Silicon Oxide Anode Material With Metal Doping for Expansion Damage Control
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face challenges with volume expansion and damage during charge/discharge cycles, leading to reduced lifespan and capacity issues.
Innovation Solution
A negative electrode active material comprising silicon-based oxide particles with a metal (Li or Mg) distributed on their surface or inside, having a compressive fracture strength of 170 MPa to 380 MPa, and Si crystal grains of 3 nm to 20 nm, is developed. This material is prepared by mixing silicon-based oxide particles with a metal-containing material and heat-treating the mixture at 1,050°C to 1,350°C, enhancing the particle strength and minimizing structural changes during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to achieve high capacity and high energy density, then the battery capacity increases about 10 times compared to carbon-based materials, but volume expansion and cracks/damage occur during charge/discharge cycles leading to reduced lifespan
Solution Approach 1:
The patent embeds silicon particles inside a porous carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nesting approach allows silicon to expand and contract during charge/discharge cycles while being constrained by the carbon matrix, preventing cracks and damage while maintaining high capacity.
Solution Approach 2:
The patent creates a composite material consisting of silicon particles combined with carbon matrix and conductive metal particles. This composite structure combines the high capacity of silicon with the structural stability of carbon and the conductivity of metal, resolving the contradiction between high capacity and lifespan durability.
2Use of energy by moving object
If silicon-based negative electrode active material is used to achieve high energy density with thin electrode, then the energy density increases, but cracks/damage to active material particles occur due to volume expansion
Solution Approach 1:
The patent employs a porous carbon matrix that acts as a flexible container around silicon particles. This carbon shell can accommodate volume changes of silicon during charge/discharge without breaking, maintaining particle integrity while enabling high energy density.
Solution Approach 2:
The patent uses a porous carbon matrix structure that provides space for silicon expansion while maintaining structural integrity. The porous structure allows volume change accommodation without causing cracks, preserving active material particle strength during cycling.
3Ease of manufacture
If conventional negative electrode active material is used, then the battery structure is simple and easy to manufacture, but the energy density is low and capacity is limited
Solution Approach 1:
The patent merges multiple materials (silicon, carbon, and conductive metal particles) into a single integrated composite structure that can be manufactured in one process. This combining approach achieves high energy density while maintaining manufacturing simplicity through a unified synthesis method.
Solution Approach 2:
The patent changes the physical and chemical parameters of the negative electrode material by using silicon-based compounds with specific crystal structures and combining them with conductive metals. This parameter change enables high energy density while the overall composite structure remains manufacturable using conventional techniques.
4Quantity of substance
If silicon-based negative electrode active material is used, then high capacity is achieved, but volume expansion during charge/discharge causes damage and reduces lifespan
Solution Approach 1:
The patent uses the carbon matrix as a counteracting structure that restrains the volume expansion of silicon particles during charge/discharge. The carbon matrix provides mechanical counterbalance to the expansion forces, preventing damage while allowing high capacity operation.
Solution Approach 2:
The patent pre-structures the carbon matrix with appropriate porosity and mechanical properties before combining with silicon particles. This preliminary preparation of the carbon framework ensures it can accommodate future volume expansion of silicon without causing damage during battery operation.
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 effectively prevents active material damage and improves the lifespan and capacity properties of the negative electrode, maintaining excellent energy density and reducing volume expansion, thereby enhancing the overall performance of the battery.
Implementation Method 1
heat-treating the mixture at 1,050°C to 1,350°C
Implementation Method 2
a metal distributed on a surface, inside, or on the surface of and the inside the silicon-based oxide particles
Data Source
AI summary
The present invention relates to a negative electrode active material including silicon-based oxide particles and a metal distributed on a surface, inside, or on the surface of and the inside the silicon-based oxide particles, wherein compressive fracture strength measured at a pressure of 100 mN is 170 MPa to 380 MPa, and the silicon-based oxide particles contain Si crystal grains having a crystal grain size of 3 nm to 20 nm.