Brushing thin films on the electrodes preserves the batteries

A little brushing may be the secret to making better rechargeable lithium batteries.

The Rice University lab of chemist James Tour has introduced a technique to tune the surface of battery anodes by simply applying powders to them. The powder adheres to the anode and becomes a thin lithium coating which effectively prevents the formation of harmful dendrites.

Scanning electron microscope images show a sequence of lithium sheets processed by Rice University scientists. Brushing metal powder into the lithium anodes of rechargeable batteries can quench the formation of damaging dendrites. Scale bars represent 100 microns. Courtesy of the tour group

Ground phosphorus-sulfur powder on the surface of metallic lithium foil has demonstrated that its surface energy can be tuned without the need for toxic solvents. Anodes modified in this way and associated with lithium-iron-phosphate-oxide cathodes in test cells showed that they retained 70% more capacity after 340 charge-discharge cycles than standard batteries.

The study appears in Advanced Materials.

“This would simplify the manufacture of high-capacity batteries while significantly improving them,” Tour said. “Grinding these powdered solids into a lithium metal anode dramatically reduces the formation of dendrites that can short out a battery, as well as accelerated material consumption.”

According to Rice University scientists, brushing metal powders on the surface of lithium anodes shows promise in reducing the threat of dendrites that damage recyclable batteries.  Courtesy of the tour group
According to Rice University scientists, brushing metal powders on the surface of lithium anodes shows promise in reducing the threat of dendrites that damage recyclable batteries. Courtesy of the tour group

Weiyin Chen, lead author and graduate student at Rice, and his lab colleagues applied the elbow grease needed to test a variety of candidate powders on their electrodes. They first brushed the surface to give it texture, then powder brushed to create the thin film that reacts with the lithium metal and forms a strong passivation layer.

Chen and co-author Rodrigo Salvatierra, a former postdoctoral researcher and now academic visitor in the Tour’s lab, built test batteries and determined that the treated anodes retained ultra-low bias — another damaging characteristic for lithium batteries. ion – for over 4,000 hours, approximately eight times longer than bare lithium anodes.

Tour said the powders effectively tune the surface energy of the electrodes, allowing for more uniform behavior across the material.

“This provides a metal composite surface that prevents lithium metal loss from the anode, a common problem in lithium metal batteries,” Tour said. “Lithium metal batteries far exceed the capacity of traditional lithium-ion batteries, but lithium metal is often difficult to recharge repeatedly.”

Rice University scientists have found that brushing powdered phosphorus and sulfur into lithium anodes prevents them from forming harmful dendrites in rechargeable batteries.  From left to right: James Tour, Weiyin Chen and Rodrigo Salvatierra.
From left to right: James Tour, Weiyin Chen and Rodrigo Salvatierra.

“The powder on the surface of lithium metal produces an artificial passivation layer that improves stability throughout charge-discharge cycles,” Chen said. “Using this method of brushing, the metal surface is stabilized so that it can be recharged safely.”

To show that the technique may have wider application, the lab also ground powder into a sodium electrode and found that the process greatly stabilized its voltage surge.

The study aligns with Tour and Rice mechanical engineer C. Fred Higgs III’s recent discovery that sanding certain powders onto surfaces can make them superhydrophobic or highly water resistant.

The co-authors of the article are Rice alumni John Li and Duy Luong; graduate students Jacob Beckham, Nghi La and Jianan Xu, and visiting scholar Victor Li. Tour is the TT and WF Chao Professor of Chemistry as well as a professor of Computer Science and Materials Science and Nano-Engineering at Rice.

The Air Force Office of Scientific Research (FA9550-19-1-0296) supported the research.

Peer-reviewed research

Brushed metals for rechargeable metal batteries: https://onlinelibrary.wiley.com/doi/10.1002/adma.202202668

Pictures to download

According to Rice University scientists, brushing metal powders on the surface of lithium anodes shows promise in reducing the threat of dendrites that damage recyclable batteries.  (Credit: Tour Group/Rice University)

According to Rice University scientists, brushing metal powders on the surface of lithium anodes shows promise in reducing the threat of dendrites that damage recyclable batteries. (Credit: Tour Group/Rice University)

A multi-step process without toxic solvents that adds a lithium film to the anodes of lithium-ion batteries promises to prevent the formation of harmful dendrites, according to Rice University scientists.  (Credit: Tour Group/Rice University)

A multi-step process without toxic solvents that adds a lithium film to the anodes of lithium-ion batteries promises to prevent the formation of harmful dendrites, according to Rice University scientists. (Credit: Tour Group/Rice University)

Scanning electron microscope images show a sequence of lithium sheets processed by Rice University scientists.  Brushing metal powder into the lithium anodes of rechargeable batteries can quench the formation of damaging dendrites.  Scale bars represent 100 microns.  (Credit: Tour Group/Rice University)

Scanning electron microscope images show a sequence of lithium sheets processed by Rice University scientists. Brushing metal powder into the lithium anodes of rechargeable batteries can quench the formation of damaging dendrites. Scale bars represent 100 microns. (Credit: Tour Group/Rice University)

Rice University scientists have found that brushing powdered phosphorus and sulfur into lithium anodes prevents them from forming harmful dendrites in rechargeable batteries.  From left to right: James Tour, Weiyin Chen and Rodrigo Salvatierra.  (Credit: Rice University)

Rice University scientists have found that brushing powdered phosphorus and sulfur into lithium anodes prevents them from forming harmful dendrites in rechargeable batteries. From left to right: James Tour, Weiyin Chen and Rodrigo Salvatierra. (Credit: Rice University)