Nonaqueous Electrolyte with Cyclic Sulfate for High-Voltage Li-Ion Cells
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Solution Overview
Problem
Current nonaqueous electrolytes used in lithium-ion batteries face challenges such as poor oxidation resistance, easy decomposition, gas generation, low flash point, and safety concerns under high voltage and high temperature conditions, particularly in lithium cobalt oxide or high nickel ternary systems.
Innovation Solution
A nonaqueous electrolyte comprising a mixed solvent of high oxidation potential and carbonate solvents, along with cyclic sulfate as an additive, which forms a stable interface protective film on electrodes to enhance safety and electrochemical performance, improving overcharge safety, hot box safety, and kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbonate solvents are used in nonaqueous electrolytes, then the electrolyte has good ionic conductivity and low viscosity, but the oxidation resistance is poor, leading to easy decomposition and gas generation at high voltage
Solution Approach 1:
The patent uses a composite solvent system combining cyclic carbonate (EC, PC) and chain carbonate (DMC, DEC, EMC) solvents with specific proportions. This composite approach leverages the high dielectric constant and oxidation resistance of cyclic carbonates while utilizing the low viscosity and high ionic conductivity of chain carbonates, achieving both stability and conductivity at high voltage
Solution Approach 2:
The patent optimizes the proportion parameters of different carbonate solvents in the electrolyte system. By adjusting the ratios of cyclic to chain carbonates and specific chain carbonate compositions, the patent achieves the optimal balance between oxidation resistance, viscosity, and ionic conductivity for high-voltage operation
2Reliability
If the electrolyte system is designed for high voltage operation, then the oxidation resistance improves, but the kinetic performance and ionic conductivity may deteriorate
Solution Approach 1:
The patent employs a composite carbonate solvent system that combines the advantages of cyclic carbonates (high dielectric constant, oxidation resistance) with chain carbonates (low viscosity, high ionic conductivity). This composite approach ensures both oxidation resistance for high voltage and sufficient ionic conductivity for good kinetic performance
Solution Approach 2:
The patent applies different solvent types in specific proportions to different functional requirements: cyclic carbonates primarily provide oxidation resistance and dielectric properties, while chain carbonates contribute to low viscosity and high ionic conductivity. This localized functional assignment optimizes both oxidation resistance and kinetic performance
3Quantity of substance
If conventional electrolytes are used in lithium cobalt oxide or high nickel ternary systems, then the battery achieves high energy density, but the safety performance such as overcharge safety and hot box safety deteriorates
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance that reacts with the electrolyte to form a stable protective film on the electrode surface. This film acts as a barrier that prevents direct contact between the electrolyte and electrode, suppressing side reactions and improving safety while maintaining the high energy density benefits of lithium cobalt oxide and high nickel ternary systems
Solution Approach 2:
The film-forming additive performs preliminary protective action by forming a stable interface film before any harmful reactions can occur. This pre-formed protective layer prevents overcharge reactions and thermal runaway, addressing safety concerns before they manifest during battery operation
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 safety and electrochemical performance of lithium-ion batteries by combining high oxidation resistance and non-flammability of high oxidation potential solvents with low viscosity and high dielectric constant of carbonate solvents, forming a thin and dense interface protective film that enhances lithium ion transfer kinetics and oxidation resistance.
Implementation Method 1
the additive includes cyclic sulfate... forms a stable interface protective film on electrodes
Implementation Method 2
high oxidation potential solvent... improve electrochemical performance... improve oxidation resistance
Implementation Method 3
carbonate solvent... ensure that the lithium-ion battery has some kinetic performance
Data Source
AI summary
This application provides a nonaqueous electrolyte, a lithium-ion battery, a battery module, a battery pack, and an apparatus. The nonaqueous electrolyte includes a nonaqueous solvent, a lithium salt, and an additive, where the nonaqueous solvent includes a carbonate solvent and a high oxidation potential solvent, and the additive includes cyclic sulfate. The high oxidation potential solvent is selected from one or more of compounds represented by formula I and formula II, and the cyclic sulfate may be selected from one or more of compounds represented by formula III. This application can not only improve electrochemical performance of the lithium-ion battery under high temperature and high voltage and improve safety performance such as overcharge safety and hot box safety of the lithium-ion battery, but also ensure that the lithium-ion battery has some kinetic performance.