Cathode Composite Oxide Composition for Capacity and Endurance
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Solution Overview
Problem
Lithium-excess composite oxides for non-aqueous electrolyte secondary batteries face issues with transition metal elution, which can be suppressed by adding F, but this increases resistance and reduces capacity, while adding Al stabilizes the crystal structure but does not achieve high capacity expectations.
Innovation Solution
A positive electrode active material comprising a lithium-transition metal composite oxide with a specific composition formula Li x Mn y Ni z Al a M b O 2-c F c, where M includes elements like Ti, Co, and Nb, along with Al, to enhance capacity and endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If F is added to lithium-excess composite oxide to suppress transition metal elution, then endurance is improved, but resistance is increased and capacity is reduced
Solution Approach 1:
The patent uses a composite oxide material containing Li, Mn, Ni, Al, and F elements in specific proportions. This composite structure allows the material to simultaneously achieve high capacity (through lithium-excess composition) and good endurance (through F-induced stability), resolving the contradiction between capacity and durability that plagues single-component materials.
Solution Approach 2:
The patent optimizes the compositional parameters (molar ratios of Li, Mn, Ni, Al, and F) to achieve the desired balance. By carefully controlling the concentration of F and the lithium-excess ratio, the material achieves both high capacity and suppressed transition metal elution, transforming the trade-off into a synergistic relationship.
2Stability of the object's composition
If Al is added to lithium-excess composite oxide to stabilize crystal structure, then structure stability is improved, but capacity does not reach high capacity expectations
Solution Approach 1:
The patent combines Al with F and lithium-excess composition to create a multi-component system where each element contributes its beneficial effect. Al provides structural stability, F suppresses transition metal elution and maintains low resistance, while the lithium-excess composition ensures high capacity, achieving synergistic effects that none of the components can achieve alone.
Solution Approach 2:
The composite oxide material performs multiple functions simultaneously: structural stabilization (through Al), elution suppression (through F), resistance control (through F), and capacity enhancement (through lithium-excess composition). This multi-functionality resolves the limitation of Al-only addition by incorporating additional elements that address other performance aspects.
3Quantity of substance
If lithium-excess composite oxide is used to achieve high capacity, then capacity is improved, but transition metal elution increases
Solution Approach 1:
The F element acts as an intermediary that mediates between the lithium-excess composition and the transition metal atoms. It forms strong bonds with transition metals, preventing their elution while allowing the lithium-excess structure to maintain its high capacity characteristics. This intermediary effect resolves the contradiction between high capacity and metal stability.
Solution Approach 2:
The patent creates a composite oxide with specific elemental ratios where the interaction between Li, Mn, Ni, Al, and F produces a stable structure that prevents transition metal elution even at high lithium content. The composite nature of the material allows simultaneous achievement of high capacity and suppressed elution that cannot be achieved with simpler compositions.
Data Source
Figure 1
AI summary
This positive electrode active material for a non-aqueous electrolyte secondary battery contains a lithium transition metal composite oxide represented by the composition formula LixMnyNizAlaMbO2-cFc (in the formula, M represents at least two elements selected from Ti, Co, Si, Sr, Nb, W, Mo, P, Ca, Mg, Sb, Na, B, V, Cr, Fe, Cu, Zn, Ge, Zr, Ru, K, and Bi; 1.0<x≤1.2; 0.4≤y≤0.8; 0≤z≤0.4; 0<a<0.01; 0<b<0.03; 0<c<0.1; and x+y+z+a+b≤2).