Today's scientists are using advanced material science to push the design capabilities of batteries, resulting in the discovery of unimaginable applications while also overcoming some of industry's greatest technological barriers, such as capacity fading, charge/discharge time, storage capacity, weight, material cost, and infrastructure deployment. The lithium-ion battery has been the cornerstone of the secondary cell design due to its ability to hold a charge when not in use and also for its high energy-to-weight ratio;1 therefore, it is no surprise that a lot of the current research has been focused on further developing this design.
Current Design
The basic battery consists of three items: a cathode material (the positive end), an anode material (the negative end), and an electrolyte material, which is a liquid that allows ions to move from the anode to the cathode—this nonreversible process will continue until the stored charge is exhausted. This basic three-piece design is known as a primary cell and has been vastly improved upon over the years. In fact, look for a new and improved version of primary cell batteries this summer under the name Oxyride that guarantees to make the time between changes even longer.2 A large portion of today's batteries, however, can be discharged and then recharged for additional use. These types of batteries are called secondary cells (see Table 1 for list of primary and secondary cells).
Table 1: List of Primary and Secondary Cells
| Primary Cells | Secondary Cells |
|---|---|
| Alkaline battery | Lead-acid battery |
| Aluminium battery | Lithium-ion battery |
| Chromic acid cell | Lithium-iron phosphate battery |
| Lithium battery | Lithium-sulfur battery |
| Mercury battery | Lithium-titanate battery |
| Nickel-oxyhydroxide battery | Nickel-cadmium battery |
| Silver-oxide battery | Nickel-hydrogen battery |
| Zinc-air battery | Nickel-iron battery |
| Zinc-carbon battery | Low self-discharge NiMH battery |
| Oxyride battery | Nickel-zinc battery |
| Sodium-sulfur battery | |
| Zinc-bromine battery |
Advances in Materials
Overcoming Capacity Fading
Some of the most promising material science research attempts to add silicon to the anode side of the lithium-ion battery. This has the potential to increase the battery's storage capacity by a factor of 10 while reducing the time it takes to recharge.3 The downside, however, is silicon's inability to maintain its structure during the charge/discharge cycles—it expands to four times its original size during the charging process. Therefore, as the battery cycles back and forth between charging and discharging, the silicon breaks down and fractures. This degradation leads to capacity fading, or the battery's inability to hold a charge.
One way to overcome capacity fading and to increase the number of times the battery can be charged/discharged is to bond silicon to another substrate material, such as titanium or carbon. A group of Boston College chemists, using silicon-coated titanium nanonets, were successful in achieving an increase in storage capacity of 1,000 milliamps-hour per gram (mA-h/g) while keeping an average of 0.1% capacity fade per cycle between the 20th and the 100th cycles.4 While still being developed, scientists believe that this type of research will lead to greatly expanded future applications.
Moving Beyond the Internal Battery
Other battery designers have focused more on the weight issue created when a large amount of energy is required, such as for vehicles. The advancement of carbon fiber materials has allowed scientists to develop a strong, lightweight, moldable material that can store and discharge electricity without the need of a chemical process. This breakthrough is thought to potentially turn the outer casing of hand-held items into batteries themselves, thereby eliminating internal batteries altogether. Further, hybrid or electric vehicles could gain an added capacity for electrical energy while also maintaining a lighter yet durable design.5 This design helps to break the mold of what batteries are thought to look like, as well as how they are made.
Bending the Rules with Nanotechnology
Material scientists, familiar with existing battery materials, are also turning to new tools that they hope will unlock new designs. For example, through the use of advances in nanotechnology, scientists have been able to create a battery with a stroke of a brush—literally. By using carbon nanotubes and silver nanowires, scientists at Stanford University have designed an "ink" that will turn paper into bendable batteries and super capacitors. The charge/discharge cycles are thought to be an order of magnitude greater than lithium-ion batteries, which are limited to around 1,200 cycles. The high surface-to-volume ratio of the nanomaterials allows for a quick transfer of electricity, and the uses range from industrial energy storage to hybrid vehicles.6
Going Organic
Even more impressive breakthroughs are questioning traditional battery materials. New advances in polymer science have led to flexible, razor-thin batteries made of plastic and organic compounds. Using a redox-active organic polymer film approximately 200 nanometers thick, scientists are able to create a high charge/discharge capacity battery, which means it can charge much more quickly than conventional batteries and can more quickly discharge a larger amount of energy. Uses for this design include pocket-sized integrated circuit cards used for memory storage and microprocessing.7
Taking Charge
Finally, with all of the emerging technology breakthroughs and advances in materials, some scientists have turned their research toward battery delivery systems. While it may be convenient to purchase batteries for your remote control at the drug store, the same is not true for vehicles that need a new charge between destinations. German chemists at Fraunhofer Institute for Chemical Technology ICT in Pfinztal have developed a new type of redox flow battery that would allow people to change the battery's discharged electrolyte fluid for a recharged fluid—much like refilling a gas tank. The battery uses two fluid electrolytes containing metal ions that flow through porous graphite felt electrodes, separated by a membrane that allows protons to pass through. This type of delivery system could work well with existing infrastructure, and even more excitingly, the discharged electrolyte fluid could be recharged at the deposit station via clean energy provided by wind turbines or solar plants for the next user.8
Closing
The use of advanced materials has allowed scientists to blur the lines between what was and what will be. While some research is more promising than others, it stands to reason that traditional battery design will be forever changed. All of these designs push the boundaries of how people think of batteries, but more importantly, they are leading to expanding possibilities that will revolutionize the battery industry and the various industries that batteries serve.
Endnotes
1 http://www.pcworld.com/article/188624/lithiumion_battery_life_could_reach_20_years.html
2 http://www.sciencedaily.com/videos/2005/0606-longerlasting_battery.htm
3 http://www.nature.com/nnano/journal/v3/n1/full/nnano.2007.411.html
4 http://www.sciencedaily.com/releases/2010/02/100216101157.htm
5 http://www.sciencedaily.com/releases/2010/02/100205115808.htm
6 http://www.sciencedaily.com/releases/2009/12/091207165035.htm
7 http://www.sciencedaily.com/releases/2007/03/070323141052.htm
