Modified Lithium Ion Negative Electrode Material, and Preparation Therefor and Use Thereof

Abstract

The present disclosure relates to the technical field of batteries, and in particular, to a modified lithium ion negative electrode material, and preparation therefor and use thereof. The preparation method includes the following steps: dropwise adding a mixed solution of a titanium source and a lithium source into a mixed solution of an iron salt and an organic acid, adjusting the pH to 5.0-7.0, and stirring to obtain a wet gel; drying and crushing the wet gel, and then calcinating to obtain a LiFeTiO.sub.4 composite oxide; and reducing the LiFeTiO.sub.4 composite oxide to obtain the modified lithium ion negative electrode material. In the present disclosure, a spinel modified negative electrode material lithium iron titanium oxide is synthesized by using a citric acid sol-gel method, thereby not only greatly improving the charging and discharging capacity thereof, but also improving the large-current charging and discharging capability thereof.

Claims

1. A preparation method for a modified lithium ion negative electrode material, comprising the following steps, S1: adding an organic acid to an iron salt solution to obtain a solution I; at the same time, dissolving a titanium source and a lithium source in an alcohol solvent to obtain a solution II; S2: dropwise adding the solution II into the solution I, adjusting the pH to 5.0-7.0, and continuing stirring to obtain a wet gel; S3: drying the wet gel to form a xerogel, grinding and crushing the xerogel, and calcinating to obtain a LiFeTiO.sub.4 composite oxide; and S4: under the action of a reducing gas, performing a heat treatment on the LiFeTiO.sub.4 composite oxide to obtain the modified lithium ion negative electrode material, wherein the chemical formula of the modified lithium ion negative electrode material is LiFeTiO.sub.x, where 1<x<4; in step S3, the calcination is carried out twice, in which the temperature for the first calcination is 260-350 C., and the time is 1-5 h; and the temperature for the second calcination is 550-750 C., and the time is 1.5-4 h; in step S4, the reducing gas is hydrogen, the temperature for the heat treatment is 350-650 C., and the time is 2-8 h.

2. The preparation method for a modified lithium ion negative electrode material according to claim 1, wherein the molar ratio of the iron salt in the solution I to the lithium source in the solution II is (0.1-0.3):1.

3. The preparation method for a modified lithium ion negative electrode material according to claim 1, wherein in step S1, the addition amount of the organic acid is 1-5 times of the mole number of metal ions, and the metal ions are lithium ions, iron ions and titanium ions.

4. The preparation method for a modified lithium ion negative electrode material according to claim 1, wherein the iron salt is selected from one or more of ferric nitrate, ferric chloride and ferric sulfate; the organic acid is selected from one or more of citric acid, malic acid and tartaric acid; the titanium source is selected from one or more of tetrabutyl titanate, n-butyl titanate and isopropyl titanate; the lithium source is selected from one or more of lithium acetate, lithium carbonate, lithium oxalate and lithium nitrate; and the alcohol solvent is selected from one or more of ethanol, methanol, ethylene glycol and diethylene glycol.

5. The preparation method for a modified lithium ion negative electrode material according to claim 1, wherein in step S2, the stirring is continued for 3-6 h under a condition of 30-50 C., so as to obtain a wet gel.

6. A modified lithium ion negative electrode material prepared by using the preparation method according to claim 1.

7. A negative electrode sheet, comprising a negative electrode active material layer, wherein the negative electrode active material layer comprises the modified lithium ion negative electrode material according to claim 6.

8. A battery, comprising the negative electrode sheet according to claim 7.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0043] FIG. 1 is a result diagram of cycle tests of batteries prepared by using the materials obtained in Example 1 and Comparative Example 1.

[0044] FIG. 2 is a result diagram of cycle tests of batteries prepared by using the materials obtained in Comparative Example 2 and Comparative Example 1.

[0045] FIG. 3 is a result diagram of rate discharge tests of batteries prepared by using the materials obtained in Example 1 and Comparative Example 1.

[0046] FIG. 4 is a result diagram of charge and discharge tests of batteries prepared by using the materials obtained in Example 1 and Comparative Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, the present disclosure will be further described with reference to the accompanying drawings and specific embodiments, so that a person skilled in the art could better understand the present disclosure and implement same, but the embodiments listed are not intended to limit the present disclosure.

