Lithium Battery Electrolyte Solvent Ratio for Low-Temperature Performance
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Solution Overview
Problem
Lithium secondary batteries face challenges with low-temperature performance due to poor solubility of lithium salts in organic solvents and viscosity-related conductivity issues, leading to deteriorated operational characteristics.
Innovation Solution
A lithium secondary battery design utilizing a specific composition of cyclic and linear carbonate esters as solvents, along with a compound like vinylene carbonate, in a controlled ratio, combined with optimized cathode and anode porosity, to create an electrolyte solution with high ion conductivity and safety features such as non-inflammability at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cyclic carbonate ester solvents are used, then solubility for lithium salts is improved, but viscosity increases
Solution Approach 1:
The patent combines cyclic carbonate ester (high solubility) with linear carbonate ester (low viscosity) in a specific ratio to create an electrolyte solution that achieves both high lithium salt solubility and low viscosity, resolving the contradiction between these two properties
Solution Approach 2:
The electrolyte solution uses a composite solvent system comprising multiple carbonate esters with different molecular structures and properties, where each component contributes specific characteristics to achieve overall optimal performance in both solubility and viscosity
2Force
If linear carbonate ester solvents are used, then viscosity is reduced, but solubility for lithium salts deteriorates
Solution Approach 1:
The patent merges linear carbonate ester (low viscosity) with cyclic carbonate ester (high solubility) in optimized proportions to simultaneously achieve low viscosity and high lithium salt solubility, resolving this contradiction
Solution Approach 2:
The composite solvent system integrates linear and cyclic carbonate esters where the linear component controls viscosity while the cyclic component ensures adequate lithium salt solubility, balancing both 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 solution maintains output characteristics across temperatures, enhances safety, and improves low-temperature performance, making it suitable for hybrid electric vehicles and other applications.
Implementation Method 1
an electrolyte solution which comprises as solvents: a cyclic carbonate... a linear carbonate... and a compound...
Implementation Method 2
Cyclic carbonate ester solvents have a high viscosity, although they have a high solubility for lithium salts
Data Source
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AI summary
The present invention provides a lithium secondary battery which has improved safety, mainly coming from use of an electrolyte solution which is not inflammable at room temperature (20°C), while not deteriorating output characteristics at low temperatures and room temperature or output maintenance characteristics after storage at high temperature (50°C). The lithium secondary battery of the present invention, encased in a container, is provided with a cathode and an anode, both capable of storing/releasing lithium ions, a separator which separates these electrodes from each other, and an electrolyte solution containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) as solvents, the DMC/EMC ratio by volume being 0.6 to 1.3.