“By the end of 2021, 55% of our ATL Delta Cargo facility will be powered by Flux Power lithium-ion Toyota forklifts. With these maintenance free batteries and Toyota's T360 support program, we have significantly reduced our operating costs and increased uptime.”
According to this statement, they appear to have a few years headstart.
https://www.fluxpower.com/application/airport-gse
https://www.fluxpower.com/hs-search-results?q=GSE+&type=SITE_PAGE&type=BLOG_POST&type=LISTING_PAGE