Nonaqueous Battery Cathode Composition for Crack-Resistant High-Ni Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-transition metal composite oxide batteries with high Ni content suffer from particle cracking during charging and discharging, leading to reduced battery capacity and poor charge-discharge cycle characteristics.
Innovation Solution
A non-aqueous electrolyte secondary battery design using a combination of lithium-transition metal composite oxides with specific particle sizes and surface compositions, where smaller particles have a higher titanium content to inhibit metal elution and stress relaxation, enhancing energy density and 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 as positive electrode active material, then energy density is improved, but particle cracking occurs during charging and discharging leading to poor charge-discharge cycle characteristics
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high Ni content (0.7-0.95 mol fraction) for high energy density, while the outer shell region contains lower Ni content (0.5-0.7 mol fraction) to provide structural stability and resistance to particle cracking. This spatial variation in composition allows different regions to fulfill different functions: the core provides energy storage capacity while the shell provides mechanical strength and crack resistance, thereby resolving the contradiction between energy density and cycle characteristics.
2Reliability
If smaller primary particles are used in composite oxide (B), then surface area increases improving reactivity, but particle strength decreases leading to easier cracking
Solution Approach 1:
The patent merges multiple primary particles (0.3 μm or smaller) into a secondary particle structure with median diameter of 6-25 μm. This aggregation maintains the high surface area-to-volume ratio of small particles for good electrolyte contact and reactivity, while the collective structure of the aggregated particles provides enhanced mechanical strength and resistance to cracking during charge-discharge cycles. The secondary particle structure thus combines the advantages of both small and large particles.
Data Source
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.