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CN-121460494-B - Negative electrode piece, preparation method thereof and lithium ion battery

CN121460494BCN 121460494 BCN121460494 BCN 121460494BCN-121460494-B

Abstract

Aiming at the problem that the energy density and the multiplying power performance of the battery are difficult to be considered in the material homogenization design of the single coating of the negative electrode plate of the existing lithium ion battery, the invention provides a negative electrode plate, a preparation method thereof and a lithium ion battery. The negative electrode plate comprises a negative electrode current collector and a plurality of negative electrode active layers, wherein the plurality of negative electrode active layers are sequentially 1 st, 2 nd and the third and the fourth, the nth negative electrode active layer, n is more than or equal to 2, the ith negative electrode active layer and the i-1 th negative electrode active layer respectively comprise the ith negative electrode active substance and the i-1 th negative electrode active substance, the relationship ① or ②：①C i ＞C i‑1 ;②C i =C i‑1 is met, the SOC i ＞SOC i‑1 ;C i and the C i‑1 are respectively the minimum lithium-out multiplying power of the ith negative electrode active layer and the i-1 th negative electrode active layer, and the SOC i and the SOC i‑1 are respectively the critical lithium-out states of the ith negative electrode active layer and the i-1 th negative electrode active layer.

Inventors

  • HAO RONG
  • RUAN ZEWEN
  • LIANG JINGZHE
  • SHEN XI

Assignees

  • 深圳市懋略技术研究有限公司

Dates

Publication Date
20260508
Application Date
20260108

Claims (16)

