MAGNETIC CURRENT COLLECTOR AND NEGATIVE ELECTRODE PLATE THAT APPLIES SAME, LITHIUM METAL BATTERY, AND ELECTRONIC DEVICE

Abstract

A magnetic current collector includes a permanent magnet material layer. In the permanent magnet material layer, remanence intensity of a permanent magnet material is 0 T to 2 T. The magnetic current collector can introduce a magnetic field into the lithium metal battery. The magnetic field interacts electromagnetically with an electric field exerted by the battery to quicken a mass transfer process of lithium ions at an interface between a negative electrode and an electrolytic solution, homogenize a current density generated by a lithium-ion flow on a surface of the negative electrode, quicken a mass transfer process of lithium ions in a direction parallel to the current collector, and homogenize the distribution of lithium ions, so as to suppress lithium dendrites and improve the cycle performance of the lithium metal battery.

Claims

1. A magnetic current collector, comprising: a permanent magnet material layer, wherein, in the permanent magnet material layer, remanence intensity of a permanent magnet material is 0 T to 2 T.

2. The magnetic current collector according to claim 1, wherein a thickness of the permanent magnet material layer is 1 μm to 100 μm.

3. The magnetic current collector according to claim 1, wherein the permanent magnet material layer exists on at least one surface of a metallic current collector, and a thickness of the permanent magnet material layer is 0.1 μm to 10 μm.

4. The magnetic current collector according to claim 1, wherein the permanent magnet material comprises at least one of a rare earth permanent magnet material, a metallic permanent magnet material, or a ferrite-based permanent magnet material.

5. The magnetic current collector according to claim 4, wherein the rare earth permanent magnet material comprises at least one of SmCo.sub.5, Sm.sub.2Co.sub.17, Nd—Fe—B, Pr—Fe—B, or Sm—Fe—N; the metallic permanent magnet material comprises at least one of Al—Ni—Co, Fe—Cr—Co, Cu—Ni—Fe, or Fe—Co—V; and the ferrite-based permanent magnet material comprises a permanent magnet material formed by sintering Fe.sub.2O.sub.3 with at least one of nickel oxide, zinc oxide, manganese oxide, barium oxide, or strontium oxide.

6. The magnetic current collector according to claim 1, wherein a resistivity of the permanent magnet material is less than or equal to 200 Ω.Math.m.

7. The magnetic current collector according to claim 1, wherein the permanent magnet material layer further comprises a conductive material, and a mass percentage of the conductive material is less than 50%.

8. The magnetic current collector according to claim 7, wherein the conductive material comprises at least one of acetylene black, superconducting carbon, or Ketjen black.

9. A negative electrode plate comprising a magnetic current collector, the magnetic current collector comprises a permanent magnet material layer, wherein, in the permanent magnet material layer, remanence intensity of a permanent magnet material is 0 T to 2 T.

10. The negative electrode plate according to claim 9, wherein a thickness of the permanent magnet material layer is 1 μm to 100 μm.

11. The negative electrode plate according to claim 9, wherein a negative active material layer exists on a surface of the magnetic current collector, the negative active material layer comprises lithium, and a thickness of the negative active material layer is 5 μm to 200 μm.

12. The negative electrode plate according to claim 11, wherein a conductive layer is disposed between the magnetic current collector and the negative active material layer.

13. The negative electrode plate according to claim 12, wherein the conductive layer comprises at least one of Cu, Ni, Ti, Ag, or a carbon conductive agent.

14. A lithium metal battery, comprising the negative electrode plate according to claim 9.

15. The lithium metal battery according to claim 14, wherein a thickness of the permanent magnet material layer is 1 μm to 100 μm.

16. The lithium metal battery according to claim 14, wherein a negative active material layer exists on a surface of the magnetic current collector, the negative active material layer comprises lithium, and a thickness of the negative active material layer is 5 μm to 200 μm.

17. The lithium metal battery according to claim 16, wherein a conductive layer is disposed between the magnetic current collector and the negative active material layer.

18. The lithium metal battery according to claim 17, wherein the conductive layer comprises at least one of Cu, Ni, Ti, Ag, or a carbon conductive agent.

