CN-122025550-A - Positive electrode plate, preparation method thereof, lithium ion battery and power utilization device

Abstract

The invention discloses a positive pole piece, a preparation method thereof, a lithium ion battery and an electric device, and belongs to the technical field of new energy materials. According to the invention, by regulating and controlling the compaction density and the porosity of the positive pole piece, the pole piece is ensured to have excellent volume energy density, a proper ion transmission channel is maintained, particle breakage or electrolyte infiltration difficulty caused by too high compaction is avoided, the complementation of coating rigidity and toughness is realized by adopting the mixed binder of PVDF and PAA, the structural integrity of the pole piece in charge-discharge expansion is ensured, the interfacial impedance increase caused by too high binding force is avoided, the auxiliary nano particles with specific content and size are cooperated, and a protective net with ion conduction and thermal stability is constructed on the premise of not sacrificing the energy density.

Inventors

• WANG KAI
• CHEN FEIFAN

Assignees

• 江苏睿恩新能源科技有限公司

Dates

Publication Date

20260512

Application Date

20260226

Claims (10)

1. 1. The positive electrode plate is characterized by comprising a current collector, an undercoat layer and a positive electrode active material layer coated on the surface of the undercoat layer, wherein the undercoat layer is positioned between the current collector and the positive electrode active material layer, The compaction density of the positive pole piece is 3.3-3.7g/cm 3 ; The porosity of the positive plate is 18-30%.
2. 2. The positive electrode sheet according to claim 1, wherein the peel strength of the positive electrode sheet is 15 to 30N/m.
3. 3. The positive electrode sheet according to claim 1, wherein the positive electrode active material layer comprises a main active material and auxiliary nanoparticles, the main active material is a metal oxide, and the D90 particle diameter, the D50 particle diameter, and the D10 particle diameter of the main active material satisfy 0.85< <1.15。
4. 4. The positive electrode sheet according to claim 3, wherein the auxiliary nano particles are at least one of phosphates, oxides and nitrides, the mass percentage of the auxiliary nano particles is 2-6wt% and the size of the auxiliary nano particles is 220-410nm.
5. 5. The positive electrode sheet according to claim 1, wherein the primer layer comprises a conductive agent and a binder, and the binder in the primer layer is a mixture of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA).
6. 6. The positive electrode sheet according to claim 4, wherein the auxiliary nanoparticle is at least one of aluminum oxide, lithium phosphate, silicon dioxide, titanium dioxide, boron nitride, and aluminum nitride.
7. 7. The positive electrode sheet according to claim 6, wherein the auxiliary nanoparticle is a mixture of aluminum oxide and lithium phosphate.
8. 8. The positive electrode sheet according to claim 3, wherein the metal oxide is at least one of LiNi x Co y Mn z O 2 、LiNi x Co y Al z O 2 、LiCoO 2 、LiFePO 4 , wherein x is not less than 0.3 and x+y+z=1.
9. 9. A lithium ion battery characterized in that the lithium ion battery comprises the positive electrode sheet according to any one of claims 1-8.
10. 10. An electric device characterized by comprising the lithium ion battery as claimed in claim 9.

Description

Positive electrode plate, preparation method thereof, lithium ion battery and power utilization device Technical Field The invention relates to the technical field of new energy materials, in particular to a positive pole piece, a preparation method thereof, a lithium ion battery and an electric device. Background With the development of electric vehicles and high specific energy storage systems, high nickel ternary cathode materials (such as NCM 811) are widely used due to their high energy density. However, under mechanical abuse conditions such as needling, extrusion, and internal short-circuiting, the high nickel positive electrode system is very prone to cause low-impedance internal short-circuiting (aluminum current collector-negative electrode/aluminum current collector-copper foil failure mode) due to exposure of the positive current collector aluminum foil, so that instantaneous heavy current discharge and severe joule heat release are caused, and thermal runaway and even combustion explosion are triggered. Although attempts have been made to improve thermal stability by means of surface coating, electrolyte additives, etc., these methods have difficulty in fundamentally solving the problem of aluminum foil exposure caused by mechanical failure. In addition, the insufficient interfacial adhesion between the aluminum current collector and the positive electrode active layer is one of the key factors causing the stripping of the active layer, and in the traditional direct coating process, the binder polyvinylidene fluoride (PVDF) is unevenly distributed on the surface of the current collector, so that interfacial weak points are easily formed, and interlayer separation under mechanical damage is accelerated. Disclosure of Invention The invention mainly aims to provide a positive electrode plate, a preparation method thereof and a lithium ion battery, and the invention introduces a conductive bottom coating between an aluminum current collector and an active layer, and introduces specific auxiliary nano particles in the active layer, meanwhile, the compaction density and peel strength window of the pole piece are strictly limited, the coordination of mechanical reinforcement and interface bonding regulation is realized, the aluminum foil exposure in the needling process is effectively avoided, and the safety of the battery is obviously improved. In order to achieve the aim, the invention provides a positive electrode plate, which comprises a current collector, an undercoat layer and a positive electrode active material layer coated on the surface of the undercoat layer, wherein the undercoat layer is positioned between the current collector and the positive electrode active material layer, The compaction density of the positive pole piece is 3.3-3.7g/cm 3; The porosity of the positive plate is 18-30%. On the basis of the technical scheme, the stripping strength of the positive electrode plate is preferably 15-30N/m. On the basis of the technical proposal, the positive electrode active material layer is preferably composed of a main active material and auxiliary nano particles, the main active material is metal oxide, and the D90 particle diameter, the D50 particle diameter and the D10 particle diameter of the main active material satisfy 0.85<<1.15。 On the basis of the technical scheme, preferably, the auxiliary nano particles are at least one of phosphates, oxides and nitrides, the mass percentage of the auxiliary nano particles is 2-6wt%, and the size of the auxiliary nano particles is 220-410nm. On the basis of the technical scheme, the primer layer comprises a conductive agent and a binder, wherein the binder in the primer layer is a mixture of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA). On the basis of the technical scheme, preferably, the auxiliary nano particles are at least one of aluminum oxide, lithium phosphate, silicon dioxide, titanium dioxide, boron nitride and aluminum nitride. On the basis of the above technical solution, preferably, the auxiliary nanoparticle is a mixture of aluminum oxide and lithium phosphate. On the basis of the technical scheme, preferably, the metal oxide is at least one of LiNixCoyMnzO2、LiNixCoyAlzO2、LiCoO2、LiFePO4, wherein x is more than or equal to 0.3, and x+y+z=1. The invention also provides a lithium ion battery comprising the positive electrode sheet according to any one of claims 1-8. The invention also provides an electric device comprising the lithium ion battery. Compared with the prior art, the invention has the beneficial effects that: 1) The invention provides a positive electrode plate, a preparation method thereof and a lithium ion battery, wherein an auxiliary nano material with mechanical reinforcing and bonding regulation functions is introduced into high-nickel positive electrode slurry, so that the microstructure and mechanical property of the positive electrode plate can be obviously regulated and controlled, the spatial distr