[0048] The present disclosure provides a preparation method for a modified lithium ion negative electrode material, including the following steps: [0049] S1: adding an organic acid to an iron salt solution, and performing ultrasonic dispersion for 0.5-1 h to obtain a solution I; [0050] at the same time, dissolving a titanium source and a lithium source in an alcohol solvent, stirring same for 0.5-2 h, to obtain a clear and transparent solution II; [0051] wherein the molar ratio of the iron salt to the lithium source is (0.1-0.3):1, and the addition amount of citric acid is 1-2 times of the mole number of metal ions; [0052] S2: slowly dropwise adding the solution II into the solution I under a stirring state at a rotational speed of 400-800 r/min, after the dropwise addition is completed, adding ammonia water to adjust the pH to 5.0-7.0, continuing stirring, and stirring at a constant temperature of 30-50 C. for 3-6 h to form a wet gel; [0053] S3: drying the wet gel at 60-90 C. for 24-72 h to form a xerogel, and then grinding same to form a powder; [0054] heating the powder from room temperature (255 C.) to 260-350 C. at a heating rate of 1-2 C./min and maintaining the temperature for 1-5 h to remove the citric acid; after the temperature is reduced to room temperature, taking same out, grinding and then performing second calcination, increasing the temperature from room temperature to 550-750 C. and maintaining the temperature for 1.5-4 h, and the heating rate being 4-6 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide; and [0055] S4: introducing a mixed gas of hydrogen and an inert gas, the gas flow rate being 50-70 mL/min, increasing the temperature of the LiFeTiO.sub.4 composite oxide to 350-650 C. at a heating rate of 4-6 C./min, maintaining the temperature for 2-8 h, and then cooling to room temperature, so as to obtain a modified lithium ion negative electrode material, i.e. a LiFeTiO.sub.x composite oxide.

[0056] Example 1 Synthesis of modified lithium ion negative electrode material lithium titanium oxide by a sol-gel method [0057] 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 4.5 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; [0058] and in another container, 1.6 mol of tetrabutyl titanate and 1.3 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0059] The solution II was dropwise added into the solution I, mechanical stirring was performed rapidly at 400 r/min; after the dropwise addition was completed, the pH value of the mixed solution was adjusted to 6.0 by using ammonia water, and the mixed solution was stirred at a constant temperature of 40 C. for 6 h to form a wet gel; and [0060] the wet gel was dried at a condition of 80 C. for 48 h to form a xerogel, and then the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 300 C. and maintained for 2 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 600 C. and maintained for 2 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

[0061] A solid powder of the LiFeTiO.sub.4 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 400 C. at a heating rate of 5 C./min, the maintaining time being 6 h, so as to obtain a LiFeTiO.sub.x composite oxide negative electrode material (Fe content being 2.8%), wherein 1<x<4. Since gas phase reduction would convert some Ti.sup.4+ into Ti.sup.3+, lattice distortion would occur around the material to generate a large amount of oxygen vacancies. However, it couldn't be determined how much Ti.sup.4+ was converted into Ti.sup.3+, only that x ranged from 1 to 4.

[0062] Example 2 Synthesis of modified lithium ion negative electrode material lithium titanium oxide by a sol-gel method [0063] 0.16 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 4.5 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; [0064] and in another container, 1.56 mol of tetrabutyl titanate and 1.28 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0065] The solution II was dropwise added into the solution I, mechanical stirring was performed rapidly at 400 r/min; after the dropwise addition was completed, the pH value of the mixed solution was adjusted to 6.0 by using ammonia water, and the mixed solution was stirred at a constant temperature of 40 C. for 6 h to form a wet gel; and [0066] the wet gel was dried at a condition of 80 C. for 48 h to form a xerogel, and then the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 300 C. and maintained for 2 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 600 C. and maintained for 2 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

[0067] A solid powder of the LiFeTiO.sub.4 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 400 C. at a heating rate of 5 C./min, the maintaining time being 6 h, so as to obtain a LiFeTiO.sub.x composite oxide negative electrode material (Fe content being 4.05%).

[0068] Example 3 Synthesis of modified lithium ion negative electrode material lithium titanium oxide by a sol-gel method [0069] 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 6 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; [0070] and in another container, 1.6 mol of tetrabutyl titanate and 1.3 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0071] The solution II was dropwise added into the solution I, mechanical stirring was performed rapidly at 400 r/min; after the dropwise addition was completed, the pH value of the mixed solution was adjusted to 6.0 by using ammonia water, and the mixed solution was stirred at a constant temperature of 40 C. for 6 h to form a wet gel; and [0072] the wet gel was dried at a condition of 80 C. for 48 h to form a xerogel, and then the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 300 C. and maintained for 2 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 600 C. and maintained for 2 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

[0073] A solid powder of the LiFeTiO.sub.4 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 500 C. at a heating rate of 5 C./min, the maintaining time being 4 h, so as to obtain a LiFeTiO.sub.x composite oxide negative electrode material.

Example 4

[0074] The difference from Example 1 merely lies in that the mixed solution was stirred at a constant temperature of 30 C. for 6 h to form a wet gel.

Example 5

[0075] The difference from Example 1 merely lies in that the mixed solution was stirred at a constant temperature of 50 C. for 3 h to form a wet gel.

