Composite lithium supplement material, lithium supplement cathode and lithium ion battery

Abstract

The application provides a composite lithium supplementing material, a lithium supplementing positive electrode and a lithium ion battery containing the composite lithium supplementing material. The composite lithium supplementing material comprises at least lithium oxalate lithium supplementing agent L1, further comprises L2 and / or L3; L3 is mainly prepared by spray drying of an aqueous solution containing MoxC / NC and lithium oxalate to form a 4.3V decomposition potential lithium oxalate lithium supplementing agent; L2 is mainly prepared by freeze drying of an aqueous solution containing Mo2CMXene etched by HF and lithium oxalate to form a 4.1V decomposition potential lithium oxalate lithium supplementing agent; L1 is mainly prepared by electrospinning and carbonization of an organic solution containing MoxC / NC or Mo2CMXene etched by HF, lithium oxalate and PAN to form a 3.8V decomposition potential lithium oxalate lithium supplementing agent. The lithium supplementing positive electrode and the lithium ion battery prepared by using the composite lithium supplementing material can realize full life cycle lithium supplementing, has large cycle capacity and obvious capacity retention rate advantage.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a composite lithium replenishment material, a lithium replenishment cathode, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are becoming increasingly widely used, but the formation of SEI and CEI and the irreversible adsorption of active lithium by electrode materials with low kinetics and strong coupling inevitably lead to a decrease in reversible capacity, energy density loss, and cycle life degradation. Therefore, compensating for the loss of active lithium in the battery system is key to significantly improving battery energy density.

[0003] Currently, some studies have used lithium oxalate as a lithium replenishing agent. However, lithium-ion batteries that use lithium oxalate alone are mostly one-time lithium replenishment, and the performance degradation caused by the subsequent loss of active lithium has not been effectively solved. Summary of the Invention

[0004] Therefore, it is necessary to provide a positive electrode composite lithium replenishment material, a lithium replenishment positive electrode, a lithium-ion battery, and a method for preparing the same.

[0005] The present invention adopts the following technical solution:

[0006] This invention provides a composite lithium supplement material, comprising at least lithium oxalate supplement L1, and further comprising lithium oxalate supplement L2 and / or lithium oxalate supplement L3; the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (8-25):(4-20), and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L3 is (8-25):(2-20);

[0007] The lithium oxalate supplement L1 is a 3.8V decomposition potential lithium oxalate supplement prepared by electrospinning and carbonization of an organic solution containing nitrogen-doped defective molybdenum carbide (MoxC / NC), lithium oxalate, and polyacrylonitrile (PAN); the lithium oxalate supplement L2 is a 4.1V decomposition potential lithium oxalate supplement prepared by freeze-drying an aqueous solution containing molybdenum carbide (Mo2CMXene) and lithium oxalate; the lithium oxalate supplement L3 is a 4.3V decomposition potential lithium oxalate supplement prepared by spray drying an aqueous solution containing MoxC / NC and lithium oxalate; wherein, Mo2CMXene is prepared by etching molybdenum gallium carbide (Mo2Ga2C) with hydrofluoric acid (HF).

[0008] Preferably, the composite lithium supplement material includes lithium oxalate supplements L1, L2 and L3, with a mass ratio of (8-25):(4-20):(2-20) for the lithium oxalate supplements L1, L2 and L3.

[0009] Preferably, in the composite lithium supplement material, the amount of lithium oxalate supplement agent L1 is not higher than the amount of lithium oxalate supplement agent L2, and the amount of lithium oxalate supplement agent L3 is not higher than the amount of lithium oxalate supplement agent L2.

[0010] More preferably, the mass ratio of lithium oxalate supplement L1, lithium oxalate supplement L2 and lithium oxalate supplement L3 is 20:10:(2-5).

[0011] In some embodiments, the mass ratio of MoxC / NC to lithium oxalate is (1-3):(9-7); the mass ratio of Mo2CMXene to lithium oxalate is (1-3):(9-7); the mass ratio of MoxC / NC, lithium oxalate, and PAN is (1-3):(9-7):10; and the mass ratio of Mo2CMXene, lithium oxalate, and PAN is (1-3):(9-7):10.

[0012] The present invention also provides a lithium supplementation cathode, which is mainly prepared by lithium iron phosphate, binder, conductive agent and composite lithium supplementation material as described in any one of claims 1 to 3, wherein the mass ratio of lithium iron phosphate to composite lithium supplementation material is (28-36):(1-8).

