Silicon Anode Coating Structure to Limit SEI Clogging
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Solution Overview
Problem
Silicon-based negative electrode active materials experience rapid volume expansion during charging and discharging, leading to conductive path disconnection and reduced service life due to SEI layer clogging, limiting their commercial application in high-capacity lithium secondary batteries.
Innovation Solution
A double-layer structure is formed by coating a first silicon-based active material with pores using a second silicon-based active material having a controlled crystal grain size of 20 nm to 200 nm, which acts as a Li ion channel and prevents SEI layer formation, thereby reducing particle breakage and improving service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compound is used as negative electrode active material to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging which disconnects conductive path and degrades battery characteristics
Solution Approach 1:
A coating layer comprising carbon and silicon oxide is formed on the surface of the silicon-based compound particles. This coating layer acts as a flexible protective shell that accommodates volume expansion during charging while maintaining structural integrity and preventing conductive path disconnection. The coating layer remains adhered to the particles even during expansion, preserving electrical conductivity.
Solution Approach 2:
The coating layer is composed of composite materials including carbon and silicon oxide in specific weight ratios (carbon: 30-70 wt%, silicon oxide: 70-30 wt%). This composite structure combines the advantages of both materials: carbon provides electrical conductivity and structural stability, while silicon oxide provides mechanical strength and volume expansion buffering, together preventing conductive path disconnection.
2Duration of action of stationary object
If porosity is adjusted to high range to alleviate stress from particle expansion/contraction, then service life performance is improved, but SEI layer accumulates on surface and clogs particle pores, resulting in rapid decrease in service life performance
Solution Approach 1:
The coating layer is applied specifically on the surface of the silicon-based compound particles, creating a localized protective barrier. This surface treatment allows the interior porous structure to maintain its stress-alleviating function while the exterior coating prevents SEI layer accumulation and pore clogging, thus improving service life without the harmful effects.
Solution Approach 2:
The coating layer acts as an intermediary between the porous silicon-based compound particles and the electrolyte. It prevents direct contact between the electrolyte and the porous surface, thereby blocking SEI layer formation and pore clogging, while still allowing lithium ion transport through the coating to reach the porous interior for continued electrochemical activity.
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 coating layer suppresses SEI layer side reactions, maintains a pathway for Li ion migration, and alleviates stress caused by lithium intercalation, enhancing the service life and performance of silicon-based negative electrodes.
Implementation Method 1
a coating layer provided on a surface of the first silicon-based active material, wherein the coating layer includes a second silicon-based active material
Implementation Method 2
a crystal grain size of the second silicon-based active material is 20 nm or greater and 200 nm or less... functioning as a Li ion channel
Implementation Method 3
the porosity is adjusted to a certain high range to alleviate the stress caused by particle expansion/contraction due to intercalation/deintercalation of lithium during charging/discharging
Data Source
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AI summary
The present application relates to: a negative electrode active material comprising a first silicon-based active material and a coating layer provided on the surface of the first silicon-based active material, wherein the coating layer includes a second silicon-based active material, and the grain size of the second silicon-based active material is 20 nm to 200 nm; a method for preparing the negative electrode active material; a negative electrode composition; a negative electrode for a lithium secondary battery, the negative electrode comprising same; and a lithium secondary battery comprising the negative electrode.