Lithium Battery Electrolyte Swelling Suppression via Cyclic Ester
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Solution Overview
Problem
Lithium secondary batteries face issues with excessive swelling at high temperatures due to electrolyte decomposition, which affects their performance and safety, especially when using nickel-containing active materials, and existing solvents with high boiling points and dielectric constants have limitations in viscosity and wettability.
Innovation Solution
An electrolyte composition comprising a cyclic ester, a nitrile-containing solvent at 1-5% volume, and a lithium salt, which improves swelling characteristics and discharge capacity at low temperatures, while maintaining suitable wettability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate) are used as electrolyte components, then the battery can operate with standard electrolyte composition, but excessive swelling phenomenon occurs at high temperature due to electrolyte decomposition
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing γ-butyrolactone (cyclic ester) as a specific solvent component and controlling the content of nickel-containing positive electrode active material to 30-80 wt%. This parameter change resolves the swelling issue by selecting materials with appropriate thermal stability and electrochemical properties that prevent decomposition at high temperatures.
Solution Approach 2:
The patent creates a composite electrolyte system combining γ-butyrolactone (cyclic ester) with conventional carbonate solvents, and a composite electrode structure with nickel-containing positive electrode active material (30-80 wt%) combined with other positive electrode materials. This composite approach leverages the high boiling point and dielectric constant of γ-butyrolactone while maintaining overall electrolyte performance and reducing swelling.
2Reliability
If γ-butyrolactone is used as a solvent to suppress swelling phenomenon, then high boiling point and high dielectric constant properties improve swelling resistance, but viscosity increases and wettability to separator deteriorates
Solution Approach 1:
The patent optimizes the concentration parameter of γ-butyrolactone in the electrolyte to achieve the right balance between swelling resistance and wettability. By controlling the cyclic ester content and combining it with conventional carbonate solvents, the electrolyte maintains appropriate viscosity and surface tension properties for good separator wettability while retaining the high-temperature stability benefits of γ-butyrolactone.
Solution Approach 2:
The patent creates a composite solvent system where γ-butyrolactone (cyclic ester) is combined with conventional carbonate solvents. This composite electrolyte formulation balances the high viscosity and low wettability of pure γ-butyrolactone with the better flow properties of carbonate solvents, achieving both swelling resistance and adequate wettability to the separator.
3Ease of operation
If alternative solvents with low boiling point and low dielectric constant are used to replace γ-butyrolactone, then viscosity and wettability improve, but swelling phenomenon reoccurs at high temperature
Solution Approach 1:
The patent selects γ-butyrolactone as the cyclic ester component specifically because of its high boiling point and high dielectric constant properties, which provide inherent swelling resistance. The concentration and composition parameters are optimized to ensure that even though γ-butyrolactone has higher viscosity, the overall electrolyte system maintains swelling resistance at high temperatures while achieving acceptable wettability through proper formulation.
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 effectively suppresses swelling at high temperatures and maintains excellent discharge capacity at low temperatures, ensuring better battery performance and stability.
Implementation Method 1
a swelling phenomenon occurs in which the center of a specific surface is transformed, for example, a battery is swollen in a specific direction due to a gas generated by decomposition of an electrolyte in the battery at a high temperature
Implementation Method 2
an electrolyte for a lithium secondary battery includes: a cyclic ester; an organic solvent including a nitrile-containing solvent represented by the following Formula 1 at a content ranging from of 1 to 5% by volume based on the total volume of the cyclic ester and the nitrile-containing solvent; and a lithium salt
Data Source
AI summary
An electrolyte for a lithium secondary battery, and a lithium secondary battery including the same are provided. The electrolyte includes: a cyclic ester; an organic solvent including a nitrile-containing solvent represented by Formula 1 at a content ranging from 1 to 5% by volume; and a lithium salt,R—C≡N (1)wherein R is selected from the group consisting of a C1 to C10 aliphatic hydrocarbon, a C1 to C10 halogenated aliphatic hydrocarbon, a C6 to C10 aromatic hydrocarbon, and a C6 to C10 halogenated aromatic hydrocarbon. The electrolyte can improve swelling characteristics and discharge capacity characteristics at a low temperature, and realize equal or better performance in characteristics such as capacity, life span and the like, as compared to a conventional carbonate-containing electrolyte.