ELECTRODE PROTECTIVE LAYER, AND PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

The present disclosure relates to an electrode protective layer, and a preparation method therefor and the use thereof. The electrode protective layer comprises a metal oxide and has a one-layer laminated structure, and the metal oxide is ionically conductive; and the surface of a negative electrode plate of a secondary battery is coated with the electrode protective layer. The electrode protective layer has the effects of improving the safety performance and cycle performance of a secondary battery; the preparation method is simple and has high applicability; and the electrode protective layer can be used in various batteries and various fields.

Claims

1. An electrode protective layer, comprising a metal oxide, and having a 1 to multi-layer laminated structure, and the metal oxide has ionic conductivity; wherein the metal oxide comprises at least one of a binary oxide and a ternary oxide; wherein the binary oxide has a general formula of AO.sub.m; in the AO.sub.m, A is independently selected from one of the group consisting of V, Mo, Nb, Sb, Ge, Zn, Cd, In, Co, Fe, Mn, Ni, Cu and Cr; and 1?m?3; wherein the ternary oxide is at least one of titanate, niobate, stannate, antimonate and other transition-metal ternary oxides satisfying the general formula of XY.sub.2O.sub.4; wherein the titanate is selected from at least one of the group consisting of Li.sub.4Ti.sub.5O.sub.12 and MgTi.sub.2O.sub.5; wherein the niobate is TiNb.sub.2O.sub.7; wherein the stannate is selected from at least one of the group consisting of Mg.sub.2SnO.sub.4, MgSnO.sub.3, Mn.sub.2SnO.sub.4, Co.sub.2SnO.sub.4, CoSnO.sub.3, Zn.sub.2SnO.sub.4, CaSnO.sub.3, SrSnO.sub.3 and Li.sub.2SnO.sub.3; wherein the antimonate is selected from at least one of the group consisting of CoSb.sub.2O.sub.6, NiSb.sub.2O.sub.6 and CuSb.sub.2O.sub.6.

2-3. (canceled)

4. The electrode protective layer according to claim 1, wherein the AO.sub.m is at least one of a stoichiometric oxide and a non-stoichiometric oxide.

5. The electrode protective layer according to claim 2, wherein the stoichiometric oxide is selected from at least one of the group consisting of VO, VO.sub.2, V.sub.2O.sub.5, V.sub.nO.sub.2n?1, MoO.sub.3, Nb.sub.2O.sub.5, Sb.sub.2O.sub.3, GeO.sub.2, ZnO, CdO, In.sub.2O.sub.3, CoO, Co.sub.3O.sub.4, FeO, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, MnO, Mn.sub.2O.sub.3, Mn.sub.3O.sub.4, NiO, CuO and Cr.sub.2O.sub.3; in the V.sub.nO.sub.2n?1, n is a positive integer.

6. (canceled)

7. The electrode protective layer according to claim 6, wherein the X and Y in the XY.sub.2O.sub.4 are independently selected from one of the group consisting of Mn, Fe, Co, Ni and Cu; and the condition is that the X and the Y are different.

8-11. (canceled)

12. The electrode protective layer according to claim 1, wherein the electrode protective layer has a thickness of ?0.1 nm.

13. A preparation method for the electrode protective layer according to claim 1, wherein the preparation method is an atomic layer deposition method, a chemical vapor deposition method, a physical vapor deposition method, or a combination thereof.

14. The preparation method according to claim 13, wherein the atomic layer deposition method comprises the following steps: E1. placing a negative electrode plate of a secondary battery in a chamber of an atomic layer deposition system, vacuumizing, and sequentially or simultaneously introducing isolation gas, metal precursor and oxygen-containing reactant into the chamber for atomic layer deposition; and E2. starting a moving mechanism to enable the plate to move and pass through the deposition area of the chamber for 1 to multiple times, so as to obtain the electrode protective layer.

15. The preparation method according to claim 14, wherein the metal precursor in step E1 has a flow rate of 0.1-500 SLM.

16. The preparation method according to claim 14, wherein the oxygen-containing reactant in step E1 has a flow rate of 0.1-500 SLM.

17. The preparation method according to claim 14, wherein the speed of motion in step E2 is at 0.01-300 m/min.

18. The preparation method according to claim 13, wherein the atomic layer deposition method comprises the following steps: A1. adsorbing the metal precursor on the surface of the negative electrode plate of the secondary battery in the chamber for atomic layer deposition; A2. introducing the oxygen-containing reactant into the chamber in step A1 to make the oxygen-containing reactant react with the metal precursor; and A3. repeating the steps A1 to A2, and performing cyclic deposition to form the electrode protective layer that has 1 to multi-layer laminated structure, and it is made of the metal oxide; and the metal oxide is binary oxide.

19. The preparation method according to claim 13, wherein the atomic layer deposition method comprises the following steps: B1. adsorbing a first metal precursor on the surface of the negative electrode plate of the secondary battery in the chamber for atomic layer deposition; B2. introducing the oxygen-containing reactant into the chamber in step B1 to make the oxygen-containing reactant react with the first metal precursor; B3. introducing a second metal precursor into the chamber in step B2 to make the second metal precursor adsorb on the surface of the product obtained in step B2; B4. introducing the oxygen-containing reactant into the chamber in step B3 to make the oxygen-containing reactant react with the second metal precursor; and B5. repeating the steps B1 to B4, and performing cyclic deposition to form the electrode protective layer that has 1 to multi-layer laminated structure, and it is made of the metal oxide, and the metal oxide is a ternary oxide.

20. The preparation method according to claim 13, wherein the atomic layer deposition method comprises the following steps: C1. adsorbing a first metal precursor on the surface of the negative electrode plate of the secondary battery in the chamber for atomic layer deposition; C2. introducing the oxygen-containing reactant into the chamber in step B1 to make the oxygen-containing reactant react with the first metal precursor; C3. repeating the steps C1 to C2 to obtain a first metal oxide layer; C4. introducing a second metal precursor into the chamber in step C3 to make the second metal precursor adsorb on the surface of the first metal oxide layer; C5. introducing the oxygen-containing reactant into the chamber in step C4 to make the oxygen-containing reactant react with the second metal precursor; C6. repeating the steps C4 to C5, and performing cyclic deposition to form a second metal oxide layer; and C7. cycling the steps C1 to C6, and performing cyclic deposition to form the electrode protective layer that has a multi-layer laminated structure, and it is made of the metal oxide.

