Cathode Composition for High-Ni Battery Capacity and Crystal Stability
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Solution Overview
Problem
Lithium-transition metal composite oxides with high Ni content have unstable crystalline structures, leading to cation mixing and reduced battery capacity, despite efforts to stabilize the structure by increasing Al content.
Innovation Solution
A non-aqueous electrolyte secondary battery design that includes a positive electrode with a lithium-transition metal composite oxide represented by LiaNibCo(1-b-c)AlcOd, where 0.9<a≤1.2, 0.88≤b≤0.96, 0.04≤c<0.12, and 1.9≤d≤2.1, along with 0.1 to 1.0 mass % of lithium carbonate and 0.05 to 0.20 mol % of tungsten on the surface of the primary particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Ni content is increased to achieve high capacity, then the battery capacity increases, but the crystalline structure becomes unstable causing cation mixing
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high Ni content (0.85-0.95) for high capacity, while the outer shell region contains lower Ni content (0.70-0.85) and higher Al content (0.05-0.20) for structural stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and structural stability.
Solution Approach 2:
The patent uses composite materials by combining multiple transition metal elements (Ni, Co, Al) in a layered structure with specific composition gradients. The composite oxide Li[Ni1-x-yMxAlz]O2 integrates the high capacity contribution from Ni with the structural stabilization from Al and Co, creating a composite material that balances both requirements.
2Stability of the object's composition
If the amount of Al is increased to stabilize the crystalline structure, then the crystalline structure stability improves, but the battery capacity decreases
Solution Approach 1:
The patent applies local quality by concentrating Al in the outer shell region (0.05-0.20 mol ratio) where it provides structural stabilization, while keeping the core region rich in Ni (0.85-0.95) for high capacity. This localized distribution allows Al to stabilize the structure without significantly reducing overall capacity.
Solution Approach 2:
The patent uses parameter changes by optimizing the Al content within a specific range (0.05-0.20 mol ratio) and controlling the Ni content gradient from core to shell. By precisely adjusting these compositional parameters and their spatial distribution, the patent achieves both structural stability and high capacity.
Data Source
AI summary
In a non-aqueous electrolyte secondary battery that is one example of the embodiment, a positive electrode mix layer comprises a positive electrode active material comprising a lithium transition metal composite oxide represented by general formula: LiaNibCo(1-b-c)AlcOd (0.9<a≤1.2, 0.88≤b≤0.96, 0.04≤c≤0.12, 1.9≤d≤2.1) and lithium carbonate in an amount of 0.1 to 1.0% by mass relative to the mass of the positive electrode active material. The lithium transition metal composite oxide has the form of secondary particles formed by the aggregation of primary particles, wherein tungsten is present, on the surface of each of the primary particles, in an amount of 0.05 to 0.20 mol % relative to the total molar amount of non-Li-metal elements contained in the positive electrode active material.