高稳定性水系锌离子电池正极材料MnO2@MgO的制备与性能

Preparation and Performance of High Stability Cathode Material MnO2@MgO for Aqueous Zinc-Ion Battery

采用共沉淀法和热分解法合成了具有核壳结构的MnO2@MgO微球。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等手段对材料进行表征,结果发现包覆MgO不改变MnO2的结构,包覆层由纳米颗粒组成,厚度约为50 nm。电化学性能结果显示,包覆后材料的放电比容量明显提高,在100 mA·g^-1电流密度下,最大放电比容量为274.3 mAh·g^-1,比未包覆材料提高了12.8%。在1000 mA·g^-1电流密度下经过500次循环后,包覆后材料的放电比容量保持率高达84.1%,表现出优异的循环稳定性。MgO包覆层的存在避免了MnO2与电解液之间直接接触,抑制了电极材料在充放电过程中锰的溶解,从而显著提高MnO2的循环性能。

MnO2@MgO core-shell microspheres were synthesized by coprecipitation method and pyrolytic process.The materials were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscopy(TEM).It is found that MgO coating did not change the microstructure of MnO2,and the coating layer was composed of nanoparticles with a thickness of about 50 nm.As a result,electrochemical property showed that the discharge specific capacity of the coated material was obviously improved.The maximum discharge specific capacity was 274.3 mAh·g^-1 at the current density of 100 mA·g^-1,which was 12.8%higher than that of the uncoated material.Meanwhile,the coated material exhibited excellent cycle stability with 84.1%discharge specific capacity retention after 500 cycles at the current density of 1000 mA·g^-1.Obviously,the MgO coating layer prevents directly contact between MnO2 and electrolyte,and suppresses the dissolution of manganese during the charge and discharge process,thus significantly improves the cycle performance of MnO2.