Co-Sintered Lithium Secondary Battery for Stable Electrode Alignment
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Solution Overview
Problem
Lithium secondary batteries with ceramic positive and negative electrodes suffer from poor long-term reliability, particularly storage performance, due to displacement issues during assembly and waviness or warpage of sintered plates, leading to variations in electrode distance and reduced charge/discharge cycle performance.
Innovation Solution
A lithium secondary battery configuration where a positive electrode layer, ceramic separator, and negative electrode layer form an integrated sintered plate with specific capacity and thickness ratios (C/A of 1.03 to 2.30 and Tc/Ta of 0.50 to 2.00) to ensure accurate alignment and minimize displacement, enhancing long-term reliability and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate sintered plates are used for positive and negative electrodes, then high capacity and charge/discharge efficiency are achieved, but displacement and waviness during assembly occur leading to poor long-term reliability
Solution Approach 1:
The patent combines the positive electrode layer, ceramic separator, and negative electrode layer into a single integrated sintered plate formed by co-sintering. This merging eliminates the displacement and waviness issues that occur when separate sintered plates are assembled, as the integrated structure ensures precise alignment and structural stability throughout the battery's operational life.
2Reliability
If integrated sintered plate is used to eliminate displacement, then long-term reliability is improved, but charge/discharge cycle performance decreases due to waviness
Solution Approach 1:
The integrated sintered plate structure merges the positive electrode, separator, and negative electrode into one co-sintered component, eliminating relative displacement between layers during assembly and storage, thereby improving long-term reliability and storage performance.
Solution Approach 2:
The patent optimizes specific parameters of the integrated sintered plate to balance storage performance and cycle performance: the thickness ratio of positive to negative electrode layers is controlled at 0.50 to 2.00, and the capacity ratio C/A is maintained at 1.03 to 2.30. These parameter controls prevent excessive waviness while maintaining the integrated structure's alignment advantages.
3Reliability
If powder-dispersed positive electrode is used, then ease of manufacture is achieved, but capacity and charge/discharge efficiency are reduced due to low packing density
Solution Approach 1:
The integrated sintered plate uses a composite structure where the ceramic separator and electrode layers are co-sintered into a unified component. This composite approach eliminates the need for separate binder and conductive agent materials required in powder-dispersed electrodes, achieving high packing density of active materials while maintaining manufacturability through a single co-sintering process.
Data Source
AI summary
Provided is a lithium secondary battery including a positive electrode layer composed of a lithium complex oxide sintered body, a negative electrode layer composed of a titanium-containing sintered body, a ceramic separator interposed therebetween, an electrolytic solution, and an exterior body including a closed space, which accommodates the positive electrode layer, the negative electrode layer, the ceramic separator, and the electrolytic solution, wherein the positive electrode layer, the ceramic separator, and the negative electrode layer are bonded together, a ratio C/A of a capacity C of the positive electrode layer to a capacity A of the negative electrode layer is 1.03 to 2.30, a ratio Tc/Ta of a thickness Tc of the positive electrode layer to a thickness Ta of the negative electrode layer is 0.50 to 2.00, the thickness Tc is 50 to 1000 μm, and the thickness Ta is 50 to 1200 μm.