Ternary Cathode Material: Single Crystalization
Ternary Cathode Material: Single Crystalization
Current Trends in Ternary Cathode Materials primarily include three major developments: Single crystallization, high voltageization, and high nickelization.
The development of single crystal materials is primarily aimed at improving battery cycle life, while high nickel and high voltage materials are focused on enhancing energy density.
◆ In the single crystal direction, prominent cathode material companies include Zhenhua New Materials.
◆ While in the high voltage direction, there are companies like Xawu New Energy and Changyuan Lithium Technology.
◆ For the high nickel direction, companies like CAP New Materials and Danshen Technology are notable representatives.
Various technological trends intersect like high-nickel single crystal materials, with companies like CAP New Materials leading the way.
1. Single Crystalization: Advantages
Cathode materials can be categorized as polycrystalline and single crystal.
Polycrystalline materials typically exist in the form of micrometer-scale aggregates. Within these aggregates, there are numerous grain boundaries.
During the charge-discharge processes in batteries, due to the anisotropic lattice changes, polycrystalline materials are prone to grain boundary cracking, resulting in the breakage of secondary particles.
This leads to a rapid increase in side reactions, impedance rise, and a rapid decrease in performance.
Using single crystal particles can reduce grain boundaries, decrease the occurrence of side reactions, and improve packing density, thus increasing energy density.
In comparison to polycrystalline materials, single crystal materials generally exhibit much better cyclic performance.
2. Monocrystallization: Production Process
The primary method for producing monocrystalline cathode materials involves high-temperature sintering.
The preparation methods can be categorized into three types: single-step high-temperature method, multi-step high-temperature method, and molten salt-assisted synthesis method. The molten salt-assisted synthesis method requires the introduction of molten salt and a subsequent washing process after sintering.
In comparison to the preparation of polycrystalline materials, the sintering temperature for monocrystalline materials is generally higher by 70-80 degrees.
During the sintering process, primary particles grow, and secondary particles also agglomerate. Therefore, post-sintering grinding is necessary.
3. Monocrystallization: Challenges
The transition from polycrystalline to monocrystalline cathodes also presents some challenges.
Processing: If sintering is incomplete, resulting in quasi-monocrystalline structures, it may not achieve the expected performance.
Additionally, monocrystalline particles exhibit reversible slip during charge and discharge processes. The grain size typically should not exceed 3.5 micrometers, and excessive sintering should be avoided.
Lithium-Nickel Cointegration: The preparation of monocrystals requires higher sintering temperatures, but elevated temperatures can lead to the co-integration of lithium and nickel.
Rate Performance: Due to the high lithium-ion diffusion coefficient in polycrystalline systems, the use of monocrystals often sacrifices rate performance.
During the transition of cathode materials from polycrystalline to monocrystalline, it is necessary to fully consider the overall performance of the cathode material.
In practical applications, monocrystalline materials are sometimes blended with polycrystalline materials.
