Synthesis of olivine NaMnPO4 single crystals and electrochemical performance as anode material for Li-ion batteries

The direct synthesis of metastable olivine phase NaMnPO4 still remains a challenge. In this study, single crystals of the olivine NaMnPO4 were synthesized for the first time by a facile hydrothermal reaction. Single-crystal X-ray diffraction analysis provides precise structure information on the olivine structure of NaMnPO4. Moreover, the olivine NaMnPO4 can be completely transformed to its maricite phase after heating at 600 ​°C under Ar atmosphere, confirming the metastable nature of the olivine phase. Electrochemical performance of the olivine NaMnPO4 as anode material for Li-ion batteries (LIBs) was characterized. It delivers a capacity of 645.0 mAh g−1 ​at 0.1 ​A ​g−1 after 200 cycles. In contrast, the maricite phase NaMnPO4 exhibits very low lithium storage capacity.