The future of mobile phone batteries
Lithium-ion batteries have served our needs quite well over the last two decades. They pack an impressive electrical power into a small package, and this has made them the phone manufacturers' preferred battery solution so far. Their performance has been constantly improving, while costs have gone down significantly. According to data-alliance.net, energy capacity per price has grown from the initial 0.3 watts-hour to over 3 watts-hour per dollar. Also, battery capacity has increased almost 10 times since the first prototypes have hit the market.
However, the current technology is really close to reaching its limits. While battery manufacturers are testing new solutions which will reduce risk hazards, for example the aqueous lithium-ion battery, there aren't too many things that they can do to increase Li-ion's energy density even further. So, let's take a look at some of the most promising batteries that utilize new technologies.
Solid-state batteries look very good in my book. They utilize a solid electrolyte, and this allows manufacturers to use lithium for the anode, thus having the ability to increase battery capacity while reducing safety risks. Actually, the technology isn't that new; people have been trying to create solid-state batteries since the 1950s. Nevertheless, those early prototypes had a very high internal resistance, and this has made them useless for real-life purposes.
Toyota and Panasonic have joined their forces back in 2017, with the goal of creating usable solid-state batteries. Several car makers, including BMW and Honda, are conducting research in this sector as well; as you can imagine, solid electrolytes are the perfect solution, because the resulting batteries can't damage electric vehicles due to overheating, fires or explosions.
Metal-air batteries provide an improved energy density in comparison with lithium-ion cells. Their anodes are made from various metals such as lithium, aluminum, germanium, magnesium, calcium, sodium or silicon. The electrolytes are often aqueous, while most cathodes utilize ambient air. Since these batteries are more efficient, they use less space, so they are perfect for next-gen smartphones.
Lithium-air batteries look very promising, being able to reach about 5,200 Wh/kg including oxygen, or over 11,000 Wh/kg excluding oxygen. Their voltage is quite low at 1.2V, so we'd need to use at least three cells to build a phone battery. Calcium-air cells have an open circuit voltage of over 3V, being followed closely by magnesium-air cells with 2.9V. One more thing: the existing lithium-air batteries can't be recharged at the moment, because the superoxide ion that's formed during the chemical reaction interacts with the electrolyte, modifying its properties. The problem may be solved in the near future, though.
Fuel cells convert the chemical energy that's often provided by hydrogen and an oxidizing agent into electrical energy. While these batteries can use oxygen from air, they also need a source of fuel. Accumulators that use fuel cells are quite old, being invented in 1838. Today, many of them are used as primary or backup electricity sources in remote areas.
Unlike lithium-ion batteries, the cells use hydrogen protons that move from anode to cathode through the electrolyte. Since a single cell produces about 0.7V, we would need at least five of them to create a phone battery. Typical energy efficiency ranges from 40% to 60%; however, if the resulting heat is captured, efficiency levels can reach 85%.
Microfuel cells can successfully power smartphones. While lithium-ion batteries can provide about 44 Wh/kg, fuel cell systems can easily reach values of over 500Wh/kg. Still, they cost about 400% more at the moment.
As phone manufacturers continue to release devices that have larger and larger screens, the demand for power increases as well. Fortunately, some of these new battery technologies look promising, and I'm pretty sure that prices will continue to go down as each technology matures.