Na_(3)P interphase reduces Na nucleation energy enabling stable anode-less sodium metal batteries

Sodium metal batteries(SMBs)are rising as viable alternatives to lithium-ion systems due to their superior energy density and sodium's relative abundance.However,SMBs face significant impediments,particularly the exceedingly high negative-to-positive capacity ratios(N/P ratios)which severely encumber energy density and hinder their practical application.Herein,a novel nucleophilic Na_(3)P interphase on aluminum foil has been designed to significantly lower the nucleation energy barrier for sodium atom deposition,resulting in a remarkable reduction of nucleation overpotential and efficient mitigation of dendritic growth at high sodium deposition of 5 mA h cm^(−2).The interphase promotes stable cycling in anode-less SMB configurations with a low N/P ratio of 1.4 and high cathode mass loading of 11.5 mg cm^(−2),and demonstrates a substantial increase in high capacity retention of 92.4%after 500 cycles even under 1 C rate condition.This innovation signifies a promising leap forward in the development of high-energy-density,anode-less SMBs,offering a potential solution to the longstanding issues of cycle stability and energy efficiency.

Atomically bonding Na anodes with metallized ceramic electrolytes by ultrasound welding for high-energy/power solid-state sodium metal batteries

A solid-state sodium metal battery has cut a striking figure in next-generation large-scale energy storage technology on account of high safety,high energy density,and low cost.Nevertheless,the large interfacial resistance and sodium dendrite growth originating from the poor interface contact seriously hinder its practical application.Herein,a modified ultrasound welding was proposed to atomically bond Na anodes and Au-metalized Na_(3)Zr_(2)Si_(2)PO_(12) electrolytes associated with the in situ formation of Na–Au alloy interlayers.Thereupon,intimate Na_(3)Zr_(2)Si_(2)PO_(12)-Au/Na interfaces with a low interfacial resistance(~23Ωcm^(2))and a strong dendrite inhibition ability were constructed.The optimized Na symmetric battery can cycle steadily for more than 900 h at 0.3 mA cm^(-2) under a low overpotential(<50 mV)of Na electroplating/stripping and deliver a high critical current density of 0.8 mAcm^(-2) at room temperature.By incorporating the above interface into the solid-state Na metal battery,taking three-dimensional Na_(3)V_(2)(PO_(4))_(3) as the cathode,the full battery offers a high energy density of 291 Wh kg^(-1) at a high power density of 1860Wkg^(-1).A pouch-type solid-state sodium metal full battery based on a ceramic electrolyte was assembled for the first time,and it lit a 3 V LED lamp.Such a strategy of the ultrasound welding metalized solid-state electrolyte/Na interface by engineering the Na-Au interlayer would pave a new pathway to engineer a low-resistance and highly stable interface for high-energy/density solid-state sodium metal batteries.

Recent advanced development of stabilizing sodium metal anodes

As the application of next-generation energy storage systems continues to expand,rechargeable secondary batteries with enhanced energy density and safety are imperative for energy iteration.Sodium-ion batteries(SIBs)have attracted extensive attention and are recognized as ideal candidates for large-scale energy storage due to the abundant sodium resources and low cost.Sodium metal anodes(SMAs)have been considered as one of the most attractive anode materials for SIBs owing to their high specific capacity(1166 mAh g^(-1)),low redox potential,and abundant natural resources.However,the uncontrollable dendrite growth and inevitable side reactions on SMA lead to the continuous deterioration of the electrochemical performance,causing serious safety concerns and limiting their practical application in the future.Therefore,the construction of stable dendrite-free SMAs is a pressing problem for advanced sodium metal batteries(SMBs).In this review,we comprehensively summarize the research progress in suppressing the formation of sodium dendrite,including artificial solid electrolyte interphase(SEI),liquid electrolyte modification,three-dimensional(3D)host materials,and solid-state electrolyte.Additionally,key aspects and prospects of future research directions for SMAs are highlighted.We hope that this timely review can provide an overall picture of sodium protection strategies and stimulate more research in the future.