19. An electronic device, comprising the lithium metal battery according to claim 14.

Description

DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of this application clearer, the following describes this application in more detail with reference to embodiments. Evidently, the described embodiments are merely a part of but not all of the embodiments of this application. All other embodiments derived by a person of ordinary skill in the art based on the embodiments of this application fall within the protection scope of this application.

[0051] A permanent magnet material is magnetized by a using magnetizer (brand: Jiuju; model: MA2030) with a planar multi-stage magnetizing coil.

[0052] Remanence intensity of the permanent magnet material is measured by using a Tianheng TD8650 Teslameter-Gaussmeter.

[0053] The measurement procedure is as follows:

[0054] 1. Turning on the instrument. The display screen shows +000. If the display screen shows another value, pressing the reset button until the displayed value is zero.

[0055] 2. Selecting a test range based on an estimated remanence intensity.

[0056] 3. Placing a measuring side of a Hall probe of the instrument toward the measured permanent magnet vertically, so that a recessed dot on a sensor head indicates the measuring side of the probe. At this time, magnetic field lines of the measured permanent magnet pass through the Hall probe vertically.

[0057] 4. Reading the reading on the display screen of the instrument to obtain the remanence intensity of the permanent magnet.

[0058] Testing a Capacity Retention Rate:

[0059] Charging a lithium metal battery at a constant current of 0.5 C until the voltage reaches 4.4 V, then charging the battery at a constant voltage of 4.4 V until the current reaches 0.05 C, leaving the battery to stand for 10 minutes in a 25° C.±3° C. environment, and then discharging the battery at a current of 0.5 C until the voltage reaches 3.0 V, and recording a first-cycle discharge capacity as Q.sub.1. Repeating the foregoing charge and discharge process for 100 cycles, and recording the discharge capacity as Q.sub.100, and obtaining a 100.sup.th-cycle capacity retention rate based on the following formula: η=Q.sub.100/Q.sub.1×100%.

Preparation Example 1: Preparing a Positive Electrode Plate

[0060] Mixing lithium iron phosphate (LiFePO.sub.4) as a positive active materials, conductive carbon black (Super P), and polyvinylidene difluoride (PVDF) at a mass ratio of 97.5:1.0:1.5, adding N-methyl-pyrrolidone (NMP) as a solvent, blending the mixture into a slurry with a solid content of 0.75, and stirring the slurry evenly. Coating a 10 μm-thick positive current collector aluminum foil with the slurry evenly, drying the slurry at a temperature of 90° C., and forming a 100 μm-thick positive active material layer on one side of the positive current collector, so as to obtain a positive electrode plate coated with the positive active material layer on a single side. After completion of the coating, cutting the electrode plate into a size of 38 mm×58 mm for future use.

Preparation Example 2: Preparing an Electrolytic Solution

[0061] Mixing dioxolane (DOL) and dimethyl ether (DME) as a solvent at a volume ratio of 1:1 in a dry argon atmosphere, and then adding a lithium salt LiTFSI into the solvent, letting the lithium salt be dissolved and mixed evenly to obtain an electrolytic solution in which a lithium salt concentration is 1 mol/L.

Preparation Example 3: Preparing a Lithium Metal Battery

[0062] Using a 15 μm-thick polyethylene (PE) as a separator, placing the negative electrode plate prepared in each embodiment and comparative embodiment in the middle, placing one single-side-coated positive electrode plate as an upper layer and another as a lower layer, and placing a separator between each positive electrode plate and the negative electrode plate. After lamination, fixing four corners of the entire laminate structure by using adhesive tape, and then placing the laminate structure into an aluminum plastic film; and performing top-and-side sealing, electrolyte injection, and sealing to ultimately obtain a laminated lithium metal battery.

[0063] Preparing a Negative Electrode Plate

Embodiment 1

[0064] Preparing Nd—Fe—B sheets: Formulating metallic ingredients of Nd, Fe, and B at a molar ratio of 20:79:1, mixing and smelting the ingredients, and jet-milling the ingredients to obtain Nd—Fe—B alloy magnetic powder. Subjecting the magnetic powder to magnetic field orientation, and pressing the magnetic powder into a roughcast magnet, and then placing the roughcast magnet into a vacuum sintering furnace for sintering. The sintering process is: increasing the temperature to 400° C. at a speed of 10° C. per minute and keeping the temperature for 2 hours, increasing the temperature to 700° C. and keeping the temperature for 5 hours, then increasing the temperature to 850° C. and keeping the temperature for 1 hour, finally increasing the temperature to 1100° C. and sintering for 6 hours, and filling the furnace with argon to quickly cool down to a room temperature to obtain an Nd—Fe—B sheet.

