Carbonate Washing of Porous Cathode Precursors for Low-Impurity Oxides
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Solution Overview
Problem
Conventional methods for producing positive electrode active materials for lithium-ion secondary batteries result in high impurity levels, leading to reduced battery capacity, irreversible capacity, and safety concerns due to excess lithium and corrosive chlorine impurities, which also contaminate equipment during the firing process.
Innovation Solution
A method involving the washing of nickel-manganese composite hydroxide particles with an aqueous carbonate solution to reduce impurities, followed by a firing step to produce lithium-nickel-manganese composite oxide with a hollow or porous structure, achieving a lower sulfate and sodium content, thereby enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional production methods are used to produce positive electrode active materials, then the production process is simple, but the impurity content increases leading to reduced battery capacity and safety issues
Solution Approach 1:
The patent applies preliminary action by washing the nickel-manganese composite hydroxide particles with aqueous carbonate solution before the firing step. This pre-washing removes sulfate and sodium impurities from the precursor particles, so that when the material is subsequently fired to produce lithium-nickel-manganese composite oxide, the final product has reduced impurity content (sulfate ≤0.4% by mass, sodium ≤0.035% by mass) without requiring complex post-processing steps.
2Productivity
If conventional firing process is used, then the production efficiency is high, but chlorine impurities volatilize and contaminate equipment
Solution Approach 1:
The patent applies the extraction principle by removing chlorine-containing impurities from the nickel-manganese composite hydroxide particles through washing with aqueous carbonate solution before firing. This extracts harmful chlorine substances from the precursor material, preventing their volatilization during the subsequent high-temperature firing process, thereby protecting equipment from contamination while maintaining production efficiency.
3Reliability
If excess lithium is used to compensate for irreversible capacity, then the battery capacity is maintained, but safety concerns increase due to excess lithium
Solution Approach 1:
The patent applies preliminary action by removing sulfate and sodium impurities from the precursor particles through washing with aqueous carbonate solution before firing. This preliminary purification prevents these impurities from causing irreversible capacity loss during battery operation, eliminating the need to add excess lithium to compensate for such losses, thereby improving battery safety while maintaining reliable capacity.
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 approach results in a positive electrode active material with reduced impurities, improved capacity, coulomb efficiency, and reaction resistance, while minimizing equipment damage from chlorine volatilization, thus offering a more efficient and safer battery production process.
Implementation Method 1
washing nickel-manganese composite hydroxide particles... with an aqueous carbonate solution... to reduce impurities
Implementation Method 2
washing... with an aqueous carbonate solution having a carbonate concentration of 0.1 mol/L or more
Implementation Method 3
a firing step of firing the lithium mixture in an oxidizing atmosphere at 800 to 1100° C. to obtain lithium-nickel-manganese composite oxide
Implementation Method 4
firing the lithium mixture... to obtain lithium-nickel-manganese composite oxide
Implementation Method 5
firing the lithium mixture in an oxidizing atmosphere at 800 to 1100° C.
Data Source
AI summary
Provided is a precursor of a positive electrode active material containing, in a reduced amount, impurities which do not contribute to a charge/discharge reaction but rather corrode a firing furnace and peripheral equipment and thus having excellent battery characteristics and safety, and production method thereof.A method for producing a precursor of a positive electrode active material for nonaqueous electrolyte secondary batteries having a hollow structure or porous structure includes obtaining the precursor by washing nickel-manganese composite hydroxide particles having a particular composition ratio and a pore structure in which pores are present within the particles with an aqueous carbonate solution having a carbonate concentration of 0.1 mol/L or more.