Si-Sn-Al Alloy Negative Electrode for Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries using Si-based negative electrode materials face challenges with phase transition from amorphous to crystalline state, leading to volume changes and reduced cycle life, which compromises capacity and durability.
Innovation Solution
A negative electrode active material comprising an alloy with Si in the range of 12% to 100% by mass, Sn from 16% to 45% by mass, Al from 18% to 43% by mass, and minimal impurities, which suppresses phase transition and enhances cycle life and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based negative electrode material is used to achieve high capacity, then discharge capacity is improved, but phase transition from amorphous to crystalline state occurs causing volume change and reduced cycle life
Solution Approach 1:
The invention changes the compositional parameters by introducing specific ratios of Sn and Al elements to Si, creating an amorphous alloy system where the specific composition range (Si: 12-100%, Sn: 16-45%, Al: 18-43%) prevents crystalline phase formation during cycling, thereby maintaining structural stability and improving cycle life while preserving high capacity
Solution Approach 2:
The invention creates a composite amorphous alloy material combining Si, Sn, and Al elements in specific proportions. This composite structure leverages the beneficial properties of each element: Si provides high capacity, while Sn and Al suppress phase transition and maintain amorphous structure stability, resulting in a material that achieves both high discharge capacity and excellent cycle durability
2Quantity of substance
If Si content is increased to enhance capacity, then energy density is improved, but volume change during alloying with Li increases reducing electrode durability
Solution Approach 1:
The invention optimizes the compositional parameters by establishing specific content ranges for Si, Sn, and Al elements. By controlling Si content within 12-100% while simultaneously introducing Sn (16-45%) and Al (18-43%), the material achieves high energy density while the Sn and Al components constrain volume expansion and maintain compositional stability during Li alloying cycles
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 Si-Sn-Al-based alloy maintains high capacity and cycle durability, with discharge capacity retention of 92% at the 50th cycle and 55% at the 100th cycle, outperforming conventional materials.
Implementation Method 1
when Si and Li are alloyed, transition from an amorphous state to a crystalline state is generated. As the result, a large volume change occurs, and there is such a problem that a cycle life of the electrode decreases
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The negative electrode active material for an electric device of the present invention has an alloy containing Si in a range from 12% by mass or more to less than 100% by mass, Sn in a range from more than 0% by mass to 45% by mass or less, Al in a range from more than 0% by mass to 43% by mass or less, and indispensable impurities as remains. The negative electrode active material can be obtained, for example, using a multiple DC magnetron sputtering apparatus with Si, Sn and Al as targets. Electric devices to which the negative electrode active material of the present invention is applied have an improved cycle life and are excellent in the capacity and cycle durability.