A Lithium-Ion Battery That Works Even When It’s on Fire

In a paper printed last month in Nano Letters, the group describe how they’ve designed a novel “fireproof” strong-state electrolyte (SSE) for use in lithium-ion batteries. “We deal with the dilemma of flammability in SSEs by adding a fire retardant,” states Jiayu Wan, a postdoctoral researcher in Cui’s lab and co-author of the paper. 

They made use of a flame-retardant substance called decabromodiphenyl ethane, or DBDPE for brief. To make their new strong-state electrolyte, the group to start with designed a slim film by combining DBDPE with polyimide, a mechanical enforcer. 

Working with polyimide has a lot of benefits, states Wan. Aside from getting “mechanically truly solid,” it boasts a large melting issue (generating it much less probably that a brief circuit will occur), a alternatives-dependent production system (that’s suitable with how batteries are manufactured right now), and it is economical (3M even has film tapes manufactured from it).

The hitch, nevertheless, is that polyimide just cannot perform ions. To get all-around this snag, Wan and his colleagues extra two different polymers, polyethylene oxide (PEO) and lithium bistrifluoromethanesulfonylimide (LiTFSI), to the combine.

“It’s innovative—they’ve neatly made use of co-polymers, which is a new way to solve the flammable polymer electrolyte battery dilemma,” states Chunsheng Wang, a researcher who scientific studies new battery systems at the University of Maryland.

Stable-state electrolytes just take two most important kinds. You can make them from ceramics, a substance that conducts ions properly but is exceptionally brittle and effects in thick batteries, which have lower electricity density. Or, you can have electrolytes composed of polymers, which are minimal price tag, light-weight, and versatile. They are also “soft,” indicating there is minimal resistance together the interface of the electrode and electrolyte, which lets the electrolyte to perform ions effortlessly.

But polymer electrolytes also have difficulties. “This softness indicates they’re not able to suppress lithium dendrite propagation, so they’re flammable,” states Wang, referring to the very small needle-like projections that grow from a battery’s anode. Dendrites can consequence following repeated cycles of charging and discharging when these lithium crystals pierce a battery’s separator, they can start fires.

“A lot of folks believe that for liquid electrolytes, there is no resistance and dendrites can grow by means of the electrolyte,” states Wang. “But if you replace the liquid with a strong, which is mechanically more robust, the lithium may perhaps be blocked.”

Their mechanical power, together with diminished flammability, are just some causes why strong-state electrolytes have garnered interest among the researchers in both academia and sector. A 3rd rationale lies with the reality that they enable batteries to be stacked. “Because the electrolyte does not stream, you can effortlessly put them together without the need of wires… which is crucial for growing electricity density,” states Wang.

There’s no perfect choice, while. “All the different SSEs have some challenges, so you have to balance them out,” he states.

It is a objective that the group at Stanford would seem a single action closer to reaching. Not only is their new strong-state electrolyte ultrathin (measuring between 10 to 25 micrometers), it also provides a large precise capability (131 milliampere hrs for each gram, mAh/g, at 1 diploma C), and demonstrates good biking functionality (long lasting 300 cycles at sixty degrees C). Crucially, prototype battery cells manufactured working with it proved to do the job even with catching fire (in this online video, an LED stays lit even while the battery powering it is on fire).

“This was pretty astonishing to us,” states Stanford’s Wan. “Usually a battery will just explode with a fire. But with this a single, not only does it not explode, it even now features.” 

Currently, the group carries on to take a look at new resources and constructions for use in strong-state electrolytes, with the intention of improving latest density and cell capability. Says Wan: “The obstacle now is to make the battery cost a lot quicker, have a better electricity density, and to last extended.”