Porous Si/C Anode Structure With GO Layer for Expansion Control
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Solution Overview
Problem
Existing silicon-based anode materials for lithium-ion, potassium-ion, and sodium-ion batteries face challenges such as high volume expansion, limited capacity, and stability issues, which hinder their performance and cycle life, especially in industrial applications requiring over 1000 cycles.
Innovation Solution
A composite anode material comprising silicon-carbon composite particles with a porous shell and a graphene oxide layer, formed through spray drying and baking, which minimizes volume expansion and enhances electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon particles are encapsulated with a compact carbon layer, then electronic conductivity is improved, but volume expansion is not inhibited leading to capacity fading
Solution Approach 1:
The patent employs a porous carbon coating layer with controlled porosity (5-50% void volume) that provides both electronic conductivity pathways and sufficient void space to accommodate silicon volume expansion during lithiation. The porous structure allows the carbon layer to maintain electrical contact while physically buffering the expansion stress, thereby resolving the contradiction between conductivity enhancement and expansion inhibition.
Solution Approach 2:
The invention creates a composite structure combining silicon particles with a porous carbon matrix, where the carbon phase provides both conductive pathways and mechanical buffering. This composite approach allows simultaneous achievement of electrical conductivity and volume expansion management, as the carbon-silicon interface and porous network work together to maintain structural integrity during cycling.
2Stability of the object's composition
If a thick carbon coating is applied to silicon particles, then volume expansion is buffered, but Li diffusion is hindered
Solution Approach 1:
The porous carbon coating with controlled porosity (5-50%) creates a network of channels and voids that allow lithium ions to diffuse through the coating with minimal resistance. The porous structure maintains buffering capacity while providing open pathways for ion transport, thus preventing the trade-off between expansion buffering and diffusion speed.
Solution Approach 2:
The carbon coating is designed with non-uniform local properties - the porous structure provides different characteristics at different scales. At the macro level, the coating thickness provides expansion buffering, while at the micro level, the porous channels facilitate rapid lithium diffusion. This local quality variation resolves the contradiction between buffering and diffusion.
3Ease of manufacture
If conventional spray drying is used to prepare Si/C composites, then industrial scalability is achieved, but the compact structure does not inhibit volume expansion
Solution Approach 1:
The spray drying process is modified to incorporate porogen materials that create a porous carbon structure during drying and subsequent heat treatment. This maintains the industrial scalability of spray drying while transforming the product from a compact to a porous structure that can accommodate volume expansion, thus resolving the contradiction between manufacturability and expansion inhibition.
Solution Approach 2:
The invention changes key process parameters in spray drying, including the composition of the slurry (adding porogens), drying temperature profiles, and atmospheric conditions, to control the formation of porous structures. These parameter changes enable the same spray drying technology to produce expansion-resistant composites, maintaining scalability while improving performance.
4Quantity of substance
If high silicon content is used in the anode, then theoretical capacity is increased, but capacity retention over cycles is reduced
Solution Approach 1:
The high silicon content composites are stabilized by incorporating them into a porous carbon matrix that provides structural support and conductive pathways. The carbon-silicon composite structure allows higher silicon loading while the porous network maintains electrical connectivity and mechanical integrity during cycling, enabling both high capacity and good retention.
Solution Approach 2:
The porous carbon coating with controlled porosity provides a flexible matrix that can accommodate the volume changes of high silicon content particles during lithiation and delithiation. This porous structure prevents particle fracture and maintains electrical contact even with high silicon loading, thus enabling capacity retention despite increased silicon content.
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 composite anode material achieves high capacity values (2200-2300 mAh/g for Li-Si cells) with excellent capacity retention (up to 100% over 1500 cycles) and resistance to Li-induced volume expansion, while allowing minimal Li diffusion hindrance and using recycled silicon.
Implementation Method 1
the porous shell comprising the plurality of silicon particles intermixed with the carbon-based material
Implementation Method 2
an interesting method suitable for industrial use is the spray drying method
Implementation Method 3
a dispersion containing silicon nanoparticles, one or more conductive carbon additives and a carbon precursor in absolute ethyl alcohol is dried by spray-drying
Implementation Method 4
the process starts with a first mixed solution in which silicon or silicon oxide particles, a conductive material and a porogen are dispersed
Data Source
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AI summary
In a first aspect, the present invention relates to a composite anode material, comprising: (i) a layer of silicon-carbon (Si/C) composite material comprising silicon-carbon composite particles, and (ii) a graphene oxide (GO) layer covering the layer of silicon-carbon composite material; wherein the silicon-carbon composite particles each comprise a plurality of silicon (Si) particles intermixed with a carbon-based material, and wherein the silicon-carbon composite particles comprise a porous shell surrounding a hollow, the porous shell comprising the plurality of silicon particles intermixed with the carbon-based material.