Carbon Fiber Aggregate Diameter Distribution for Dense Battery Electrodes
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Solution Overview
Problem
The challenge is to enhance the packing density and battery performance of pitch-based ultrafine carbon fibers in nonaqueous electrolyte secondary batteries, as their uniform fiber diameter distribution hinders efficient arrangement and high-density packing in electrode mixture layers.
Innovation Solution
A carbon fiber aggregate with a fiber diameter distribution of 100 to 1000 nm and a coefficient of variation of 0.50 to 1.0 is developed, along with specific production steps involving thermoplastic resin removal and carbonization, to increase packing density and conductivity in the electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pitch-based ultrafine carbon fibers with uniform fiber diameter (CV value of 10 to 50%) are used in the electrode mixture layer, then the fiber diameter uniformity is improved, but the packing density and battery performance deteriorate due to inefficient arrangement in gaps between active material particles
Solution Approach 1:
The invention changes the fiber diameter distribution parameter from a narrow uniform distribution (CV value of 10-50%) to a wider distribution (CV value of 80-150%), while maintaining the average fiber diameter in the range of 0.5-5 μm. This parameter change enables carbon fibers to efficiently fill gaps between active material particles of various sizes, thereby improving packing density and battery performance without sacrificing fiber quality
2Quantity of substance
If carbon fibers with larger diameter variation are used to improve packing density, then the packing property is improved, but the fiber diameter uniformity deteriorates
Solution Approach 1:
The invention optimizes the fiber diameter distribution by controlling the coefficient of variation (CV value) to be within 80-150%, which balances packing efficiency with manufacturing precision. This parameter range ensures that carbon fibers can effectively fill interstitial spaces while maintaining sufficient uniformity for consistent performance
3Area of stationary object
If the average fiber diameter is reduced to increase surface area and contact properties, then the contact properties with active material particles are improved, but the mechanical strength and handling properties deteriorate
Solution Approach 1:
The invention optimizes the average fiber diameter to the range of 0.5-5 μm, which provides sufficient surface area for contact with active material particles while maintaining adequate mechanical strength and handling properties. This diameter range balances the competing requirements of surface area and structural integrity
4Reliability
If carbon fibers with higher crystallinity and electroconductivity are used to improve battery performance, then the electroconductivity is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention controls the crystallite interplanar spacing (d002) to be 0.3400 nm or more, which ensures high electroconductivity and crystallinity while maintaining a manufacturable process. This parameter control achieves superior electrical properties without excessively complicating the manufacturing process
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
This approach allows for high-density packing of active material particles, improving electron conductivity and battery performance by forming a conductive path that maintains stability during charge/discharge cycles.
Implementation Method 1
by making use of high electroconductivity and high thermal conductivity of a carbon material
Implementation Method 2
sequentially stabilized, de-polyethylenated, and carbonized/graphitized to produce ultrafine carbon fibers
Data Source
AI summary
With the present invention a carbon fiber aggregate is provided that has an average fiber diameter of 100-1000 nm, and a fiber diameter variation coefficient (CV value) greater than 0.5 and less than or equal to 1.0.