Porous Carbon Anode Material With SiCx Coating Against Silicon Swelling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based negative electrode materials for lithium secondary batteries face challenges such as significant volume change during charging and discharging, leading to pulverization, electrical disconnection, and reduced cycle life due to the formation of a thick solid electrolyte interface (SEI) layer and oxide films, which hinder the commercialization of high-capacity batteries.
Innovation Solution
A negative electrode active material is developed, comprising a carbon-based particle with pores and a silicon-based coating layer containing silicon carbon compounds, where the silicon carbon compound satisfies SiCx (0<x≤2) and includes Si nano-particles with controlled crystallinity and thickness, formed using chemical vapor deposition to alleviate volume expansion and prevent oxide film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to increase capacity, then charge capacity is improved, but volume change during charging and discharging causes pulverization and reduces cycle life
Solution Approach 1:
The patent embeds silicon particles inside hollow carbon spheres, creating a nested structure where the inner silicon particles are protected by the outer carbon shell. This nesting approach allows the silicon to undergo volume expansion during lithiation while the carbon shell maintains structural integrity, preventing pulverization and electrode disconnection, thus resolving the contradiction between high capacity and cycle life
Solution Approach 2:
The hollow carbon shell acts as a flexible container that can accommodate the volume expansion of silicon particles during charging. The carbon shell maintains its structural integrity while allowing the silicon inside to expand and contract, preventing electrode pulverization and maintaining electrical connectivity throughout charge-discharge cycles
2Quantity of substance
If thick silicon-based coating layer is applied to increase capacity, then charge capacity is improved, but thick SEI layer formation increases battery resistance and reduces cycle life
Solution Approach 1:
The patent creates a localized high-silicon environment inside the hollow carbon spheres, concentrating the capacity-enhancing silicon in specific regions rather than distributing it uniformly. The carbon shell provides a stable, low-reactivity interface with the electrolyte, allowing thick silicon coating for high capacity while preventing excessive SEI formation at the electrode-electrolyte interface, thus maintaining low battery resistance
3Ease of manufacture
If silicon is exposed to air during manufacturing, then oxide film forms on silicon surface, but oxide film formation decreases capacity and depletes electrolyte
Solution Approach 1:
The patent forms the hollow carbon sphere structure and loads silicon particles inside before exposing the material to air during manufacturing. The carbon shell is already in place as a protective barrier, preventing oxygen from reaching and oxidizing the silicon particles. This preliminary protective action eliminates the need for inert atmosphere handling during subsequent manufacturing steps while preserving silicon capacity
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 solution enhances the capacity and cycle life of lithium secondary batteries by reducing stress from volume expansion, preventing electrical isolation, and suppressing oxide film formation, thereby improving the battery's performance and longevity.
Implementation Method 1
the silicon-based negative electrode material causes a significant volume change at the time of intercalation/deintercalation of lithium
Implementation Method 2
when silicon is exposed to the air at the time of pulverizing the negative electrode active material or manufacturing the negative electrode, the silicon reacts with oxygen, such that an oxide film is formed on a surface of the silicon
Data Source
AI summary
Provided is a negative electrode active material for a lithium secondary battery according to the present invention, including a carbon-based particle including pores in an inner portion and/or a surface thereof; and a silicon-based coating layer positioned on a pore surface and/or a pore-free surface of the carbon-based particle and containing silicon carbon compound.