A new technology that reduces the internal resistance of solid-state lithium-ion batteries, and thereby improves charge-discharge performance, has been developed by researchers from Hitachi and Tohoku University’s Advanced Institute for Material Research.
The new technology utilizes LiBH4-based complex hydrides as novel solid electrolytes in order to achieve the performance improvements — and, as a result, the batteries can successfully operate at temperatures as high as 150° Celsius while maintaining a discharge capacity of 90% of max capacity.
As a result of this all, the possibility is there to now use lithium-ion batteries (solid-state designs, to be more particular) in applications where high temperatures are a possible issue. And, probably more importantly, the possibility is there to begin using lithium-ion batteries without a cooling system (which are commonly required to keep performance up and degradation down).
Hitachi argues that this will allow for designs that are more compact, and also an overall reduction in costs.
Green Car Congress provides more information on the specifics of the new battery design:
Composite positive electrode layer to suppress the decomposition of active materials at interface. One potential issue is that Li-ion conductivity will be inhibited by the decomposition of the cathode material, which is reduced by LiBH4-based complex hydrides. To solve this issue, a Li-B-Ti-O-based oxide material was developed to form a dense composite positive electrode with the active materials. The Li-B-Ti-O in the electrode effectively protected the active materials, and suppressed the increment of internal resistance caused by the decomposition. In consequence, the discharge capacity of the battery was improved from 0 to 50% of theoretical value.
Adhesive layer for reducing the interface resistance between solid electrolyte and composite positive electrode layer. Another issue is that the composite cathode material and the metal hydride complex solid electrolyte layer were delaminated due to the volume change of the active materials during charge-discharge reaction. This causes incremental interfacial resistance by poor lithium ion conduction at the delaminated interface. To prevent delamination of the interface, the team developed an amide-added metal hydride complex with a low melting point for use as an adhesive layer.
As a result, the internal resistance of the all-solid-state Li-ion battery was successfully reduced to 1/100 of the value compared to that of a battery with no adhesive layer.
The researchers behind the work are now aiming to further improve capacity, energy density, and charge-discharge performance.