Inorganic Particles Buffer Solid Electrolyte Interface
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Solution Overview
Problem
All-solid lithium ion secondary batteries face challenges due to the peeling off of active materials from the solid electrolyte during repeated charge and discharge cycles, primarily due to the expansion and contraction of active materials, which affects the interface and cycle life.
Innovation Solution
Inorganic compound particles with a specific solvent content and particle size are used, providing lithium ion conductivity and improving the interface between the solid electrolyte and active materials, enhancing the battery's rate performance and life properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solid electrolyte and active material are simply adhered by heating, then the manufacturing process is simple, but the active material peels off from the electrolyte during repeated charge and discharge cycles due to expansion and contraction
Solution Approach 1:
An intermediate layer containing inorganic compound particles (such as Al2O3, SiO2, TiO2, or their composite oxides) is introduced between the solid electrolyte and the active material. This intermediate layer acts as a buffer that absorbs the stress from expansion and contraction of the active material during charge-discharge cycles, preventing peeling while maintaining good contact. The intermediate layer is formed by applying a slurry containing the inorganic compound particles to the solid electrolyte surface and heating at 100-500°C for 1-48 hours.
Solution Approach 2:
The patent uses composite materials by combining the solid electrolyte with inorganic compound particles in an intermediate layer. This composite structure integrates the benefits of both the solid electrolyte (high ion conductivity) and the inorganic compound particles (mechanical stability and stress resistance), creating a more reliable interface that withstands repeated cycling.
2Reliability
If the active material is allowed to expand and contract freely, then the material maintains its electrochemical activity, but the interface with the solid electrolyte deteriorates and cycle life is reduced
Solution Approach 1:
The intermediate layer containing inorganic compound particles is prepared in advance between the solid electrolyte and active material to cushion against the expansion and contraction forces that will occur during subsequent charge-discharge cycles. This pre-prepared buffer layer absorbs the mechanical stress before it can damage the interface, thereby extending cycle life while preserving electrochemical activity.
3Area of stationary object
If inorganic compound particles with small size are used, then the interface contact area increases, but the particle density increases making handling difficult
Solution Approach 1:
The patent optimizes the particle size parameters of the inorganic compound particles to be within 0.1-5 μm, with preferred ranges of 0.1-1 μm or 1-5 μm. This parameter optimization balances the need for large interface contact area (achieved by smaller particles) with the need for manageable particle density (avoiding excessively fine powders that are difficult to handle). The slurry application method further facilitates handling by suspending the particles in a liquid medium.
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 use of inorganic compound particles with a solvent content between 8-25 weight % and particle diameters between 0.1-5 μm improves lithium ion conductivity and reduces the impact of active material expansion, leading to enhanced cycle life and rate performance in secondary batteries.
Implementation Method 1
the inorganic compound particles having a lithium ion conductivity at 25° C. that is greater than or equal to 1×10-10 S/cm
Data Source
AI summary
A plurality of inorganic compound particles contain a solvent, wherein a weight ratio of the solvent to the inorganic compound particles is greater than or equal to 8 weight % and less than or equal to 25 weight %; the inorganic compound particles having a lithium ion conductivity at 25° C. that is greater than or equal to 1×10-10 S/cm; and an average particle diameter of the inorganic compound particles is greater than or equal to 0.1 μm and less than or equal to 5 μm.