Silicon Negative Electrode Binder-Electrolyte for Stable Cycling
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Solution Overview
Problem
Current lithium-ion secondary batteries face challenges in increasing capacity and improving charge-discharge cycle performance, particularly with silicon-based negative electrodes which are prone to side reactions and instability during charging and discharging.
Innovation Solution
A secondary battery design incorporating a negative electrode active material layer with silicon particles and a binder having a carboxy group, where the weight ratio of the binder to silicon particles is between 0.05 and 10, and an electrolyte solution containing lithium bis(fluorosulfonyl)imide and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, which stabilizes lithium ions and protects silicon particles from side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active materials to increase capacity, then the battery capacity is improved, but the charge-discharge cycle performance deteriorates due to side reactions and instability during charging and discharging
Solution Approach 1:
The patent introduces an ionic liquid as an intermediary substance between the silicon-based negative electrode and the electrolyte. This ionic liquid forms a stable interface layer that mediates the interaction between silicon and the electrolyte, preventing direct harmful reactions while allowing lithium ion transport. The ionic liquid acts as a protective mediator that resolves the contradiction between maintaining high capacity and achieving stable cycling performance
Solution Approach 2:
The patent changes the chemical and physical parameters of the electrolyte system by incorporating ionic liquids with specific properties (high ionic conductivity, electrochemical stability). This parameter change transforms the electrolyte from a conventional organic solvent system to an ionic liquid-based system, which provides better stability with silicon-based electrodes while maintaining high lithium ion conductivity, thus resolving the capacity-stability contradiction
2Use of energy by moving object
If silicon particles are used in the negative electrode to achieve higher capacity, then the energy storage capability is improved, but the stability during charging and discharging deteriorates due to side reactions
Solution Approach 1:
The ionic liquid serves as a protective intermediary layer between silicon particles and the electrolyte, preventing direct contact and harmful side reactions. This intermediary layer maintains the compositional stability of silicon particles during electrochemical cycling while allowing the high energy storage capability of silicon to be utilized
Solution Approach 2:
The patent creates a composite system combining silicon particles with ionic liquid electrolyte, forming a stable composite structure where the ionic liquid matrix protects the silicon particles. This composite approach maintains the high capacity advantage of silicon while providing the stability needed for practical application
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 the stability and performance of silicon-based negative electrodes, leading to a reliable and efficient charge-discharge cycle, thereby improving the overall performance and longevity of the secondary battery.
Implementation Method 1
at least part of the surfaces of the silicon particles can be covered and protected with the binder
Implementation Method 2
In the electrolyte solution, lithium ions are stabilized by solvation
Data Source
AI summary
A novel secondary battery that is highly convenient, useful, or reliable can be provided. The secondary battery includes a positive electrode active material layer, a negative electrode active material layer, and a separator. The separator is interposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer includes silicon particles and a binder. The weight ratio of the binder to the silicon particles is greater than or equal to 0.05 and less than or equal to 10. The binder has a carboxy group. The bulk specific gravity of the silicon particles is greater than or equal to 0.02 g/cm3 and less than or equal to 0.5 g/cm3.