Porous Silicon Anode Particles for Lithium Battery Volume Expansion
Solution Overview
Problem
Lithium secondary batteries face challenges with graphite anode active materials due to low energy density, volumetric changes during charge and discharge leading to performance degradation, and increased risk of side reactions with electrolytes, which can cause fires or explosions.
Innovation Solution
The development of porous silicon-based particles with nonlinear pores formed on silicon or SiOx particles, which are more easily dispersed in anode active material slurries, minimize side reactions, and reduce volume expansion during charge and discharge by increasing the specific surface area and accommodating volume changes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as anode active material, then long lifespan and excellent reversibility are achieved, but energy density per unit volume is low and side reactions with electrolyte occur at high discharge voltage
Solution Approach 1:
The patent applies porous silicon-based particles with controlled pore structures to replace traditional graphite anode materials. The porous structure provides high theoretical capacity (4,200 mAh/g) while the nonlinear pore configuration (branches connecting to surface open pores) accommodates volume expansion during lithium insertion/extraction, preventing particle fracture and maintaining long cycle life. This resolves the contradiction between achieving high energy density and ensuring long lifespan.
2Stability of the object's composition
If silicon particles are reduced to nano size, then volumetric change variations are reduced, but synthesis uniformity is difficult and side reactions with electrolyte increase due to maximized surface area
Solution Approach 1:
The patent creates local quality differentiation through the porous structure design where the interior contains nonlinear pores for volume accommodation while the surface has controlled open pores for electrolyte interaction. The oxide layer (5-50 nm thick) provides localized protection at the surface, reducing side reactions while the bulk porous structure handles volumetric changes. This resolves the contradiction between stability and harmful surface reactions.
Solution Approach 2:
The patent employs composite silicon-based particles combining silicon core with oxide layer coating and porous structure. This composite design integrates the high capacity of silicon with the protective and structural benefits of the oxide layer and porous architecture, achieving both reduced volumetric variation and minimized side reactions with electrolyte.
3Quantity of substance
If silicon-based anode active material is used, then high lithium capacity is achieved, but volumetric change of 300% or more causes conductive network damage and contact resistance increase
Solution Approach 1:
The patent utilizes porous silicon-based particles where the porous structure (5-50% porosity with nonlinear pores) provides internal space to accommodate up to 300% volumetric expansion during lithium insertion without fracturing the particle or damaging the conductive network. The open pores on the surface and branching internal pores allow the structure to expand and contract while maintaining structural integrity and electrical conductivity throughout charge-discharge cycles.
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 use of porous silicon-based particles with nonlinear pores enhances the dispersibility and stability of anode active materials, reduces side reactions, and improves the life and rate characteristics of lithium secondary batteries by controlling volume expansion and increasing contact area with the electrolyte.
Implementation Method 1
adding a metal catalyst to the etching solution, wherein the metal catalyst is in a reduced state
Implementation Method 2
metal assisted chemical etching of highly resistive silicon in order to produce porous silicon, which is very difficult using an electrochemical method, with Na 2 S 2 O 8 or KMnO 4 as oxidizers
Implementation Method 3
removing an oxide layer present on surfaces of silicon (Si) or SiO x (0≤x≤2) particles
Implementation Method 4
the nonlinear pores include open pores in the surface of the particle, the porous silicon-based particle suppress the volume expansion of an anode active material during charge and/or discharge
Data Source
Figure 1~2
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AI summary
Provided are a porous silicon-based particle including a silicon (Si) or SiOx(0<x<2) particle, wherein the particle includes a plurality of nonlinear pores, and the nonlinear pores are formed as open pores in a surface of the particle, and a method of preparing the porous silicon-based particles. Porous silicon-based particles according to an embodiment of the present invention may be more easily dispersed in an anode active material slurry, may minimize side reactions with an electrolyte, and may reduce volume expansion during charge and discharge. Also, according to an embodiment of the present invention, the shape, form, and size of pores formed in the porous silicon-based particle may be controlled by adjusting the type of a metal catalyst, the concentration of the catalyst, and etching time.