[0065] Cutting the Nd—Fe—B sheet into a size of 50 □m in thickness, 40 mm in width, 60 mm in length, and then performing unsaturated magnetization at a magnetization intensity of 1 T (based on a criterion set to be less than 95% of the remanence intensity or intrinsic coercivity) by using an automated magnetizer, where a magnetization direction is parallel to a normal direction of the sheet, that is, the direction of the generated magnetic induction line is parallel to the direction of the exerted electric field; and measuring the remanence intensity to be 0.85 T. Using the magnetized Nd—Fe—B sheet as the negative electrode plate directly.

Embodiment 2

[0066] Performing magnetization at a magnetization intensity of 5 T (based on a criterion set to be higher than 2 to 4 times the remanence intensity or intrinsic coercivity), and measuring the remanence intensity to be 1.45 T. The remainder is the same as Embodiment 1.

Embodiment 3

[0067] Performing magnetization at a magnetization intensity of 8 T, and measuring the remanence intensity to be 1.50 T. The remainder is the same as Embodiment 1.

Embodiment 4

[0068] Performing magnetization at a magnetization intensity of 1 T, where the magnetization direction is perpendicular to the normal direction of the sheet, that is, the direction of the generated magnetic induction line is perpendicular to the direction of the exerted electric field; and measuring the remanence intensity to be 0.65 T. The remainder is same as Embodiment 1.

Embodiment 5

[0069] Performing magnetization at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.30 T. The remainder is the same as Embodiment 4.

Embodiment 6

[0070] Performing magnetization at a magnetization intensity of 8 T, and measuring the remanence intensity to be 1.38 T. The remainder is the same as Embodiment 4.

Embodiment 7

[0071] Preparing Al—Ni—Co sheets: Formulating metallic ingredients of Al, Ni, Co, and Fe at a molar ratio of 5:10:40:45, mixing and smelting the ingredients, and jet-milling the ingredients to obtain Al—Ni—Co alloy magnetic powder. Subjecting the magnetic powder to magnetic field orientation, and pressing the magnetic powder into a roughcast magnet, and then placing the roughcast magnet into a vacuum sintering furnace for sintering. The sintering process is: increasing the temperature to 300° C. at a speed of 5° C. per minute and keeping the temperature for 1 hours, increasing the temperature to 700° C. and keeping the temperature for 1 hours, then increasing the temperature to 750° C. and keeping the temperature for 1 hour, finally increasing the temperature to 1200° C. and sintering for 2 hours, and filling the furnace with argon to quickly cool down to a room temperature to obtain an Al—Ni—Co sheet.

[0072] Cutting the Al—Ni—Co sheet into a size of 10 μm in thickness, 40 mm in width, and 60 mm in length. Performing magnetization at a magnetization intensity of 5 T by using an automated magnetizer, where the magnetization direction is parallel to the normal direction of the sheet, that is, the direction of the generated magnetic induction line is parallel to the direction of the exerted electric field; and measuring the remanence intensity to be 1.35 T. Using the magnetized Al— Ni—Co sheet as a negative electrode plate directly.

Embodiment 8

[0073] Magnetizing a 50 μm-thick Al—Ni—Co sheet at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.33 T. The remainder is the same as Embodiment 7.

Embodiment 9

[0074] Magnetizing a 100 μm-thick Al—Ni—Co sheet at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.28 T. The remainder is the same as Embodiment 7.

Embodiment 10

[0075] Cutting a 10 μm-thick Al—Ni—Co sheet into a size of 40 mm×60 mm. Then performing magnetization at a magnetization intensity of 5 T, where the magnetization direction is perpendicular to the normal direction of the sheet, that is, the direction of the generated magnetic induction line is perpendicular to the direction of the exerted electric field; and measuring the remanence intensity to be 1.35 T. Using the Al— Ni—Co sheet as a negative electrode plate directly.

