Two-Dimensional Carbon Coating for High-Capacity Positive Electrodes
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Solution Overview
Problem
Energy storage devices, such as lithium-ion batteries, face challenges in achieving high capacity per weight and volume due to insufficient conductivity of positive electrode active materials, leading to increased weight and reduced performance in electric vehicles.
Innovation Solution
The use of two-dimensional carbon coatings on positive electrode active materials, specifically graphene with a controlled thickness and particle size, enhances conductivity without the need for excessive carbon coating or conduction auxiliary agents, thereby reducing the volume and weight of the positive electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode active material is coated with carbon to increase conductivity, then the conductivity is improved, but the capacity per volume and weight decreases due to the carbon not contributing to charge and discharge
Solution Approach 1:
The patent changes the parameter of carbon coating thickness from conventional 5-30 nm to an ultra-thin 0.3-2.0 nm range, and changes the carbon structure from amorphous or graphitic to two-dimensional graphene sheets. This parameter change allows achieving sufficient conductivity enhancement while minimizing the volume occupied by carbon, thus preserving capacity per volume
Solution Approach 2:
The patent creates a composite structure where ultra-thin two-dimensional carbon sheets are coated on the surface of the positive electrode active material particles. This composite structure combines the high conductivity of graphene with the charge-storage capability of the active material, allowing the carbon to serve dual functions of conduction and space efficiency
2Reliability
If a conduction auxiliary agent is provided to ensure electrical conduction, then the conductivity is improved, but the capacity decreases due to the auxiliary agent filling space in the positive electrode active material
Solution Approach 1:
The patent extracts the conduction function from a separate auxiliary agent and integrates it directly onto the surface of the active material particles through ultra-thin carbon coating. This eliminates the need for additional conduction agents that would occupy space and reduce capacity, as the coating itself serves as the conduction pathway
Solution Approach 2:
The ultra-thin two-dimensional carbon coating serves multiple functions simultaneously: it provides electrical conduction, maintains structural integrity, and occupies minimal space. This multi-functionality replaces the need for separate conduction auxiliary agents, volume, and weight
3Reliability
If the thickness of carbon coating is increased to improve conductivity, then the conductivity is enhanced, but the volume of the positive electrode increases
Solution Approach 1:
The patent employs ultra-thin two-dimensional carbon films (0.3-2.0 nm) as conformal coatings on the active material particles. These thin films provide sufficient electrical conduction while occupying negligible volume, thus enhancing conductivity without increasing the overall volume of the positive electrode
Solution Approach 2:
The patent transitions from conventional three-dimensional carbon structures (particles, fibers) to two-dimensional graphene sheets for coating. This dimensional change allows the carbon to provide extensive surface coverage and conduction pathways with minimal thickness, thereby improving conductivity while minimizing volume occupation
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 energy storage devices with improved charge and discharge characteristics and higher capacity per volume and weight, addressing the weight and performance issues in electric vehicles.
Implementation Method 1
A feature of graphene is high conductivity. The conductivity of graphene is 10^6 S/cm or higher and is higher than that of silver.
Implementation Method 2
Two-dimensional carbon, which is one of materials having a structure expanding two-dimensionally, is formed by stacking 1 to 10 sheets of graphene and has a property different from that of a normal metal foil or the like.
Data Source
AI summary
An energy storage device having high capacity per weight or volume and a positive electrode active material for the energy storage device are manufactured. A surface of a main material included in the positive electrode active material for the energy storage device is coated with two-dimensional carbon. The main material included in the positive electrode active material is coated with a highly conductive material which has a structure expanding two-dimensionally and whose thickness is ignorable, whereby the amount of carbon coating can be reduced and an energy storage device having capacity close to theoretical capacity can be obtained even when a conduction auxiliary agent is not used or the amount of the conduction auxiliary agent is extremely small. Accordingly, the amount of carbon coating in a positive electrode and the volume of the conduction auxiliary agent can be reduced; consequently, the volume of the positive electrode can be reduced.