Example 6

[0076] The difference from Example 1 merely lies in that the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 260 C. and maintained for 5 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 550 C. and maintained for 4 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

Example 7

[0077] The difference from Example 1 merely lies in that the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 350 C. and maintained for 1 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 750 C. and maintained for 1.5 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

Example 8

[0078] The difference from Example 1 merely lies in that a solid powder of the LiFeTiO.sub.4 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 350 C. at a heating rate of 5 C./min, the maintaining time being 8 h, so as to obtain a LiFeTiO.sub.x composite oxide negative electrode material.

Example 9

[0079] The difference from Example 1 merely lies in that a solid powder of the LiFeTiO.sub.4 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 650 C. at a heating rate of 5 C./min, the maintaining time being 2 h, so as to obtain a LiFeTiO.sub.x composite oxide negative electrode material.

Example 10

[0080] The difference from Example 1 merely lies in that 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 4.5 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; and in another container, 1.6 mol of tetrabutyl titanate and 1 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

Example 11

[0081] The difference from Example 1 merely lies in that 0.3 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 4.5 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; and in another container, 1.6 mol of tetrabutyl titanate and 1 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

Example 12

[0082] The difference from Example 1 merely lies in that 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 3 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; and in another container, 1.6 mol of tetrabutyl titanate and 1.3 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

Example 13

[0083] The difference from Example 1 merely lies in that 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 15 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; and in another container, 1.6 mol of tetrabutyl titanate and 1.3 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0084] The test results of the negative electrode materials prepared in Examples 4 to 13 were shown in Table 1.

TABLE-US-00001 TABLE 1 Negative electrode material Battery Specific Film Number of cycles Granularity surface resistance (90% discharging / (D50) area (m.sup.2/g) (m) capacity) Example 4 1.22 5.361 3.1 3875 Example 5 1.23 5.339 3.2 3821 Example 6 1.25 5.267 3.2 3799 Example 7 1.24 5.098 3.2 3783 Example 8 1.23 4.935 3.3 3527 Example 9 1.25 4.866 3.3 3513 Example 10 1.24 4.835 3.4 3493 Example 11 1.25 4.798 3.4 3269 Example 12 1.25 4.771 3.4 3248 Example 13 1.23 4.725 3.5 3211

[0085] Comparative Example 1 Synthesis of modified lithium ion negative electrode material lithium titanium oxide by a sol-gel method [0086] 1.35 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was dissolved in 100 mL of deionized water, and an ultrasonic treatment was performed for 0.5 h, so as to obtain a solution I; [0087] and in another container, 0.5 mol of tetrabutyl titanate and 0.4 mol of lithium acetate were taken and mixed with 150 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0088] The solution II was dropwise added into the solution I, mechanical stirring was performed rapidly at 400 r/min; after the dropwise addition was completed, the pH value of the mixed solution was adjusted to 6.0 by using ammonia water, and the mixed solution was stirred at a constant temperature of 40 C. for 6 h to form a wet gel; and [0089] the wet gel was dried at a condition of 80 C. for 48 h to form a xerogel, and then the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 300 C. and maintained for 2 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 600 C. and maintained for 2 h, the heating rate being 5 C./min, so as to obtain a Li.sub.4Ti.sub.5O.sub.12 composite oxide.

[0090] A solid powder of the Li.sub.4Ti.sub.5O.sub.12 composite oxide was placed into a tube furnace, 10% of H.sub.2Ar was introduced, a gas flow rate was maintained at 60 mL/min, the temperature was increased from room temperature to 400 C. at a heating rate of 5 C./min, the maintaining time being 6 h, so as to obtain a Li.sub.4Ti.sub.5O.sub.x composite oxide negative electrode material.

[0091] Comparative Example 2 Synthesis of modified lithium ion negative electrode material lithium titanium oxide by a sol-gel method [0092] 0.1 mol of Fe(NO.sub.3).sub.3.Math.9H.sub.2O was taken to formulate a 100 mL aqueous solution, an ultrasonic treatment was performed to achieve uniform mixing, then 4.5 mol of C.sub.6H.sub.8O.sub.7.Math.H.sub.2O (citric acid monohydrate) was added and the ultrasonic treatment continued for 0.5 h to obtain a solution I; [0093] and in another container, 1.6 mol of tetrabutyl titanate and 1.3 mol of lithium acetate were taken and mixed with 550 mL of absolute ethyl alcohol, and then were stirred continuously for a time period of 0.5 h to obtain a clear and transparent solution II.

