What's difference in LI-ion and Li-polymor power banks

Hey I've seen one power bank named PTron Bravado power bank which is having Li-ion batteries insted of :LI-ion batteries, And realy What all avail in markt are LI-ion batteries including mobile batteries. What's best things in polymor battery, Why any other brands like mi, lenovo, anker, ambrane all doesn't have polymor battery.
What's difference in LI-ion and Li-polymor power banks

Honor holly or panasonic P55 or spice Mi 549

I want to buy Android smartphone under 8000.
want
1. fuzz free ownership
2. solid build quality
3. good display ( crisp and above 5 inch)
4. good battery backup
5. good internet speed

processor speed does not bother me as a have to use it for internet browsing only.

I short listed
Honor holly (6999/-)
Panasonic P55 (7500/-)
and spice Mi 549 (6999/- with power bank and 1500 discount coupons at HomeShop18)