Comment by adrianwaj
2 days ago
“You need to keep an LFP cell at 25 °C, give or take, or it will rapidly degrade” so LFPs have to be heated and cooled - not difficult to solve but it does add cost and complexity to a battery, something Sodium-Ion doesn't require.
But looking at the discharge profile of Sodium-Ion [1], then a 24v stable output would need about 48v at 100% battery charge and that means cost and complexity on the input and output sides to keep a steady voltage over the discharge cycle. LFP have a much flatter discharge curve but it's a much greater concern with Sodium Ion. Sodium Ion is also criticized for its lifetime cycle degradation.
LTO (Lithium Titanate) batteries hit the sweet spot between both chemistries and are used in electric buses, but I still like Sodium batteries for their environmental considerations.
Wouldn't it be great to somehow harvest power from the temperature swings between night and day in arid regions? Also large changes between sea level and cruising altitude.
I know black tourmaline and certain lithium compounds being pyroelectric generate power upon temperature change due to mechanical stress, which instigates piezoelectricity.
"If the goal is maximum electrical energy generated per degree shift, single-crystal PMN-PT (Lead Magnesium Niobate–Lead Titanate) is currently the top-performing synthetic material." [2]
[1] https://hackaday.com/2025/10/30/why-sodium-ion-batteries-are...
LFP’s flat discharge curve is actually kind of annoying: it makes it quite difficult to measure the state of charge of a cell. BMSes mostly need to track the SoC by counting coulombs, and balancing a series of cells may be challenging unless the SoC to reach the steeper part of the curve.
Meanwhile, most serious applications have power conversion circuitry, so a variable voltage may not be much of a problem.
The low-end “12V” LFP packs without real BMSes or power conversion that sort of pretend to be lead-acid batteries in RVs and such are awful designs and work pretty poorly, and their “24V” and “48V” cousins are not much better. It’s true that Na-Ion may not be an easy drop-in replacement. That being said, some people are working on Na-Ion as a lead-acid replacement for car starter batteries (and for low voltage systems in EVs), and they have a lot of potential in this application. (LFP doesn’t have adequate not temperature performance and lead-acid sucks for many reasons.)