Lithium Battery Electrolyte Additives for High-Temperature Cycling
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Solution Overview
Problem
Lithium ion batteries face challenges in maintaining high-temperature and low-temperature characteristics due to increased viscosity of non-aqueous electrolyte solutions, leading to reduced durability and capacity, especially at high driving voltages.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, comprising LiPF6, a second lithium salt, an oligomer additive, and a mixed additive of lithium difluorophosphate, fluorobenzene, and tetravinylsilane, which improves wetting and reduces interfacial resistance by forming a stable film on the electrode surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the concentration of lithium salt in the non-aqueous electrolyte solution is increased, then the capacity and output of the battery are improved, but the viscosity of the electrolyte solution increases significantly, reducing wetting and durability at high and low temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carboxylate additive (Formula 1) with controlled molecular weight (1,000-10,000) and functional groups. This additive modifies the electrolyte's physical properties (viscosity, wetting) while maintaining high lithium ion concentration, resolving the contradiction between capacity and temperature characteristics
Solution Approach 2:
The cyclic carboxylate acts as an intermediary substance that mediates between the high concentration lithium salt and the electrode/separator. It forms a stable interfacial film that improves wetting and reduces resistance, allowing high lithium ion concentration to be maintained without the adverse viscosity effects
2Productivity
If the concentration of lithium salt is increased to achieve high capacity, then the battery output is improved, but side reactions between electrode active material and electrolyte increase, degrading battery life
Solution Approach 1:
The cyclic carboxylate additive performs preliminary protective action by forming a stable passivation film on the electrode surface before significant side reactions can occur. This pre-formed protective layer prevents harmful interactions between high-concentration lithium salt and electrode materials, extending battery life while maintaining high capacity
Solution Approach 2:
The patent converts the potentially harmful high concentration of lithium salt into a beneficial effect by using the cyclic carboxylate to control its reactivity. The additive transforms the aggressive high-concentration electrolyte into a controlled system that provides high capacity without excessive side reactions, turning a harmful condition into a beneficial one
3Power
If high voltage (4.45 V or more) is used to increase battery output, then the energy density is improved, but electrolyte wetting is significantly reduced due to increased viscosity
Solution Approach 1:
The patent changes the molecular parameters of the electrolyte by adding cyclic carboxylate with specific molecular weight range (1,000-10,000) and functional groups. This modifies the electrolyte's viscosity and surface tension properties, improving wetting capability while maintaining the high voltage (4.45 V or more) operating condition
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 enhances lithium ion mobility, improves wetting, and stabilizes the electrolyte, resulting in improved high-temperature and low-temperature characteristics, extended cycle life, and increased capacity retention.
Implementation Method 1
an additive which may form a stable film on a surface of an electrode and may simultaneously improve wetting by reducing interfacial resistance with the electrode
Implementation Method 2
an electrolyte solution as a medium for transferring lithium ions
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, a non-aqueous electrolyte solution for a lithium secondary battery includes an organic solvent, LiPF6 as a first lithium salt, a second lithium salt excluding the LiPF6, an oligomer represented by Formula 1, as a first additive, and a mixed additive of lithium difluorophosphate (LiDFP), fluorobenzene (FB), and tetravinylsilane (TVS), as a second additive.