Stable sodium anodes for sodium metal batteries(SMBs) enabled by in-situ formed quasi solid-state polymer electrolyte

A high-performance quasi-solid polymer electrolyte for sodium metal batteries(SMBs)based on in-situ polymerized poly(1,3-dioxolane)(DOL)with 20%volume ratio of fluoroethylene carbonate(FEC),termed"PDFE-20",is proposed in this work.It is demonstrated PDFE-20 possesses a room-temperature ionic conductivity of 3.31×10^(-3) S cm^(-1),an ionic diffusion activation energy of 0.10 eV,and an oxidation potential of 4.4 V.SMBs based on PDFE-20 and Na_(3)V_(2)(PO_(4))_(3)(NVP)cathodes were evaluated with an active material mass loading of 6.8 mg cm^(-2).The cell displayed an initial discharge specific capacity of 104 mA h g^(-1),and97.1%capacity retention after 100 cycles at 0.5 C.In-situ polymerization conformally coats the anode/-cathode interfaces,avoiding geometrical gaps and high charge transfer resistance with ex-situ polymerization of the same chemistry.FEC acts as a plasticizer during polymerization to suppress crystallization and significantly improves ionic transport.During battery cycling FEC promotes mechanical congruence of electrolyte-electrode interfaces while forming a stable NaF-rich solid electrolyte interphase(SEI)at the anode.Density functional theory(DFT)calculations were also performed to further understand the role FEC in the poly(DOL)-FEC electrolytes.This work broadens the application of in-situ prepared poly(DOL)electrolytes to sodium storage and demonstrates the crucial role of FEC in improving the electrochemical performance.

Rationalizing Na-ion solvation structure by weakening carbonate solvent coordination ability for high-voltage sodium metal batteries

Commercial carbonate-based electrolytes feature highly reactive activities with alkali metals,yielding low Coulombic efficiencies and poor cycle life in lithium metal batteries,which possess much higher chemical activity in the rising star sodium metal batteries.To be motivated,we have proposed that decreasing the solvent solvation ability in carbonate-based electrolytes stepwise could enable longterm stable cycling of high-voltage sodium metal batteries.As the solvation capacity reduces,more anions are enticed into the solvation sheath of Na^(+),resulting in the formation of the more desirable interphase layers on the surface of the anode and the cathode.The inorganic-dominated interphases allow highly efficient Na^(+)deposition/stripping processes with a lower rate of dead sodium generation,as well as maintain a stable structure of the high-voltage cathode material.Specifically,the assembled Na||Na_(3)V_(2)(PO_(4))_(2)F_(3)battery exhibits an accelerated ion diffusion kinetics and achieves a higher capacity retention of 85.9%with during the consecutive 200 cycles under the high voltage of 4.5 V.It is anticipated that the tactics we have proposed could be applicable in other secondary metal battery systems as well.

Uniform nanoplating of metallic magnesium film on titanium dioxide nanotubes as a skeleton for reversible Na metal anode

To meet the low-cost concept advocated by the sodium metal anode,this paper reports the use of a pulsed electrodeposition technology with ionic liquids as electrolytes to achieve uniform nanoplating of metallic magnesium films at around 20 nm on spaced titanium dioxide(TiO_(2))nanotubes(STNA-Mg).First,the sodiophilic magnesium metal coating can effectively reduce the nucleation overpotential of sodium metal.Moreover,three-dimensional STNA can limit the volume expansion during sodium metal plating and stripping to achieve the ultrastable deposition and stripping of sodium metals with a high Coulombic efficiency of up to 99.5%and a small voltage polarization of 5 mV in symmetric Na||Na batteries.In addition,the comparative study of sodium metal deposition behavior of STNA-Mg and STNA-Cu prepared by the same route further confirmed the advantage of magnesium metal to guide sodium metal growth.Finally,the prepared STNA-Mg-Na metal anode and commercial sodium vanadium phosphate cathode were assembled into a full cell,delivering a discharge capacity of 110.2 mAh·g^(-1)with a retention rate of 95.6%after 110 cycles at 1C rate.

