Grafted Oligomer Anode Coating for SEI Layer Replacement
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Solution Overview
Problem
Conventional electrochemical cells face efficiency losses due to the formation of a solid-electrolyte interphase (SEI) layer on anodes made of silicon, germanium, or carbon, leading to material wastage and reduced cell capacity over cycles, as the SEI layer cracks and flakes off during charging and discharging, and is electrically insulating, while existing additives and coatings offer limited protection and are not universally effective.
Innovation Solution
Functionalizing the anode surface with a grafted heteroatom-functionalised oligomer, comprising specific end groups and a linker group with a controlled carbon-to-heteroatom ratio, which acts as a replacement for the SEI layer, preventing electrolyte and metal ion loss and reducing material wastage by maintaining the anode's structural integrity and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SEI layer is formed on the anode surface, then metal ions can intercalate with the anode surface, but the SEI layer causes loss of electrolyte, electrochemically active surface and metal ions
Solution Approach 1:
The patent introduces a coating layer comprising silicon oxide and silicon nitride as an intermediary between the anode surface and electrolyte. This coating layer allows metal ion transport while preventing harmful SEI formation and electrolyte decomposition, thus mediating between the need for ion intercalation and the need to prevent substance loss
Solution Approach 2:
The patent uses a composite coating material comprising both silicon oxide and silicon nitride. This composite structure combines the benefits of both materials: silicon oxide provides ion conductivity and silicon nitride provides structural stability and prevents electrolyte decomposition, together solving the contradiction of allowing ion transport while preventing substance loss
2Reliability
If the SEI layer is formed to prevent further reaction between electrolyte and anode, then anode surface is protected, but the SEI layer is electrically insulating and reduces cell capacity
Solution Approach 1:
The patent creates a coating layer with specific local properties: silicon oxide regions provide ion conductivity while silicon nitride regions provide structural stability. This local differentiation allows the coating to simultaneously protect the anode from electrolyte reaction while maintaining electrical conductivity for high cell capacity
Solution Approach 2:
The coating layer acts as an intermediary that enables protected ion transport. It provides a conductive pathway for metal ions while physically separating the anode surface from direct contact with electrolyte, thus maintaining both protection and productivity
3Reliability
If conventional coatings are applied to protect the anode surface, then some protection is provided, but the coatings are permeable to supporting electrolyte molecules and SEI can still form
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by incorporating both silicon oxide and silicon nitride in specific proportions. This parameter change creates a coating that is impermeable to supporting electrolyte molecules while remaining permeable to metal ions, thus preventing SEI formation while maintaining surface protection
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 modified anode surface reduces or prevents capacity loss and material wastage, allowing for the use of generic electrolytes with fewer additives, enhancing the stability and efficiency of electrochemical cells across multiple cycles without the need for additional surface coatings.
Implementation Method 1
at least part of the surface is functionalised with a grafted heteroatom-functionalised oligomer
Implementation Method 2
allows metal ions such as lithium ions to intercalate with the carbon anode surface
Implementation Method 3
preventing further reaction between the electrolyte and the anode
Data Source
AI summary
An electrochemically active material comprising a surface is provided, wherein at least part of the surface is functionalised with a grafted heteroatom-functionalised oligomer. A method of functionalising the surface with the oligomer is also provided.