High-Nickel Cathode Composition Balancing Energy Density and Cycle Life
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Solution Overview
Problem
Current new energy vehicles suffer from low range and poor lifespan due to the limitations of existing high-nickel positive electrode materials, which have high watt-hour costs and are prone to material cracking under high-voltage conditions.
Innovation Solution
A high-nickel positive electrode material with small and large particles of specific structures, where the small particles have a monocrystalline or monocrystalline-like structure and the large particles are formed by agglomeration of primary particles, with a controlled mass percentage of small particles to reduce stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional high-nickel materials are used to achieve high capacity, then the energy density is improved, but the material is prone to cracking during cycling leading to shorter cycle life
Solution Approach 1:
The positive electrode active material is segmented into two distinct particle size ranges: small particles (Dv50: 2-5 μm) and large particles (Dv50: 5-25 μm). This segmentation allows the small particles to accommodate stress during lithium deintercalation/intercalation, preventing cracking, while the large particles provide high capacity. The segmented structure resolves the contradiction by enabling both high energy density and long cycle life simultaneously.
Solution Approach 2:
Different regions of the particle size distribution are assigned different functions: small particles (higher mass percentage) are optimized for structural stability and stress accommodation, while large particles are optimized for capacity. This local quality differentiation allows the material to simultaneously achieve high energy density from large particles and long cycle life from small particles, resolving the technical contradiction.
2Quantity of substance
If high-nickel materials are used to increase capacity, then the energy storage capability is improved, but the oxidation activity increases causing intensive chemical reactions with electrolyte and gas generation
Solution Approach 1:
The particle size segmentation creates a bimodal distribution where small particles (Dv50: 2-5 μm) with higher surface area to volume ratio are more resistant to oxidation and less prone to intensive chemical reactions with the electrolyte. This segmentation reduces gas generation while maintaining high capacity from the large particles, resolving the contradiction between capacity and harmful side reactions.
3Volume of stationary object
If the percentage of large particles is increased to improve compacted density, then the volumetric capacity is improved, but the stress from lattice contraction and expansion increases causing material cracking
Solution Approach 1:
The invention assigns different mass percentages to different particle size ranges based on their functional roles: small particles (Dv50: 2-5 μm) constitute 50-90% of the mass for structural stability, while large particles (Dv50: 5-25 μm) constitute 10-50% for compacted density. This local quality optimization resolves the contradiction by ensuring that the majority of particles are small and structurally stable, while a minority of large particles provide high density without causing excessive stress.
Data Source
AI summary
This application provides a positive electrode active material including particles A and particles B, where the particles A have a monocrystalline or monocrystalline-like structure, and the particles B are secondary particles including a plurality of primary particles. Dv50 of the particles A is less than Dv50 of the particles B, and a mass percentage of the particles A is greater than or equal to a mass percentage of the particles B, where Dv50 denotes a particle size corresponding to a cumulative volume distribution percentage of a material reaching 50%.