Nickel Cathode Active Material Calcination Without Lithium Washing
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Solution Overview
Problem
Existing nickel-based positive electrode active materials for rechargeable lithium batteries face challenges such as structural deterioration, surface reactions, particle cracks, and high unreacted lithium content, leading to reduced capacity and increased processing costs due to the need for a washing process to control surface properties.
Innovation Solution
A method involving two-stage heat treatment of a nickel-based precursor with controlled lithium raw material ratios, omitting the washing process, to produce secondary particles with uniform size and low residual lithium content, enhancing surface properties and reducing processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a washing process is performed to remove unreacted lithium and control surface properties, then surface properties are improved, but lithium is lost during washing which reduces capacity and increases processing costs
Solution Approach 1:
The patent applies preliminary action by controlling the lithium content in the precursor material before the main synthesis reaction. By carefully adjusting the lithium-to-metal ratio in the precursor and using a two-stage heat treatment process, the method prevents excessive unreacted lithium from forming in the first place, thereby eliminating the need for subsequent washing steps that would cause lithium loss.
Solution Approach 2:
The patent employs parameter changes by optimizing the lithium-to-metal ratio in the precursor material and adjusting the heat treatment temperatures in two stages. These parameter optimizations enable complete reaction of lithium without excess remaining, achieving good surface properties without requiring washing that would remove lithium.
2Manufacturing precision
If a washing process is performed to remove unreacted lithium, then surface properties are improved, but processing costs significantly increase
Solution Approach 1:
The patent eliminates the need for washing by taking preliminary action in the precursor preparation and heat treatment stages. By optimizing lithium content and using two-stage heat treatment, the process achieves complete reaction before synthesis, removing the requirement for costly washing and lithium compensation steps.
Solution Approach 2:
The patent extracts the washing step from the manufacturing process entirely. By redesigning the synthesis approach to prevent excess lithium formation through optimized precursor composition and two-stage heat treatment, the harmful or unnecessary washing operation is completely removed from the process flow.
3Quantity of substance
If higher nickel content is used to achieve high capacity, then capacity increases, but unreacted lithium content increases requiring additional washing
Solution Approach 1:
The patent uses parameter changes by optimizing the lithium-to-metal ratio in the precursor material specifically for high-nickel compositions. By adjusting this ratio and implementing two-stage heat treatment with controlled temperatures, the method ensures complete lithium reaction even in high-nickel materials, preventing excess unreacted lithium without requiring washing.
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 results in high-capacity, long-lifecycle nickel-based positive electrode active materials with improved surface characteristics and high pellet density, achieved through controlled lithium addition and heat treatment, without the need for a washing process.
Implementation Method 1
performing a first heat treatment at a temperature range of about 500° C. to about 750° C. to prepare a first fired product, mixing the first fired product and a second lithium raw material, and performing a second heat treatment at a temperature range of about 650° C. to about 850° C.
Implementation Method 2
performing a second heat treatment at a temperature range of about 650° C. to about 850° C. to prepare a positive electrode active material in the form of secondary particles including a lithium nickel-based composite oxide, the secondary particles being formed by agglomerating a plurality of primary particles
Data Source
AI summary
Disclosed are a method of preparing a positive electrode active material, a positive electrode active material prepared according to the method, and a rechargeable lithium battery including the positive electrode active material. The method includes mixing a nickel-based precursor and a first lithium raw material and performing a first heat treatment at about 500° C. to about 750° C. to prepare a first fired product, mixing the first fired product and a second lithium raw material and performing a second heat treatment at about 650° C. to about 850° C. to prepare a positive electrode active material in the form of secondary particles including a lithium nickel-based composite oxide, the secondary particles being formed by agglomerating a plurality of primary particles. A molar ratio (L1) of lithium in the first lithium raw material to a total metal of the nickel-based precursor is about 0.2 to about 0.9, a molar ratio (L2) of lithium in the second lithium raw material to a total metal excluding lithium in the first fired product is about 0.1 to about 0.8, and about 0.9≤L1+L2≤about 1.1.