Silicon Alloy Electrode Polymer Coating Expansion Control
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Solution Overview
Problem
Lithium secondary batteries with silicon-based alloy electrodes face challenges due to volumetric expansion during charging and discharging, leading to decreased capacity retention and lifespan, as the expansion disrupts the conduction path and forms a solid electrolyte interface (SEI) film, reducing efficiency and capacity.
Innovation Solution
A coating film containing a polymer with a 3,4-ethylenedioxythiophene repeating unit and an oxyalkylene repeating unit is applied to the silicon-based alloy electrode active material at low temperature, forming a conductive and ion-conductive layer that suppresses volumetric expansion and enhances conductivity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based alloy is used as electrode active material, then capacity is improved, but volumetric expansion occurs leading to decreased lifespan and capacity retention
Solution Approach 1:
A coating film comprising a polymer including a 3,4-ethylenedioxythiophene repeating unit and an oxyalkylene repeating unit is formed on the silicon-based alloy surface. This thin film layer suppresses volumetric expansion of the silicon-based alloy during charging and discharging cycles, preventing disruption of conduction paths and formation of excessive SEI film, thereby improving lifespan and capacity retention while maintaining high capacity.
Solution Approach 2:
The electrode active material is constructed as a composite structure with the silicon-based alloy core and the polymer coating film shell. This composite material combines the high capacity of silicon-based alloy with the expansion-suppressing properties of the polymer coating, achieving both high capacity and long lifespan.
2Duration of action of stationary object
If a coating film is applied to suppress volumetric expansion, then lifespan is improved, but manufacturing complexity increases
Solution Approach 1:
The coating film is formed through low-temperature processing, changing the temperature parameter from conventional high-temperature treatments to low-temperature conditions. This enables the formation of the functional coating film while simplifying the manufacturing process and reducing energy consumption.
3Ease of manufacture
If low temperature processing is used for coating, then manufacturing ease is improved, but coating effectiveness may be reduced
Solution Approach 1:
The polymer material is specifically selected with appropriate molecular weight and composition ratios to enable effective coating formation at low temperatures. The 3,4-ethylenedioxythiophene repeating unit provides conductivity while the oxyalkylene repeating unit enables low-temperature processing, achieving both manufacturing ease and coating effectiveness.
Solution Approach 2:
The polymer is designed as a composite structure combining conductive 3,4-ethylenedioxythiophene units with flexible oxyalkylene units. This composite material structure enables the coating to form effectively at low temperatures while maintaining sufficient thickness and functionality to suppress volumetric expansion.
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 coated electrode exhibits improved conductivity and capacity retention, with the polymer film effectively controlling expansion and preventing side reactions, resulting in enhanced lifespan and performance of lithium secondary batteries.
Implementation Method 1
the polymer film effectively controlling expansion
Implementation Method 2
forming a conductive and ion-conductive layer
Data Source
AI summary
In an aspect, an electrode active material for a lithium secondary battery, the electrode active material including a silicon-based alloy and a coating film containing a polymer that includes a 3,4-ethylenedioxythiophene repeating unit and an oxyalkylene repeating unit, coated on the surface of the silicon-based alloy are provided.