If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



The Great Unplugging

Hunger for mobility energizes the battery business, drives efforts to develop longer lasting batteries

by Ivan Amato
February 13, 2006 | A version of this story appeared in Volume 84, Issue 7

Credit: Photo by Ivan Amato
Credit: Photo by Ivan Amato

With relentless rollouts of portable gadgets, an onslaught of marketers peddling mobility, and an ever-growing demand for 24-7 connectivity to the infosphere, more and more technology-dependent citizens have been maligning wires and their plugs as outrageous tethers on personal freedom and as efficiency-dragging throwbacks to earlier days of electrical technology.

It's not just the laptop computer and iPod crowd that's been unplugged. On Jan. 10 at the International Builders' Show in Orlando, Fla., for example, toolmaker DeWalt of Towson, Md., announced that by summertime it would begin shipping a new line of 36-V lithium-ion-battery-powered tools, including heavy-duty cordless saws and sanders for construction sites. The company claims these new tools are as powerful as those plugged into the electrical grid. "It's time to pull the plug ... on cords," a manly, disembodied voice beams on the company's website.

The technocultural trend of getting rid of plugs brings with it, by necessity, a widespread addiction to portable power-that is, batteries. In the absence of these glamour-free, electrochemical contraptions with 18th-century roots, after all, today's beeping, blinking, wirelessly connected, blue-toothed, Blackberried, and ear-podded electronic gadgetry would become nothing more than extra weight.

Just how much unplugging ultimately is in store for the citizens of the world will depend heavily on how innovative battery designers can be. Trends in the battery market are providing plenty of incentive. Between 1997 and 2002, worldwide sales of batteries-both of the primary nonrechargeable sort used in flashlights and toys as well as the secondary rechargeable kind in laptop computers, cell phones, and cordless tools-edged up about $1 billion per year, from about $49 billion to $54 billion, according to estimates by the Freedonia Group, a Cleveland-based market research firm. Sales are expected to reach nearly $78 billion by 2007, tracking a much steeper projected annual growth rate since 2002 of more than $4 billion.

In its official publications, Intel looks at the flight from plugs as a sign that society is moving toward an era of "mobility ubiquity." In a bid to push that era forward and profit from it as well, Intel in August announced that it was joining forces with Japan's Matsushita Battery Industrial Co. (MBI) to develop a battery that lasts long enough for "all-day computing" on a single charge.

Mike Trainor, self-described as Intel's chief mobile technology evangelist, says MBI is working on advanced lithium-ion-battery technologies while Intel engineers focus on increasing the energy efficiency of the many other parts of a computer, including the display, chip set, and voltage regulation circuits.

The new all-day batteries and the energy-efficient computers they're designed for are on track to be on store shelves in the coming months, but they're all but destined to fall short of what consumers will expect soon after. Even though the capacity of batteries has been improving by about 8% per year recently, says Dan Doughty, manager of the Advanced Power Sources R&D Department at Sandia National Laboratories, Albuquerque, these advances haven't yielded longer battery life because, in his words, "gadget makers keep adding more bells and whistles."

The high-tech culture is one in which everyone always wants more processor power, more data storage, more connectivity, more mobility, more everything-all of which draws more battery power. It's a cycle that relegates the Intels of the world to a Sisyphean conundrum, always having to develop more power-efficient displays, chip sets, and disc drives, as well as better batteries, if they are to continue to offer more dazzling products without also undermining the product's appeal with larger and heavier batteries. "We find ourselves up against an inherent struggle between extending battery life and improving mobile performance," states an Intel report on the so-called battery-life challenge.

Credit: Courtesy of Jeff Dahn
Credit: Courtesy of Jeff Dahn

When asked to wax utopian about the future of battery technology, Jeff Dahn, a battery researcher at Dalhousie University, Halifax, Nova Scotia, described a battery so good that you would want to, in his words, "will it to your children." Dahn says: "The kind of battery you would really want is one you could recharge forever, that would be almost impossible to unintentionally damage, that would be lightweight and high-voltage, deliver high currents, and would have no self-discharge, or memory effect," which refers to the insidious degradation of battery recharging performance over time. "That's where people like me are trying to take batteries."

Many factors play into the complex and hard-to-predict dynamic that makes or breaks any given battery design. These factors include the periodic table, the mobility of charges through the battery's electrolyte, the stability of the battery's chemical constituents, environmental and toxicity issues, the relative costs of materials, and plenty of other technical and nontechnical factors. It's way too complicated to expect present-day theories and simulations of electrochemical processes and market dynamics to reveal a priori the best design.

That's why Dahn, for one, has been turning to combinatorial chemistry methods to generate large numbers of potential negative-electrode materials in a more empirical, trial-and-error approach to discovering better battery materials, such as various amorphous alloys involving silicon, aluminum, manganese, tin, carbon, and rare-earth elements.

The basic design for batteries has remained the same since scientists began building the first batteries just over 200 years ago. In general, batteries generate current when two chemical partners, one in the anode and one in the cathode, react with each other via mobile ions that move between the two electrodes through an intervening, ion-conducting electrolyte. As these reactions unfold, one of the chemical partners accepts electrons while the other releases them, but not directly to one another. Instead, the electrons leave through the anode; course through a tool, flashlight bulb, computer, or other device; and then return to the battery through the cathode.