21. The preparation method according to claim 13, wherein the chemical vapor deposition method is one of an atmospheric pressure chemical vapor deposition method, a low pressure chemical vapor deposition method, and a plasma enhanced chemical vapor deposition method, or a combination thereof.

22. The preparation method according to claim 21, wherein the low pressure chemical vapor deposition method comprises the following steps: F1. placing the negative electrode plate of the secondary battery in a chamber of a low-pressure hot-wall chemical vapor deposition system, vacuumizing and cleaning; and F2. introducing the metal precursor and the oxygen-containing reactant into the chamber in step F1, and reacting to obtain the electrode protective layer.

23. The preparation method according to claim 13, wherein the physical vapor deposition method is one of evaporation, magnetron sputtering, and pulse laser deposition method.

24. The preparation method according to claim 23, wherein the magnetron sputtering method comprises the following steps: G1. placing the negative electrode plate of the secondary battery into a magnetron sputtering system, and vaccumizing; G2. sputtering a transition layer on the surface of the negative electrode plate of the secondary battery in a protective gas atmosphere; and G3. sputtering the electrode protective layer on the surface of the transition layer.

25. A negative electrode, comprising the electrode protective layer according to claim 1, an active material, a binder, a conductive agent, and a current collector.

26. A negative electrode according to claim 25, wherein the active material comprises at least one of graphite, graphene, carbon nanotubes, vapor grown carbon fibers, silicon carbon, silicon, lithium metal, sodium metal, and transition metal oxides.

27. A secondary battery, comprising the negative electrode according to claim 25.

28. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0157] The following is a further explanation of the present disclosure in conjunction with the accompanying drawings and embodiments, wherein:

[0158] FIG. 1 is a schematic structural diagram of the commercial graphite negative electrode plate used in Example 1 according to the present disclosure;

[0159] FIG. 2 is a discharge specific capacity diagram of the lithium batteries consisting of the raw material of commercial graphite negative electrode plate used in the examples, and the negative electrode plates prepared in Example 3 and Comparative Example 1;

[0160] FIG. 3 is a discharge specific capacity diagram of the lithium batteries consisting of the raw material of commercial graphite negative electrode plate used in the examples, and the negative electrode plates prepared in Examples 2, 4-6 and 9 and Comparative Example 1;

[0161] FIG. 4 is a charge and discharge curves of the lithium batteries consisting of the raw material of commercial graphite negative electrode plate used in the examples, and the negative electrode plates prepared in Examples 2 and 4-5 at 50 cycles, 100 cycles and 150 cycles;

[0162] FIG. 5 is a rate performance diagram of the lithium batteries consisting of the raw material of commercial graphite negative electrode plate used in the examples and the negative electrode plates prepared in Examples 2 and 4-5.

REFERENCE NUMBERS

[0163] 100: current collector; [0164] 200: negative electrode coating layer; 210: active material; 220: binder.

DETAILED DESCRIPTION

[0165] The concept of the present disclosure and the resulting technical effects will be clearly and completely described below in conjunction with examples, so that the aims, features, and effects of the present disclosure can be fully understood. It is clear that the described examples are merely some rather than all of examples of the present disclosure. All other examples obtained by those skilled in the art based on examples of the present disclosure without creative labor shall fall within the protection scope of the present disclosure.

[0166] In the description of the present disclosure, the description with reference to the terms one embodiment, some embodiments, exemplary embodiment, example, specific example, some examples etc. refers to the particular features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the exemplary expression of above terms does not necessarily refer to the same embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples.

[0167] Unless otherwise specified, the commercial graphite negative electrode plate used in the embodiments of the present disclosure comprises a current collector 100 and a negative electrode coating 200 coated thereon. It comprises an active material graphite 210 and a binder 220 in negative electrode coating layer 200, which is purchased from Canrd, wherein the plate number is SM0201, the active material ratio is 95.7%, the material gram capacity: 330 mAh/g (0.005-2.0 V), the current collector has a thickness of 8 ?m, and the coating surface density is about 5.8 mg/cm.sup.2 (at different positions, the surface density after compaction may fluctuate within a certain range). The commercial graphite negative electrode plate does not be rolled. Specific examples of the present disclosure are described in detail below.

Example 1

[0168] This example prepares an electrode protective layer with a material of Co.sub.xO (x=0.75-1), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0169] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the chamber; [0170] H2. a metal precursor bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was pulsed into a reaction chamber at 150? C. The valve opening and closing time: 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s. The total number of pulse in this step was 1; [0171] H3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was adsorbed on the surface of the commercial graphite negative electrode; [0172] H4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, and numbers of valve opening and closing was 5, allowing ozone to fully react with bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt in step H3; [0173] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 60 s; [0174] H6. steps H2-H5 were cycled for 40 times to obtain the electrode protective layer with a thickness of 1.6 nm.

[0175] The Co.sub.xO obtained in this example represents a non-stoichiometric cobalt oxide, and since the valence of element such as Co etc can not be controlled in ALD chemical reaction process, non-stoichiometric oxides are often obtained. However, ALD tends to produce low valence compounds, x is thus between 0.75-1, and x fluctuates within the above range without affecting the performance of the resulting negative electrode plate.

[0176] By proportionally adjusting the cycle number in step H6, this example also obtained electrode protective layers made of Co.sub.xO (x=0.75-1) with thicknesses of 1 nm, 5 nm and 10 nm, respectively.

Example 2

[0177] This example prepares an electrode protective layer with a material of Fe.sub.xO (x=0.67-1), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0178] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0179] H2. a metal precursor ferrocene was placed into a reaction chamber at 200? C. The valve opening and closing time: 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s. The total number of pulse in this step was 1; [0180] H3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 60 s, wherein the ferrocene was adsorbed on the surface of the commercial graphite negative electrode; [0181] H4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, and numbers of valve opening and closing were 5 times, allowing ozone to fully react with ferrocene in step H3; [0182] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 120 s; H6. steps H2-H5 were cycled for 30 times.

[0183] Fe.sub.xO obtained in this example represents non-stoichiometric iron oxide, the reason of formation refers to Example 1, and x fluctuates between 0.67 and 1 without affecting the performance of the obtained negative electrode plate.

