The growing demands for large-scale energy storage devices have put a spotlight on aqueous sodium-ion batteries, which possess a number of highly desirable features, such as sodium abundance, low cost and safety over organic electrolytes. While lots of cathode materials were reported, only few candidate materials like active carbon and NaTi₂(PO₄)₃ were proposed as anodes. It is a long-standing common knowledge that the low cost, non-toxicity, and highly reversible FePO₄·2H₂O is known as an attractive cathode material for non-aqueous lithium- and sodium-ion batteries, but we demonstrate for the first time that nano-size non-carbon coated amorphous FePO₄·2H₂O can be used as the anode for an aqueous sodium-ion battery. Its optimum operating voltage (∼2.75 V vs. Na⁺/Na) avoids hydrogen evolution. The capacity is as high as 80 mAh/g at a rate of 0.5 C in a three-electrode system. The full cell, using the Na_0.44MnO₂ as cathode, maintained 90% of the capacity at 300 cycles at a rate of 3 C. The calculations also show that its volume change during the intercalation of Na ions is below 2%. Its low cost, high safety, along with its outstanding electrochemical performance makes amorphous FePO₄·2H₂O a promising anode material for aqueous sodium-ion batteries.

对大型能量存储设备的不断增长的需求已将注意力放在含水钠离子电池上，这些钠离子电池具有许多非常理想的功能，例如钠的丰度，低成本和相对于有机电解质的安全性。尽管报道了许多阴极材料，但仅提出了几种候选材料，例如活性炭和NaTi ₂（PO ₄）₃作为阳极。长期以来，众所周知，低成本，无毒且高度可逆的FePO ₄ ·2H ₂ O被认为是用于非水锂和钠离子电池的有吸引力的正极材料，但我们证明了这一点。纳米非碳包覆的非晶态FePO ₄ ·2H _2的首次研究O可用作钠离子水溶液电池的阳极。它的最佳工作电压（相对于Na ⁺ / Na约为2.75 V ）可避免氢气析出。在三电极系统中，容量以0.5 C的速度高达80 mAh / g。使用Na _0.44 MnO ₂作为阴极的完整电池，在300次循环中以3 C的速率保持90％的容量。计算还表明，在插入Na离子期间其体积变化低于2％。它的低成本，高安全性以及出色的电化学性能使无定形FePO ₄ ·2H ₂ O成为水性钠离子电池的有前途的负极材料。