The newest generation of lithium-ion batteries now under development promises a revolution in powering cell phones, electric vehicles, laptops and myriad other devices. Featuring all solid-state, nonflammable components, the new batteries are lighter, hold their charge longer, recharge faster and are safer to use than conventional lithium-ion batteries, which contain a gel that can catch on fire.
However, like all batteries, solid-state lithium-ion batteries have a drawback: Due to electro-chemical interactions, impedance--the AC analog of DC electrical resistance--can build up within the batteries, limiting the flow of electric current. Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have now pinpointed the location where most of this buildup occurs. In so doing, the team has suggested a simple redesign that could dramatically limit the buildup of impedance, enabling the batteries to fulfill their role as the next-generation power source.
A lithium-ion battery consists of two sheetlike terminals, the anode (negative terminal) and the cathode (positive terminal), separated by an ion-conducting medium called the electrolyte. (The electrolyte is a gel in the case of ordinary lithium-ion batteries, a solid in the solid-state version.) During discharging, lithium ions flow from the anode through the electrolyte to the cathode, forcing electrons to move around an outside circuit and generate the electric current that powers devices.
Measuring the Impedance of a Solid-State Lithium-Ion Battery
A solid-state lithium-ion battery is composed of an anode, a cathode, and a solid electrolyte separating the two. Rapidly cycling (repeatedly charging and discharging) a lithium-ion battery limits the battery's performance over time by significantly increasing the battery's internal impedance (its time-dependent resistance), which hinders the flow of current. NIST researchers, in collaboration with Sandia National Laboratories, have combined two complementary techniques – contact potential difference measurements and neutron dep ..
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