Self-charging battery gets boost from nanocomposite film

Feb 24, 2014 by Lisa Zyga feature
(a-c) The PVDF-PZT nanocomposite film acts as the piezoseparator in a self-charging power cell. (d) Photograph of the PVDF-PZT film. (e) Sticking a self-charging power cell underneath the button of a calculator, the mechanical energy generated by pressing the button can be converted and directly stored by the cell. Credit: Zhang, et al. ©2014 IOP Publishing Ltd

(Phys.org) —In 2012, a research team at the Georgia Institute of Technology led by Professor Zhong Lin Wang fabricated the first self-charging power pack, or battery, that can be charged without being plugged into a wall socket or other source of electricity. Instead, the battery is charged by applying a mechanical stress, which causes lithium ions to migrate from the cathode to the anode due to the piezoelectric effect. Now the researchers have improved the battery by adding nanoparticles to the battery's piezoelectric material, resulting in a higher charging efficiency and storage capacity.

Along with Wang, Yan Zhang and their other coauthors from Lanzhou University, Northeastern University in Shenyang, and the Chinese Academy of Sciences in Beijing (all in China), and the Georgia Institute of Technology, have published a paper on the improved self-charging battery in a recent issue of Nanotechnology.

The self-charging battery is several hundred micrometers thick and fits inside a stainless steel coin-type cell. By placing it underneath the buttons of a calculator, for instance, the mechanical energy generated by pressing a button can be simultaneously converted from mechanical to chemical energy and stored in the battery. The researchers envision that the battery could one day power a variety of small, portable electronic devices.

"Self-charging power cells charged up by mechanical deformation and vibration from the environment have possible applications for self-powered sensor systems, as well as flexible and portable electronics, such as self-charging flexible mobile phones and human health monitoring systems," Zhang told Phys.org.

The self-charging battery's ability to both convert and store energy is what sets it apart from conventional batteries, whose sole purpose is to store energy. In conventional batteries, the first step of energy conversion (such as mechanical to electrical) is almost always performed by a separate device. The self-charging battery completely bypasses the intermediate step of converting to electricity, resulting in a more efficient conversion and storage process than if two separate devices—and two steps—were used.

Piezopotential distribution of a self-charging power cell (a) without and (b) with an external compressive stress, which converts mechanical energy to chemical energy for direct storage. Credit: Zhang, et al. ©2014 IOP Publishing Ltd

To transform a conventional Li-ion battery into a self-charging one, the researchers replaced the polyethylene separator that normally separates the two electrodes in a Li-ion battery with a that generates a charge when under an applied stress. In the 2012 version, this material was a PVDF film. In the new study, the researchers added lead zirconate titanate (PZT) nanoparticles to the PVDF film to create a nanocomposite.

The addition of the PZT results in significant performance improvements, namely increasing the 's efficiency and storage capacity by 2.5 times over the earlier version. Specifically, the improved from 0.004 to 0.010 µA h.

The researchers explained that these improvements occur due to two mechanisms: first, the PZT induces a geometrical strain confinement effect that increases the piezoelectric potential; and second, the PZT has a porous structure that increases the number of pores in the nancomposite, resulting in a smaller interpore distance that increases the number of ionic conduction paths on which lithium ions can travel. Both mechanisms allow more lithium ions to migrate from the cathode to the anode, increasing the total charge.

The improvements demonstrate that a nanocomposite film can enhance the performance of self-charging batteries, and the researchers plan to make further improvements in the future.

"We need to deeply understand the exact progress of charging electrochemical reactions at the two electrodes, for improving the performance of the self-charging power cells," Zhang said.

Explore further: Inexpensive material boosts battery capacity

More information: Yan Zhang, et al. "PVDF-PZT nanocomposite film based self-charging power cell." Nanotechnology 25 (2014) 105401 (7pp). DOI: 10.1088/0957-4484/25/10/105401

add to favorites email to friend print save as pdf

Related Stories

Self-charging battery both generates and stores energy

Aug 17, 2012

(Phys.org) -- Renewable energy technologies generally consist of two distinct processes: energy generation (using sources such as coal, solar, wind, etc.) and energy storage (such as batteries). These two ...

Inexpensive material boosts battery capacity

Oct 23, 2013

Battery-powered cars offer many environmental benefits, but a car with a full tank of gasoline can travel further. By improving the energy capacity of lithium-ion batteries, a new electrode made from iron ...

Researchers make breakthrough in battery technology

Feb 11, 2014

Researchers at the Materials and Surface Science Institute (MSSI), University of Limerick have made a significant breakthrough in the area of rechargeable battery technology. There is an ever-increasing demand ...

Battery development may extend range of electric cars

Jan 09, 2014

It's known that electric vehicles could travel longer distances before needing to charge and more renewable energy could be saved for a rainy day if lithium-sulfur batteries can just overcome a few technical ...

Recommended for you

Image: Testing electric propulsion

Aug 20, 2014

On Aug. 19, National Aviation Day, a lot of people are reflecting on how far aviation has come in the last century. Could this be the future – a plane with many electric motors that can hover like a helicopter ...

Where's the real value in Tesla's patent pledge?

Aug 20, 2014

With the much-anticipated arrival next month of electric vehicle manufacturer Tesla's Model S to Australian shores, it's a good time to revisit Tesla's pledge to freely share patents. ...

New type of solar concentrator doesn't block the view

Aug 19, 2014

(Phys.org) —A team of researchers at Michigan State University has developed a new type of solar concentrator that when placed over a window creates solar energy while allowing people to actually see through ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

mohitnigam_iit
1 / 5 (3) Feb 24, 2014
alfie_null
not rated yet Feb 25, 2014
Size wasn't mentioned, but the stated capacity is something like seven orders of magnitude less than a typical lithium coin cell.