Fluorinated Battery Electrolyte for High-Voltage Thermal Stability
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Solution Overview
Problem
The energy density of commercially available secondary alkali metal ion batteries has approached its theoretical limit, and increasing battery voltage leads to oxidative degradation of positive electrode materials and electrolyte decomposition, causing rapid battery swelling and capacity degradation under high-temperature conditions.
Innovation Solution
An electrolyte using fluorinated solvent with specific additives like diethyl 2-(thiophene methyl)phosphonate (DTYP) and tetravinyl silane (TVSI) forms stable SEI and CEI films, enhancing thermal stability and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If battery voltage is increased to enhance energy density, then energy density is improved, but electrolyte decomposition and electrode material degradation occur
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate components (FEC, FPC) with specific fluorine-containing groups. These compositional changes increase the electrolyte's oxidation resistance and stability window, enabling it to withstand higher voltages (up to 4.8V) without decomposition, thus resolving the contradiction between energy density and electrolyte stability
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated cyclic carbonate (FEC/FPC) with conventional cyclic carbonate (EC) and chain carbonate (DMC, DEC). This composite formulation synergistically enhances both the stability and conductivity of the electrolyte, allowing high voltage operation while maintaining good electrochemical performance
2Use of energy by moving object
If battery voltage is increased to enhance energy density, then energy density is improved, but positive electrode material structure degrades
Solution Approach 1:
The fluorinated electrolyte components perform preliminary protective action by forming stable interface films on the positive electrode surface before degradation can occur. This pre-formed protective layer prevents direct contact between the high-voltage electrode material and the bulk electrolyte, reducing oxidative attacks and structure degradation during cycling
Solution Approach 2:
The introduction of fluorinated components changes the interfacial chemical environment at the electrode-electrolyte interface. The fluorine-containing groups modify the local chemical parameters (oxidation potential, interface stability) to create a more benign environment for the positive electrode material, reducing degradation even at high voltages
3Use of energy by moving object
If high voltage conditions are applied to increase energy density, then energy density is improved, but side reactions between electrolyte and electrodes intensify
Solution Approach 1:
The patent converts the potentially harmful high-voltage conditions into a beneficial effect by using the high voltage to drive the formation of a stable, protective interface film during initial cycling. This film, formed under controlled high-voltage conditions, subsequently prevents further harmful side reactions during normal operation, effectively converting the harmful high-voltage stress into a protective mechanism
4Temperature
If high-temperature conditions occur during battery operation, then battery performance is maintained, but electrolyte decomposition accelerates
Solution Approach 1:
The fluorinated cyclic carbonate components change the thermal parameters of the electrolyte system. The strong C-F bonds in FEC and FPC have higher bond energies than conventional carbonate solvents, raising the thermal decomposition temperature of the electrolyte. This parameter change enables the electrolyte to maintain stability at elevated temperatures where conventional electrolytes would decompose
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 improves high-temperature storage and cycling performance by inhibiting side reactions and reducing direct current resistance, maintaining battery integrity under high voltage conditions.
Implementation Method 1
through the synergistic effect of FEC and a specific content of FTYP, forms CEI film and SEI film with excellent thermal stability on the positive electrode interface and negative electrode interface respectively
Implementation Method 2
the strong electron-withdrawing ability of fluorine atoms is beneficial for the electrolyte to have higher oxidation stability, thereby significantly improving the high voltage resistance performance of the electrolyte
Data Source
AI summary
Disclosed are an electrolyte and a battery including the electrolyte, the electrolyte includes a solvent, a lithium salt and an additive. The solvent is constituted by a fluorinated solvent, the fluorinated solvent includes fluorinated ethylene carbonate (FEC), and the additive includes diethyl 2-(thiophene methyl)phosphonate (DTYP). The content of DTYP is 0.01% to 1.2% based on the total mass of the electrolyte. The electrolyte of the present disclosure, on basis of using fluorinated solvent as solvent to provide the battery with good high voltage performance, also through the synergistic effect of FEC and DTYP with specific content, forms SEI and CEI films with excellent thermal stability at the positive and negative electrode interfaces, thus enabling the battery to have both good high-temperature storage performance and high-temperature cycling performance.