LiF-Coated Silicon Nanoparticles for Battery Anodes
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Solution Overview
Problem
Current silicon-based negative electrode active materials in secondary batteries face challenges with excessive volume change during charging and discharging, leading to reduced lifespan and safety issues due to side reactions with the electrolyte, which existing carbon coating techniques fail to effectively control.
Innovation Solution
A negative electrode active material comprising a carbonaceous matrix with silicon nano-particles coated with a LiF layer, where the LiF coating minimizes side reactions and controls volume expansion, improving initial efficiency and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a silicon-based particle is used as negative electrode active material, then discharge capacity is improved, but volume expansion occurs excessively during charging and discharging
Solution Approach 1:
The patent applies nested structure by placing silicon particles inside a porous carbon matrix, forming a core-shell configuration where the silicon core is embedded within the carbon matrix. This nesting approach allows the silicon to expand and contract during lithium insertion/extraction while being contained within the carbon matrix, thus resolving the volume expansion problem while maintaining high discharge capacity.
Solution Approach 2:
The patent creates a composite material system combining silicon-based particles with porous carbon matrix. The composite structure leverages the high capacity of silicon while the carbon matrix provides structural stability and volume compensation. The porous nature of the carbon matrix allows it to absorb the volume changes of silicon during cycling, effectively controlling overall volume expansion.
2Volume of moving object
If a carbon coating layer is formed on silicon-based particle, then volume expansion is controlled, but side reaction with electrolyte is not effectively controlled
Solution Approach 1:
The patent employs porous carbon matrix instead of dense carbon coating. The porous structure provides multiple benefits: it maintains electrical conductivity, allows electrolyte penetration for lithium ion transport, and creates a larger surface area for stable SEI formation. The porous structure prevents excessive side reactions while maintaining volume control, overcoming the limitations of dense carbon coating.
Solution Approach 2:
The patent applies different properties to different regions: the inner region uses porous carbon for electrolyte interaction and lithium ion transport, while the outer structure provides mechanical constraint for volume control. This local differentiation of material properties allows simultaneous achievement of side reaction control and volume management.
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 LiF coating layer effectively reduces side reactions and volume expansion, enhancing the battery's initial efficiency, discharge capacity, and maintaining electrode thickness, resulting in improved performance and lifespan.
Implementation Method 1
a coating layer which coats the oxide layer and includes at least one of Li 2 SiO 3 and LiF, wherein the coating layer includes LiF
Implementation Method 2
a carbonaceous matrix including a plurality of nano-particles, wherein each of the nano-particles comprises a silicon core
Data Source
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AI summary
The present invention relates to a negative electrode active material including a carbonaceous matrix having a plurality of nano-particles, wherein the nano-particles have a silicon core, an oxide layer disposed on the silicon core and including SiOx (0<x≤2), and a coating layer covering at least a portion of the surface of the oxide layer and including LiF.