Ni-Co-Mn Layered Cathode Composition for Cycle Life and Capacity
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Solution Overview
Problem
Lithium secondary batteries using conventional lithium-containing composite metal oxides as positive electrode active materials fail to ensure sufficient performance in applications requiring high charge/discharge cycle performance and high discharge capacity, particularly in automotive applications.
Innovation Solution
A positive electrode active material with a layered crystal structure, specifically Li a Ni 1-x-y-z Mn x Co y M z O 2, where 0.9 ≤ a ≤ 1.2, 0 < x < 0.4, 0 < y < 0.4, 0 ≤ z < 0.1, and M is at least one metal from Mg, Al, or Zr, with optimized particle size, crystallite size, BET specific surface area, and lithium carbonate content, enhancing cycle performance and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium-containing composite metal oxide is used as positive electrode active material, then the battery structure is simple and easy to manufacture, but the charge/discharge cycle performance and discharge capacity are insufficient
Solution Approach 1:
The patent uses a composite material approach by combining multiple metal elements (Ni, Co, Mn, and additional M element) in a layered crystal structure Li a Ni 1-x-y-z Co x Mn y M z O 2. This composite composition improves charge/discharge cycle performance and discharge capacity while maintaining a manageable material structure through systematic control of stoichiometric ratios and crystal phase arrangement.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the stoichiometric ratios (a, x, y, z) of metal elements in the composite oxide, the crystallite size (600-1,400 Å), and the BET specific surface area (0.1-2.0 m²/g). These parameter optimizations enable high cycle performance and discharge capacity without excessive material complexity.
2Productivity
If conventional lithium-containing composite metal oxide is used, then the manufacturing process is simple, but the discharge capacity is insufficient for high-performance applications
Solution Approach 1:
The patent achieves high discharge capacity (140 mAh/g or more) by optimizing specific parameters: the lithium content (a=0.9-1.2), metal ratios (x, y, z), crystallite size (600-1,400 Å), and BET specific surface area (0.1-2.0 m²/g). These precise parameter controls enhance productivity in terms of discharge capacity while requiring controlled manufacturing processes.
Solution Approach 2:
The patent applies local quality by creating a layered crystal structure with specific regions having different compositions and properties. The layered structure provides localized pathways for lithium ion diffusion and electron transport, enhancing discharge capacity through optimized local electrochemical environments within the material.
3Productivity
If the crystallite size is increased to improve electrochemical performance, then the discharge capacity improves, but the specific surface area decreases
Solution Approach 1:
The patent optimizes the balance between crystallite size and specific surface area by controlling crystallite size within 600-1,400 Å and BET specific surface area within 0.1-2.0 m²/g. This parameter optimization achieves high discharge capacity (140 mAh/g or more) while maintaining sufficient surface area for electrochemical reactions, resolving the trade-off between these two parameters.
Data Source
Figure 1A~1B
AI summary
The object of the present invention is to provide a positive electrode active material usable for a lithium ion battery capable of high charge/discharge cycle performance and high discharge capacity. The positive electrode active material for a lithium secondary battery has a layered structure and comprises at least nickel, cobalt and manganese. Further, the positive electrode active material satisfies requirements (1) to (3) below: (1) a primary particle size of 0.1 µm to 1µm, and a 50 % cumulative particle size D50 of 1 µm to 10 µm, (2) a ratio (D90/D10) of volume-based 90% cumulative particle size D90 to volume-based 10% cumulative particle size D10 of 2 to 6, and (3) a lithium carbonate content in a residual alkali on particle surfaces of 0.1 % by mass to 0.8 % by mass as measured by neutralization titration.