Embodiment 11

[0076] Magnetizing a 50 μm-thick Al—Ni—Co sheet at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.26 T. The remainder is the same as Embodiment 10.

Embodiment 12

[0077] Magnetizing a 100 μm-thick Al—Ni—Co sheet at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.06 T. The remainder is the same as Embodiment 10.

Embodiment 13

[0078] Sputtering an Sm.sub.2Co.sub.17 material layer on both surfaces of an 8 μm-thick copper foil by using a magnetron sputtering technology (with an MSP-300B magnetron sputtering machine manufactured by Beijing Chuangshiweina), where the thickness of the Sm.sub.2Co.sub.17 material layer sputtered on both surfaces is 1 μm; and cutting the copper foil into a size of 40 mm×60 mm. Then performing magnetization at a magnetization intensity of 1 T, where the magnetization direction is perpendicular to the normal direction of the current collector; and measuring the remanence intensity to be 0.81 T.

Embodiment 14

[0079] Performing magnetization at a magnetization intensity of 5 T, and measuring the remanence intensity to be 1.02 T. The remainder is the same as Embodiment 13.

Embodiment 15

[0080] Performing magnetization at a magnetization intensity of 8 T, and measuring the remanence intensity to be 1.15 T. The remainder is the same as Embodiment 13.

Embodiment 16

[0081] Sputtering a BaFe.sub.12O.sub.19 material layer on both surfaces of an 8 μm-thick copper foil by using a magnetron sputtering technology, where the thickness of the BaFe.sub.12O.sub.19 material layer sputtered on both surfaces is 0.1 μm; and cutting the copper foil into a size of 40 mm×60 mm. Then performing magnetization at a magnetization intensity of 5 T, where the magnetization direction is perpendicular to the normal direction of the current collector; and measuring the remanence intensity to be 0.42 T.

Embodiment 17

[0082] This embodiment is the same as Embodiment 16 except that the thickness of the BaFe.sub.12O.sub.19 material layer sputtered on both surfaces of the copper foil is 1 μm. The measured remanence intensity is 0.38 T.

Embodiment 18

[0083] This embodiment is the same as Embodiment 16 except that the thickness of the BaFe.sub.12O.sub.19 material layer sputtered on both surfaces of the copper foil is 10 μm. The measured remanence intensity is 0.24 T.

Embodiment 19

[0084] Sputtering, by using a magnetron sputtering technology, both surfaces of an 8 μm-thick copper foil with the Nd—Fe—B alloy magnetic powder obtained in Embodiment 1, so as to form an Nd—Fe—B material layer, where the thickness of the Nd—Fe—B material layer sputtered on both surfaces is 0.1 μm; and cutting the copper foil into a size of 40 mm×60 mm. Then performing magnetization at a magnetization intensity of 5 T, where the magnetization direction is perpendicular to the normal direction of the current collector; and measuring the remanence intensity to be 1.45 T.

Embodiment 20

[0085] Sputtering, by using a magnetron sputtering technology, both surfaces of an 8 μm-thick copper foil with the Al—Ni—Co alloy magnetic powder obtained in Embodiment 7, so as to form an Al—Ni—Co material layer, where the thickness of the Al—Ni—Co material layer sputtered on both surfaces is 0.1 μm; and cutting the copper foil into a size of 40 mm×60 mm. Then performing magnetization at a magnetization intensity of 5 T, where the magnetization direction is perpendicular to the normal direction of the current collector; and measuring the remanence intensity to be 1.45 T.

Embodiment 21

[0086] Performing cold calendering and lithium replenishment on the surface of the magnetic current collector (that is, the magnetized Al—Ni—Co sheet) prepared in Embodiment 7, where the pressure is 0.2 ton to 0.8 ton and the thickness of the lithium active layer is 10 μm to 100 μm.

Embodiment 22

[0087] Performing cold calendering and lithium replenishment on the surface of the magnetic current collector (that is, the copper foil sputtered with magnetized BaFe.sub.12O.sub.19 on both surfaces) prepared in Embodiment 16, where the pressure is 0.2 ton to 0.8 ton and the thickness of the lithium active layer is 10 μm to 100 μm.

