Lithium Composite Oxide Coating for Battery Cycle Stability
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Solution Overview
Problem
Existing battery technologies face challenges in maintaining high capacity retention and cycle stability due to electrolyte decomposition and side reactions at high potentials, leading to resistance layer formation and gas separation, which degrade battery performance.
Innovation Solution
A positive electrode active material comprising a lithium composite oxide with a multiphase mixture of crystal structures belonging to space groups Fm-3m and others, such as Fd-3m, R-3m, or C2/m, combined with a covering material of low electron conductivity to suppress electron transfer and side reactions, enhancing Li diffusion paths and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium composite oxide with high capacity is used, then battery capacity is improved, but electrolyte decomposition and side reactions occur at high potentials, leading to resistance layer formation and gas separation
Solution Approach 1:
A covering material layer is introduced as an intermediary between the lithium composite oxide and the electrolyte. This covering material suppresses electron transfer and prevents direct contact between the high-potential lithium composite oxide and the electrolyte, thereby preventing electrolyte decomposition and side reactions while maintaining high battery capacity
Solution Approach 2:
The electron conductivity of the covering material is controlled to be 10^-6 S/m or less, creating an electron-blocking barrier. This parameter change in electron conductivity prevents electron transfer to the electrolyte while allowing lithium ion diffusion, resolving the contradiction between high capacity and cycle stability
2Reliability
If the covering material has low electron conductivity to suppress side reactions, then cycle stability is improved, but Li diffusion may be hindered
Solution Approach 1:
The covering material is designed with specific local properties: extremely low electron conductivity (10^-6 S/m or less) to block electrons, while maintaining lithium ion permeability. This local quality differentiation allows the covering material to simultaneously suppress side reactions and enable Li diffusion by having different conductivity characteristics for different charge carriers
Solution Approach 2:
A composite structure is created combining the lithium composite oxide core with a covering material shell. This composite material design allows the inner core to provide high capacity while the outer shell provides protection against electrolyte decomposition, and the specific composition enables selective permeability to lithium ions
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 provides batteries with improved capacity retention and cycle stability, maintaining high capacity even after multiple charge-discharge cycles by enhancing Li diffusibility and suppressing side reactions, resulting in better electrochemical performance.
Implementation Method 1
The covering material has an electron conductivity of 10^-6 S/m or less
Implementation Method 2
enhancing Li diffusion paths and stability
Implementation Method 3
The ratio I(18°-20°)/I(43°-46°) of a first integrated intensity I(18°-20°) of a first maximum peak present at a first diffraction angle 2θ of 18° or more and 20° or less to a second integrated intensity I(43°-46°) of a second maximum peak present at a second diffraction angle 2θ of 43° or more and 46° or less in an XRD pattern
Data Source
AI summary
A positive electrode active material includes a lithium composite oxide and a covering material that covers a surface of the lithium composite oxide. The covering material has an electron conductivity of 106 S/m or less. The lithium composite oxide is a multiphase mixture including a first phase having a first crystal structure that belongs to a space group Fm-3m and a second phase having a second crystal structure that belongs to a space group other than a space group Fm-3m. The ratio I(18°-20°)/I(43°-46°) of a first integrated intensity I(18°-20°) of a first maximum peak present at a first diffraction angle 2θ of 18° or more and 20° or less to a second integrated intensity I(43°-46°) of a second maximum peak present at a second diffraction angle 2θ of 43° or more and 46° or less in an XRD pattern of the lithium composite oxide satisfies 0.05≤I(18°-20°)/I(43°-46°)≤0.90.