[0013] Preferably, the mass ratio of lithium iron phosphate, conductive agent, and composite lithium replenishing material is (28-36):(2-8):(1-8). More preferably, the mass ratio of lithium iron phosphate, conductive agent, and composite lithium replenishing material is 32:4:4.

[0014] The present invention also provides a lithium-ion battery comprising the above-mentioned lithium-replenishing positive electrode, separator, lithium electrolyte and negative electrode.

[0015] In some embodiments, the negative electrode is selected from graphite negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (10-20):(10-20).

[0016] In some embodiments, the negative electrode is selected from silicon-carbon negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (20-30):(10-20).

[0017] This invention provides a lithium replenishment method for lithium-ion batteries, comprising the following steps: adding lithium oxalate replenishing agents with different decomposition potentials to lithium iron phosphate slurry to form a replenishing electrode, and then matching and assembling it with a graphite anode or a silicon-carbon anode to form a full battery that can achieve lithium replenishment throughout its entire life cycle.

[0018] In some embodiments, the conductive additive is selected from one or more of conductive carbon black, conductive graphite, porous carbon, graphitic carbon, activated carbon, Ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, graphene, and Super-P.

[0019] In some embodiments, the lithium replenishment electrode also includes aluminum foil / carbon-coated aluminum foil.

[0020] The adhesive is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride, polyacrylic acid, polyacrylic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate and styrene-butadiene rubber, and the organic solvent is selected from at least one of nitrogen-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0021] This invention provides a lithium-ion battery comprising the aforementioned lithium-replenishing positive electrode, separator, lithium electrolyte, and negative electrode. Preferably, the negative electrode is selected from graphite negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (10-20):(10-20).

[0022] The negative electrode is selected from silicon and carbon negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (20-30):(10-20).

[0023] The present invention also provides a lithium replenishment method for lithium-ion batteries, comprising the following steps: adding lithium oxalate replenishing agents L1, L2 and / or L3 with different decomposition potentials to the positive electrode lithium iron phosphate slurry to form a replenishing electrode, and then matching and assembling it with a graphite negative electrode or a silicon-carbon negative electrode to form a full battery that can achieve lithium replenishment throughout the entire life cycle.

[0024] Compared with the prior art, the core technical advantages of this invention are:

[0025] This invention prepares lithium oxalate supplements with different decomposition potentials by regulating the activity of a single lithium oxalate supplement. The combined use of lithium oxalate supplements with different decomposition potentials allows for the lithium replenishment effect of the battery under different lithium-deficient states through potential adjustment, thereby achieving a simultaneous improvement in the battery's initial coulombic efficiency, cycle life, and capacity retention.

[0026] This invention forms a composite lithium replenishing material by screening lithium oxalate replenishing agent L1, lithium oxalate replenishing agent L2 and / or lithium oxalate replenishing agent L3 and combining them. When applied to lithium iron phosphate cathode, it can achieve lithium replenishment throughout the entire life cycle of lithium-ion batteries, with large cycle capacity and significant retention rate advantages. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating the role of lithium-replenishing additives that decompose at different potentials in a battery. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The following embodiments are only used to illustrate the present invention, and are not intended to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0029] Example 1-1

[0030] This embodiment provides a method for preparing a 4.3V lithium oxalate lithium supplement (L3), including the following steps:

[0031] S1, 0.4 g ammonium molybdate and 0.85 g carbon nitride (C3N4) were ultrasonically dispersed in 50 mL of water, combined by rotary evaporation, and then carbonized at 800 °C for 3 hours in a tube furnace to obtain a highly defective active catalyst, nitrogen-doped molybdenum carbide (MoxC / NC).

[0032] S2, MoxC / NC and lithium oxalate were dispersed in an aqueous solution at a mass ratio of 3:7, and the concentration of lithium oxalate was controlled at 5 mg / mL. After spray drying, a 4.3V lithium oxalate decomposition supplement was prepared, denoted as L3.

[0033] Examples 1-2

[0034] This embodiment provides a method for preparing a 4.1V lithium oxalate lithium supplement (L2), including the following steps:

[0035] S1. Weigh 0.5g of molybdenum gallium carbide (Mo2Ga2C) and add it to a solution containing 12mL of hydrofluoric acid (HF) for etching for 24 hours. After ultrasonic centrifugation, obtain sheet-like molybdenum carbide (Mo2C Mxene).

