Aqueous Cathode Slurry pH Control Without Active Material Dissolution
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Solution Overview
Problem
The use of inorganic acids as pH adjusters in lithium-ion battery positive electrode slurries is challenging due to their strong pH-lowering effect, which can lead to dissolution of the active material and difficulty in adjusting the pH to the desired level, while organic acids require high concentrations to achieve the desired pH, resulting in reduced battery performance.
Innovation Solution
A slurry for positive electrodes of lithium-ion batteries is formulated using covered particles with lithium composite oxide and a passivation film, water as the solvent, and an organic acid as the pH adjuster, which suppresses the reaction with water, prevents corrosion, and allows for easier pH adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If inorganic acid is used as pH adjuster, then pH value is lowered effectively, but active material dissolves and handling becomes difficult
Solution Approach 1:
The patent changes the chemical nature of the pH adjuster from inorganic acid to organic acid, fundamentally altering the chemical parameters of the system. This substitution maintains the pH-lowering function while eliminating the harmful dissolution effect on the active material, as organic acids do not cause the same type of chemical attack on lithium composite oxide particles.
Solution Approach 2:
The patent employs a milder, safer organic acid that can be easily handled and disposed of, replacing the dangerous inorganic acid. The organic acid serves its purpose of pH adjustment and can be removed or neutralized more easily, reducing environmental burden and improving safety without compromising the active material.
2Ease of operation
If organic acid is used as pH adjuster, then handling becomes easier and safety improves, but large amounts are required reducing battery performance
Solution Approach 1:
The patent optimizes the concentration parameter of the organic acid in the slurry formulation. By carefully controlling the amount of organic acid added and adjusting other slurry components accordingly, the patent achieves effective pH adjustment with minimal organic acid content, preventing excessive acid residue that would harm battery performance.
Solution Approach 2:
The patent applies the organic acid locally and selectively to adjust the pH of specific components of the slurry rather than using large excess amounts throughout the entire formulation. This targeted approach ensures sufficient pH control while minimizing the total quantity of organic acid present in the final electrode product.
3Object-affected harmful factors
If water is used as solvent, then environmental burden is reduced, but active material reacts with water causing corrosion
Solution Approach 1:
The patent introduces the organic acid as an intermediary substance that mediates between the aqueous solvent and the active material. The organic acid adjusts the pH environment to be less alkaline, thereby preventing the harmful reaction between water and the active material surface, which would otherwise lead to corrosion of the aluminum current collector.
Solution Approach 2:
The patent changes the pH parameter of the aqueous slurry by adding organic acid, transforming it from a strongly alkaline environment (harmful to active material) to a mildly acidic or neutral environment (safe for active material). This parameter change allows water to remain as solvent without causing corrosion, combining the environmental benefits of aqueous solvents with the protective effect of pH control.
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 proposed slurry composition reduces the environmental impact, enhances safety and handling, and achieves battery performance comparable to that of lithium-ion batteries with positive electrodes formed from organic solvent-based slurries.
Implementation Method 1
covered particles having lithium composite oxide particles and passivation film which covers at least a part of their surface
Implementation Method 2
the pH adjuster comprises an organic acid
Data Source
Figure 1
AI summary
[Summary] [Problem to be solved] To provide a slurry for positive electrodes of lithium-ion batteries, which has a low impact on the environment, is excellent in safety and ease of handling, and can provide a lithium-ion battery that exhibits battery performance equivalent to that of a lithium-ion battery with a positive electrode formed from an organic solvent-based slurry for electrodes. [Means for solution] A slurry for positive electrodes of lithium-ion batteries, comprising a positive electrode material, a binder, a solvent and a pH adjuster, wherein the positive electrode material comprises covered particles having lithium composite oxide particles and passivation film which covers at least a part of their surface, the solvent comprises water, the pH adjuster comprises an organic acid.