Example 3

[0184] This example prepares an electrode protective layer with a material of Co.sub.xSnO.sub.2+x (0<x<2), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0185] I1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0186] I2. a metal precursor tetrakis(diethylamine)tin was pulsed into a reaction chamber at 150? C. The time of valve opening and closing: 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s. The total number of pulse in this step was 1; [0187] I3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the tetrakis(diethylamine)tin was adsorbed on the surface of the commercial graphite negative electrode; [0188] I4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 20 s, and numbers of valve opening and closing were 5 times, allowing ozone to fully react with tetrakis(diethylamine)tin; [0189] I5. 2000 sccm of N.sub.2 was introduced into the chamber in step I4 and purged for 90 s; [0190] I6. a metal precursor bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was pulsed into the reaction chamber at 150? C. The valve opening and closing time was 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse was 1 time; [0191] I7. 2000 sccm of N.sub.2 was introduced into the chamber in step I6 and purged for 30 s; [0192] 18. the reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, and numbers of valve opening and closing were 5 times, allowing ozone to fully react with bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt in step I6, and the reaction product obtained in this step was fully diffused with the reaction product obtained in step I4; [0193] I9. 2000 sccm of N.sub.2 was introduced into the chamber in step I8 and purged for 60 s; [0194] I10. steps I2-I9 were cycled for 20 times to obtain the electrode protective layer with a thickness of 3.2 nm.

[0195] The Co.sub.xSnO.sub.2+x obtained in this example represents non-stoichiometric cobalt stannate, the reason of formation refers to Example 1, and x fluctuates between 0 and 2 without affecting the performance of the obtained negative electrode plate.

[0196] By controlling the cycle times in step I10 in an equal proportion, the electrode protective layers made of Co.sub.xSnO.sub.2+x (0<x<2) with thicknesses of 1 nm, 5 nm and 10 nm are respectively prepared and obtained in this example.

Example 4

[0197] This example prepares an electrode protective layer with a material of CuMn.sub.xO.sub.2 (x=0.67-1), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is an atomic layer deposition method, which comprises the specific steps of: [0198] I1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0199] I2. a metal precursor copper acetylacetonate was pulsed into a reaction chamber at 200? C. The valve opening and closing time: 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s. The total number of pulses in this step was 1; [0200] I3. 2000 of sccm N.sub.2 was introduced into the chamber in step I2, and purged for 30 s, wherein copper acetylacetonate was adsorbed on the surface of the commercial graphite negative electrode; [0201] I4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, and the numbers of valve opening and closing were 5 times, and allowing ozone to fully react with copper acetylacetonate in step I3; [0202] I5. 2000 sccm of N.sub.2 was introduced into the chamber in step I4 and purged for 90 s; [0203] I6. a metal precursor tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese was pulsed into the reaction chamber at 150? C. The time of valve opening and closing was 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s. The total number of pulse in this step was 1; [0204] I7. 2000 sccm of N.sub.2 was introduced into the chamber in step I6, and purged for 30 s, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese was adsorbed on the surface of the product obtained in step I5; [0205] I8. the reactant ozone (O.sub.3) were introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing ozone to fully react with tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese in step I7, for 5 times, and the product obtained in this step was fully diffused with the reaction product obtained in step I4; [0206] I9. 2000 sccm of N.sub.2 was introduced into the chamber in step I8 and purged for 60 s; [0207] I10. steps I2-I9 were cycled for 20 times to obtain the electrode protective layer with a thickness of 2 nm.

[0208] The CuMn.sub.xO.sub.2 obtained in this example represents non-stoichiometric copper manganate, the reason of formation refers to Example 1, and x fluctuates between 0.67 and 1, without affecting the performance of the obtained negative electrode plate.

[0209] By controlling the cycle number of step I10 in an equal proportion, this example also obtained electrode protective layers with thicknesses of 1 nm, 5 nm and 10 nm, respectively.

Example 5

[0210] This example prepares an electrode protective layer with a material of Co.sub.xO (x=0.75-1)/Fe.sub.yO (y=0.67-1) and having a nano-laminated structure, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0211] J1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0212] J2. a first metal precursor bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was pulsed into a reaction chamber at 150? C. The time of valve opening and closing: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s. The total number of pulse was 1; [0213] J3. 2000 of sccm N.sub.2 was introduced into the chamber in step J2, and purged for 30 s, wherein a layer of bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was adsorbed on the surface of the commercial graphite negative electrode; [0214] J4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0215] J5. 2000 sccm of N.sub.2 was introduced into the chamber in step J4 and purged for 60 s; [0216] J6. steps J2-J5 were cycled for 5 times to obtain a Co.sub.xO layer; [0217] J7. a second metal oxide ferrocene was pulsed into the reaction chamber at 200? C., wherein the time of valve opening and closing was 1 s, after the pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse was 1; [0218] J8. 2000 sccm of N.sub.2 was introduced into the chamber in step J7 and purged for 60 s; [0219] J9. an oxygen-containing reactant and ozone (O.sub.3) were introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0220] J10. 2000 sccm of N.sub.2 was introduced and purged for 120 s; [0221] J11. steps J7-J10 were cycled for 3 times to obtain a Fe.sub.xO layer; [0222] J12. steps J2-J10 were cycled for 5 times to obtain an electrode protective layer with a laminated structure in which the Co.sub.xO layer and Fe.sub.xO layer were alternately formed.

[0223] Co.sub.xO (x=0.75-1)/Fe.sub.yO (y=0.67-1) prepared in this example represents a laminated structure formed by laminating non-stoichiometric cobalt oxide and iron oxide, and the formation reason of formation refers to Example 1, and x and y fluctuate within the above range without affecting the performance of the obtained negative electrode plate.

Example 6

[0224] This example prepares an electrode protective layer with a material of CuO, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is low-pressure hot-wall chemical vapor deposition, which comprises the specific steps of: [0225] L1. a commercial graphite negative electrode plate was placed into a chamber of low-pressure hot-wall chemical vapor deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then introducing N.sub.2 (2500 sccm) was introduced to clean the chamber for 15 min; [0226] L2. 50 sccm of copper acetylacetonate and 100 sccm of oxygen were introduced into the reaction chamber at 200? C., wherein the carrier gas was 2500 sccm of N.sub.2, the pressure in the reaction chamber was maintained at 0.04 Torr, the reaction time was 30 min, and a CuO film was deposited on the surface of the negative electrode plate.

