Alright domain experts of HN - tell me why this is too good to be true.
Among these are: ability to mass produce, resistance to mechanical stresses, safety, peak performance, low auto-discharge, ability to recycle, energy density, charge cycles, efficiency, availability of materials, operational temperature range, storage temperature range.
The latter criteria seem to be well addressed in the paper, the first few not really, or only tangentially (based on a quick ctrl+f for some of the key words).
But the abstract says that they're made using sulfur stabilized by[1] carbon nanofibers[1]. Great: now make a million of them.
1: EDIT: nanofibers stabilize the sulfur, but it is not encapsulated. The phrasing "within" in the abstract threw me for a loop.
Material synthesis Synthesis of CNFs. The free-standing CNFs were made by electrospinning. Typically, 10 wt% polyacrylonitrile, was added to DMF and stirred overnight to form a polymeric solution.
This solution was then loaded into a Becton Dickinson 5 mL syringe with a Luer lock tip and an 18-gauge stainless steel needle (Hamilton Corporation). The syringe with the needle was connected to a NE-400 model syringe pump (New Era Pump Systems, Inc.) to control the feeding rate of the solution.
The grounded aluminum collector was placed 6 in. from the tip of the needle. Electrospinning was performed at room temperature with a relative humidity below 15%. A potential difference of 7–8 KV (Series ES -30 KV, Gamma High Voltage Research, Inc.) was applied between the collector and the tip of the needle. The flow rate of the solution was kept constant at 0.2 mL h−1.
The as-spun nanofibers were collected and stabilized in a convection oven at 280 °C for 6 h in air atmosphere.
The stabilized nanofiber mats were then placed in alumina plates and carbonized in a nitrogen environment up till 900 °C at a ramp rate of 2.5 °C min−1 and then activated under CO2 flow for 1 h in a horizontal tube furnace (MTI. Corp). The furnace was then cooled at 2 °C min−1 until it reached room temperature.
Monoclinic γ-sulfur deposition on CNFs. The free-standing CNF mats were pun- ched with stainless steel die (φ = 11 mm) and dried at 150 °C overnight under vacuum.
The CNF discs were then weighed and placed in an in-house developed autoclave (Stainless steel 316) and subjected to 180 °C for 24 h in an oven. The autoclave consisted of a sulfur reservoir at the bottom and a perforated disk for placing electrodes at the top. After 24 h the autoclave was cooled to room tem- perature slowly in a span of 6–8 h.
The electrodes were weighed and transferred in an Argon-filled glove box via overnight room temperature vacuum drying in the antechamber for battery fabrication.
>we stabilize a rare monoclinic γ-sulfur phase within carbon nanofibers
and my mind jumped to "sulfur inside a nanotube again". But the sulfur isn't "within" the carbon nanofibers, as they later specify, and this is new.
>We demonstrate that despite an exposed “un-confined” deposition of this sulfur phase on the host carbon material, the carbonate-based battery exhibits high reversible capacity
The sulfur is in contact with the electrolyte. And it works! That's not supposed to happen, but now it does. So the process you described doesn't make carbon nanotubes, it makes nanofibers, which are much simpler (you don't need axial concentric planes).
So lithium titanate, lithium cobalt, lithium manganese oxide, nickel cobalt manganese(NCM), nickel cobalt manganese Aluminum(NCMA), lithium iron phosphate(LFP), and now lithium sulfer are all related but they have very different trade offs. 15 years ago Li-Ion battery tech meant worse trade offs so fewer charge cycles, slower charging, less energy per charge, more costly etc etc.
And yes, NCM and NCMA both use lithium.
Some hot takes:
- Price per cell has dropped ~97% since 1991
- 1991 energy density ~200 Wh/liter; 2005 energy density ~500 Wh/liter; 2017 ~700 Wh/liter
[0]: https://pubs.rsc.org/en/content/articlelanding/2021/ee/d0ee0...
https://arstechnica.com/science/2021/05/eternally-five-years...
Now and again there's an actual advance and we rejoice, but if you keep an eye on cutting edge stuff it's got to happen a lot that some promising lead leads nowhere.
If you goal is to learn about things once they're stable and working, I suggest drop reading science journalism from your schedule and just start window shopping at electronics stores.
[italics mine]
These are bold claims. You don't hear that every day. Polysulfides have been an accepted fact of life in Li-S batteries forever.