Posts Tagged‘lithium ion’

Lithium-Air Batteries are the Future, Still Many Years Away.

There’s no question about it: batteries just haven’t kept pace with technological innovation. This isn’t for lack of trying however, it’s just that there’s no direct means to increasing energy densities like there is for increasing transistor count. So what we have are batteries that are mostly capable however have not seen rapid improvement as technology has rocketed away to new heights. There are however visions for the future of battery technology that, if they come to fruition, could see a revolution in battery capacity. The latest and greatest darling of the battery world is found in a technology called Lithium-Air, although it becoming a reality is likely decades away.

ambl012_fig_2Pretty much every battery in a smartphone is some variant of lithium-ion which provides a much higher energy density than most other rechargeable battery types. For the most part it works well however there are some downsides, like their tendency to explode and catch fire when damaged, which have prevented them from seeing widespread use in some industries. Compared to other energy dense mediums, like gasoline for example, lithium-ion is still some 20 times less dense. This is part of the reason why it has taken auto makers so long to start bringing out electric cars, they simply couldn’t store the required amount of energy to make them comparable to gasoline powered versions. Lithium-Air on the other hand could theoretically match gasoline’s energy density, the holy grail for battery technology.

Lithium-air relies on the oxidation (essentially rusting) of lithium in order to store and retrieve energy. This comes with a massive jump in density because, unlike other batteries, lithium-air doesn’t have to contain its oxidizing agent within the battery itself. Instead it simply draws it from the surrounding air, much like a traditional gasoline powered engine does. However such a design comes with numerous challenges which need to be addressed before a useable battery can be created. Most of the research is currently focused on developing a cathode (negative side) as that where the current limitations are.

That’s also where the latest round of lithium-air hype has come from.

The research out of Cambridge details a particularly novel chemical reaction which, theoretically, could be used in the creation of a lithium-air battery. The reaction was reversed and redone over 2000 times, showing that it has the potential to store and retrieve energy as you’d expect a battery to. However what they have not created, and this is something much of the coverage is getting wrong, is an actual lithium-air battery. What the scientists have found is a potential chemical reaction which could make up one of the cells of a lithium-air battery. The numerous other issues, like the fact their reaction only works in pure oxygen and not air, which limit the applicability of this reaction to real world use cases. I’m not saying they can’t be overcome but all these things need to be addressed before you can say you’ve created a useable battery.

Realistically that’s not any fault of the scientists though, just the reporting that’s surrounded it. To be sure their research furthers the field of lithium-air batteries and there’s a need for more of this kind of research if we ever want to actually start making these kinds of batteries. Breathless reporting of progressions in research as actual, consumer ready technology though doesn’t help and only serves to foster the sense that the next big thing is always “10 years away”. In this case we’re one step closer, but the light is at the end of a very long tunnel when it comes to a useable lithium-air battery.

The New Battery Tech Conundrum.

The batteries in our portable devices never seem to be big enough, in fact in some cases they seem to be getting worse. Gone are the days when forgetting to charge your phone for days at a time wasn’t an issue and you’ll be lucky to get a full day’s worth of use out of your laptop before it starts screaming to be plugged back into the wall. The cold hard fact of the matter is that storing electrical energy in a portable fashion is hard as energy density is often a function of surface area, meaning those lovely slim smartphones you love are at odds with increasing their battery life. Of course there are always improvements to be made however many breakthroughs in one aspect or another usually come at the cost of something else.

saupload_775px_supercapacitors_chart.svgTake for instance the latest announcement to come out of Stanford University which shows a battery that can be fully charged in under a minute and, if its creators are to be believed, replace the current battery tech that powers all our modern devices. Their battery is based on a technology called aluminium ion which works in a very similar way to the current lithium ion technology that’s behind most rechargeable devices. It’s hard to deny the list of advantages that their battery tech has: cheaper components, safer operation and, of course the fast charging times, however those advantages start to look a lot less appealing when you see the two disadvantages that they currently have to work past.

The voltage and energy density.

As the battery tech stands now the usable voltage the battery is able to put out is around 2 volts which is about half the voltage that most devices currently use. Sure you could get around this by using various tricks (DC step up converter, batteries in series, etc.) however these all reduce the efficiency of your battery and add complexity to the device you put them in. Thus if these kinds of batteries are going to be used as drop in replacements for the current lithium ion tech they’re going to have to work out how to up the voltage significantly without impacting heavily on the other aspects that make it desirable.

The latter problem is the more difficult one and is something that all new battery technology struggles with. With any battery tech you’re usually balancing quite a few factors in order to make the best tradeoffs for your particular use case however one of the most typical is between charge times and the amount of power you can store. In general the quicker your battery can charge the less dense it is energywise, meaning that fast charge time comes at the cost of usable life once it’s off the charger. Indeed this is exactly the issue that the new aluminium ion battery is struggling with as its current power density does not match that of lithium ion.

Now this isn’t to say that the idea is worthless, more that when you hear about these amazing kinds of batteries or supercapacitors (different kind of technology, but they’re an energy storage medium all the same) that have some kind of revolutionary property your first reaction should be to ask what the trade offs were. There’s a reason why sealed lead acid, nickel metal hydride and other seemingly ancient battery technologies are still used the world over; they’re perfect at doing the job they’ve found themselves in. Whilst charging your phone in a minute might be a great thing on paper if that came with a battery life that was a mere 20% of its long charging competitors I’m sure most people would choose the latter. Hopefully the researchers can overcome their current drawbacks to make something truly revolutionary but I’ll stay skeptical until proven otherwise.