  1. 1. The negative electrode plate is characterized by comprising a negative electrode current collector and a plurality of negative electrode active layers arranged on at least one surface of the negative electrode current collector, wherein the plurality of negative electrode active layers are sequentially 1 st, 2 nd and third, n < th > negative electrode active layers, n is more than or equal to 2, the direction from the 1 st negative electrode active layer to the n < th > negative electrode active layer is a direction far away from the negative electrode current collector, the i < th > negative electrode active layer is any negative electrode active layer from the 2 < th > negative electrode active layer to the n < th > negative electrode active layer, the i < th > negative electrode active layer comprises an i < th > negative electrode active material, the i < th > negative electrode active material comprises i < th > particles, and the i < th > negative electrode active material comprises i < th > 1 > particles; the i-th anode active layer and the i-1-th anode active layer satisfy the following relational expression ① or ②: ①C i ＞C i-1 ; ②C i =C i-1 And SOC i ＞SOC i-1 ; Wherein, C i is the minimum lithium-out multiplying power of the ith negative electrode active layer, C i-1 is the minimum lithium-out multiplying power of the ith-1 negative electrode active layer, SOC i is the critical lithium-out state of the ith negative electrode active layer, and SOC i-1 is the critical lithium-out state of the ith-1 negative electrode active layer; The test calculation steps of C i and SOC i are as follows: S1, preparing an ith anode active layer by independently adopting the ith anode active material, and preparing a button cell; S2, carrying out a charging test on the button cell under the multiplying power of 0.1C to obtain the charging capacity of the button cell, and recording the charging capacity as Q ci ; S3, performing discharge test on the button cell under different multiplying powers until the discharge curve of the button cell is lower than 0V, wherein the different multiplying powers are a multiplied by C, a is an integer multiple of 0.1, and a is more than or equal to 1; When the discharge curve of the button cell is lower than 0V, the corresponding multiplying power is marked as C i of the ith negative electrode active material, and meanwhile, the discharge capacity of the button cell from the discharge curve to 0V at the multiplying power is marked as Q di of the ith negative electrode active material; S4, calculating to obtain the SOC i of the ith anode active layer according to the relation SOC i =Q di /Q ci ; Repeating the test steps S1-S4 to obtain C i-1 and SOC i-1 of the i-1 th anode active layer; The ith particle and the ith-1 particle are primary particles, the average particle size of the ith particle is D i , and the average particle size of the ith-1 particle is D i-1 ,D i ＜D i-1 ; Or, the ith particle and the (i-1) th particle are secondary particles, the secondary particles are formed by granulating primary particles, the average particle size of the primary particles of the ith particle is D i , and the average particle size of the primary particles of the (i-1) th particle is D i-1 ,D i ＜D i-1 ; Or, the ith particle and the ith-1 particle include a primary particle and a secondary particle, the secondary particle is formed by granulating the primary particle, the primary particle average particle diameter of the ith particle is D i , and the primary particle average particle diameter of the ith-1 particle is D i-1 ,D i ＜D i-1 .
  2. 2. The negative electrode tab of claim 1, wherein the i-th particle has an average carbon coating amount of ω i and the i-1-th particle has an average carbon coating amount of ω i-1 ,ω i ≥ω i-1 .
  3. 3. The negative electrode tab of claim 2, wherein the range of omega i and omega i-1 is 0% -3.0%.
  4. 4. The negative electrode tab of claim 1, wherein the D i and D i-1 are both in the range of 3-25 μm.
  5. 5. The negative electrode tab of claim 1, wherein the i-th particle has an average interlayer spacing t i and the i-1-th particle has an average interlayer spacing t i-1 ,t i ≥t i-1 .
  6. 6. The negative electrode tab of claim 5, wherein the ranges of t i and t i-1 are each 0.30-0.40 nm.
  7. 7. The negative electrode tab of claim 1, wherein the total thickness L of the multi-layer negative electrode active layer ranges from 30 to 150 μm.
  8. 8. The negative electrode tab of claim 1, wherein the total compacted density ρ of the multi-layer negative electrode active layer is in the range of 1.2-2.2 g/cm 3 .
  9. 9. The negative electrode tab of claim 1, wherein the i-th negative electrode active layer and the i-1-th negative electrode active layer have a degree of orientation of OI i and OI i-1 , respectively, the OI i and OI i-1 are both in the range of 2 to 30, and OI i ＜OI i-1 .
  10. 10. The negative electrode tab according to claim 1, wherein the i-th negative electrode active material and/or i-1 th negative electrode active material comprises one or more of a graphite material, an amorphous carbon material, a graphene material, a carbon fiber material, a silicon carbon material, a silicon oxygen material, a lithium titanate material, a tin-based material, an alloy material.
  11. 11. The anode tab of claim 1, wherein the ratio of the mass of binder in the i-th anode active layer to the total mass of the i-th anode active layer is b i and the ratio of the mass of binder in the i-1-th anode active layer to the total mass of the i-1-th anode active layer is b i-1 ,b i ≤b i-1 .
  12. 12. The negative electrode of claim 11, wherein b i and b i-1 are each 1.0% -10.0%, and/or, The binder comprises one or more of carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE) and modified polymers thereof, rubber, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyimide (PI), modified polyimide, polyamide (PAI), polyethyleneimine (PEI), polyurethane (PU), polymethyl methacrylate (PMMA), polypropylene, modified polypropylene, polyacrylic acid (PAA), modified polyacrylic acid, polyvinyl alcohol (PVA), modified polyvinyl alcohol, polyvinyl butyral, modified polyvinyl butyral, polyacrylonitrile (PAN) and modified polyacrylonitrile.
  13. 13. The anode tab of claim 1, wherein the ratio of the mass of the conductive agent in the i-th anode active layer to the total mass of the i-th anode active layer is e i and the ratio of the mass of the conductive agent in the i-1-th anode active layer to the total mass of the i-1-th anode active layer is e i-1 ,e i ≥e i-1 .
  14. 14. The negative electrode of claim 13, wherein the e i and e i-1 are each in the range of 0.1% -4.0%, and/or, The conductive agent comprises one or more of conductive nanofibers, conductive nanotubes, carbon nanofibers, graphene, lamellar graphite micro-plates, carbon black, graphene microspheres, a three-dimensional conductive metal organic framework and porous spherical carbon.
  15. 15. A method for preparing a negative electrode sheet according to any one of claims 1 to 14, comprising the steps of: Mixing the negative electrode active materials, the binder and the conductive agent of each negative electrode active layer, and respectively adding the mixture into water for dispersion to respectively obtain the 1 st negative electrode slurry, the 2 nd negative electrode slurry, the nth negative electrode slurry; Sequentially coating the 1 st negative electrode slurry, the 2 nd negative electrode slurry, & gtand the n-th negative electrode slurry on at least one side of the negative electrode current collector, and drying and rolling to obtain the negative electrode plate.
  16. 16. A lithium ion battery comprising a negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet according to any one of claims 1 to 14, or the negative electrode sheet is prepared by the preparation method of the negative electrode sheet according to claim 15.

