Non-Aqueous Electrolyte Battery Cathode Composition for Cycle Stability
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Solution Overview
Problem
Lithium transition metal oxides with high Ni content used in positive electrode active materials for non-aqueous electrolyte secondary batteries experience deformation of the layered crystal structure during repeated charge/discharge cycles, leading to reduced battery capacity and suboptimal charge/discharge cycle characteristics.
Innovation Solution
Incorporating a predetermined amount of Ca into the lithium transition metal oxide, along with Ni and Al, and adjusting the proportion of metal elements excluding Li in the Li layer, stabilizes the layered structure and enhances the charge/discharge cycle characteristics. Additionally, forming a Ca film on the surface of the negative electrode active material improves the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Ni content (80-95 mol%) is used in lithium transition metal oxide to increase battery capacity, then energy density is improved, but layered crystal structure deforms during repeated charge/discharge cycles
Solution Approach 1:
The patent applies local quality by introducing Ca and Al elements at specific locations within the lithium transition metal oxide structure. Ca is incorporated into the Li layer at controlled proportions (0.6-2.0 mol%) to locally stabilize the structure without compromising the high Ni content (80-95 mol%) needed for high capacity. This localized modification allows the bulk material to maintain high energy density while specific regions provide structural stability during charge/discharge cycles.
Solution Approach 2:
The patent creates a composite material system by combining Li-Ni-Co-O base structure with Ca and Al dopants. The composite consists of high Ni content lithium transition metal oxide (providing high capacity) combined with Ca elements in the Li layer (providing structural stabilization) and Al elements (providing additional stability). This composite approach allows simultaneous achievement of high battery capacity and improved cycle characteristics.
2Quantity of substance
If high Ni content is used to extract more Li during charge, then battery capacity increases, but charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the lithium transition metal oxide. The Ni content is set within 80-95 mol% to ensure high capacity, while Ca content is controlled at more than 0 mol% and 3 mol% or less, and Al content at more than 0 mol% and 8 mol% or less. The proportion of metal elements excluding Li in the Li layer is specifically adjusted to 0.6-2.0 mol%. These optimized parameters enable both high battery capacity and improved charge/discharge cycle characteristics.
3Reliability
If Ca is added to stabilize the layered structure, then cycle characteristics improve, but battery capacity may be reduced
Solution Approach 1:
The patent applies partial action by incorporating Ca at controlled, limited proportions rather than in large amounts. The Ca content is maintained at more than 0 mol% and 3 mol% or less, with the proportion of metal elements excluding Li in the Li layer at 0.6-2.0 mol%. This partial incorporation is sufficient to stabilize the layered structure and improve cycle characteristics while minimizing the impact on battery capacity, thus avoiding the trade-off between stability and capacity.
Data Source
AI summary
In this non-aqueous electrolyte secondary battery: a positive electrode active material contains a lithium transition metal oxide that has a layered structure including a Li layer and that contains at least prescribed amounts of Ni, Ca, and Al; the proportion of metal elements, excluding Li, in the Li layer is 0.6-2.0 mol % with respect to the total number of moles of metal elements, excluding Li, contained in the lithium transition total oxide; a negative electrode active material has a coating containing Ca on the surface thereof; and the contained amount of Ca in the coating is not less than 15 mass ppm but less than 80 mass ppm with respect to the total mass of the positive electrode material.