Example 7

[0227] This example prepares an electrode protective layer with a material of Co.sub.2SnO.sub.4, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is magnetron sputtering method, which comprises the specific steps of: [0228] M1. the commercial graphite negative electrode plate was transferred into a magnetron sputtering system, and the air pressure of chamber in system was reduced to 0.002 Torr by using a mechanical pump and a molecular pump; [0229] M2. 80 sccm of Ar was introduced, and the air pressure in the system chamber was raised to 0.01 Torr. a pure titanium target material was sputtered by using a 150 W direct current power supply. The bias voltage was applied to the substrate at ?50V, and rotated at 30 rad/min for 3 min, and a titanium transition layer was deposited on the surface of the negative electrode plate; [0230] M3. a pure Co.sub.2SnO.sub.4 target material was sputtered by using a 300 W radio frequency power supply. The bias voltage was applied to the substrate at ?50V, and rotated at 30 rad/min. The sputtering time was 30 min, and a coating layer Co.sub.2SnO.sub.4 was deposited.

Example 8

[0231] This example prepares an electrode protective layer with a material of Fe.sub.xO (x=0.67-1), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is roll-to-roll atomic layer deposition method, which comprises the specific steps of: [0232] P1. a negative electrode plate coil stock with a width of 1000 mm and a length of 1000 m was placed in the chamber of an atomic layer deposition system, vacuumizing the system to 0.05 Torr. The inert isolation gas with a flow rate of 400 SLM, the iron source precursor gas used for Fe.sub.xO (x=0.67-1) electrode protective layer with a flow rate of 200 SLM and 500 mg/L ozone gas used for electrode protective layer material with a flow rate of 200 SLM were sequentially or simultaneously introduced into the atomic layer deposition chamber; [0233] P2. The moving mechanism was started to enable the electrode plate to be deposited to pass through the inner cavity deposition area of five cycles in two directions at the speed of 50 m/min for four times; [0234] P3. when all the negative electrode plates had moved forward, the flushing gas, the iron source precursor gas and ozone gas were turned off. The heating was turned off, and air was filled back. A winding device was opened to move the graphite negative electrode plate after completing the deposition processing.

Example 9

[0235] This example prepares an electrode protective layer with a material of In.sub.2O.sub.3, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0236] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0237] H2. a metal precursor trimethylindium was pulsed into a reaction chamber at 150? C., wherein the time of valve opening and closing: 0.5 s, after the reaction chamber pressure reached 10 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step was 1; [0238] H3. 2000 sccm of N.sub.2 was introduced into the chamber of the step H2, and purged for 30 s, wherein the trimethylindium was adsorbed on the surface of the commercial graphite negative electrode; [0239] H4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 1 Torr, time of maintaining: 1 s, and numbers of valve opening and closing were 5 times, allowing H.sub.2O to fully react with trimethylindium in step H3; [0240] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0241] H6. steps H2-H5 were cycled for 25 times to obtain the electrode protective layer with a thickness of 1 nm.

[0242] By controlling the cycle number of step H6 in an equal proportion, this example also prepared and obtained electrode protective layers with thicknesses of 5 nm and 10 nm, respectively.

Example 10

[0243] This example prepares an electrode protective layer with a material of Mn.sub.xO, and this electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0244] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0245] H2. a metal precursor tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese was pulsed into a reaction chamber at 150? C. The time of valve opening and closing was 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse in this step was 1; [0246] H3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese was adsorbed on the surface of the commercial graphite negative electrode; [0247] H4. the reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing ozone to fully react with tris(2,2,6,6-tetramethyl-3,5-heptanedione)manganese in step H3, for 5 times; [0248] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0249] H6. steps H2-H5 were cycled for 20 times.

Example 11

[0250] This example prepares an electrode protective layer with a material of NiO, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0251] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0252] H2. a metal precursor bis(dimethylamino-2-propoxy)nickel was pulsed into the reaction chamber at 150? C. The valve opening and closing time was 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse in this step was 1; [0253] H3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the bis(dimethylamino-2-propoxy)nickel was adsorbed on the surface of the commercial graphite negative electrode; [0254] H4. the reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing ozone to fully react with bis(dimethylamino-2-propoxy)nickel in step H3, for 5 times; [0255] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0256] H6. steps H2-H5 were cycled for 20 times.

Example 12

[0257] This example prepares an electrode protective layer with a material of CuO, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0258] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0259] H2. a second metal precursor copper acetylacetonate was pulsed into the reaction chamber at 150? C. The time of valve opening and closing: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse in this step is 1; [0260] H3. 2000 of sccm N.sub.2 was introduced into the chamber in step H2, and pulsed for 30 s, wherein copper acetylacetonate was adsorbed on the surface of the commercial graphite negative electrode; [0261] H4. the reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing ozone to fully react with copper acetylacetonate in step H3, for 5 times; [0262] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0263] H6. steps H2-H5 were cycled for 25 times.

Example 13

[0264] This example prepares an electrode protective layer with a material of ZnO, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0265] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0266] H2. a metal precursor diethyl zinc was pulsed into a reaction chamber at 150? C. The time of valve opening and closing: 0.5 s, after the reaction chamber pressure reached 1 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step is 1; [0267] H3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the diethyl zinc was adsorbed on the surface of the commercial graphite negative electrode; [0268] H4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 1 Torr, time of maintaining: 1 s, number of valve opening and closing was 1 time, allowing H.sub.2O to fully react with diethyl zinc in step H3; [0269] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0270] H6. steps H2-H5 were cycled for 15 times.

Example 14

[0271] This example prepares an electrode protective layer with a material of Nb.sub.2O.sub.5, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0272] H1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0273] H2. a metal precursor niobium pentaethoxide was pulsed into a reaction chamber at 150? C. The time of valve opening and closing: 2 s, after the reaction chamber pressure reached 1 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step is 1; [0274] H3. 2000 sccm of N.sub.2 was introduced into the chamber of the step H2, and purged for 30 s, wherein the niobium pentaethoxide was adsorbed on the surface of the commercial graphite negative electrode; [0275] H4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 1 Torr, time of maintaining: 5 s, number of valve opening and closing was 1 time, allowing H.sub.2O to fully react with niobium pentaethoxide in step H3; [0276] H5. 2000 sccm of N.sub.2 was introduced into the chamber in step H4 and purged for 20 s; [0277] H6. steps H2-H5 were cycled for 30 times.

