SiOx Anode Coating Structure for Cycle Life and Low Impedance
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high cycle life due to the volume expansion and contraction of silicon-based anode materials, which leads to structural damage, electrolyte consumption, and increased electrochemical impedance, limiting their performance and stability.
Innovation Solution
A silicon compound (SiOx) coated with an oxide layer (MeOy) and a carbon nanotube layer is used, where the oxide layer forms a stable interface with the silicon compound and the carbon nanotube layer creates a porous conductive network to enhance mechanical strength, inhibit volume expansion, and improve lithium diffusion and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material to achieve high reversible capacity (4200 mAh/g), then the capacity is improved, but the volume expansion reaches about 400% causing structural damage and continuous SEI formation
Solution Approach 1:
The patent employs a multi-layer nested structure where the silicon compound core is coated with an oxide layer (MeOy), which is further coated with a carbon nanotube layer. This nested configuration allows the high-capacity silicon material to be protected by successive shells that constrain volume expansion and prevent direct contact with electrolyte, thereby maintaining structural stability during charge-discharge cycles.
Solution Approach 2:
The patent creates a composite anode material consisting of silicon compound (SiOx) combined with oxide coating (MeOy where Me includes Al, Si, Ti, Mn, V, Cr, Co or Zr) and carbon nanotube outer layer. This composite structure synergistically combines the high capacity of silicon with the protective properties of oxide and conductive carbon nanotubes, resolving the contradiction between capacity and stability.
2Stability of the object's composition
If silicon-oxygen material is used to reduce volume expansion to 120-160%, then the structural damage is reduced, but the reversible capacity decreases compared to pure silicon
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner silicon compound core provides high capacity, while the outer oxide and carbon nanotube layers provide structural stability and volume control. Each layer has differentiated local properties optimized for its specific function, allowing the material to achieve both high capacity and controlled expansion.
3Loss of substance
If repeated formation of SEI occurs due to volume expansion, then electrolyte consumption increases, but the cycle life requirement is not met
Solution Approach 1:
The patent applies preliminary action by pre-coating the silicon compound with an oxide layer (MeOy) before battery assembly. This pre-formed protective layer prevents direct exposure of fresh silicon surfaces during initial cycles, thereby preventing continuous SEI formation and electrolyte consumption, and establishing structural integrity for long cycle life from the outset.
Solution Approach 2:
The oxide layer (MeOy) and carbon nanotube layer serve as intermediary protective barriers between the silicon compound and the electrolyte. These intermediary layers prevent direct interaction that would lead to continuous SEI formation, thereby reducing electrolyte consumption and enabling long cycle life.
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 alleviates structural damage, reduces electrolyte consumption, and enhances the cycle life and rate performance of the anode material by improving the bonding between the carbon layer and the silicon-oxygen material, maintaining structural stability and facilitating ion and electron transmission.
Implementation Method 1
the oxide MeOy layer coats at least a portion of the silicon compound SiOx... the volume expansion of silicon-oxygen material can be controlled to be only 120-160%
Implementation Method 2
the carbon nanotube layer coats at least a portion of the oxide MeOy layer... the carbon nanotube layer creates a porous conductive network to enhance mechanical strength, inhibit volume expansion, and improve lithium diffusion and conductivity
Implementation Method 3
the carbon nanotube layer creates a porous conductive network to enhance mechanical strength, inhibit volume expansion, and improve lithium diffusion and conductivity
Implementation Method 4
the tight coating structure can effectively alleviate structural damage during this process
Data Source
AI summary
The present application relates to an anode material, and an electrochemical device and an electronic device using the same. The anode material of the present application includes: a silicon compound SiOx, where x is 0.5-1.5; an oxide MeOy layer, the MeOy layer coating at least a portion of the silicon compound SiOx, where Me includes at least one of Al, Si, Ti, Mn, V, Cr, Co or Zr, where y is 0.5-3; and a carbon nanotube layer, the carbon nanotube layer coating at least a portion of the MeOy layer. The anode material can significantly enhance the cycle performance and rate performance of the electrochemical device, and significantly reduce the impedance of the electrochemical device.