| With the commercial application of lithium-ion batteries,lithium-ion batteries have been used on a large scale in fields such as portable electronic devices and electric vehicles(EVs).However,the large-scale application of lithium-ion batteries in various fields has increased the demand for the energy density of lithium-ion batteries.At present,the energy density of traditional lithium-ion battery systems based on graphite anodes has approached its theoretical energy density.Therefore,the development and development of energy storage battery systems with higher energy density is of great significance to alleviate social energy problems.Due to their relatively high theoretical specific capacity of lithium metal(3860m Ah g-1)and sulfur cathode(1675 m Ah g-1),lithium metal batteries and lithium-sulfur batteries have attracted extensive attention and research as energy storage battery systems with high energy density.In addition,the application of lithium-ion batteries in the field of large-scale energy storage and the relative scarcity of lithium resources have made sodium-ion batteries with relatively abundant resources as a potential replacement for lithium-ion batteries.This thesis mainly studies the energy storage system of lithium metal battery and lithium sulfur battery with high energy density and the energy storage system of sodium ion battery with abundant resources.The specific researches are mainly on the use of lithiophilic current collectors for lithium metal batteries and nanosheet array structure substrates for lithium sulfur batteries and nanosheet array structure binder-free sulfide anode materials for sodium ion batteries.The following are the main contents and results of the study:(1)Mixed ionic/electronic conductor nanosheet arrays as lithiophilic current collectors for stable lithium storage.Lithophilic current collectors with lithiophilic nanosheet arrays(Ni-LONSs)with mixed electronic conductors(Ni)and ionic conductors(Li2O)were fabricated on the nickel foil(NF)surface by using a relatively simple synthesis method for lithium metal battery.The electrochemical performance of current collectors using Ni-LONSs for lithium metal battery was investigated through corresponding electrochemical performance testing and characterization.The nanosheet array layer on Ni-LONSs collector surface obtained by using a relatively simple preparation method is lithophilic.As a result,Ni-LONSs current collectors can effectively reduce the actual current density during Li metal plating/stripping,and can provide a large number of lithiophilic sites for uniform nucleation of Li metal.In addition,the nanosheet array structure of Ni-LONSs current collectors can alleviate the volume change during Li metal plating/stripping.In comparison with the NF current collector,due to the specific nanosheet array structure of Ni-LONSs current collector,the Ni-LONSs current collector demonstrates excellent coulombic efficiency of 97.2%after 280 cycles(95.7%after 100 cycles of NF current collector)and satisfactory cycling lifespan of 340 h(about 120 h of NF current collector)at 0.5 m A cm-2with 1.0 m Ah cm-2.In addition,the Ni-LONSs current collector was applied to Li metal full batteries,and the Ni-LONSs collector showed a high initial reversible capacity of 141.3m Ah g-1 with a capacity retention of 81.3%after 300 cycles at 1.0 C(1.0 C=170 m A g-1).Compared with NF current collectors,Ni-LONSs current collectors show more excellent electrochemical performance.(2)Mixed ionic/electronic conductor nanowires-modified Cu foil for high-performance lithium metal anodes.Lithophilic nanowire arrays(Cu-LPNWs)current collectors with mixed electronic conductors(Cu)and ionic conductors(Li3P)were fabricated on the surface of copper foil(Cu foil)current collectors using a relatively simple synthetic method and applied to lithium metal batteries to induce uniform deposition of lithium metal.The electrochemical performance of lithium metal batteries using Cu-LPNWs current collectors was investigated through corresponding electrochemical performance testing and characterization.The Cu-LPNWs current collectors with mixed electronic(Cu)and ionic conductors(Li3P)can accelerate electron conduction through Cu and uniform lithium metal deposition through Li3P.Therefore,the Cu-LPNWs current collectors show relatively excellent