Silicon Anode Copolymer Coating for SEI Layer Control
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Solution Overview
Problem
Silicon-based anode materials in lithium-ion batteries are prone to chemical reactions with the electrolyte, leading to the formation of a solid electrolyte interphase (SEI) layer, which reduces lithium ion storage capacity and prevents full charging of the cathode.
Innovation Solution
A copolymer comprising an ionically conductive polyethylene oxide (PEO) and an electrically conductive polymer like PEDOT, PANI, or PPy is used in conjunction with silicon, forming a block copolymer that enhances ionic and electrical conductivity while preventing electrolyte contact with silicon, thus minimizing SEI formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode active material, then lithium ion storage capacity is improved, but chemical reaction with electrolyte forms SEI layer which reduces capacity
Solution Approach 1:
The patent introduces a copolymer coating as an intermediary layer between silicon and the electrolyte. This copolymer consists of an ionically conductive polymer phase and an electrically conductive polymer phase, allowing lithium ion transport while preventing direct contact between silicon and electrolyte, thus blocking SEI layer formation while maintaining high lithium ion storage capacity
Solution Approach 2:
The patent uses a composite copolymer material combining two different polymer phases with complementary properties: one phase provides ionic conductivity for lithium ion transport, while the other phase provides electrical conductivity and physical barrier properties to prevent electrolyte access to silicon, thereby resolving the contradiction between capacity and SEI formation
2Object-affected harmful factors
If copolymer coating is applied to prevent electrolyte contact, then SEI formation is reduced, but device complexity increases
Solution Approach 1:
The patent employs a copolymer material that integrates multiple functions (ionic conductivity, electrical conductivity, and protective barrier properties) into a single coating layer, simplifying the overall electrode structure while effectively preventing electrolyte accumulation on silicon surface
Solution Approach 2:
The copolymer coating performs multiple functions simultaneously: it acts as an ionic conductor for lithium ion transport, an electrical conductor for electron transport, and a protective barrier against electrolyte contact, thereby reducing SEI formation without significantly increasing device complexity
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 copolymer structure maintains high lithium ion storage capacity and electrical conductivity, prevents electrolyte accumulation on the silicon surface, and allows for volume expansion during lithium intercalation, maintaining battery performance.
Implementation Method 1
During a discharging process, the lithium ions migrate within the battery cell from the anode to the cathode
Implementation Method 2
the second polymer being electrically conductive. The electrical conductivity of the second polymer is, in this case, preferably at least 10^-4 S/cm
Implementation Method 3
The silicon as the active material of the anode is exposed to attacks from chemical reactions with the liquid electrolyte
Data Source
AI summary
An electrode for a battery cell, including an active material which contains silicon and which contains a first polymer which is ionically conductive. The active material contains in this case a copolymer, which includes the first polymer and a second polymer, the second polymer being electrically conductive. A battery cell which includes at least one electrode is also described.