Porous Silicon Particles for Lithium-Ion Battery Anodes
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Solution Overview
Problem
Conventional lithium-ion battery negative electrodes using silicon as the active material face issues with large volume changes during charge and discharge, leading to poor cycling characteristics and short battery life due to pulverization, exfoliation, and conductivity loss.
Innovation Solution
The development of porous silicon particles and complex porous silicon particles with a three-dimensional network structure, achieved through spinodal decomposition and dealloying of silicon alloys, which maintain high silicon content and controlled porosity to mitigate volume changes and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode active material to achieve high capacity, then battery capacity is improved, but volume expansion during lithium ion occlusion causes pulverization and exfoliation, resulting in poor cycling characteristics and short battery life
Solution Approach 1:
The patent employs porous silicon particles with controlled pore structures to accommodate volume expansion during lithium ion occlusion. The porous architecture provides internal void space that absorbs expansion stress, preventing pulverization and exfoliation while maintaining structural integrity over multiple charge-discharge cycles, thus improving cycling characteristics without sacrificing capacity
Solution Approach 2:
The patent creates composite structures by combining silicon with other materials to form complex porous silicon particles. This composite approach allows the silicon component to provide high capacity while the composite structure provides mechanical stability and conductivity, resolving the contradiction between capacity and cycling life
2Length of moving object
If conventional manufacturing methods mechanically grind silicon to micro meter size, then particle size is reduced, but conductivity deteriorates and cycling characteristics worsen due to pulverization and exfoliation
Solution Approach 1:
Instead of mechanically grinding silicon which causes pulverization, the patent uses a chemical etching process to create porous structures. This approach reduces particle size to the nanometer scale while forming a controlled porous network that prevents further degradation during cycling, maintaining both small size and structural integrity
Solution Approach 2:
The patent replaces mechanical grinding with chemical etching to reduce particle size. This substitution avoids the mechanical stress that causes pulverization and exfoliation, producing porous silicon particles with controlled morphology and preserved conductivity
3Quantity of substance
If silicon volume expands up to 4 times during lithium ion occlusion, then battery capacity increases, but structural integrity is lost due to repeated expansion and contraction, causing exfoliation and short life
Solution Approach 1:
The patent designs porous silicon particles where the pore structure provides buffer space for volume expansion. The porous architecture allows the silicon to expand and contract within the particle without compromising the overall structural integrity, maintaining both high capacity and stability over multiple cycles
Solution Approach 2:
The patent divides the silicon structure into a network of interconnected pores and walls. This segmentation creates a flexible framework that can accommodate volume changes through local deformation rather than overall collapse, preserving structural integrity during repeated expansion and contraction
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
These particles achieve high capacity and improved cycling characteristics, extending the life of lithium-ion batteries by maintaining structural integrity and conductivity during charge-discharge cycles.
Implementation Method 1
The porous silicon particle has a three-dimensional network structure and comprises silicon microparticles which are joined together and formed by spinodal decomposition
Implementation Method 2
formed by spinodal decomposition and dealloying of silicon alloys
Data Source
AI summary
Porous silicon particles and complex porous silicon particles suitable for negative electrode materials etc. for lithium-ion batteries, which achieve high capacity and good cycling characteristics, are provided. Porous silicon particles formed by the joining of a plurality of silicon microparticles, and having an average particle diameter of 0.1 μm to 1000 μm, a three-dimensional network structure having continuous gaps, an average porosity of 15 to 93%, and a structure in which the particles of a whole particle are uniform. Complex porous silicon particles formed by the joining of a plurality of silicon microparticles and a plurality of silicon compound particles, and characterized by containing a compound of silicon and composite elements, having an average particle diameter of 0.1 μm to 1000 μm, and having a three-dimensional network structure having continuous gaps.