A battery technology that’s getting a lot of attention is solid-state batteries, lithium-ion batteries that replace the liquid electrolyte with a solid material.
To elaborate on why it’s still stuck at TRL 4/9: the barrier is manufacturing, not science. There are several types of solid electrolyte — the component that defines an all-solid-state battery — and each is a different trade-off between performance and cost.
The leading candidate, the sulfide type, has the highest conductivity, and Japan’s decades-deep players (Toyota, Idemitsu) are built around it. But it reacts with trace moisture to release H₂S, so it needs extremely strict dry-room control — a serious manufacturing-cost barrier, not a physics one.
The halide type is the development to watch. In July, Sumitomo Chemical announced it will mass-produce a halide electrolyte that — it says — matches sulfide conductivity while running on existing lithium-ion production lines. That prioritizes manufacturability over the spec sheet.
One issue I had hoped you might address is how the ions migrate through a solid electrolyte (as opposed to the liquid case where mobility of dissolved material is not a problem).
I'd never really registered that a gas car gets its oxidizer for free from the air while a battery has to carry its own. That framing explains the energy density gap better than any spec sheet: solid-state trims the scaffolding, but the cathode you have to haul around isn't going anywhere.
The 70 grams of scaffolding per gram of reacting lithium explains why the funding pattern looks the way it does. Removing the graphite intercalation structure is one of the few remaining changes that alters the ratio rather than trimming it, since most incremental gains since 2010 have come from shaving the supporting material rather than changing what it's supporting. That's a step change in the denominator, which is why $4 billion goes into something the leading manufacturer rates at 4 of 9 and won't commit to commercially.
But you don't need to have all your fuel in the engine when you run it, you have a fraction of a gram of petrol in the actual combustion chamber.
Flow batteries are the analogue of engines where the reactants are held in tanks, the issue is finding a reactant that will flow and have a high electrical potential. You can't just feed them liquid lithium so you are back to having a "structure" around the reactants.
Everyone is talking about solid state batteries as the successor of "liquid state" batteries. The matter has a third state - gas but nobody is talking about air/gas batteries !?
Your application of the virial theorem seems wrong. Batteries are presumably not in equilibrium when (dis)charging, and they're more than 50% efficient.
I've seen Indian software engineers in battery-adjacent fields over-invest in RSUs of solid-state battery startups, assuming commercialization will mirror the hype timeline.
CATL's 4/9 readiness suggests a 5-10 year horizon at least — long enough that relying on it for near-term retirement growth is risky.
The pattern: treat it as a speculative allocation, not a core holding. Run the numbers on a 10-year delay.
To elaborate on why it’s still stuck at TRL 4/9: the barrier is manufacturing, not science. There are several types of solid electrolyte — the component that defines an all-solid-state battery — and each is a different trade-off between performance and cost.
The leading candidate, the sulfide type, has the highest conductivity, and Japan’s decades-deep players (Toyota, Idemitsu) are built around it. But it reacts with trace moisture to release H₂S, so it needs extremely strict dry-room control — a serious manufacturing-cost barrier, not a physics one.
The halide type is the development to watch. In July, Sumitomo Chemical announced it will mass-produce a halide electrolyte that — it says — matches sulfide conductivity while running on existing lithium-ion production lines. That prioritizes manufacturability over the spec sheet.
One issue I had hoped you might address is how the ions migrate through a solid electrolyte (as opposed to the liquid case where mobility of dissolved material is not a problem).
I was curious too, but a brief overview is provided in footnote 2.
I'd never really registered that a gas car gets its oxidizer for free from the air while a battery has to carry its own. That framing explains the energy density gap better than any spec sheet: solid-state trims the scaffolding, but the cathode you have to haul around isn't going anywhere.
Battery races are a materials story. The scarce edge is deciding which upstream metals still compound when demos outrun supply.
https://paretoinvestor.substack.com/p/copper-crisis-2026-supply-shortage
would also be interesting to understand how SOC testing evolve with battery mfg innovation
The 70 grams of scaffolding per gram of reacting lithium explains why the funding pattern looks the way it does. Removing the graphite intercalation structure is one of the few remaining changes that alters the ratio rather than trimming it, since most incremental gains since 2010 have come from shaving the supporting material rather than changing what it's supporting. That's a step change in the denominator, which is why $4 billion goes into something the leading manufacturer rates at 4 of 9 and won't commit to commercially.
To be fair, you need a lot of scaffolding in a combustion engine also. You need at least a heavy combustion chamber and pistons.
But you don't need to have all your fuel in the engine when you run it, you have a fraction of a gram of petrol in the actual combustion chamber.
Flow batteries are the analogue of engines where the reactants are held in tanks, the issue is finding a reactant that will flow and have a high electrical potential. You can't just feed them liquid lithium so you are back to having a "structure" around the reactants.
This startup will be a fun read for you and the readers after this: https://www.gaussion.com/
They are addressing this dendrite formation issue. Thank you for article!
Everyone is talking about solid state batteries as the successor of "liquid state" batteries. The matter has a third state - gas but nobody is talking about air/gas batteries !?
Your application of the virial theorem seems wrong. Batteries are presumably not in equilibrium when (dis)charging, and they're more than 50% efficient.
I've seen Indian software engineers in battery-adjacent fields over-invest in RSUs of solid-state battery startups, assuming commercialization will mirror the hype timeline.
CATL's 4/9 readiness suggests a 5-10 year horizon at least — long enough that relying on it for near-term retirement growth is risky.
The pattern: treat it as a speculative allocation, not a core holding. Run the numbers on a 10-year delay.