Lithium batteries’ big unanswered question – BBC Future https://www.bbc.com/future/article/20220105-lithium-batteries-big-unanswered-question?at_custom4=6DFDCB4E-6FB8-11EC-AF2D-4DD5923C408C&at_medium=custom7&at_custom2=facebook_page&at_custom3=BBC+News&at_campaign=64&at_custom1=%5Bpost+type%5D