Description

Negative electrode piece, preparation method thereof and lithium ion battery Technical Field The invention belongs to the technical field of secondary batteries, and particularly relates to a negative electrode plate, a preparation method thereof and a lithium ion battery. Background With the rapid development of new energy technology, lithium ion batteries are used as core components of energy storage systems, and are facing higher and higher requirements in terms of energy density, power performance, cycle life and the like. Particularly in the fields of electric automobiles, portable electronic devices and renewable energy storage, the performance of batteries directly affects the efficiency and the use experience of the devices. However, the existing conventional thick electrode designs, while improving energy density, also expose some technical challenges, especially in terms of energy density and cycle performance of the battery. The main advantage of the conventional thick electrode is that the energy density of the battery can be improved by increasing the amount of active material. But this design also presents a number of challenges. First, the surface density of the thick electrode is too high, which results in a longer ion transport path and a limited ion transport rate inside the battery. The diffusion rate of lithium ions in the electrode decreases, thereby increasing the resistance to ion transport. This not only reduces the charge and discharge efficiency of the battery, but also causes the polarization effect of the battery to be increased during high-rate charge and discharge, and the voltage to be reduced, thereby limiting the high power output and the rapid charge and discharge capability of the battery. Particularly, under the high-load use condition of the battery, the performance of the battery can be obviously reduced, the polarization phenomenon shortens the cycle life of the battery, and the capacity fading is accelerated. Furthermore, the homogeneous design of a single coating often has difficulty meeting multiple requirements of the battery, such as high conductivity, strong adhesion, and rapid ion migration, at the same time. In the traditional thick electrode, the balance of conductivity and binding force is difficult to realize because of the single material structure, so that the electrode material of the battery cannot fully play a role in high-rate charge and discharge. More importantly, the porosity of the thick electrode is low, the infiltration capacity of the electrolyte is insufficient, and the electrolyte cannot uniformly infiltrate into the deep region of the electrode. This may result in insufficient utilization of active materials inside the battery, thereby reducing the energy density and cycle performance of the battery. Disclosure of Invention Aiming at the problems that the material homogenization design of a single coating of the negative electrode plate of the existing lithium ion battery is difficult to meet multiple requirements of high conductivity, high bonding strength, rapid ion migration and the like, and particularly the problems that electrolyte is not soaked uniformly in a thick electrode, the utilization rate of active substances is low and the like are easy to occur, and the energy density and the cycle performance of the battery are affected, the invention provides the negative electrode plate, a preparation method thereof and the lithium ion battery. The technical scheme adopted by the invention for solving the technical problems is as follows: The invention provides a negative electrode plate, which comprises a negative electrode current collector and a plurality of negative electrode active layers arranged on at least one surface of the negative electrode current collector, wherein the plurality of negative electrode active layers are sequentially 1 st, 2 nd and the third, n is more than or equal to 2, and the direction from the 1 st negative electrode active layer to the n negative electrode active layer is a direction away from the negative electrode current collector; the i-th anode active layer and the i-1-th anode active layer satisfy the following relational expression ① or ②: ①Ci＞Ci-1; ②Ci=Ci-1 And SOC i＞SOCi-1; Wherein, C i is the minimum lithium-out multiplying power of the ith negative electrode active layer, C i-1 is the minimum lithium-out multiplying power of the ith-1 negative electrode active layer, SOC i is the critical lithium-out state of the ith negative electrode active layer, and SOC i-1 is the critical lithium-out state of the ith-1 negative electrode active layer. Further, the test calculation steps of C i and SOC i are: S1, preparing an ith anode active layer by independently adopting the ith anode active material, and preparing a button cell; S2, carrying out a charging test on the button cell under the multiplying power of 0.1C to obtain the charging capacity of the button cell, and recording the charging capacity as