A stable anthraquinone-derivative cathode to develop sodium metal batteries: The role of ammoniates as electrolytes

Rechargeable sodium metal batteries constitute a cost-effective option for energy storage although sodium shows some drawbacks in terms of reactivity with organic solvents and dendritic growth.Here we demonstrate that an organic dye,indanthrone blue,behaves as an efficient cathode material for the development of secondary sodium metal batteries when combined with novel inorganic electrolytes.These electrolytes are ammonia solvates,known as liquid ammoniates,which can be formulated as NaI·3.3NH_(3) and NaBF_(4)·2.5NH_(3).They impart excellent stability to sodium metal,and they favor sodium non-dendritic growth linked to their exceedingly high sodium ion concentration.This advantage is complemented by a high specific conductivity.The battery described here can last hundreds of cycles at 10 C while keeping a Coulombic efficiency of 99%from the first cycle.Because of the high capacity of the cathode and the superior physicochemical properties of the electrolytes,the battery can reach a specific energy value as high as 210 W h kgIB^(-1),and a high specific power of 2.2 kW kgIB^(-1),even at below room temperature(4℃).Importantly,the battery is based on abundant and cost-effective materials,bearing promise for its application in large-scale energy storage.

Pre-sodiation strategy for superior sodium storage batteries

The irreversible consumption of sodium in the initial several cycles greatly led to the attenuation of capacity,which caused the low initial coulombic efficiency(ICE)and obvious poor cycle stability.Presodiation can effectively improve the electrochemical performance by compensating the capacity loss in the initial cycle.Here,carbon-coated sodium-pretreated iron disulfide(NaFeS_(2)@C)has been synthesized through conventional chemical method and used in sodium metal battery as a cathode material.The calculated density of states(DOS)of NaFeS2@C is higher,which implies enhanced electron mobility and improved cycle reversibility.Because of the highly reversible conversion reaction and the compensation of irreversible capacity loss during the initial cycle,the Na/NaFeS_(2)@C battery achieves ultrahigh initial coulombic efficiency(96.7%)and remarkable capacity(751 mA·h·g^(-1) at 0.1 A·g^(-1)).In addition,highly reversible electrochemical reactions and ultra-thin NaF-rich solid electrolyte interphase(SEI)also benefit for the electrochemical performance,even at high current density of 100 A·g^(-1),it still exhibits a reversible capacity of 136 mA·h·g^(-1),and 343 mA·h·g^(-1) after 2500 cycles at 5.0 A·g^(-1).This work aims to bring up new insights to improve the ICE and stability of sodium metal batteries.

Stabilizing sodium metal anode through facile construction of organicmetal interface

Implementation of sodium metal anode is highly desired for sodium batteries due to its high theoretical capacity and low redox potential.Unfortunately,formation of unstable solid electrolyte interphase(SEI)and uncontrollable growth of dendrites during charge/discharge cycles greatly hinder the practical application of sodium metal anode.In this study,an organic-metal artificial layer made of PVdF and Bi was constructed to protect Cu current collector via a facile coating method,leading to smooth and dense sodium plating/stripping,which in retern enables stable cycling and high coulombic efficiency(CE).At 1 mA cm^(−2),PB@Cu current collector presents extended lifetime of~2500 h with high sodium utilization of 50%,which is approximately six times higher than Cu current collector.PB@Cu electrode also displays high average CE of 99.92%and 99.95%over 2500 and 1300 cycles at 1 and 2 mA cm^(−2) respectively,which is in sharp contrast to the low and tremendously fluctuant CE gained from bare Cu electrode.Moreover,stable capacity of>90 mAh g^(−1) over 150 cycles is realized for PB@Cu-based full cell assembled with NVP cathode at a low negative-positive capacity ratio of~3.5,which is significantly higher than 37.2 mAh g^(−1) obtained from NVP/Cu at 150th cycle.The superior electrochemical performance of PB@Cu current collector is revealed to originate from the alloyed Na_(3)Bi phase with high sodium conductivity and robust mechanical strength as well as the formation of NaF-rich SEI with fast sodium ion migration,which enable dendrite-free morphology during plating/stripping cycles.

