After many questions and confusion over various Lithium Ion battery types discussed in this 18650 thread, I thought it would be useful to try and give a breakdown of the various categories of Lithium Ions. There are more details that could be given, but this is meant to just be a "handy" guide.
Edit: I recently did a "Safe Chemistry" 18650 Shootout here
Source References:
Three structural parts inside the battery can & top:
Two major categories of Lithium batteries:
.
.
Edit: I recently did a "Safe Chemistry" 18650 Shootout here
Source References:
Three structural parts inside the battery can & top:
- 1) When we talk about various Lithium chemistry batteries, most of the differences relate to the structure & metal alloy used in the positive cathode.
- 2) Since 1996, the negative anode made of graphite (carbon) has been well optimized.
- 3) The electrolyte is a Lithium salt solution, and may be a source of further improvements in the future.
Two major categories of Lithium batteries:
- 1) Lithium Primary (non-rechargeable) batteries which contain pure Lithium metal which is volatile in water/oxygen.
- 2) Lithium Secondary (Li-Ion or LiPo -rechargeable) batteries which contain Lithium as an cathode alloy or salt. They have no memory or self-discharge issues.
Four major categories of Secondary Li-Ion cell cathode metals:
- a) "Unsafe" Lithium Cobalt Oxide (Layered Structure) is the original Lithium Ion rechargeable cell, first made by Sony in 1991. It is what most people recognize as Li-Ion, and is now made by many companies such as Sony, Sanyo, Pila, Panasonic, AW (sales link), etc.
Lithium Cobalt is a more volatile cathode material with a higher resistance to the flow of ions, resulting in heat buildup.
It is best to use cells with separate built in protection circuit (AW & Pila), or pack with circuit board ("PCB") & balance tap leads going to each cell (or at least to groups of cells). This protection PCB resolves most of the safety concerns & issues.
It is best to use cells with separate built in protection circuit (AW & Pila), or pack with circuit board ("PCB") & balance tap leads going to each cell (or at least to groups of cells). This protection PCB resolves most of the safety concerns & issues.
- Limited charge/discharge loads without heating up (fire/explosion) are generally 1-2C (5 Amp discharge & 2 Amp charge in protected 18650 cell)
- Higher stored capacity. 18650 size has ~2200mAh
- Higher 3.6/3.7V nominal voltage, charges up to 4.2V
- Begins losing function (voltage drops) in 2-3 years after manufacture due to Lithium crystalizing onto Lithium Cobalt Oxide cathode layers, thereby increasing internal cell resistance.
- Useful rule of thumb for checking the voltage to determine charge capacity left in a Li-Cobalt cell.
These readings should be taken where cell has rested at least 15 mins after charge, not under any load.
4.2V Full 100%
4.1V About 90%
4.0V About 80%
3.9V About 60%
3.8V About 40%
3.7V About 20%
3.6V Empty
<3.5V Overdischarged
<3.0V Cell damage occurs (increasingly based on duration and how much lower voltage goes.)
4.1V About 90%
4.0V About 80%
3.9V About 60%
3.8V About 40%
3.7V About 20%
3.6V Empty
<3.5V Overdischarged
<3.0V Cell damage occurs (increasingly based on duration and how much lower voltage goes.)
- b) "Safe" Lithium Manganese (Spinel Structure) developed in 1996, with increased cathode surface area using a complex 3-dimensional cross-lattice "spinel" structure. Only made by: Emoli. Found in specific Ridgid or "Ryobi One+ Lithium" tool packs.
- Has much higher discharge rate of 10-15C (for 18650 cells that's 15-20 Amps output). It should be charged at 1-2C (1.5 to 3.0 Amps).
- Moderate stored capacity. 18650 size has ~1300mAh
- Higher 3.7/3.8V nominal, charging up to 4.2V
- Begins losing function (voltage drops) several years after manufacture due to Lithium crystalizing onto Lithium Manganese Oxide cathode.
- c) "Safe" Lithium Nickel Cobalt Manganese cathode. This is close to the previous category, but this combination gives a bit more capacity but a bit less output rate. This is the Sony V (or VT in 26700 size), Sanyo, or Konion is another licensed brand made in Germany. Found in specific Makita, Ryobi, Bosch tool packs.
- Has higher discharge rate of 5-7C (for 18650 cells that's ~10 Amps output). It should be charged at 1-2C (1.6 to 3.0 Amps).
- Moderate high stored capacity. 18650 size has ~1400mAh
- Higher 3.7V nominal, charging up to 4.1V (charging higher reduces cycle life from 800 to 300 cycles)
- Begins losing function (voltage drops) several years after manufacture due to Lithium crystalizing onto Lithium Nickel Cobalt Manganese Oxide cathode.
- d) "Safe" Lithium Iron Phosphate cathode. This has a huge leap forward in discharge rates, but with a lower capacity & voltage. It needs a separate charging setup. Saphion is one of the original brands, with other Chinese/Hong Kong versions springing up (including some from CPF member: AW). There is a "Nano" Lithium Iron Phospate made by the A123 Systems company which seems to have the highest quality and performance.
- Has very high discharge rate of 25-35C (for 18650 cells that's ~30 Amps output). Can be charged at 2-5C (2 to 6.0 Amps). Able to take significant user abuse.
- Moderate stored capacity. 18650 size has ~1100mAh
- Lower 3.3V nominal, charging up to 3.6V.
- Has longest life & number of cycles, but will still fail in several years. (I don't have exact handle on this.)
Last edited:
