Si-Sn-Cu Negative Electrode Material for Cycle-Stable Li-Ion Batteries
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Solution Overview
Problem
Alloy-based negative electrode active materials for lithium-ion batteries face challenges with capacity retention and coulombic efficiency due to large volume expansion and contraction during charging/discharging, leading to decreased performance over cycles.
Innovation Solution
A negative electrode active material comprising alloy particles with a specific chemical composition and structure, including phases such as D03, δ, ε, and SiOx, optimized to suppress expansion and contraction, enhancing capacity and coulombic efficiency through a balanced phase composition and volume fraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based negative electrode active materials (Si or Sn) are used to achieve higher capacity, then discharge capacity is improved, but capacity retention ratio deteriorates due to large volume expansion and contraction
Solution Approach 1:
The patent employs a composite material system consisting of Si-Sn alloy particles embedded in a Cu matrix. This composite structure combines the high capacity benefits of Si and Sn alloys with the structural stability of Cu, creating a material that achieves both high discharge capacity and good capacity retention ratio by suppressing excessive volume changes during charging/discharging cycles
Solution Approach 2:
The patent optimizes specific parameter ranges including Si content (6-40 at%), Sn content (13-40 at%), and Cu content (balance) to achieve the desired balance between capacity and retention. By carefully controlling these compositional parameters, the material exhibits suppressed volume expansion while maintaining high lithium ion insertion/extraction capacity
2Quantity of substance
If Si single substance or Sn single substance is used to achieve high capacity, then discharge capacity is improved, but reliability deteriorates due to significant expansion and contraction causing cracking
Solution Approach 1:
The patent creates a heterogeneous structure where Si and Sn alloy particles are locally distributed within a Cu matrix. This local quality distribution allows the Si-Sn particles to provide high capacity while the surrounding Cu matrix provides structural support and constraints, preventing cracking and maintaining integrity during volume changes
Solution Approach 2:
The Cu matrix acts as an intermediary material between the Si-Sn alloy particles and the current collector. This intermediary Cu phase buffers the mechanical stress from volume expansion/contraction, preventing direct transmission of cracking forces to the current collector while maintaining electrical conductivity
3Quantity of substance
If alloy particles with high Si content are used to improve capacity, then discharge capacity is improved, but manufacturing precision becomes difficult to control due to phase composition complexity
Solution Approach 1:
The patent defines specific parameter ranges for Si (6-40 at%), Sn (13-40 at%), and Cu (balance) contents that guide the manufacturing process. By controlling these compositional parameters within specified ranges, the patent achieves consistent formation of the desired Cu-Si-Sn intermetallic phases while maintaining high capacity and good retention performance
Data Source
AI summary
Provided is a negative electrode active material which is excellent in capacity, capacity retention ratio, and a coulombic efficiency when charging/discharging is repeated. The chemical composition of the alloy particles of the negative electrode active material of the present disclosure includes 0.50 to 3.00 mass % of oxygen, and alloy elements containing Sn: 13.0 to 40.0 at % and Si: 6.0 to 40.0 at %, with the balance being Cu and impurities. The structure of the alloy particles includes: one or more types selected from the group consisting of a phase having a D03 structure, and a δ phase; one or more types selected from the group consisting of an ε phase and an η′ phase; and a SiOx phase (x=0.50 to 1.70). The SiOx phase (x=0.50 to 1.70) has a volume fraction of 5.0 to 60.0% and the η′ phase has a volume fraction of 0 to 60.0%.