David Briddock investigates if a battery technology breakthrough is imminent
Consumer interest in portable computing technology shows no signs of diminishing. Every year we see a new range of slimmer, lighter and more capable laptops, 2-in-1 devices, tablets, smartphones and smartwatches to satisfy demand.
Yet manufacturers and consumers alike continue to be frustrated by short battery life and long recharge times.
Limitations And Frustrations
The introduction of the rechargeable lithium-ion (Li-ion) battery was a portable technology milestone. Despite some undesirable limitations (see below), advances in Li-ion cell construction and power storage mean we’ve seen, on average, energy density increase by 5% per year and cost decrease by 8% per year.
Yet these gains have been offset by battery-draining, high-pixeldensity screens plus power-hungry processing and graphics chips. Today we’re just as far away from a mains-free battery utopia than we were a decade or two ago.
Our laptops rarely last a full working day. The latest smartphones are typically recharged daily. And who wants a smartwatch that needs to be charged every night? Even worse, it invariably takes many hours to fully recharge a battery pack – and up to an hour just to give it a quick boost.
It’s only because we love our mobile gadgets so much that we’re prepared to put up with these constraints. Even so, many owners feel a sense of foreboding, even panic, when they find themselves far away from a power socket with an almost drained smartphone battery.
Key Breakthroughs
What we really want is a laptop battery that lasts all day and still has the power to watch a movie in the evening. A smartphone battery that lasts a minimum of two to three days, or ideally a full week. And surely in 2016 it’s not too much to ask for a watch battery that last weeks on a single charge.
Well, in 2016 we seem to be on the threshold of innovations that could offer new hope for our communication devices, wearables, toys, electric vehicles, medical equipment and much more.
New anode/cathode materials and electrolytes promise a step change in both storage capacity and longevity. And nano technology, where engineering takes place at the atomic scale, keeps bringing new surprises.
We’re also making progress on the multi-hour charging time problem. The latest ultra-fast battery charging solutions can provide a 50% battery boost in minutes, which negates the need for ever larger, heavier battery packs.
Let’s take a look at some of the most promising technologies in more depth.
Huawei Smart Chip
One big Li-ion battery limitation is excessive heat buildup during charging. As you might expect, faster charging times tend to exacerbate this problem, so manufacturers play safe. The result is our typical multi-hour recharge timescales.
However, the giant Huawei organisation has a solution. It’s developed a tiny smart chip that can be easily embedded into all sizes of rechargeable batteries. These chips constantly monitor the health and status of the battery cells and report back to the charger.
Using this data, a higher recharge current can be applied until specified safety levels are reached. While this won’t be long enough to fully recharge the cells, it’s often enough to top it up to around 50–80%. This means we can top up our batteries in minutes instead of hours without the risk of overheating.
As Professor Rachid Yazami from the Nanyang Technological University in Singapore says, “In addition to knowing the degradation of batteries, our technology can also tell the exact state of charge of the battery, and thus optimise the charging so the battery can be maintained in its best condition while being charged faster.”
Another benefit is battery longevity. As we all know, Li-ion batteries gradually lose their storage capacity over time, discharging increasingly quickly. And this is an important issue when modern gadgets frequently have non-replaceable battery packs. The Huawei smart chip helps the battery achieve a greater number of recharge/discharge cycles.
Imagine a world where all batteries have Huawei-like smart chips. Laptops, tablets and smartphones can make do with fewer battery cells, making them smaller and lighter. Smartwatches and other wearable gadgets suddenly make more sense. And those batterypowered cars, helicopters, drones and robots are much more fun when a charge boost takes just seconds.
Other areas would be revolutionised too, such as the portable medical equipment industry. And what about fast-charging electric cars? At a stroke long journeys would be possible on modest-sized battery packs, allowing designers to create a new breed of smaller, lighter and more ergonomic personal transportation.
Oxis Li-S Battery
Li-ion limitations can be addressed through the use of alternative materials. Oxis Energy Limited is working on one of these alternatives, a lithium-sulphur (li-s) battery, which it hopes will revolutionise the rechargeable battery market.
