Fluorinated Carbonate Additive for Lithium Battery Electrolyte
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Solution Overview
Problem
Existing nonaqueous electrolytic solutions for lithium secondary batteries fail to maintain optimal electrochemical characteristics across a broad temperature range, leading to deteriorated cycle properties and discharge performance due to solvent decomposition and gas generation.
Innovation Solution
A nonaqueous electrolytic solution comprising specific compounds represented by general formulas (I), (II), and (III), which improve electrochemical characteristics by forming a dense, heat-resistant surface film on electrodes and enhancing wettability, thereby preventing excessive surface film densification and maintaining performance across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional nonaqueous electrolytic solutions are used in lithium secondary batteries, then the batteries can operate in a broad temperature range, but the electrochemical characteristics deteriorate due to solvent decomposition and gas generation
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the electrode surface and the bulk electrolyte. This compound forms a stable interface layer that prevents direct contact between the electrolyte solvent and electrode, thereby preventing decomposition reactions while maintaining ionic conductivity across a broad temperature range
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (formula 1) into the electrolyte system. This parameter change alters the interfacial properties and decomposition behavior of the electrolyte, enabling stable electrochemical performance from -40°C to +85°C
2Stability of the object's composition
If the nonaqueous solvent undergoes reductive decomposition on the negative electrode surface, then a surface film is formed, but the decomposed products and gases worsen cycle properties and electrochemical reactions
Solution Approach 1:
The patent converts the harmful decomposed products of conventional electrolytes into beneficial components by using fluorinated cyclic carbonate compounds that decompose to form stable, protective surface films containing fluorine. These films prevent further decomposition of the bulk electrolyte while maintaining lithium ion conductivity, thus transforming potential harm into a protective benefit
Solution Approach 2:
The fluorinated cyclic carbonate compound acts as an intermediary that forms a stable interface layer between the negative electrode and the bulk electrolyte. This intermediary layer prevents direct contact and further decomposition reactions, while its controlled decomposition products contribute to film stability and ionic conductivity
3Quantity of substance
If lithium metal or its alloys are used as the negative electrode material, then high initial battery capacity is achieved, but micronized powdering promotes accelerated reductive decomposition of the nonaqueous solvent
Solution Approach 1:
The fluorinated cyclic carbonate compound serves as an intermediary protective layer on the lithium metal or alloy surface. This intermediary film prevents direct exposure of the high-capacity lithium material to the bulk electrolyte, thereby suppressing micronized powdering and accelerated decomposition while preserving the high initial capacity
Solution Approach 2:
The patent changes the interfacial chemical environment parameters by introducing fluorinated cyclic carbonate compounds. This parameter change creates a stable interface that suppresses the micronized powdering phenomenon and reduces the reactivity between lithium metal and the electrolyte solvent, maintaining high capacity over cycles
4Stability of the object's composition
If the nonaqueous solvent undergoes oxidative decomposition at the positive electrode interface, then gases and decomposed products are generated, but these interfere with electrochemical reactions and worsen characteristics
Solution Approach 1:
The fluorinated cyclic carbonate compound forms an intermediary protective film at the positive electrode interface that prevents direct contact between the electrolyte solvent and electrode surface. This intermediary layer suppresses oxidative decomposition reactions that generate harmful gases and decomposed products, while maintaining ionic conductivity for electrochemical reactions
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 significantly enhances low-temperature cycle properties and discharge performance after high-temperature storage, outperforming previous solutions by maintaining battery efficiency and capacity retention across extreme temperature conditions.
Implementation Method 1
the solvent in the nonaqueous electrolytic solution undergoes reductive decomposition on the surface of the negative electrode during charging and the decomposed products and gases generated through the decomposition detract from the desired electrochemical reaction in the battery
Implementation Method 2
the solvent in the nonaqueous electrolytic solution undergoes reductive decomposition on the surface of the negative electrode during charging
Implementation Method 3
the nonaqueous solvent in the nonaqueous electrolytic solution locally undergoes partial oxidative decomposition in the interface between the positive electrode material and the nonaqueous electrolytic solution in a charged state
Data Source
AI summary
The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in a broad temperature range, such as low-temperature cycle properties and low-temperature discharge properties after high-temperature storage, and provides an energy storage device using the nonaqueous electrolytic solution. The invention includes (1) a nonaqueous electrolytic solution of an electrolyte salt dissolved in a nonaqueous solvent, which comprises from 0.001 to 10% by mass of a compound represented by the following general formula (I), and (2) an energy storage device comprising a positive electrode, a negative electrode, and a nonaqueous electrolytic solution of an electrolyte salt dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution is the nonaqueous electrolytic solution of (1). (In the formula, Y represents a group -C(=O)- or a group -S(=O)2-; R3 and R4 each independently represent an aryl group having from 6 to 10 carbon atoms in which at least one hydrogen atom is substituted with a halogen atom, or R3 and R4 bonding to each other represent a cycloalkanediyl group or a benzenediyl group, having from 5 to 12 carbon atoms. R represents -C(R1)(R2)- or -L-; R1 and R2 each independently represent a hydrogen atom, a halogen atom, or an alkyl group having from 1 to 4 carbon atoms; and L represents a divalent linking group having from 1 to 6 carbon atoms and optionally substituted with a halogen atom.)