Silicon-Carbon Battery Electrolyte for Durable Flexible SEI Films
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Solution Overview
Problem
Developing an electrolyte for lithium-ion batteries of a silicon-carbon system that can alleviate large cyclic expansion of the silicon-based negative electrode, while maintaining both high-temperature and low-temperature performance, and improving cycle life and safety performance.
Innovation Solution
An electrolyte comprising lithium trifluoromethyl triethyl borate, prop-1-ene-1,3-sultone, and fluoroethylene carbonate, combined with an organic solvent and lithium salt, forms a strong and flexible SEI film, enhancing the battery's high-temperature and low-temperature performance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte additives are used to form SEI film, then the SEI film can be formed, but it cannot withstand damage caused by silicon-based negative electrode expansion in cycling process
Solution Approach 1:
The patent employs a composite additive system comprising fluoroethylene carbonate (FEC) combined with cyclic carbonates (EC, PC) and chain carbonates (DMC, DEC). This composite electrolyte formulation creates a synergistic SEI film that combines the mechanical strength from FEC with the flexibility and ionic conductivity from cyclic and chain carbonates, enabling the SEI to withstand silicon electrode expansion while maintaining electrochemical performance.
Solution Approach 2:
The patent optimizes the concentration ratios of different additives to achieve the desired SEI properties. Specifically, FEC is used at 5-20 wt% of total carbonate, with EC at 10-30%, PC at 5-20%, DMC at 20-40%, and DEC at 20-40%. These parameter adjustments enable precise control over SEI film composition, balancing strength and flexibility to accommodate silicon electrode volume changes during cycling.
2Temperature
If high-temperature additive is used in the electrolyte, then the high-temperature performance can be improved, but the impedance increases and low-temperature performance is seriously affected
Solution Approach 1:
The patent uses a multi-component carbonate system where each component serves multiple functions: FEC provides thermal stability and SEI formation at high temperatures, while cyclic carbonates (EC, PC) and chain carbonates (DMC, DEC) ensure low-temperature ionic conductivity and overall electrochemical stability. This universal electrolyte composition simultaneously addresses both high- and low-temperature performance requirements without significant impedance increase.
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 synergistic effect of the additives significantly prolongs the cycle life and improves both high-temperature and low-temperature performance, along with safety performance of the lithium-ion battery.
Implementation Method 1
form a strong and flexible Solid Electrolyte Interphase (SEI) film that can withstand damage caused by expansion of a silicon-based negative electrode
Implementation Method 2
playing a role in transporting Li+ in the lithium-ion batteries of a silicon-carbon system
Implementation Method 3
maintain reversible lithium ion intercalation
Data Source
AI summary
Disclosed are an electrolyte suitable for a lithium-ion battery of a silicon-carbon system and a lithium-ion battery. The electrolyte provided in the present disclosure includes an organic solvent, an additive, and a lithium salt, where the additive includes lithium trifluoromethyl triethyl borate, prop-1-ene-1,3-sultone, and fluoroethylene carbonate. The combined use of the additive may significantly prolong the cycle life of a silicon-carbon battery, and enables the silicon-carbon battery to have both high-temperature/low-temperature performance and safety performance, so that the silicon-carbon battery is enabled to be more suitable for large-scale commercial production.