[0036] S2, Mo2C MXene and lithium oxalate were ultrasonically dispersed in water at a ratio of 3:7, and the concentration of lithium oxalate was controlled at 5 mg / mL. After freeze-drying for 24 h, a 4.1V lithium oxalate decomposition lithium supplement was prepared, denoted as L2.

[0037] Examples 1-3

[0038] This embodiment provides a method for preparing a 3.8V lithium oxalate lithium supplement (L1), including the following steps:

[0039] S1, MoxC / NC, lithium oxalate, and polyacrylonitrile (PAN) are uniformly dispersed in 5 mL of dimethylformamide (DMF) solution at a mass ratio of 3:7:10 to form a mixture, and the concentration of lithium oxalate is controlled at 5 mg / mL.

[0040] S2, then the mixed solution was injected into a 5mL syringe, and electrospinned at 0.025mL / min under 18kV voltage to obtain the electrospinned product;

[0041] S3, the electrospun product was carbonized in a tube furnace at 350°C for 6 hours to obtain a 3.8V lithium oxalate supplement, denoted as L1.

[0042] Example 2-1

[0043] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0044] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 14 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 8 mg L1, 4 mg L2, 2 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0045] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0046] Example 2-2

[0047] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0048] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 21 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 12 mg L1, 6 mg L2, 3 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0049] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0050] Example 2-3

[0051] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0052] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 40 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 22 mg L1, 12 mg L2, 6 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0053] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0054] Examples 2-4

[0055] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0056] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 40 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 20 mg L1, 10 mg L2, 10 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0057] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0058] Examples 2-5

[0059] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0060] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 40 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 10 mg L1, 20 mg L2, 10 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0061] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0062] Examples 2-6

[0063] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps:

[0064] S1, weigh 320 mg lithium iron phosphate, 40 mg binder (PVDF), 40 mg conductive agent (KB), and 40 mg composite lithium supplement material (lithium oxalate supplement prepared in the above example: 10 mg L1, 10 mg L2, 20 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry.

[0065] S2, the prepared slurry is uniformly coated onto carbon-coated aluminum foil and vacuum dried at 110℃ for 12h to obtain a composite lithium replenishment electrode.

[0066] Examples 2-7

[0067] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps: weigh 320 mg of lithium iron phosphate, 40 mg of binder (PVDF), 40 mg of conductive agent (KB), and 40 mg of composite lithium replenishment material (using the lithium oxalate replenishment agent prepared in the above embodiment: 20 mg L1, 20 mg L2, 0 mg L3), and uniformly disperse them in NMP solvent to obtain a slurry; uniformly coat the prepared slurry onto carbon-coated aluminum foil, and vacuum dry at 110°C for 12 h to obtain a lithium electrode.

[0068] Examples 2-8

[0069] This embodiment provides a lithium replenishment electrode, the preparation method of which includes the following steps: weighing 320mg lithium iron phosphate, 40mg binder (PVDF), 40mg conductive agent (KB), and 40mg composite lithium replenishment material (using the lithium oxalate replenishment agent prepared in the above embodiment: 20mg L1, 0mg L2, 20mg L3), uniformly dispersing them in NMP solvent to obtain a slurry; uniformly coating the prepared slurry onto carbon-coated aluminum foil, and vacuum drying at 110℃ for 12h to obtain a lithium electrode.

[0070] Comparative Example 3-1

[0071] This comparative example provides a lithium electrode, the preparation method of which includes the following steps: weighing 320 mg of lithium iron phosphate, 40 mg of binder (PVDF), and 40 mg of conductive agent (KB), uniformly dispersing them in NMP solvent to obtain a slurry; uniformly coating the prepared slurry onto carbon-coated aluminum foil, and vacuum drying at 110°C for 12 h to obtain the lithium electrode. The lithium electrode of this comparative example does not contain the lithium oxalate lithium supplementer prepared in the above examples.

[0072] Comparative Example 3-2

[0073] This comparative example provides a lithium electrode, the preparation method of which includes the following steps: weighing 320 mg of lithium iron phosphate, 40 mg of binder (PVDF), 40 mg of conductive agent (KB), and 40 mg of lithium oxalate supplementing agent L2 prepared in the above embodiment, and uniformly dispersing them in NMP solvent to obtain a slurry; uniformly coating the prepared slurry onto carbon-coated aluminum foil, and vacuum drying at 110°C for 12 h to obtain a lithium electrode.

