Researchers from Virginia Commonwealth University are working towards improving safety and conductivity in lithium-ion batteries, which are employed for powering many electronic devices all over the world, including iPods, satellites, artificial hearts, laptops and cell phones.
Instability in lithium-ion batteries from liquid-state electrolytes that enable charges to be carried from one battery electrode to another is considered to be one hazard scientists can avoid, said Puru Jena, Ph.D., an eminent professor in the Department of Physics in the College of Humanities and Sciences. In spite of this instability, liquid-state electrolytes are commonplace in lithium-ion batteries because of their conductive superiority over solid-state electrolytes that are more stable.
Theoretical studies by Jena and colleague Hong Fang, a postdoctoral fellow in the Department of Physics, demonstrate the possibility of designing solid-state electrolytes not only to be as conductive as their liquid counterparts but also extremely stable. Their findings, which were featured in the Proceedings of the National Academy of Sciences this month, could lead to more powerful and safer lithium-ion batteries.
Theoretically, you can have your cake and eat it too, when it comes to the stability and conductivity.
Puru Jena, professor in the Department of Physics in the College of Humanities and Sciences, Virginia Commonwealth University
Electrolytes, which are essential for a battery, are salts made up of negative and positive ions. Positive ions are atoms that comprise of more protons than electrons, while negative ions inversely comprise of more electrons than protons.
In a lithium-ion battery, positive lithium ions pass between electrodes using electrolytes. Lithium ions are capable of flowing freely via liquid-state electrolytes but are less mobile in a solid-state electrolyte, which negatively affects conductivity.
The researchers enhanced the conductivity in solid-state electrolytes in order to produce a computational model in which one negative ion is removed. Negative cluster ions, referring to groups of atoms with more electrons than protons, replace the absent ion.
The scientists conceptualized a twist on a particular solid-state electrolyte earlier tested by other researchers. The electrolyte, which originally belongs to a family of crystals known as antiperovskites, comprised of positive ions made up of one oxygen atom and three lithium atoms. The positive ions were attached with a single chlorine atom that was a negative ion.
The chlorine atom, in the computational model, is replaced by a negative cluster ion developed by one boron atom and four fluorine atoms fixed to the existing positive ions.
In order to potentially improve conductivity, other combinations of negative cluster ions were identified.
Replacing the chlorine ion with cluster ions improves conductivity because these ions are larger and allow the lithium ions to move quickly, as if they were in a liquid.
Jena and Fang are presently in search of collaborators for testing their computational model in a laboratory setting for eventual lithium-ion battery applications.