Graphene Battery Electrode Structure for Low-Additive Conductivity
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in achieving desired output characteristics and energy density due to poor electron conductivity of active materials and uneven distribution of conductive additives, leading to increased electronic resistance and reduced battery performance.
Innovation Solution
A secondary battery electrode comprising a mixture layer with graphene as a conductive additive, where conductive material portions are determined by scanning spreading resistance microscopy to ensure an average aspect ratio of 2.0 or more, optimizing the distribution and resistance values to enhance electron flow and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of conductive additive is reduced to improve energy density, then energy density is improved, but electron conductivity inside the electrode is extremely reduced
Solution Approach 1:
The patent changes the morphological parameters of the conductive additive from traditional spherical carbon black to flake-shaped graphene with specific aspect ratios (2.0 or more). This parameter change allows graphene to form efficient conductive networks with much lower loading amounts (0.01-5 mass%), simultaneously improving energy density and maintaining electron conductivity.
Solution Approach 2:
The patent creates a composite structure where flake-shaped graphene particles form a three-dimensional conductive network within the electrode mixture. This composite approach combines the high aspect ratio geometry of graphene with the active material particles, enabling effective electron transport pathways that reduce the required amount of conductive additive while maintaining conductivity.
2Reliability
If conventional carbon black is used as conductive additive, then electron conductivity is provided, but the conductive additive is easily aggregated and unevenly distributed within the electrode
Solution Approach 1:
The patent uses flake-shaped graphene with large aspect ratios that can wrap around and connect active material particles in a flexible, conformal manner. This thin-film-like structure of graphene flakes creates uniform conductive coverage throughout the electrode without the aggregation problems of spherical carbon black, ensuring stable and even distribution.
3Reliability
If aggregates of conductive additive are large in size, then the conductive network is formed, but the proportion of portions where active material and conductive additive do not contact is large, increasing electronic resistance
Solution Approach 1:
The patent segments the conductive additive into individual flake-shaped graphene particles with controlled sizes and aspect ratios, preventing the formation of large aggregated clumps. This segmentation ensures that graphene flakes remain dispersed and can individually contact multiple active material particles, creating numerous contact points and reducing electronic resistance through a distributed conductive network.
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 approach results in a secondary battery with improved output characteristics and energy density by forming an efficient conductive network, reducing electronic resistance and enhancing the battery's overall performance with a smaller amount of conductive additive.
Implementation Method 1
acquiring a mapping image and a histogram of spreading resistance values of a mixture layer portion by scanning spreading resistance microscopy
Data Source
AI summary
A secondary battery electrode is provided that may achieve a non-aqueous electrolyte secondary battery having a high energy output density with a small amount of a conductive aid. The secondary battery electrode has a mixture layer containing graphene and a secondary battery active substance. The secondary battery electrode has a mean aspect ratio of 2.0 or greater in an electric conductive material portion from a cross section of the secondary battery electrode, as specified by the method described below. The method for specifying the electric conductive material portion comprises: (1) acquiring, by scanning spreading resistance microscopy, a mapping image and a histogram of spreading resistance values for a mixture layer portion; and (2), defining R1 as the lowest resistance value in the histogram, accumulating sequentially from R1 the frequency, defining R2 as the spreading resistance value when the cumulative frequency has exceeded 3% relative to the cumulative frequency over the entire data, further defining R3 as a spreading resistance value of ten times R2, and, with R3 serving as the threshold value, binarizing the mapping image to define as the electric conductive material portion the portion having a resistance value of R3 or lower.