| In order to address global warming and energy crisis,and to reduce the consumption of non-renewable fossil resources and greenhouse gas emissions such as carbon dioxide and methane,it is necessary to vigorously promote the construction of green urban transportation networks and integrate renewable energy into smart grids.Rechargeable secondary ion batteries have attracted extensive attention due to their higher conversion efficiency and environmental friendliness.Improving the mass/volume energy density and lifespan of lithium ion batteries(LIBs)is currently the main challenge to avoid "mileage anxiety".In addition,factors such as limited lithium resources,uneven distribution and difficult recovery of lithium resources have greatly restricted the application of LIBs in large-scale energy storage systems.Sodium ion batteries(SIBs)are considered as a potential replacement for LIBs in large-scale energy storage systems due to their low cost and abundant reserves.The specific capacity and voltage platform of electrode materials determine the energy density of LIBs/SIBs,so it is crucial to develop alloy-type anode materials with high specific capacity,suitable voltage platform and long cycle life.Recently,Sn/Sb-based anode materials with high theoretical specific capacity have received extensive attention.However,the commercial application of alloy-type anode materials still faces many challenges,such as huge volume expansion during charge and discharge,slow reaction kinetics and unstable SEI films.Constructing a three-dimensional nanoporous structure and introducing active/inactive metal elements can effectively accommodate the huge volume expansion,shorten the ion transport path and improve the reaction kinetics.Carbon/alloy composites can synergistically take advantage of the high stability of carbon-based materials and the high specific capacity of alloy materials to obtain excellent electrochemical performance.Interfacial modification strategies can improve the adhesion between thin metal films and substrates and improve the structural stability of binder-free electrodes.In this scene,the tin/antimony-based alloy anode with high specific capacity were investigated thoroughly,including Li+/Na+storage/transport characteristics,Li+/Na+storage mechanism and gas evolution behavior.Simultaneously coupled with strategies such as three-dimensional nanoporous structure design,alloy composition regulation,carbon/alloy composite material construction,and film-substrate interface modification,NiSn,NiSb alloys,Sb@C,BiSb@C and binder-free Sb-based metal thin films were successfully prepared.The main research content and results are as follows:(1)Based on the difference in the corrosion rate of nickel and tin in acid,the precursor alloy of Al97.5Ni2Sn0.5 was designed.Through the two-step dealloying in NaOH and HNO3 solutions,the NiSn alloy(NiSn-3h and NiSn-6h samples)were fabricated with a threedimensional connected ligament-channel structure and rich nanowalls on the surface of the ligament.As for the LIBs anodes,the NiSn-3h sample exhibits excellent cycle stability with the specific capacity of 213.9 mAh g-1 after 1000 cycles at a current density of 1 A g-1.This is mainly attributed to its three-dimensional connected ligament-channel structure,which is conducive to the infiltration of electrolyte,shortens the ion diffusion path and improves its reaction kinetics.In addition,the porous structure can effectively relieve the volume expansion during repeated charge/discharge and improve the structural stability.In-situ X-ray diffraction(XRD)results show that the products of NiSn-3h alloy during the discharge process are Li5Sn2 and Li7Sn2 with low crystallinity.On-line differential electrochemical mass spectrometry(DEMS)confirmed that the gas production process of NiSn-3h electrode mainly occurred in the first discharge process,and the gas produced were mainly H2 and C3H6.(2)The single-phase np-NiSb alloy with bicontinuous ligament-channel structure was prepared by "rapid solidification+dealloying" strategy.As an anode for SIBs,np-NiSb alloy exhibits superior cycle stability with a capacity retention of 97%(279.7 mAh g-1)after 100 cycles at 1 A g-1 and excellent rate capability(155.6 mAh g-1 at 20 A g-1).Based on the CV,EIS and GITT results,the np-NiSb alloy exhibits excellent Na+diffusion rate and electron transfer kinetics.The excellent Na storage performance can be attributed to the unique nanoporous structure,which can effectively shorten the Na+ diffusion distance.The inactive Ni element not only improves the electrical conductivity,but also enhances the structural stability as a buffer matrix.In-situ XRD results show that the alloying/dealloying process of np-NiSb alloys in SIBs is highly reversible:NiSb(crystalline)(?) Ni(amorphous)+NaxSb(amorphous)(?)Na3Sb(crystalline)+Ni(amorphous).(3)A scalable pyrolysis route is proposed to fabricate ultrafine Sb nanoparticles confined in a porous carbon framework.The Sb@C composites were prepared by one-step pyrolysis,with commercial antimony potassium tartrate as precursor.It exhibits excellent Na+ storage and operation behavior with a capacity retention of 93%after 100 cycles at 0.2 A g-1.Even at a high current density of 10 A g-1,it can still deliver a capacity of 261.1 mAh g-1.The CV and GITT results indicate that the Sb@C composite has fast ion/electron transfer kinetics.This is attributed to the shortening of ion transport path by ultra-small size of Sb nanoparticles and the fast electron transport network of the porous carbon framework.Online DEMS reveals the gas evolution process of Sb@C in SIBs.In addition,the full cell with Na3V2(PO4)2F3/Sb@C as cathode/anode exhibits a high operating voltage of 2.95 V and an energy density of 152.2 Wh kg-1.This simple and easy preparation method provides a feasible way to prepare highperformance Sb-based anode materials.(4)Based on the above-mentioned simple pyrolysis strategy for preparing carbon/metal composites,combined with the alloying strategy,a series of bismuth-antimony alloy with different compositions confined in a porous carbon matrix was successfully prepared by introducing an organic bismuth salt(bismuth citrate).The synergistic effect between the optimized Bi-Sb composition,porous carbon matrix,and nanoscale particles can effectively alleviate the stress changes caused by volume expansion/shrinkage during charging/discharging,improving the structural stability.In addition,in-situ XRD results verified the synergistic sodium storage mechanism of Bi1Sb1@C composites during the sodiation/desodiation process:BiiSb1(?)Na(Bi1Sb1)(?)Na3(Bi1Sb1).(5)The optimization effect of Ag3Ga thin film as binding layer on the interface between metal thin film and stainless steel substrate was investigated.The Ag3Ga alloy thin film was prepared by DC magnetron sputtering-gallium brushing-annealing process on the stainless steel flexible substrate.Then the Sb thin film was sputtered on Ag3Ga layer and annealed to obtained the binder-free GaSb alloy thin film electrode(Sb@Ag3Ga-400).The degree of sodiation of Sb@Ag3Ga-400 is limited by controlling the cut-off voltage during the charge and discharge processes.When the voltage window is 0.01-0.75 V(vs.Na+/Na),the Sb@Ag3Ga-400 alloy thin film exhibits excellent cycle stability up to 400 cycles at a high current density of 1 A g-1.According to the in-situ XRD results,it was found that the Sb@Ag3Ga-400 electrode has amorphous sodium products and the GaSb phase is regenerated after charging to 1.5 V(vs.Na+/Na).The phase transition process is reversible. |
PDF Full Text Request