Lithium Battery Electrolyte SEI Formation for High-Temperature Stability
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Solution Overview
Problem
Rechargeable lithium batteries for electric vehicles face challenges in maintaining high power output and cycle life at various temperatures, particularly at high temperatures and during storage, due to limitations in forming an effective solid electrolyte interface (SEI) on the negative electrode.
Innovation Solution
An electrolyte composition for lithium batteries is developed, including specific lithium salts, non-aqueous organic solvents, and additives, which form a stable SEI on the negative electrode, enhancing performance at room temperature, low temperature, and high temperature conditions by optimizing the weight ratios and concentrations of these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional electrolyte compositions are used, then the battery can operate at room temperature, but the output characteristic deteriorates at high temperature and low temperature conditions
Solution Approach 1:
The patent applies parameter changes by systematically varying the composition ratios and concentrations of multiple electrolyte components (cyclic carbonates, chain carbonates, lithium salts, and additives) to optimize SEI formation across different temperature conditions. Specifically, the electrolyte contains cyclic carbonate 1-3, chain carbonate 3-6, lithium salt 0.5-2.0 M, and additive 0.01-5 wt%, with specific ratio ranges designed to maintain stable output characteristics from -30°C to 60°C operation temperatures
Solution Approach 2:
The patent employs composite materials by formulating a multi-component electrolyte system that combines cyclic carbonates (EC, PC, DEC, EMC), chain carbonates, lithium salts (LiPF6, LiBF4, LiClO4), and specific additives (LiDFOB, LiDFB, GBL). This composite electrolyte composition works synergistically to form a stable SEI layer that ensures reliable output characteristics across wide temperature ranges and during storage conditions
2Power
If the battery is designed for high power output, then the discharge voltage is high, but the cycle life deteriorates at high temperature
Solution Approach 1:
The patent uses the solid electrolyte interface (SEI) layer as an intermediary between the electrode and electrolyte. The SEI layer, formed by the specific electrolyte composition containing cyclic carbonates, chain carbonates, lithium salts, and additives, acts as a protective mediator that enables high discharge voltage operation while preventing degradation reactions that would otherwise reduce cycle life at elevated temperatures
Solution Approach 2:
The patent optimizes the concentration and ratio parameters of electrolyte components to achieve both high power output and long cycle life. The electrolyte contains lithium salt at 0.5-2.0 M concentration, cyclic carbonate 1-3, chain carbonate 3-6 in specific ratios, and additive at 0.01-5 wt%, creating an SEI layer with appropriate ionic conductivity and protective properties that maintains cycle life during high discharge voltage operation
3Power
If the battery operates at high temperature, then the power output is maintained, but the capacity deterioration accelerates during storage
Solution Approach 1:
The patent applies preliminary action by forming a stable SEI layer through the specific electrolyte composition before the battery undergoes storage or high-temperature operation. The pre-formed SEI layer, created by the synergistic action of cyclic carbonates, chain carbonates, lithium salts, and additives in optimized ratios, prevents subsequent capacity deterioration during storage at elevated temperatures while maintaining power output capability
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 improves the cycle life and output characteristics of lithium batteries at high temperatures and during storage, reducing capacity deterioration and maintaining high performance across different temperature ranges.
Implementation Method 1
adding an appropriate additive to form an excellent solid electrolyte interface (SEI) on the surface of a negative electrode
Implementation Method 2
a positive electrode including a positive active material that can intercalate and deintercalate lithium, and a negative electrode including a negative active material that can intercalate and deintercalate lithium
Data Source
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AI summary
The present invention provides an electrolyte for a rechargeable lithium battery, which includes at one first lithium salt; at least one second lithium salt including a compound represented by Chemical Formula 1, Chemical Formula 3-1 or Chemical Formula 3-2, or a combination thereof; at least one nonaqueous organic solvent; and at least one additive including a compound represented by the following Chemical Formula 9, and a rechargeable lithium battery including the same.