The key factor in favour of Li-S is that it has, in theory, five times the energy density of Li-ion. In practice, this might work out at two or three times. Even so, a battery pack that lasts twice or three times longer – or one that is half or a third the size (and therefore weight too) – would still be a game changer.
Oxis report that its Li-S cells also achieve an excellent charge/discharge cycle lifespan, typically managing around 1,500 cycles before battery capacity falls to 80% of new. That equates to about four years of daily charging. And it thinks 2,500 cycles is possible within a few years.
Even better Li-S cells are able to discharge completely, whereas in practice Li-ion has a 80% discharge limit because they can be damaged by over-discharging. Also, Oxis cells have an indefinite shelf-life. In contrast, Li-ion batteries require a recharge every three to six months to prevent failure – something that often leads to warranty problems.
Safety is another important factor. Oxis cells meet international standards concerning shocks, crushing, thermal stability and short circuits. A ceramic lithium sulphide passivation layer and the non-flammable electrolyte cope with extreme situations, including bullet and nail penetration. Li-S is also a greener solution, because the sulphur replaces heavy metals such as nickel and cobalt.
StoreDot
In 2014, at Microsoft’s Think Next symposium in Tel Aviv, the Israelibased StoreDot company demonstrated a prototype fast-charge smartphone battery. The claim was that its new FlashBattery could be fully recharged in just 30 seconds.
It sounds amazing, so what’s the secret? It’s all down to an innovative nano-technology: ‘nanodots’ formed from bio-organic peptides. Abundant in nature, these bio-organic peptides can also self-assemble, simplifying battery cell construction and lowering manufacturing costs.
Inside a cell, these peptide nanodots react with the lithium cathode to form a multi function electrode (MFE), essentially a supersized capacitor. Capacitors are well known for their fast charging capabilities, but the problem is they discharge quickly too. But the StoreDot FlashBattery has a slow discharge rate, on a par with a lithium-ion battery.
Battery engineers typically try to optimise a specific function: faster charging, increased capacity or extended battery life. Amazingly, StoreDot’s solution improves all three. FlashBattery recharge speeds are 100 times faster than a typical 2000mAh mobile device battery. And StoreDot say it’s good for 2,000 charge/discharge cycles, which is many times more than a typical Li-ion battery.
Safety is improved too. The lithium and organic compounds are encased in a multi-layer protection structure that prevents overvoltage and heating during high-current charging. And these material leave a minimal environmental footprint, in contrast to other batteries that contain toxic, polluting heavy metals.
StoreDot believes its technology can be scaled up for fast-charging electric vehicles. Many others, including organisations like Samsung Ventures, share this optimism and have contributed tens of millions of dollars in research funding.
An electric vehicle battery would consist of 7,000 interconnected StoreDot cells. The target is to fully recharge it in just five minutes, which isn’t much longer than it takes to fill up a vehicle’s fuel tank with petrol or diesel. Yet a single charge should be good for 300 miles (480 kilometres) for the typical family car.
Of course, before these electric vehicles become a commonplace sight, there has to be significant investment in a national network of rapid-charging stations, just as Tesla is doing in the US to boost its own electric vehicles sales.
Lithium-air
On paper, the rechargeable lithium-air battery looks to be another promising technology for next-generation energy storage. The aim is to take in regular air to fuel the chemical reaction, although so far the process relies on pure oxygen. Nevertheless, it does make for a particularly lightweight battery.
Perhaps the most promising lithium-air battery attribute is its energy density, which is very close to petrol in terms of energy-per-kg. For electric vehicles this kind of energy density means a single battery charge would be enough to go from London to Edinburgh.
In practice, there are a number of hurdles to overcome, with energy loss, lengthy charge times and low charge/discharge cycle counts being some of the biggest lithium-air shortcomings.
However, a recent scientific paper from a group at the University of Cambridge highlighted a new cell design, which uses a spongy graphene oxide electrode and a novel chemical reaction using lithium iodide. Lab experiments using this setup are encouraging. Energy efficiency now peaks at around 93%, and the battery can be recharged thousands of times without any noticeable change to efficiency levels.
