Graphene-Coated Cathode Active Material for Lithium Batteries
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Solution Overview
Problem
Current lithium-ion and lithium-sulfur batteries face challenges due to the poor electrical and thermal conductivity of cathode active materials, leading to reduced lithium ion storage capacity and increased risk of thermal runaway, primarily because of the need for high amounts of non-active conductive additives like carbon black, which dilute the active material and are difficult to incorporate effectively.
Innovation Solution
The use of cathode active material-coated graphene sheets with high active material loading (>80%) and thin coatings (2-100 nm) to form a 3-D network of electron-conducting paths, enhancing both electrical and thermal conductivity, allowing for higher active material utilization and improved battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used as conductive additive to improve electrical conductivity, then electrical conductivity is improved, but the proportion of active material is reduced and lithium ion storage capacity decreases
Solution Approach 1:
The patent changes the key parameter from using traditional carbon black particles to using graphene nanosheets, which have fundamentally different electrical conductivity properties. This parameter change allows achieving the same conductivity improvement with much lower additive content, thereby preserving active material proportion and lithium ion storage capacity.
Solution Approach 2:
The patent creates a composite structure where graphene nanosheets serve as the conductive matrix and carbon black particles are embedded within or on the graphene sheets. This composite approach leverages the superior conductivity of graphene while utilizing the familiar properties of carbon black, achieving enhanced conductivity with minimal non-active material content.
2Reliability
If carbon black is used as conductive additive to improve electrical conductivity, then electrical conductivity is improved, but thermal conductivity remains insufficient and thermal runaway risk increases
Solution Approach 1:
The patent changes the material parameter from carbon black to graphene nanosheets, which possess both superior electrical conductivity and exceptional thermal conductivity. This single parameter change simultaneously addresses both electrical and thermal conductivity requirements, enabling effective heat dissipation while maintaining electrical performance.
3Reliability
If carbon black aggregates are used to form conductive network, then electrical conductivity is achieved, but large amounts of conductive additive are required due to percolation threshold
Solution Approach 1:
The patent transitions from using zero-dimensional carbon black particles to two-dimensional graphene nanosheets. This dimensional change fundamentally alters the percolation behavior, allowing conductive networks to form at much lower concentrations. The planar structure of graphene enables more efficient electron transport pathways compared to spherical carbon black aggregates.
4Reliability
If CNTs or VG-CNFs are used as conductive additive to improve conductivity, then electrical conductivity is improved, but production cost increases and transition metal catalysts remain that adversely affect cycling stability
Solution Approach 1:
The patent employs a cost-effective approach by using graphene nanosheets that can be produced without expensive transition metal catalysts. The method utilizes carbonaceous materials and carbon nanotubes as precursors that are converted to graphene through thermal treatment, eliminating the need for costly and potentially contaminating catalysts while maintaining superior conductivity properties.
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 results in lithium batteries with increased lithium ion storage capacity, improved thermal management, and enhanced cycling stability, enabling high-rate capability and extended cycle life while reducing the need for excessive conductive additives.
Implementation Method 1
form a 3-D network of electron-conducting paths, enhancing both electrical and thermal conductivity
Implementation Method 2
Such a thermally conductive additive would be capable of dissipating the heat generated from the electrochemical operation of the Li-ion battery
Data Source
AI summary
Provided is a cathode (positive electrode) of a lithium battery and a process for producing this cathode. The electrode comprises a cathode active material-coated graphene sheet and the graphene sheet has two opposed parallel surfaces, wherein at least 50% area (preferably greater than 80%) of one of the two surfaces is coated with a cathode active material coating. The graphene material is in an amount of from 0.1% to 99.5% by weight and the cathode active material is in an amount of at least 0.5% by weight (preferably greater than 80% and more preferably greater than 90%), all based on the total weight of the graphene material and the cathode active material combined. The cathode active material is preferably an inorganic material, an organic or polymeric material, a metal oxide/phosphate/sulfide, or a combination thereof. Also provided is a lithium battery, including a lithium-ion, lithium-metal, or lithium-sulfur battery.