The new iron-based mixed polyanionic material Na₂Fe(C₂O₄)(HPO₄) has been synthesized by a hydrothermal technique. The compound contains four Na sites with a three-dimensional crystal structure. This compound shows promising reversible Li and Na insertion properties as a cathode material. The redox potentials observed were ∼3.2 V (vs Li⁺/Li) for the Li-ion cell and ∼3.1 V (vs Na⁺/Na) for the Na-ion cell with Fe^2+/3+ redox reactions. The reversible electrode operation was found to deliver 71 and 104 mAh g⁻¹ specific capacities in Li and Na half cells, respectively. This present study reveals promising performance from a mixed oxalate-phosphate based polyanionic material and opens up further possibilities for materials discovery.

通过水热技术合成了新型的铁基混合聚阴离子材料Na ₂ Fe（C ₂ O ₄）（HPO ₄）。该化合物含有四个具有三维晶体结构的Na位点。该化合物作为阴极材料显示出有希望的可逆的Li和Na插入特性。对于具有Fe ^{2 + / 3 +}氧化还原反应的锂离子电池，观察到的氧化还原电势约为3.2 V（vs Li ⁺ / Li），对于钠离子电池约为3.1 V（vs Na ⁺ / Na）。发现可逆电极操作可提供71和104 mAh g ^-1锂和钠半电池的比容量。本研究揭示了基于草酸盐-磷酸盐的混合聚阴离子材料的良好性能，并为发现材料开辟了更多可能性。