Positive Electrode Mixture Layer for Battery Capacity and Cycle Life
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries require improvement in charge-discharge cycle characteristics for enhanced performance, particularly in on-board and power storage applications.
Innovation Solution
A positive electrode comprising a mixture layer with a first lithium-transition metal composite oxide (LixNi1−y−zCoyMzO2) and a second lithium-transition metal composite oxide (LiaNi2−a−bMebO2), along with carbon nanotubes, to improve cycle characteristics by protecting the surface of the first composite oxide and facilitating effective contact between particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used, then the battery can operate, but the charge-discharge cycle characteristics are insufficient
Solution Approach 1:
The patent uses a composite oxide material with the general formula LixNi1-y-zCoyMzO2 where M represents multiple elements (Mn, Ti, Y, Nb, Mo, W) combined in specific ratios. This composite structure integrates the advantages of different metals: Ni provides high capacity, Co enhances conductivity, Mn improves stability, and other elements address specific degradation issues. The synergistic combination resolves the contradiction by achieving both reliability (cycle characteristics) and productivity (battery performance) simultaneously.
Solution Approach 2:
The patent optimizes the local composition by controlling the content of each metal element within specific ranges (e.g., 0.01≤y≤0.2, 0.01≤z≤0.2, 0.01≤a≤0.5 for Mn content). This local quality control ensures that the positive electrode active material has optimal properties in different regions of its composition space, achieving both good cycle characteristics and high battery performance without the trade-off present in conventional uniform materials.
2Quantity of substance
If the positive electrode composition is optimized for high capacity, then battery capacity increases, but cycle stability deteriorates
Solution Approach 1:
The patent systematically changes multiple parameters simultaneously: the Li content (x), Ni content (y), Co content (z), and the addition of various metal elements (Mn, Ti, Y, Nb, Mo, W) within optimized ranges. By coordinating these parameter changes, the patent achieves a composition that delivers high battery capacity while maintaining excellent cycle stability, resolving the contradiction between quantity (capacity) and stability (cycle life).
Solution Approach 2:
The patent introduces intermediary elements (Mn, Ti, Y, Nb, Mo, W) that mediate between the high-capacity Ni component and the stability requirements. These intermediary elements act as buffers that prevent the degradation issues associated with high Ni content while preserving the high capacity benefits, thus resolving the contradiction between battery capacity and cycle stability.
Data Source
AI summary
The positive electrode mixture layer of this nonaqueous electrolyte secondary battery positive electrode, which is one exemplary embodiment, contains a first lithium-transition-metal composite oxide represented by general formula LixNi1−y−zCoyMzO2 (in the formula. 0.8≤x≤1.2, 0≤y≤0.2, 0<z≤0.5, and M is at least one metal element excluding Li, Ni, and Co), a second lithium-transition-metal composite oxide represented by general formula LiaNi2−a−bMebO2 (in the formula, 0<a≤0.5, 0≤b≤0.5, and Me is at least one metal element excluding Li and Ni), and a carbon nanotube.