How do you think discharge rates would affect the battery? Would it behave like a LFP that basically outputs mostly the same rate of Amps in the full spectrum of charge (Voltage varies little with discharge %)
Do you think an approach like this generates bateries with long lifetimes?
Did you expect balancing of these particular batteries to be particularly complicated?
Li-ion batteries have solid particles that Li ions migrate into and out of. This can cause particles to break up, especially at high charge/discharge rates. Because there are fewer ions to migrate, fast discharge at low charge is bad for battery lifetime and gives lower voltage.
SMAC batteries have solid particles that dissolve and form as the battery is operated. It doesn’t matter if those break up. To some extent, the maximum discharge rate would decrease as some smaller particles disappear during discharge. There’s also some Ostwald ripening that happens, which decreases discharge rate a bit over time, until the next charge cycle, but the extent is limited.
Li-ion batteries are limited largely by SEI growth from electrolyte-Li reaction. Charging and discharging accelerates SEI growth because it causes cracking in the existing SEI, especially at high rates.
SMAC battery lifetime would probably be limited by water migration, with charge cycles being irrelevant and only time & temperature being important, but the long-term lifetime isn’t clear at this point. Yes, there is a SEI in SMAC batteries, but it’s a thin SEI that works for Na but not Li, with less surface area, so it wouldn’t cause much capacity loss.
The relative charge rate of Li-ion vs SMAC depends on the thickness of the electrolyte layers, which depends on the manufacturing process rather than the chemistry. The experimental data I got doesn’t really indicate this because an insulating oxide layer was forming, and because the test cells used much thicker layers than commercial cells would. But I’d expect it to be similar, meaning max charge rates between 0.1C and 10C.
How do you think discharge rates would affect the battery? Would it behave like a LFP that basically outputs mostly the same rate of Amps in the full spectrum of charge (Voltage varies little with discharge %)
Do you think an approach like this generates bateries with long lifetimes?
Did you expect balancing of these particular batteries to be particularly complicated?
Basically, tell us more!
Li-ion batteries have solid particles that Li ions migrate into and out of. This can cause particles to break up, especially at high charge/discharge rates. Because there are fewer ions to migrate, fast discharge at low charge is bad for battery lifetime and gives lower voltage.
SMAC batteries have solid particles that dissolve and form as the battery is operated. It doesn’t matter if those break up. To some extent, the maximum discharge rate would decrease as some smaller particles disappear during discharge. There’s also some Ostwald ripening that happens, which decreases discharge rate a bit over time, until the next charge cycle, but the extent is limited.
Li-ion batteries are limited largely by SEI growth from electrolyte-Li reaction. Charging and discharging accelerates SEI growth because it causes cracking in the existing SEI, especially at high rates.
SMAC battery lifetime would probably be limited by water migration, with charge cycles being irrelevant and only time & temperature being important, but the long-term lifetime isn’t clear at this point. Yes, there is a SEI in SMAC batteries, but it’s a thin SEI that works for Na but not Li, with less surface area, so it wouldn’t cause much capacity loss.
The relative charge rate of Li-ion vs SMAC depends on the thickness of the electrolyte layers, which depends on the manufacturing process rather than the chemistry. The experimental data I got doesn’t really indicate this because an insulating oxide layer was forming, and because the test cells used much thicker layers than commercial cells would. But I’d expect it to be similar, meaning max charge rates between 0.1C and 10C.
I’m not sure why balancing would be different.