Porous Silicon-Carbon Anode Shell Layer for Low Expansion Cycling
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Solution Overview
Problem
The existing silicon-carbon composite materials for lithium-ion batteries face issues such as silicon-carbon separation and unstable solid electrolyte interphase (SEI) films, leading to rapid capacity attenuation and volume expansion, which restricts the energy density and cycling performance of lithium-ion batteries.
Innovation Solution
A negative electrode material with a core-shell structure is developed, where amorphous silicon is distributed within and on the surface of a non-graphitizing porous carbon material, coated with a protective layer of silicon monoxide, silicon dioxide, or lithium silicate, providing buffer space for volume expansion and stabilizing the SEI film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to achieve high specific capacity, then theoretical lithium storage capacity is improved (10 times that of graphite), but large volume change occurs during charging/discharging causing fast attenuation of cycling performance and large thickness expansion
Solution Approach 1:
The patent embeds silicon particles within a three-dimensional porous carbon matrix structure, where silicon is nested inside the porous framework. This nesting approach allows silicon to expand and contract within the confined porous space without causing macroscopic volume changes or structural collapse, thereby maintaining cycling stability while preserving high lithium storage capacity
Solution Approach 2:
The patent employs a three-dimensional porous carbon matrix as the host structure for silicon. The porous architecture provides sufficient void space to accommodate silicon's volume expansion during lithium insertion while maintaining overall structural integrity. The porous structure also facilitates electrolyte penetration and lithium ion transport, ensuring both high capacity and stable cycling performance
2Quantity of substance
If silicon is used as negative electrode material to achieve high specific capacity, then theoretical lithium storage capacity is improved, but poor electronic conductivity and poor ionic conductivity lead to low power density
Solution Approach 1:
The patent creates a composite material system where silicon particles are integrated within a conductive carbon matrix. The carbon component provides excellent electronic conductivity pathways, while the porous structure ensures efficient ionic conductivity. This composite approach combines silicon's high capacity with carbon's superior conductivity, achieving both high lithium storage capacity and high power density
Solution Approach 2:
The patent optimizes the local distribution and morphology of silicon within the porous carbon matrix. By controlling silicon particle size, distribution density, and spatial arrangement within the porous framework, the material achieves optimal local conductivity pathways for both electrons and lithium ions, thereby maximizing power density while maintaining high capacity
3Volume of stationary object
If conventional silicon-carbon composite material is used to buffer volume stress, then volume expansion is reduced, but silicon-carbon separation or unstable SEI film occurs causing continuous attenuation of battery capacity
Solution Approach 1:
The patent pre-forms a stable protective interface layer on the silicon surface before battery assembly. This preliminary protective layer prevents direct contact between silicon and electrolyte, avoiding unstable SEI formation. The pre-stabilized interface ensures consistent electrochemical behavior from the first cycle, preventing continuous capacity attenuation while maintaining volume expansion control
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 enhances the cycling capacity retention and reduces volume expansion, resulting in improved stability and power density of lithium-ion batteries.
Implementation Method 1
The carbon material in the negative electrode material has a relatively large quantity of pores that may accommodate the silicon material and provide buffer space for volume expansion of the silicon material
Implementation Method 2
The shell layer of the negative electrode material can suppress a reaction between the negative electrode material and an electrolyte solution in a charging/discharging process, thereby further improving stability of the passivation film on the surface of the negative electrode material
Data Source
AI summary
Disclosed are a negative electrode material, and a negative electrode plate and a battery including the negative electrode material. The negative electrode material includes a silicon material and a carbon material. The silicon material is distributed on a surface and in a pore of the carbon material, to form a silicon-carbon composite material that serves as a core. A surface of the silicon-carbon composite material is coated with a thin protective layer as a shell layer. The carbon material in the negative electrode material has a relatively large quantity of pores that may accommodate the silicon material and provide buffer space for volume expansion of the silicon material. In this way, the battery has a low cycling volume expansion rate.