| Since the first industrial revolution,there has been an explosive growth in the demand for energy.However,the use of primary energy sources such as oil and coal has caused a serious greenhouse effect.To increase the share of clean energy use,electricity needs to be stored for use.As the most popular energy storage device,batteries are an important measure to achieve the goals of "carbon peaking" and "carbon neutrality".Among them,lithium-oxygen batteries(LOBs)have attracted much attention because of their high theoretical energy density of 3500 Wh kg-1,and they are regarded as the first choice for next-generation batteries.However,there are still many obstacles to give full play to the energy density advantage of lithium-oxygen batteries and realize practical applications,among which the incomplete decomposition of discharge products at the cathode,which is the core site of electrochemical reactions,will lead to passivation of the cathode material surface,affecting the battery performance and accelerating battery death.The development of efficient cathode catalyst materials is essential to improve battery performance and promote the commercialization of lithium-oxygen batteries.The performance of oxide cathode catalysts is related to the crystal structure and its stability,and octahedra with redox activity play a key role in the catalytic reaction process.The wolframite structure with two sets of parallel octahedral frameworks is expected to improve the catalytic activity while enhancing the structural stability.In this work,we prepared a variety of materials with wolframite or wolframite-like structures by a simple combination of electrostatic spinning and calcination and explored their catalytic performance in lithium-oxygen batteries.Co-based oxides exhibit excellent metal-oxygen hybridization properties,and therefore,wolframite-based CoWO4 is expected to be an efficient catalyst for next-generation lithiumoxygen batteries,which is the focus of this paper.We analyzed the effect of the structure of CoWO4 on the catalytic performance through experimental exploration combined with Density Functional Therory(DFT)first principles calculations.In addition,we compared the performance advantages and disadvantages of wolframite-structured CoWO4 and wolframitelike structured molybdate in catalyzing lithium-oxygen batteries in ambient air.Therefore,this topic focuses on the following two aspects:(1)A one-dimensional cobalt tungstate(CoWO4)nanowire material was synthesized using electrostatic spinning plus calcination,its electrochemical catalytic performance was tested and analyzed,and the mechanism of the influence of wolframite structure on the catalytic performance of lithium-oxygen batteries was explained in combination with DFT theoretical calculations.Using electrostatic spinning method,combined with further calcination treatment,nanowires with one-dimensional structure were prepared and used in the study of lithiumoxygen battery cathode catalyst.It was experimentally demonstrated that the CoWO4 nanowires synthesized by electrostatic spinning method exhibited excellent catalytic performance in lithium-oxygen batteries.The catalytic reaction mechanism was analyzed and investigated by in situ DEMS tests and theoretical calculations,and the optimal material structure and electrochemical properties were obtained by changing the synthesis conditions,and the ultrahigh specific capacity of 11803 mAh g-1 was obtained at a current density of 200 mA g-1 and 154 cycles at a current density of 1000 mA g-1 and a limited capacity of 600 mAh g-1 with excellent cycling stability.(2)Molybdate materials with wolframite-like structure,zinc molybdate,copper molybdate and cerium molybdate powders,were prepared.Their morphology and structure were characterized and they were further prepared as lithium-oxygen battery to test and compare their electrochemical catalytic performance under ambient air atmosphere without additional protective measures.A series of molybdates:zinc molybdate,copper molybdate and cerium molybdate powders were prepared by a combination of electrostatic spinning and calcination.They were found to exhibit excellent cycling stability as lithium-oxygen batteries under ambient air atmosphere,with copper molybdate stable for 100 cycles,cerium molybdate stable for 90 cycles,and zinc molybdate can be cycled 70 times.In addition,we found that a mixture of cerium molybdate and cerium dioxide can be stably cycled for 200 cycles at a small current density of 200 mA g-1,which shows a very long cycle life.The present work is expected to open the way for the practical application of lithium-oxygen batteries. |
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