Silicon-Based Composite Negative Electrode Material for Lithium Battery
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Solution Overview
Problem
Silicon-based negative electrode materials for lithium-ion batteries face issues such as significant volume expansion, low initial-cycle Coulombic efficiency, and poor cycle performance due to the presence of inactive components like oxygen, leading to reduced cycle life and energy density.
Innovation Solution
A method involving in situ doping of alkali metal, alkaline earth metal, or third group elements to consume inactive components, forming silicate, which buffers volume expansion, combined with carbon coating to enhance conductivity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode material, then lithium storage capacity is improved, but volume expansion occurs during lithiation process
Solution Approach 1:
The patent employs a core-shell structure where silicon-based active material particles are nested within an amorphous carbon coating layer. The carbon shell acts as a container that accommodates the volume expansion of silicon during lithiation while maintaining structural integrity, preventing particle crushing and electrode pulverization.
Solution Approach 2:
The patent utilizes polyhedral oligomeric silsesquoxane (POSS) as a precursor that transforms into amorphous carbon coating through thermal pyrolysis. This parameter change in the coating material's structural state (from crystalline to amorphous) allows the coating to better accommodate volume changes and maintain flexibility during battery cycling.
2Quantity of substance
If silicon-based material is used as negative electrode material, then lithium storage capacity is improved, but conductivity is reduced
Solution Approach 1:
The patent creates a composite structure combining silicon-based active material with conductive amorphous carbon coating. The carbon coating layer serves as a conductive network that facilitates electron transport while the silicon core provides high lithium storage capacity, achieving synergistic improvement in both conductivity and capacity.
3Volume of moving object
If core-shell structure is adopted, then volume expansion is relieved, but morphology is lost during electrode plate preparation
Solution Approach 1:
The patent employs an amorphous carbon coating layer that functions as a flexible shell surrounding the silicon core. The amorphous structure of the carbon coating provides flexibility and deformability, allowing it to accommodate volume changes during lithiation/delithiation cycles while maintaining the overall particle morphology and preventing structural collapse during electrode fabrication.
4Quantity of substance
If silicon monoxide material is used, then inactive component is reduced, but irreversible capacity increases
Solution Approach 1:
The patent extracts and removes oxygen from silicon monoxide through magnesiothermic reduction, converting SiOx into pure silicon. This extraction of the inactive oxygen component increases the proportion of active silicon material that can reversibly store lithium, thereby reducing irreversible capacity loss and improving coulombic efficiency.
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 significantly improves initial Coulombic efficiency and cycle performance, reducing the proportion of crystal regions, thereby enhancing the energy density and cycle life of the silicon-based composite negative electrode material.
Implementation Method 1
in situ doping of alkali metal, alkaline earth metal, or third group elements to consume inactive components, forming silicate
Implementation Method 2
combined with carbon coating to enhance conductivity and cycle performance
Implementation Method 3
the product silicate can buffer volume expansion generated in the lithium intercalation process
Data Source
AI summary
A preparation method of silicon-based composite negative electrode material for a lithium battery includes the following steps: forming steam from a raw material A containing Si and a reducing substance raw material B capable of reacting to generate a silicate under a vacuum heating condition, condensing and depositing in a deposition system after a reaction, and then carrying out carbon coating to obtain the silicon-based composite material. A certain amount of alloy is added into the raw material B, so that a proportion of a crystal region in the silicon-based composite material can be reduced, and the initial coulombic efficiency and the cycling stability of the negative electrode material are further improved.