Preparation Of Sheet-structured Energystorage Composites For Lithium Battery Electrodes And Their Electrochemical Properties

Lithium-ion batteries are widely used in electric vehicles,mobile electronic devices and other fields due to their high operating voltage,wide operating temperature range,etc.However,taking the negative pole of lithium ion battery as an example,there are problems such as low capacity,easy agglomeration of materials and insufficient structural stability.Another new type of secondary battery,lithium-sulfur batteries have great development potential because of their high energy density and high theoretical capacity,but they are also constrained by the low conductivity of sulfur,excessive volume change,"shuttle effect"and so on.In order to meet the development needs of energy storage devices,the development of high-performance electrode materials based on secondary battery applications has become an important research direction.Herein,we are working on developing high stability energy-storage materials,deeply studying the preparation method and electrochemical characteristics of composite electrode materials,providing the foundation for the development of high-performance secondary batteries.Specific research contents and innovations include:?1?A novel Co₂SiO₄ nanosheet with hollow porous structure was synthesized through a sample templated method.It was found that the cathode of lithium ion batteries based on Co₂SiO₄ nanosheets showed a high and stable capacity of 1456 mAh g^-1 after 200 cycles at 0.2 A g^-1,and exhibited an excellent rate-performance after three rounds of cycling.Then,the electrochemical kinetics and charge storage mechanism of the composite electrode were analyzed by cyclic voltammetry.In addition,the process of dynamic lithiation was studied using an in situ transmission electron microscopy technology.?2?A novel hierarchical composite consisting of an ordered NiCo₂O₄ nanowire array growing on the lateral side of a Fe₂O₃ microdisc was designed and synthesized,which can greatly alleviate the volume expansion of electrode materials effectively.The composites were observed by using X-ray holography on synchrotron radiation station.It was showed that the synergy between the Fe₂O₃ microdisc and laterally grown NiCo₂O₄ nanowire arrays enhanced the conductivity and reactivity of the electrode.The mechanism of electrochemical reaction was investigated by ex-situ XRD.The cathode of Li-ion batteries based on Fe₂O₃@NiCo₂O₄ exhibited a high capacity of 1528 mAh g^-11 after 200 cycles at 0.2 C.The charge/discharge and multiple rate tests at different current densities and the density functional theory calculations have proved that Fe₂O₃@NiCo₂O₄ composites have a good structural stability,and thus can effectively improve electrochemical lithium storage performance.?3?An In₂S₃@C@S core-shell structure with In₂S₃ microspheres assembled from layered nanosheets as the main body was prepared.The adsorption of polysulfides of In₂S₃ core and physical limitation of the outer carbon shell structure can effectively reduce the shuttle effect of lithium-sulfur batteries.Meanwhile,the core-shell structure can effectively buffer the sulfur volume expansion during the cyclic process.The cyclic performance and rate-performance under different current densities were tested respectively.It presents a high capacity of 704 mAh g^-1 cycling for 200 times at 0.2 C,and remains 583 mAh g^-1 after cycling 400 times at 0.5 C.The above studies provide some new idea for improving the capacity and electrode stability of secondary batteries,which have important potential applications.Moreover,the high-performance electrode composites and the controllable preparation technology also provide a foundation for the research of new high-performance batteries.