Magnesium-Doped Silicon Anode Material for Stable Li-Ion Cycling
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Solution Overview
Problem
Lithium secondary batteries face issues with stability and electrical properties due to the contraction and expansion of silicon-based active material particles, leading to poor contact between particles, short circuits, and degradation of ionic conductivity and high-temperature stability.
Innovation Solution
An anode active material comprising a carbon-based material and silicon-based material doped with magnesium, with controlled particle sizes and porosity, and optionally including a carbon coating, to enhance structural stability and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material particles are used to increase energy density, then capacity is improved, but particle contraction and expansion occur during charging/discharging leading to poor contact and short circuits
Solution Approach 1:
A carbon coating layer is formed on the surface of the silicon-based active material particles. This carbon shell acts as a flexible protective layer that accommodates the volume changes of silicon during lithiation and delithiation, preventing particle fracture and maintaining electrical contact while allowing lithium ion diffusion.
Solution Approach 2:
The carbon coating layer is designed with a porous structure having controlled porosity (0.03 mL/g to 0.08 mL/g). These pores provide buffer space for silicon expansion, facilitate electrolyte penetration and lithium ion diffusion, and prevent mechanical stress concentration that would lead to particle failure.
2Stability of the object's composition
If the composition and structure of anode active material are changed to improve stability, then particle stability is improved, but ionic conductivity and high-temperature stability are degraded
Solution Approach 1:
The porosity of the carbon coating layer is precisely controlled within the range of 0.03 mL/g to 0.08 mL/g. This optimized porosity parameter balances structural stability with ionic conductivity - providing enough void space for expansion while maintaining sufficient density for lithium ion transport and electrical conductivity.
Solution Approach 2:
A composite structure is created combining silicon-based active material particles with a carbon-coated porous layer. The carbon coating provides structural stability and conductivity, while the porous structure accommodates volume changes. This composite design synergistically combines the high capacity of silicon with the stability and conductivity of carbon.
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 solution improves the stability and electrical properties of lithium secondary batteries, enhancing rapid charging capabilities, room temperature life-span, and high-temperature performance by suppressing particle contraction and expansion, and reducing side reactions.
Implementation Method 1
silicon-based active material particles doped with magnesium
Implementation Method 2
At least some of the silicon-based active material particles include pores
Implementation Method 3
the silicon-based active material particles may further include a carbon coating
Data Source
AI summary
An anode active material for a secondary battery includes a carbon-based active material, and silicon-based active material particles doped with magnesium. At least some of the silicon-based active material particles include pores, and a volume ratio of pores having a diameter of 50 nm or less among the pores is 2% or less based on a total volume of the silicon-based active material particles.