[0094] The solution II was dropwise added into the solution I, mechanical stirring was performed rapidly at 400 r/min; after the dropwise addition was completed, the pH value of the mixed solution was adjusted to 6.0 by using ammonia water, and the mixed solution was stirred at a constant temperature of 40 C. for 6 h to form a wet gel; and [0095] the wet gel was dried at a condition of 80 C. for 48 h to form a xerogel, and then the xerogel was ground into a powder, and in a muffle furnace, the temperature was increased from room temperature to 300 C. and maintained for 2 h, wherein the heating rate was 2 C./min. After the temperature was reduced to room temperature, the xerogel was taken out, ground again and then subjected to second calcination, the temperature was increased from room temperature to 600 C. and maintained for 2 h, the heating rate being 5 C./min, so as to obtain a LiFeTiO.sub.4 composite oxide.

Analysis of Results

[0096] 1. The granularity, specific surface area and film resistance of the materials obtained in Example 1 and Comparative Example 1 were tested, in which the film resistance was tested by a TT-ACCF-G1R film resistance meter, and 10 tests were performed and an average value thereof was taken.

[0097] The results showed that:

[0098] In Example 1, the granularity was: D10 of 0.41, D50 of 1.22, D90 of 5.14 and D99 of 8.88; in Comparative Example 1, the granularity was: D10 of 0.43, D50 of 1.25, D90 of 5.07 and D99 of 8.92; [0099] in Example 1, the specific surface area was 6.432 m.sup.2/g, higher than 4.593 m.sup.2/g in Comparative Example 1; and [0100] in Example 1, the film resistance was 3.1 m, lower than 3.6 m in Comparative Example 1. [0101] 2. The materials obtained in Example 1 and Comparative Examples 1-2 were used to prepare batteries and the batteries were tested.

[0102] A preparation method for a positive electrode sheet includes: a positive electrode, i.e. lithium iron phosphate, a conductive agent Super P and a binder PVDF were mixed at a mass ratio of 97:2:1, and then an NMP solvent was added for uniform mixing to prepare a positive electrode slurry; and the positive electrode slurry was uniformly coated, according to a certain areal density, onto the front and back surfaces of an aluminum foil coated with a conductive carbon layer, and air blow drying at 80-120 C., and then cold pressing, die-cutting were performed, to obtain a positive electrode sheet.

[0103] A preparation method for a negative electrode sheet includes: a negative electrode material obtained, conductive carbon black Super P and a negative electrode binder CMC at a mass ratio of 96:2:2 were uniformly mixed with deionized water to prepare a negative electrode slurry; the negative electrode slurry was uniformly coated on the front and back surfaces of a copper foil according to a certain areal density, and air blow drying at 80-120 C., and then cold pressing, die-cutting were performed to obtain a negative electrode sheet.

[0104] A preparation method for a battery includes: the positive electrode sheet, a PP separator and the negative electrode sheet were prepared into a jelly roll, wherein the PP separator needs to be able to completely wrap the positive electrode sheet and the negative electrode sheet. After the obtained jelly roll was placed in a metal housing or wrapped by an aluminum plastic film, an electrolyte solution was injected into the metal housing or aluminum plastic film. Finally, a lithium iron phosphate battery was prepared by processes such as still standing, formation and capacity division.

[0105] A test method for cycling of the battery cycle is: at 252 C., the battery was charged to 2.5 V under a 1 C constant current and a constant voltage, with a cut-off current being 0.05 C; and the battery stood still for 30 min, then was discharged to 1.0 V at 1 C, the process continued, and the number of cycles was recorded.

[0106] A test method for discharge rate is as follows: at 252 C., the battery was charged to 2.5 V under a 1 C constant current and a constant voltage, with a cut-off current being 0.05 C; and the battery stood still for 30 min, then was discharged to 1.0 V at 0.3 C, 0.5 C, 1 C, 2 C, 3 C, 5 C and 10 C, and different discharge currents were recorded for 10 cycles.

[0107] As shown in FIG. 1, it can be determined that the cycle performance of Example 1 is far superior to that of Comparative Example 1, and decreased by 8.9% at the 4000-th cycle. The initial capacity in Example 1 was 106.7 Ah, slightly higher than 104.5 Ah in Comparative Example 1.

[0108] As shown in FIG. 2, it can be determined that the battery of Comparative Example 2 began to rapidly attenuate at a cycle less than 2500-th cycle, and the cycle performance thereof was poorer than that in Example 1.

[0109] As shown in FIG. 3, it can be determined that the large-current charging and discharging capability in Example 1 was high, and under a high current of 10 C, the discharging capacity thereof was maintained at about 70%, and the discharging capacity thereof was much higher than that of Comparative Example 1.

[0110] As shown in FIG. 4, it can be determined that the charging and discharging capacity of Example 1 was significantly higher than that of Comparative Example 1.

[0111] Apparently, the described embodiments are merely examples made for clear illustration, and are not intended to limit the embodiments. For a person of ordinary skill in the art, other variations or modifications of different forms may be made on the basis of the described illustration. Herein, it is neither necessary nor possible to list all embodiments in an exhaustive manner. Moreover, obvious variations or modifications derived therefrom are still within the scope of protection of the present invention and creation.