We’ve had a lot of questions since our last post on lithium ion batteries versus lithium polymer batteries, so we’ve decided to revisit the popular battery comparison. Chances are, if you’re a regular enough reader of the RAV blog to remember that post, you would probably self-describe as a hardcore power nerd. In that case, read on. For the rest of you, the question of whether to “choose” li-ion or li-po batteries can be answered both briefly and bluntly:
Don’t worry about it.
We know, we know. Being in the small minority of people who talk about batteries for a living, we’re going against our grain here. But the thing is, for most applications the li-ion versus li-po question isn’t relevant to the consumer—which option is better is highly contextual, and the decision tends to be made by manufacturers based on the perceived needs of the device.
As we noted in our history of power bank technology, thanks to Apple’s engineering chutzpah the batteries for mobile devices, laptops and most other battery-powered consumer tech are now custom-designed to take best advantage of the decreasing space available to manufacturers. If you can’t remove the standard battery without a high level of technical ability, that means few third-party companies will attempt to produce their own superior alternatives. And that, in turn, means that consumers are basically stuck with whichever kind of battery the manufacturer elected to install themselves.
If high efficiency and long battery life are important to you, you’re best off simply looking up the benchmarks announced by the manufacturers, and checking out some reviews from reputable tech blogs to make sure they hold up under real world conditions. This information will tell you a lot more about the quality of the battery than its type will.
Even if you have a li-ion power bank and a li-po battery (or vice versa), they’ll work together fine—as we noted last time, a handful of our power banks use li-po batteries, but like most manufacturers, we primarily use li-ion batteries.
Still there? Okay, time for the nitty-gritty.
Li-Po, Li-Ion: The Difference?
Now that we’ve got the dilettantes out of the room, we can clue to you in to a big secret: there are virtually no true lithium polymer batteries currently in use. Our friends at BatteryUniversity.com have the scoop:
A solid polymer has poor conductivity at room temperature, and the battery must be heated to 60°C (140°F) and higher to enable current flow. Large polymer batteries for stationary applications were installed that needed heating, but these have since disappeared. The much anticipated hype of the “true plastic battery” promised in the early 2000s did not materialize as conductivity could not be attained at ambient temperature.
For the most part, when you hear people talking about lithium polymer batteries in electronics today, they’re actually referring to lithium-ion polymer batteries. Working on the same internal principles as standard li-ions, lithium-ion polymer batteries are constructed with laminated sheets instead of the rigid shell that li-ion batteries require.
Fun Fact: Sometimes these deceptive batteries actually contain no true polymers whatsoever, which may offend certain battery puritans…)
This foil pouch shaves off about 20% of the weight of a standard li-ion battery, which is very attractive to manufacturers of extremely light devices. It also makes them more flexible: they can be folded into various shapes, or even pressed as thin as a credit card. The pouch is, however, more vulnerable to being ruptured if exposed. They also have the same potential for fire, short-circuiting, and charging errors.
Over time, the electrolyte can be vaporized by overcharging, causing the pouch to bloat. This reduces the reliability and endurance of the battery. Wikipedia’s page on lithium-ion polymer batteries even includes an image of a swollen pouch in an iPhone casing that is faintly reminiscent of a chubby corpse in its casket at a viewing:
As far the battery comparison goes for the end user, these “li-po” batteries are practically identical to li-ions, as they use the same materials for their cathodes and anodes and contain almost the same quantity of electrolyte.
For devices which do allow you to swap out the standard battery, the primary advantage offered by lithium-ion polymer batteries is that they weigh slightly less than lithium-ions with similar capacity. The disadvantage is that they may be less durable.
We hope this pragmatic review of the state of battery tech today has been useful to you! Let us know in the comments what you’d like to see us tackle in a future blog!