Solid-State Battery Anode Structure for Low-Pressure Cycle Durability
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Solution Overview
Problem
All solid state batteries using Si as an anode material face capacity durability issues due to large volume changes during charge and discharge, which can lead to ion and electron conducting path disruptions, especially when low restraining pressure is applied.
Innovation Solution
Incorporating a silicon clathrate type II crystal phase anode active material and maintaining a capacity ratio between anode and cathode within a specific range (2.5 to 4.8) while applying restraining pressure of 0 to 5 MPa, eliminating the need for a large restraining jig.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high restraining pressure is applied to maintain ion and electron conducting paths, then capacity durability is improved, but device complexity increases due to requirement of restraining jig
Solution Approach 1:
The invention extracts and eliminates the restraining jig from the battery structure by using silicon clathrate type II crystal phase anode active material that inherently maintains conducting paths through its unique crystal structure, resolving the contradiction between capacity durability and device complexity
Solution Approach 2:
The invention changes the crystal phase parameter of the anode active material from conventional Si to silicon clathrate type II, which has a specific open framework structure that accommodates volume changes while maintaining conducting paths, thereby improving capacity durability without requiring external restraining pressure
2Device complexity
If silicon clathrate type II crystal phase is used with low restraining pressure, then device complexity is reduced, but capacity durability may deteriorate due to volume change
Solution Approach 1:
The invention uses silicon clathrate type II crystal phase which has a composite structure combining Si atoms with cage-like frameworks, providing both volume expansion space and structural integrity to maintain conducting paths without external pressure
Solution Approach 2:
The open framework structure of silicon clathrate type II crystal phase beforehand cushions the volume changes during charge-discharge cycles, preventing conducting path disruption without requiring external restraining pressure
3Use of energy by moving object
If capacity ratio A is increased to improve anode capacity, then energy density is improved, but volume change during charge discharge increases
Solution Approach 1:
The invention changes the crystal structure parameter of the anode active material to silicon clathrate type II, which has an open framework that accommodates volume changes, allowing high capacity ratio A (2.5-4.8) without excessive volume expansion
Data Source
AI summary
A main object of the present disclosure is to provide an all solid state battery with excellent capacity durability when restraining pressure is not applied or even when low restraining pressure is applied thereto. The present disclosure achieves the object by providing an all solid state battery comprising layers in the order of a cathode layer, a solid electrolyte layer, and an anode layer; wherein the anode layer contains an anode active material including a silicon clathrate type II crystal phase; restraining pressure of 0 MPa or more and less than 5 MPa is applied to the all solid state battery in a layering direction; and when a capacity ratio of anode capacity with respect to cathode capacity is regarded as A, the capacity ratio A is 2.5 or more and 4.8 or less.