The biggest weakness of all-solid-state batteries is their slow charging and discharging speeds. Japanese researchers have found a way to decrease the electrical resistance between the electrode and electrolyte, greatly increasing the rate at which a battery transports electrical energy, an article in Nanowerk reported.
The new batteries were devised by a joint effort of Tokyo Institute of Technology (Tokyo Tech) and Tohoku University (TU). A study published in the journal ACS Applied Materials & Interfaces covered the details of the prototype storage devices.
The researchers reported that their all-solid-state batteries exceeded the performance of both traditional dry cells and lithium-ion batteries. They believe that their newly-developed energy storage device could kick off big changes in the portable electronics industry.
Lithium-ion batteries have solid electrodes and either liquid or polymer electrolytes. They have improved over the years until they attained ubiquity as the premier power source for electronic devices.
The technology has pretty much reached the peak of its performance. Engineers and researchers are looking for successors that can store more energy and release it at a faster rate. (Related: Revolutionary battery can self-assemble and charge your phone in SECONDS.)
Reducing the (electrical) resistance of all-solid-state batteries
All-solid-state batteries are one of the replacements for lithium-ion batteries. They are an evolution of their predecessor, swapping out the liquid or polymer electrolyte of their predecessor for its fully solid equivalent.
Tests showed that these batteries are demonstrably safer than the older generation. They have superior stability and can store higher densities of energy.
Unlike lithium-ion batteries, the solid-state batteries suffer from significant electrical resistance within the interface that connects their solid electrode and equally solid electrolyte. The resistance is attributed in part to impurities in the materials.
Because their electrons travel slowly between their parts, the batteries charge or recharge at a slower rate. Sold-state batteries are less efficient for powering advanced electronics.
The Tokyo Tech-TU research team turned to an lithium-nitrogen-magnesium-oxygen (LNMO) alloy with very low interface resistance. They built several all-solid-state batteries in ultra-high vacuum conditions to ensure the absence of impurities responsible for high electrical resistance.
They tested the electrochemical properties of the newly-fabricated batteries in the same vacuum environment. X-ray diffraction and spectroscopy techniques were used to evaluate the crystalline structure of the thin films of each battery. Their target were lithium-ions distributed around the interface.
New solid-state batteries charge and recharge faster than lithium-ion equivalents
In their study, the researchers reported that lithium ions abruptly migrated from the LiPO4 layer to the LNMO layer during electrical discharges. The transferred lithium ions proceeded to turn half of the LNMO at the electrode-electrolyte interface into L2NMO.
The exact opposite happens when the battery starts recharging. The converted L2NMO sheds the lithium ion and goes back to being LNMO. The now-excess lithium returns to the Li3PO4 interface.
Researchers reported that the resistance of this solid interface is a couple of orders of magnitude lower than all preceding all-solid-state batteries that used LNMO material. The new batteries even outperform lithium-ion batteries that use liquid electrolytes.
The greatly reduced electrical resistance increased the charging and discharging speeds of the experimental batteries. It only took a second to either fill a battery to half-capacity or empty it of a similar amount of stored energy.
Fast charging and recharging rates normally increase the wear and tear on batteries. However, the new all-solid-state batteries maintained their performance despite undergoing 100 cycles of charging and discharging.
The researchers concluded their study with the hope that their new batteries will one day provide power to a new generation of electronic devices and electric vehicles.
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