Silicon-Carbon Anode Material With Uniform Metal Silicate Doping
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Solution Overview
Problem
Existing anode materials face challenges in achieving uniform distribution of dopant elements and balanced growth of silicon crystal grains, leading to uneven performance and safety issues in secondary batteries.
Innovation Solution
An anode material with a silicon-based core and carbon layer, where the metal M element is uniformly distributed, ensuring standard deviations k1≤10 and k2≤5, with k2/k1 between 0.1 and 1, achieved through in-situ doping technology using vacuum co-evaporation and carbon coating.
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 easily generated
Solution Approach 1:
The patent changes the physical state parameter of magnesium from solid (metal powder) to gaseous (vapor), enabling uniform diffusion and distribution throughout the silicon oxide particles during vapor-phase reaction, thereby eliminating the non-uniform distribution and by-product formation associated with solid-state reactions
Solution Approach 2:
The patent replaces the mechanical mixing and solid-state diffusion process with a vapor-phase chemical reaction process, where magnesium vapor uniformly penetrates and reacts with silicon oxide particles, achieving homogeneous distribution without mechanical intervention
2Reliability
If in-situ gaseous magnesium doping technology is used, then the initial Coulombic efficiency reaches more than 83% and aqueous slurry has good stability, but the local magnesium doping ratio is not controllable and silicon crystal grains grow unbalanced
Solution Approach 1:
The patent implements feedback control by monitoring the reaction progress and adjusting the magnesium vapor flow rate and reaction temperature in real-time, ensuring the magnesium doping ratio remains within the optimal range of 1-10 atomic% and preventing unbalanced crystal grain growth
Solution Approach 2:
The patent makes the doping process dynamic and adjustable by controlling the magnesium vapor introduction rate and reaction conditions, allowing precise control over the final magnesium content and distribution, rather than using a fixed static process
3Duration of action of stationary object
If silicon oxide material is used as anode material, then the specific capacity reaches up to 2100 mAh/g and cycle life is greatly improved compared to crystalline silicon, but the irreversible formation of Li2O and lithium silicate causes low initial coulombic efficiency
Solution Approach 1:
The patent performs preliminary action by pre-doping magnesium into the silicon oxide structure before battery operation, which pre-forms stable magnesium silicate phases that reduce subsequent irreversible reactions with lithium, thereby improving initial coulombic efficiency without sacrificing cycle life
Solution Approach 2:
The patent converts the potentially harmful irreversible reaction between silicon oxide and lithium into a beneficial controlled reaction by having magnesium present to form stable magnesium silicate phases, which actually consume the lithium that would otherwise be lost in uncontrolled side reactions, thereby improving efficiency
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 and separation of nano-silicon and silicon oxide domains.
Implementation Method 1
the magnesium vapor generated by heating starts to react from the outside of the silicon oxide particles and gradually diffuses into the particles
Implementation Method 2
adding an exogenous reductant metal element, reacting with the oxygen element in the silicon oxide, and performing reduction to generate the nano-silicon
Implementation Method 3
the reaction of silicon oxide vapor generated by the silicon and silicon dioxide mixture under heating conditions
Implementation Method 4
in the process of mixed deposition of magnesium vapor and silicon oxide vapor
Data Source
AI summary
An anode material including a silicon-based core and a carbon layer disposed on at least part of a surface of the silicon-based core are described. 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.