Abstract
Polyanionic compounds form an important class of materials for positive electrodes for Na-ion batteries (NIBs). This chapter gives the structural frameworks of some typical polyanionic materials. It highlights the recent achievements in the development of new electrode materials for NIBs. Solid state reaction and wet method are two traditional synthesis routes for Na Super Ionic CONductor (NASICON) compounds. NASICON-type materials constitute an important family of polyanionic compounds. They also hold an essential role as solid electrolytes and electrode materials for both lithium-ion batteries and NIBs. Na3V2(PO4)3 and Na3V2(PO4)2F3 are two of the most promising polyanionic materials that can be used at the positive electrode in NIBs and they indeed belong to two different families of materials.