Preparation Of Binary Zn-Mn Oxygen Compound/Carbon Composites For Lithium-ion Batteries

Lithium-ion battery,as the most commonly used energy storage device at present,its development speed will determine the convenience and durability of people’s future life to a certain extent.At present,there are many researches on cathode materials for lithium batteries,so the search for a high-performance anode material become important.In recent years,due to considerable theoretical capacity,abundant raw material reserves and unique physical and chemical properties,Zn/Mn oxygen compounds have been the research hotspots of lithium battery anode materials.Due to the problems of poor conductivity and volume expansion,this article modified it through the dual role of nanometerization and compounding,and prepared three new Zn/Mn binary oxygen compound/carbon composite materials.The main research results are as follows:Using the waste TENCEL mask cloth as the carbon source,a three-dimensional network structure of Zn Mn₂O₄/carbon fiber composite material was synthesized by a simple hydrothermal calcination method,in which Zn Mn₂O₄ nano spherical particles were evenly embedded on the carbon fiber.The carbon fiber not only increases the electronic conductivity of Zn Mn₂O₄,but also has excellent mechanical properties to ease the expansion stress during charge/discharge process.After 80 cycles at a current density of 100 m A g^-1,its discharge capacity is still as high as 860.8 m Ah g^-1.After 950cycles at a current density of 1 A g^-1,the capacity is 709.2 m Ah g^-1,reaching a high capacity retention rate of 70.3%.Using a simple solvent method,two morphological bimetallic MOF materials Zn-Mn-BTC were prepared by changing the amount of PVP,which were used as precursors to sulfide synthesis（Zn,Mn）S/C composites under high temperature inert atmosphere.When the amount of PVP is 5 g,the prepared（Zn,Mn）S/C has a short cubic structure.When the amount of PVP is doubled（10 g）,the composite material is a slender rod or rectangular parallelepiped structure.（Zn,Mn）S/C composites have outstanding cycle stability and rate performance,and the reversible capacity of（Zn,Mn）S/C-PVP5 is significantly batter than（Zn,Mn）S/C-PVP10.At a current density of 100 m A g^-1,the first discharge capacities of（Zn,Mn）S/C-PVP5 and（Zn,Mn）S/C-PVP10 are 1286.7 and 1051.6 m Ah g^-1,after 70 charge and discharge cycling,they dropped to 722.4 and 548.8 m Ah g^-1 respectively.After 700 cycles at a current density of 1 A g^-1,their capacities remained at 459.95 and 347.81 m Ah g^-1,respectively.It shows that a reasonable structural design for electrode material is essential.A simple structured MOF material Zn-Mn-ptcda was synthesized by a simple hydrothermal reaction.Taking Zn-Mn-ptcda as a precursor,through direct selenization and accompanying carbonization,Zn_0.697Mn_0.303Se/C composite was formed material.The composite material is a two-dimensional elliptical sheet-like structure,similar to the shape of a leaf.It is composed of a large amount of nano-scale Zn_0.697Mn_0.303Se small particles wrapped in a carbon matrix.Its specific surface area is up to 213.9 m² g^-1.Its rate characteristics are particularly prominent.The Zn_0.697Mn_0.303Se/C composit has a reversible capacity of up to 1005.14 m Ah g^-1 after 110 charge-discharge cycles at a current density of 100 m A g^-1.After 1000 cycles at 1 A g^-1,the capacity remains at653.79 mAhg^-1.