Carbon-Coated Polyanion Electrode for Low AC Resistance
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Solution Overview
Problem
Existing energy storage devices using lithium transition metal compounds with a polyanion structure face challenges in reducing alternating current resistance due to the brittleness of the particles, leading to increased interface resistance and poor adhesion between the substrate and the active material layer during the production process.
Innovation Solution
The particles containing lithium transition metal compounds with a polyanion structure are coated with a first carbon material, ensuring a particle size change of 1.1 nm or less when pressurized from 20 mN to 100 mN, and optionally incorporating a second carbon material such as carbon nanotubes to enhance electron conductivity and reduce deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If particles containing lithium transition metal compound having a polyanion structure are used as active material, then energy storage capacity is improved, but alternating current resistance increases due to particle brittleness and poor adhesion
Solution Approach 1:
The patent applies composite materials by coating lithium transition metal compound particles with carbon materials to create a composite structure. This composite approach maintains the high energy storage capacity of the polyanion structure while the carbon coating layer improves electrical conductivity and reduces alternating current resistance, resolving the contradiction between energy storage capacity and reliability.
Solution Approach 2:
The patent controls the particle size of the active material particles within a specific range (10 μm to 50 μm) and adjusts the carbon content (0.1 wt% to 10 wt%) to optimize performance. By changing these parameters, the patent reduces alternating current resistance while maintaining energy storage capacity, addressing the reliability issue without sacrificing energy storage.
2Ease of manufacture
If active material particles are pressed during production process, then adhesion between substrate and active material layer is improved, but particle deformation increases leading to increased interface resistance
Solution Approach 1:
The patent uses a carbon coating layer as a flexible shell around the active material particles. This carbon shell maintains particle integrity during the pressing process, preventing deformation while allowing sufficient adhesion between the active material layer and substrate. The flexible carbon shell absorbs pressing stress, reducing interface resistance while maintaining manufacturability.
Solution Approach 2:
The carbon coating is applied beforehand to protect the brittle lithium transition metal compound particles during subsequent pressing operations. This prior cushioning prevents particle deformation and maintains low interface resistance while still allowing the pressing process to achieve adequate adhesion between layers.
3Reliability
If carbon material coating is applied to improve electron conductivity, then alternating current resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent combines the carbon coating step with the existing electrode manufacturing process, integrating multiple functions into a single workflow. The carbon coating is applied during the standard electrode production process, merging the conductivity enhancement step with the manufacturing process to minimize additional complexity while achieving reduced alternating current resistance.
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 improves adhesion between the substrate and the active material layer, thereby reducing alternating current resistance and enhancing initial power characteristics of the energy storage device.
Implementation Method 1
an amount of change in the particle size of 1.1 nm or less when pressurized from 20 mN to 100 mN
Implementation Method 2
coated with a first carbon material... and a second carbon material... capable of reducing the alternating current resistance
Data Source
AI summary
An electrode according to one aspect of the present invention is a granular material in which particles containing a lithium transition metal compound having a polyanion structure are coated with a first carbon material, and includes active material particles including an amount of change in the particle size of 1.1 nm or less when pressurized from 20 mN to 100 mN, and a second carbon material.