| Tin-based alloys are regarded as ideal alternatives for commercial carbon anode materials due to their higher capacity and safety,but their practical implementation is severely restricted by the huge volume change.Hybridization alloys with heterogeneous components is an effective method to improve the structural stability,reversible capacity and charge transport capability of anodic systems.However,the phase regulation of tin-based alloys remains a significant challenge,and the relationship between phase and Li-storage mechanism is not quite clear.Besides,the heterogeneous components are physically hybridized with tin-based alloys,and their weaker interfacial forces hinder the full achievement of hybridization merits.To overcome these challenges,in this thesis we develop a gel-enabled wet-chemical reduction route for selectively synthesize amorphous and metastable tin-based alloys usingcyano-bridged coordination polymer gels(cyanogels)as precursors.Furthermore,these tin-based alloys have been hybridzed with carbon or silicon matrices via strong covalent bonds,and the complex relationships between phase/interface and Li-storage performance/mechanism of hybrid anodic systems have been examined and uncovered.The main innovations of this thesis are as follows:(1)Phase engineering:Preparation and Li-storage mechanism of amorphous and metastable Sn–Ni alloy frameworks.By using Sn–Ni cyanogels as precursors,Sn–Ni alloy frameworks have been fabricated via a wet-chemical reduction route.The phase regulation of Sn–Ni alloys has been realized through the modulation of solvent polarity and solvent/cyanogels interaction force.Specifically,amorphous and metastable Sn–Ni alloys have been prepared in aqueous and diethylene glycol(DEG)solvents,respectively,and the relationship between phase and Li-storage mechanism has been further studied.Compared with amorphous alloys,the metastable phase alloy exhibits more stable electrochemical properties,ensuring excellent lithium storage performance.At high current densities of 5 and 10 A g-1,metastable phase alloy exhibits reversible capacities of 313 and 205 m Ah g-1,respectively,which is much higher than the average specific capacities of amorphous alloy(75 and 19 m Ah g-1,respectively).(2)Interface engineering:Preparation and Li-storage mechanism of carbon black-composite amorphous Sn–Ni alloy framework.By using carbon black-hybridized Sn–Ni cyanogel(water as the solvent)as a precursor,the carbon black-hybridized amorphous Sn–Ni alloy framework has been fabricated via a wet chemical-reduction route.The hydrogen bonds between cyanogel and carbon black contributes to the formation of interfacial chemical bonds(Sn–O–C bonding)after reduction.Hybridization alloys with carbon matrices is beneficial for improving anodic stability and electron capability,while the strong interfacial chemical bonding of Sn–O–C can accelerate ion shuttling,facilitating long-term cycle life(400 m Ah g-1 after 350 cycles at 0.2 A g-1)and fast reaction kinetics(294 and 190m Ah g-1 at 5 and 10 A g-1,respectively).(3)Interface engineering:Preparation and Li-storage mechanism of Si-composite metastable phase Sn–Ni alloy framework.By using Si particle-hybridized Sn–Ni cyanogel(diethylene glycol as the solvent)as precursors,the Si-hybridized metastable phase Sn–Ni alloy framework has been fabricated via a wet chemical-reduction route.The hydrogen bonds between the natural oxide layers on the surface of silicon particles and the cyanide groups are beneficial for the formation of interfacial chemical bonds(Si–O–Sn bonding)after reduction.Moreover,the rearrangement of Si particles in the holes of Sn–Ni alloy framework increases the dispersity of Si inside as well as the synergic effects between them toward lithium storage.Benefiting from the excellent electrochemical stability of the metastable phase Sn–Ni alloy and the fast ion/electron transport due to the interfacial chemistry,Si–composite metastable phase Sn–Ni alloy framework exhibited the prolonged life span(1205 m Ah g-1 after 100 cycles at 0.5 A g-1)and excellent rate performance(886 and 653 m Ah g-1 at 5 and 10 A g-1,respectively). |
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