In a typical alkaline cell, the reaction between, say, a zinc-based anode and a manganese oxide-based cathode in the presence of an alkaline electrolyte releases electrons from the anode and accepts them at the cathode, generating a current. In primary cells, the reaction is essentially irreversible, so once it is complete, the flow of electrons ceases and the battery becomes useless.

In secondary cells, such as nickel-cadmium, nickel/metal-hydride, and lithium-ion batteries, the internal electrochemical reactions are reversible. That makes the batteries rechargeable, usually by plugging them into a wall socket. In a typical lithium-ion battery, the electrochemical reaction that generates current centers on the reversible migration of lithium ions from a positive lithium cobalt oxide electrode to a graphitic or at least carbon-based electrode, where the ions intercalate between the electrodes' carbon layers.

Whether it's small-scale research, as Dahn's group does in Halifax, or large-scale operations like the multi-million-dollar collaboration of five U.S. government laboratories to develop practical, longer lasting, safer, affordable batteries for hybrid electric-gasoline cars under the Department of Energy's FreedomCAR program, the modus operandi for getting more performance out of batteries is the same. By varying the chemical composition and material properties of the electrodes, the electrolyte, various additives, and other battery components, researchers try to come up with a battery design that has some advantage over existing options, say, higher voltage, more power, reliable operation at low or high temperatures, faster recharging, or a cheaper price tag.

Even as Intel and MBI work toward their all-day lithium-ion battery, the power tool industry is revving up its decades-long march to unplug more and more of its products. Early last year, Milwaukee Electric Tool Corp. of Brookfield, Wis., began selling what it claims to be "the most powerful cordless tool system on the planet." The claim rests on a new battery system based on what the company briefly describes as "lithium manganese chemistry," a proprietary design that relies on a LiMn2O4 powder, which Milwaukee has been developing in collaboration with the Canadian branch of E-One Moli Energy, a Taiwan-based firm.

Although more expensive than the nickel/cadmium and nickel/metal-hydride batteries that have been powering cordless tools for many years, the new lithium manganese batteries have longer run times and are lighter. Those advantages enabled Milwaukee to offer 28-V systems that for many potential buyers would have been unacceptably heavy using other types of batteries.

The firm puts into the battery pack twice the energy of an 18-V nickel-cadmium battery without adding any weight, says Gary Meyer, Milwaukee's manager of concept R&D. "We are finding that our customers are weaning themselves off the cord."

In addition to cutting the plugs from more types of power tools-among them band saws, metal-cutting saws, right-angle drills, and rotary hammers-Milwaukee expects its new V28 technology to find use in home and garden tools, such as cordless lawn mowers and home appliances, and in military settings. Because of the premium costs of the new batteries, cost-conscious consumers are likely to stick with tools running on less expensive earlier generations of rechargeable batteries.

Credit: A123Systems Photo
Credit: A123Systems Photo

Not to be outdone, DeWalt, a subsidiary of Black & Decker Corp., teamed up with the start-up battery developer A123Systems in Watertown, Mass., on Project Nirvana. The goal was to develop their own lithium-ion battery capable of delivering 36 V and about 3,600 W/kg of battery. Using technology that facilitates rapid lithium-ion migration, developed by Massachusetts Institute of Technology materials scientist and company founder Yet-Ming Chiang, they met their goal in a surprisingly short three-year period.

At the core of the new "nanophosphate" battery technology are cathode materials made out of nanoscale particles of lithium iron phosphate subtly doped with metal ions, such as those of aluminum, niobium, manganese, and titanium. "We expect that our technology will have the same impact on high-power products as the introduction of the first-generation lithium-ion technology had on the development of consumer electronics in the 1990s," says David Vieau, A123System's chief executive officer and president.

One of the advantages of the new battery is that it can recharge to 90% of its capacity within even a short coffee break. A123Systems is now producing hundreds of thousands of the new batteries in factories in Asia, Vieau says. According to a DeWalt spokesperson, the company will begin shipping its new line of tools in the coming months.

Battery makers would love to see the plug-pulling trend continue to grow, but there is only so much electrical energy designers can pack into a canister. The power tool industry knew that it would have to shift from the nickel-cadmium batteries, which had made their earlier generation of 18-V cordless tools possible, when it tried selling 24-V tools with bigger and heavier nickel-cadmium batteries. These did not do well in the market, notes Christine Potter, group product manager for DeWalt. "That's when lithium-ion batteries became interesting to us." The A123Systems batteries in the company's new line of 36-V tools will weigh about the same as their 18-V nickel-cadmium predecessors.

The trend of offering more battery power at the same weight cannot go on forever, however. "What most people in the battery industry believe is that today's conventional lithium-ion-based cell is probably reaching a point of maximum optimization or maximum maturity in terms of the amount of energy you can get out of these cells," says Intel's Trainor. But as long as there's still a few more percent in performance to squeeze out of batteries each year, researchers will push on with eyes wide open.

As its practitioners well know, the art of battery making entails bottling electrochemical energy in ways that are predictable, controllable, safe, manufacturable, and environmentally sound or at least manageable. The batteries should be long lasting, small and light enough to handle, and affordable to boot. It's a mix of requirements that, when met, is, as Dahn sees it, "almost miraculous."


The Great Unplugging
Hunger for mobility energizes the battery business, drives efforts to develop longer lasting batteries

Lithium-Ion Batteries
The Marketplace Beckons For More Innovation


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.