Lithium Composite Oxide with Low Conductivity Covering Material
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Solution Overview
Problem
Existing lithium-ion battery positive electrode active materials face challenges in maintaining capacity retention and cycle stability due to structural instability and side reactions at high potentials, particularly when cation mixing is insufficient or excessive, leading to reduced diffusibility and increased resistance.
Innovation Solution
A lithium composite oxide with a crystal structure belonging to space group C2/m, incorporating elements like fluorine, chlorine, nitrogen, or sulfur, and a covering material with low electron conductivity, which stabilizes the structure and suppresses side reactions by controlling cation mixing and electron transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium composite oxide with high capacity is used, then the battery capacity increases, but the cycle stability and capacity retention deteriorate due to structural instability and side reactions at high potentials
Solution Approach 1:
A covering material layer is introduced as an intermediary between the lithium composite oxide and the electrolyte. This covering material suppresses side reactions at the interface while maintaining ion transport, thereby improving cycle stability without significantly reducing battery capacity
Solution Approach 2:
The positive electrode active material is designed as a composite structure combining lithium composite oxide particles with a covering material layer. This composite approach allows the core material to provide high capacity while the outer layer provides structural stability and suppresses degradation
2Stability of the object's composition
If the cation mixing in the lithium composite oxide is increased to improve structural stability, then the capacity retention improves, but the diffusibility of lithium ions decreases leading to increased resistance
Solution Approach 1:
The covering material layer is designed with specific local properties (electron conductivity of 10^-6 S/m or less) that differ from the core lithium composite oxide. This local quality difference allows the covering layer to suppress side reactions while the core material maintains its electrochemical activity and lithium ion diffusibility
3Reliability
If a covering material with low electron conductivity is applied to suppress side reactions, then the cycle characteristics improve, but the initial capacity may be reduced due to surface coverage
Solution Approach 1:
The electron conductivity parameter of the covering material is specifically controlled to be 10^-6 S/m or less, which is low enough to suppress side reactions but not so low as to completely block electrochemical reactions. This optimized parameter allows the covering material to improve cycle characteristics while minimizing impact on initial capacity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances capacity retention and cycle stability by maintaining structural integrity and reducing side reactions, resulting in higher capacity and longer battery life even at high potentials.
Implementation Method 1
The covering material has an electron conductivity of 10^-6 S/m or less
Data Source
AI summary
A positive electrode active material contains a lithium composite oxide and a covering material. The lithium composite oxide contains at least one element selected from the group consisting of fluorine, chlorine, nitrogen, and sulfur. The lithium composite oxide has a crystal structure that belongs to space group C2/m. The ratio I(003)/I(104) of a first integrated intensity I(003) of a first peak corresponding to a (003) plane to a second integrated intensity I(104) of a second peak corresponding to a (104) plane in an XRD pattern of the lithium composite oxide satisfies 0.05≤I(003)/I(104)≤0.90. The covering material has an electron conductivity of 106 S/m or less.