Carbon-Coated Silicon Anode Material With Uniform Metal Silicate Doping
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Solution Overview
Problem
Existing anode materials, particularly silicon oxide-based materials, suffer from non-uniform distribution of dopant elements and unbalanced growth of silicon crystal grains, leading to low initial coulombic efficiency, poor cycle performance, and safety risks due to uneven volume expansion.
Innovation Solution
An anode material with a silicon-based core coated by a carbon layer, where the metal M element is uniformly distributed, achieving a specific standard deviation in content values through in-situ doping technology, ensuring uniform distribution of metal silicate to separate nano-silicon and silicon oxide domains, reducing volume change and improving electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If solid-state doping reduction reaction using magnesium metal powder is used, then the physical and chemical properties of magnesium silicate are stable and aqueous slurry stability is good, but the magnesium distribution is non-uniform and by-products such as magnesium silicide and magnesium oxide are generated
Solution Approach 1:
The patent replaces the solid-state mechanical diffusion process with a chemical vapor deposition process. Magnesium vapor and silicon oxide vapor are mixed in the gas phase and then deposited simultaneously, eliminating the diffusion-controlled limitations of solid-state reactions and achieving uniform distribution without by-products.
Solution Approach 2:
The patent changes the physical state of the reactants from solid to gas phase. By using vapor-phase magnesium and vapor-phase silicon oxide instead of solid powders, the reaction kinetics and diffusion characteristics are fundamentally altered, enabling uniform mixing and deposition while avoiding the formation of unwanted by-products.
2Reliability
If in-situ gaseous magnesium doping technology is used, then the initial Coulombic efficiency is improved and aqueous slurry stability is good, but the local magnesium doping ratio is uncontrollable and silicon crystal grains grow unbalanced
Solution Approach 1:
The patent merges the doping process with the deposition process. Magnesium vapor and silicon oxide vapor are introduced simultaneously and deposited together in the same reaction chamber, ensuring that magnesium is uniformly incorporated into the silicon oxide structure during deposition, thereby controlling the doping ratio and preventing unbalanced crystal grain growth.
Solution Approach 2:
The patent employs controlled vapor deposition with regulated heating zones and vapor flow rates. By monitoring and controlling the deposition conditions, the magnesium doping ratio can be precisely adjusted and maintained uniform throughout the deposited layer, preventing local variations that would cause unbalanced crystal grain growth.
3Productivity
If magnesium vapor diffusion into silicon oxide particles is used, then the reduction reaction can proceed, but the diffusion rate is slow and complete uniform doping is difficult to achieve
Solution Approach 1:
The patent replaces the slow solid-state diffusion mechanism with rapid gas-phase mixing and deposition. Magnesium vapor and silicon oxide vapor mix uniformly in the gas phase before deposition, achieving both high reaction rate and uniform doping distribution simultaneously, overcoming the fundamental limitation of solid-state diffusion.
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 anode material exhibits high initial coulombic efficiency, good cycle performance, and low volume expansion, with improved stability and safety due to uniform metal silicate distribution, enhancing the overall performance of secondary batteries.
Implementation Method 1
heating evaporation respectively to obtain a metal source gas and a silicon oxide gas
Implementation Method 2
mixing and condensing the silicon oxide gas and the metal source gas to obtain a core material
Data Source
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Figure 5
AI summary
An anode material includes a silicon-based core and a carbon layer coated on at least part of a surface of the silicon-based core. The silicon-based core includes nano-silicon and a silicate containing a metal M element. The anode material is subjected to section and energy spectrum analysis, k1≤10, k2≤5, and 0.1<k2/k1≤ 1 are satisfied. The method for preparing the anode material includes: heating and evaporating the pre-disproportionated silicon oxide material and M metal source material to obtain silicon oxide gas and metal source gas; mixing and condensing these two gases to obtain the core material; and performing carbon coating treatment to obtain the anode material. The metal silicate in the prepared anode material effectively separates a nano-silicon domain and a silicon oxide domain, is relatively uniform in distribution, and has high initial Coulombic efficiency and good cycle performance.