Silicon-Aluminum-Copper Alloy for Lithium Battery Anodes
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Solution Overview
Problem
Lithium secondary batteries using non-carbon based materials like Si and Sn face rapid capacity degradation due to volumetric expansion during charging and discharging, leading to reduced lifespan.
Innovation Solution
A silicon-based alloy comprising silicon, aluminum, and copper, with an alloy matrix of AlCu and Al2Cu, and dispersed silicon nanoparticles, is developed to reduce inactive phase formation and inhibit volumetric expansion, enhancing battery capacity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon based materials like Si and Sn are used as negative active material, then capacity is increased (10 times greater than graphite), but volumetric expansion occurs during charging and discharging leading to rapid capacity degradation
Solution Approach 1:
The patent uses a composite material system consisting of silicon-based alloy particles embedded in a copper matrix. The copper matrix provides structural stability and prevents volumetric expansion, while the silicon-based alloy provides high capacity. This composite structure resolves the contradiction by combining the high capacity of silicon with the dimensional stability of copper.
Solution Approach 2:
The patent changes the physical parameters of the silicon-based material by alloying it with copper and controlling the particle size (D50 between 0.3-10 μm). This parameter modification reduces the volumetric expansion effect while maintaining high capacity, thereby improving capacity retention over charge-discharge cycles.
2Quantity of substance
If silicon-based alloy is used to increase capacity, then discharge capacity is improved, but formation of inactive phase of silicon occurs causing loss of Si
Solution Approach 1:
The copper matrix in the composite structure prevents silicon particles from forming inactive phases by maintaining their structural integrity during charge-discharge cycles. The copper provides a stable environment that prevents silicon aggregation and phase transformation, thereby reducing silicon loss while maintaining high discharge capacity.
Solution Approach 2:
The patent creates local quality differences by having silicon-based alloy particles distributed within a copper matrix. The copper matrix provides local structural support and prevents silicon from undergoing phase transformations that would lead to inactive phase formation, thus reducing silicon loss while maintaining high 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
The silicon-based alloy with a specific atomic fraction ratio of Al and Cu achieves high discharge capacity and improved capacity retention rates by minimizing inactive silicon and increasing the strength and conductivity of the alloy matrix, thus extending the battery's lifespan.
Implementation Method 1
a silicon-based alloy comprising silicon, aluminum, and copper, wherein the silicon-based alloy includes: an alloy matrix including AlCu and Al2Cu; and silicon nanoparticles dispersed in the alloy matrix
Implementation Method 2
Lithium secondary batteries generate electric energy by oxidation and reduction reactions occurring when lithium ions are intercalated into and deintercalated from a positive electrode and a negative electrode
Data Source
AI summary
A negative active material, a negative electrode and a lithium battery including the same, and a method of manufacturing the negative active material are disclosed. The negative active material includes a silicon-based alloy including Si, Al, and Cu. Since the silicon-based alloy includes AlCu and Al2Cu as inactive phases, the lifespan of a lithium battery may be increased.