Graphite-Silicon Anode Composite With Porous Carbon Buffering
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Solution Overview
Problem
The high volume change of silicon anode electrode materials in lithium-ion batteries during the delithiation/intercalation process leads to unsatisfactory cycle and rate performance, hindering their commercialization, and existing graphite anode electrodes have limited capacity, necessitating a material with higher energy density and improved stability.
Innovation Solution
A graphite-silicon composite anode electrode material is developed through surface porous treatment of starch, absorption of nano silicon and lithium, followed by high-temperature carbonization to form a porous silicon-Li-containing precursor with a carbon matrix structure, which is further coated with a carbon layer to enhance conductivity and prevent volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon anode electrode material is used to increase capacity, then the theoretical capacity increases from 372 mAh/g to 4200 mAh/g, but the volume change during delithiation/intercalation becomes large causing unsatisfactory cycle performance
Solution Approach 1:
The patent employs a porous carbon coating layer with controlled porosity (30-70%) formed through starch carbonization. This porous structure provides buffer space for silicon volume expansion during lithium insertion/extraction, accommodating the large volume changes without causing material degradation. The pores act as voids that absorb expansion stress, preventing cracking and maintaining structural integrity over multiple cycles, thus resolving the contradiction between high capacity and cycle performance.
Solution Approach 2:
The patent creates a composite structure consisting of silicon particles embedded in a carbon matrix formed from starch. This composite material combines the high capacity of silicon with the structural stability and flexibility of carbon. The carbon coating layer (5-20 nm thickness) provides mechanical support and electrical conductivity while the porous structure accommodates volume changes, enabling the composite to maintain both high capacity and good cycle performance.
2Quantity of substance
If silicon anode electrode material is used to increase capacity, then the theoretical capacity increases from 372 mAh/g to 4200 mAh/g, but the material becomes difficult to be directly used due to volume expansion
Solution Approach 1:
The patent uses starch as an intermediary material that serves multiple functions: it provides the carbon source for the coating layer, creates the porous structure through carbonization, and acts as a binding matrix. The starch-based porous carbon coating is applied to silicon particles before electrode fabrication, making the silicon material processable and manufacturable while maintaining its high capacity benefits.
Solution Approach 2:
The patent optimizes several parameters to enable manufacturability: controlling the starch concentration (5-20 wt%), adjusting the pH value (3.0-6.5) during treatment, optimizing carbonization temperature (800-1000°C), and controlling the final carbon layer thickness (5-20 nm). These parameter optimizations transform raw silicon into a manufacturable composite material with appropriate mechanical properties, electrical conductivity, and structural stability.
3Reliability
If a carbon layer is coated on silicon anode electrode material to suppress volume change, then cycle performance is improved, but the conductivity of the silicon surface needs to be enhanced
Solution Approach 1:
The patent employs a porous carbon coating layer rather than a dense coating. The porous structure (30-70% porosity) provides pathways for electron transport while maintaining mechanical flexibility. The carbon material in the pores and on the surface provides electrical conductivity, while the porous architecture allows volume expansion. This resolves the contradiction by providing both structural support for cycle stability and conductive pathways for energy efficiency.
4Stability of the object's composition
If the porosity of silicon anode electrode material is increased to suppress volume change, then stability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent uses a self-assembling approach where starch particles naturally form a porous network structure through carbonization. The starch-based coating is applied by simple dip-coating or mixing methods, and the porous structure forms automatically during the carbonization process without requiring complex pore-forming agents or multi-step fabrication procedures. This self-organizing process creates the desired porous structure while keeping manufacturing relatively simple.
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 carbon matrix structure provides a buffer for silicon expansion, maintaining stability and improving cycle performance by preventing cracking and falling off, while the carbon coating enhances conductivity and forms a stable SEI film, ensuring better performance during lithium absorption and discharge.
Implementation Method 1
lithium can be absorbed through surface porous treatment of starch
Implementation Method 2
through further pore expansion, nano silicon and ammonium acetate can be absorbed
Implementation Method 3
high-temperature carbonization is carried out to obtain a porous silicon-Li-containing precursor doped with adsorbed silicon, lithium, and nitrogen
Implementation Method 4
The carbon matrix structure provides a buffer space for the expansion of silicon, effectively inhibits volume expansion
Implementation Method 5
a carbon coating layer is formed by surrounding a mixed gas and carrying out secondary carbonization to ensure that the conductivity of the silicon surface can be improved
Implementation Method 6
it can avoid direct contact between silicon and the electrolyte to ensure the formation of a stable SEI film during the cycle
Data Source
AI summary
The disclosure relates to a graphite-silicon composite anode electrode material, a preparation method therefor, and the application thereof. The preparation method for the graphite-silicon composite anode electrode material comprises: mixing a starch and a lithium salt to obtain a mixed solution S, heating, and stirring; adding a biological enzyme, stirring to obtain a mixed solution T, mixing the mixed solution T with nano silicon, shaking to obtain an adsorption type mixed solution, and drying to obtain porous starch; carrying out primary thermal carbonization to obtain a black powder, adding an organic acid ammonium into the black powder, carrying out thermal adsorption, and dehydrating to obtain a nitrogen-adsorbed porous silicon-Li-containing precursor; and mixing the nitrogen-adsorbed porous silicon-Li-containing precursor with graphite spheres, introducing a mixed gas to obtain a porous silicon-Li-containing precursor and graphite sphere mixture surrounded by the mixed gas, and then carrying out secondary thermal carbonization to obtain the graphite-silicon composite anode electrode material. The graphite-silicon composite anode electrode material is applied to the preparation of a lithium ion battery and has relatively good cycle performance.