Porous Silicon Anode Particles for Volume-Stable Li-Ion Batteries
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Solution Overview
Problem
Silicon-based negative electrode active material particles in lithium-ion batteries experience significant volume expansion and contraction during charging and discharging, leading to variations in restraint pressure, which affects battery performance.
Innovation Solution
Developing negative electrode active material particles with a clathrate type II crystalline phase and pores of 10 nm or less, optimized through mechanical milling and heat treatment of Si particles with NaH, to reduce expansion and contraction by enhancing the crystallinity and pore structure, thereby stabilizing the battery's restraint pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Si particles are used as negative electrode active material, then energy density is increased, but volume expansion and contraction during charging and discharging occurs
Solution Approach 1:
The patent introduces pores with a volume of 0.05 cc/g or more into the Si particle structure. These pores act as internal voids that can accommodate the volume expansion of Si during lithiation, preventing particle cracking and maintaining structural integrity. The porous structure allows the Si to expand into the void spaces rather than externally, thus reducing the overall volume variation of the electrode material.
Solution Approach 2:
The patent creates a composite structure by combining Si particles with a specific crystalline phase (clathrate type II) and incorporating pores within the particle matrix. This composite approach integrates the high capacity of Si with the structural stability provided by the crystalline phase and the volume-buffering capacity of the pores, achieving both high energy density and volume stability.
2Reliability
If expansion and contraction of active material is reduced, then restraint pressure variation is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameters for the pore volume (0.05 cc/g or more) and the crystalline phase composition (clathrate type II with specific XRD peak intensities). By controlling these parameters, the invention achieves optimal balance between volume stability and manufacturability. The quantified parameters provide clear manufacturing targets that simplify the production process while ensuring the desired performance.
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 approach effectively reduces the expansion and contraction of negative electrode active material particles during charging and discharging, minimizing variations in restraint pressure and enhancing the charging and discharging capacity of lithium-ion batteries.
Implementation Method 1
mechanically milling Si particles with pores inside and NaH particles
Implementation Method 2
performing heating at a heating temperature of 250° C. to 500° C. for a heating time of 1 hour to 60 hours to obtain NaSi alloy particles
Implementation Method 3
a half width W (°) of a peak at 2θ=31.72°±0.50° in an X-ray diffraction test using CuKα
Data Source
AI summary
Negative electrode active material particles of the present disclosure are Si particles with pores inside primary particles and having a clathrate type crystalline phase, and satisfying the following relationship: 0.061≤V/W. Here, V is a volume of pores having a pore diameter of 10 nm or less and W is a half width of a peak at 2θ=31.72°±0.50° in an X-ray diffraction test using CuKα.