Using the yet even more expensive LiFePO4 instead of lithium though their preformance is roughly equivalent (LiFePO4 has more cycles & is safer than lithium) vs the typical scooter type SLA/AGM;
LiFePO's are Lithium too.
'The lithium iron phosphate (LiFePO4) battery, also called LFP battery (with "LFP" standing for "lithium ferrophosphate"), is a type of rechargeable battery, specifically a lithium-ion battery, which uses LiFePO
4 as a cathode material. LiFePO4 batteries have somewhat lower energy density than the more common LiCoO2 design found in consumer electronics, but offers longer lifetimes, better power density (the rate that energy can be drawn from them) and are inherently safer. LiFePO4 is finding a number of roles in vehicle use and backup power.'
For cheap however heck you can just use 3 12V deep cycle marine batteries in series if you don't need the basket space, even at $80 a pop so $240 that is still far less than sealed LA or Lithium and it will run you awhile, half an hour or more maybe with a smallish motor, they just need a long charge time.
Yes, Lead Acid is big, heavy and potentially messy but cheap, it just has 6 2V cells in series.
That LI power brick I had made is 2.5x more expensive but less than 1/2 the size of 3 marine batteries at about the size of a phone book and has 120 3.6V cells arranged as 10 series banks of 12 parallel cells for ~35A constant power and *poof* nothing, LA's start strong and then just slowly loose power as they drain which anyone who has ever had a car has seen.