Silicon Clathrate Active Material for Battery Volume Control
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Solution Overview
Problem
Si particles exhibit large volume change during charge and discharge, limiting their application in batteries due to structural constraints.
Innovation Solution
A method involving a precursor compound with a silicon clathrate I type crystal phase is treated with a polar liquid to desorb Na elements, maintaining the crystal structure and reducing volume change, resulting in an active material with a composition NaxMySi46, where M is a metal element other than Na, and the presence of a polar liquid residue on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Si particles are used as active material to achieve high energy condensation, then battery energy density is improved, but volume change during charge and discharge becomes large
Solution Approach 1:
The patent embeds Si particles within a clathrate crystal structure formed by alkaline earth metal elements and aluminum. This nested configuration allows the Si particles to be contained within the cage-like clathrate structure, providing structural support and constraint that limits volume expansion during lithium insertion, while still maintaining the high energy density benefits of Si-based active material.
Solution Approach 2:
The patent creates a composite active material consisting of Si particles combined with clathrate compounds formed from alkaline earth metal elements and aluminum. This composite structure combines the high capacity of Si with the structural stability of the clathrate framework, achieving both high energy density and reduced volume change during charge-discharge cycles.
2Volume of moving object
If Na element is desorbed from precursor compound to obtain active material, then volume change is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent employs liquid treatment to alter the chemical parameters of the precursor compound, specifically removing Na elements through chemical interaction with polar liquids. This parameter change transforms the composition from NaxMySi46 with high Na content to a modified composition with reduced Na content, achieving volume stabilization while managing manufacturing complexity through controlled chemical treatment.
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 method effectively reduces volume change during charge and discharge, enabling the production of batteries with improved capacity and cycle properties, and allows for reduced confining pressure, inhibiting size increase in battery components.
Implementation Method 1
by conducting the liquid treatment, an Na element may be efficiently desorbed while maintaining the silicon clathrate I type crystal structure
Implementation Method 2
a step of conducting a heat treatment to a NaSi compound containing at least a Na element and a Si element under decompressed pressure so as to desorb the Na element from the NaSi compound
Implementation Method 3
heat treatment temperature may be less than 550° C. and heat treatment time may be 12 hours or less
Data Source
AI summary
A main object of the present disclosure is to provide a novel active material of which volume change due to charge and discharge is small. The present disclosure achieves the object by providing a method for producing an active material having a composition represented by NaxMySi46 (M is a metal element other than Na, x and y satisfy 0<x, 0≤y, y≤x, and 0<x+y<8), and a silicon clathrate I type crystal phase, the method comprising: a preparing step of preparing a precursor compound having the silicon clathrate I type crystal phase; and a liquid treatment step of bringing the precursor compound into contact with a polar liquid so as to desorb a Na element from the precursor compound and obtain the active material.