Silicon Anode Material With 3D Conductive Network for Cycle Stability
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Solution Overview
Problem
Lithium ion batteries using silicon anode materials face challenges due to large volume changes during charge and discharge cycles, leading to mechanical stress, pulverization, and poor conductivity, which limits their cycle performance and efficiency.
Innovation Solution
An anode active material comprising silicon particles embedded in a three-dimensional conductive network formed by carbon nanotubes and vapor grown carbon fibers, with a controlled surface area ratio and binder composition to enhance conductivity and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon material is used as anode active material, then reversible capacity is improved (up to 4200 mAh/g), but volume change during charge and discharge cycles increases (up to 300% expansion ratio)
Solution Approach 1:
The patent embeds silicon particles inside hollow carbon spheres, creating a nested structure where the silicon is contained within the carbon shell. This nesting approach allows the silicon to expand and contract within the confined space of the hollow sphere during lithium insertion and extraction, accommodating the 300% volume expansion without causing mechanical failure or particle pulverization.
Solution Approach 2:
The hollow carbon sphere acts as a flexible shell that can deform to accommodate the volume changes of the silicon particles during cycling. The carbon shell provides mechanical flexibility and structural support, allowing the anode to withstand the large volume expansion and contraction forces generated by silicon during charge and discharge cycles.
2Quantity of substance
If silicon material is used as anode active material, then reversible capacity is improved (up to 4200 mAh/g), but mechanical stress and pulverization occur due to large volume change
Solution Approach 1:
The hollow carbon sphere provides a protective nested structure that contains silicon particles, shielding them from mechanical stress and preventing pulverization during volume expansion and contraction. The carbon shell acts as a protective cage that maintains structural integrity even when the internal silicon undergoes large dimensional changes.
Solution Approach 2:
The patent creates a composite material system combining silicon particles with hollow carbon spheres. This composite structure leverages the high capacity of silicon while utilizing the mechanical strength and flexibility of carbon to resist pulverization and maintain structural integrity during cycling.
3Quantity of substance
If silicon material is used as anode active material, then reversible capacity is improved (up to 4200 mAh/g), but conductivity deteriorates causing severe polarization
Solution Approach 1:
The patent forms a composite structure where conductive carbon materials (both the hollow sphere shell and external conductive network) are combined with silicon particles. This composite approach maintains high electrical conductivity throughout the anode structure, ensuring efficient electron transport even when using low-conductivity silicon as the active material.
Solution Approach 2:
The patent applies conductive carbon materials locally in specific configurations - forming hollow spheres around silicon particles and creating an external three-dimensional conductive network. This localized application of conductive materials ensures that each silicon particle has direct electrical contact pathways, eliminating polarization issues while maintaining high capacity.
4Volume of moving object
If nanocrystallization of silicon materials is applied, then volume change is reduced, but specific surface area increases (>100 m2/g) consuming more electrolyte
Solution Approach 1:
The hollow carbon sphere shell provides a flexible containment structure that allows silicon particles to undergo volume changes without requiring nanocrystallization. By providing this flexible shell, the patent eliminates the need to reduce particle size to nanoscale, thereby avoiding the associated increase in specific surface area and electrolyte consumption.
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 suppresses silicon particle expansion, maintains conductivity, and improves the cycle performance and stability of lithium ion batteries, enhancing their electrochemical performance and industrial production feasibility.
Implementation Method 1
the first conductive material and the second conductive material form a three-dimensional conductive network structure
Implementation Method 2
the anode active particles are accommodated in the three-dimensional conductive network structure
Data Source
AI summary
The present application relates to an anode active material and a preparation method thereof, and a device using the anode active material. The anode active material provided by the present application includes anode active particles having silicon element, a first conductive material and a second conductive material, wherein the first conductive material and the second conductive material form a three-dimensional conductive network structure, at least a portion of the anode active particles are accommodated in the three-dimensional conductive network structure, and a ratio of the total surface area of the first conductive material to the total surface area of the anode active particles is less than 1000. The capacity retention rate and expansion ratio of the anode active material with progression of the cycle are significantly improved.