Lithium Battery Electrolyte Difluorophosphate Additives High Voltage Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with oxidative decomposition and swelling characteristics, especially at high temperatures, which affect their cycle-life performance and safety.
Innovation Solution
An electrolyte composition including a non-aqueous organic solvent, a lithium salt, a first additive with a difluorophosphate group, and a second additive of lithium difluorophosphate, which forms a stable solid electrolyte interface and protective layers on electrodes, reducing oxidative reactions and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lithium secondary battery is driven at high voltage, then energy density and power output are improved, but oxidative decomposition of the electrolyte worsens
Solution Approach 1:
The patent introduces a mediator substance (additive containing difluorophosphate group) that interacts with both the electrode and electrolyte to form a protective interface layer. This intermediary layer prevents direct contact between the electrolyte and electrode, reducing oxidative decomposition while allowing ion transport, thus enabling high voltage operation without sacrificing reliability.
Solution Approach 2:
The patent uses a composite electrolyte system combining multiple components (non-aqueous organic solvent, lithium salt, and difluorophosphate-containing additive) that work synergistically. The composite nature of the electrolyte provides both the conductivity needed for high power output and the stability required to resist oxidative decomposition at high voltages.
2Adaptability or versatility
If a lithium secondary battery is stored at high temperature, then operational flexibility is improved, but swelling characteristics and cycle-life worsen
Solution Approach 1:
The patent applies preliminary action by forming a stable protective film on the electrode surface before high-temperature storage conditions cause significant degradation. The difluorophosphate-containing additive proactively creates this protective layer during initial cycles, preventing subsequent swelling and maintaining cycle-life even when the battery is stored at high temperatures.
3Ease of manufacture
If conventional electrolyte additives are used, then manufacturing simplicity is maintained, but swelling characteristics at high temperature deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte additive by incorporating a difluorophosphate group with specific molecular structure (where A is a substituted or unsubstituted aliphatic chain or ether group). This parameter change in the additive's chemical composition provides high-temperature swelling resistance while maintaining ease of manufacture, as the additive can be introduced using conventional electrolyte preparation methods.
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 improves oxidative decomposition characteristics and cycle-life performance, while minimizing swelling and resistance increase, even at high temperatures, leading to a more stable and efficient lithium secondary battery operation.
Implementation Method 1
lithium difluorophosphate (LiPO 2 F 2 ), which forms a stable solid electrolyte interface and protective layers on electrodes
Implementation Method 2
reducing oxidative reactions and gas generation
Implementation Method 3
lithium salts dissolved in the non-aqueous organic solvent are used as an electrolyte
Data Source
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AI summary
Disclosed are an electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same. The electrolyte for a lithium secondary battery, according to an embodiment, can comprise: a nonaqueous organic solvent; a lithium salt; a first additive comprising a compound represented by a specific chemical formula; and a second additive including at least one of lithium difluorophosphate (LiPO2F2), a cyclic carbonate including a fluorine atom, and a dinitrile compound.