The lithium-ion battery has had 90% of the engineering efficiency of which it is capable already optimized. The only thing left to do with it are dangerous options which often result in fire or explosion.
Fortunately, on the near horizon are nonflammable alternatives that are just entering their optimization stage, giving mobile devices a stable future once the consumer device makers switch from investing in more dangerous Li-ion optimization to optimizing the nonflammable alternatives.
When the separation between the anode and cathode of a traditional lithium-ion (Li-ion) battery are breeched (here with a drill) the flammable electrolyte explodes its package and burns with a visible fire.
When a non-flammable ionic liquid electrolyte, such as Nohm’s NanoLyte shown here, is substituted for the ordinary lithium salt dissolved in an organic solvent, the battery does not explode or burn even when the anode and cathode are breeched.
Just as lithium-ion (Li-ion) replaced nickel metal hydride (NiMH) before it and nickel cadmium (NiCd) before that, silver zinc (AgZn) batteries are on track to replace Li-ion too, according to a McGraw-Hill forecast as far back as 2010. Since then silver zinc has been perfected and are on the market for rechargeable hearing-aid “button” batteries by ZPower LL (Camarillo, Calif.) They are nonflammable and could provide up to 40 percent more run time than lithium-ion batteries. SOURCE: ZPower
Yet another Li-ion successor battery is being developed by SolidEnergy Systems using a solid electrolyte design similar to that being developed by Dyson, General Motors and Khosla Ventures when they purchase University of Michigan spin-off Sakti3. The SolidEnergy Systems next-generation Li-ion battery uses an “anode-free” lithium metal battery with dual-layer electrolytes and an ultra-thin lithium metal anode, which both companies claim is safer than today’s Li-ion. SOURCE: Solid Energy Systems
Some analysts, however, aren’t sure about the imminence of a switch.
“Lithium-ion will be with us for a while,” said Martin Reynolds, vice president at Gartner Inc. “The real issue is the amount of energy that the battery contains. If something goes wrong, the battery delivers all that energy in just a few seconds — so you get a fire. The problem is compounded by the electrolyte. In Li-ion, the electrolyte is flammable, and evaporates quickly — a bit like alcohol. So a Li-ion failure may also involve hot organic vapor, combusting in air to release more energy than the battery has in electricity. Many other technologies are water-based, and the water inhibits any tendency to fire. Silver-zinc, for example, uses a water based electrolyte. But it today does not compete with Li-ion in typical applications.”
Li-ion is very developed in several key areas: long lasting cycles (so your phone battery is not dead after three months; good capacity retention (so it is still functional after two years), fast charge (30 to 60 minutes; low cost; and are generally safe) — excluding a few meltdowns for those who over-optimize their designs, such as making the interior electrolyte barrier too thin or flimsy.
An enormous variety of sodium-ion battery variations are being considered by researchers worldwide as surveyed here regarding their operation voltages versus specific capacities for cathode materials (a) and anode materials (b) in order to find a combination that make them competitive with Li-ion. SOURCE: Macmillan Publishers Ltd.
“Any new technology will have to have all the advantages of Li-ion, but will still likely be dangerous, simply because of its capacity and energy delivery,” Reynolds told EE Times. “We do see plenty of lab developments. Some of these go to better Li batteries. Others are at the very beginning of their life cycle, and will take years to turn to production. So, although we see lots of new technologies in the lab, they have a long way to go to beat lithium-ion. Lastly, the continued demand for battery capacity to drive new features means that manufacturers are pushing for ever thinner separators and electrodes inside batteries. The thinner they are, the more likelihood of failure.”
Today’s zinc-oxide battery prototypes have lower energy densities than Li-ion, as well as the lower operating cell voltages but their aqueous electrolytes are safer and with improved chemistries could offer better volumetric energy densities. SOURCE: Macmillan Publishers Ltd.
Some of the most promising alternatives are illustrated in this slideshow, including ionic liquids designed to merely replace the flammable electrolyte in existing Li-ion batteries. Ionic liquid electrolytes are also called ionic melts, ionic fluids, fused salts, liquid salts, and ionic glasses. The most common these is table salt — sodium chloride (NaCl) — which melts at 1,474°F, but there are many alternative salts that melt as low as 68°F.
NEC is developing an organic radical battery (ORB) that is environmentally friendly since they use organic radical polymers instead of metals to provide electricity. ORBs may become a high-power alternative to the Li-ion battery within five years. SOURCE: NEC
The high-temperature ionic salts are being developed for grid-sized batteries, but the low-temperature versions are being adapted to mobile applications, thus making them nonflammable, according to chief technology officer (CTO) Surya Moganty, at Nohms Technologies. Ionic salts produce no flammable by-products and basically all they need to be successful is the engineering optimizations necessary to make them outperform Li-ion. Sumitomo, for instance, has a salt-based battery that is molten at 142°F, which they claim requires half the space of Li-ion batteries.
The Nickel-Lithium battery has a non-flammable electrolyte called LISBON (LIthium Super Ionic CONductor, Li2+2xZn1-xGeO4) which can store up to 3.5-times the energy per pound of today’s Li-ion batteries, but requires a large investment to be developed into a replacement for Li-ion. SOURCE: Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
Even Gartner’s Reynolds is a fan of ionic liquids. “A non-flammable electrolyte would be a big help,” he said. “It would absorb energy needed to evaporate it, rather than turning it into a flammable gas. You might still end up with a glowing red mass, but you would not have flame jets.”
Aluminium-ion batteries work like lithium-ion batteries, just using an inexpensive aluminum anode instead of an expensive lithium anode. The down side is that the theoretical maximum voltage for an aluminum-ion battery is 2.65 volts compared to four volts for lithium-ion batteries. However, on the up side the theoretical energy density of aluminum-ion batteries is 1060 Wh/kg, over twice as much as lithium-ion batteries at 406 Wh/kg (aluminium ions have three valence electrons while lithium-ions only have one). SOURCE: Stanford
The fuel cell industry already exceeds $1 billion with an annual growth rate in double digits, but most are for stationary installations since cost-of-usage in this application is only about 10 cents per kilowatt-hour. Unfortunately, they have been abandoned for vehicle-sized applications mainly because of the non-feasibility of switching to a hydrogen infrastructure when gasoline is so cheap (despite the fuel-cell powered vehicle shown here) and in 2016 were ditched by Samsung in favor of more profitable Li-ion battery optimization.
Beyond ionic liquids is a vast variety of alternatives, some nearing maturity and some just getting started. A few we left out because of their limited applications, such as the Aqueous Hybrid Ion (AHI) battery from Aquion Energy which is primarily for grid-sized applications. For safer Li-ion substitutes for mobile applications check out the slideshow to see just the highlights of what is available now and promised in the future.
By R. Colin Johnson