Silicon-Coated Carbon Anode for Stable High-Capacity Li-Ion Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges with silicon-based anode materials that cause side reactions, contraction, and expansion, leading to reduced lifespan and stability, especially when exposed to moisture and air, necessitating a solution for high capacity and stability.
Innovation Solution
A carbon-based anode active material layer with a silicon coating, where the silicon content on the surface is controlled between 3 atom% to 25 atom% and the Si—O peak intensity ratio is between 0.05 to 1, formed using a dry deposition process to prevent gas generation and maintain conductivity, is used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as anode active material, then capacity is improved, but side reactions with moisture and air occur causing reduced stability
Solution Approach 1:
A carbon coating layer is introduced as an intermediary between the silicon-based active material and the external environment (moisture, air, electrolyte). This carbon layer prevents direct contact and side reactions while allowing lithium ion transport, thus maintaining high capacity benefits of silicon while improving stability and lifespan
Solution Approach 2:
The anode is designed as a composite structure combining silicon-based active material particles with a carbon coating layer. This composite approach leverages the high capacity of silicon while the carbon component provides chemical stability, moisture resistance, and structural integrity during cycling
2Quantity of substance
If silicon-based material is used as anode active material, then capacity is improved, but contraction and expansion occur during charging and discharging
Solution Approach 1:
The carbon coating layer acts as a flexible shell that can accommodate the volume changes of silicon during lithiation and delithiation. This shell maintains structural integrity, prevents particle fragmentation, and ensures continuous electrical contact throughout cycling
Solution Approach 2:
The carbon coating is applied beforehand to the silicon particles, creating a protective cushion that absorbs mechanical stress from expansion and contraction. This pre-established protective layer prevents direct mechanical failure of the silicon structure during volume changes
3Reliability
If conventional anode active material is used, then stability is maintained, but high capacity is not achieved
Solution Approach 1:
The invention creates a composite anode structure where silicon-based material (providing high capacity) is combined with carbon coating (providing stability). This composite approach allows the system to achieve both high capacity and good stability simultaneously, overcoming the limitation of conventional single-material anodes
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
This approach enhances capacity and energy density while reducing gas generation and anode resistance, ensuring improved stability and lifespan of the lithium secondary battery.
Implementation Method 1
formed using a dry deposition process to prevent gas generation and maintain conductivity
Implementation Method 2
A surface content of silicon of the anode active material layer measured by an X-ray photoelectric spectroscopy (XPS)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An anode active material for a secondary battery includes an anode current collector, and an anode active material layer formed on the anode current collector and including carbon-based active material particles and a silicon coating formed on surfaces of the carbon-based active material particles. A surface content of silicon of the anode active material layer measured by an X-ray photoelectric spectroscopy (XPS) is in a range from 3 atom% to 25 atom%. A peak intensity ratio defined as a ratio of a second peak intensity corresponding to a peak intensity at a binding energy in a range from 102 eV to 106 eV relative to a first peak intensity corresponding to a peak intensity at a binding energy in a range from 98 eV to 102 eV is in a range from 0.05 to 1.