Cr-LiF as a high energy density conversion-type cathode for Li-ion solid-state batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Transition-metal fluorides (TMFs) are explored as lithium-ion battery cathodes, with iron-based systems being prominent.
• Common TMF cathodes face challenges like slow kinetics and electrolyte issues.

Purpose of the Study:

• To investigate chromium (Cr) as a novel transition metal for TMF cathodes in rechargeable lithium batteries.
• To address limitations of existing TMF cathodes using a thin-film solid-state platform.

Main Methods:

• Coevaporation of chromium and lithium fluoride (LiF) to create heterogeneous Cr-LiF thin films.
• Electrochemical cycling, capacity, and energy density measurements.
• First-principles calculations to identify the delithiated phase.

Main Results:

• Cr-LiF thin films achieved an initial capacity of 435 mAh/g and energy density of 0.71 Wh/g at C/10.
• CrF2 identified as the dominant delithiated phase.
• Sustained capacity of 208 mAh/g at 1C and 5C after 1500 cycles, outperforming Fe-LiF analogs in rate capability.

Conclusions:

• Chromium fluorides represent a new class of high-energy conversion cathodes for batteries.
• The thin-film solid-state approach effectively mitigates TMF cathode shortcomings.
• Cr-LiF expands the range of viable positive electrode materials for advanced battery technologies.