SiOx Anode Polycarbonate Coating for Stable SEI Cycling
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Solution Overview
Problem
The cycle performance of SiOx-based negative electrode materials in lithium-ion batteries is poor due to repeated destruction and reconstruction of the solid electrolyte interface (SEI) film, which limits their commercial application.
Innovation Solution
A composite negative electrode material is developed with a SiOx-based active material coated with a polycarbonate layer, which increases the toughness and stability of the SEI film by participating in its formation during charging and discharging, thereby improving the battery's cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx-based material is used as negative electrode material, then capacity is improved, but cycle performance deteriorates due to repeated destruction and reconstruction of SEI film
Solution Approach 1:
The patent applies preliminary action by pre-coating the SiOx-based active material surface with polycarbonate before battery assembly. This pre-formed coating layer serves as a template for SEI film formation, allowing the SEI to be established in advance with improved stability rather than forming repeatedly during cycling. The polycarbonate coating is applied through dissolution in electrolyte followed by controlled polymerization, creating a stable foundation that prevents subsequent SEI film destruction and reconstruction.
Solution Approach 2:
The patent uses polycarbonate as an intermediary substance between the SiOx-based active material and the electrolyte. This intermediary layer mediates the interaction between the active material and electrolyte, controlling SEI film formation by providing a stable polymer matrix that incorporates into the SEI structure. The polycarbonate acts as a bridge that allows ion transport while preventing direct contact between electrolyte and SiOx surface, thereby stabilizing the SEI film and improving cycle performance.
2Reliability
If polycarbonate coating layer is added to SiOx-based active material, then SEI film stability is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the polymerization process parameters to achieve optimal polycarbonate coating thickness and molecular weight. By adjusting polymerization time, temperature, and catalyst concentration, the coating layer parameters are optimized to provide sufficient SEI stabilization without excessive thickness that would hinder ion transport. The polycarbonate content and coating thickness are carefully controlled to balance SEI stability improvement with minimal impact on battery performance and 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 polycarbonate coating enhances the stability of the SEI film, leading to improved cycle performance and extended service life of lithium-ion batteries, while also being cost-effective and environmentally friendly.
Implementation Method 1
polycarbonate firmly coated on the surface of the SiOx-based active material protects the SiOx-based active material while participating in the formation of the SEI film during a charging and discharging process
Implementation Method 2
polycarbonate firmly coated on the surface of the SiOx-based active material protects the SiOx-based active material
Data Source
AI summary
The present application provides a composite negative electrode material of a lithium ion battery, a preparation method thereof and the use thereof in a lithium ion battery. The composite negative electrode material includes a SiOx-based active material and a polycarbonate coating layer coated on a surface of the SiOx-based active material. The method includes: (1) preparing a monomer solution of unsaturated carbonate; (2) polymerizing the monomer in presence of a polymerization catalyst to obtain a polymer solution; and (3) adding a SiOx-based active material, water and a polymer catalyst to the polymer solution, and further polymerizing to coat the SiOx-based active material, to obtain the composite negative electrode material.