There are plenty of alternatives for lithium batteries, chiefly sodium and a redox flow. Heating/cooling is good as well to store, but not every structure is energy efficient enough that it would make much sense. Good thing to work towards, but grid batteries would probably be faster and easier to implement. I have reservations towards pumped hydropower, in part due to watching how hard it is to decommission a lot of hydroelectric dams these days in US as well as the cost to create the areas to hold the water (a lot of the areas that are geographically advantageous for pumped hydropower tend to be nature reserves or national parks, soo…).