If it wasn't so important for the future of electric cars, it could almost get tiresome: Just how do you improve batteries for longer life, quicker charging and a greater range?
It's a question being investigated by great minds all around the world, and has turned up some surprising and exciting results over the last few years.
Inspired by Popular Mechanics' look at potential electric vehicle and hybrid battery breakthroughs, we've compiled many of our previous battery tech articles into one handy guide. Which of the following will be our batteries of the future?
Aluminum-air
We've all heard--and laughed off--stories of water-powered cars. It just isn't possible on any practical, car-based level.
But aluminum-air uses water in a different way. Aluminum is used as the anode in a battery, ambient air (and the oxygen in it) as a cathode, and water molecules. Combined in the battery, they produce hydrated aluminum oxide and energy--and that energy can be used to power a car.
The aluminum plates used have high energy density, and companies testing it such as Phinergy say you'd need to refill the car with water every few hundred miles. The air--well, that's all around us.
Want to try the physics for yourself? You can even buy a small-scale kit...
Improved lithium-ion
Existing lithium-ion technology is among the best battery technology we have for electric cars and hybrids.
Compared to other battery types it's relatively energy-dense, charges relatively quickly, is lighter than many other battery types, and it's tried-and-tested. But it isn't perfect, and several research groups are looking for a way to improve on its existing strengths.
![Egg-like nanoparticles for lithium-ion batteries. [Image: Zhi Wei She et al., Stanford University]](https://images.hgmsites.net/lrg/egg-like-nanoparticles-for-lithium-ion-batteries-image-zhi-wei-she-et-al-stanford-university_100415061_l.jpg "Egg-like nanoparticles for lithium-ion batteries. [Image: Zhi Wei She et al., Stanford University]")
Egg-like nanoparticles for lithium-ion batteries. [Image: Zhi Wei She et al., Stanford University]
Others have researched into the existing problems with lithium-ion tech--such as reducing the tendency for lithium to gather around the battery electrodes.
Then there's lithium-air tech--an offshoot of lithium-ion batteries, and one that could significantly increase energy density. Whatever technology is explored, lithium-ion will certainly be here for many more years.
Herbs
It sounds unlikely, but simple herbs could be employed to make batteries greener in future.
In a rare look at improving the environmental aspects of batteries rather than increasing their range, researchers at Rice University and the City College of New York have looked at using the herb madder, or purpurin, as a natural cathode for lithium-ion batteries.
You might not gain hundreds of miles, but any eco-minded electric car driver would be glad to know their batteries had just a little less impact on the environment, right?
Graphene paper. Image: Lisa Aliosio
Graphene
It's one of the biggest breakthroughs of the 21st century so far, and something we'll be hearing a lot more of whatever industry you look at: graphene.
The "wonder material" is essentially a single-atom-thick lattice of carbon atoms. It's light, incredibly strong for its size, and incredibly electrically conductive. And if those aren't qualities that'd be useful for batteries, we don't know what else is...
Graphene's light-weight benefits are being explored, using graphene rolled into carbon nanotubes and then weaved into an 'Aerographite' material. Graphene 'foam' also has potential--graphene grown on a metal foam to form a three-dimensional structure, both light, flexible and highly conductive.
Software
All electric car batteries are controlled by the software of the vehicle they're in. The car measures the battery life, state of charge, temperature and other parameters and tries to maintain each one to its most efficient degree.
The trouble is, all this is being measured using just voltage and current, and it's not too sophisticated as a result. Some researchers are studying how more sophisticated software could control a battery much more tightly, meaning less margin of error would have to be built into packs--making them smaller and lighter.
New algorithms can estimate the position of charged particles, allowing for much more precision and less over-engineering.
Extracting Lithium Carbonate From Brine 
Another substance aimed at greening batteries, rather than improving range and other factors, is brine.
Yep, that salty water substance. Plenty of it is bubbling out of the ground through the San Andreas fault in California, and it's bringing minerals with it--including lithium. Collecting lithium from the brine is a more ecologically-friendly way of gathering it than digging huge mines, that's for sure.
Better still, all that brine is already being put to good use--the hot liquid is used to drive turbines for geothermal energy plants.
Others
Several other technologies are currently being explored, almost too numerous to mention.
We've covered the unusual look at lead-acid batteries ourselves, since one startup still sees potential in them for hybrid vehicles.
Popular Mechanics covers several more, including copper nanowire cathode lithium, which use the higher surface area of nanoscopic copper wire to store more lithium ions. Lithium silicone polymer is another energy-dense format, as is a stable lithium-manganese chemistry.
No doubt more technologies will emerge over the next few years--and we'll be keeping this guide updated as they do.
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