Example 15

[0278] This example prepares an electrode protective layer with a material of Co.sub.xO (x=0.75-1), and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is roll-to-roll atomic layer deposition method, which comprises the specific steps of: [0279] P1. a negative electrode plate coil stock with a width of 1000 mm and a length of 1000 m was placed in a chamber of an atomic layer deposition system, vacuumizing the system to 0.05 Torr. The inert isolation gas with a flow rate of 400 SLM, mixed gas of bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt source precursor and nitrogen carrier gas used by a Co.sub.xO (x=0.75-1) electrode protective layer with a flow rate of 200 SLM, and 500 mg/L ozone gas used by an electrode protective layer material with a flow rate of 200 SLM were sequentially or simultaneously introduced into the atomic layer deposition chamber; [0280] P2. The moving mechanism was started to enable the electrode plate to be deposited to pass through the inner cavity deposition area of five cycles in two directions at the speed of 10 m/min for four times; [0281] P3. when all the negative electrode plates had moved forward, the flushing gas, the cobalt source precursor gas and ozone gas were turned off. The heating was turned off, and air was filled back. A winding device was opened to move the graphite negative electrode plate after completing the deposition processing.

Example 16

[0282] This example prepares an electrode protective layer with a material of In.sub.2O.sub.3, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is roll-to-roll atomic layer deposition method, which comprises the specific steps of: [0283] P1. a negative electrode plate coil stock with a width of 1000 mm and a length of 1000 m was placed in a chamber of an atomic layer deposition system, vacuumizing the system to 0.05 Torr. The inert isolation gas with a flow rate of 400 SLM, the mixed gas of indium source precursor and nitrogen carrier gas used by a In.sub.2O.sub.3 electrode protective layer with a flow rate of 200 SLM, and the mixed gas of water vapor and nitrogen carrier gas used by an electrode protective layer material with a flow rate of 200 SLM were sequentially or simultaneously introduced into the atomic layer deposition chamber; [0284] P2. The moving mechanism was started to enable the electrode plate to be deposited to pass through the inner cavity deposition area of five cycles in two directions at the speed of 10 m/min for four times; [0285] P3. when all the negative electrode plates had moved forward, the flushing gas, the indium source precursor gas and ozone gas were turned off. The heating was turned off, and air was filled back. A winding device was opened to move the graphite negative electrode plate after completing the deposition processing.

Example 17

[0286] This example prepares an electrode protective layer with a material of Li.sub.4Ti.sub.5O.sub.12, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0287] I1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0288] I2. a metal precursor tert-butyl lithium was pulsed into a reaction chamber at 200? C. The time of valve opening and closing: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step is 1; [0289] I3. 2000 sccm of N.sub.2 was introduced into the chamber of step H2, and purged for 30 s, wherein the tert-butyl lithium was adsorbed on the surface of the commercial graphite negative electrode; [0290] I4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, for 5 times, allowing water to fully react with tert-butyl lithium in step I3; [0291] I5. 2000 sccm of N.sub.2 was introduced into the chamber in step I4 and purged for 90 s; [0292] I6. a metal precursor titanium tetraisopropoxide was pulsed into a reaction chamber at 150? C. The time of valve opening and closing: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s. The total number of pulse in this step was 1; [0293] I7. 2000 sccm of N.sub.2 was introduced into the chamber in step I6, and purged for 30 s, wherein the titanium tetraisopropoxide was adsorbed on the surface of the product obtained in step I5; [0294] I8. the reactant water (H.sub.2O) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing water to fully react with titanium tetraisopropoxide in step I7, for 5 times, and the product obtained in this step was fully diffused with the reaction product obtained in step I4; [0295] I9. 2000 sccm of N.sub.2 was introduced into the chamber in step I8 and purged for 60 s; [0296] I10. steps I2-I9 were cycled for 20 times.

Example 18

[0297] This example prepares an electrode protective layer with a material of TiNb.sub.2O.sub.7, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0298] I1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0299] I2. a metal precursor titanium tetraisopropoxide was placed into a reaction chamber at 200? C. The valve opening and closing time: 1 s. After the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step was 1; [0300] I3. 2000 of sccm N.sub.2 was introduced into the chamber in step I2, and purged for 30 s, wherein titanium tetraisopropoxide was adsorbed on the surface of the commercial graphite negative electrode; [0301] I4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, number of valve opening and closing was 5 times, allowing water to fully reacted with the titanium tetraisopropoxide in step I3; [0302] I5. 2000 sccm of N.sub.2 was introduced into the chamber in step I4 and purged for 90 s; [0303] I6. a metal precursor niobium pentaethoxide was pulsed into the reaction chamber at 150? C. The valve opening and closing time: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse was 1 time; [0304] I7. 2000 sccm of N.sub.2 was introduced into the chamber in step I6, and purged for 30 s, wherein the niobium pentaethoxide was adsorbed on the surface of the product obtained in step I5; [0305] I8. the reactant water (H.sub.2O) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing water to fully react with niobium pentaethoxide in step I7, for 5 times, and the product obtained in this step was fully diffused with the reaction product obtained in step I4; [0306] I9. 2000 sccm of N.sub.2 was introduced into the chamber in step I8 and purged for 60 s; [0307] I10. steps I2-I9 were cycled for 20 times.

Example 19

[0308] This example prepares an electrode protective layer with a material of CoSb.sub.2O.sub.6, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0309] I1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0310] I2. a metal precursor bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was pulsed into a reaction chamber at 200? C. The valve opening and closing time: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse in this step was 1; [0311] I3. 2000 sccm of N.sub.2 was introduced into the chamber of step I2, and purged for 30 s, wherein the bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was adsorbed on the surface of the commercial graphite negative electrode; [0312] I4. an oxygen-containing reactant and water (H.sub.2O) were introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, time of maintaining: 15 s, number of valve opening and closing was 5 times, allowing water to fully react with bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt in step I3; [0313] I5. 2000 sccm of N.sub.2 was introduced into the chamber in step I4 and purged for 90 s; [0314] I6. a metal precursor antimony pentachloride was pulsed into the reaction chamber at 150? C. The valve opening and closing time: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse was 1 time; [0315] I7. 2000 sccm of N.sub.2 was introduced into the chamber in step I6, and purged for 30 s, wherein the niobium pentaethoxide was adsorbed on the surface of the product obtained in step I5; [0316] I8. the reactant water (H.sub.2O) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 10 s, allowing water to fully react with antimony pentachloride in step I7, for 5 times, and the product obtained in this step was fully diffused with the reaction product obtained in step I4; [0317] I9. 2000 sccm of N.sub.2 was introduced into the chamber in step I8 and purged for 60 s; [0318] I10. steps I2-I9 were cycled for 20 times.

