Moisture-Proof Layer for All-Solid-State Battery
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Solution Overview
Problem
All-solid-state lithium ion secondary batteries with ceramic electrolytes face issues of moisture intrusion leading to battery capacity degradation due to weak moisture-proof layers, which crack under impact or absorb moisture, causing short circuits.
Innovation Solution
A moisture-proof layer composed of a cured product containing a polymer compound, such as polyethylene, and metal compound particles like metal oxide particles, is applied to the battery surfaces excluding terminal electrodes, enhancing mechanical strength and adhesion to prevent cracks and moisture absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film coating of silicon oxide or silicon nitride is applied to prevent moisture intrusion, then moisture resistance is improved, but film strength is low causing cracks under impact
Solution Approach 1:
The patent applies a composite coating layer comprising both an inorganic film (silicon oxide or silicon nitride) and an organic resin. The inorganic film provides moisture resistance while the resin matrix provides mechanical strength and flexibility. This composite structure prevents cracks under impact while maintaining moisture barrier properties, resolving the contradiction between moisture resistance and film strength.
2Strength
If resin is used for coating to provide mechanical strength, then film strength is improved, but resin absorbs moisture causing deterioration
Solution Approach 1:
The patent creates a composite coating where resin and inorganic film work synergistically. The resin provides mechanical strength and flexibility, while the inorganic film (silicon oxide or silicon nitride) embedded in the resin provides the moisture barrier. This composite approach allows each material to contribute its strengths without suffering its weaknesses alone.
Solution Approach 2:
The inorganic film acts as an intermediary barrier within the resin coating, preventing moisture from reaching and deteriorating the resin matrix. This intermediate protective layer allows the resin to provide mechanical strength while the inorganic film protects it from moisture absorption.
3Reliability
If low-melting glass is used for coating to prevent moisture contact, then moisture resistance is improved, but film strength is low causing cracks under impact
Solution Approach 1:
The patent replaces low-melting glass with a composite of resin and inorganic film. The resin provides the mechanical strength and flexibility that glass lacks, while the inorganic film particles dispersed in the resin maintain the moisture barrier properties. This composite substitution resolves the strength deficiency of glass-based coatings.
Data Source
AI summary
The present invention aims to provide an all-solid-state lithium ion secondary battery having a high reliability which does not have a decrease in battery capacity due to absorption of moisture in the air. The all-solid-state lithium ion secondary battery is provided with a battery body having an electrolyte layer between a positive electrode layer and a negative electrode layer, a pair of terminal electrodes respectively connected to the positive electrode layer and the negative electrode layer at both end portions of the battery body, and a moisture-proof layer disposed on surfaces excluding the surfaces to be the terminal electrodes, wherein the moisture-proof layer contains a cured product of a composition containing a polymer compound and metal compound particles.