Super‐Reversible CuF<sub>2</sub> Cathodes Enabled by Cu<sup>2+</sup>‐Coordinated Alginate
Jiale Xia, Zeyi Wang, Nuwanthi D. Rodrig, Bo Nan, Jiaxun Zhang, Weiran Zhang, Brett L. Lucht, Chongyin Yang, Chunsheng Wang
Abstract
Abstract Copper fluoride (CuF 2 ) has the highest energy density among all metal fluoride cathodes owing to its high theoretical potential (3.55 V) and high capacity (528 mAh g −1 ). However, CuF 2 can only survive for less than five cycles, mainly due to serious Cu‐ion dissolution during charge/discharge cycles. Herein, copper dissolution is successfully suppressed by forming Cu 2+ ‐coordinated sodium alginate (Cu‐SA) on the surface of CuF 2 particles during the electrode fabrication process, by using water as a slurry solvent and sodium alginate (SA) as a binder. The trace dissolved Cu 2+ in water from CuF 2 can in situ cross‐link with SA binder forming a conformal Cu‐SA layer on CuF 2 surface. After water evaporation during the electrode dry process, the Cu‐SA layer is Li‐ion conductor but Cu 2+ insulator, which can effectively suppress the dissolution of Cu‐ions in the organic 4 m LiClO 4 /ethylene carbonate/propylene carbonate electrolyte, enhancing the reversibility of CuF 2 . CuF 2 electrode with SA binder delivers a reversible capacity of 420.4 mAh g ‐1 after 50 cycles at 0.05 C, reaching an energy density of 1009.1 Wh kg ‐1 . Cu 2+ cross‐link polymer coating on CuF 2 opens the door for stabilizing the high‐energy and low‐cost CuF 2 cathode for next‐generation Li‐ion batteries.