Composite active material and battery
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Solution Overview
Problem
Si-based particles with pores, used as electrode active materials in batteries, face challenges due to increased specific surface area, leading to difficulty in maintaining a good interface with solid electrolytes, which can result in increased battery resistance.
Innovation Solution
A composite active material is developed, comprising Si-based particles with pores and a coating layer containing a solid electrolyte, with a Brunauer-Emmett-Teller (BET) specific surface area of 40 m2/g or less and a coverage of 20% or more by the coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Si-based particles with pores are used as electrode active material, then energy density is increased, but specific surface area increases leading to poor interface with solid electrolyte and increased battery resistance
Solution Approach 1:
The patent applies local quality by creating a coating layer with solid electrolyte on the surface of Si-based particles. This coating layer has different properties from the bulk Si particle - it provides good interface quality and ion conduction paths locally at the particle surface, while the interior Si particle maintains its high capacity characteristics. The coating layer thickness and composition are optimized to provide locally different functions: protecting the Si particle surface while allowing ion transport.
Solution Approach 2:
The patent uses composite materials by combining Si-based particles with a coating layer containing solid electrolyte. This composite structure integrates the high capacity advantage of Si with the good interface properties of solid electrolyte. The coating layer acts as an intermediate phase that bridges the Si particle and the bulk solid electrolyte, creating a composite active material that exhibits both high energy density and good interfacial contact.
2Use of energy by moving object
If Si-based particles with pores are used as electrode active material, then energy density is increased, but battery resistance increases due to poor interface maintenance
Solution Approach 1:
The coating layer containing solid electrolyte serves as an intermediary between the Si-based particle and the bulk solid electrolyte. This intermediate layer facilitates ion transport across the interface, reducing contact resistance. The coating layer mediates the interaction between Si and solid electrolyte, preventing direct contact issues while maintaining efficient ion conduction paths.
Solution Approach 2:
The coating layer provides locally optimized properties at the particle surface to reduce resistance. By controlling the coating thickness and composition, the patent creates a local region with enhanced ion conductivity and reduced contact resistance, while maintaining the overall high capacity characteristics of the Si-based particle.
3Reliability
If coating layer with solid electrolyte is applied to Si-based particles, then interface quality is improved, but specific surface area is reduced
Solution Approach 1:
The patent applies partial action by using a coating layer with coverage of 20% or more but not complete coverage. This partial coating approach is sufficient to provide the necessary interface quality and ion conduction paths without excessively reducing the specific surface area. The coating is applied to the extent needed to solve the interface problem while minimizing the loss of surface area for ion contact.
Data Source
AI summary
The composite active material includes an electrode active material including an Si element and having a void therein, and a coating layer covering the surface of the electrode active material and including a solid electrolyte. A composite active material is provided in which BET specific surface area of the composite active material is less than or equal to 40 m2/g, and the coverage by the coating layers is 20% or more.