Engineering Sodium Metal Anode with Sodiophilic Bismuthide Penetration for Dendrite-Free and High-Rate Sodium-Ion Battery

Sodium(Na)metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable.However,an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of sodium during high-rate plating/stripping behaviors,followed by severe dendrite growth and loose stacking.Herein,we engineer the Na hybrid anode with sodiophilic Na_(3)Bi-penetration to develop the abundant phase-boundary ionic transport channels.Compared to intrinsic Na,the reduced adsorption energy and ion-diffusion barrier on Na_(3)Bi ensure even Na^(+)nucleation and rapid Na^(+)migration within the hybrid electrode,leading to uniform deposition and dissolution at high current densities.Furthermore,the bismuthide enables compact Na deposition within the sodiophilic framework during cycling,thus favoring a high volumetric capacity.Consequently,the obtained anode was endowed with a high current density(up to 5 mA∙cm^(−2)),high areal capacity(up to 5 mA∙h∙cm^(−2)),and long-term cycling stability(up to 2800 h at 2 mA∙cm^(−2)).

Enabling stable sodium metal cycling by sodiophilic interphase in a polymer electrolyte system

Enabling highly reversible sodium(Na) metal anodes in a polymer electrolyte(PE) system is critical for realizing next-generation batteries with lower cost,higher energy,and improved safety.However,the uneven Na deposition and high Na/PE interphase resistance lead to poor reversibility and short cycle life of Na metal anodes.To tackle these problems,here a variety of metal nanoparticles(M-np,M=Al,Sn,In or Au) are deposited onto copper(Cu) foils to synthesize binder-free M-np@Cu substrates for Na plating/stripping.Notably,the Au-np@Cu substrate provides abundant preferential nucleation/growth sites,decreasing Na nucleation barrier and thus promoting uniform Na deposition.Accordingly,stable Na metal anodes are achieved with high reversible capacities,long cycle life,and high usage of Na.With the Au-np@Cu/Na anode and PE,the full cell using a commercial bulk sulfur cathode exhibits a reversible capacity of>400 mAh g^(-1) with near-100% Coulombic efficiency over 200 cycles.

Sodiophilic skeleton based on the packing of hard carbon microspheres for stable sodium metal anode without dead sodium

The propensity of metallic Na dendrites from uneven electrodeposits and the low Coulombic efficiency due to the inevitable existence of "dead sodium" are crucial barriers to realizing the Na metal anode.Herein,we report a multifunctional sodiophilic skeleton based on the packing of hard carbon(HC)microspheres for stable sodium metal electrodeposition without "dead sodium".Firstly,HC is sodiophilic substrate due to the intrinsic heteroatoms or defects which is a favor for the nucleation of Na.Secondly,silver nanoparticles electroplating on HC(Ag-HC)was adopted to boost the Na diffusion and further regulate the uniform Na metal epitaxial deposition due to well compatibility with AIMD simulation.Finally,the packing of HC microspheres provides the inner space for Na plating.Importantly,it was first found by Cryo-TEM that Na metal deposition in nanoscale is achieved by oriented attachment along[110]direction,leading to the formation of polycrystalline Na metal film on Ag-HC.Such epitaxial deposition can efficiently reduce the formation of "dead sodium" as revealed by chromatography tests,allowing the high Coulombic efficiency and good cycling stability robust kinetics.Finally,HC-Ag||Na_(3)V_(2)(PO_(4))_(3)full cell with a low negative/positive ratio of 0.6 is firstly achieved and displays good cycling stability.This finding provides a new practical strategy without pre-plating of Na metals and demonstrates a highly reversible polycrystalline Na metal anode toward a high-energy Na-based battery.

