Coated Silicon Anode Material for Swelling-Resistant Li-Ion Batteries
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face issues with volumetric swelling during lithium intercalation, leading to degradation of charge/discharge cycle life due to cracking and mis-contact with the current collector.
Innovation Solution
A negative electrode active material comprising silicon particles with a full width at half maximum (FWHM) of 2-10 in the particle diameter distribution and a coating layer of carbon and/or polymer, which prevents pulverization and side reactions, enhancing conductivity and reaction reversibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based materials are used as negative electrode active materials to achieve high theoretical capacity, then capacity is improved, but volumetric swelling occurs during lithium intercalation leading to cracking and degradation of charge/discharge cycle life
Solution Approach 1:
The patent divides the negative electrode into multiple layers: a first negative electrode layer containing Si-based active material and a second negative electrode layer containing carbonaceous material. This segmentation isolates the high-capacity Si-based material from direct contact with electrolyte while maintaining its capacity benefits, and the carbonaceous layer provides structural stability to prevent swelling-induced cracking, thus resolving the contradiction between high capacity and cycle life reliability
Solution Approach 2:
The patent creates a composite negative electrode structure combining Si-based active material with carbonaceous material in specific weight ratios (Si-based: 30-80 wt%, carbonaceous: 20-70 wt%). This composite approach allows the Si-based material to provide high theoretical capacity while the carbonaceous material provides structural integrity and swelling resistance, simultaneously achieving both high capacity and improved charge/discharge cycle life
2Quantity of substance
If Si-based materials are used to achieve high theoretical capacity, then capacity is improved, but cracking occurs due to volumetric swelling causing mis-contact between active material and current collector
Solution Approach 1:
The patent separates the Si-based active material into a distinct first negative electrode layer and provides a second negative electrode layer with carbonaceous material. This segmentation prevents the Si-based material from undergoing free volumetric swelling that causes cracking, while maintaining its high capacity properties through controlled structural configuration
Solution Approach 2:
The patent forms a composite structure where Si-based material (30-80 wt%) is combined with carbonaceous material (20-70 wt%). The carbonaceous component acts as a structural framework that constrains volumetric swelling of the Si-based material during lithium intercalation, preventing cracking and maintaining structural integrity while preserving high capacity
3Reliability
If carbonaceous materials are used as negative electrode active materials to achieve high stability and reversibility, then reliability is improved, but capacity is limited
Solution Approach 1:
The patent assigns multiple functions to different layers: the first negative electrode layer with Si-based material provides high capacity function, while the second negative electrode layer with carbonaceous material provides stability and reversibility function. This multi-functional assignment allows the overall electrode to achieve both high capacity and high reliability simultaneously
Solution Approach 2:
The patent creates a composite negative electrode where Si-based material (30-80 wt%) contributes high theoretical capacity and carbonaceous material (20-70 wt%) contributes high stability and reversibility. The synergistic combination allows the electrode to achieve capacity values exceeding traditional carbonaceous materials while maintaining their stability and reversibility characteristics
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 significantly improves both life and output characteristics of lithium secondary batteries by preventing particle pulverization and maintaining physical binding, thus extending cycle life and ensuring high capacity retention.
Implementation Method 1
a coating layer surrounding the silicon particles, wherein the silicon particles have a full width at half maximum (FWHM) of peak ranging from 2 to 10 in the particle diameter distribution having an average particle diameter (D 50 ) of 1-30 μm, and the coating layer includes at least one of carbon and a polymer
Implementation Method 2
the coating layer includes at least one of carbon and a polymer
Implementation Method 3
the coating layer includes at least one of carbon and a polymer
Implementation Method 4
Si-based negative electrode active materials are problematic in that they undergo a change in crystal structure during lithium intercalation and storage to cause volumetric swelling
Implementation Method 5
the silicon particles have a full width at half maximum (FWHM) of peak ranging from 2 to 10 in the particle diameter distribution having an average particle diameter (D 50 ) of 1-30 μm
Data Source
Figure 1~2
Figure 3~4
AI summary
Disclosed is a negative electrode active material for a lithium secondary battery which includes: silicon particles; and a coating layer surrounding the silicon particles, wherein the silicon particles have a full width at half maximum (FWHM) of peak ranging from 2 to 10 in the particle diameter distribution having an average particle diameter (D50) of 1-30 µm, and the coating layer includes at least one of carbon and a polymer. A negative electrode and lithium secondary battery including the negative electrode active material are also disclosed.