Lithium-ion Batteries Do Age Through Charge Cycles
Today’s lithium-ion batteries are more efficient than you might expect. Some of the old beliefs about these batteries, like, “Always let your battery run down to a full discharge before charging” just aren’t true anymore. However, there is one thing that will always age an iPhone battery: completing a charge cycle, or using an equivalent of 100% of the battery’s power, and then recharging that power to 100%.
Over time, use degrades the chemical composition of the battery in small ways, which leads to what we think of as battery aging. iPhone batteries are designed to maintain at least 80% of their charge capacity for as long as possible, currently up to around 500 cycles, but charge cycles always take their toll. There isn’t a way around that either, other than using your iPhone less and ultimately charging it less often.