Smallest Battery

To better read the anode's characteristics, the tiny rechargeable, lithium-based battery was formed inside a transmission electron microscope TEM at the Center for Integrated Nanotechnologies CINT, a Department of Life studies facility jointly operated by Sandia and Los Alamos local laboratories. Says Huang regarding the work, reported within the Dec. 10 issue regarding the journal Science, This experiment enables us to read the charging and discharging of a battery in real time and at atomic scale resolution, thus enlarging our understanding regarding the fundamental mechanisms by which batteries work. Because nanowire-based fabrics in lithium ion batteries for example dell Latitude D510 battery, dell Inspiron 5100 battery, dell 6T473 battery, release the potential for significant improvements in force and life density over bulk electrodes, more stringent investigations of their operating properties should improve new generations of plug-in hybrid electric vehicles, laptops and cell phones. What motivated our work, says Huang, is that lithium ion batteries [LIB] have very important applications, but the little life and force densities of current LIBs cannot meet the demand.

To improve performance, we wanted to understand LIBs from the bottom up, and we thought in-situ TEM should bring new insights to problem. Battery studies groups do use nanomaterials as anodes, but in bulk rather than individually -- a process, Huang says, that resembles receiving note of at a forest and trying to understand the behavior of an lone tree. The tiny battery created by Huang and co-workers consists of a lone tin oxide nanowire anode 100 nanometers in diameter and 10 micrometers long, a bulk lithium cobalt oxide cathode 3 millimeters long, and an ionic liquid electrolyte. The device offers the ability to directly observe change in atomic structure during charging and discharging regarding the lone trees. An unexpected locate regarding the researchers was that the tin oxide nanowire rod nearly doubles in length during charging -- distant higher than its diameter increases -- an information that should help stay away from brief circuits that shall shorten battery life.

Manufacturers should take account of this elongation in their battery design, Huang said. The common belief of workers within the field was that batteries swell throughout their diameter, not longitudinally. Huang's team located this flaw by following the progression regarding the lithium ions as they venture along the nanowire and make what researchers christened the Medusa front -- an region where high density of mobile dislocations cause the nanowire to bend and wiggle as the front progresses. The web of dislocations is caused by lithium penetration regarding the crystalline lattice. These observations prove that nanowires can sustain large stress and gt;10 GPa induced by lithiation without breaking, indicating that nanowires are very good candidates for battery electrodes, spoke about Huang.

Our observations -- which initially surprised us -- tell battery researchers how these dislocations are generated, how they evolve during charging, and release guidance in how to mitigate them, Huang said. This is the closest view to what is happening during charging of a battery that researcher have achieved so far. Lithiation-induced volume expansion, plasticity and pulverization of electrode fabrics are the primary mechanical defects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, Huang said. So our observations of structural kinetics and amorphization [the change from normal crystalline structure] have important implications for high-energy battery creation and in mitigating battery failure. The electronic noise position generated from the researchers' measurement system was too high to view electrical currents, but Sandia co-author Paul Sullivan estimated a current position of a picoampere flowing within the nanowire during charging and discharging.

The nanowire was charged to a potential of about 3. A picoampere is a millionth of a microampere. A microampere is a millionth of an ampere. The reason that atomic-scale examination regarding the charging and discharging process of a lone nanowire had not been likely was due to the fact that the high vacuum in a TEM created it difficult to use a liquid electrolyte. Component regarding the Huang group's achievement was to demonstrate that a low-vapor-pressure ionic liquid -- essentially, molten pepper -- should function within the vacuum environment.

Although the work was carried out creating use of tin oxide SnO2 nanowires, the experiments shall be extended to other fabrics systems, neither for cathode or anode studies, Huang said. The methodology that we developed should stimulate extensive real-time studies regarding the microscopic processes in batteries and lead to a more done understanding regarding the mechanisms governing battery performance and reliability, he said. Our experiments also lay a foundation for in-situ studies of electrochemical reactions, and shall have broad impact in life storage, corrosion, electrodeposition and general chemical synthesis studies field. Other researchers contributing to this work with Xiao Hua Liu, Nicholas Hudak, Arunkumar Subramanian and Hong You Fan, all of Sandia; Li Zhong, Scott Mao and Li Qiang Zhang regarding the University of Pittsburgh; Chong Min Wang and Wu Xu of Pacific Northwest Local Laboratory; and Liang Qi, Akihiro Kushima and Ju Li regarding the University of Pennsylvania. Funding came from Sandia's Science department Directed Studies and development Office and the Department of Energy's Office of Science through the Center for Integrated Nanotechnologies and the Life Frontier Studies Centers program.