Silicon Anode Battery Electrolyte for Cycle Life
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Solution Overview
Problem
Lithium ion secondary batteries with high-capacity negative electrode active materials like silicon face deterioration due to electrolyte solution decomposition, leading to poor cycle characteristics.
Innovation Solution
A lithium ion secondary battery comprising a negative electrode with silicon as the active material and an electrolyte solution containing a fluorinated ether compound, an open-chain sulfone compound, and cyclic carbonate, along with supporting salts LiPF6, LiFSI, and LiBOB, where the LiBOB content is 0.2 mass % or more, to enhance cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity negative electrode active materials like silicon are used, then battery capacity and energy density are improved, but cycle characteristics deteriorate due to electrolyte solution decomposition
Solution Approach 1:
The patent introduces a specific electrolyte solution composition as an intermediary between the silicon-based negative electrode and the environment. The electrolyte contains LiBOB (0.05-2 mass%), fluoroethylene carbonate (1-30 mass%), and ethyl methyl sulfone (70-95 mass%), which together form a protective interface that mediates the interaction between silicon and electrolyte, preventing harmful decomposition while maintaining high capacity
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte solution by incorporating specific concentrations of LiBOB, FEC, and EMS. This parameter modification transforms the electrolyte's properties to be more compatible with silicon-based electrodes, reducing decomposition and improving cycle characteristics while preserving high capacity
2Use of energy by moving object
If silicon-based negative electrode active material is used, then energy density is improved, but electrolyte solution decomposition occurs leading to poor cycle characteristics
Solution Approach 1:
The electrolyte solution acts as a protective intermediary layer between the silicon-based negative electrode and the external environment. The specific composition of LiBOB, FEC, and EMS creates a stable interface that prevents direct harmful interactions, allowing high energy density to be achieved without electrolyte decomposition
Solution Approach 2:
The patent converts the potentially harmful decomposition reaction into a beneficial process by controlling the electrolyte composition. The initial formation cycle creates a protective SEI layer on the silicon surface that prevents further decomposition, transforming what would be a harmful continuous reaction into a beneficial one-time protective mechanism
Data Source
AI summary
A lithium ion secondary battery having high energy density and being excellent in cycle characteristics is provided. The present invention relates to a lithium ion secondary battery comprising: a negative electrode active material comprising a material comprising silicon as a constituent element; and an electrolyte solution comprising: a non-aqueous solvent comprising a fluorinated ether compound, an open-chain sulfone compound, and a cyclic carbonate compound, and a supporting salt comprising LiPF6, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalato)borate (LiBOB); wherein the content of LiBOB in the electrolyte solution is 0.2 mass % or more.