Silicon Negative Electrode Sheet With Stable SEI Formation
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Solution Overview
Problem
The continuous consumption of the solid electrolyte interphase film on silicon-based negative electrodes in lithium-ion batteries leads to reduced cycle life and performance, primarily due to irregular volume expansion and side reactions during lithium-ion alloying and dealloying.
Innovation Solution
A negative electrode sheet is developed with a silicon-based material and an auxiliary agent containing a carbon-carbon double or triple bond, which undergoes electrochemical polymerization to form a stable solid electrolyte interphase film, reducing internal resistance and improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based material is used as negative electrode active material to achieve high gram capacity and rich content, then energy density is improved, but the solid electrolyte interphase film is continuously consumed during charging and discharging, resulting in reduced cycle life
Solution Approach 1:
The patent introduces a film-forming agent that undergoes electrochemical polymerization during initial charging cycles to form a stable solid electrolyte interphase film on the silicon-based material surface before normal operation begins. This preliminary film formation prevents continuous consumption during subsequent cycling, thereby improving cycle life while maintaining high energy density
Solution Approach 2:
The patent uses a film-forming agent containing carbon-carbon double or triple bonds as an intermediary substance. This agent undergoes electrochemical polymerization to create a stable protective film that mediates between the silicon-based active material and the electrolyte, preventing direct harmful interactions and reducing continuous consumption of the solid electrolyte interphase film
2Quantity of substance
If silicon-based material undergoes alloying and dealloying of lithium-ions, then high capacity is achieved, but irregular volume expansion occurs generating more interphases and consuming large amounts of solvent and auxiliary agent
Solution Approach 1:
The patent employs a polymer film formed by electrochemical polymerization of the film-forming agent as a flexible protective shell on the silicon-based material surface. This thin film accommodates the irregular volume expansion during lithium-ion alloying and dealloying while preventing excessive consumption of solvent and auxiliary agent, thus maintaining high lithium-ion capacity with reduced substance loss
3Object-affected harmful factors
If conventional solid electrolyte interphase film is formed on silicon-based negative electrode, then basic protection is provided, but the film is continuously consumed affecting battery performance and cycle life
Solution Approach 1:
The patent changes the chemical composition parameters of the solid electrolyte interphase film by introducing a film-forming agent with carbon-carbon double or triple bonds. This agent undergoes electrochemical polymerization to form a film with different structural and chemical properties that is more stable and less consumable, thereby extending cycle life while maintaining protection
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 stable solid electrolyte interphase film enhances lithium-ion and electron conduction, leading to improved cycle life and reduced internal resistance in lithium-ion batteries.
Implementation Method 1
the carbon-carbon double bond or carbon-carbon triple bond undergoes electrochemical polymerization at a low potential, and thus, a stable solid electrolyte interphase film is formed in the silicon-based negative electrode
Data Source
AI summary
The present disclosure provides a negative electrode sheet and a lithium-ion battery including same. A negative electrode active material, a conductive agent, a binder, and an auxiliary agent (a compound represented by Formula 1) are used in the negative electrode sheet of the present disclosure, the above substances are dissolved in a solvent, uniformly mixed, and coated on a surface of a negative electrode current collector, after drying, the negative electrode sheet of the present disclosure can be obtained. The auxiliary agent (the compound represented by Formula 1), due to its small molecular weight and short polymer chain segment, can be fully mixed with the negative electrode active material, conductive agent, and binder.