2D Porous Silicon Anodes for Volume Change and Ion Diffusion
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Solution Overview
Problem
Two-dimensional silicon materials used in lithium ion batteries face significant volume changes during charging and discharging, leading to particle breakage and reduced battery capacity due to slow lithium ion transmission.
Innovation Solution
A method to prepare two-dimensional porous silicon by acid etching, involving soaking silicocalcium powder in an acidic solution, thermal treatment, and subsequent hydrofluoric acid treatment to produce a material with accelerated ion transmission and a practical, controllable process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If two-dimensional silicon materials are used in lithium ion batteries, then high theoretical specific capacity is achieved, but volume change as high as 300% causes particle breakage and falling off of active substances
Solution Approach 1:
The patent introduces a porous structure into the two-dimensional silicon material, creating void spaces within the lamellar framework. This porous architecture provides internal buffer space to accommodate the 300% volume expansion during lithium intercalation, preventing particle breakage and maintaining structural integrity while preserving high specific capacity.
Solution Approach 2:
The patent creates a composite structure by combining two-dimensional silicon with a porous framework. This composite architecture integrates the high capacity benefits of silicon with the structural stability of the porous design, allowing the material to withstand repeated expansion and contraction cycles without particle disintegration.
2Quantity of substance
If two-dimensional silicon materials are used, then high specific capacity is achieved, but slow lithium ion transmission rate hinders battery performance
Solution Approach 1:
The porous structure creates additional channels and pathways within the two-dimensional silicon material, allowing lithium ions to penetrate deeper and move more efficiently through the structure. The increased surface area and interconnected pores significantly enhance the lithium ion transmission rate while maintaining the high capacity characteristics of two-dimensional silicon.
3Quantity of substance
If conventional two-dimensional silicon structure is used, then high capacity is achieved, but ions are transmitted at lower speed in the direction perpendicular to the lamellar structure
Solution Approach 1:
The patent transforms the conventional two-dimensional lamellar structure into a three-dimensional porous architecture by introducing vertical channels and void spaces. This dimensional transformation creates additional transmission pathways perpendicular to the original lamellar planes, enabling faster ion transport in all directions while preserving the high capacity benefits of the two-dimensional silicon structure.
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 resulting two-dimensional porous silicon effectively alleviates volume changes and enhances lithium ion diffusion, improving battery performance and capacity retention.
Implementation Method 1
soaking the two-dimensional Si/SiO2 in a hydrofluoric acid solution, centrifuging, and drying under vacuum, to obtain the two-dimensional porous silicon material
Implementation Method 2
In the heating process, siloxene can be fully oxidized into SiOx, and SiOx is disproportionated in further high-temperature treatment to produce uniformly distributed two-dimensional Si/SiO2
Implementation Method 3
thermally treating the siloxene powder in a vacuum environment to obtain two-dimensional Si/SiO2
Implementation Method 4
drying under vacuum to obtain a siloxene powder
Implementation Method 5
thermally treating the siloxene powder in a vacuum environment
Data Source
AI summary
A two-dimensional porous silicon, and a preparation method and use thereof in lithium ion batteries. A silicocalcium powder is soaked in a hydrochloric acid solution, filtered under suction after reaction, and dried to obtain a siloxene powder. The siloxene powder is thermally treated in a vacuum environment, in which siloxene is oxidized into SiOx during the heating process, and SiOx is disproportionated in further high-temperature treatment to produce uniformly distributed two-dimensional Si/SiO2. The two-dimensional Si/SiO2 is soaked in a hydrofluoric acid solution, in which hydrofluoric acid reacts with SiO2. After complete reaction, a two-dimensional silicon material having a porous structure is obtained after repeatedly centrifugation and washing, and drying under vacuum. The two-dimensional porous silicon has a crystal structure and an ultra-thin lamellar structure, effectively alleviate the volume change of the negative electrode material, and accelerate the diffusion of lithium ions when used in a lithium ion battery.