Hello,
For my current research project I need LiNiMnCoO2 particles with secondary particle size below 1um, ideally below 200 nm. All of the commercial powders have secondary particle sizes well above that limit. And also, all the papers claiming "NMC nanoparticles" have huge secondary particles with the primary particles being on the order of 100s of nm... Most commonly used method is sol-gel, but that yields a powder with rather large secondary particle size. Can you recommend any approaches that would result in actual fine powder with separate,
Unfortunately what you ask for in a powder is contrary to the laws of physics....
Solid-solid diffusion and van der Waals attraction means that primary particles < 100 nm or higher in size will form a mass of sub- and post-micron particles. In order to preserve the nano size (< 100 nm ) then the material must be retained in colloidal suspension or in atomized form. Take a look at:
(Open in IE only) Dispersion and nanotechnology http://tinyurl.com/hpywsge
Adhesion and cohesion http://tinyurl.com/zwb2wlh
Also Google 'comminution limit'...
Thank you for your answer,
I actually would rather to preserve the 100s of nm primary particles structure, that's perfectly fine. The only thing I care about is the final, total size of particles overall (secondary ones). I would like that size to be below 1 um. And it definitely doesn't defy laws of physics, as I observe such particles in the commercially available powders as well. They are just a minor fraction of the total size distribution. Maybe the better way to phrase this question would be: how to change the synthesis method to make formation of smaller secondary particles preferential.
Milling brings the risk of making the surface amorphous, which would change the Li conductivity a lot.
milling might be suitable for a large fraction of particles around and below 1 µm. I doubt that most around 200 nm and below can be achieved without large efforts. Further, I wonder wether you need the secondary particles submicron, I would have assumed that the primary particle size determines conductivity to a large extent?
I agree with Alan F Rawle regarding the particles around 100 nm.
However, for the particles of few 100s nm primary size, it is important to control the drying and the calcination processes in terms of:
1- Using temperatures as low as possible.
2- Reducing the time duration of the process as much as possible.
Please note that the thermal analysis (TGA and DSC) are required to decide the suitable conditions of these processes.
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