Graphene-Enhanced Cathode Particulates for Lithium Batteries
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Solution Overview
Problem
Current lithium-ion and lithium metal batteries face challenges due to the poor electrical and thermal conductivity of cathode active materials, which requires the use of conductive additives like carbon black, leading to reduced active material capacity and increased risk of thermal runaway. Existing alternatives such as carbon nano-tubes and graphene composites face difficulties in production and conductivity.
Innovation Solution
The development of nano graphene-enhanced particulates, where graphene sheets are bonded with fine cathode active material particles to form secondary particles with high electrical and thermal conductivity, allowing for a 3-D network of electron-conducting paths, thereby enhancing battery performance and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used as a conductive additive to improve electrical conductivity, then the electrode achieves percolation threshold and forms 3-D electron-conducting paths, but the proportion of active material is reduced and total lithium ion storage capacity decreases
Solution Approach 1:
The invention changes the physical form of carbon additive from traditional carbon black particles to expanded graphite particles with high aspect ratio (10-100:1). This parameter change in particle morphology allows the conductive additive to form effective conductive networks at much lower weight percentages (0.1-5%), thereby preserving 95-99% active material proportion while achieving sufficient electrical conductivity.
Solution Approach 2:
The invention transitions from using spherical carbon black particles (0-D) to expanded graphite particles with high aspect ratio (1-D/2-D structure). This dimensional change enables the conductive additive to form more efficient conductive paths with less material, as the high aspect ratio particles can bridge larger distances and create percolation networks more effectively than spherical particles.
2Reliability
If a significant amount of conductive additive is used to achieve sufficient electrical conductivity, then the electrode becomes reasonably conducting, but the concentration of active material is diluted and storage capacity is reduced
Solution Approach 1:
By changing the morphological parameter of the conductive additive from spherical to high aspect ratio expanded graphite, the invention achieves the same electrical conductivity function with significantly reduced additive quantity (0.1-5% vs. 2-15%), thereby maintaining high active material concentration (95-99%) and maximizing lithium ion storage capacity.
3Ease of manufacture
If traditional carbon black aggregates are used as conductive additive, then the material is available in aggregate form, but a large amount is required to reach percolation threshold due to spherical geometry and discrete particle dispersion
Solution Approach 1:
The invention changes the geometric parameter of the conductive additive from spherical (aspect ratio ~1) to high aspect ratio expanded graphite (10-100:1). This parameter change enables the material to form percolation networks at much lower concentrations, as the elongated structure provides more effective conductive pathways per unit mass compared to spherical aggregates.
4Reliability
If carbon black with low electrical conductivity is used, then the resulting electrode remains of relatively low conductivity, but a high proportion of carbon black must be incorporated to make the electrode reasonably conducting
Solution Approach 1:
The invention changes the material form from carbon black to expanded graphite, which inherently possesses higher electrical conductivity along its basal planes. Combined with the high aspect ratio geometry, this material change achieves superior electrode conductivity at very low additive proportions (0.1-5%), eliminating the need to use high proportions of low-conductivity carbon black.
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 nano graphene-enhanced particulates achieve superior electrical conductivity and thermal management, enabling high-rate capable cathodes with improved lithium ion storage capacity and safety, outperforming traditional carbon black and carbon nano-tube based electrodes.
Implementation Method 1
graphene sheets are bonded with fine cathode active material particles to form secondary particles with high electrical and thermal conductivity, allowing for a 3-D network of electron-conducting paths
Implementation Method 2
graphene sheets are bonded with fine cathode active material particles to form secondary particles with high electrical and thermal conductivity
Data Source
AI summary
A nano graphene-enhanced particulate for use as a lithium battery cathode active material, wherein the particulate is formed of a single or a plurality of graphene sheets and a plurality of fine cathode active material particles with a size smaller than 10 μm (preferably sub-micron or nano-scaled), and the graphene sheets and the particles are mutually bonded or agglomerated into an individual discrete particulate with at least a graphene sheet embracing the cathode active material particles, and wherein the particulate has an electrical conductivity no less than 10−4 S/cm and the graphene is in an amount of from 0.01% to 30% by weight based on the total weight of graphene and the cathode active material combined.