Positive Electrode Pore Structure for Battery Wetting
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Solution Overview
Problem
Secondary batteries face challenges in achieving high energy density and efficient electrolyte wetting due to the low solubility and dispersibility of carbon nanotubes, leading to increased electrode resistance and reduced battery performance.
Innovation Solution
A positive electrode with a conductive material comprising bundle-type carbon nanotubes, optimized for improved dispersibility and pore structure, is developed, featuring a specific Raman spectroscopy ratio and packing density, enhancing electrolyte wetting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If high-pressure press is used to fabricate high-density electrodes, then electrode density is increased, but permeation of electrolyte into the electrode is decreased
Solution Approach 1:
The patent utilizes porous structures within the electrode active material particles themselves, rather than relying on inter-particle spaces. The porous interior of each particle provides channels for electrolyte penetration while the particle packing maintains high density, thus resolving the contradiction between density and permeation.
Solution Approach 2:
The patent implements a nested structure where porous interiors are contained within solid particle exteriors. The porous structure is nested inside each active material particle, allowing electrolyte access to the interior reaction sites while the outer shell maintains structural integrity and packing density.
2Reliability
If carbon nanotubes are used to reduce electrode resistance, then conductivity is improved, but dispersibility in solvent is poor leading to agglomeration
Solution Approach 1:
The patent introduces a dispersant as an intermediary substance that mediates between the carbon nanotubes and the solvent. The dispersant adsorbs onto the carbon nanotube surfaces, providing steric or electrostatic repulsion that prevents agglomeration while allowing uniform distribution throughout the electrode slurry.
Solution Approach 2:
The patent creates a composite system combining carbon nanotubes with dispersant molecules. This composite approach allows the carbon nanotubes to maintain their conductive properties while the dispersant coating improves their compatibility with the solvent and prevents aggregation during electrode fabrication.
3Ease of manufacture
If ultrasonic treatment is used to disperse carbon nanotubes, then dispersibility is maintained during treatment, but carbon nanotubes agglomerate after treatment when concentration increases
Solution Approach 1:
The patent applies preliminary action by adding the dispersant to the carbon nanotubes before ultrasonic treatment. This pre-coating of dispersant on the nanotube surfaces during mixing, followed by ultrasonic treatment, ensures that the nanotubes remain dispersed even at higher concentrations and over extended periods, preventing post-treatment agglomeration.
4Reliability
If high concentration of carbon nanotubes is dispersed in solvent, then conductivity is improved, but viscosity increases making handling difficult
Solution Approach 1:
The dispersant acts as a lubricating intermediary between carbon nanotubes, reducing inter-particle friction and preventing the formation of dense aggregates. This allows higher carbon nanotube concentrations to be achieved while maintaining manageable viscosity levels and good flow characteristics for electrode fabrication.
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 optimized positive electrode exhibits improved electrolyte wetting, reduced resistance, and enhanced battery performance by maintaining high packing density while maintaining large pore sizes for efficient electrolyte permeation.
Implementation Method 1
a conductive material is used in fabrication of an electrode, the conductive material is dispersed between compressed electrode active material particles, and thus micropores are maintained between the active material particles, resulting in facilitated permeation of an electrolyte, and resistance in the electrode may be reduced due to high conductivity of the conductive material
Implementation Method 2
the positive electrode active material layer has a packing density of 3.0 g/cc or more, and has an average pore diameter of 0.1 μm to 0.5 μm at the packing density when a pore size distribution is measured by mercury intrusion porosimetry
Data Source
AI summary
Provided herein are a positive electrode for a secondary battery and a secondary battery including the same. The positive electrode includes a positive electrode active material layer including a positive electrode active material, a conductive material, and a dispersant, wherein the conductive material includes bundle-type carbon nanotubes, units of which have an average strand diameter of 15 nm or less, and the positive electrode active material layer has a packing density of 3.0 g/cc or more, and has an average pore diameter of 0.1 μm to 0.5 μm at the packing density when a pore size distribution is measured by mercury intrusion porosimetry, and thus may exhibit excellent electrolyte wetting properties. As a result, when the positive electrode is applied to a battery, wetting time of the positive electrode is shortened, and an area of the positive electrode that is not filled with an electrolyte is reduced, resulting in enhanced battery performance.