N/S Doped Porous Carbon Materials Derived From Biomass And Their Lithium/sodium Storage Performance

In various energy development strategies,electrochemical energy is currently the most promising energy storage device,and lithium-ion batteries?LIBs?are particularly outstanding.With the increasing demand of various electronic devices,LIBs have been widely used in portable electronics,electric vehicles and renewable energy reserves.LIBs are playing an increasingly prominent role in social life and production.The demand of lithium resources is bound to increase,which will inevitably push up the prices of related raw materials and the cost of batteries,which is not conducive to the development of new energy industries.Sodium and lithium are the same main group elements,which have similar physical and chemical properties.Sodium is relatively abundant in the crust and its price is much lower than that of lithium raw materials.Therefore,the development of high performance sodium ion batteries?SIBs?to make up for the shortcomings of LIBs possesses important application value and practical significance.In the study,we demonstrate a simple and general high temperature activation method to prepare three-dimensional porous carbon materials with bagasse,wheat straw and wood shavings as biomass carbon sources.The materials have not only macroporous structures,but also a lot of mesoporous and microporous structures.Hierarchical porous structures are formed via macroporous bridging,providing channels and locuses for lithium-ion storage,in that improves battery performance.As anode materials of LIBs,they exhibit high specific capacity,amazing capability and stable cycling performance.For example,the sample obtained from bagasse at 800?can remain 325 mAh g^-1 after 100 cycles in an current density of 0.1 A g^-1.N-doped biomass-derived porous carbon?N/C?with a 3D framework and large specific surface area was obtained by carbonizing bagasse biomass waste with melamine as nitrogen source.The obtained N/C has macroporous structures,rich mesoporous and microporous structures.The multi-grade pore structure can not only increase the specific surface area,but also effectively provide multi-layer electron transmission channels.N-doping can greatly enhance the interaction between anchor sites and lithium ions,because it can alter local electron density,which is conducive to lithium-ion adsorption and anchoring.As anode of LIBs,it exhibits excellent reversible specific capacity of 530 mAh g^-1 at 0.1 A g^-1 after 100cycles.Furthermore,this study demonstrates the employment of natural waste material as a potential anode for LIBs,which will definitively make a strike in the energy storage field.Sulfur-doped honeycomb-like 3D porous carbon from bagasse waste has been efficiently obtained through a simple,economically feasible and environmentally friendly approach.The honeycomb-like 3D porous carbon possesses a unique porous structure with the co-existence of macro-,meso-and micropore structure which can afford facile storage and transport channels for both Li and Na ions.It is well characterized using X-ray diffraction?XRD?,Field Emission Scanning Electron Microscopy?FE-SEM?,Transmission electron Microscopy?TEM?,High resolution TEM?HR-TEM?and X-ray photoelectron spectroscopy?XPS?.As anode of LIBs,it can deliver superior electrochemical reversible specific capacity(690.9 mAh g^-1 at the current density of 0.1 A g^-1 after 100 cycles and 229 mAh g^-1 after 500 cycles at a high current density of 5 A g^-1.)When used as anode material of SIBs,it exhibits excellent reversible specific capacity of 505.8 mAh g^-1 at 0.1 A g^-1 after 100 cycles and 108 mAh g^-1 at5 A g^-1 after 500 cycles.Furthermore,this study demonstrates a facile strategy to synthesize sulfur-doped honeycomb-like 3D porous carbon from natural waste material with excellent electrochemical performance in both LIBs and SIBs.Nitrogen/sulfur co-doped disordered porous biocarbon was facilely synthesized and applied as anode material for LIBs and SIBs.Benefiting from high nitrogen?3.38 wt%?and sulfur?9.75 wt%?doping,NS_1-1 as anode materials showed a high reversible capacity of1010.4 mAh g^-1 at 0.1 A g^-1 in lithium ion batteries.In addition,it also exhibited excellent cycling stability,which can maintain at 412 mAh g^-1 after 1000 cycles at 5 A g^-1.As anode material of SIBs,NS_1-1 can still reach 745.2 mAh g^-1 at 100 mA g^-1 after 100 cycles.At a high current density(5 A g^-1),the reversible capacity is 272.5 mAh g^-1 after 1000 cycles,which exhibits excellent electrochemical performance and cycle stability.The preeminent electrochemical performance can be attributed to three effects:?1?the high level of sulfur and nitrogen;?2?the synergic effect of dual-doping heteroatoms;?3?the large quantity of edge defects and abundant micropores and mesopores,providing extra Li/Na storage regions.This disordered porous biocarbon co-doped with nitrogen/sulfur exhibits unique features,which is very suitable for anode materials of LIBs and SIBs.