Silicon Negative Electrode Thermal Stability via Chain Carbonate Electrolyte
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode face challenges in maintaining cycle characteristics and thermal stability due to volume variation during charging/discharging, leading to deterioration of battery performance.
Innovation Solution
Incorporating a negative electrode with silicon and an electrolytic solution containing chain carbonate and cyclic carbonate, specifically diethyl carbonate, which improves cycle characteristics and thermal stability by reducing heat generation during charging/discharging cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to increase capacity, then energy density is improved, but volume variation during charging/discharging causes particle miniaturization and contact property deterioration
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by specifying chain carbonates with carbon numbers of 4 or more (such as diethyl carbonate, dipropyl carbonate) and limiting methyl carbonate content to 5 vol% or less. These parameter changes in the electrolyte composition stabilize the solid electrolyte interface film on silicon particles, preventing volume variation-induced deterioration and maintaining cycle characteristics while utilizing silicon's high capacity.
2Power
If silicon is used as negative electrode material, then discharge electric potential is reduced, but volume variation causes contact properties between current collector and conductive auxiliary agent to decrease
Solution Approach 1:
The patent modifies the electrolytic solution composition parameters by using chain carbonates with carbon numbers of 4 or more and limiting methyl carbonate, which stabilizes the solid electrolyte interface film. This stabilization prevents volume variation during charging/discharging, thereby maintaining contact properties between the current collector and conductive auxiliary agent on the silicon-based negative electrode.
3Productivity
If methyl carbonate is used in electrolytic solution to improve ion conductivity, then battery performance is enhanced, but it promotes decomposition of solid electrolyte interface film on silicon electrode
Solution Approach 1:
The patent changes the electrolytic solution composition by limiting methyl carbonate content to 5 vol% or less and introducing chain carbonates with carbon numbers of 4 or more (such as diethyl carbonate). This parameter change reduces the decomposition of the solid electrolyte interface film on silicon electrodes while maintaining adequate ion conductivity through the alternative carbonate components.
4Productivity
If chain carbonate with short carbon number is used, then electrolyte performance is improved, but negative electrode stability is insufficient
Solution Approach 1:
The patent changes the chain carbonate parameter by specifying carbon numbers of 4 or more (such as diethyl carbonate with 4 carbons, dipropyl carbonate with 6 carbons). This parameter change in the electrolyte composition provides sufficient negative electrode stability by forming a more stable solid electrolyte interface film, while still maintaining good electrolyte performance through the chain carbonate structure.
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 use of silicon in the negative electrode with a suitable electrolytic solution composition enhances cycle characteristics and thermal stability, preventing deterioration and improving battery performance.
Implementation Method 1
an amount of heat generation, which is measured by a differential scanning calorimeter within a range of 210 to 380° C. during full charge, is 850 J/g or less
Implementation Method 2
an amount of heat generation, which is measured by a differential scanning calorimeter within a range of 210 to 380° C. during full charge
Data Source
AI summary
The negative electrode is formed from silicon, an amount of heat generation in a negative electrode, which is measured by a differential scanning calorimeter within a range of 210 to 380° C. during full charge, is 850 J/g or less, and a cyclic carbonate including ethylene carbonate and a chain carbonate which has a chemical formula expressed by R1—O—CO—OR2, and in which R1 and R2 represent an alkyl group having a carbon number of 2 or more are used for an electrolytic solution.