Structure Optimization And Potassium Storage Mechanism Of Tin Disulfide Matrix Composites

Potassium-ion batteries(PIBs)are considered to be promising energy-storagesystem in post-Li-ion batteries.However,the large radius of potassium ions leads to slow solid-state diffusion in electrode materials and a significant volume effect,restricting the potassium storage performance of the electrode materials.How to design and construct anode materials with high K-ion storage capacity and fast diffusion becomes the key problem to be solved urgently.Layered metal sulfide,Sn S2,is considered a promising candidate for PIBs owing to the high theoretical capacity and the unique interlayer passages for K-ion diffusion.However,insufficient electronic conductivity,slow K-ion diffusion kinetics in the solid phase,inevitable volume expansion,and dissolution of polysulfides result in the capacity degradation and limited cycle life of the Sn S2 anode.To solve the above problems,three strategies namely "regulating ion-electron bicontinuous transfer avenues;constructing heterogeneous structures;as well as doping copper and further hybridizing GO and PDA" are proposed in this dissertation.The research contents are as follows:1.Sn S2 and carbon hybrid submicro-fibers with optimized channels were prepared by electrospinning by adjusting the ratio of PAN to PMMA,as integrated PIBs electrodes to clarify the effect of the bi-continuous avenues on the rate capability.In this configuration,Sn S2 nanosheets are confined by carbon and further crosslinked into3 D network.The 3D carbon submicro-fibers are adopted as a network for electron transfer,while the channels play the role of ion diffusion avenues.Owing to the stable and expedite bicontinuous electron/ion avenues,the rate capability of the Sn S2@C-1V1 SMFs electrode is improved(137.5 m Ah g-1 at 2.0 Ag-1)when compared to the Sn S2@C-1V0 SMFs and Sn S2@C-1V2 SMFs electrode(3.6 and 94.5 m Ah g-1at the same condition,respectively).Moreover,the lower voltage hysteresis and overpotentials were also delivered.2.Few layered Ti3C2 Tx nanosheets were selected as the multi-functional substrate to spread Sn S2 by an in-situ method,constructing ultrathin Sn S2/Ti3C2 Tx heterostructural nanosheets(HNs).The thickness of the HNs is as thin as about 5 nm,which shortens the K-ion diffusion distance.In this configuration,the formed Ti-S bonds provide robust interaction between Sn S2 and Ti3C2 Tx nanosheets,which hinders the agglomeration of Sn S2 and the restack of Ti3C2 Tx,endowing the hybrid material with robust nanostructure.Thus,the shortcomings of the Sn S2 anode are muchly relieved.In this way,the as-prepared Sn S2/Ti3C2 Tx HNs electrode delivers reversible capacities of462.1 m Ah g-1 at 0.1 A g-1 and 166.1 m Ah g-1 at 2.0 A g-1,respectively,and a capacity of 85.5 m Ah g-1 is remained even after 460 cycles at 2.0 A g-1.These results are superior to those of the Sn S2 micro-flowers(MFs)counterpart electrode without the addition of the few-layered Ti3C2 Tx nanosheets.3.Cu-doped Sn S2 nanoflowers(Sn S2-Cu)were synthesized in one step via a facile solvothermal method.Reasonable copper doping can inhibit the layer number of nanosheets,enlarge the interlayer spacing and generate rich defects.When Sn S2-Cu evaluated as PIBs anode material,the reversible capacity increased from 176.4 to 492.8m Ah g-1 and the initial coulomb efficiency significantly improved from 38.17% to67.29% compared with Sn S2 without copper doping.After hybridizing with graphene and further wrapping PDA to enhance structural stability,the as-prepared Sn S2-Cu/GO@PDA electrode exhibits excellent cycling stability and rate capability.The reversible capacity of 391.8 m Ah g-1 is still maintained at 0.1 A g-1 even proceeding for 100 cycles,and the rate capacity is 201.3 m Ah g-1 at 2.0 Ag-1.