Mixed Additive Electrolyte for Lithium Battery High-Temperature Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with high-temperature storage and overcharge stability due to the degradation of the solid electrolyte interface (SEI) layer, leading to battery swelling and potential fire or explosion, and existing additives often degrade the overall performance of the battery.
Innovation Solution
A non-aqueous electrolyte solution is developed with a mixed additive composition of lithium difluorophosphate, fluorobenzene, tetravinylsilane, and a compound containing a sulfonate or sulfate group in specific weight ratios, which forms a stable SEI layer on the electrode surfaces, enhancing high-temperature and overcharge stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional organic solvent is used in the electrolyte solution, then the battery can operate, but gas is generated during high-temperature storage due to oxidation side reactions, causing battery swelling and deformation
Solution Approach 1:
The patent introduces a specific additive (lithium difluorophosphate combined with fluorinated cyclic carbonate) as an intermediary substance that mediates between the organic solvent and the electrode. This additive forms a protective SEI layer that prevents direct contact and oxidation reactions between the solvent and electrode, thereby eliminating gas generation during high-temperature storage while maintaining battery operation
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte additive package by specifically selecting lithium difluorophosphate in combination with fluorinated cyclic carbonates (FEC, FPC). This parameter change in additive chemistry fundamentally alters the SEI layer properties, making it more stable and less prone to decomposition at high temperatures, thus preventing gas generation
2Reliability
If the SEI layer is formed to prevent side reactions, then high-temperature stability improves, but the SEI layer collapses during high-temperature storage, exposing the negative electrode and causing continuous side reactions
Solution Approach 1:
The patent creates a composite SEI layer structure by combining multiple additive components (lithium difluorophosphate with fluorinated cyclic carbonates). This composite approach produces an SEI layer with enhanced structural integrity and chemical stability that can withstand high-temperature storage conditions without collapsing, maintaining its protective function over extended storage periods
Solution Approach 2:
The additive combination proactively forms a pre-stabilized SEI layer during initial charging cycles that is specifically designed to resist high-temperature degradation. This beforehand cushioning protects the negative electrode from exposure and continuous side reactions during subsequent high-temperature storage
3Reliability
If existing additives are added to improve stability, then high-temperature characteristics improve, but overall battery performance degrades due to other side effects
Solution Approach 1:
The patent applies local quality improvement by targeting specific functional requirements at the electrode interface. The additive combination specifically enhances SEI layer stability at the negative electrode without introducing harmful side effects elsewhere in the battery system, thus improving high-temperature characteristics while maintaining overall performance
Solution Approach 2:
The patent optimizes the chemical parameters of the additive package by selecting specific compounds (lithium difluorophosphate with fluorinated cyclic carbonates) in controlled amounts. This precise parameter control allows formation of a stable SEI layer that improves high-temperature characteristics without degrading overall battery performance through excessive side reactions
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 solution significantly improves the battery's high-temperature storage characteristics, cycle life, and overcharge stability by forming a robust SEI layer, reducing gas generation and internal pressure, and preventing battery deformation and ignition.
Implementation Method 1
lithium ions, which are discharged from the positive electrode by charging, transfer energy while a phenomenon is repeated in which the lithium ions are intercalated into the negative electrode, for example, carbon particles, and deintercalated during discharging
Implementation Method 2
a layer is formed on a surface of the negative electrode while some of electrolyte solution additive components and organic solvents are decomposed in a voltage range of 0.5 V to 3.5 V during initial charge
Implementation Method 3
lithium ions react with the electrolyte solution on the surface of the negative electrode to form compounds, such as Li2CO3, Li2O, and LiOH
Implementation Method 4
the SEI layer may only pass the lithium ions by acting as an ion tunnel
Implementation Method 5
gas is generated while the organic solvent is oxidized by a side reaction with a transition metal oxide discharged from the positive electrode
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In an embodiment, a non-aqueous electrolyte solution for a lithium secondary battery includes a lithium salt, an organic solvent, and an additive, wherein the additive is a mixed additive which includes lithium difluorophosphate, fluorobenzene, tetravinylsilane, and a compound containing one sulfonate group or sulfate group in a weight ratio of 1:2:0.05:0.5 to 1:8:0.3:2.