Functional Carbon-based Materials:Structural Design And Application In Novel Batteries

Lithium-ion batteries(LIBs)have been widely applied in commercial applications in recent years.However,LIBs cannot meet the increasing demand for the rapid development of large-scale energy storage systems.To meet the needs of electric vehicles and smart grids for high energy density and large-scale applications,it is necessary to develop novel batteries with high energy density and low-cost.As one of the most promising alternatives to commercial LIBs,sodium-ion batteries(SIBs)have attracted extensive attention due to the abundance and low cost of sodium.At present,lithium-sulfur batteries and alkali metal batteries with low cost,high storage capacity and high energy density have received extensive attention.Herein,a series of functional carbon materials including graphene nanoscroll-based materials prepared by liquid nitrogen cold extraction and carbon nanofiber composites prepared by electrospinning were designed.The specific work are as follows:1.Li sulfur(Li-S)battery is regarded as one of the most promising candidates for next-generation rechargeable batteries.However,some challenging obstacles such as uncontrolled dendrites of Li metal anode and poly sulfides shuttling in sulfur cathode substantially impede the practical application.In this work,we proposed a versatile strategy of fabricating graphene nanoscroll(GNS)based bifunctional Janus polypropylene(Janus PP)separators for inhibiting lithium dendrites and suppressing polysulfides shuttling towards high performance Li-S batteries.On the anode side of separator,nitrogen-doped GNS(NGNS)were used to protect the lithium metal.The highly uniform NGNS nanostructure facilitated electrolyte penetration and homogenous Li+flux,thus fundamentally prompting lithiation/delithiation kinetics and inhibiting the growth of Li dendrites.Due to the virtues,the Li symmetrical cell with NGNS modified PP separator(NGNS-PP)delivers an ultralow voltage hysteresis of 36 mV at 6.0 mA cm-2 after 12000 h(65.5 mV at 10 mA cm-2 after 3400 h).On the cathode side,GNS wrapped Co3O4 nanoparticles(Co3O4@GNS)was used as an interlayer on PP separator,acting as a wonderful physical blocking and chemical catalytic layer to sufficiently mitigate the "shuttle effects" of lithium polysulfides.As a result,with the Janus PP separator,the Li-S cells obtain a stable capacity of 805 mA h g-1 after 800 cycles.Therefore,this proposed strategy of GNS based Janus separators will pave a new way to rationally construct durable and efficient Li-S batteries.2.Sodium-ion batteries(SIBs)have drawn much attention due to the abundance and low cost of sodium.However,electrode materials of SIBs displayed sluggish Na+diffusivity and fatal volume expansion,owing to the larger ionic radius of Na+ ions than Li+ions.In this work,we built the CoSe2 nanoparticles embedded in graphene nanoscrolls(GNS)as advanced anodes for high-rate SIBs.The CoSe2/C@GNS anodes exhibited a high reversible capacity of 545 mA hg-1 at 0.2 A g-1.Moreover,they showed an outstanding cycling stability of 455 mA h g-1 after 5000 cycles at 1 A g-1.The CoSe2/C@GNS anode also demonstrate ultrahigh rate capabilities(212.5 mA h g-1 at 50 A g-1).In addition,with a high mass loading(6 mg cm-2),the electrode still displayed a stable capacity(412 mA h g-1 1 A g-1).The fast electron transfer and Na+ion diffusion kinetics creates the excellent electrochemical properties,on account of the uniform arrangement of nanoparticles and unique reticular crosslinking structure of CoSe2/C@GNS.This strategy could also be constructed other electrode materials,which provides more probabilities for the development of SIBs.3.Sodium is one of the most promising alternatives to lithium as the anode material for next generation batteries.However,uneven Na nucleation and subsequent dendrite growth impedes its practical applications.Herein,a 3D framework consisted of N-doped carbon nanofibers(NCF)and MoS2 is designed to serves as the substrate for Na deposition.Density functional theory(DFT)calculations indicate the 2H-MoS2 and N-functional groups possess of strong sodiophilicity and can regulate the uniform distribution of Na.The MoS2 and N-functional groups contribute to the adsorption of Na+and the reduction of Na nucleation energy.Due to the low nucleation barrier enabled by 2H-MoS2 and pyridinic N-functional groups,high-loading Na can deposit uniformly on the surface of the MoS2/NCF skeleton.The cooperation of super sodiophilicity and eventual adsorption makes Na stripping/plating over 3000 cycles at 8 mA cm-2 with coulombic efficiency of 99.6%(8000 cycles at 2 mA cm-2).The symmetric MoS2@NCF/Na cells exhibited excellent cycling stability and stable hysteresis voltage(30.0 mV after 3000 cycles at 6 mA cm-2 with 3 mA h cm-2)and excellent rate performance(low overpotential of 120 mV at 20 mA cm-2).As a proof of concept,the full cells of MoS2@NCF/Na‖NVP@C also achieve exceptional improvement in cycling and rate performance.This work develops a promising strategy based on stable Na deposition for advanced high-performance sodium-metal batteries.4.Through the combination of DFT theoretical calculations,the sodiophilic Sb@NCF framework was rationally designed and synthesized by electrospinning.The Sb@NCF was used as artificial protective film of sodium metal battery.The introduction of elemental Sb and the co-existence of N functional groups enhanced the binding energy between the substrate and Na+and changed the behavior of Na+.It not only greatly promotes sodiophilicity,but also modulates the deposition behavior of Na ions along the carbon substrate direction,promoting the reaction kinetics and contributing to the dendrite-free structure.A self-supporting material with a 3D crosslinked structure and a network-like space obtained by electrospinning can accommodate a large amount of sodium ions and buffer abrupt volume changes during the stripping/plating process.It still provides good conductivity for fast transport of ions and electrons.It can effectively adjust the diffusion of Na+ when modifying sodium metal,and avoid the unevenness of local current and the appearance of sodium dendrites.Using sodium metal as the sodium source can supplement the consumption of sodium ions and alleviate the performance degradation caused by the inevitable side reactions with the electrolyte.Sufficient metallic sodium in the Sb@NCF-Na anode constantly replenishes the consumption caused by inevitable side reactions,thereby realizing the reduction of overpotential and the increase of cycle life of the symmetric battery.Compared with metallic sodium,this stable composite anode exhibits higher electrochemical performance and cycling stability in both full cells,opening a new avenue for practical application of next-generation high-energy SMBs.