27-Apr-2017: Safer alternative to lithium-ion batteries

Scientists have demonstrated a breakthrough for nickel-zinc (Ni-Zn) batteries in which a three-dimensional (3-D) Zn "sponge" replaces the powdered zinc anode traditionally used. With 3-D Zn, the battery provides an energy content and rechargeability that rival lithium-ion batteries while avoiding the safety issues that continue to plague lithium.

The 3-D sponge form factor allows us to reimagine zinc, a well-known battery material, for the 21st century.

Zinc-based batteries are the go-to global battery for single-use applications, but are not considered rechargeable in practice due to their tendency to grow conductive whiskers (dendrites) inside the battery, which can grow long enough to cause short circuits.

The key to realizing rechargeable zinc-based batteries lies in controlling the behavior of the zinc during cycling. Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites.

With the benefits of rechargeability, the 3-D Zn sponge is ready to be deployed within the entire family of Zn-based alkaline batteries across the civilian and military sectors. It offers an energy-relevant alternative, from drop-in replacements for lithium-ion to new opportunities in portable and wearable power, and manned and unmanned electric vehicles while reducing safety hazards, easing transportation restrictions, and using earth-abundant materials.

7-Feb-2017: E-pills that can monitor patient health under development

MIT scientists have developed a small battery that runs on stomach acids and could power next-generation ingestible electronic pills which may monitor patient health or treat diseases by residing in the gastrointestinal tract for extended periods of time. The device may offer a safer and lower-cost alternative to the traditional batteries now used to power such devices.

Researchers have previously built and tested many ingestible devices that can be used to sense physiological conditions such as temperature, heart rate, and breathing rate, or to deliver drugs to treat diseases such as malaria.

This work could lead to a new generation of electronic ingestible pills that could someday enable novel ways of monitoring patient health and/or treating disease. Such devices are usually powered by small batteries, but conventional batteries self-discharge over time and pose a possible safety risk.

Researchers took inspiration from a very simple type of voltaic cell known as a lemon battery, which consists of two electrodes - often a galvanized nail and a copper penny - stuck in a lemon. The citric acid in the lemon carries a small electric current between the two electrodes. To replicate that strategy, the researchers attached zinc and copper electrodes to the surface of their ingestible sensor. The zinc emits ions into the acid in the stomach to power the voltaic circuit, generating enough energy to power a commercial temperature sensor and a 900-megahertz transmitter.

In tests in pigs, the devices took an average of six days to travel through the digestive tract. While in the stomach, the voltaic cell produced enough energy to power a temperature sensor and to wirelessly transmit the data to a base station located two metres away, with a signal sent every 12 seconds. Once the device moved into the small intestine, which is less acidic than the stomach, the cell generated only about a hundredth of what it produced in the stomach. But there's still power there, which you could harvest over a longer period of time and use to transmit less frequent packets of information.

The current prototype of the device is a cylinder about 40 millimetres long and 12 millimetres in diameter, but the researchers anticipate that they could make the capsule about one-third that size.