The Rise of Nanotechnology in Modern Lithium-ion Powered Devices

With the plethora of electronic devices being used today, the problem of battery conservation is a hot topic. People have become extremely reliant on their electronics, particularly their mobile phones. Mobile devices are easy to carry around, but charging them when they run out of battery is not always very convenient. Especially for people that move around every day for work or school, it is often difficult to find a reliable power source. Even for those that are at home all day, a short battery life can be disadvantageous. As a result, companies always work towards extending the battery life of their electronic products. It is also an important piece of information that consumers always look out for when purchasing electronics.

Many innovative advancements have already been made towards creating better and more efficient batteries. Cell phones use lithium ion batteries, so it is important to focus on improving them. Recently, a Silicon Valley-based tech company called Amprius developed a new lithium-ion battery that stores 20% more energy than batteries that are currently on the market. Amprius has already started shipping these batteries to smartphone companies, and has also secured $30 million to develop the next wave of batteries that could potentially store 50% more energy than existing batteries.

The lithium-ion batteries developed by Amprius have a silicon anode instead of the standard graphite material. Silicon anodes open new doors in terms of energy density; only four lithium ions are needed to bond with a silicon ion, while six carbon atoms are required to bond to a lithium ion. Unfortunately, creation of silicon-based batteries is currently difficult because the silicon expands and contracts from lithium ion flow with every charge/discharge cycle, thereby destroying the anode very quickly. To get around this, Amprius has developed a carbon-coated silicon nanoparticle cathode (diagram on right). Although this silicon-carbon cathode does not have the energy density that pure silicon has, but it still significantly improves battery life and can be produced with existing equipment, which is a big concern in the tech industry. These batteries will retain 80% of their charge after 500 cycles, which is more than sufficient for mobile devices.

At the Lawrence Berkeley National Laboratory, researchers have developed a new lithium/sulfur cell that boasts better energy storage, power, recharge speed, and survivability. Li/S batteries have high energy capacity because two electrons are produced every time the battery’s chemical reaction occurs.

A basic Li/S battery cell contains a lithium anode, a carbon-sulfur cathode, and an electrolyte that lets lithium ions pass through. The discharge reaction converts lithium metal in the anode into Li2S at the cathode. The flow of the two lithium ions is balanced by the flow of two electrons between the battery contacts, which deliver double the current of those in a typical lithium-ion battery.

However, there are also many issues involved in the chemistry of lithium/sulfur batteries. When the sulfur in the cathode absorbs lithium ions, the Li2S has double the volume of the original sulfur. This creates mechanical stress and deterioration, reduces electrical contact between the carbon and the sulfur, and prevents lithium ions from flowing to the surface. In addition, lithium and sulfur generally do not directly form Li2S, and require a series of intermediate species.

In response to these problems, the Lawrence Berkeley research team has developed a sulfur-graphene oxide nanocomposite cathode that is held together with an elastic polymer binder. Thin flakes of graphene oxide are coated with a layer of sulfur a few nanometers in thickness, and then a layer of protective surfactant. The electrolyte was also modified to produce an overall balanced combination that has the features for efficient Li/S cell operation.

There are a large variety of possibilities in the field of lithium ion battery improvement. Research has already produced very efficient models, such as combinations with silicon and sulfur. Lithium ion batteries are the future, and they will only get better.

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