All-solid battery binder composition suppressing electrolyte cracking
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Solution Overview
Problem
All-solid state secondary batteries face issues with cracking in the solid electrolyte and electrode active material layers during manufacturing and use, leading to reduced manufacturing efficiency and battery performance, particularly due to pressurization.
Innovation Solution
A binder composition comprising polymer particles with specific particle size distribution and moisture content, including a graft polymer without surfactants, is used to form a solid electrolyte-containing sheet, which enhances ion conductivity and prevents cracking in the solid electrolyte and electrode active material layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a binder composition is used to adjust the interface state of solid particles in all-solid state secondary batteries, then the manufacturing process can be simplified and electrodes and electrolyte can be directly disposed in series, but cracking occurs in the solid electrolyte layer and electrode active material layer during manufacturing and use, leading to reduced manufacturing efficiency and battery performance
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by specifying it contains 80-95 mass% of a specific compound (formula 1) and 5-20 mass% of a polyether compound, with controlled molecular weight ranges and functional group ratios. This compositional parameter optimization prevents cracking while maintaining structural simplicity.
Solution Approach 2:
The binder composition uses a composite system combining the specific compound of formula (1) with polyether compounds having different molecular weights and functional groups. This composite approach creates a synergistic effect that improves interfacial adhesion and prevents cracking in the solid electrolyte and electrode layers.
2Reliability
If the solid electrolyte layer and electrode active material layer are formed using conventional binders, then the battery can be manufactured, but cracking occurs during pressurization in use, leading to deterioration in battery performance
Solution Approach 1:
The patent optimizes physical parameters of the binder including molecular weight (1,000-100,000), glass transition temperature (-50°C to 0°C), and functional group ratios (carboxyl:hydroxyl = 1:9 to 1:1). These parameter changes enhance the binder's flexibility and adhesion, preventing cracking under pressurization while maintaining performance stability.
Solution Approach 2:
The binder acts as an intermediary material between the solid electrolyte particles and electrode active material particles, providing a flexible interface that accommodates volume changes and mechanical stress. The specific molecular structure with carboxyl and hydroxyl groups enables strong interfacial bonding while maintaining mechanical compliance under pressurization.
Data Source
AI summary
Provided are a binder composition for an all-solid state secondary battery, a solid electrolyte-containing sheet, an all-solid state secondary battery, and a method of manufacturing a solid electrolyte-containing sheet, and a method of manufacturing an all-solid state secondary battery. The binder composition for an all-solid state secondary battery includes polymer particles (A) and a non-aqueous dispersion medium (B), in which the polymer particles (A) are formed of a graft polymer not including a surfactant and having two or more peaks in a scattering intensity distribution measured by a dynamic light scattering particle size distribution analyzer, and a moisture content of the composition is 100 ppm or lower by mass.