Lithium Manganese Coated Electrode Fluorine Hydrophobicity
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Solution Overview
Problem
The manufacturing of lithium manganese complex oxide particles for lithium ion secondary batteries results in increased reaction resistance due to the exchange reaction between lithium ions and protons, leading to a decrease in manganese valence and subsequent impedance issues during the drying process when using aqueous solvents.
Innovation Solution
Coating the lithium manganese complex oxide particles with a lithium ion-conductive oxide and introducing fluorine to create a hydrophobic layer, which suppresses the exchange reaction and maintains optimal manganese valence, using a specific thickness and fluorine-to-manganese ratio to balance conductivity and hydrophobicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aqueous solvents are used to prepare the paste, then environmental load is reduced and manufacturing costs are lowered, but reaction resistance increases due to exchange reaction between lithium ions and protons
Solution Approach 1:
A coating layer comprising a lithium ion-conductive oxide is formed on the surface of the LiMn complex oxide particles to act as an intermediary barrier. This coating prevents direct contact between water and the particle surfaces, thereby suppressing the exchange reaction between lithium ions and protons while maintaining lithium ion conductivity for battery operation
Solution Approach 2:
Fluorine is introduced into the LiMn complex oxide particles to change the surface properties and make them hydrophobic. This parameter change in surface chemistry reduces the affinity between water and the particle surfaces, thereby suppressing the exchange reaction while maintaining the desired electrochemical performance
2Reliability
If coating thickness is increased to suppress water contact, then reaction resistance decreases, but lithium ion conductivity may be reduced
Solution Approach 1:
The coating thickness is precisely controlled within the range of 5 nm to 10 nm. This optimized parameter allows the coating to provide sufficient barrier function against water while maintaining adequate lithium ion conductivity for efficient battery operation
Solution Approach 2:
The coating layer is composed of lithium ion-conductive oxide materials that possess both barrier properties against water and high lithium ion conductivity. This composite structure enables the coating to simultaneously provide protection against exchange reactions while facilitating lithium ion transport
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 effectively reduces reaction resistance by minimizing the contact between water and lithium manganese complex oxide particles, maintaining low impedance and enhancing the performance of the positive electrode in lithium ion secondary batteries.
Implementation Method 1
an exchange reaction between lithium ions (Li+) and protons (H+) is caused on the surfaces of the LiMn complex oxide particles
Implementation Method 2
introducing fluorine into at least a part of the coated particles... the fluorine-introduced portions become hydrophobic
Implementation Method 3
H+ is adsorbed onto the surfaces of the LiMn complex oxide particles
Data Source
AI summary
A method for manufacturing a positive electrode for a lithium ion secondary battery includes preparing lithium manganese complex oxide particles, preparing coated particles by forming a coating including a Li+-conductive oxide on a surface of each lithium manganese complex oxide particle, introducing fluorine into at least a part of the coated particles, preparing a fluid composition by mixing the coated particles at least a part of which fluorine is introduced into, a conductive material, an aqueous binder, and an aqueous solvent, forming a positive electrode mixture layer by disposing the fluid composition on a surface of a collector, and drying the positive electrode mixture layer. The thickness of the coating is 5 nm or more and 10 nm or less. Fluorine is introduced such that the ratio of fluorine to manganese in terms of the number of atoms in the coated particles reaches 1.95 or more and 3.1 or less.