[0074] Comparative Example 3-3

[0075] This comparative example provides a lithium electrode, the preparation method of which includes the following steps: weigh 320 mg of lithium iron phosphate, 40 mg of binder (PVDF), 40 mg of conductive agent (KB), and 40 mg of lithium oxalate supplementing agent L3 prepared in the above example, and uniformly disperse them in NMP solvent to obtain a slurry; uniformly coat the prepared slurry onto carbon-coated aluminum foil, and vacuum dry at 110°C for 12 h to obtain a lithium electrode.

[0076] Comparative Examples 3-4

[0077] This comparative example provides a lithium electrode, the preparation method of which includes the following steps: weighing 320 mg of lithium iron phosphate, 40 mg of binder (PVDF), 40 mg of conductive agent (KB), and 40 mg of composite lithium supplementation material (lithium oxalate supplementation agent prepared in the above example: 0 mg L1, 20 mg L2, 20 mg L3), uniformly dispersing them in NMP solvent to obtain a slurry; uniformly coating the prepared slurry onto carbon-coated aluminum foil, and vacuum drying at 110°C for 12 h to obtain a lithium electrode.

[0078] Application performance testing:

[0079] 1) Fabrication of artificial graphite anode to simulate a battery:

[0080] The positive electrode uses the aforementioned lithium electrode sheet. The electrolyte is 1 mol of lithium hexafluorophosphide (LiPF6) dissolved in 1 L of a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. The separator is PP. The positive electrode, negative electrode, electrolyte, and separator are assembled into a simulated battery in an argon-protected glove box.

[0081] First, a simulated battery is charged to 3.8V at 50mA / g, then discharged to 2.5V at 50mA / g. Subsequently, it is cycled 500 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V. Next, it is charged to 4.1V at 50mA / g, then discharged to 2.5V at 50mA / g. This cycle is repeated 1500 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V. Finally, it is charged to 4.3V at 50mA / g, then discharged to 2.5V at 50mA / g. This cycle is repeated 2000 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V.

[0082] The statistical results of the initial charge / discharge efficiency and capacity retention are shown in the table below:

[0083]

[0084] As can be seen from the table above, the initial coulombic efficiency and capacity retention both increase to varying degrees with the increase in the amount of composite lithium replenishing agent material. In particular, the graphite anode simulated batteries prepared using the lithium replenishing electrodes of Examples 2-1 to 2-8 still retain 90% or more of the capacity retention after 2000 cycles and 85% or more of the capacity retention after 5000 cycles.

[0085] However, it is worth noting that the amount of composite lithium replenishing agent material used is not necessarily better the higher it is. If the amount exceeds 10% of the active material of lithium iron phosphate, over-lithiation may occur, and the overall capacity / energy density of the battery may be reduced to a certain extent, which is not conducive to the improvement of overall performance.

[0086] 2) Fabrication of a silicon / carbon anode simulated battery:

[0087] The positive electrode uses the aforementioned lithium electrode sheet. The electrolyte is 1 mol of lithium hexafluorophosphide (LiPF6) dissolved in 1 L of a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. The separator is PP. The positive electrode, negative electrode, electrolyte, and separator are assembled into a simulated battery in an argon-protected glove box.

[0088] First, a simulated battery is charged to 3.8V at 50mA / g, then discharged to 2.5V at 50mA / g. Subsequently, it is cycled 200 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V. Next, it is charged to 4.1V at 50mA / g, then discharged to 2.5V at 50mA / g. This cycle is repeated 300 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V. Finally, it is charged to 4.3V at 50mA / g, then discharged to 2.5V at 50mA / g. This cycle is repeated 500 times at a 1C current density, with charge / discharge cutoff voltages ranging from 3.65V to 2.5V.

[0089] The statistical results of the initial charge / discharge efficiency and capacity retention are shown in the table below:

[0090]

[0091] As can be seen from the results in the table above, in particular, the silicon-carbon anode simulated batteries prepared using the lithium-added electrodes of Examples 2-1 to 2-8 still retain 80% or more of the capacity after 500 cycles and 74% or more of the capacity after 1000 cycles.

