Fluorinated Electrolyte Composition for Low-Temperature Lithium Metal Cells
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Solution Overview
Problem
Metal negative secondary batteries, such as lithium metal batteries, face challenges with poor cycling performance and low-temperature capacity release, particularly due to issues like high electrolyte salt concentration, high viscosity, and low ionic conductivity, which hinder their application in high-endurance electric vehicles and other scenarios.
Innovation Solution
An electrolyte containing a solvent with a specific compound of formula I, which includes fluorine-containing substituents, is used to enhance oxidation resistance and ion transport properties, improving cycling performance and low-temperature discharge capacity retention by maintaining a stable ring structure and appropriate solvation ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high electrolyte salt concentration is used to improve ionic conductivity, then ion transport is enhanced, but viscosity increases and cycling performance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds with specific molecular structures (formula I) that have lower viscosity and higher ionic conductivity compared to conventional electrolytes. This parameter change resolves the contradiction by achieving high ion transport without the penalty of high viscosity.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate (formula I) with other carbonate solvents (cyclic and chain carbonates). This composite approach leverages the complementary properties of different components to achieve both low viscosity and high ionic conductivity, resolving the technical contradiction.
2Reliability
If conventional electrolyte composition is used to maintain stability, then oxidation resistance is adequate, but low-temperature capacity release is poor
Solution Approach 1:
The patent modifies the electrolyte's physical and chemical parameters by incorporating fluorinated groups into the cyclic carbonate structure. The fluorine substitution changes the molecular polarity, boiling point, and solvation characteristics, enabling the electrolyte to maintain stability while significantly improving low-temperature ionic conductivity and capacity release.
Solution Approach 2:
The patent applies local quality modification by introducing fluorine atoms at specific positions in the cyclic carbonate molecule (as defined in formula I with specific R1-R4 substituents). This localized chemical modification creates regions of enhanced polarity and solvation ability that specifically improve low-temperature performance without compromising overall oxidation resistance.
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 solution achieves a significant improvement in cycle life and low-temperature capacity release capability for metal negative secondary batteries, enabling them to perform effectively over a wide temperature range, including extreme low-temperature conditions.
Implementation Method 1
Further selecting the respective groups in the above-mentioned compound of formula I can make the electrolyte of the present disclosure have good oxidation resistance
Implementation Method 2
can effectively dissociate the electrolyte salts
Implementation Method 3
maintaining a stable ring structure and appropriate solvation ability
Data Source
AI summary
An electrolyte containing a solvent including at least one compounds of formula I, wherein A1 is an oxygen atom or a single bond, A2 is a single bond or CHR4, R1 and R2 are each independently a hydrogen atom, C1-6 alkyls or a C1-6 fluoroalkyls, R3 and R4 are each independently a hydrogen atom, a fluorine atom, C1-6 alkyls or C1-6 fluoroalkyls, A1 and A2 cannot both be single bonds simultaneously, and only one of R1 to R4 includes a fluorine atom is described. The electrolyte can make a metal negative electrode secondary battery have good cycling performance and good discharge capacity retention at low temperature.