system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a solid state battery and why/how is it superior to lithium ion?

I keep seeing a lot of information about “breakthroughs” in solid state batteries for electric cars. People seem really excited about it and companies seem to be working hard to perfect it. 

But I’m struggling to understand why they’re superior and what makes a solid state battery such a “breakthrough” technology. Hoping someone can explain to someone who really doesn’t understand this stuff.
gpt
The majority of other battery types have some sort of liquid or gel inside them, which a solid state battery does not. How they work isn't all that different or important, but the major takeaway is that they can hold more charge than other batteries. So you either get more KWh for the same weight. 

Thats important for EVs because those battery packs weigh a ton (sometimes literally) so being able to pack in the same charge with less weight is ideal.