K3V(PO4)2/C: a New Cathode Material for Advanced Potassium-ion Batteries

Intensive efforts are needed to find an alternative to replace Li-ion batteries. Among the potential candidates, K- ions batteries (KIBs) have received a lot of interest thanks to the low reduction potential and low cost of potassium due to the high abundance and broad distribution of potassium sources. In this regard, the development of high performance cathode materials has raised some challenges. Phosphate-based materials are considered as the most promising cathode materials for KIBs owing to their high structural stability upon cycling, high ionic conductivity and high insertion potential. Here, K3V(PO4)2 (KVP) and K3V(PO4)2/C composites are reported as new cathode
materials for KIBs with a high theoretical capacity (150 mAh.g− 1) and a high working potential (3.5–4 V). The pristine KVP and KVP/C composite materials are obtained by spray-drying process. The influence of grinding process on the structural, morphological and the electrochemical properties is investigated. The composite with carbon
nanotubes (KVP/20CNT) demonstrates the best reversible capacity of 101 mAh.g− 1 at C/ 40 using 0.8 M KPF6 in PC +10 wt% FEC as electrolyte. Different characterization techniques are combined to investigate the structural and morphological properties of the materials such as XRD, SEM, TEM and Laser granulometry.
Potassium (K) is a highly abundant element, distributed homogeneously on earth and much cheaper than lithium with similar reduction potential, thus K-ion batteries (KIBs), for similar specific capacity, are expected to deliver higher energy density than Na-ion batteries (NIBs) with no difference compared to Li-ion batteries (LIBs). Phosphate-based materials are considered as the most promising cathode materials for KIBs due to their high structural stability upon cycling, high insertion potential and good ionic conductivity. However, these materials exhibit low intrinsic electronic conductivity. In this work, we study K3V(PO4)2 (KVP) and KVP/C, obtained by spray drying, that combines a high working potential of 3.5-4V and a high theoretical capacity of 150 mAh.g-1 (for 2 K+). To solve the issue related to the electronic conductivity in KVP, conductive carbon allotropes (carbon nanotubes (CNT) and reduced graphene oxide (rGO)) were added before the spray-drying process. The influence of grinding step carbon addition on electrochemical properties is investigated by different characterization techniques such as XRD, SEM, TEM. The electrochemical performance are investigated by EIS and galvanostatic cycling. The KVP/20CNT composite material exhibit the best reversible capacity at 101mAh/g.
Reference : J. Bodart et al, Journal of Power Sources 480 (2020) 229057