I read the abstract.
It is not even about a battery. It is about a supercapacitor.
The energy densities are very small. 12 Watt-hours per kg. From the abstract:
Moreover the assembled supercapacitor device yields a maximum energy density of 12 Wh kg–1, which is higher than that of commercially available supercapacitors.
The energy density of lithium-ion batteries are typically 100 - 265 Wh kg–1.
This experimental, laboratory device, has about 4-12% the energy density of existing lithium-ion batteries.
“Experts say”
NEVER question the experts. They are experts, we are little people.
Energy density vs power density. Energy density is needed for long range. Power density is needed for regenerative braking and energy recovery. The energy it takes to accelerate a full sized sedan from 0 to 60 mph is only 200 watt hours. Conversely it takes the same energy to slow to zero from that same speed. Hybrids get such great mileage in city traffic recovering that energy that would be dissipated as heat in the friction brakes. This energy recovery doubles the mileage of a hybrid in stop and go traffic compared to a straight ICE of comparable size. 200wh is only 16 kilos for 100 % recovery in a hybrid. If it’s cheap to make “cooking” is pyrolysis under pressure with no oxygen not an expensive process at all. They are making structured high surface area carbon from plant based carbon chains. Also of interest would be cycle life super capacitors have cycle life measured in the hundreds of thousands of full depth of discharge vs 5000 of lithium ion. With those kinds if cycle life you could do a charge optimised hybrid run cycle. It takes one kWh to send a full-size Tesla 4 miles a 250 kg pack would hold 3kWh of juice enough for 12 miles of all electric driving. The engine would be run at its most efficient point to charge up the pack then shut down for a 12 mile cruise then on again for 12 more miles ect. An Atkins cycle hybrid engine such as in the Prius has a peak efficiency of 43% gasoline to electricity. That’s 60 mpg (114,000btu lhv of petrol*0.43/3414 by/kWh) in a full sized car not a Prius sized car. In a small Prius sized car at 6 miles to the kWh it’s 85 mpg tank to wheels. Since the Super capacitors can take so many cycles you can only run the engine at its peak efficiency to charge the pack intermittently. Put this in perspective the avg American as in 92% percent verified by the DOT commute 35 miles or less each day. The engine would run 3 times to cover that distance while getting over 60 mpg for the trip. Being able to charge at home and work would cut that to twice each way. The Prius motor system is 99PS or 73kw to put 3 kWh into the Super capacitors would take 2.46 minutes of run time at 73kw output. Which means to cover 35 miles the engine would only run three times for 2 and a half minutes each time at peak efficiency. That is the value of high density Super capacitors