Another chemistry that is potentially interesting is:
FeCl₂ + 2NaOH → Fe(OH)₂ + 2NaCl
Turning FeCl₂ into Fe(OH)₂ yields 51wh/mole, while turning NaOH into NaCl yields about 2wh/mol, and importantly we're not requiring H2O to participate.
A challenge with this chemistry is in the Fe(OH)₂ will turn into Fe(OH)₃ when exposed to air. But one could still de-water it in nitrogen, or just keep it under water.
Interestingly, FeCl₂, NaOH, Fe(OH)₂, and NaCl can all be reasonably precipitated out of the water as solids. If we push the reaction until they precipitate, we don't necessarily need to worry about concentrations in water.
Solid concentrations are:
NaCl -> 37mol/liter
NaOH -> 53mol/liter
Fe(OH)₂ -> 40mol/liter
FeCl₂ -> 12mol/liter (approx)
So if we're storing solids then:
1 liter of FeCl₂ requires 0.45 liter of NaOH and makes 0.3 liters of Fe(OH)₂ and 0.64 liters of NaCl, and this stores about 630wh of energy.
If we want to store everything as a sludge in 25% water, we keep all of the numbers the same but reduce the energy storage by 1/4.
Conservatively, we might think about storing 0.5kwh per 3 liters of tanks. So similarly to the other reactions, we're in the same ball park of 3 cubic meters of materials storing 100kWh.
But these materials are quite a bit safer. Note: There are no papers I could find on this exact reaction, so there might be something fatally flawed with it that I'm not thinking of...
Caleb James DeLisle
npub105…t88up
2026-10-05 11:16:44 UTC
in reply to nevent1q…3x87
Author Public Key
npub10502c8jv0y27jwcwxcq9kd3ph2wg7pt8ycexf5w2fyzythe97w2s7t88upPublished at
2026-10-05 11:16:44 UTCEvent JSON
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"content": "Another chemistry that is potentially interesting is:\n\nFeCl₂ + 2NaOH → Fe(OH)₂ + 2NaCl\n\nTurning FeCl₂ into Fe(OH)₂ yields 51wh/mole, while turning NaOH into NaCl yields about 2wh/mol, and importantly we're not requiring H2O to participate.\n\nA challenge with this chemistry is in the Fe(OH)₂ will turn into Fe(OH)₃ when exposed to air. But one could still de-water it in nitrogen, or just keep it under water.\n\nInterestingly, FeCl₂, NaOH, Fe(OH)₂, and NaCl can all be reasonably precipitated out of the water as solids. If we push the reaction until they precipitate, we don't necessarily need to worry about concentrations in water.\n\nSolid concentrations are:\nNaCl -\u003e 37mol/liter\nNaOH -\u003e 53mol/liter\nFe(OH)₂ -\u003e 40mol/liter\nFeCl₂ -\u003e 12mol/liter (approx)\n\nSo if we're storing solids then:\n1 liter of FeCl₂ requires 0.45 liter of NaOH and makes 0.3 liters of Fe(OH)₂ and 0.64 liters of NaCl, and this stores about 630wh of energy.\n\nIf we want to store everything as a sludge in 25% water, we keep all of the numbers the same but reduce the energy storage by 1/4.\n\nConservatively, we might think about storing 0.5kwh per 3 liters of tanks. So similarly to the other reactions, we're in the same ball park of 3 cubic meters of materials storing 100kWh.\n\nBut these materials are quite a bit safer. Note: There are no papers I could find on this exact reaction, so there might be something fatally flawed with it that I'm not thinking of...",
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