Increasing battery’s storage capacity could allow laptops, electric vehicles to run longer
The lithium-ion batteries that power our laptops and electric vehicles could store more energy and run longer on a single charge with the help of a sponge-like silicon material.
Pacific Northwest National Laboratory
PNNL researchers have developed a porous, sponge-like nanomaterial made of silicon (shown here under a microscope) that could help lithium-ion batteries run longer on a single charge by giving the batteries' electrodes the space they need to expand without breaking.
Researchers developed the porous material to replace the graphite traditionally used in one of the battery’s electrodes, as silicon has more than 10 times the energy storage capacity of graphite. A paper describing the material’s performance as a lithium-ion battery electrode was published today in Nature Communications.
“Silicon has long been sought as a way to improve the performance of lithium-ion batteries, but silicon swells so much when it is charged that it can break apart, making a silicon electrode inoperable,” said Pacific Northwest National Laboratory Fellow Ji-Guang “Jason” Zhang. “The porous, sponge-like material we’ve developed gives silicon the room it needs to expand without breaking.”
Room for improvement
Rechargeable lithium-ion batteries have two electrodes: one that’s positively charged and made of lithium and another that’s negative and typically consists of graphite. Electricity is generated when electrons flow through a wire that connects the two. To control the electrons, positively charged lithium atoms – which scientists call ions - shuffle from one electrode to the other through another path: the electrolyte solution in which the electrodes sit.
The chemistry of lithium-ion batteries limits how much energy they can store. To increase the battery’s energy capacity, researchers are looking at new materials such as silicon. A lithium-ion battery with a silicon electrode could last about 30 percent longer than one with a graphite electrode. Today’s average electric vehicle could drive about 130 miles on a single charge if it used a lithium-ion battery with PNNL’s silicon electrode.
Unfortunately, silicon expands as much as three times in size when it charges, creating pressure within the material that causes it to break. Many scientists have attempted to make tiny, nano-sized battery components with the idea that the smaller size would give silicon enough room to expand, but these efforts haven’t produced market-ready technologies.
A sponge solution
Zhang and his PNNL colleagues wondered if a sponge-like silicon electrode would do the trick. Others had etched pores into a silicon electrode’s surface, but hadn’t succeeded in creating holes throughout the material. So they approached Michael Sailor, a University of California, San Diego chemist whose research includes using porous silicon to detect pollutants and deliver drugs, for help. PNNL used Sailor’s method to create porous silicon – placing thin sheets in a chemical bath to etch out tiny holes throughout the material – and then coated the result with a thin layer of conductive carbon to make their electrodes.
Next, the team collaborated with materials scientist Chongmin Wang, who specializes in using in-situ transmission electron microscopes at DOE’s EMSL, the Environmental Molecular Sciences Laboratory at PNNL. Wang uses powerful microscopes to record close-up videos of tiny batteries, allowing researchers to better understand the physical and chemical changes that batteries undergo as they operate. Wang put the team’s sponge-like, carbon-coated silicon electrode through a series of charges and discharges under the microscope’s careful eye.
Space to grow
The team observed that while being charged, the new electrode mostly expanded into the empty spaces created by the material’s porous structure. The outside shape of the electrode only expanded by 30 percent – much less than the 300 percent usually seen in silicon electrodes. And the new electrode didn’t break down. After more than 1,000 charge-and-discharge cycles, the electrode maintained more than 80 percent of its initial energy storage capacity.
Next, Zhang and his colleagues plan to develop a larger prototype battery with their silicon sponge electrode. Part of that effort will involve creating a more streamlined production process so their new electrode can be made at a reasonable cost.
This research was funded by the Department of Energy's Office of Energy Efficiency and Renewable Energy.
REFERENCE: Xiaolin Li, Meng Gu, Shenyang Hu, Rhiannon Kennard, Pengfei Yan, Xilin Chen, Chongmin Wang, Michael J. Sailor, Ji-Guang Zhang and Jun Liu, “Mesoporous Silicon Sponge as an Anti-Pulverization Structure for High-Performance Lithium-Ion Battery Anodes,” Nature Communications, July 8, 2014, DOI: 10.1038/ncomms5105, http://www.nature.com/ncomms/2014/140708/ncomms5105/full/ncomms5105.html.
Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,300 staff and has an annual budget of about $950 million. It is managed by Battelle for the U.S. Department of Energy’s Office of Science. As the single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information on PNNL, visit the PNNL News Center, or follow PNNL on Facebook, Google+, LinkedIn and Twitter.
EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science. Located at Pacific Northwest National Laboratory in Richland, Wash., EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. Its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies. Follow EMSL on Facebook, LinkedIn and Twitter.
Franny White | newswise
Trojan Transit Rolling Out
27.03.2015 | University of Arkansas at Little Rock
Ultra-Thin Silicon Films Create Vibrant Optical Colors
25.03.2015 | University of Alabama Huntsville
In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...
The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.
As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...
When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.
The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe.
Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...
Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.
From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...
25.03.2015 | Event News
19.03.2015 | Event News
17.03.2015 | Event News
27.03.2015 | Agricultural and Forestry Science
27.03.2015 | Materials Sciences
27.03.2015 | Ecology, The Environment and Conservation