Example 20

[0319] This example prepares an electrode protective layer with a material of Co.sub.xO/In.sub.2O.sub.3 (x=0.75-1) and having a nano-laminated structure, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0320] J1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0321] J2. a first metal precursor bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was pulsed into a reaction chamber at 150? C. The valve opening and closing time: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse is in this step was 1 time; [0322] J3. 2000 of sccm N.sub.2 was introduced into the chamber in step J2, and purged for 30 s, wherein a layer of bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt was adsorbed on the surface of the commercial graphite negative electrode; [0323] J4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0324] J5. 2000 sccm of N.sub.2 was introduced into the chamber in step J4 and purged for 60 s; [0325] J6. steps J2-J5 were cycled for 5 times to obtain a Co.sub.xO layer; [0326] J7. a second metal oxide source trimethylindium was pulsed into the reaction chamber at 150? C. The valve opening and closing time: 1 s, after the pressure reached 15 Torr, the pressure was maintaining for 10 s, and the total number of pulse was 1; [0327] J8. 2000 sccm of N.sub.2 was introduced into the chamber in step J7 and purged for 60 s; [0328] J9. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0329] J10. 2000 sccm of N.sub.2 was introduced and purged for 120 s; [0330] J11. steps J7-J10 were cycled for 3 times to obtain the In.sub.2O.sub.3 layer; [0331] J12. steps J2-J10 were cycled for 5 times to obtain an electrode protective layer with a laminated structure in which the Co.sub.xO layer and In.sub.2O.sub.3 layer are alternately formed.

[0332] Co.sub.xO/In.sub.2O.sub.3 (x=0.75-1) prepared in this example represents a laminated structure formed by laminating non-stoichiometric cobalt oxide and iron oxide, and the reason of formation refers to Example 1, and x fluctuates within the above range without affecting the performance of the obtained negative electrode plate.

Example 21

[0333] This example prepares an electrode protective layer with a material of In.sub.2O.sub.3/ZnO and having a nano-laminated structure, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0334] J1. a commercial graphite negative electrode plate was palced into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0335] J2. a first metal precursor trimethylindium was pulsed into the reaction chamber at 150? C. The valve opening and closing time: 1 s, after the reaction chamber pressure reached 15 Torr, the pressure was maintained for 5 s, and the total number of pulse was 1; [0336] J3. 2000 sccm of N.sub.2 was introduced into the chamber of step J2, and purged for 30 s, wherein the a trimethylindium layer was adsorbed on the surface of the commercial graphite negative electrode; [0337] J4. an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0338] J5. 2000 sccm of N.sub.2 was introduced into the chamber in step J4 and purged for 60 s; [0339] J6. steps J2-J5 were cycled for 5 times to obtain a In.sub.2O.sub.3 layer; [0340] J7. a second metal oxide source diethyl zinc was pulsed into the reaction chamber at 150? C. The valve opening and closing time was 1 s, after the pressure reached 15 Torr, the pressure was maintained for 10 s, and the total number of pulse was 1; [0341] J8. 2000 sccm of N.sub.2 into the chamber in the step J7 for purging for 60 s; [0342] J9. introducing an oxygen-containing reactant ozone (O.sub.3) was introduced into the reaction chamber, when the pressure of the chamber reached 5 Torr, maintaining for 15 s, for 5 times; [0343] J10. 2000 sccm of N.sub.2 was introduced and purged for 120 s; [0344] J11. steps J7-J10 were cycled for 3 times to obtain the ZnO layer; [0345] J12. steps J2-J10 were cycled for 5 times to obtain an electrode protective layer with a laminated structure in which the In.sub.2O.sub.3 layer and ZnO layer are alternately formed.

[0346] The In.sub.2O.sub.3/ZnO prepared in this example is a laminated structure formed by laminating non-stoichiometric indium oxide and zinc oxide, and the reason of formation refers to Example 1.

Example 22

[0347] This example prepares an electrode protective layer with a material of Co.sub.xSnO.sub.2+x, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is low-pressure hot-wall chemical vapor deposition, which comprises the specific steps of: [0348] L1. a commercial graphite negative electrode plate was placed into a chamber of a low-pressure hot-wall chemical vapor deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then N.sub.2 (2500 sccm) was introduced to clean the chamber for 15 min; [0349] L2. 50 sccm of a metal precursor tetrakis(diethylamine)tin, 50 sccm of bis(2,2,6,6,-tetramethyl-3,5-heptanedioate)cobalt, and 100 sccm of oxygen were introduced into the reaction chamber at 150? C. The carrier gas was 2500 sccm of N.sub.2, the pressure in the reaction chamber was maintained at 0.04 Torr, the reaction time was 30 min, and the Co.sub.xSnO.sub.2+x was deposited on the surface of the negative electrode plate.

Example 23

[0350] This example prepares an electrode protective layer with a material of CuO, and this electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is magnetron sputtering method, which comprises the specific steps of: [0351] M1. the commercial graphite negative electrode plate was transferred into a magnetron sputtering system, and the air pressure of chamber in system was reduced to 0.002 Torr by using a mechanical pump and a molecular pump; [0352] M2. 80 sccm of Ar was introduced, and the air pressure in the system chamber was raised to 0.01 Torr; a CuO target material material was sputtered by using a 150 W alternating current power supply. The bias voltage was applied to the substrate at ?50V, and rotated at 20 rad/min for 3 min, and a CuO coating layer was deposited on the surface of the negative electrode plate.

Comparative Example 1

[0353] This comparative example prepares an electrode protective layer with a material of Al.sub.2O.sub.3, and above electrode protective layer is attached to a commercial graphite negative electrode plate, and the preparation method is atomic layer deposition method, which comprises the specific steps of: [0354] A1. a commercial graphite negative electrode plate was placed into a chamber of an atomic layer deposition system, vacuumizing by using a mechanical pump to reduce the air pressure of the chamber to 0.01 Torr, then introducing a small amount of N.sub.2 (100 sccm) was introduced to keep the fluidity of inert gas inside the cavity; [0355] A2. a precursor trimethylaluminum was pulsed into a reaction chamber at 150? C. The valve opening and closing time: 0.5 s, the ALD reaction chamber pressure reached 2 Torr, the time of pressure maintaining for precursor was 1 s, for 1 time; [0356] A3. 2000 sccm of N.sub.2 was introduced and purged for 15 s; [0357] A4. the reactant ozone (O.sub.3) was introduced into the reaction chamber, wherein the pressure of the ALD reaction chamber reached 5 Torr, time of maintaining: 15 s, for 2 times; [0358] A5. 2000 sccm of N.sub.2 was introduced and purged for 30 s; [0359] A6. the steps A2-A5 were cycled for 10 times to obtain the electrode protective layer with a thickness of 3.2 nm.