Unfortunately, at present, the long charge times issue has still to be addressed, as does the ability to run on regular air rather than pure oxygen.
Aluminium-ion
A team at Stanford University, led by Professor Hongjie Dai, believe new cell materials are the best way to overcome lithium-ion battery limitations. The materials they’ve selected are aluminium for the anode and graphite for the cathode.
Right from the start, there are big benefits. Both materials are readily available, cheap to buy and easier to manage from an environmental perspective. And these materials eliminate the heatinduced fire hazard of a lithium-ion cell. In fact, Prof. Hongjie Dai said, “Our new battery won’t catch fire, even if you drill through it.”
But that’s not all. The resulting battery is actually bendable, thanks to the ionic liquid electrolyte being enclosed inside a flexible polymer-coated pouch. This makes it perfect for wearable devices like smartwatches and curved smartphones.
It already sounds good, but the icing on the cake is its performance. Aluminium-ion batteries have ultra-fast charging capabilities, down to just a few minutes, and they last too. The Stanford battery withstood more than 7,500 charge/discharge cycles without any loss of capacity.
The only fly in the ointment is that these cells only generate around 2V of electricity. While this is on a par with a 1.5V AA or AAA battery cell, it’s only around half the typical lithium-ion cell power output. However, Prof. Hongjie Dai thinks improving the cathode material should eventually increase the voltage and energy density.
Coming Soon?
Of course, it’s easy to be sceptical. We hear about innovations every day, but often years go by before anything changes. What can we realistically expect this year?
Huawei’s tiny, battery-embedded smart chips are expected to appear in devices at some point in 2016. And if that’s true, we can be sure other manufacturers won’t be far behind. Microsoft, Apple and other big players would love to launch products with rapid charging capabilities. Apple makes it own batteries these days, so maybe we’ll see Huawei-like smart-charging chips in one or more of the forthcoming Phone 7 models.
StoreDot originally hoped to have some of its technology out in the marketplace by the end of 2015. That didn’t happen, but it still has high hopes that StoreDot-enhanced products will begin to appear in 2016.
Aluminium-ion battery technology is tantalisingly close but probably still a few years away. However, lithium-air batteries are a long way from becoming an everyday reality; even a 2020 introduction seems overly optimistic without a sudden and, as yet, unforeseen breakthrough.
The Race Is On
As the world becomes ever more reliant on advanced mobile technology, a new generation of rechargeable batteries is long overdue. An innovation leap would make everything from wearable electronics to electric cars a far more attractive and realistic proposition.
And there’s plenty of money to be made. The market for advanced and post lithium-ion batteries is worth many billions of dollars, with some analysts suggesting a figure of around $10 billion by 2020. Whoever puts a breakthrough battery technology into consumer’s hands first can look forward to big profits.
Meanwhile, for all of us, a fast-charging, long-life, safe battery can’t come soon enough.
Li-ion Limitations
Li-ion batteries have a limited number of charge/discharge cycles. Another frustration is that there’s some variability between cell longevity depending on where they were manufactured. In practice, this limits the usable lifespan of a typical mobile phone battery to a few years.
Lifespan is also affected by temperature. Elevated temperatures hasten storage capacity loss, as does poor internal ventilation. And smartphone, tablet and laptop design problems can lead to heat buildups. Extended recharge times is one way to keep cell temperatures under control.
Prolonged storage periods, which cause the cells to overdischarge, also reduce battery life. Electrolytic efficiency degrades due to unwanted side reactions – something that can occasionally lead to internal short-circuits.
More alarmingly, excess heat and side reactions can lead to a fire or even an explosion. That’s a nasty enough problem for smartphone or laptop owners, but it’s a potentially fatal one for road vehicles and aircraft. Numerically speaking, the risk is very low, far less than one-in-a-million. Yet billions of Li-ion batteries are produced each year, plus electric vehicles or aircraft frequently use batteries with hundreds of individual cells.
So Li-ion batteries need to have built-in safety technology to protect against fires and explosions. These include shut-down separators for overheating, tear-away tabs and vents for internal pressure release and thermal interrupts for overcharging.