Construction And Potassium Storage Performance Of Three Dimensional Carbon-confined Sb/Ni-based Anode Materials

Since the potassium ion has been confirmed to have the capability of being embedded/extracted between graphite layers,the development of potassium ion batteries（KIBs）has become another hotspot and frontier in the field of energy storage.In the current research of KIBs,both the alloy-type and the conversion-type anodes such as transition metal chalcogenide can realize the multi-electron transfer resulting in a high theoretical capacity,thereby have received extensive attention.However,a large volume change occurs during the potassiation-depotassiation process,and the mechanism of potassium storage is still unclear.How to obtain electrode materials through efficient structural design is a great challenge in current research.In this thesis,we have constructed a three-dimensional carbon skeleton confined Sb nanoparticle anodes and a three-dimensional crumpled graphene-confined NiS₂ electrode material by confining the Sb nanoparticles and the Ni-based chalcogenide to the carbon framework.The electrochemical performances of these two carbon-confined composite materials as KIB anodes were studied,and the mechanism of potassium storage in the electrochemical reaction process was investigated.The main results are as follows:1.A simple approach for preparing a three-dimensional carbon skeleton confined Sb nanoparticle（3D SbNPs@C）composite material was developed.By using the NaCl template-assisted self-assembly method followed by carbothermal reduction,the Sb³⁺was successfully reduced to Sb nanoparticles and confined inside the carbon skeleton.The superiority of the designed 3D SbNPs@C structure was demonstrated by comparison with the bulk Sb powder electrode material.Electrochemical performance tests show that the reversible capacity can reach 461 mA h g^-1 at a current density of200 mA g^-1,and even maintain 228 mA h g^-1 after cycling for 50 cycles at a high current density of 1000 mA g^-1.2.By means of in-situ XRD and ex-situ TEM techniques,combined with the basic principles of electrochemistry,the energy storage mechanism of Sb-based anode as KIBs is revealed.Firstly,K⁺is inserted into Sb to form K-Sb alloys and finally transformed into cubic phase K₃Sb through the alloying reaction,which proves a two-step potassium storage mechanism and provides theoretical support for the further development of high-performance Sb-based anode in KIBs.3.A composite electrode material with three-dimensional crumpled graphene-confined nano-nickel disulfide（3D NiS₂/GO）was constructed.Firstly,the effects of different sulfur sources and graphene on its structure and morphology were investigated.The correlation between the 3D NiS₂/GO structure and electrochemical performance was analyzed by comparison with the performance of the pure NiS₂.When the as prepared 3D NiS₂/GO was applied to KIBs,the reversible capacity of 391 mA h g^-1 was maintained after 50 cycle at a current density of 100 mA g^-1.In addition,the potassium storage mechanism of Ni-based chalcogenide compounds in KIBs was investigated by in-situ XRD and ex-situ Raman.