Tertiary Composite Particles for Silicon Anode Expansion Control
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Solution Overview
Problem
Lithium-ion batteries face challenges with dendrite formation and volume expansion issues in silicon-based negative electrodes, leading to short-circuits and capacity loss, which limits their specific energy and cyclability.
Innovation Solution
The method involves forming secondary composite particles with a silicon core embedded in a carbon-rich matrix, produced through a gas-phase process where the atomic ratio of silicon to carbon is controlled, and tertiary composite particles are formed by agglomerating these secondary particles into a network with a conductive outer layer, reducing silicon diffusion and enhancing mechanical cohesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the active material to increase storage capacity, then the specific energy is improved, but volume expansion causes cracking and dissipation of the electrode
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nested structure allows silicon to expand and contract during lithiation/delithiation cycles while the carbon matrix provides structural support and prevents electrode disintegration, resolving the contradiction between high capacity and structural stability.
Solution Approach 2:
The patent creates a composite material consisting of silicon particles embedded in a carbon-rich matrix. This composite structure combines the high lithium storage capacity of silicon with the structural stability and conductivity of carbon, allowing the electrode to maintain both high capacity and structural integrity during cycling.
2Duration of action of stationary object
If nanoscale silicon particles are used to accommodate volume variations, then the cyclability is improved, but the surface area to volume ratio increases leading to more SEI formation
Solution Approach 1:
The patent employs a porous carbon matrix with controlled porosity that accommodates nanoscale silicon particles. The porous structure provides buffer space for silicon volume changes during cycling, improving cyclability, while the carbon matrix acts as a barrier that reduces direct electrolyte contact with silicon surfaces, thereby minimizing SEI formation and lithium loss.
3Quantity of substance
If the atomic ratio of silicon to carbon is increased to enhance capacity, then the specific capacity is improved, but the mechanical cohesion of the electrode is reduced
Solution Approach 1:
The patent creates a heterogeneous structure where silicon-rich regions provide high capacity while carbon-rich regions provide mechanical strength and cohesion. By locally optimizing the composition - silicon particles for capacity and carbon matrix for structural integrity - the electrode achieves both high specific capacity and adequate mechanical strength.
4Duration of action of stationary object
If graphite is used as the active material to ensure structural stability, then the cyclability is improved, but the specific energy is insufficient
Solution Approach 1:
The patent creates a silicon-carbon composite that combines the advantages of both materials: silicon provides high lithium storage capacity (3579 mAh/g theoretical) while the carbon matrix provides structural stability, conductivity, and cyclability. This composite approach achieves specific energy levels unattainable with graphite alone while maintaining acceptable cycle life.
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 approach improves the cyclability and specific capacity of lithium-ion batteries by reducing silicon diffusion and volume expansion, leading to increased cycle life and stability of the negative electrode.
Implementation Method 1
raising the temperature of the homogeneous gas mixture to the deposition temperature, wherein the deposition temperature is between 500 and 1200 °C
Implementation Method 2
tertiary composite particles are formed by agglomerating these secondary particles into a network with a conductive outer layer
Data Source
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AI summary
This invention relates to a method for manufacturing secondary composite particles, secondary composite particles, a method for manufacturing tertiary composite particles, the tertiary composite particles, and a secondary electrochemical cell utilising the secondary or tertiary composite particles as the active material of the negative electrode of the secondary electrochemical cell, wherein each tertiary composite particle comprises a plurality of secondary composite particles embedded in a second matrix being predominantly made of carbon, wherein each secondary composite particle comprises a plurality of primary particles embedded in a first matrix, wherein the primary particles are predominantly composed of silicon and wherein the first matrix comprises silicon and carbon.