Porous Polycrystalline Cathode Material to Reduce Particle Cracking
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Solution Overview
Problem
Lithium nickel cobalt manganese oxide materials used in lithium-ion batteries have high energy density but poor long-term cycle performance and safety performance due to poor stability of the bulk phase and surface structure, leading to particle cracking and irreversible phase changes during the electrode plate processing.
Innovation Solution
A positive electrode material with a polycrystalline particle structure having a porosity of 1% to 15% and a pore edge distance of 5nm to 100nm, combined with a molten salt method to regulate thermal field distribution and form uniform pores, enhancing particle toughness and reducing stress accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel lithium nickel cobalt manganese oxide material is used to achieve high energy density, then the energy density is improved, but the long-term cycle performance and safety performance deteriorate due to poor stability of bulk phase and surface structure
Solution Approach 1:
The patent introduces a porous structure within polycrystalline particles with controlled porosity (1-15%) and pore edge distances (5-100nm). This porous structure acts as a buffer to accommodate volume changes during lithium insertion/extraction, reducing mechanical stress and preventing particle cracking, thereby improving long-term cycle performance and safety while maintaining high energy density
Solution Approach 2:
The patent creates a composite structure consisting of multiple primary particles (200-800nm) aggregated into polycrystalline particles. This composite architecture combines the high capacity benefits of fine primary particles with the structural stability of larger polycrystalline aggregates, resolving the contradiction between energy density and reliability
2Strength
If polycrystalline particle structure with porosity of 1% to 15% and pore edge distance of 5nm to 100nm is designed, then particle toughness and mechanical impact resistance are improved, but the manufacturing complexity increases
Solution Approach 1:
The patent optimizes specific parameters including porosity (1-15%), pore edge distance (5-100nm), primary particle size (200-800nm), and polycrystalline particle size (9-17μm). By controlling these parameters within specific ranges, the material achieves improved toughness and mechanical resistance while maintaining manufacturability through standardized production processes
3Manufacturing precision
If molten salt method is used to regulate thermal field distribution and form uniform pores, then the manufacturing precision is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent uses molten salt as an intermediary substance during the sintering process. The molten salt facilitates uniform thermal field distribution and promotes the formation of uniformly distributed pores within polycrystalline particles. After sintering, the molten salt is removed, leaving behind the desired porous structure. This intermediary approach achieves high manufacturing precision while keeping the process manageable
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The material design reduces cracking ratios and initial stress, improves mechanical impact resistance, and enhances long-term cycle and safety performance by maintaining structural stability and reducing particle collapse.
Implementation Method 1
combined with a molten salt method to regulate thermal field distribution and form uniform pores
Data Source
Figure 1~2
AI summary
The present application provides a positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery. The positive electrode material comprises a first lithium nickel oxide material, the first lithium nickel oxide material comprises a polycrystalline particle, and the porosity inside the polycrystalline particle is denoted as d, 2%≤d≤15%; in any CP cross-section of the polycrystalline particle, the distance between two adjacent pore edges inside the polycrystalline particle is 10nm to 100nm. Thus, the cracking ratio of the positive electrode material during the processing of the electrode plate can be reduced, and the initial stress and the stress accumulation of the new surface generated by the cracking during the cycle process can be significantly reduced, and the particle toughness and particle strength are improved. Meanwhile, sufficient support can be provided for the rigid structure of the material, and the collapse and crushing of the material particles can be reduced. Therefore, the stability of the bulk phase and the surface is improved at the material level, and the long-term cycle performance and safety performance of the material are improved.