[0360] By adjusting the cycle number of step A6 in an equal proportion, this comparative example also prepared and obtained electrode protective layers with thicknesses of 1 nm, 5 nm and 10 nm, respectively.

Test Example

[0361] This test example tests the performance of the negative electrode plates. The specific test method is as follows.

[0362] (1) Assembling of a graphite electrode plate-lithium plate half-cell. A wave elastic sheet of the button-cell shell made of 316 stainless steel (Canrd, 15.4 mm?1.0 mm), a gasket of the button-cell shell made of 316 stainless steel (Canrd, 15.5 mm?0.5 mm), a metal lithium plate, a separator (Celgard, a thickness of 25 ?m, made of polypropylene) and a graphite negative electrode (Canrd SM0201) that was or was not processed by the passivation layer were sequentially placed in the button-cell shell made of 316 stainless steel (Canrd). Wherein several drops of electrolyte (graphite button battery electrolyte, Canrd KLD-1230C) were dripped into the surface of the lithium plate and separator before and after the separator was Installed. Finally, the installed battery above was compacted by using a hydraulic tablet press to complete the assembly of the half-cell buckling.

[0363] (2) Cycle test of the half-cell. The half-cell was installed on a LANHE cell test system and placed at a test environment of 25(?1? C.) for testing. In the first 2 cycles, the battery was activated by charge and discharge at a constant current of 0.1 C. In subsequent cycles, charge and discharge was performed at a constant current of 0.2 C, and the test voltage was 0-2.0V.

[0364] (3) Rate performance test of the half cell. The test voltage was 0-2.0V, after activating and cycling for 2 cycles by the same method as the cycle test, the discharge capacities of the battery at 0.1 C/0.1 C, 0.2 C/0.2 C, 0.5 C/0.5 C, 1 C/1 C and 2 C/2 C were sequentially tested, each rate test was performed for 6 cycles, and after the above rate tests were finished, the recovery condition of the battery performance was observed by cycling for 6 cycles at 0.1 C/0.1 C.

[0365] The discharge specific capacity graph of the electrochemical performance of the commercial graphite negative electrode plate used in Example 3 and the negative electrode plates prepared in Example 3 and Comparative Example 1 is shown in FIG. 2.

[0366] It can be seen from FIG. 2 that the specific capacity of the negative electrode plate formed by the Co.sub.xSnO.sub.2+x electrode protective layer (with a thickness of 3.2 nm) prepared by the atomic layer deposition method in Example 3 has a slow decrease trend and can be maintained above 300 mAh/g; compared with the untreated commercial graphite negative electrode plate, the specific capacity of the negative electrode plate is greatly decreased after 60 cycles, and is decreased to below 150 mAh/g after 100 charge and discharge cycles. Therefore, It can be seen that the cycle life of the negative electrode plate coated by the electrode protective layer is greatly prolonged. In addition, the commercial plate coated with Al.sub.2O.sub.3 (with a thickness of 3.2 nm) prepared by atomic layer deposition in the first 30 cycles shows similar cycle performance to the Co.sub.xSnO.sub.2+x coated plate; and with a subsequent slow decrease in capacity, the overall performance of the commercial plate is weaker than that of Co.sub.xSnO.sub.2+x coated plate but better than that of uncoated plate. The reason is that the thickness of Al.sub.2O.sub.3 coating is thinner and the ionic conductivity is poor.

[0367] The cycle performances of the commercial graphite negative electrode plate used in Example 1, the negative electrode plate in Comparative Example 1 (coated with Al.sub.2O.sub.3), the negative electrode plate used Example 2 (deposited Fe.sub.xO by static atomic layer deposition), the negative electrode plate in Example 8 (deposited Fe.sub.xO by roll-to-roll deposition), the negative electrode plate in Example 4 (coated with CuMn.sub.xO.sub.2), and the negative electrode plate in Example 5 (coated with Co.sub.xO/Fe.sub.yO) are shown in FIG. 3 (the thicknesses of all the electrode protective layers are 5 nm), and the results in FIG. 3 show that the electrode protective layers with any of static atomic layer deposition, the dynamic atomic layer deposition and different materials can achieve similar secondary battery negative electrode protection effects, and are significantly better than the performances of the untreated commercial graphite negative electrode plate and the commercial graphite negative electrode plate that is treated with Al.sub.2O.sub.3.

[0368] The charge and discharge curves of the lithium batteries consisting of the commercial graphite negative electrode plate raw material of examples, and negative electrode plates in Example 2 and 4-5 at 150 cycles are shown in FIG. 4 (the thickness of the electrode protective layer is 5 nm).

[0369] FIG. 4 shows that comparing with the negative electrode plate without the electrode protective layer, the performance of the negative electrode plates of Example 2 (Fe.sub.xO), Example 4 (CuMn.sub.xO.sub.2) and Example 5 (Co.sub.xOFe.sub.yO) of the present disclosure is significantly better.

[0370] The rate performance diagram of the lithium batteries consisting of commercial graphite negative electrode plate raw material of examples, and the negative electrode plates in Examples 2 and 4-5 is shown in FIG. 5 (the thickness of the electrode protective layer is 5 nm).

[0371] FIG. 5 shows that whether or not the electrode protective layer is set has a little effect on the charge and discharge performance of the lithium-ion batteries at low rate (0.1 C). However, at rates of 0.2 C, 0.5 C and IC, the protective performance of the electrode protective layer is reflected, which significantly improving the rate performance of the resulting battery. 0.2 C-1 C is a common used rate for lithium-ion battery. Therefore, the electrode protective layer provided by the present disclosure has broad application prospects in various types of lithium-ion batteries. If the rate continues to be increased, the impedance brought by the electrode protective layer is larger, so it may have a certain impact on high rate.

[0372] This test example also compiled the electrochemical performance results of the negative electrode plates obtained in examples and comparative example, as well as the corresponding results of between above performance and the material and thickness of the electrode protective layer, as shown in Tables 1-3.

[0373] In Tables 1-3, the thickness of the electrode protective layer is calibrated according to the metal content in the electrode protective layer, specifically, the metal content in the electrode protective layer deposited on the negative electrode plate has a linear relationship with the thickness of the film deposited on the silicon dummy wafer (when the electrode protective layer is deposited, the silicon dummy wafer is deposited at the same time and under the same conditions), and the film thickness of the silicon dummy wafer can be accurately measured by ellipsometer, so as to calibrate the electrode plate content.

