Super Batteries Made from Recycled Glass

Researchers are developing a high capacity silicon-based battery with minimal external expansion.

(Image courtesy of the author.)

(Image courtesy of the author.)

Our rapidly growing population and everyday activities are putting considerable pressure on the Earth, exploiting resources faster than they naturally replenish. Climate change is the most obvious example of this problem. However, there are many ways to reduce the load we’re placing on the planet, and waste recycling is a major one.

Glass can be completely recycled with no quality loss. It is made from sand and other supplements (soda ash, limestone, etc.), meaning the material must be heated to 1400-1600C, which requires a huge source of energy.

According to the U.S. Energy Information Administration, natural gas is the most common heat source (73 percent), followed by electrical energy (24 percent). Yet despite the upfront costs, recycling processes generally save energy by reducing emissions and raw material consumption.

(Image courtesy of the author.)

(Image courtesy of the author.)

As a solution to both our ever-increasing energy needs and the need to deal with glass waste, researchers at the University of California Riverside have developed a battery based on the silicon that results from recycling glass. This is a very efficient way of glass recycling as well an important advancement in small, high-capacity batteries.

The most common batteries, lithium-ion, have a wide range applications, from small electronic devices to electric vehicles. These batteries are usually made of lithium cathodes and graphite anodes. The graphite anode works well because of its resistance to expansion during the charging-discharging process.

During the charging process, the battery is heated and gasses are released inside during electrolyte decomposition, which inflates the battery, potentially causing safety and battery performance issues. Most electronic devices are not designed to allow large battery volume expansion (usually the battery volume expansion tolerance is, at most, five percent).

The disadvantage of carbon as an anode is its low energy density (370 mAh/g), which makes it less than ideal for storage.

The increasing energy requirements of electronic devices and electrical vehicles imposes demands for higher capacities and energy densities in the batteries, which is why silicon is becoming a popular material for battery researchers. It has very high capacity (4200 mAh/g), basically, the highest energy density value compared to all other materials.

Battery researchers are focusing on silicon because it has great potential for designing a super battery. Moreover, it’s inexpensive and easily available, obtainable in a green way by recycling glass garbage.

Unfortunately, silicon is not a perfect magic material; it has its own disadvantages.

During the battery charging process, silicon reacts with lithium creating the composite SiLix. The result of this process is a significant structural change where the Si expands by 300-400 percent and causes Li-ion batteries to swell. This causes the mechanical stress and silicon structure pulverization, which are associated with electrolyte interface. This process usually leads to battery failure, and is the reason silicon batteries do not have long lifecycles.

iPhone 3G with a swollen battery. (Image courtesy of the author.)

iPhone 3G with a swollen battery. (Image courtesy of the author.)

Electrical devices increasingly require batteries with higher energy densities (capacities), but also minimum external dimension change.

Silicon’s huge energy density value could lead to a new generation of high capacity batteries, but this means solving the material’s expansion during the charging process is critically important. Extending the lifecycle of this battery type is the main challenge for the researchers.

One of the most recent battery designs utilizes a nano-architecture silicon diode. In this design, silicon nanowires (at a length of a few microns) are mixed with graphene and carbon nanotubes. Test results of this solution show that there is a less contact between the lithium and electrode, result in higher stability which, in turn, prevented the expansion.

The second possible solution is to use a composite of silicon and metal. Metal does not react with Lithium and makes a matrix which decreases the volume expansion. Using the new binders—such as alginic acid (AA), polyamide-imide (PAI) and polyimide (PI)…)—which can provide more volume expansion, is a potential solution.

Still, the best and fastest short-term solution is a combination of silicon material which has great energy density with graphitic carbon, which has good physical and chemical performance. This solution does not offer as high a capacity as silicon alone, but has a significantly longer life cycle than  pure silicon anode batteries.

(Image courtesy of the author.)

(Image courtesy of the author.)

The battery solution created by UC Riverside has great potential because it brings us a high-capacity battery using green technology. This approach is promising because it is expected that the battery capacity will be increased by 40-60 percent (according to research from the University of Waterloo), allowing electric cars to drive up to 310 miles per charge, for example.

Edis was born in Sarajevo (Bosnia and Herzegovina). He has an MSc. in Electrical Engineering, Power Engineering department. He works in an international company based in Stockholm (Sweden) as a power transformer testing expert and has visited many countries all over the world. He also has extensive experience in project management, science research and writing technical papers, testing power transformers and researching new test methods, developing and designing new test equipment, etc. In his free time, he likes to grow plants and enjoys long walks in the countryside.