Hydrophobic Carbon Coating for Battery Electrode Paste Stability
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Solution Overview
Problem
Existing methods for producing positive electrode active materials for nonaqueous electrolyte secondary batteries face challenges such as lithium ion elution, decomposition, and gelation due to water contact, leading to non-uniform layers and reduced battery performance.
Innovation Solution
A method involving a coating layer formed by mixing fine carbon particles, an organic dispersant, a hydrophobic coat forming agent, and an organic solvent with the positive electrode active material, followed by drying and heat treatment, to enhance water resistance and conductivity while preventing gelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an aqueous medium is used as a solvent to prepare the positive electrode mixture material paste, then the paste can be easily prepared and applied, but lithium ions are eluted from the active material particles into the solvent due to water, causing the paste to become strongly alkalized and leading to decomposition or gelation of the binder and aggregation of the active material
Solution Approach 1:
A coating layer comprising fine carbon particles and a hydrophobic coat forming agent is formed on the surface of the positive electrode active material particles. This coating layer acts as an intermediary barrier that prevents direct contact between water in the aqueous solvent and the active material particles, thereby suppressing lithium ion elution and preventing paste alkalization while still allowing the use of aqueous media for paste preparation
Solution Approach 2:
The surface properties of the active material particles are modified by coating them with a hydrophobic substance. This changes the surface energy and wettability parameters of the particles, making them resistant to water contact and preventing the harmful interactions that occur when aqueous solvents directly contact the active material
2Reliability
If an organic solvent is used as a solvent to prepare the positive electrode mixture material paste, then lithium ion elution is suppressed, but the binder may still decompose or gel due to trace amounts of water contained in the solvent
Solution Approach 1:
The coating layer of fine carbon particles and hydrophobic coat forming agent is formed beforehand on the active material particles to provide a protective cushion against water contact. This pre-established protection prevents trace water in organic solvents from causing binder decomposition or gelation, ensuring paste stability throughout the manufacturing process
3Reliability
If the positive electrode active material particles are coated with a thick coating layer to improve water resistance, then lithium ion elution is suppressed, but the conductivity and battery performance may be reduced
Solution Approach 1:
A thin coating layer comprising fine carbon particles and hydrophobic coat forming agent is formed on the active material particles. This thin film provides sufficient water resistance to prevent lithium ion elution while maintaining electrical conductivity, as the coating is thin enough to not significantly impede electron transport
Solution Approach 2:
The coating layer is formed as a composite structure combining fine carbon particles (which provide electrical conductivity) and a hydrophobic coat forming agent (which provides water resistance). This composite approach allows both functions to be achieved simultaneously in a single thin layer
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 method improves water resistance and suppresses gelation of the positive electrode mixture material paste, maintaining battery performance and allowing for easier industrial-scale production with reduced surface damage to the active material particles.
Implementation Method 1
a coating layer which comprises fine carbon particles and a hydrophobic coat forming agent
Implementation Method 2
drying the mixture to obtain the mixture containing the organic solvent in a reduced amount
Implementation Method 3
heat-treating the mixture containing the organic solvent in a reduced amount
Data Source
AI summary
A method produces a positive electrode active material that does not impair the original battery characteristics of the positive electrode active material. The method can improves water resistance, and suppress the gelation of a positive electrode mixture material paste. The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries can include a mixing step of preparing a mixture including fine carbon particles, an organic dispersant, a hydrophobic coat forming agent, an organic solvent, and positive electrode active material particles, a drying step of drying the mixture to obtain the mixture containing the organic solvent in a reduced amount, and a heat treatment step of heat-treating the mixture containing the organic solvent in the reduced amount to obtain a coated positive electrode active material.