Electrolyte Additives for High-Temperature Battery Stability
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Solution Overview
Problem
Nonaqueous electrolyte cells suffer from severe deterioration at high temperatures, particularly above 45°C, which limits their durability and performance in applications like electric vehicles and power storage systems, with existing additives either failing to provide sufficient high-temperature stability or causing gas generation and performance deterioration.
Innovation Solution
An electrolyte for nonaqueous electrolyte cells is developed by combining specific compound groups, including bis(oxalato)borate, difluoro(oxalato)borate, tris(oxalato)phosphate, and sulfonate-containing imide salts, which form a protective film on electrodes to enhance lithium ion conductivity and prevent decomposition, thereby improving cycle characteristics and storage stability without causing swelling or performance deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylene carbonate is added to form a protective film on the electrode surface, then electrolyte decomposition is suppressed, but lithium ion conductivity decreases due to increased internal resistance
Solution Approach 1:
The patent combines vinylene carbonate (0.01-5 mass%) with boron-phosphorus complex salts having oxalic acid groups (0.01-5 mass%) to create a composite electrolyte system. This composite approach allows the vinylene carbonate to form a protective film while the boron-phosphorus complex salts modify the film properties to maintain lithium ion conductivity, thus resolving the contradiction between film protection and ion transport.
Solution Approach 2:
The patent optimizes the concentration parameters of both vinylene carbonate and boron-phosphorus complex salts within specific ranges (0.01-5 mass% each). By controlling these parameters, the protective film's properties are tuned to achieve both decomposition suppression and acceptable lithium ion conductivity, balancing the conflicting requirements.
2Reliability
If boron and phosphorus complex salts having oxalic acid group are added to improve high-temperature cycle characteristics, then output characteristics improve, but gas generation occurs causing swelling and performance deterioration
Solution Approach 1:
The patent utilizes the film-forming reaction of boron-phosphorus complex salts, which normally consumes the additive, to create a protective interface that actually suppresses further decomposition reactions. The controlled gas generation from initial film formation is converted into a beneficial effect by creating a stable protective layer that prevents more severe decomposition and swelling during cycling.
Solution Approach 2:
The patent carefully controls the concentration of boron-phosphorus complex salts within 0.01-5 mass% to optimize the balance between film-forming effect and gas generation. This parameter optimization ensures sufficient film formation for protection while limiting excessive gas production that would cause swelling.
3Reliability
If the amount of boron and phosphorus complex salts is increased to enhance film-forming effect, then high-temperature stability improves, but decomposition reactions increase causing gas generation
Solution Approach 1:
The patent creates a synergistic composite system where vinylene carbonate and boron-phosphorus complex salts work together. The vinylene carbonate provides base film formation while the boron-phosphorus complex salts enhance the film's protective properties. This composite approach achieves high-temperature stability without requiring excessive amounts of either additive, thus limiting decomposition 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 combined compound groups form a strong protective film that enhances high-temperature durability and suppresses gas generation, leading to improved cycle characteristics and storage stability in nonaqueous electrolyte cells, suitable for large-size power applications without performance degradation.
Implementation Method 1
This method prevents an electrolyte from decomposing on the surface of an electrode by coating the electrode with a polymer film by polymerization of vinylene carbonate
Implementation Method 2
a nonaqueous electrolyte or a nonaqueous electrolyte coagulated by a gelation agent is used as an ionic conductor
Data Source
AI summary
Disclosed is an electrolyte for nonaqueous electrolyte cells, which contains a nonaqueous organic solvent and a solute. This electrolyte is characterized by containing as additives at least one compound selected from a first compound group consisting of bis(oxalato)borate, difluoro(oxalato)borate, tris(oxalato)phosphate, difluorobis(oxalato)phosphate, and tetrafluoro(oxalato)phosphate, and at least one compound selected from a second compound group consisting of a sulfonate group-containing imide salt, which is represented by the general formula M[R1OSO2NSO2OR2]n, and a phosphoryl group-containing imide salt, which is represented by the general formula M[R3R4OPNPOR5R6]m. This electrolyte provides nonaqueous electrolyte cells with high-temperature durability without causing swelling and performance deterioration of batteries.