Silicon-Carbon Particles With Tuned Surface Layer for Stable Cycling
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Solution Overview
Problem
Electrochemical apparatuses face issues with performance variability due to differences in negative electrode active materials, leading to deteriorated cycling performance, swelling, and rate performance, primarily attributed to significant volume changes in silicon-based materials during charge and discharge cycles.
Innovation Solution
The use of silicon-carbon particles with a controlled surface layer thickness and average particle size, combined with graphite particles, along with a uniform distribution of silicon elements, enhances the stability and performance of the negative electrode active material, including a surface layer composition of C, O, F, P, N, Si, and Li, and a preparation method involving a porous carbon framework with metal salts to ensure uniform deposition of silicon-based particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based materials are used as negative electrode active material, then energy density is improved, but volume change during charge and discharge cycles deteriorates cycling performance and causes swelling
Solution Approach 1:
Silicon particles are embedded within carbon particles to form silicon-carbon composite particles. The carbon matrix acts as a container that accommodates the silicon particles, allowing the silicon to expand and contract during charge-discharge cycles without compromising the structural integrity of the electrode. This nested structure resolves the contradiction by enabling high energy density from silicon while maintaining cycling performance through the stabilizing carbon framework.
Solution Approach 2:
The invention uses composite materials by combining silicon and carbon to form silicon-carbon composite particles. The composite structure leverages the high capacity of silicon while the carbon component provides structural stability and conductive pathways. This composite approach directly addresses the technical contradiction by integrating the beneficial properties of both materials to achieve both high energy density and reliable cycling performance.
2Use of energy by moving object
If silicon-based materials are used as negative electrode active material, then energy density is improved, but swelling during charge and discharge cycles deteriorates rate performance
Solution Approach 1:
Silicon particles are nested within carbon particles, creating a structure where the carbon matrix constrains silicon expansion. This prevents swelling that would otherwise block ion transport pathways, thereby maintaining rate performance while utilizing silicon's high energy density.
Solution Approach 2:
The silicon-carbon composite structure combines the high capacity of silicon with the structural stability and conductivity of carbon. The carbon component maintains porosity and conductive networks even during silicon expansion, ensuring that rate performance is not compromised despite the high energy density achieved through silicon utilization.
3Reliability
If surface layer thickness is increased to stabilize silicon-carbon particles, then volume change is reduced, but ion transport resistance increases
Solution Approach 1:
Instead of creating a thick uniform surface layer, the invention uses a thin surface layer (5-50 nm) with specific compositional characteristics. This thin layer provides sufficient stabilization to control volume change while minimizing the barrier to ion transport. The local quality of the surface layer is optimized to balance protection and permeability, resolving the contradiction between volume stability and ion transport rate.
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 cycling performance, swelling suppression, and rate performance by stabilizing the volume changes of silicon-carbon particles, inhibiting electrolyte decomposition, and ensuring uniform distribution, thereby enhancing the overall electrochemical apparatus performance.
Implementation Method 1
providing a silicon-containing precursor on the porous carbon framework containing the metal salt, so that the silicon-containing precursor undergoes a chemical vapor reaction to form silicon-based particles, and the silicon-based particles deposit in the pores of the porous carbon framework
Data Source
Figure 1
AI summary
An electrochemical apparatus includes a negative electrode plate and an electrolyte, where the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector and containing a negative electrode active material, the negative electrode active material including silicon-carbon particles and graphite particles. A surface of each silicon-carbon particle has a surface layer, a thickness of the surface layer is c µm, an average particle size of the silicon-carbon particles is d µm, and 0.42%<c/d<16.0%.