Sodiophilicity/potassiophilicity chemistry in sodium/potassium metal anodes

Heteroatom-doped carbon materials have been widely used as sodium(Na) and potassium(K) metal anode frameworks to achieve uniform Na and K depositions. If the origin of the Sodiophilicity and potassiophilicity of doping sites in heteroatom-doped carbon host are clearly understood, the nucleation and growth behavior of Na and K can be precisely regulated in working batteries. Herein the Sodiophilicity and potassiophilicity chemistries of carbon materials are probed through first-principles calculations. The local dipole of doping functional groups and charge transfer during Na/K deposition are regarded as key principles to reveal the sodiophilic and potassiophilic nature of doping sites. Especially, O–B, O–S, and O–P co-doping strategy are predicted to be effective methods to improve the Sodiophilicity and potassiophilicity of carbon hosts and thus render safe and dendrite-free Na and K metal anodes. This work affords a deep and insightful understanding of Sodiophilicity and potassiophilicity chemistry of Na and K anodes and establishes general principles of designing highly sodiophilic and potassiophilic carbon frameworks.

An in-situ generated Bi-based sodiophilic substrate with high structural stability for high-performance sodium metal batteries

Sodium(Na)metal anode exhibits a potential candidate in next-generation rechargeable batteries owing to its advantages of high earth abundance and low cost.Unfortunately,the practical development of sodium metal batteries is inherently plagued by challenges such as the side reactions and the growth of Na dendrites.Herein we report a highly stable Bi-based“sodiophilic”substrate to stabilize Na anode,which is created by in-situ electrochemical reactions of 3D hierarchical porous Bi_(2)MoO_(6)(BMO)microspheres.BMO is initially transformed into the Bi“nanoseeds”embedded in the Na-Mo-O matrix.Subsequently,the Bi nanoseeds working as preferential nucleation sites through the formation of BiNa alloy enable the non-dendritic Na deposition.The asymmetric cells based on such BMO-based substrate can deliver a long-term cycling for 600 cycles at a large capacity of 4 m Ah cm^(-2) and for 800 cycles at a high current density of 10 m A cm^(-2).Even at a high depth of discharge(66.67%),the Na-predeposited BMO(Na@BMO)electrodes can cycle for more than 1600 h.The limited Na@BMO anodes coupled with the Na_(3)V_(2)(PO_(4))_(3) cathodes(N/P ratio of 3)in full cells also show excellent electrochemical performance with a capacity retention of about 97.4%after 1100 cycles at 2 C.

Achieving high-performance sodium metal anodes: From structural design to reaction kinetic improvement

Sodium metal is one of the ideal anodes for high-performance rechargeable batteries because of its high specific capacity(~1166 mAh·g^(-1)),low reduction potential(-2.71 V compared to standard hydrogen electrodes),and low cost.However,the unstable solid electrolyte interphase,uncontrolled dendrite growth,and inevitable volume expansion hinder the practical application of sodium metal anodes.At present,many strategies have been developed to achieve stable sodium metal anodes.Here,we systematically summarize the latest strategies adopted in interface engineering,current collector design,and the emerging methods to improve the reaction kinetics of sodium deposition processes.First,the strategies of constructing protective layers are reviewed,including inorganic,organic,and mixed protective layers through electrolyte additives or pretreatments.Then,the classification of metal-based,carbon-based,and composite porous frames is discussed,including their function in reducing local deposition current density and the effect of introducing sodiophilic sites.Third,the recent progress of alloys,nanoparticles,and single atoms in improving Na deposition kinetics is systematically reviewed.Finally,the future research direction and the prospect of high-performance sodium metal batteries are proposed.