[0092] The above only shows some of the experimental examples. In fact, the inventors' team discovered through extensive research that:

[0093] 1) The combination of lithium oxalate supplementary agents with different oxidation potentials from different preparation processes can significantly affect the initial coulombic efficiency and cycle capacity retention of lithium-ion batteries. In lithium-ion battery systems with lithium iron phosphate cathodes, sufficient addition of lithium oxalate supplementary agent L1 is beneficial for initial efficiency and capacity retention in the early cycle stage; addition of lithium oxalate supplementary agent L2 mainly compensates for mid-cycle consumption; addition of lithium oxalate supplementary agent L3 is mainly aimed at lithium deficiency in the later cycle stage, and a small amount can achieve good capacity retention. The lack of lithium oxalate supplementary agent L1 will make the initial activity loss uncompensated, resulting in low initial efficiency and poor capacity retention.

[0094] 2) The proportion of lithium iron phosphate, conductive agent and composite lithium replenishment material needs to be controlled. The composite lithium replenishment material should be controlled to no more than 10% of the active material in order to ensure that the battery energy density is not excessively lost while improving cycle life and capacity.

[0095] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite lithium supplementation material, characterized in that, It includes at least lithium oxalate supplement L1, and also includes lithium oxalate supplement L2 and / or L3; the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (8~25):(4~20), and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L3 is (8~25):(2~20). The lithium oxalate supplement L1 is mainly prepared by electrospinning and carbonization of an organic solution of nitrogen-doped defective molybdenum carbide MoxC / NC, lithium oxalate, and polyacrylonitrile PAN, or an organic solution containing sheet-like molybdenum carbide Mo2CMXene, lithium oxalate, and PAN. It is a lithium oxalate supplement with a decomposition potential of 3.8V. The lithium oxalate supplement L2 is a lithium oxalate supplement with a decomposition potential of 4.1V prepared by freeze-drying an aqueous solution containing flake molybdenum carbide (Mo2CMXene) and lithium oxalate. The lithium oxalate supplement L3 is mainly prepared by spray drying of an aqueous solution containing MoxC / NC and lithium oxalate, resulting in a lithium oxalate supplement with a decomposition potential of 4.3V. The Mo2CMXene is prepared by etching molybdenum gallium carbide (Mo2Ga2C) with hydrofluoric acid HF.

2. The composite lithium replenishment material according to claim 1, characterized in that, Including lithium oxalate supplement L1, lithium oxalate supplement L2 and lithium oxalate supplement L3; The mass ratio of lithium oxalate supplements L1, L2, and L3 is (8~25):(4~20):(2~20).

3. The composite lithium replenishment material according to claim 1 or 2, characterized in that, The mass ratio of MoxC / NC to lithium oxalate is (1~3):(9~7); The mass ratio of Mo2CMXene to lithium oxalate is (1~3):(9~7); The mass ratio of MoxC / NC, lithium oxalate, and PAN is (1~3):(9~7):10; The mass ratio of Mo2CMXene, lithium oxalate, and PAN is (1~3):(9~7):

10.

4. A lithium-added cathode, characterized in that, It is mainly prepared by using lithium iron phosphate, binder, conductive agent and composite lithium supplementation material as described in any one of claims 1 to 3, wherein the mass ratio of lithium iron phosphate to composite lithium supplementation material is (28~36):(1~8).

5. The lithium-added cathode according to claim 4, characterized in that, The mass ratio of lithium iron phosphate, conductive agent and composite lithium supplement material is (28~36):(2~8):(1~8).

6. The lithium-added cathode according to claim 5, characterized in that, The mass ratio of lithium iron phosphate, conductive agent and composite lithium replenishment material is 32:4:

4.

7. A lithium-ion battery, characterized in that, It comprises the lithium-filled positive electrode, separator, lithium electrolyte and negative electrode as described in any one of claims 4 to 6.

8. The lithium-ion battery according to claim 7, characterized in that, The negative electrode is selected from graphite negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (10 ~ 20): (10 ~ 20).

9. The lithium-ion battery according to claim 7, characterized in that, The negative electrode is selected from silicon-carbon negative electrodes, and the mass ratio of lithium oxalate supplement L1 to lithium oxalate supplement L2 is (20 ~ 30): (10 ~ 20).

10. A method for replenishing lithium in lithium-ion batteries, characterized in that, The process includes the following steps: adding the composite lithium replenishment material according to any one of claims 1 to 3 with different decomposition potentials to the positive electrode lithium iron phosphate slurry to form a lithium replenishment electrode, and then matching and assembling it with a graphite anode or a silicon-carbon anode to form a full battery that can achieve lithium replenishment throughout its entire life cycle.

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