How to distinguish between Lithium-ion and Lithium Polymer cell - Page 1
Forum section: electronics / projects

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 29, 2024, 04:48:14 pm
content: What is and how to distinguish between Lithium-ion and Lithium Polymer cell?What is 'grey soft pouch' cell that are universally found on modern cellular phone or other 'small size' devices (instead of 16500 big cylinderical cell) ?We need 50 to 100mAh and light weight.Many thanks

author: Siwastaja
author_rank: Super Contributor
timestamp: May 29, 2024, 05:54:14 pm
content: There is no such a thing as "lithium polymer" cell. It's a marketing term used to describe pouch cells. The chemistry itself is similar to other form factors. The "polymer" refers to the plastic used in the outer packaging (it's aluminum-plastic sandwich pouch).In 18650 cell, the internals are wrapped like a swiss roll, then pushed into metal cylinder. In a pouch cell, they have a "roll" with sharper edges, vacuum packaged into the plastic-aluminum pouch.Most professionals prefer to say "pouch cell" instead of "polymer".In 1990's, there were hopes in developing polymerized, solid electrolyte. This was the initial use of "lithium polymer". They never materialized commercially, but the term was reused by marketing after that.

author: IanB
author_rank: Super Contributor
timestamp: May 29, 2024, 06:05:33 pm
content: One issue with pouch cells is that they need external mechanical protection. If you puncture a charged cell it could easily go up in flames. The metal-cased cylindrical cells are much more robust and harder to damage.

author: amyk
author_rank: Super Contributor
timestamp: May 30, 2024, 01:39:23 am
content: Note that there are also rectangular (hard) metal-cased cells, although they tend to be less common.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 30, 2024, 07:45:32 am
content: In the pics first one with wide metal tabs is a raw cell, without any over-voltage, under-voltage, over-current or thermal fuse protection.The second one, with wires, has an internal PCB with a protection circuit on it, for the above situations. Same for the mobile phones batteries, they came with a protection PCB embedded in the metal or plastic enclosure of the battery.If you see the contacts are like wide metal sheet tabs, that's usually a raw cell, easy to damage or to set on fire. Never use raw cells to directly power your circuit. Similar for the round 18650 (or other sizes, 18x650 is the diameter x length), some have internal protection (made to be used by the end users), others are raw cells meant to replace dead batteries in battery-packs that have their own BMS (battery management system, like e.g. in laptop batteries, hand-tool drills, battery vacuum cleaners, etc.).Youmusthave a dedicated circuit to supervise rechargeable Li based batteries, because when discharged too much, Li recheargeables form internal metallic bridges (unrecoverable damage), and when overcharged they catch fire. Same if the current is too high (either during charging, or during discharging) or when a short-circuit happens.

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 30, 2024, 10:25:39 am
content: Many thanks. The grey plastic pouch cell are 'universally' used in device with hard casing.What chemistryare mostly used forwatch and wearable (fitbit type)?Seem LCO has highest energy at 200 Wh/kg and 400 Wh per litre. LMO is 150 and 350 respectively.TIA

author: Siwastaja
author_rank: Super Contributor
timestamp: June 01, 2024, 02:38:51 pm
content: Quote from: Wilson__ on May 30, 2024, 10:25:39 amIt's funny how stuff like this, written in 2005 or something, still pops up.LCO went beyond 200Wh/kg and while probably still available, has been mostly superseded by other chemistries like NCA, NMC and whatnot. NCA specifically is said to be of highest energy density, but nothing is clear-cut like that. Chemistries have subtleties. All that matters is, what cells are commercially available to buy, and what are their actual specifications. You might not even know what the chemistry is.

author: amyk
author_rank: Super Contributor
timestamp: June 02, 2024, 02:54:07 am
content: These days the majority of cells are likely to be NMC.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: June 02, 2024, 01:14:41 pm
content: Good Morning Wilson, by the term Lithium Polymer, could you have meantLiFePO4 batteries

author: salihkanber
author_rank: Regular Contributor
timestamp: June 02, 2024, 01:27:43 pm
content: Are you sure of the mah capacity of 50-100? Regularly its around 300mah. Afaik 4 smaller sizes and form factors, pouch cells are commonly used. Addition to that, you can go for rechargeable coin cells such as: Citizen MT920, or search for other ready-made smart watch batteries as spare parts.