Preparation And Electrochemical Performance Of Molybdenum Phosphide Nanoparticles As Anode Materials For Lithium Ion Batteries

At present,with the continuous improvement of social and technology,people are facing more and more environmental problems,which makes the demand for developing environmentally friendly clean energy urgent.Among them,lithium ion batteries are one kind of rechargeable batteries,which have smaller volume,higher energy density,longer cycle life,and could be environmentally friendly,sustainable and practical.It has gained widespread attention and research and is now applied to various areas.As an important component of lithium-ion batteries,anode materials have a great influence on the electrical performance of lithium-ion batteries,so it is one of the research priorities over lithium-ion batteries.Among varies of lithium ion battery anode materials,transition metal phosphides are considered to be excellent anode material due to their advantages of high capacity,low voltage platform,low price,and small volume expansion effect.The molybdenum phosphide material exhibits excellent structural stability when used as a catalyst of batteries.Although rarely studied as a anode material,it also has a lot of potential.In this experiment,two stable phases of molybdenum phosphide,namely MoP and MoP₂ nanomaterials,were prepared and tested as anode materials for lithium ion battery.The differences between the two materials were analyzed.In this context,the preparation of materials can be divided into two steps.First,the DC method is applied to fabricate metal molybdenum nanopowders as precursor.Second,molybdenum nanopowders reacts with the red phosphorus through solid-phase reaction to obtain molybdenum phosphide nanoparticles.MoP and MoP₂ nanoparticles were prepared according to different materials and suitable reaction conditions.The structure of the obtained product was characterized by x-ray diffraction and transmission electron microscopy.The MoP nanoparticles showed a spherical structure with a particle size of about 20-50 nm,while the MoP₂ nanoparticles were mostly lamellar.From the results of electrochemical tests,the initial discharge specific capacity of the MoP nanoparticle anode material was 746 mAh/g at a current density of 100 mA/g.After 50 cycles,the discharge specific capacity was obtained.Maintaining at 241.9 mAh/g,after passing current densities of 100,200,500,1000 and 2000mA/g in the rate test,it exhibits excellent reversibility when the current density returns to 100mA/g.The MoP₂ nanoparticles have a first discharge specific capacity of 1041.5 mAh/g at a current density of 100 mA/g,and a discharge specific capacity of 686.6 mAh/g at the 60th cycle,and are tested at a rate.It also showed excellent reversibility.The difference between MoP and MoP₂ nanoparticles is not only reflected in different crystal structures,but also in the lithium deintercalation process.When the cycle performance test is performed under the same conditions,the MoP₂ nanoparticle anode material exhibits a higher capacity.The capacity,after the battery capacity is stable,its discharge specific capacity is also much higher than the MoP nanoparticle anode material under the same conditions,and it is a lithium ion battery anode material with great potential.