Rechargeable Na-MnO_(2) battery with modified cell chemistry

High voltage,high energy density,nominal cycle life,and low cost are the most critical requirements of rechargeable batteries for their widespread energy storage applications in electric vehicles and renewable energy technologies.Na-MnO_(2) battery could be a low-cost contender,but it suffers extensively from its low cell voltage and poor rechargeability.In this study,we modified the conventional cell structure of Na-MnO_(2) battery and established altered cell chemistry through a hybrid electrochemical process consisting of Na striping/plating at the anode and Zn^(2+) insertion/de-insertion along with MnO_(2) dissolution/deposition at the cathode.After the modification,Na-MnO_(2) battery exhibits a discharge capacity of 267.10 mA h/g and a cell voltage of 3.30 V(vs.Na/Na^(+)),resulting in a high specific energy density of 881.43 Wh/kg.After 300 cycles,the battery retains 98% of its first-cycle discharge capacity with100% coulombic efficiency.Besides,Na metal-free battery assembled using sodium biphenyl as a safer anode also delivers an excellent energy density of 810.0 Wh/kg.This work could provide a feasible method to develop an advanced Na-MnO_(2) battery for real-time energy storage applications.

Affinity-Engineered Flexible Scaffold toward Energy-Dense, Highly Reversible Na Metal Batteries

The practical deployment of metallic anodes in the energy-dense batteries is impeded by the thermodynamically unstable interphase in contact with the aprotic electrolyte,structural collapse of the substrates as well as their insufficient affinity toward the metallic deposits.Herein,the mechanical flexible,lightweight(1.2 mg cm^(−2))carbon nanofiber scaffold with the monodispersed,ultrafine Sn_(4)P_(3) nanoparticles encapsulation(Sn_(4)P_(3)NPs@CNF)is proposed as the deposition substrate toward the high-areal-capacity sodium loadings up to 4 mAh cm^(−2).First-principles calculations manifest that the alloy intermediates,namely the Na_(15)Sn_(4) and Na_(3)P matrix,exhibit the intimate Na affinity as the“sodiophilic”sites.Meanwhile,the porous CNF regulates the heterogeneous alloying process and confines the deposit propagation along the nanofiber orientation.With the precise control of pairing mode with the NaVPO4F cathode(8.7 mg cm^(−2)),the practical feasibility of the Sn_(4)P_(3) NPs@CNF anode(1^(*)Na excess)is demonstrated in 2 mAh single-layer pouch cell prototype,which achieves the 95.7%capacity retention for 150 cycles at various mechanical flexing states as well as balanced energy/power densities.

Sodium metals for single emitter strong coupling:Alternative plasmonic candidates beyond noble metals

This work provides a theoretical investigation into the strong coupling between a single quantum emitter(QE)and the surface plasmons of sodium metals in two representative plasmonic systems,i.e.,the semi-infinite metal-dielectric interface and the metal nanoparticles(NPs)of monomer/dimer configuration.In both configurations,sodium metals exhibit distinctly stronger coupling strength and lower optical loss in the optical region than their noble metal counterparts,demonstrating the ideal candidate characteristics for single-molecule-level strong couplings with distinctly facile operation conditions.Our results provide new insights into extreme light-matter interactions with potential applications in quantum information,optical sensors,quantum chemistry,etc.

In-plane isotropic separator-induced highly efficient sodium plating for unlocking the fast-charging capability of anode-free sodium battery at practical conditions

Ether-based electrolytes with excellent reductive stability are compatible with sodium(Na)metal an-odes,which enables stable cycling for Na metal batteries even in an anode-free configuration.However,the practical applications of anode-free sodium batteries(AFSBs)with a high theoretical energy density are restricted by the low-rate capability and limited cycle life.Here we demonstrate that the mechanical properties of the separators,which have been overlooked in previous studies,can significantly affect the cycling stability of AFSBs due to the intrinsic softness of Na and the large volume variation of AFSBs during Na plating/stripping.By using various separators including polypropylene(PP),polyethylene(PE),PP/PE/PP tri-layer,and aluminum oxide-coated separators,we find that the balanced elastic moduli of the separator along the machine direction and transverse direction are crucial for enabling highly effi-cient Na plating and unlocking the 4 C fast-charging capability of the AFSBs at practical conditions including a high cathode active mass loading(13.5 mg/cm^(2)),lean electrolyte addition(8.8 mL/cm^(2)),and no pre-sodiation process.This study provides an important separator design principle for the develop-ment of high-rate and long-cycle-life AFSBs.

A new approach for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid without using transition metal catalysts

The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.