Title: Recently there was a thread about a &quot;breakthrough&quot; in battery technology at Toyota.<p><a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=36585327">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=36585327</a><p>Toyota has been putting out PR puff pieces about their &quot;solid-state&quot; (solid-electrolyte) batteries for years, but this story was unique in that it had a quote from Keiji Kaita, who holds some high-level role at Toyota. Anyway, I didn&#x27;t think much of it, because there was no paper referenced in the <i>Guardian</i> article, which seemed to be the original source.<p>But while reading about something else, I came across the paper &quot;A near dimensionally invariable high-capacity positive electrode material&quot;, published in <i>Nature Materials</i> last December:<p><a href="https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;s41563-022-01421-z" rel="nofollow noreferrer">https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;s41563-022-01421-z</a><p>This paper, reporting a cathode that has very little (much less than normal) change in size or shape when charged and discharged, claims reversible storage with a solid electrolyte. It stands to reason that dimensional stability of the cathode is necessary for interfacing with a solid electrolyte, since if it swells and shrinks, it will probably detach from the electrolyte, and possibly damage it further.<p>Looking at the affiliations of some of the authors we see a number of contributors from the &quot;Lithium Ion Battery Technology and Evaluation Center (LIBTEC)&quot;. A web search about LIBTEC leads to several articles from 2018:<p><a href="https:&#x2F;&#x2F;www.cnet.com&#x2F;roadshow&#x2F;news&#x2F;toyota-nissan-honda-libtec-solid-state-battery-development&#x2F;" rel="nofollow noreferrer">https:&#x2F;&#x2F;www.cnet.com&#x2F;roadshow&#x2F;news&#x2F;toyota-nissan-honda-libte...</a><p>which state that Toyota, along with Nissan, Honda and Panasonic (Tesla&#x27;s major collaborator), have established this consortium to work on solid-electrolyte batteries as of five years ago.<p>So what does this thing look like? It&#x27;s a vanadium–titanium cathode, Li8Ti2V4O14. Titanium is common; vanadium technically has a higher crustal abundance than nickel, but it tends to be spread across low-quality deposits, so production is low right now. A review considering the resource outlook for V-based batteries [1] was guardedly optimistic. 750 Wh&#x2F;kg is <i>great</i>. Vanadium cathodes historically had a problem with high dimensional <i>instability</i>, but it appears that cocrystallization with titanium may have fixed that, and the weird properties of vanadium became an advantage in compensating for Li+ influx&#x2F;efflux.<p>The use of a sulfide electrolyte pours doubt on claims of safety, though. It&#x27;s reasonably likely that if water were to come into contact with the electrolyte, it could release highly toxic hydrogen sulfide gas.<p>Also, since the battery was developed in collaboration with other major automakers (and funded by the Japanese government), it&#x27;s somewhat questionable to think it would give Toyota a major advantage in the EV race. But for the Japanese economy, which has been rather slow lately, it could be a boost.<p>1: <a href="https:&#x2F;&#x2F;chemistry-europe.onlinelibrary.wiley.com&#x2F;doi&#x2F;abs&#x2F;10.1002&#x2F;cssc.202200479" rel="nofollow noreferrer">https:&#x2F;&#x2F;chemistry-europe.onlinelibrary.wiley.com&#x2F;doi&#x2F;abs&#x2F;10....</a>
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