Niobium Bronzoids as negative Electrodes: Synthesis, Structure and Electrochemical Properties of Li2Nb4P2O16 and Na2Nb4P2O16 Jean-Noël Chotard, Nikhil Subash, Amna Rafique, Loic Dupont, Pierre-Etienne Cabelguen, François Fauth, Christian Masquelier ChemRxiv, 2025