Abstract
Due to the abundance and low cost of sodium-containing precursors ambient temperature sodium ionbatteries are promising for large scale grid storage. The low melting point of Na (97.7 °C) compared to180.6 C for Li represents a significant safety hazard for the use of Na metal anodes at ambienttemperatures, which emphasizes the need for scientists and engineers to identify, design and developnew negative electrodes for Na-ion batteries. The identification of a suitable negative electrode is acrucial challenge for any further successful development of new cells, and to date efficient andcompetitive negative electrodes for NaB are still very rare. In this work we demonstrate that NiP3 couldbe a good challenger for this purpose. NiP3 based electrodes are evaluated as negative electrodematerials for Li-ion batteries (LiB) and Na-ion batteries (NaB). The study of the reaction mechanismreveals the formation of a phase of composition close to Li3P and Na3P embedding Ni nanoparticles asthe final reaction product after a full discharge. While the direct conversion of NiP3 into Na3P is identifiedfor the reaction versus Na, it is still unclear whether an amorphous phase exists during the first dischargefor the reaction versus Li before the conversion. Furthermore, thanks to the carboxymethyl cellulose/carbon black (CMC/CB) electrode formulation, the NiP3 electrode possesses a very promising capacitywith a reversible storage capacity higher than 1000 mA h g-1 after 50 cycles for LiB and 900 mA h g-1after 15 cycles for NaB, which represents one of the highest capacities ever sustained in Na-ion batteries.