Cathode Particle Composition for High-Energy Battery Cycle Life
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with high energy density suffer from particle cracking of the positive electrode active material during charging and discharging, leading to poor charge-discharge cycle characteristics.
Innovation Solution
The use of lithium-transition metal composite oxides with specific particle size distributions and surface compositions, where smaller particles have a higher titanium content, combined with larger particles to enhance stress relaxation and inhibit metal elution, resulting in improved cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high Ni content lithium-transition metal composite oxide is used to achieve high energy density, then energy density is improved, but particle cracking occurs during charging and discharging leading to poor cycle characteristics
Solution Approach 1:
The patent applies local quality by creating particles with non-uniform Ni distribution - the core has high Ni content (0.7-0.95) for high energy density, while the surface has lower Ni content (0.5-0.8) for improved stability. This gradient structure allows different regions to serve different functions, resolving the contradiction between energy density and cycle life.
Solution Approach 2:
The patent uses composite materials by combining lithium-transition metal composite oxide particles with a coating layer containing elements such as Al, Ti, Zr, or B on the particle surface. This composite structure provides both the high capacity of high-Ni materials and the protective stability of the coating layer, improving charge-discharge cycle characteristics while maintaining energy density.
2Quantity of substance
If high Ni content positive electrode active material is used, then battery capacity is improved, but metal elution increases leading to capacity degradation
Solution Approach 1:
The patent reduces metal elution by creating a surface region with lower Ni content and higher stability compared to the high-Ni core. This local quality modification at the particle surface minimizes the interaction between high-Ni material and electrolyte, thereby reducing metal elution while preserving the high capacity benefits of the bulk high-Ni structure.
Solution Approach 2:
The patent employs composite materials by forming a protective coating layer on the high-Ni particles. This coating layer acts as a barrier that prevents direct contact between the high-Ni active material and the electrolyte, significantly reducing metal elution while allowing lithium ion transport, thus maintaining high battery capacity over extended cycles.
3Device complexity
If uniform particle size is used for simplicity, then manufacturing complexity is reduced, but stress distribution during charging and discharging becomes uneven leading to particle cracking
Solution Approach 1:
The patent optimizes the particle size distribution by controlling the D10, D50, and D90 parameters within specific ranges and establishing their relationships (D10≥0.5μm, D50≥1μm, D90≤5μm, and D10/D50≤0.8). This parameter optimization ensures uniform stress distribution during lithium insertion/extraction, preventing particle cracking while maintaining manufacturability through controlled synthesis parameters.
Data Source
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AI summary
A nonaqueous electrolyte secondary battery according to the present invention comprises a positive electrode that contains, as positive electrode active materials: a lithium transition metal composite oxide (A) that is configured of secondary particles, in each of which primary particles having an average particle diameter of 0.5 µm or more aggregate, or is configured of substantially one kind of particles, while having a volume-based D50 of from 0.6 µm to 3 µm; and a lithium transition metal composite oxide (B) that is configured of secondary particles, in each of which primary particles having an average particle diameter of 0.3 µm or less aggregate, while having a volume-based D50 of from 6 µm to 25 µm. With respect to the lithium transition metal composite oxide (B), the molar fraction (B2) of Ti with respect to the total number of moles of metal elements other than Li on the surfaces of second particles having a particle diameter smaller than the volume-based D30 is higher than the molar fraction (B1) of Ti with respect to the total number of moles of metal elements other than Li on the surfaces of first particles having a particle diameter larger than the volume-based D70.