Li22Si5-Derived Active Material Void Structure for Volume Stability
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Solution Overview
Problem
Existing active materials for batteries, such as Si-based materials, experience significant volume variation during charge/discharge cycles, which affects their performance and stability.
Innovation Solution
A method is developed to produce an active material by preparing a LiSi precursor with a crystal phase of Li22Si5, extracting the Li element using a solvent like ethanol or acetic acid, and forming voids within the material to reduce volume variation during charge/discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based active materials are used for battery anodes, then high capacity is achieved, but significant volume variation occurs during charge/discharge cycles
Solution Approach 1:
The patent applies porous silicon materials with controlled void spaces to accommodate volume expansion during lithium insertion. The porous structure allows the silicon framework to expand and contract without mechanical failure, maintaining structural integrity while enabling high lithium capacity. This resolves the contradiction by providing both high capacity (through silicon's inherent properties) and volume stability (through the porous architecture that absorbs expansion stress).
Solution Approach 2:
The patent creates composite structures combining silicon with other materials (such as carbon coatings or metal oxides) to form a composite active material. The silicon component provides high lithium capacity while the surrounding matrix material constrains volume expansion and maintains structural stability. This composite approach simultaneously achieves high capacity and volume stability during charge/discharge cycles.
2Stability of the object's composition
If Li element is extracted from LiSi precursor to form voids, then volume variation is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent employs preliminary action by forming the LiSi precursor with a specific crystal phase (Li22Si5) before the extraction step. This pre-formed precursor structure is designed to facilitate controlled Li extraction and void formation. By preparing the precursor in advance with the appropriate crystal structure, the subsequent extraction process becomes more efficient and controllable, reducing overall process complexity while achieving the desired volume stability.
Solution Approach 2:
The patent utilizes parameter changes by controlling the crystal phase composition (specifically the Li22Si5 phase ratio indicated by peak intensity ratio Ia/Ib ≥ 0.50) and extraction conditions (solvent type, temperature, time). By optimizing these parameters, the extraction process achieves controlled void formation with predictable outcomes. This parameter control reduces trial-and-error experimentation, simplifying the manufacturing process while ensuring consistent volume stability in the final product.
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 variation during charge/discharge cycles, enhancing the stability and performance of the active material, particularly in lithium-ion batteries.
Implementation Method 1
a void forming step of forming a void by extracting the Li element from the LiSi precursor by using a Li extracting solvent
Implementation Method 2
a dispersing step of obtaining a LiSi precursor dispersion by adding a dispersing medium with a specific dielectric constant of 3.08 or less to the LiSi precursor
Data Source
AI summary
A main object of the present disclosure is to provide a method for producing an active material wherein a volume variation due to charge/discharge is reduced. The present disclosure achieves the object by providing a method for producing an active material, the method comprising steps of: a preparing step of preparing a LiSi precursor including a Si element and a Li element, and a void forming step of forming a void by extracting the Li element from the LiSi precursor by using a Li extracting solvent, and the LiSi precursor includes a crystal phase of Li22Si5.