Silicon-Carbon Anode Material for Volume-Stable High Capacity
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Solution Overview
Problem
Current negative electrode active materials in secondary batteries face challenges such as reduced initial efficiency and discharge capacity due to irreversible reactions with lithium ions and volume changes during charging/discharging, which affect the battery's service life.
Innovation Solution
A negative electrode active material is developed with silicon-containing composite particles including pores and a metal compound, coated with both an outer and inner carbon layer, resulting in a controlled BET specific surface area of 3 to 15 m2/g, reducing side reactions and volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If silicon-containing particles with high discharge capacity are used, then discharge capacity is improved, but volume change during charging/discharging increases
Solution Approach 1:
The patent applies a carbon coating layer (thin film) on the surface of silicon-containing particles. This carbon shell acts as a flexible protective layer that accommodates volume changes during lithium insertion/extraction while maintaining structural integrity, thus resolving the contradiction between high discharge capacity and volume stability.
Solution Approach 2:
The patent creates composite structures by combining silicon-containing particles with carbon materials and metal compounds. This composite approach allows the silicon core to provide high discharge capacity while the carbon and metal components provide structural stability and accommodate volume changes, resolving the contradiction between power and composition stability.
2Productivity
If metal doping is applied to block irreversible reaction sites, then initial efficiency is improved, but discharge capacity per weight is reduced
Solution Approach 1:
The patent optimizes the type and concentration of metal dopants (such as Mg, Al, or Ti) to achieve the desired balance between initial efficiency and discharge capacity. By carefully controlling doping parameters, the patent blocks irreversible reaction sites while minimizing the weight penalty, thus resolving the contradiction between productivity and power.
3Reliability
If carbon layer is formed to improve conductivity, then electrical conductivity is improved, but uniform disposition of carbon layer is difficult
Solution Approach 1:
The patent uses metal compounds (such as MgO, Al2O3, or TiO2) as intermediary layers between the silicon-containing particles and the carbon coating. These intermediary layers provide a controlled surface that facilitates uniform carbon deposition, ensuring consistent conductivity without compromising layer uniformity, thus resolving the contradiction between reliability and manufacturing precision.
4Ease of manufacture
If large pores are created to remove metal compound, then metal removal is facilitated, but side reaction with electrolytic solution increases
Solution Approach 1:
The patent creates a hierarchical pore structure with different pore sizes and distributions in different regions of the particle. Smaller pores are used for metal compound removal while larger pores are strategically positioned to avoid direct contact with electrolyte, thus facilitating manufacturing while minimizing harmful side reactions, resolving the contradiction between ease of manufacture and object-generated harmful factors.
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 configuration enhances the discharge capacity, initial efficiency, and service life of the battery by minimizing side reactions and volume changes during charging/discharging, while effectively controlling pore size and number.
Implementation Method 1
a technique of forming a carbon layer has been used in order to improve the conductivity of the negative electrode active material
Implementation Method 2
The negative electrode includes a negative electrode active material for intercalating and de-intercalating lithium ions from the positive electrode
Data Source
AI summary
A negative electrode active material including: silicon-containing composite particles including (a) SiOx, wherein 0<x<2, (b) pores, and (c) a Mg compound or a Li compound; an outer carbon layer present on the surface of the silicon-containing composite particle; and an inner carbon layer present inside the pores, in which a BET specific surface area of the negative electrode active material is 3 m2/g to 15 m2/g, a negative electrode including the same, a secondary battery including the negative electrode and a method for preparing the negative electrode active material.