electrochemical performance for lithium metal batteries.The lithiophilic abilities of Li3P and Cu were calculated using density functional theory(DFT),indicating that the Cu-LPNWs current collectors have better lithiophilic properties.The relatively excellent electrochemical performance of Cu-LPNWs current collectors for lithium metal batteries was investigated by in situ and ex situ characterization.The Cu-LPNWs current collector for lithium metal batteries can deposit a high capacity of more than 5 m Ah cm-2 without obvious lithium dendrite formation.Furthermore,the Cu-LPNWs current collector exhibits a relatively excellent coulombic efficiency of 99.1%after 600 cycles at 0.5 m A cm-2 with 1.0m Ah cm-2.The Cu-LPNWs current collector exhibits a relatively satisfactory cycling lifespan of over 3000 h at 1.0 m A cm-2 with 1.0 m Ah cm-2.In addition,the Cu-LPNWs current collectors were combined with Li Fe PO4(LFP)or Li Ni0.8Co0.1Mn0.1O2(NCM)electrodes to assemble lithium metal full cells,and the Cu-LPNWs current collectors showed relatively satisfactory cycling performance(LFP electrode and NCM electrode showed 72.9%and 84.8%capacity retention after 1500 cycles and 300 cycles,respectively).(3)In situ growth of NiS2 nanosheet arrays on nickel foil as cathode for improving the performance of lithium/sodium-sulfur batteries.NiS2 nanosheet arrays was fabricated on nickel foil(NF)current collector(NiS2/NF)and applied to lithium/sodium-sulfur batteries by using an in situ growth and sulfidation method.The electrochemical performances of lithium/sodium-sulfur batteries using sulfur electrodes with NiS2/NF current collectors(NiS2/NF-S)are investigated through corresponding electrochemical performance tests and characterizations.The NiS2/NF electrode fabricated using the in situ growth and sulfidation method have a specific nanosheet array structure that can provide abundant active sites for polysulfide adsorption and chemical interactions.Therefore,the ion/electron transport of polysulfides can be promoted and the chemical reactions of polysulfides can be accelerated.Compared with the sulfur powder coated pure NF(NF-S)for lithium sulfur battery,the NiS2/NF-S electrode exhibits superior electrochemical performance.Specifically,the NiS2/NF-S delivered a high reversible capacity of 1007.5 m Ah g-1at 0.1 C(1 C=1675 m A g-1)and kept 74.5%of the initial capacity at 1.0 C after 200 cycles,indicating the great promise of NiS2/NF-S as the cathode of lithium sulfur battery.In addition,the NiS2/NF-S electrode also showed relatively better electrochemical performance compared with the NF-S electrode when used as the cathode for sodium sulfur battery.(4)In situ growth of NiS2 nanosheet arrays on stainless steel foil as binder-free anode materials for high power sodium ion batteries.The NiS2 nanosheet arrays were directly grown on stainless steel foil(SS)current collector(NiS2/SS)using an in situ growth and sulfidation strategy as the binder-free anode material for sodium ion batteries.The sodium ion storage performance of NiS2/SS electrode was investigated by using corresponding characterizations and electrochemical performance tests.The NiS2/SS electrode synthesized using an in situ growth and sulfidation strategy.Due to the close contact between the active material NiS2 nanosheets and the SS,the NiS2/SS electrode has higher electronic conductivity and richer interconnected ion/electron transport paths than the NiS2nanoparticles electrodes with the binder(NiS2/CMC and NiS2/PVDF).The NiS2/SS electrode demonstrates high rate capability with a reversible capacity of 492.5 m Ah g-1 at5.0 C rate.Such rate capability is superior to that of NiS2 nanoparticles electrodes(NiS2/CMC:41.7 m Ah g-1 at 5.0 C and NiS2/PVDF:7.3 m Ah g-1 at 5.0 C)and other Ni sulfides(100–450 m Ah g-1 at 5.0 C)reported.Furthermore,the initial reversible specific capacity and coulombic efficiency of NiS2/SS are 786.5 m Ah g-1 and 81%,respectively,demonstrating a better sodium storage ability than those of most NiS2 anodes reported for sodium ion batteries.In addition,the amorphization and conversion mechanism during the sodiation/desodiation process of NiS2 are proposed after investigation by in situ X-ray diffraction(XRD)measurements of intermediate products at successive charge/discharge stages. |
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