Si-C Core with Phosphorus Coating for Battery Anodes
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Solution Overview
Problem
Lithium secondary batteries face issues with volume expansion during charging and discharging, leading to capacity deterioration and reduced cycle life due to the use of metal-based anode active materials like Si and Sn, which limits their commercial viability.
Innovation Solution
An anode active material comprising a carbon-silicon composite with a phosphorus-based alloy coating layer is developed, where the coating layer is formed on the surface of a core with a cavity, using a method involving silicon polymer particles treated with a metal chloride solution and heat treatment in a reducing atmosphere to control the coating thickness and density, thereby alleviating stress from volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based anode active materials (Si, Sn) are used to achieve higher charge/discharge capacity, then capacity increases, but volume change during charging/discharging causes cracks and reduces cycle life
Solution Approach 1:
The patent embeds metal particles (Si or Sn) inside a porous carbon matrix, creating a nested structure where the metal is contained within the carbon framework. This nesting approach allows the high-capacity metal to be protected by the volume-stable carbon outer layer, preventing crack propagation while maintaining electrochemical performance.
Solution Approach 2:
The patent employs a flexible porous carbon coating layer that envelops the metal particles. This carbon shell acts as a buffer that can accommodate volume expansion of the metal during lithiation while maintaining structural integrity, preventing the formation of cracks that would otherwise lead to capacity fading.
2Reliability
If alloy of Si/Sn and another metal is used to improve cycle life and prevent volume expansion, then cycle life improves, but volume expansion during alloying with lithium still occurs
Solution Approach 1:
The patent changes the physical and chemical parameters of the carbon matrix by controlling its porosity, density, and compositional ratio (carbon to metal). By optimizing these parameters, the carbon matrix can accommodate volume expansion of the metal alloy during lithium alloying without compromising cycle life.
Solution Approach 2:
The patent creates a composite material system combining metal particles (Si/Sn with other metals) embedded in a porous carbon matrix. This composite structure synergistically combines the high capacity of metal alloys with the volume stability and flexibility of carbon, allowing volume expansion to occur within the porous carbon framework without causing structural failure.
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 phosphorus-based alloy coating layer effectively reduces degradation caused by volume expansion, enhancing the cycle life and capacity retention of lithium secondary batteries by acting as a buffer and facilitating lithium ion diffusion.
Implementation Method 1
volume expansion generated during alloying with lithium
Implementation Method 2
facilitating lithium ion diffusion
Implementation Method 3
carbonizing the phosphorous (P)-based alloy surface-coated silicon polymer particle by heat treatment in a reducing atmosphere
Data Source
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AI summary
The present invention relates to an anode active material for lithium secondary batteries and a method for manufacturing same, the anode active material comprising: a core part including a carbon-silicon complex and having a cavity therein; and a coated layer which is formed on the surface of the core part and includes a phosphor-based alloy. The anode active material of the present invention, including the phosphor-based alloy coated layer formed on the surface of the carbon-silicon complex having the cavity therein, enables stress resulting from a volume expansion caused by the alloying of lithium and Si to be released by coating the surface of an Si-based active material with a phosphor-based alloy. Also, the manufacturing method for the anode active material according to the present invention enables easy adjustment of the thickness of the coated layer.