| With the shortage of petroleum resources and the pollution problems it brings,replacing petroleum products with renewable resources to reduce their consumptions has become the current development trend.Especially the development of the biorefining industry,a large amount of biomass is widely used in different fields.How to convert and use these cheap biomasses with high added value is one of the hot topics in the current research field.Among them,the widespread application of biomass-derived carbon materials in the field of energy has attracted researchers' attention.This paper uses agricultural wastes(walnut shell,lignin)as raw materials,combined with electrospinning and surface modification methods to prepare lignin-based carbon nanofiber membranes,oxygen-enriched carbon membranes,and carbon/lithium composite membranes for high-performance lithium ion batteries.Some exploratory studies have been performed on their electrochemical performances and related mechanisms.The specific work includes the following aspects:(1)Porous carbon nanofiber derived from a waste biomass as anode materials in Li-ion batteries.In this work,we demonstrate the use of sustainable woody biomass(walnut shells)as a carbon-derived precursor for the controlled synthesis of mechanically flexible and free-standing CNF films with abundant pore structure as electrode materials for LIB.The PVA amounts and carbonization temperature has noticeable impact on electrochemical performances in LIB.As the amount of PVA or the carbonization temperature were increased,the less specific surface area and graphite-like layer of CNF are obtained,which were unfavorable for storing lithium ion.As a consequence,the 80-20-800 electrode shows the best overall performance,exhibiting a specific capacity up to 380 mAh g-1 at 0.03 A g-1,with excellent rate cycle performance(190 and 180 mAh g-1 at 1 A g-1 and 2 A g-1,respectively),and long cycling stability(above 280 mA h g-1 reversible capacity after 200 cycles at 0.1 A g-1).This present work holds great promise to achieve the low-cost,green and environmentally benign of walnut shell-derived CNF as electrode materials for applications in LIB.Meanwhile,this method provides a new possibility for converting raw biomass resources to advanced carbon materials.(2)Understanding the critical chemistry to inhibit lithium consumption in lean lithium metal composite anodes.Previous studies of lithium metal anodes have primarily utilized bulk lithium metal(e.g.,lithium foil),which could not represent practical lithium metal batteries where the loading of lithium metal must be minimized for improving safety and energy density.In this work,the formation of the Li/CNF composite anode has allowed us to design a lithium-limited full cell system,which has not been a heavily investigated area of research.The major benefit of using the electrodeposition method for inserting lithium is that the limited system allowed us a fast turnaround with observing changes in cell performance and cycle life based on modifications to the anode,either in total deposition capacity of lithium,or rate of electrodeposition,the electrolyte system,with the addition of electrolyte additives,and the change in C rate.We have found that the rate of consumption of composite anodes with mass loading to bypass the large initial consumption of lithium has a lifespan of?23 cycles(1C rate)per mAh/cm2.The increase in rate of deposition was found to have a negative effect on the cycling life of the composite anode due to the inhomogeneous plating of lithium on the CNF with increasing rate.XPS has shown that the addition of VC has increased the organic phase and the LiF content,while decreasing Li2CO3 to account for the increase in cell cycle life.Lastly,the deposition of lithium into a graphite anode has shown that graphite can lengthen the lifespan of active lithium and giving good cycle performance,with a capacity retention of 75%after 1000 cycles.Graphitic carbon has an influential effect on increasing the longevity of active lithium in the composite anode,and requires further investigation to determine the importance of the Li-C bonding environment to improve the lifespan of lithium.Finally,our study calls for utilizing limited lithium loading for investigating the anode chemistry in lithium metal batteries in order to remain relevant to future practical applications.(3)Flexible lignin carbon membranes with surface ozonolysis to host lean lithium metal anodes for nickel-rich layered oxide batteries.In this work,we prepared natural lignin-derived OLCM through electrospinning and surface ozonolysis.Natural lignin is widely available,low cost,and for the first time,used to fabricate the lithiophilic skeleton to host Li metal for nickel-rich layered oxide Li metal batteries.Because of the homogeneously distributed oxygen-containing functional groups,the OLCM offered uniformly distributed Li nucleation sites to guide the uniform Li growth during lithium metal deposition.The lean Li metal anode hosted in the OLCM skeleton exhibited high and stable Coulombic efficiency(>98%over 230 cycles),long cycle life(>1,000 hr),and small voltage hysteresis(<20 mV).The nickel-rich layered oxide batteries,assembled with the lean Li@OLCM composite anode,delivered high initial discharge capacities.Compared with the Cu and LCM hosts,the OLCM host improved the cycle life of the nickel-rich layered oxide batteries at var-ious CNMC811/CLi capacity ratios due to the decelerated Li consumption.The present study investigated the performance of carbon hosts without the interference of bulk properties using the surface-targeted ozonolysis method.Further advances in the performance of these lightweight,low-cost,flexible,and natural lignin-derived carbon membranes are foreseeable by engineering the carbon crystal structure and cell chemistry.(4)A surface chemistry approach to tailoring the hydrophilicity and lithiophilicity of carbon films for hosting high-performance lithium metal anodes.In this work,we have established a facile surface chemistry approach for tailoring the Li wettability of most carbon scaffolds(from non-wetting to super-wetting)and successfully fabricated a thin Li@CF composite anode with the assistance of a lithiophilic top layer on the lightweight lignin-based CF.The resulting Li@CF composite anode delivers a higher practical capacity of 3222 mAh g-1 than the reported Li hosts.A dense,chunky Li metal is formed in the Li@CF electrode after the deep stripping/plating pre-cycling,which effectively suppresses the volume expansion and dendritic formation.As a result,the thin Li@CF electrode not only exhibits a minimal voltage fluctuation and improved long-term cycling stability in symmetric cells,as well as delivers high reversible capacity,long cycle life,good rate performance in the Co-free layered oxide cathode-based Li metal batteries.We attribute the excellent electrochemical performance of the Li@CF composite anode to three key advantages:1)the homogeneous lithiophilic top layer drives the uniform adsorption of liquid Li on the lignin-based CF scaffold;2)the lithiophilic top layer guides evenly Li nucleation and mitigates the Li dendritic growth;3)the unique microstructure CF provides abundant space for sufficient electrolyte-electrode contact,stable electrolyte-electrode interphase and enables fast charge transfer for Li/Li+redox reactions.In summary,our study provides alternative strategies for tailoring the surface hydrophilicity and lithiophilicity of carbon materials and for designing stable,safe high-energy-density Li metal batteries. |
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