Porous Spherical Negative Active Material for Lithium Battery Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face cycle-life deterioration due to volume expansion of Si-based and Sn-based negative active materials during charge and discharge cycles, leading to poor energy density and commercial viability issues.
Innovation Solution
A negative active material is developed with spherical assemblies of flake-shaped materials (Si, Sn, Al, Ge, or their alloys) that include pores to absorb volume expansion, mixed with a polymer binder and fired at low temperature to form a structure with controlled porosity and thickness, enhancing cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based or Sn-based materials are used as negative active materials, then capacity is improved, but volume expansion occurs during charge and discharge cycles leading to poor cycle-life
Solution Approach 1:
The patent employs porous carbonaceous materials as the negative active material, where the porous structure provides void spaces that can accommodate volume expansion of Si-based or Sn-based materials during lithiation, preventing structural degradation and maintaining cycle-life while preserving high capacity
Solution Approach 2:
The patent creates composite structures combining Si-based or Sn-based materials with carbonaceous materials, where the carbonaceous matrix provides structural stability and accommodates volume changes, while the Si/Sn components provide high capacity, achieving both improved capacity and maintained cycle-life
2Reliability
If carbonaceous materials are used as negative active material, then cycle-life is improved, but irreversible capacity of 5 to 30% occurs during first several cycles reducing energy density
Solution Approach 1:
The patent optimizes parameters such as pore size distribution, porosity (20-80%), and particle size of carbonaceous materials to minimize irreversible capacity while maintaining cycle-life, finding that controlled porosity reduces initial electrolyte consumption and improves first-cycle efficiency
3Quantity of substance
If metal negative active materials (Si, Sn) are included at 30% or less, then initial coulomb efficiency decreases, but capacity retention rate deteriorates remarkably after 150 cycles
Solution Approach 1:
The porous carbonaceous material structure allows for optimized metal content by providing sufficient void space to accommodate volume expansion even at higher metal concentrations, enabling improved capacity retention without sacrificing initial coulomb efficiency
Solution Approach 2:
The patent creates local regions with different properties within the composite structure, where Si/Sn particles are distributed within the porous carbonaceous matrix, allowing each component to perform its optimal function - Si/Sn providing capacity and carbonaceous material providing structural stability and ion transport pathways
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 porous spherical assemblies effectively suppress volume expansion, improving the cycle-life and energy density of lithium batteries, maintaining high discharge capacity retention after multiple cycles.
Implementation Method 1
materials that are capable of reversibly intercalating or deintercalating lithium ions in positive and negative electrodes
Implementation Method 2
an arrangement of flake-shaped materials that are arranged to form a central pore inside the spherical assembly
Data Source
AI summary
A negative active material for rechargeable lithium batteries and a method of manufacturing the negative active material are provided. The negative active material for rechargeable lithium batteries includes at least one generally spherical assembly having flake-shaped materials that are capable of doping and dedoping lithium, and are arranged in a generally spherical shape defining a central pore. The negative active material imparts improved cycle-life characteristics.