Electrolyte Composition for Silicon Anodes With LiF Film Stability
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Solution Overview
Problem
Lithium ion batteries with silicon negative electrodes face challenges in maintaining battery life and preventing resistance increases due to inadequate electrolyte solutions, particularly in high-voltage applications.
Innovation Solution
An electrolytic solution containing less than 10% by mass of a fluorinated ether, represented by the general formula HCF2CF2—O—R, where R is a fluorinated alkyl group, is used to form lithium fluoride (LiF) as a reducing film on the silicon negative electrode, improving battery life and resistance suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used with silicon negative electrodes, then battery capacity can be achieved, but battery life is insufficient and resistance increases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by specifying precise proportions of fluoroethylene carbonate (3-15 mass%), difluoroethylene carbonate (85-97 mass%), and fluoroether (0.5-10 mass%). This parameter optimization enables the formation of a stable LiF-rich film on silicon negative electrodes, suppressing resistance increase and extending battery life without sacrificing capacity
Solution Approach 2:
The patent creates a composite electrolyte system combining multiple carbonate esters (fluoroethylene carbonate and difluoroethylene carbonate) with fluoroether. This composite approach leverages the complementary properties of each component: the carbonates form stable solid electrolyte interphase films while the fluoroether enhances lithium ion conductivity and film stability, resulting in superior battery performance
2Power
If high-voltage operation is implemented, then power output is improved, but electrolyte stability deteriorates
Solution Approach 1:
The patent optimizes the electrolyte composition parameters with high dielectric constant carbonate esters (fluoroethylene carbonate and difluoroethylene carbonate) that maintain stability at high voltages. The specific ratio range ensures sufficient ion solvation and stable SEI formation even under high-voltage conditions, enabling safe power enhancement without electrolyte decomposition
Solution Approach 2:
The patent uses small amounts of fluoroether (0.5-10 mass%) as a sacrificial additive that preferentially reacts to form protective films on the electrode surface. This fluoroether acts as a short-lived component that consumes itself to create a stable interface, protecting the main electrolyte from degradation at high voltages
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 specified electrolytic solution enhances battery life and suppresses resistance increases by forming a favorable LiF film on the silicon negative electrode, optimizing performance in lithium ion secondary batteries, especially at high voltages.
Implementation Method 1
forming a favorable LiF film on the silicon negative electrode
Data Source
AI summary
Provided are an electrolytic solution that can allow a secondary battery comprising a silicon negative electrode to be improved in life and suppressed in an increase in resistance, and a secondary battery using the electrolytic solution. An electrolytic solution for use in a battery comprising an electrode having a negative electrode material containing a silicon element and a carbon element, wherein the electrolytic solution comprises less than 10% by mass of a fluorinated ether represented by the following general formula (1): HCF2CF2—O—R (1), wherein R is a fluorinated alkyl group.