Layered Silicon-Carbon Anode for Fast-Charging Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in improving energy density and rapid charging performance while maintaining cycle life characteristics, due to the limitations of graphite anodes and the high cost and uneven distribution of single-walled carbon nanotubes when mixed with silicon materials.
Innovation Solution
An anode structure featuring a carbon-based first active material layer and a second active material layer with a silicon-based material and single-walled carbon nanotubes, where the silicon-based material and single-walled carbon nanotubes are concentrated on the surface, forming a weight ratio of 30:1 to 150:1, enhancing lithium-ion reaction sites and reducing the amount of single-walled carbon nanotubes needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon material is used to improve energy density, then energy density is improved, but cycle life characteristics deteriorate due to volume expansion
Solution Approach 1:
The patent uses a thin film anode structure where silicon-based material is deposited as a thin layer on the current collector. This thin film configuration allows the silicon to expand and contract during charging-discharging cycles without causing the severe mechanical degradation that would occur in bulk silicon structures, thereby maintaining cycle life while preserving high energy density benefits
Solution Approach 2:
The patent changes the physical form and dimensional parameters of silicon material by converting it from bulk form to thin film form with controlled thickness. This parameter change enables the silicon to accommodate volume expansion during lithiation without compromising structural integrity, thus improving cycle life while maintaining high energy density
2Reliability
If single-walled carbon nanotubes are mixed with silicon material to improve cycle life, then cycle life is improved, but manufacturing cost increases due to high price of nanotubes
Solution Approach 1:
The patent replaces expensive single-walled carbon nanotubes with cheaper carbon black particles that serve the same function of maintaining electrical conductivity and structural stability during silicon expansion. This substitution dramatically reduces manufacturing cost while still improving cycle life characteristics
Solution Approach 2:
The patent uses carbon black particles as a cost-effective substitute that replicates the essential function of single-walled carbon nanotubes in maintaining electrical conductivity and mechanical stability during silicon volume changes, achieving similar performance improvement at much lower cost
3Speed
If single-walled carbon nanotubes are mixed with silicon material to improve rapid charging, then rapid charging performance is improved, but uniformity of distribution is poor leading to limited improvement
Solution Approach 1:
The patent achieves homogeneous distribution of conductive carbon black particles throughout the silicon-based material matrix through thorough mixing processes. This uniform distribution ensures consistent electrical conductivity throughout the anode, enabling improved rapid charging performance without the aggregation problems that plague nanotube-based composites
4Ease of manufacture
If graphite anode material is used, then manufacturing cost is low and manufacturing process is simple, but energy density is low
Solution Approach 1:
The patent creates a composite anode structure consisting of silicon-based material deposited on a graphite or carbon-coated current collector. This composite structure combines the high energy density of silicon with the manufacturing familiarity and low cost of graphite-based systems, achieving high energy density while maintaining ease of manufacture
Solution Approach 2:
The patent segments the anode structure into distinct functional layers: a current collector layer (graphite or carbon-coated) that provides mechanical support and electrical conductivity, and a silicon-based active material layer that provides high capacity. This segmentation allows each layer to be optimized independently while maintaining overall manufacturing simplicity
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 configuration improves energy density, cycle life characteristics, and rapid charging performance by alleviating volume expansion issues and reducing the cost of single-walled carbon nanotubes, while maintaining manufacturing economics.
Implementation Method 1
the single-walled carbon nanotubes were not uniformly distributed on the surface of the silicon material, so there was a problem that the improvement of rapid charging performance was limited
Implementation Method 2
the silicon material has a problem in that cycle life characteristics of the secondary battery are deteriorated due to volume expansion during charging and discharging
Implementation Method 3
the cathode and anode are each provided with active materials into which lithium ions may be inserted and extracted
Implementation Method 4
the cathode and anode are each provided with active materials into which lithium ions may be inserted and extracted
Data Source
AI summary
The present disclosure provides an anode including an anode current collector, a first anode active material layer formed on at least one side of the anode current collector and comprising a carbon-based material, and a second anode active material layer formed on the first anode active material layer and comprising a silicon-based material and single-walled carbon nanotubes, wherein a weight ratio of the silicon-based material and the single-walled carbon nanotubes is 30:1 to 150:1, and a secondary battery including the same.