All too often searches for information on how you can 3D print a battery doesn’t turn up the answer you would expect. This popular YouTube video, for example, is only about printing the battery case. The rest needs to be put together in the same sort of way that all batteries are built. But is that all about to change?
In 2016 claims started surfacing in the press that 3D printed batteries were a reality and not only as a theoretical laboratory experiment.
Scientists found that graphene, a form of carbon, could store electricity on its surface and as graphene is a two dimensional material you only need a sheet that is one atom thick in order to create something workable. Something that is one atom thick is also much easier to print than the bulky nature of a traditional battery.
The surface storage characteristic means that graphene based power storage has no moving parts which degrade over time – the reason why most batteries die in the end – so printable and ever lasting?.
The existence of graphene has been suspected for decades, but it was only produced for the first time in 2004. Over one hundred times stronger than steel but highly flexible it held many possibilities especially in the form of wearable power storage.
By late 2017, Brunel University in London had done just that and claimed to have developed fashionable bracelet batteries.
Industry cover up?
A 3D printable battery that could charge within seconds and potentially last a lifetime. So why did this news not grab every headline worldwide? Was this an industry cover up?
Unfortunately on closer inspection graphene based power storage units are not all that they seem. To begin with they are not actually batteries, they are super-capacitors. This means they are technically different in their structure and also fundamentally different in their character.
A super capacitor stores electricity on its surface while a battery stores it in chemical form. To charge a battery up requires an internal chemical process to take place over several hours while atoms and particles are moved around inside. The super-capacitor requires a simple ‘change of state’ which means it can be fully charged in a matter of seconds.
This static electricity stored on a super-capacitor is similar to that which can build up on you when wearing certain clothing. Remove a sweater and you take on a positive charge. Touch a door handle and you feel a small shock as you discharge.
The super-capacitor limitations
This is what super capacitors are all about – charging fast and discharging fast, but also self-discharging fast. In fact even if you fully charged a super capacitor and then didn’t use it at all for a month it would still be all but flat. They self-discharge faster, way faster than batteries where most alternatives Sealed Lead Acid batteries or Lithium self-discharge only a few percent per month.
Many items in our modern life such as smartphones need power sources that discharge slowly over long periods, that’s not something super-capacitors do well.
Punting the super-capacitor as a ‘phone charger instead is also questionable. Chargers themselves need to dispense steady power over long periods in order to work with the slow speed at which batteries can take on power. Super capacitors are at their best when they discharge fast.
This is not to say that a super-capacitor can’t charge a smartphone, just that there are other backup options (basically other batteries) that do it better and cheaper even if they can’t form part of your clothing or jewelry.
But there are times when the fast charge and discharge super-capacitors offer makes sense.
It may also come as a surprise to find that super capacitors are already in widespread use as a power source. China has a number of urban buses solely powered by them. Energy created by braking to pick up passengers can be passed to the super-capacitor and used moments later as the vehicle needs power to accelerate away.
The reality of 3D printed batteries
So while a super-capacitor is like a battery, it isn’t actually a battery. A super capacitor can be 3D printed but its nature means that it currently only has limited use in every day life.
Other suggestions that batteries themselves can be printed turn out to be half solutions such as printing only a battery case. Batteries remain too complex and contain too many materials for today’s 3D printing technology, but that does not mean some breakthrough is just around the corner.