I've noticed an odd trend in the lithium-ion batteries used in smartphones and tablets: rather than the 3.6V or 3.7V per cell typical of most Li-ion batteries in other types of consumer devices, they use 3.8V batteries that are charged to a maximum voltage of 4.35V (this is the case with both my Nexus 5X and Nexus 9). In at least one case (the LG G5 battery), the battery has a nominal voltage of 3.85V and is charged to 4.4V.
What's with these high-voltage Li-ion cells? I can understand that the higher voltage translates to more overall energy, but why pursue higher voltage instead of just higher capacity (as is done with 18650 cells)? Is there a drawback to using this type of battery?
A chat discussion starting here suggests that this higher voltage is specific to Li-poly batteries and does not apply to cylindrical cells like 18650 or prismatic cells like the sort used in compact camera batteries. Is this indeed the case?
Best Answer
So I did some research and found out that there's a recent advance in battery technology that allows LiPo cells, used in both mobile devices and hobbyist/RC applications, to operate at higher voltages. Specifically, a silicon-graphene additive is used in the anode to protect against corrosion at higher voltages, allowing them to be charged to 4.35V or even 4.4V. This results in slightly higher energy density, but charging the battery to higher voltages can reduce its service life.
The high power consumption of mobile devices means that high energy density is more important than any other characteristic. This means that reduced service life is an acceptable trade-off; since the typical consumer replaces their smartphone every two years, service life is not a major requirement.
In essence, the higher voltage is just another avenue of increasing overall energy density.