Covalent Oligomer Surface Coating for Low-Loss Battery Anodes
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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 anode surfaces, leading to capacity reduction, material wastage, and the need for electrolyte additives, which are not effective in preventing SEI layer cracking and thickening.
Innovation Solution
An electrochemically active material with a surface covalently bonded to a linear or branched oligomeric moiety, selected from specific formulas, is used to prevent SEI layer formation, enhancing capacity retention and reducing interaction between the electrolyte and the anode surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional anode surface (silicon, germanium, or carbon) is used, then the electrochemical cell can operate, but a solid electrolyte interphase (SEI) layer forms causing first cycle loss and reduced efficiency
Solution Approach 1:
The anode surface is pre-modified by covalently bonding oligomeric moieties to the surface before electrochemical operation begins. This preliminary surface modification creates a controlled interface that prevents uncontrolled SEI layer formation during the first cycle, thereby reducing first cycle loss while maintaining reliable cell operation.
Solution Approach 2:
The oligomeric moiety acts as an intermediary layer between the anode surface (silicon, germanium, or carbon) and the electrolyte. This intermediate layer mediates the interaction between the electrode and electrolyte, allowing ion transport while preventing direct contact that would lead to harmful SEI formation and associated energy losses.
2Reliability
If an SEI layer forms on the anode surface, then metal ions can intercalate with the electrode, but the SEI layer contributes to material wastage and reduced cell capacity
Solution Approach 1:
The covalently bonded oligomeric moiety serves as an intermediary layer that enables metal ion intercalation while preventing direct electrolyte-anode contact. This intermediary function allows necessary electrochemical reactions to proceed while blocking the pathway that leads to material wastage through uncontrolled SEI formation.
Solution Approach 2:
The oligomeric moiety forms a thin film on the anode surface that is flexible enough to accommodate volume changes during lithiation/delithiation cycles. This thin film structure maintains ion transport pathways while preventing the thickening and cracking that characterizes conventional SEI layers, thereby reducing material wastage.
3Strength
If electrolyte additives are used to improve SEI layer strength and flexibility, then SEI formation is partially improved, but the additives cannot prevent SEI layer cracking and thickening
Solution Approach 1:
Instead of relying on electrolyte additives to modify SEI properties during operation, the invention performs preliminary modification of the anode surface by covalently bonding oligomeric moieties before cell assembly. This preliminary action creates a stable, controlled interface that prevents the formation of weak and crack-prone SEI layers, eliminating the need for electrolyte additives.
Solution Approach 2:
The covalently bonded oligomeric moiety acts as a permanent intermediary layer that provides consistent mechanical strength and compositional stability. Unlike electrolyte additives that are consumed and variable in effectiveness, this intermediary layer remains stable throughout cycling, preventing SEI cracking and thickening while maintaining composition stability.
4Reliability
If the SEI layer thickens due to continuous formation, then more anode surface is exposed to electrolyte, but this exposes more surface to form additional SEI layer causing further material wastage
Solution Approach 1:
The covalently bonded oligomeric moiety forms a flexible thin film that accommodates volume expansion and contraction during lithiation and delithiation cycles. This flexibility prevents the film from cracking and peeling off, maintaining a stable barrier that prevents continuous SEI formation and the associated material wastage.
Solution Approach 2:
The oligomeric moiety intermediary layer remains intact during cycling, continuously mediating between the anode surface and electrolyte. This stable intermediary prevents the cycle of exposure and re-formation that leads to material wastage, as the intermediary itself does not crack or peel like conventional SEI layers.
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 reduces capacity loss and material wastage by preventing SEI layer formation, improving specific capacity and eliminating the need for electrolyte additives, while maintaining compatibility with existing battery components.
Implementation Method 1
a linear or branched oligomeric moiety is covalently bonded to the surface
Implementation Method 2
Surface modification... An electrochemically active material with a surface covalently bonded to a linear or branched oligomeric moiety
Data Source
AI summary
An electrochemically active material comprising a surface is provided, wherein the surface comprises an oligomer. A method of functionalising the surface with the oligomer is also provided.