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Georgia Tech Power Cell Among Top 10 Physical Science Breakthroughs in 2012

Source: Georgia Tech News Service

A power cell that directly converts mechanical energy to chemical energy – which can then be stored and converted to electrical energy – has been selected as one of 2012’s top breakthroughs in the physical sciences by Physics World magazine.

Figure 1. Structure design of a self-charging power cell by hybridizing a piezoelectric nanogenerator and a Li-ion battery. (a) Schematic diagram showing the design and structure of the self-charging power cell. The anode is aligned TiO2 nanotube arrays that are directly grown on Ti foils; a layer of polarized PVDF film performs as the separator; the cathode is a LiCoO2 mixture on aluminum foil. This structure is sealed in stainless-steel 2016-coin-type cells, as shown in the inset. (b) Sticking a power cell on the bottom of a shoe, the compressive energy generated by walking can be converted and stored directly by SCPC. (c) Cross-sectional SEM image of the self-charging power cell, which is composed of aligned nanotubes as anode, piezoelectric polymer film as separator and cathode. (d) Enlarged view of the aligned TiO2 nanotubes. The inset is a top view SEM image of the nanotubes.

The cell, developed at the Georgia Institute of Technology by Professor Zhong Lin Wang and his research team, was first reported in the journal Nano Letters on August 9, 2012. By eliminating the need to convert mechanical energy to electrical energy for charging a battery, the new hybrid generator-storage cell utilizes mechanical energy more efficiently than systems using separate generators and batteries.

At the heart of the self-charging power cell is a piezoelectric membrane that drives lithium ions from one side of the cell to the other when the membrane is deformed by mechanical stress. The lithium ions driven through the polarized membrane by the piezoelectric potential are directly stored as chemical energy using an electrochemical process.

By harnessing a compressive force, such as a shoe heel hitting the pavement from a person walking, the power cell generates enough current to power a small calculator. A hybrid power cell the size of a conventional coin battery could power small electronic devices – and could have military applications for soldiers who might one day recharge battery-powered equipment as they walked, said Wang, who is a Regents Professor in the School of Materials Science and Engineering.

The Physics World team selected the project from more than 350 news articles about advances in the physical sciences published on in 2012. The criteria for judging included:

  • Fundamental importance of research
  • Significant advance in knowledge
  • Strong connection between theory and experiment
  • General interest to all physicists

The original Physics World article on the power cell can be read at the link below. The work is published in NanoLetters at