I am trying to dissolve CMC-SBR in water at 80C. First, I start with dissolving CMC in water, stirring at 80C, and after CMC is dissolved I added SBR, but SBR ends up as white gel-like structures. Didnt, dissolve even after stirring overnight at 80C. I have taken the ratio of CMC: SBR as 1:1 (wt%). To be more precise, I took 0.1g + 0.1g (CMC+ SBR) and added 10 ml water.
Edit: I have an additional 5 ml of ethanol into 10 ml solution and it converted into a uniform white solution.
I have taken the ratio of CMC: SBR as 1:1 (wt%). To be more precise, I took 0.1g + 0.1g (CMC+ SBR) and added 10 ml water. I have been taken excess water since it didn't dissolve in 5ml.
Is the SBR you're adding in powder form? The SBR I use (MTI) is suspended in water, and even then, it would never dissolve into a CMC solution the way you describe. If someone has given you the protocol you're using, I would suggest they have skipped a few details. I always add the SBR after all other slurry components, and it will start to separate immediately after mixing.
Anne Sawhney Thanks for answering.
Yes, I am using the powdered form of CMC and SBR is in liquid form. Almost all the publications mention dissolving both CMC and SBR. As you mentioned, I am sure the exact sequence of the addition of components and finer details might not be mentioned in publications.
I have added ethanol (1:2, ethanol: water) with water, and obtained a consistent white solution. Still, I am wondering whether ethanol impacts the performance of the binder.
Hi Pranay, the references you're following must be very different than mine. To predict dissolution behaviour of (non-powder) SBR into a (powder) CMC-based slurry, I would especially recommend Article Effects of the mixing sequence on the graphite dispersion an...
andArticle Effect of carboxymethyl cellulose on the flow behavior of li...
, which specifically studied the interaction of these two.Although I have read at least one paper where ethanol was used (to dissolve a cathode active material), I found that CMC does not dissolve in ethanol, so it would complicate optimisation.
Hi Anne Sawhney, thanks for the references. There is no problem with CMC, which dissolves by stirring at 60-80C in water. The problem is with the addition of SBR. SBR being a vicious rubbery-like liquid, doesn't dissolve in water, but instead forms gel-like structures. I have found that adding ethanol seems to form a uniform solution.
If I add SBR at the end, as you said, it gets separated and doesn't form good electrodes, with visibly inconsistent coating.
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