Nickel Cathode Material Calcination With Low Residual Lithium
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Solution Overview
Problem
Nickel-based positive electrode active materials face challenges such as structural deterioration, surface side reactions, and high unreacted lithium content during heat treatment, leading to reduced capacity and increased processing costs due to the need for a washing process to remove excess lithium.
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 from nickel-based positive electrode active materials, then surface properties are improved and residual lithium content is reduced, but lithium is lost from inside the material and processing costs significantly increase
Solution Approach 1:
The patent applies preliminary action by adding excess lithium raw material before the heat treatment step. This ensures that during the heating process, there is sufficient lithium available to react with the nickel-based precursor, preventing the formation of unreacted lithium on the surface that would otherwise require washing. The lithium is pre-positioned in the mixture to react during heating, eliminating the need for subsequent washing operations.
Solution Approach 2:
The patent extracts the washing step from the conventional preparation process. By removing the washing operation entirely and replacing it with controlled heat treatment of the mixed raw materials, the method eliminates the harmful effect of lithium loss during washing while still achieving the desired surface properties and low residual lithium content through the thermal reaction process.
2Manufacturing precision
If a washing process is performed to remove unreacted lithium, then residual lithium content is reduced, but processing costs and device complexity significantly increase
Solution Approach 1:
The patent extracts the washing step from the conventional preparation process. By removing the washing operation entirely and replacing it with controlled heat treatment of the mixed raw materials, the method eliminates the harmful effect of lithium loss during washing while still achieving the desired surface properties and low residual lithium content through the thermal reaction process.
Solution Approach 2:
The patent applies parameter changes by modifying the heat treatment parameters (temperature range of 500-750°C, holding time of 1-12 hours) and the ratio of lithium raw material to nickel-based precursor. These parameter adjustments ensure that the heat treatment process itself is sufficient to react the materials and produce the desired product with low residual lithium, eliminating the need for additional washing steps and reducing processing complexity.
3Quantity of substance
If nickel-based positive electrode active materials are prepared with high nickel content to achieve high capacity, then energy density is improved, but unreacted lithium content increases during heat treatment requiring additional washing
Solution Approach 1:
The patent applies preliminary action by adding excess lithium raw material before the heat treatment step. This ensures that during the heating process, there is sufficient lithium available to react with the nickel-based precursor, preventing the formation of unreacted lithium on the surface that would otherwise require washing. The lithium is pre-positioned in the mixture to react during heating, eliminating the need for subsequent washing operations.
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 achieves high-capacity, long-lifecycle nickel-based positive electrode active materials with improved surface characteristics and high pellet density, while minimizing lithium loss and processing costs.
Implementation Method 1
performing a first heat treatment at a temperature range of 500 °C to 750 °C to prepare a first fired product, and performing a second heat treatment at a temperature range of 650 °C to 850 °C
Data Source
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AI summary
Disclosed are a method of preparing a positive electrode active material, a positive electrode active material prepared according to the method, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. The method includes (i) 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, and (ii) 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.