Cu-Sn Alloy Negative Electrode for Lithium-Ion Batteries
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Solution Overview
Problem
Existing negative electrode active materials for lithium-ion batteries, particularly alloy-based ones, face challenges with volume expansion and contraction during charging and discharging, leading to capacity deterioration and reduced cycle characteristics.
Innovation Solution
A negative electrode active material with an alloy phase containing 10 to 20 at% Sn and balanced Cu and impurities, with an oxygen content not exceeding 5000 ppm, undergoes thermoelastic diffusionless transformation to mitigate strain and improve discharge capacity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based negative electrode active materials (Si or Sn) are used to increase capacity, then the volumetric discharge capacity is improved, but the charge-discharge cycle characteristics deteriorate due to large volume expansion/contraction
Solution Approach 1:
The invention changes the chemical composition parameters of the alloy by precisely controlling the Sn content (10-20 at%) and maintaining low oxygen content (≤5000 ppm), which modifies the material's volumetric properties and transformation behavior to reduce expansion/contraction strain while maintaining high capacity
Solution Approach 2:
The invention utilizes thermoelastic diffusionless transformation (martensitic transformation) in the Cu-Sn alloy phase during charging/discharging cycles. This phase transition mechanism allows the material to accommodate volume changes reversibly without significant permanent deformation, thereby improving cycle characteristics while maintaining high volumetric capacity
2Quantity of substance
If Si or Sn single substance is used as negative electrode active material, then the capacity is increased, but cracking occurs in the negative electrode mixture due to significant expansion and contraction
Solution Approach 1:
The invention creates a composite alloy material combining Cu and Sn in specific proportions (10-20 at% Sn), forming a unified crystalline structure that exhibits both high capacity and structural stability. The composite structure prevents cracking by distributing stress uniformly throughout the material during volume changes
Solution Approach 2:
By adjusting the Sn concentration parameter to 10-20 at% and controlling oxygen content to ≤5000 ppm, the invention optimizes the balance between capacity and structural strength, preventing the cracking that occurs in pure Si or Sn materials while maintaining high volumetric capacity
3Quantity of substance
If alloy-based negative electrode active material is used, then the volumetric discharge capacity is improved, but the capacity deteriorates due to loss of electron conductivity from freed active substances
Solution Approach 1:
The invention optimizes the alloy composition parameters (Sn: 10-20 at%, Oxygen: ≤5000 ppm) to ensure the material maintains adequate electron conductivity even after repeated charging/discharging cycles, preventing capacity deterioration from freed active substances
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 enhances the volumetric discharge capacity and charge-discharge cycle characteristics of lithium-ion batteries by reducing strain from volume changes and suppressing oxide formation, resulting in higher capacity retention ratios.
Implementation Method 1
undergoes thermoelastic diffusionless transformation to mitigate strain and improve discharge capacity and cycle characteristics
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2E
AI summary
Provided is a negative electrode active material that can improve the discharge capacity per volume and charge-discharge cycle characteristics. The negative electrode active material according to the present embodiment contains an alloy phase. The alloy phase undergoes thermoelastic diffusionless transformation when releasing metal ions or occluding metal ions. The oxygen content of the negative electrode active material is not more than 5000 ppm in mass.