Silicon-Anode Electrolyte Coating for Stable Cycle Life
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Solution Overview
Problem
The use of silicon negative electrodes in lithium-ion batteries leads to large volume expansion during charging and discharging, causing destruction of the protective layer and increased side reactions with the electrolyte, resulting in gas production and rapid capacity decline.
Innovation Solution
An electrolyte containing sulfonic anhydride compounds forms a stable protective layer on the silicon negative electrode, suppressing side reactions and improving cycle life and gas production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon negative electrode is used to increase energy density, then energy density is improved, but volume expansion occurs during charging and discharging causing protective layer destruction
Solution Approach 1:
The patent applies preliminary action by pre-coating the silicon negative electrode with a protective layer containing compounds having S=O bonds (such as sulfones, sulfoxides, or sulfonates) before battery operation. This pre-formed protective layer prevents volume expansion from destroying the coating, as the layer is designed to accommodate silicon's volume changes while maintaining integrity and preventing electrolyte contact with the silicon surface.
Solution Approach 2:
The patent employs composite materials by combining silicon with materials containing S=O bonds (sulfones, sulfoxides, sulfonates) to create a composite coating structure. This composite approach leverages the high capacity of silicon while the S=O containing materials provide structural stability and chemical protection, creating a synergistic system that resolves the contradiction between energy density and protective layer stability.
2Reliability
If protective layer on silicon surface is destroyed due to volume expansion, then side reactions with electrolyte increase, but gas production and capacity decline occur
Solution Approach 1:
The patent converts the harmful effect of volume expansion into a beneficial outcome by designing a protective layer that not only withstands expansion but utilizes it to create a more stable and uniform coating structure. The S=O containing compounds form a flexible protective matrix that accommodates volume changes, transforming the mechanical stress from harmful to beneficial by improving coating uniformity and reducing defects that would otherwise lead to gas production and capacity decline.
Solution Approach 2:
The protective layer containing S=O bond compounds acts as an intermediary between the silicon negative electrode and the electrolyte. This intermediate layer prevents direct contact between the electrolyte and silicon surface, thereby suppressing side reactions that would generate gas and cause capacity decline, while still allowing lithium ion transport to maintain battery functionality.
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 protective layer enhances the cycle life and reduces gas production in lithium-ion batteries with silicon negative electrodes.
Implementation Method 1
the electrolyte includes at least one sulfonic anhydride compound... forms a stable protective layer on the surface of silicon negative electrode... suppressing side reactions of the electrolyte on the silicon negative electrode
Data Source
AI summary
An electrochemical device including a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode active material layer, including a negative electrode active material, wherein the negative electrode active material includes a silicon-containing compound; and the negative electrode active material further includes, on the surface, a protective layer including a compound having an S═O bond.