High-Voltage Battery Electrolyte Composition for Cycle Gas Suppression
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Solution Overview
Problem
Existing electrolytes in high energy density lithium-ion batteries suffer from side reactions with positive electrode active materials at high working voltages, leading to cycle lifespan degradation and increased cycle gas generation, with a lack of systematic understanding and effective solutions.
Innovation Solution
An electrolyte composition comprising specific ratios of ethylene carbonate, propylene carbonate, fluorinated ethylene carbonate, and additives like 1,3-propane sultone and ethylene sulfate, optimized to enhance oxidation resistance and electrochemical stability, reducing side reactions and maintaining lithium ion transport capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the positive electrode active material is developed towards high energy density and high charging voltage, then the energy density of the battery is improved, but the stability of the positive electrode active material deteriorates and side reactions with the electrolyte increase
Solution Approach 1:
The patent introduces a specific electrolyte composition as an intermediary between the high-voltage positive electrode active material and the battery system. The electrolyte contains fluorinated ethylene carbonate (0.5-3 mass%), ethylene carbonate (2-10 mass%), propylene carbonate (5-20 mass%), and linear carbonate (60-85 mass%), which together form a protective interface that mediates the interaction between the electrolyte and the high-voltage cathode, preventing direct harmful reactions while maintaining ionic conductivity.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated ethylene carbonate and optimizing the ratios of conventional carbonate solvents. This parameter change transforms the electrolyte's chemical properties to achieve higher oxidation resistance and electrochemical stability, enabling compatibility with high-voltage (≥4.15V) positive electrode materials while maintaining lithium ion transport capacity.
2Temperature
If existing electrolyte is used with high working voltage battery, then the battery can operate at high voltage, but side reactions cause surface lattice collapse and oxygen release leading to cycle lifespan degradation
Solution Approach 1:
The patent converts the potential harm of high-voltage operation into a benefit by using fluorinated ethylene carbonate to form a stable protective film on the positive electrode surface. This film, formed through controlled initial reactions, prevents further harmful side reactions, lattice collapse, and oxygen release during cycling, thereby transforming the high-voltage environment from destructive to sustainable.
Solution Approach 2:
The patent uses a composite electrolyte system combining fluorinated ethylene carbonate with conventional carbonate solvents (ethylene carbonate, propylene carbonate, and linear carbonate). This composite composition synergistically provides both the oxidation resistance needed for high-voltage stability and the ionic conductivity required for battery operation, enabling long cycle lifespan at working voltages ≥4.15V.
3Temperature
If existing electrolyte is used with high working voltage battery, then the battery can operate at high voltage, but cycle gas generation increases
Solution Approach 1:
The fluorinated ethylene carbonate in the electrolyte acts as an intermediary that forms a stable protective interface film on the positive electrode. This film mediates the interaction between the electrolyte and electrode, preventing gas-generating side reactions while allowing ionic transport, thereby suppressing cycle gas generation during high-voltage operation.
4Reliability
If the electrolyte is optimized for oxidation resistance by reducing ethylene carbonate content, then the electrochemical stability is improved, but the conductivity performance may deteriorate
Solution Approach 1:
The patent employs a composite electrolyte formulation where fluorinated ethylene carbonate (0.5-3 mass%) provides oxidation resistance, ethylene carbonate (2-10 mass%) contributes to electrochemical stability and SEI formation, propylene carbonate (5-20 mass%) enhances dielectric constant and ionic conductivity, and linear carbonate (60-85 mass%) provides bulk conductivity. This composite system synergistically balances oxidation resistance and conductivity without compromising either property.
Solution Approach 2:
The patent optimizes the concentration parameters of multiple electrolyte components simultaneously. By precisely controlling the content of fluorinated ethylene carbonate (0.5-3 mass%) and the ratio of conventional carbonates, the electrolyte achieves both high oxidation resistance (for electrochemical stability) and sufficient ionic conductivity (for energy transport), resolving the trade-off between these two critical properties.
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 optimized electrolyte improves cycle lifespan and reduces cycle gas generation while ensuring conductivity, without deteriorating initial impedance, by adjusting component ratios to stabilize the positive electrode interface and form a stable solid electrolyte interphase film.
Implementation Method 1
the electrolyte optimizes the contents of other alternative components (the propylene carbonate and the fluorinated ethylene carbonate) to compensate for the decrease in dielectric constant and electrical conductivity caused by the reduction of ethylene carbonate
Implementation Method 2
ensuring the conductivity performance of the electrolyte
Data Source
AI summary
Provided are an electrolyte and a secondary battery. The electrolyte includes a lithium salt and a solvent. The solvent includes ethylene carbonate, propylene carbonate, fluorinated ethylene carbonate, and linear carbonate. A mass percentage of the ethylene carbonate relative to the solvent is 2% to 10%. A sum of a mass of the propylene carbonate and the fluorinated ethylene carbonate relative to the mass percentage of the solvent is 10% to 30%. The electrolyte may well match batteries with high working voltage, while ensuring that the initial impedance of the battery does not deteriorate, effectively improving the issues of poor cycle performance and large cycle gas generation of the battery.