Comparative Embodiment 1

[0088] Using a 10 μm-thick copper foil as a negative electrode plate directly.

Comparative Embodiment 2

[0089] Performing cold calendering and lithium replenishment on the surface of the 10 μm-thick copper foil, where the pressure is 0.2 ton to 0.8 ton and the thickness of the lithium active layer is 10 μm to 100 μm.

[0090] Table 1 shows performance parameters of a lithium metal battery assembled with the negative electrode plate prepared in each embodiment and comparative embodiment.

TABLE-US-00001 TABLE 1 Thickness of Thickness of 100.sup.th-cycle Current Remanence permanent magnet current capacity collector intensity material layer collector Magnetic field retention material (T) (μm) (μm) direction rate (%) Embodiment 1 Nd—Fe—B 0.85 50 50 Parallel 60 Embodiment 2 Nd—Fe—B 1.45 50 50 Parallel 75 Embodiment 3 Nd—Fe—B 1.50 50 50 Parallel 76 Embodiment 4 Nd—Fe—B 0.65 50 50 Perpendicular 58 Embodiment 5 Nd—Fe—B 1.30 50 50 Perpendicular 75 Embodiment 6 Nd—Fe—B 1.38 50 50 Perpendicular 78 Embodiment 7 Al—Ni—Co 1.35 10 10 Parallel 78 Embodiment 8 Al—Ni—Co 1.33 50 50 Parallel 70 Embodiment 9 Al—Ni—Co 1.28 100 100 Parallel 65 Embodiment Al—Ni—Co 1.35 10 10 Perpendicular 76 10 Embodiment Al—Ni—Co 1.26 50 50 Perpendicular 68 11 Embodiment Al—Ni—Co 1.06 100 100 Perpendicular 60 12 Embodiment Sm.sub.2Co.sub.17 0.81 1 10 Perpendicular 52 13 Embodiment Sm.sub.2Co.sub.17 1.02 1 10 Perpendicular 65 14 Embodiment Sm.sub.2Co.sub.17 1.15 1 10 Perpendicular 68 15 Embodiment BaFe.sub.12O.sub.19 0.42 0.1 8.2 Perpendicular 51 16 Embodiment BaFe.sub.12O.sub.19 0.38 1 10 Perpendicular 45 17 Embodiment BaFe.sub.12O.sub.19 0.24 10 28 Perpendicular 40 18 Embodiment Nd—Fe—B 1.45 0.1 8.2 Perpendicular 74 19 Embodiment Al—Ni—Co 1.28 0.1 8.2 Perpendicular 70 20 Embodiment Al—Ni—Co 1.35 10 10 Parallel 82 21 Embodiment BaFe.sub.12O.sub.19 0.42 0.1 8.2 Perpendicular 75 22 Comparative Cu / / 10 / 36 Embodiment 1 Comparative Cu / / 10 / 50 Embodiment 2

[0091] As can be seen from the comparison between Embodiments 1-22 and Comparative Embodiments 1-2, when the magnetic current collector according to this application is adopted, the cycle performance (100.sup.th-cycle capacity retention rate) of the battery is significantly improved. As can be seen from Embodiments 1-6 and Embodiments 13-15, the higher the remanence intensity of the permanent magnet material, the higher the cycle performance of the battery. For different magnetic materials, the same rule is exhibited.

[0092] As can be seen from Embodiments 1-6 and Embodiments 7-12, this application can be implemented regardless of the magnetization direction.

[0093] As can be seen from Embodiments 7-12 and Embodiments 16-18, with the same magnetization intensity, the increase in the thickness of the permanent magnet material layer slightly reduces the remanence intensity. The inventor also finds that the thickness of the permanent magnet material layer scarcely affects the capacity retention rate of the battery. Considering the energy density of the battery as well as the impact caused by the intensity of the permanent magnet material layer and a demagnetization factor, when the permanent magnet material layer according to this application is directly used as a current collector, the thickness of the magnetic current collector is 1 μm to 100 μm. When the permanent magnet material layer exists on at least one surface of the metallic current collector, the thickness of the permanent magnet material layer is 0.1 μm to 10 μm.

[0094] The foregoing descriptions are merely exemplary embodiments of this application, but are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application fall within the protection scope of this application.