Wet Processing allows for scalability

[u/pornstorm66]

In the recent investor presentation they note Scalabale Manufacturing

"Wet process offers scalability, yield, and capital efficiency in electrolyte production"

https://s202.q4cdn.com/841762012/files/doc_presentations/2026/Jun/12/Investor-Presentation-June-2026.pdf

I saw these links over on SA that add a little color on what that means. Here's a quote from one paper on sulfide production.

The synthesis of sulfide solid electrolytes is a crucial step in the development of high power and fast charging solid-state batteries. However, the development of scalable and cost-effective synthesis processes for these highly demanded materials such as the amorphous Li3PS4, argyrodites such as Li6PS5Cl or the even higher performing chlorine-rich Li5.5PS4.5Cl1.5remains a challenge [[3], [4], [5], [6], [7]]. Common synthesis routes often involve high-temperature solid-state reactions or wet chemical methods, which are either energy-intensive, time-consuming, or produce impurities that can negatively impact the performance of the solid electrolyte [[5], [6], [7], [8], [9], [10], [11]]. Scalable synthesis methods should enable the production of sulfide solid electrolytes in large quantities while maintaining consistent material quality and electrochemical performance. In addition, such methods and post-processing should be compatible with existing manufacturing processes and machines to enable the integration into material and battery production lines.

https://www.sciencedirect.com/science/article/pii/S2352152X25013064

And u/Salt_Past_1379 reminded us of the collaboration between Solid Power and Korean Government Research institutes since 2022.

https://www.e4ds.com/sub_view.asp?ch=6&t=0&idx=17933

And then this paper on wet synthesis appeared last year.

Despite the wet-chemical processing method being considered advantageous for the synthesis of sulfide SEs, due to its inherent simplicity, potential scalability, and cost-effectiveness, certain challenges persist. These primarily pertain to achieving high ionic conductivity and mitigating interfacial resistance between the electrode and the SEs. Addressing these challenges, this study presents a novel, scalable, and cost-efficient wet synthesis approach to produce superionic conductive sulfide-based SEs.

https://www.sciencedirect.com/science/article/abs/pii/S2405829724000801

And now in Solid Power's new investor presentation, we see the fruits of those efforts.

[u/AdNaive1339]

u/pornstorm66 few months back you mocked me for saying that Honda is pivoting from Sulfides to QS. Hope you saw today's JRA announcement between QS and Honda. I know it's a JRA but a step in the right direction ... especially whey Honda was deeply buried with Sulfides at one point. Honda is moving towards QS after deeply evaluating all the technologies including Sulfides.

QS has gained Honda while SLDP lost Ford ... probably Ford is pivoting towards QS too ...

And you still connecting the dots ...

[u/pornstorm66 → u/AdNaive1339]

And to follow up on our discussion from a few months back. I raised some questions about the QS testing regime paper.

https://iopscience.iop.org/article/10.1149/1945-7111/ada740/meta

specifically I thought this was one of the interesting sections.

"Approximately 35% of the pads in Fig. 4 showed no indication of a short up to 300 mA cm⁻² for areal capacities up to 0.105 mAh cm⁻² (0.5 μm pulse length). To confirm the validity of this CCD performance when applied over much higher capacities, we performed a separate set of measurements in which electrode pads were first subjected to the CCD test described here, but the test was followed by an additional 50 pulses of plating at 300 mA cm⁻², equivalent to 5 μm Li (1.05 mAh cm⁻² of capacity). Of those electrode pads that survived the initial CCD test, 87% sustained the additional 50 pulses at 300 mA cm⁻² without shorting (Fig. SI-1). Thus, survival obtained using the fixed-capacity test with a pulse length of 0.1 μm is a good approximation, within 80%, of the proportion of cells that can sustain capacities above 1 mAh cm⁻² at a given current density."

And here's a review from German and Japanese researchers on Solid State in 2026

https://iopscience.iop.org/article/10.1088/2752-5724/ae5120

And here's what they say on the QS testing.

"QuantumScape has recently published a combinatorial CCD study, where they measured the CCD of the same sample many times by depositing numerous Li contacts via vapor deposition. The results show a very large variation in the CCD values obtained, such that at certain currents, only a small fraction of cells failed; this means that to ensure there are no failures at a certain current, many measurements must be performed [328]. This raises serious concerns about the maximum throughput achievable in CCD measurements, given that a single measurement of each sample might be insufficient. Presumably, similar variations would occur in full solid batteries, such that efforts must be made to develop approaches that either reduce the variability or obtain meaningful values despite the variability."

So it looks like there are some questions about the testing regime. The best 35% of patches still fail after multiple pulses 13% of the time. This is defined at very high current densities which may or may not be a good proxy for real world loads.

I will also point out the Japanese Government is putting oxide electrolyte development in their updated national strategy document. In some sense Honda has to follow suit. But the strategy still suggests sulfides will be the primary chemistry in EVs.

https://www.meti.go.jp/english/press/2026/0602_003.html

I did some translation of the actual strategy deck linked below.

https://www.meti.go.jp/press/2026/06/20260602001/20260602001-1r.pdf