Non-Aqueous Battery Electrolyte for Stable Silicon Anode SEI
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Solution Overview
Problem
Silicon-based negative electrodes in lithium secondary batteries experience significant volume changes during charge and discharge, leading to degradation, cracking, and continuous electrolyte decomposition due to the instability of the solid electrolyte interphase (SEI) layer, which limits their cycle life and high-temperature storage characteristics.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, an organic solvent, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI) as the first additive, and tetravinylsilane as the second additive, which form a stable SEI layer on the negative electrode, suppressing side reactions and improving high-temperature storage and cycle life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to improve energy per weight, then capacity per weight increases, but volume change during charge and discharge causes SEI layer destruction and continuous electrolyte decomposition
Solution Approach 1:
The patent applies preliminary action by introducing a film-forming additive into the electrolyte composition before battery operation. This additive proactively forms a stable protective film on the silicon-based negative electrode surface during initial cycles, preventing the subsequent destruction of the SEI layer that would normally occur due to silicon's volume expansion. The protective film is formed in advance to withstand the mechanical stress of silicon expansion during charge-discharge cycles.
Solution Approach 2:
The patent uses an intermediary substance (film-forming additive) that mediates between the silicon-based negative electrode and the electrolyte. This additive acts as a buffer layer that accommodates the volume changes of silicon during lithiation and delithiation, preventing direct contact between the expanding silicon and the electrolyte, thereby avoiding continuous electrolyte decomposition while still allowing lithium ion transport.
2Use of energy by moving object
If silicon-based material undergoes alloying reaction with lithium to achieve high capacity, then energy density improves, but physical change in electrode structure causes degradation and cracking
Solution Approach 1:
The patent employs a flexible protective film formed by the film-forming additive on the silicon-based negative electrode surface. This thin film acts as a flexible shell that can accommodate the volume expansion and contraction of silicon during charge-discharge cycles without cracking, thereby maintaining electrode structural integrity while allowing high capacity lithium alloying reactions to occur.
Solution Approach 2:
The patent applies beforehand cushioning by having the film-forming additive create a protective cushioning layer on the silicon surface before the electrode undergoes repeated expansion and contraction. This pre-formed protective layer absorbs the mechanical stress of volume changes, preventing electrode degradation and cracking that would otherwise occur due to the rigid structure of silicon during high-capacity alloying reactions.
3Productivity
If SEI layer is formed on silicon surface during charge and discharge, then initial capacity is achieved, but volume change destroys SEI layer causing continuous electrolyte decomposition
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance between the silicon-based negative electrode and the electrolyte. This additive forms a stable protective film that serves as a mediator, allowing initial capacity to be achieved through SEI formation while simultaneously preventing the destruction of this layer during subsequent volume changes, thereby eliminating continuous electrolyte decomposition.
Solution Approach 2:
The patent applies parameter changes by modifying the electrolyte composition to include specific film-forming additives that change the properties of the SEI layer. These additives alter the chemical composition and mechanical properties of the SEI film, making it more flexible and stable against volume changes, thus preventing electrolyte decomposition while maintaining initial capacity.
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 effectively forms a robust and stable SEI layer, reducing gas generation, maintaining battery performance, and enhancing high-temperature storage stability and cycle life by preventing electrolyte decomposition and resistance increase.
Implementation Method 1
a first additive, and a second additive, wherein the first additive is lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), and the second additive is tetravinylsilane
Implementation Method 2
capable of forming a stable film on a surface of a negative electrode... a side reaction between the negative electrode and the electrolyte solution may be suppressed
Implementation Method 3
there is a limitation in that electrolyte decomposition continuously occurs on the exposed surface of the active material due to the SEI layer destroyed during charge and discharge
Data Source
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AI summary
The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same, and particularly, to a non-aqueous electrolyte solution for a lithium secondary battery, which includes a lithium salt, an organic solvent, a first additive, and a second additive, wherein the first additive is lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide, and the second additive is tetravinylsilane, and a lithium secondary battery including the same.