Si/C Composite Anode for Lithium Battery Volume Expansion
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Solution Overview
Problem
Lithium secondary batteries face challenges with high volume expansion and limited capacity due to the use of silicon anode materials, which lead to reduced battery life and capacity retention, and existing solutions like nanoscale silicon particles and carbon coatings do not effectively address these issues.
Innovation Solution
A method for preparing a silicon (Si)/carbon (C) composite by mixing aromatic and linear silicon alkoxide compounds with an organic solvent, followed by heat treatment and acid treatment to disperse carbon in an atomic state within silicon particles, enhancing electrical conductivity and minimizing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material to increase capacity, then capacity increases, but volume expansion occurs during charging
Solution Approach 1:
Carbon atoms are nested within the silicon particle interior during the sol-gel process, creating a core-shell structure where carbon is embedded in silicon. This nested configuration allows the carbon to act as an internal buffer that accommodates silicon's volume expansion during lithium insertion, preventing external structural damage while maintaining high capacity
Solution Approach 2:
The invention creates a composite material structure where carbon and silicon are combined at the atomic level within the particle. The carbon-silicon composite leverages carbon's structural stability and silicon's high capacity, achieving a material that exhibits both high capacity and reduced volume expansion through the synergistic combination of the two elements
2Volume of moving object
If carbon coating is applied to silicon particles, then volume expansion is buffered, but cracks occur in carbon during charging
Solution Approach 1:
Instead of applying a uniform carbon coating on the particle surface, the invention creates local carbon regions dispersed throughout the silicon particle interior. This localized carbon distribution allows each carbon region to independently buffer volume changes in its surrounding silicon matrix, preventing stress concentration and crack formation that would occur with a uniform coating
Solution Approach 2:
The carbon-dispersed silicon particle structure creates an internally porous or heterogeneous configuration where carbon atoms are distributed throughout the particle volume. This internal porosity allows the structure to accommodate volume changes during charging-discharging cycles without generating the mechanical stress that leads to surface cracking in conventional coated structures
3Volume of moving object
If nanoscale silicon particles are used, then volume change buffering is achieved, but manufacturing cost increases
Solution Approach 1:
The sol-gel process enables the silicon particles to self-organize and self-dope with carbon atoms during a single low-temperature treatment step. The carbon-containing precursor decomposes and deposits carbon directly within the forming silicon particles, eliminating the need for separate nanoparticle synthesis and carbon coating steps, thereby significantly reducing manufacturing complexity and cost
4Reliability
If carbon is dispersed in atomic state in silicon, then electrical conductivity is improved, but manufacturing precision is required
Solution Approach 1:
The sol-gel process acts as an intermediary mechanism that facilitates uniform carbon distribution within silicon particles. By using a carbon-containing precursor that participates in the sol-gel reaction, carbon is introduced and distributed uniformly during the self-assembly process of particle formation, avoiding the need for precise post-synthesis dispersion techniques
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 Si/C composite improves the charge and discharge capacity, capacity retention, and electrical conductivity of lithium secondary batteries, leading to enhanced life characteristics by uniformly dispersing carbon within silicon particles without chemical bonding, thus minimizing volume expansion.
Implementation Method 1
mixing an aromatic group-containing silicon alkoxide compound selected from the group consisting of phenyltriethoxysilane (PTES), phenyltrimethoxysilane (PTMS), and diphenyldiethoxysilane (DDES), or a mixture of two or more thereof and a linear silicon alkoxide compound selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), tetrapropyl orthosilicate (TPOS), and tetrabutyl orthosilicate (TBOS), or a mixture of two or more thereof with an organic solvent to form a SiO2/C composite
Implementation Method 2
mixing the SiO2/C composite obtained in step i) with an alkali metal or an alkaline earth metal and heat treating the mixture in a temperature range of 350°C to 1400°C and in an inert atmosphere to reduce SiO2
Implementation Method 3
acid treating the heat-treated product obtained in step ii) to remove an oxide
Implementation Method 4
carbon is dispersed in an atomic state in a silicon particle
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Provided are a Si/C composite, in which carbon (C) is dispersed in an atomic state in a silicon (Si) particle, and a method of preparing the Si/C composite. Since the Si/C composite of the present invention is used as an anode active material, electrical conductivity may be further improved and volume expansion may be minimized. Thus, life characteristics of a lithium secondary battery may be improved.