Electrolyte Composition for Lithium-Ion Anode SEI Stability
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Solution Overview
Problem
Lithium-ion batteries face significant capacity loss due to mechanical and chemical damage of the Solid Electrolyte Interface (SEI) on the anode surface caused by volume changes during lithiation and delithiation, leading to reduced cycle stability and service life.
Innovation Solution
An electrolyte composition comprising aprotic, non-aqueous solvents, a fluorine-containing cyclic carbonate component, and at least two lithium salts, including lithium nitrate, which forms a stable SEI on the anode surface, preventing damage and maintaining capacity over multiple cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode materials such as silicon are used to increase energy density, then the theoretical capacity increases significantly, but the anode undergoes large volume changes during lithiation and delithiation causing SEI layer damage and continuous capacity loss
Solution Approach 1:
The electrolyte composition performs preliminary action by forming a stable SEI layer during initial cycles that is specifically designed to withstand subsequent volume changes. The fluorine-containing cyclic carbonate component and lithium nitrate work together during formation to create a pre-compression effect that densifies the SEI layer, preparing it to resist mechanical stress from future anode expansion and contraction cycles.
Solution Approach 2:
The invention uses a composite electrolyte system combining fluorine-containing cyclic carbonate component (such as fluoroethylene carbonate) with lithium nitrate. This composite approach creates synergistic effects where the fluorinated compound provides mechanical strength and flexibility to the SEI layer, while lithium nitrate enhances ionic conductivity and stabilizes the interface, together solving both capacity and stability requirements.
2Ease of operation
If the SEI layer is formed on the anode surface during initial cycles, then lithium transport is enabled, but the SEI layer is mechanically and chemically damaged by volume changes requiring continuous regeneration and causing capacity loss
Solution Approach 1:
The electrolyte composition provides beforehand cushioning by creating an over-protected SEI layer that is more robust than conventional SEI layers. The fluorine-containing cyclic carbonate component forms a flexible, mechanically strong interface that cushions against the mechanical stress of volume changes, while lithium nitrate provides chemical stabilization. This pre-cushioned SEI layer reduces the need for continuous regeneration and minimizes electrolyte decomposition.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by introducing fluorine-containing cyclic carbonate and lithium nitrate. These parameter changes alter the properties of the formed SEI layer, making it more mechanically resilient and chemically stable. The fluorine substitution and nitrate addition modify the SEI's elastic modulus, fracture toughness, and ionic conductivity to better withstand operational stress.
3Productivity
If conventional electrolyte compositions are used with high-capacity anodes, then the battery can operate, but the service life and cycle stability are reduced due to continuous SEI regeneration
Solution Approach 1:
The fluorine-containing cyclic carbonate component and lithium nitrate act as intermediaries between the anode and the bulk electrolyte. This intermediary SEI layer mediates the interaction by providing a stable interface that protects the anode from direct contact with aggressive electrolyte components while maintaining efficient lithium transport. The intermediary layer absorbs mechanical stress and prevents direct damage to the underlying anode structure.
Solution Approach 2:
The invention achieves continuity of useful action by creating an SEI layer that maintains its integrity over many cycles without requiring continuous regeneration. The stable SEI formed by the fluorinated electrolyte composition allows lithium transport to continue uninterrupted, eliminating the periodic breakdown and reforming cycles that normally occur with conventional electrolytes, thus extending service life.
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 electrolyte composition significantly enhances the cycle stability and service life of lithium-ion batteries by maintaining capacity at 80-95% after 60-100 cycles, with improved lithium transport and electrochemical stability.
Implementation Method 1
The surface layer that forms on the anode surface during the first cycles, also called SEI (Solid Electrolyte Interface), is mechanically and/or chemically damaged due to the volume changes of the anode during repeated lithiation and delthiation
Implementation Method 2
The electrolyte composition significantly enhances the cycle stability and service life of lithium-ion batteries by maintaining capacity at 80-95% after 60-100 cycles, with improved lithium transport and electrochemical stability
Implementation Method 3
improved lithium transport and electrochemical stability
Data Source
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AI summary
The present invention relates to an electrolyte composition for a lithium-ion battery, a lithium-ion battery and the use of a fluorine-containing cyclic carbonate component and lithium nitrate for improving the cycle stability and/or for increasing battery performance of a lithium-ion battery.