Studies On Three-dimensional Micro-nano Structures For Lithium Batteries

The construction of three-dimensional(3D)electrodes with micro-nano structure is a very important direction for the future development of lithium-based recyclable batteries.Due to high specific surface area and abundant pore,the 3D electrodes exhibit significant improvement in electrochemistry performance.On the one hand,the electrodes with 3D structure can shorten the distance of charge diffusion.On the other hand,3D porous structure is not only conducive to the infiltration of electrolyte and promotion of the active materials utilization,but also can effectively alleviate the volume expansion of active materials caused by lithium ion embedding during charging and discharging process.It can effectively avoid the stress effects between active material layer and current collector.However,there are still many defects in conventional 3D electrodes with porous struture.For example,the commercial metal foam has low surface area,larger pore size and very large weight,while the intrinsic conductivities of 3D porous carbon-based structures and metal oxide materials are not as good as that of metal-based current collector.In this paper,a series of 3D electrodes with high conductivity,light weight,multi-function,safety and stability were designed and fabricated from the point of view of current collectors and active materials,and their electrochemical properties as lithium ion or lithium metal electrodes were successfully tested.The full text can be divided into four systems.(1)Thin tin anode supported by 3D high conductivity titanium nitride nanotubes.High capacity tin anodes are demanded to increase the energy and power density of lithium ion batteries.However,the cycling and rate properties are severely affected by the large volume changes caused by the lithium insertion and extraction during cycling.Structured electrodes with mechanically stable scaffolds are widely developed to mitigate the adverse effects of volume changes.For tin metal,there is a critical value of tin particle size above which tin anodes will readily crack.Therefore,the electrode design using 3D mechanical scaffolds must retain tin particles below this critical size and concurrently enable high volumetric capacity.In this paper,we provided a highly conductive titanium nitride(TiN)nanotubes array with submicron diameters.It can maintain high volume capacity while keeping the tin layer thin.Such a structured electrode delivered a high initial capacity of 795 mA h gsn-1(tin mass basis)and 1812 mA h cmel-3(electrode volume basis).What' more,the long-term cycling showed only 0.04%capacity decay per cycle.(2)Nickel cobaltate nanowires array anode supported by ultralight nickel foam.3D conductive scaffolds are usually developed to build rapid electron/ion pathways and accommodate volume changes.However,the large pore size and thick skeleton weight of commercial nickel foam seriously affect the overall electrode performance.In this paper,using template-assisted electrochemical deposition and hydrothermal synthesis techniques,we developed a composite electrode consisting of high loading nickel cobaltate(NiCo2O4)nanowires on an ultralight nickel foam current collector.The uniform NiCo2O4 nanowires could provide large surface for rapid charge transports.The porous structure of ultralight nickel foam electrically could accommodate the volume expansion of NiCo2O4 nanowires during lithiation process.The composite electrode demonstrated a high performance microstructure for ideal lithium ion anodes.It not only enhanced the utilization of active materials but also increased the electrode based specific capacity by one order of magnitude as compared to the widely used nickel foam.The specific capacity of as-obtained composite electrode was 612 mA h gel-1(overall electrode mass basis),which is 13.3 times larger than that of commercial nickel foam current collector.(3)Multi-functional cobalt sulfide nanotube-sulfur 3D composite electrode.Lithium sulfur batteries attract the increasing attentions because of their high energy density.However,sulfur cathodes suffer from several scientific and technical issues which are related to polysulfide ion migration,low conductivity,and volume changes.Many strategies such as porous hosts,polysulfide adsorbents,catalysts,and conductive fillers and so on have been proposed to address these issues,separately.In this study,novel 3D network-like cobalt sulfide(Co3S4)nanotubes with high conductivity were developed to efficiently host sulfur,adsorb polysulfide,and catalyze polysulfide conversion.Because of these multifunctional advantages in one structure,the resulting Co3S4@S nano tube electrodes demonstrated superior electrochemical properties for high performance lithium sulfur batteries.An optimized Co3S4@S nanotube composite electrode was able to deliver a high discharge capacity of 1172 mA h gAs-1(active sulfur basis)at a rate of 0.1 C and showed a low capacity decay rate of 0.041%per cycle at a higher rate of 5 C.(4)Gold nanoparticles pillared graphene layer as composite 3D lithium metal anode.Lithium metal anodes suffer from serious safety issues and rapid capacity fade because of nonideal lithium plating-stripping behaviors.Lithium mteal nucleation on undesired positions usually results from nonuniform multiphysical feld distributions and the dynamically changing interface thermodynamics.In this paper,a 3D sandwich composite anode consisting of gold nanoparticles pillared reduced graphene oxides(rGO)was designed.Because the uniform gold nanoparticles preferentially induced lithium metal nucleation,the typically uncontrolled lithium deposition process became a highly controllable nucleation-guided process.Because the 3D sandwich structure of the Au-pillared rGO could provide a stable anode morphology with cycling and stabilize the solid electrolyte interface layer during volume expansion,the Au-pillared rGO delivered a high Coulombic effciency of up to 98%for at least 200 cycles for 1600 hours.Using this 3D pillared structure,an interlayer plating process was revealed in rGO-sandwiched anodes,which differ from either conventional metallic anodes or intercalation anodes.The Au-pillared design bridged the gap between metal and intercalation anodes,and provided a novel strategy to improve the effciencies and cyclability of safe lithium metal anodes.