Batteries are an important part of our lives, whether in phones or laptops. The technology is evolving, as is best practice to maintain your batteries in their best health.
An early contender was NiCad (Nickel Cadmium) followed soon my NiMH (Nickel Metal Hydride). NiCad couldn’t store much power for their size, in both NiCad and NiMH, the power drained away quite fast and had another big problem. This was that they could lose capacity quite easily, due to overcharging. When most laptops used NiMH batteries I recommended taking the battery out if using it mostly on the mains. Otherwise the battery gets ‘cooked’ and won’t hold charge. Then the battery tells the computer it doesn’t feel well and the computer won’t start unless the battery is removed.
NiMH is still used for conventional rechargeable batteries like AA
Battery technology has moved on and for devices built around rechargeable power (Phones, tablets and laptops) Lithium-ion is the current market-leader. This is more efficient for its size, retains charge longer and can be moulded around other components. This means that it is quite hard to remove the battery, but fortunately modern devices have circuitry to prevent the overcharging of batteries. Nevertheless there is still a downside, which is the number of full recharge cycles affects the capacity of the battery. So, unlike NiCad and NiMH, it is a bad idea to run Lithium Ion batteries right down. Recharging at 20% or so will prevent a full recharge cycle and preserve your battery for longer
The latest technology is Lithium Polymer, which is safer than other batteries. These batteries can also be made in much thinner sizes and also hold more power for their size, although they have a shorter life. Apple uses this type of battery quite extensively. These batteries tend to be in pouches rather than rigid container and the main downside is as they get to the end of their life, they tend to expand. I’ve seen a phone with the back pushed off and had a laptop which ‘blew’ the back off when I took the screws out.