Bimodal Cathode Precursor Preparation for Higher Packing Density
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Solution Overview
Problem
Existing methods for preparing positive electrode active materials for lithium secondary batteries face challenges in achieving high packing density per unit volume while maintaining thermal stability and reducing preparation costs and time, particularly when mixing precursors of different diameters.
Innovation Solution
A method is developed to prepare a bimodal-type positive electrode active material precursor in a single reactor by controlling pH conditions during co-precipitation reactions, resulting in particles with different average diameters and compositions, which are then mixed with a lithium raw material and fired to enhance firing uniformity and packing density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If separate preparation and mixing of small-diameter and large-diameter precursors is performed, then packing density per unit volume is improved, but preparation costs and preparation time are increased
Solution Approach 1:
The patent combines the preparation of small-diameter and large-diameter precursors into a single reactor by controlling pH conditions during co-precipitation. The process uses a single reactor to produce both precursor types simultaneously, eliminating the need for separate preparation and mixing operations, thereby reducing preparation time and costs while achieving high packing density
Solution Approach 2:
The patent employs parameter changes by adjusting pH conditions to control particle size distribution. By maintaining pH within specific ranges (pH 9-11 for small-diameter, pH 7-9 for large-diameter precursors), the process generates a bimodal particle size distribution in a single reactor, achieving high packing density without separate preparation steps
2Quantity of substance
If high nickel content is used to increase capacity, then reversible capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating precursors with different compositions tailored to different size ranges. Small-diameter precursors contain high nickel content (70-90 mol%) for high capacity, while large-diameter precursors have lower nickel content (30-70 mol%) for better thermal stability. This composition gradient optimizes both capacity and safety
Solution Approach 2:
The patent creates a composite precursor system combining different nickel-containing compounds (such as Ni(OH)2, NiCO3, NiO) in specific ratios. This composite approach allows tuning of both capacity and thermal stability by adjusting the composition and size distribution of the precursor particles
3Reliability
If lithium-nickel-cobalt metal oxide is used to improve thermal stability, then thermal stability is improved, but capacity is reduced
Solution Approach 1:
The patent segments the precursor population into distinct size ranges (small-diameter: 3-8 μm, large-diameter: 8-15 μm) with different compositions. This segmentation allows the final product to achieve both high capacity (from high-nickel small particles) and good thermal stability (from lower-nickel large particles) simultaneously
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 improves productivity and packing density per unit volume, enhances firing uniformity, and maintains high-capacity properties by compensating for differences in particle size and composition, thus addressing the limitations of existing methods.
Implementation Method 1
subjecting the mixture to a co-precipitation reaction under a primary pH condition to form nuclei of first positive electrode active material precursor particles
Data Source
AI summary
A method for preparing a bimodal-type positive electrode active material precursor is provided. The method is capable of not only increasing productivity by preparing positive electrode active material precursors having small diameters and large diameters in a single reactor but also improving packing density per unit volume, a positive electrode active material precursor prepared by the preparation method and having improved packing density, and a positive electrode for a secondary battery and a lithium secondary battery including the same.