Lithium-Ion Battery Electrolyte Additives for Silicon Anode Stability
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Solution Overview
Problem
Lithium-ion batteries with silicon-based negative electrodes face challenges due to poor conductivity and significant volume expansion, leading to electrode separation and side reactions with the electrolytic solution, which affects electrical performance and cycle life.
Innovation Solution
An electrolytic solution is developed containing additives A and B, which form a dense, tough SEI film on electrode surfaces, preventing volume expansion and side reactions, comprising specific compounds that reduce impedance and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to achieve high capacity, then the theoretical capacity increases significantly, but the volume expansion reaches 400% causing electrode separation and poor electrical performance
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable SEI film on the silicon negative electrode surface before full cycling begins. The electrolytic solution contains specific additives (compounds with Formula I and Formula II) that preferentially react with silicon during initial cycles to create a protective interface layer. This pre-formed SEI film prevents subsequent volume expansion from causing electrode separation, allowing the high capacity of silicon (4200 mAh/g) to be utilized without the 400% expansion problem that would otherwise occur.
2Quantity of substance
If silicon material continuously intercalates and de-intercalates lithium during cycling, then high capacity is achieved, but the volume expansion effect causes separation from current collector and affects electrical performance
Solution Approach 1:
The patent uses an intermediary approach by introducing a third component - a protective SEI film formed from electrolytic solution additives - that mediates between the silicon negative electrode and the electrolyte. This intermediary SEI film, created by compounds with Formula I and Formula II, allows lithium intercalation/deintercalation to proceed (maintaining high capacity) while preventing the mechanical stress of volume expansion from causing separation from the current collector. The SEI film acts as a buffer that preserves electrical performance during repeated cycling.
3Quantity of substance
If no protective film is formed on silicon negative electrode, then high capacity utilization is achieved, but side reactions between negative electrode material and electrolytic solution increase
Solution Approach 1:
The patent applies local quality by creating a specialized protective SEI film with specific chemical composition and structure at the local interface between the silicon negative electrode and the electrolyte. The electrolytic solution contains additives with Formula I and Formula II that concentrate at the electrode surface to form this locally optimized protective layer. This local modification allows the bulk silicon material to maintain high capacity utilization (4200 mAh/g) while the local SEI film interface prevents harmful side reactions with the electrolyte.
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 suppresses volume expansion, reduces gas production at high temperatures, and maintains cycling performance, improving the overall capacity retention and storage life of lithium-ion batteries.
Implementation Method 1
forming a dense SEI film with high toughness on surfaces of positive and negative electrode materials and preventing side reactions between the electrode materials and the electrolytic solution
Data Source
AI summary
The present disclosure relates to the technical field of lithium-ion battery, and particularly, to an electrolytic solution and a lithium-ion battery including the electrolytic solution. The electrolytic solution includes additives, and the additives include an additive A and an additive B. The additive A forms a film on the surface of the positive electrode and effectively prevents interface side reactions at the positive electrode. Comparing with the additive A, the additive B is preferentially reduced to form a film at the negative electrode, avoiding an increase in impedance and deterioration of cycling dynamic performance, etc., caused by film formation of the additive A on the negative electrode. The combination of the additive A and additive B imparts the battery with a reduced gas production, a higher capacity retention rate and a lower impedance at high temperature.