TABLE-US-00001 TABLE 1 Electrochemical performance of the negative electrode plate with the single-layer binary oxide as the electrode protective layer First-cycle discharging Capacity retention Thick- specific rate % ness capacity 50 100 150 Material (nm) (mAh/g) cycles cycles cycles 373 97 63.5 44.7 Exam- Co.sub.xO 10 365 99 98.1 94.9 ple 1 Co.sub.xO 5 364 98 97.7 94.5 Co.sub.xO 1 366 99 98.6 95 Exam- In.sub.2O.sub.3 10 368 98.5 98.2 94.6 ple 9 In.sub.2O.sub.3 5 370 98.2 98 94.1 In.sub.2O.sub.3 1 371 99 98.5 92.1 Exam- Fe.sub.xO 5 369 99.5 99.2 92.3 ple 2 Exam- Mn.sub.xO 5 370 98.6 98.3 92 ple 10 Exam- NiO 5 374 99 98.5 91.5 ple 11 Exam- CuO 5 372 98.6 98.2 94.8 ple 12 Exam- ZnO 5 374 98.7 98.3 95 ple 13 Exam- Nb.sub.2O.sub.5 5 375 99 98.6 94.9 ple 14 Exam- Co.sub.xO 5 373 98.8 98.5 94.6 ple 15 dynamic device Exam- In.sub.2O.sub.3 5 371 98.9 98.4 94.8 ple 16 dynamic device

[0374] The results in Table 1 show that the cycle performance of the negative electrode plate deposited with the electrode protective layer is significantly improved, the capacity retention rate after 50 complete cycles is ?98% (the ratio of the discharge capacity at the 50.sup.th cycle to the discharge capacity at the first cycle, and so on), the capacity retention rate after 100 cycles is ?97.7%, and the capacity retention rate after 150 cycles is ?91.5%. Since this test example uses button battery for testing, the cycle performance can not be fully exerted. It can be predicted that when the negative electrode plate obtained by the present disclosure is used in full battery, the cycle performance of the obtained full battery will be further better than the cycle performance test results in Table 1.

[0375] By comparing the thickness of the electrode protective layer and the battery performance in Examples 1 and 9, it can be known that, in a thickness range of 1-10 nm, the electrode protective layer can significantly improve the performance of the obtained negative electrode plate, and the optimal thickness of the electrode protective layer is related to the material of the electrode protective layer, for example, when the electrode protective layer is made of Co.sub.xO, a thinner (e.g., 1 nm) electrode protective layer can play a good role in protection; when the electrode protective layer is made of In.sub.2O.sub.3, a thicker electrode protective layer (e.g., 10 nm) has better performance.

TABLE-US-00002 TABLE 2 Electrochemical performance of the negative electrode plate with the single-layer ternary oxide or laminated structure as the electrode protective layer First- cycle dis- charging Capacity retention Thick- specific rate % ness capacity 50 100 150 Material (nm) (mAh/g) cycles cycles cycles 373 97 63.5 44.7 Exam- Co.sub.xSnO.sub.2+x 10 367 99 98.8 92.5 ple 3 Co.sub.xSnO.sub.2+x 5 369 98.8 99.1 94.6 Co.sub.xSnO.sub.2+x 1 369 99 98.5 90.6 Exam- CuMn.sub.xO.sub.2 10 372 98.6 98.3 93.5 ple 4 CuMn.sub.xO2 5 371 98.7 98.4 94.2 CuMn.sub.xO2 1 372 98.8 98.6 91.7 Exam- Li.sub.4Ti.sub.5O.sub.12 5 368 98.6 98.3 94.3 ple 17 Exam- TiNb.sub.2O.sub.7 5 369 99.2 98.4 94.2 ple 18 Exam- CoSb.sub.2O.sub.6 5 366 99 98.4 92.1 ple 19 Exam- Co.sub.xO/Fe.sub.yO 5 371 98.8 98.5 90.1 ple 5 Exam- Co.sub.xO/In.sub.2O.sub.3 5 368 98.7 98.6 93.8 ple 20 Exam- In.sub.2O.sub.3/ZnO 5 366 99.1 98.3 94.1 ple 21

[0376] The results in Table 2 show that when the electrode protective layer is a single-layered ternary oxide or has a laminated structure, they are equivalent to the effect of a single-layered binary oxide.

[0377] However, it can be seen from comparing the results corresponding to electrode protective layers with different thicknesses in Example 3 and Example 4 that when the electrode protective layer is a ternary oxide, the thickness of the electrode protective layer has a more significant influence on the electrochemical performance of the negative electrode plate. Specifically, the thickness of 5 nm is preferable to that of 10 nm and 1 nm.

TABLE-US-00003 TABLE 3 Electrochemical performance results of negative electrode plates obtained in some examples and comparative example First-cycle discharging Capacity retention specific rate % Thickness capacity 50 100 150 Material Method (nm) (mAh/g) cycles cycles cycles 373 97 63.5 44.7 Example 7 Co.sub.2SnO.sub.4 Magnetron 5 371 98.2 94.5 93.8 sputtering Example 22 Co.sub.xSnO.sub.2+x CVD 5 372 98.6 90.1 88.9 Example 3 Co.sub.xSnO.sub.2+x ALD 5 369 98.8 99.1 94.6 Example 23 CuO Magnetron 5 366 98.2 95.3 92.7 sputtering Example 6 CuO CVD 5 368 98.6 92.1 90.5 Example 12 CuO ALD 5 372 98.6 98.2 94.8

[0378] In Tables 1 to 3, the material and thickness refer to the material and thickness of the electrode protective layer; the method is the setting method for the electrode protective layer; - indicates absence or no testing.

[0379] The results in Table 3 show that the electrode protection layers with excellent protective performance can be obtained using different preparation methods. Compared among magnetron sputtering, CVD and ALD, due to the denser and more uniform protective layer formed by ALD, its protection performance is superior.

[0380] The battery formed by assembling the electrode protective layers of negative electrode plate formed by using other materials of the present disclosure has good ion transmission performance, and the cycle performance of the lithium-ion battery is also improved to different degrees.

[0381] The above provides a detailed explanation of the examples of the present disclosure in conjunction with specific embodiments. However, the present disclosure is not limited to the aforementioned embodiments. Within the scope of knowledge possessed by ordinary skilled in the art, various changes can be made without departing from the aim of the present disclosure. In addition, the embodiments of the present disclosure and features in those embodiments can be combined with each other without conflict.