Nonaqueous Battery Cathode Surface Treatment for Cycle Stability
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries face challenges in achieving both high initial charge-discharge efficiency and excellent cycle characteristics, particularly due to increased reaction resistance and volume change of the positive electrode active material, leading to cracking and side reactions.
Innovation Solution
Incorporating a sulfonate compound on the surface of the lithium-containing transition metal composite oxide positive electrode active material and applying a pressure of greater than or equal to 8.00 × 10 -2< MPa to the electrode assembly in the stacking direction, which suppresses cracking and side reactions, thereby improving both efficiency and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-containing transition metal composite oxide is used as positive electrode active material, then battery capacity is improved, but reaction resistance increases and cycle characteristics deteriorate
Solution Approach 1:
A sulfonate compound is introduced as an intermediary substance on the surface of the lithium-containing transition metal composite oxide particles. This intermediary layer mediates between the positive electrode active material and the non-aqueous electrolyte, reducing reaction resistance and preventing direct harmful interactions while maintaining high capacity. The sulfonate compound acts as a protective interface that improves cycle characteristics without sacrificing battery capacity.
Solution Approach 2:
The surface properties of the positive electrode active material are modified by controlling the amount of sulfonate compound adhered to the particle surface (0.01-5 mass%). This parameter change in surface composition reduces reaction resistance and prevents cracking during charge-discharge cycles, thereby improving cycle characteristics while maintaining high capacity.
2Quantity of substance
If positive electrode active material undergoes volume change during charge-discharge, then battery capacity is improved, but cracking occurs and cycle characteristics deteriorate
Solution Approach 1:
The sulfonate compound forms a protective layer on the surface of the positive electrode active material before cracking can occur. This pre-established protective layer cushions the internal stresses generated during volume changes in charge-discharge cycles, preventing crack propagation and maintaining structural integrity while allowing high capacity operation.
3Reliability
If external pressure is applied to suppress expansion, then cycle characteristics are improved, but initial charge-discharge efficiency deteriorates
Solution Approach 1:
The sulfonate compound serves as an intermediary that allows the positive electrode active material to expand and contract during charge-discharge cycles without direct mechanical constraint. This intermediary layer accommodates volume changes while maintaining electrical contact and ionic conductivity, achieving both high initial charge-discharge efficiency and improved cycle characteristics without requiring external pressure.
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 combination of the sulfonate compound and external pressure enhances initial charge-discharge efficiency and maintains high capacity while improving cycle characteristics by reducing reaction resistance and suppressing positive electrode active material cracking.
Implementation Method 1
a sulfonate compound is present on a surface of the lithium-containing transition metal composite oxide
Implementation Method 2
a predetermined pressure is applied from the outside to a flat portion of the non-aqueous electrolyte secondary battery, thereby suppressing expansion of the positive electrode active material
Data Source
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AI summary
This nonaqueous electrolyte secondary battery comprises: an electrode body having a structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween; and an exterior body that accommodates the electrode body. The nonaqueous electrolyte secondary battery is characterized in that: a positive electrode active material is constituted of secondary particles formed by aggregation of primary particles; a sulfonic acid compound represented by formula (I) is present on the surface of the secondary particles; and through pressure applied from the outside of the exterior body in the lamination direction, in which the positive electrode, the negative electrode, and the separator are laminated, a pressure of 8.00× 10-2 MPa or greater is applied to the electrode body. (In the formula, A represents a group 1 element or a group 2 element, R represents a hydrocarbon group, and n represents 1 or 2.)