Secondary Battery Electrolyte for Wide Temperature Operation
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Solution Overview
Problem
Lithium-ion secondary batteries face performance issues at low and high temperatures, with reduced functionality below freezing and potential shortening of lifespan at elevated temperatures, necessitating a solution for stable operation across a wide temperature range.
Innovation Solution
Incorporating an electrolyte mixture of acyclic esters and fluorinated carbonic esters, specifically with 5 vol.% or higher fluorinated cyclic carbonate, to reduce interface resistance and enhance the stability of lithium ions, allowing for efficient charge and discharge at temperatures from -40°C to 150°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolytes are used, then the battery can operate at standard temperatures, but the performance deteriorates at low and high temperatures
Solution Approach 1:
The patent uses a composite electrolyte system combining fluorinated cyclic carbonate (FCC) with other carbonate esters. The FCC component specifically addresses low-temperature performance by reducing desolvation energy, while the composite formulation maintains overall battery stability across the -40°C to 150°C operating range, resolving the contradiction between temperature range and performance stability.
Solution Approach 2:
The patent modifies the electrolyte composition by introducing fluorinated cyclic carbonate with specific chemical structure parameters. The fluorine substitution in the cyclic carbonate structure changes the dielectric constant and solvation characteristics, enabling the electrolyte to maintain effective lithium ion solvation and transport across extreme temperature variations, thus improving both temperature range and performance stability.
2Productivity
If the battery operates at high temperatures, then charging and discharging speed increases, but the lifetime is shortened
Solution Approach 1:
The fluorinated cyclic carbonate modifies the electrolyte's thermal properties and interfacial characteristics. This parameter change in the electrolyte composition reduces the degradation rate of electrode materials at high temperatures while maintaining efficient ion transport, allowing the battery to achieve high charge/discharge rates without proportionally reducing lifetime.
3Use of energy by moving object
If the battery operates at low temperatures, then energy conservation is improved, but the functionality is reduced
Solution Approach 1:
The fluorinated cyclic carbonate's modified solvation parameters enable effective lithium ion desolvation at low temperatures. This parameter change in the electrolyte's chemical structure allows the battery to maintain adequate functionality even in cold conditions, reducing the need for energy-intensive heating while preserving basic operational capability.
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 proposed electrolyte composition enables stable operation of secondary batteries across a wide temperature range, ensuring reliable performance and safety by reducing desolvation energy and maintaining smoothness between active materials during volume changes, thus extending cycle life and safety.
Implementation Method 1
Lithium ions are dissolved in an electrolyte while the lithium ions are coordinated to and solvated by a solvent having high dielectric constant
Implementation Method 2
When the lithium ions enter a layer of a positive electrode or a negative electrode, the lithium ions approach the surface of the positive electrode or the negative electrode while the solvent is removed. Lithium ions in the state of being coordinated to solvent molecules, i.e., in a solvated state, are more stable than lithium ions alone. Therefore, energy is needed in a desolvation process of removing solvent molecules, thereby causing interface resistance in conducting lithium ions.
Implementation Method 3
Lithium ions are dissolved in an electrolyte while the lithium ions are coordinated to and solvated by a solvent having high dielectric constant
Data Source
AI summary
According to one embodiment of the present invention, a secondary battery that can be used at a wide range of temperatures and is less likely to be influenced by an environmental temperature is provided. Furthermore, a secondary battery with high safety is provided. An electrolyte obtained by mixing an acyclic ester having high temperature characteristics with a fluorinated carbonic ester at 5 vol. % or higher, preferably 20 vol. % or higher, is used for the purpose of reducing interface resistance between an electrode and an electrolyte, whereby a secondary battery capable of operating at a wide range of temperatures, specifically, at temperatures higher than or equal to −40° C. and lower than or equal to 150° C., preferably higher than or equal to −40° C. and lower than or equal to 85° C. can be achieved.