Study Of Cu-Based Anode Materials For Sodium Ion Batteries

With the rapid development of electronic equipments and electric vehicles?EVs?,it is necessary to study the energy-efficient,resource-rich and environment-friendly energy storage materials for human society to achieve sustainable development.However,most of the renewable energy sources can not provide a stable supply of energy due to their uncontrollable and intermittent shortcomings.So far,lithium ion battery?LIBs?have been developed for over two decades with great success,which have been widely used in electronic equipment,electric vehicles and other facilities,with penetrate into all areas of life.However,owing to the limited lithium resources,such technology is now facing difficulties with the large-scale application and sustainable development.Therefore,the development of alternative energy storage system is much urged.Sodium ion batteries?SIBs?have attracted wide attention as alternatives to LIBs,due to the abundant and low cost of sodium resources.Therefore,developing high performance SIBs will exert profound effects on larger-scale energy storage applications in the future.However,compared with the LIB with study of more mature,SIB is still an immature technology at current stage.Sodium ion has similar physics and chemical properties with lithium ion.However,compared to lithium ion,sodium ion possesses much larger radius,resulting in a drastic volume e xpansion and serious hysteresis during the electrochemical processs.Therefore,most of the efficient electrode materials for LIBs are no longer suitable for SIBs.Anode material,as the important component of an SIB,has significant effects on the overall electrochemical performances of SIBs.Moreover,the cost of anode materials also effects the large-scale application and development of SIBs.Hence,it is important to develop suitable,efficient and low cost anode materials in order to achieve an improved electrochemical performance of SIBs.At present,copper-based anode materials have attracted wide attention as potential anode materials for SIBs,due to the abundant resources and low cost of copper-based anode materials.In this paper,CuO and Cu3 P two kinds of copper-based anode materials were prepared and used as anode materials for SIBs with a series of electrochemical tests and characterization,respectively.?1?CuO nanosheets are studies as high capacity sodium ion batteries anode material.With uniform size and morphology 2D CuO nanosheets were prepared by a simple hydrothermal treatment method with cupric chloride,sodium hydroxide and deionized water as precursor.Compared with the materials obtained by ball milling,the 2D nanosheet structure materials prepared by hydrothermal treatment method has larger specific surface area.Moreover,the 2D nanosheet structure materials as electrode materials for SIBs has short ion/electron transport pathways and sufficient void space for volume expansion o f active materials during charge/discharge processes.C uO nanosheets electrode prepared with carboxymethyl cellulose?CMC?binder as anode electrode for SIBs showed significantly higher specific capacity and more satisfactory cycling stability.Specifically,CuO nanosheets electrodes with CMC binder showed a high reversible capacity of 627.2 mAhg^-1(close to the theoretical capacity 674 mAhg^-1)at 50 mAg^-1.Even at a high current density of 2000 mAg^-1,CuO nanosheet still deliverd a initial reversible capacity of 418.4 mAhg^-1 and 73.4% of initial capacity value after 100 cycles.Besides,poly?vinylidene?fluoride?PVDF?was used as the binder to investigated the effect of different polymeric binders on the electrochemical performance of SIBs.Furthermore,to explore the practical application of CuO nanosheets anode,a SIB full cell consisting of CuO nanosheets anode and the Na₃V₂?PO₄?₃?NVP?cathode was assembled and tested.?2?Cu₃P nanowires?CPNWs?were synthesized through directly grown on half surface of copper current collector via an in situ growth followed by phosphidation method.This method can be simple and large-scale preparation of Cu3 P nanowires that directly grown on half surface of copper current collector.Moreover,the C u3 P nanowires can directly used as anode electrode for SIBs without using conductive carbon or polymer binders in the electrode fabrication,which can decreases the batteries cost and simplifies the battery assembly process.Cu3 P nanowires directly as anode electrode for SIBs without using any additive in the electrode fabrication showed excellent electrochemical performance.As a result,the Cu3 P nanowires electrode demonstrated high specific reversible capacity(349 mAhg^-1 at 50 mAg^-1),good rate performance(137.8 mAhg^-1 at 5000 mAg^-1),and stable cycling performance(an average of 0.12% drop in capacity per cycle at 1000 mAg^-1 in 260 cycles).In addition,in order to investigate the effect of Cu3 P nanowires length on the electrochemical performance of SIBs,the different lengths of C u3 P nanowires were also synthesized.Besides,the charge/discharge reaction mechanism of C u3 P nanowires directly as anode electrode for SIBs is investigated by the corresponding characterization.Furthermore,to explore the practical application of Cu3 P nanowires directly as anode electrode for SIBs without using any additive in the electrode fabrication,a Na+ full cell consisting of CPNW anode and Na₃V₂?PO₄?₃?NVP?cathode is assembled and characterized.