The ESS battery uses Iron and Salt.
https://www.patreon.com/posts/exclusive-early-90305492?utm_medium=post_notification_email&utm_campaign=patron_engagement&utm_source=post_link&token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJyZWRpc19rZXkiOiJpYToyMjAxYWQzZi1iYTQ1LTQyZGItODAyOC1iMGVkZjU0MTJjY2UiLCJwb3N0X2lkIjo5MDMwNTQ5MiwicGF0cm9uX2lkIjo1NDQxODEzNX0.93GUyndIekBTnmm8fV2_PtnVexoX9zyP3bgjrB7PLV8
Dave’s JHAT on RFBs :