Battery Electrolyte Composition for Safety, Cycle Life, and Power
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Solution Overview
Problem
Current batteries face challenges in achieving a balance between safety performance and electrochemical performance, particularly in terms of cycle life and power performance, which is critical for applications like electric vehicles.
Innovation Solution
An electrolytic solution comprising a solvent with a compound represented by Formula (1) and ethylene carbonate, along with dimethyl carbonate and lithium bisfluorosulfonimide, which optimizes the weight percentages to enhance safety and cycle life while improving power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate is used as a solvent in the electrolytic solution, then safety performance is improved, but electrochemical performance and power performance deteriorate
Solution Approach 1:
The patent changes the concentration parameter of ethylene carbonate from conventional high levels (70-90 wt%) to a controlled low level (5-25 wt%), and introduces a new compound (Formula 1) at 5-35 wt% to replace part of the solvent system. This parameter transformation resolves the contradiction by achieving both safety and power performance improvements through optimized composition ratios.
Solution Approach 2:
The patent creates a composite solvent system combining ethylene carbonate with a fluorinated cyclic carbonate compound (Formula 1), dimethyl carbonate, and carboxylate. This composite approach allows the system to simultaneously achieve the flame resistance and safety of ethylene carbonate while gaining the low viscosity and high conductivity from the other components, thus resolving the power performance deterioration issue.
2Reliability
If ethylene carbonate content is increased to improve safety, then cycle life is reduced due to oxidative decomposition
Solution Approach 1:
The fluorinated cyclic carbonate compound (Formula 1) acts as an intermediary substance that prevents the harmful oxidative decomposition of ethylene carbonate. The compound preferentially undergoes oxidation to form a stable protective film on the positive electrode, thereby protecting the ethylene carbonate from decomposition and eliminating the source of gas generation that limits cycle life, while maintaining the safety benefits of ethylene carbonate.
Solution Approach 2:
The patent applies preliminary anti-action by having the fluorinated cyclic carbonate compound (Formula 1) preemptively form a stable protective film on the positive electrode before ethylene carbonate can undergo harmful oxidative decomposition. This preliminary protective action prevents the subsequent gas generation and electrode degradation that would otherwise limit cycle life, allowing the battery to achieve both high safety and long cycle life.
3Power
If conventional solvents are used to maintain low viscosity and high conductivity, then safety performance deteriorates
Solution Approach 1:
The patent transforms the solvent composition parameters by introducing a fluorinated cyclic carbonate compound (Formula 1) with specific molecular structure features (fluorinated alkyl groups) that inherently provide both low viscosity and high conductivity. Additionally, the compound's fluorinated structure provides flame resistance, thus achieving a parameter transformation that simultaneously improves power performance and safety performance without relying on high concentrations of conventional flammable solvents.
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 achieves high safety performance, extended cycle life, and enhanced power performance by reducing oxidative decomposition and improving electrical conductivity, thereby addressing the trade-off between safety and electrochemical performance.
Implementation Method 1
ethylene carbonate is easily oxidized at a positive electrode of the battery, thereby generating a large amount of gas
Implementation Method 2
The electrolytic solution according to this application further includes the low-viscosity organic solvents such as dimethyl carbonate and/or carboxylate, thereby increasing electrical conductivity of the electrolytic solution
Implementation Method 3
The electrolyte salt includes lithium bisfluorosulfonimide and lithium hexafluorophosphate
Data Source
AI summary
An electrolytic solution includes a solvent. The solvent includes a compound represented by Formula (1) below, in which R1 is a fluorinated C1 to C6 alkyl or a fluorinated C2 to C6 alkenyl, and R2 and R3 each independently are a hydrogen atom, a fluorine atom, or a fluorinated C1 to C6 alkyl. The solvent further includes ethylene carbonate. Based on a total weight of the solvent, a weight percent of the ethylene carbonate is less than or equal to 25 wt %.