Electrolyte Additive for Stable SEI on Silicon Anodes
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium-ion batteries experience rapid volume changes due to ion intercalation and deintercalation, leading to SEI layer fragmentation and battery degradation, necessitating a stable SEI layer that can withstand volume expansion.
Innovation Solution
An electrolyte additive containing a compound with a vinyl group and nitrogen atom forms a robust SEI layer on the electrode surface, comprising a durable amide group and Li3N-containing film, which stabilizes the silicon-based negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active materials are used to increase capacity, then energy density is improved, but volume expansion causes SEI layer fragmentation and battery degradation
Solution Approach 1:
The patent introduces a novel electrolyte additive with specific molecular structure (Formula 1) containing nitrogen and vinyl groups, which changes the chemical composition parameters of the SEI layer. This additive modifies the formation reaction parameters to create a more stable SEI layer that can accommodate silicon's volume expansion without fragmenting, thus resolving the contradiction between high capacity and cycle stability.
Solution Approach 2:
The patent creates a composite SEI layer structure by introducing the nitrogen-containing additive that forms Li3N and amide groups alongside traditional SEI components. This composite structure combines the benefits of traditional SEI protection with the mechanical stability and flexibility provided by the nitrogen-based compounds, enabling the SEI layer to withstand silicon's volume changes while maintaining protective function.
2Reliability
If the SEI layer is formed to protect the electrode surface, then stability is improved, but the SEI layer formed by carbonate-based solvents has weak elasticity and cannot maintain the film during volume expansion
Solution Approach 1:
The patent changes the chemical composition parameters of the SEI layer by introducing the nitrogen-containing additive (Formula 1). This additive undergoes electrochemical reactions to form Li3N and amide groups, which fundamentally alter the physical and chemical properties of the SEI layer, providing both stability and the necessary elasticity to accommodate volume expansion.
Solution Approach 2:
The patent creates local quality differences within the SEI layer by forming a multi-component structure with distinct regions: traditional carbonate-based SEI components providing stability, and nitrogen-based Li3N/amide groups providing flexibility and elasticity. This heterogeneous composition allows different parts of the SEI layer to fulfill different functional requirements simultaneously.
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 additive enhances the cycle properties and high-rate charging/discharging performance of lithium secondary batteries, particularly with high-capacity active materials, by minimizing SEI layer decomposition and side reactions.
Implementation Method 1
the solid electrolyte interface layer (hereinafter referred to as 'SEI layer') formed on the electrode surface as the carbonate-based non-aqueous solvent decomposes
Implementation Method 2
capable of forming a robust SEI layer on the electrode surface in the structure, thereby forming a durable amide group and Li 3 N-containing film on the negative electrode surface
Data Source
AI summary
The present disclosure provides an electrolyte additive, a non-aqueous electrolyte for a lithium secondary battery including the same, and a lithium secondary battery. Specifically, the present disclosure can provide a non-aqueous electrolyte for a lithium secondary battery capable of securing excellent cycle characteristics and a lithium secondary battery comprising the same by applying a non-aqueous electrolyte for a lithium secondary battery that includes an electrolyte additive capable of forming a robust SEI layer on the surface of the negative electrode.