Abstract
Potassium titanyl phosphate (KTiOPO4) is a well-known material for nonlinear optical device applications, but its electrochemical properties are not yet well understood. This study investigates sodium and potassium storage properties of KTiOPO4 using alkali metal fluorosulfonyl amide based nonaqueous electrolytes and a higher stiffness sodium alginate binder. The prepared KTiOPO4-reduced graphene oxide (rGO) composite electrode delivers stable desodiation and depotassiation capacities of 97 and 123 mAh g–1, respectively, at 0.075 C (10 mA g–1) over 70 cycles. The potassium cells demonstrate excellent cycle stability and high rate capability performances. Operando and ex situ XRD measurements confirm the multiple structural changes by potassiation/depotassiation and the high reversibility of the phase evolution.
Highlights
Potassium ion batteries (PIBs) are considered as alternative energy storage systems to conventional Li ion batteries (LIBs).[1]
We have successfully developed a highly conductive KTiOPO4−reduced graphene oxide composite electrode that delivers a highly stable capacity of 129 mAh g−1 at 0.075 C (C/13.3) for 70 cycles in a K cell filled with KFSA and carbonate ester electrolyte and a very stable sodiation capacity of 101 mAh g−1 at 0.075 C for 70 cycles in a Na cell
The KTiOPO4−rGO composite was synthesized by a solidstate reaction
Summary
Potassium ion batteries (PIBs) are considered as alternative energy storage systems to conventional Li ion batteries (LIBs).[1]. [Fe(CN)6]), and polyanionic compounds (KVPO4F, KVOPO4,9 KFeSO4F,10 and Na3V2O2x(PO4)2F3−2x11) have been reported as positive electrode materials for PIBs.[12] Among these positive electrode materials, KTiOPO4 (KTP) structural type compounds[13] (i.e., KTiOPO4, KVPO4F, KVOPO4, KFeSO4F, and KTiPO4F) with the general formula AMXO4L [A = Li, Na, K; M = Fe, Ti, V; X = P, S, Si; L= O, F, OH] are more worthy as both positive and negative electrode materials for PIBs due to their high ionic conductivities and stable tunnel frameworks.[13]. We have successfully developed a highly conductive KTiOPO4−reduced graphene oxide (rGO) composite electrode that delivers a highly stable capacity of 129 mAh g−1 at 0.075 C (C/13.3) for 70 cycles in a K cell filled with KFSA and carbonate ester electrolyte and a very stable sodiation capacity of 101 mAh g−1 at 0.075 C for 70 cycles in a Na cell. The mechanism of potassium insertion into the KTP structure is studied by operando and ex situ X-ray diffraction (XRD) measurements
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