Iron-air batteries (1,200 Wh/kg), and in general metal-air [1], might bring a surprise after 2024: December 2022, "Form Energy will site first American iron-air battery manufacturing plant in Weirton, West Virginia" [2].
[1] 2017, Yanguang Li, Jun Lu, Metal–Air Batteries: Will They Be the Future Electrochemical Energy Storage Device of Choice?https://pubs.acs.org/doi/10.1021/acsenergylett.7b00119 Betteridge's law of headlines answers "no", but good overview.
The various "-air" batteries tend to have major downsides...
They tend to get heavier as they discharge. They usually aren't rechargeable (or if they are, only a few times or with much lower energy densities). They tend to self-discharge within a few weeks of non-use.
Yes, there are downsides, as always in engineering, it's a matter of managing the compromises for the current implementation and researching better solutions for the next iteration.
[1] 2017, Yanguang Li, Jun Lu, Metal–Air Batteries: Will They Be the Future Electrochemical Energy Storage Device of Choice? https://pubs.acs.org/doi/10.1021/acsenergylett.7b00119 Betteridge's law of headlines answers "no", but good overview.
[2] https://formenergy.com/west-virginia-governor-jim-justice-an...