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.

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)).

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.

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.

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.

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.

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.

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.

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.

Regulate the chemical property of the carbon nanospheres layer modified on the surface of sodium metal anode to achieve high-load battery

The energy density of batteries can be increased by using high-load cathode material matched with sodium (Na) metal anode. However, the large polarization of the battery under such harsh conditions will promote the growth of Na dendrites and side reactions. Carbon materials are regarded as ideal modify layers on Na metal anode to regulate the Na+ plating/stripping behavior and inhibit the Na dendrites and side reactions due to their light weight, high stability and structural adjustability. However, commonly used carbon nanotubes and carbon nanofibers cannot enable these modified Na metal anodes to operate stably in full batteries with a high-load cathode (】15 mg·cm^(−2)). The most fundamental reason is that abundant polar functional groups on the surface bring serious side reactions and agglomerations lead to uneven Na+ flow. Here, a proof-of-concept study lies on fabrications of carbon nanospheres with small amount of polar functional groups and sodiophobic components on the surface of Na metal anode, which significantly enhances the uniformity of the Na+ plating/stripping. The assembled symmetric battery can cycle stability for 1300 h at 3 mA·cm^(−2)/3 mAh·cm^(−2). The full battery with high-load Na3V2(PO4)3 (30 mg·cm^(−2)) maintains a Coulombic efficiency of 99.7% after 100 cycles.

Asymmetric fireproof gel polymer electrolyte constructed by boron-contained covalent organic framework for dendrite-free sodium metal battery

Gel polymer electrolytes (GPEs) with flexibility, easy processability, and low cost have been regarded as promising alternatives for conventional liquid electrolytes in next-generation sodium metal batteries (SMBs). However, GPEs often suffer from combustion risk and inferior interfacial compatibility toward Na metal anode, which severely limit their wide commercial applications. Here, a rational design of asymmetric fireproof GPE (AFGPE) modified with a boron-contained covalent organic framework (BCOF) on one side is developed through in-situ crosslinking polymerization process. Benefiting from the unique structure and composition, the resulting AFGPE exhibits high Na+ transference number, wide electrochemical window, excellent mechanical properties and high safety. Especially, the nanoscale BCOF layer with uniform nanochannels works as ion sieve that homogenizes Na+ flux during Na plating process, while the abundant Lewis-acid B sites can strongly capture counter anions and decrease space charge layer at anode side, thus promoting the uniform Na deposition to effectively suppress dendrite growth. Consequently, the Na/AFGPE/Na symmetric cells demonstrate remarkable cycling stability for over 1200 h at 0.1 mA·cm^(-2), and the solid-state SMBs exhibit outstanding cycling properties and rate capability, delivering a high capacity retention of 96.4% under current density of 1 C for over 1000 cycles.

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.

A robust,highly reversible,mixed conducting sodium metal anode

Sodium metal anode holds great promise in pursuing high-energy and sustainable rechargeable batteries,but severely suffers from fatal dendrite growth accompanied with huge volume change.Herein,a robust mixed conducting sodium metal anode is designed through incorporating Na SICON-type solid Na-ion conductor into bulk Na.A fast and continuous pathway for simultaneous transportation of electrons and Na+is established throughout the composite anode.The intimate contact between Na-ion conducting phase and Na metallic phase constructs abundant two-phase boundaries for fast redox reactions.Further,the compact configuration of the composite anode substantially protects Na metal from being corroded by liquid organic electrolyte for the minimization of side reactions.Benefiting from the unique configuration,the composite anode shows highly reversible and durable Na plating/stripping behavior.The symmetric cells exhibit ultralong lifespan for over 700 h at 1 mA cm^(-2)with a high capacity of 5 m Ah cm^(-2)and outstanding rate capability up to 8 m A cm^(-2)in the carbonate electrolyte.Full cells with Na_(3)V_(2)(PO_(4))_(3)/C cathode demonstrate impressive cycling stability(capacity decay of 0.012%per cycle)and low charge/discharge polarization as well.This work provides new insights into rational design and development of robust sodium metal anode through an architecture engineering strategy for advanced rechargeable sodium batteries.

3D uniform nitrogen-doped carbon skeleton for ultra-stable sodium metal anode

Sodium metal batteries are arousing extensive interest owing to their high energy density,low cost and wide resource.However,the practical development of sodium metal batteries is inherently plagued by the severe volume expansion and the dendrite growth of sodium metal anode during long cycles under high current density.Herein,a simple electrospinning method is applied to construct the uniformly nitrogen-doped porous carbon fiber skeleton and used as three-dimensional(3D)current collector for sodium metal anode,which has high specific surface area(1,098 m^2/g)and strong binding to sodium metal.As a result,nitrogen-doped carbon fiber current collector shows a low sodium deposition overpotential and a highly stable cyclability for 3,500 h with a high coulombic effciency of 99.9%at 2 mA/cm^2 and 2 mAh/cm^2.Moreover,the full cells using carbon coated sodium vanadium phosphate as cathode and sodium pre-plated nitrogen-doped carbon fiber skeleton as hybrid anode can stably cycle for 300 times.These results illustrate an effective strategy to construct a 3D uniformly nitrogen-doped carbon skeleton based sodium metal hybrid anode without the formation of dendrites,which provide a prospect for further development and research of high performance sodium metal batteries.

Recent Progress and Perspectives of Sodium Metal Anodes for Rechargeable Batteries

Sodium metal anodes have attracted significant attention due to their high specific capacity,low redox potential and abundant resources.However,the dendrites and unstable solid electrolyte interphase(SEI)of sodium anodes restrict the development of sodium metal batteries.This review includes the recent progress on the Na anode protection in sodium metal batteries.The strategies are summarized as modified three-dimensional current collectors,artificial solid electrolyte interphases,and electrolyte modifications.Conclusions and perspectives are envisaged for the further understanding and development of Na metal anodes.

Sodium-rich NASICON-structured cathodes for boosting the energy density and lifespan of sodium-free-anode sodium metal batteries

Rechargeable sodium metal batteries(SMBs)have emerged as promising alternatives to commercial Li-ion batteries because of the natural abundance and low cost of sodium resources.However,the overuse of metallic sodium in conventional SMBs limits their energy densities and leads to severe safety concerns.Herein,we propose a sodium-free-anode SMB(SFA-SMB)configuration consisting of a sodium-rich Na superionic conductor-structured cathode and a bare Al/C current collector to address the above challenges.Sodiated Na_(3)V_(2)(PO_(4))_(3)in the form of Na_(5)V_(2)(PO_(4))_(3)was investigated as a cathode to provide a stable and controllable sodium source in the SFA-SMB.It provides not only remarkable Coulombic efficiencies of Na plating/stripping cycles but also a highly reversible three-electron redox reaction within 1.0–3.8 V versus Na/Na+confirmed by structural/electrochemical measurements.Consequently,an ultrahigh energy density of 400 Wh kg^(-1)was achieved for the SFA-SMB with fast Na storage kinetics and impressive capacity retention of 93%after 130 cycles.A narrowed voltage window(3.0–3.8 V vs.Na/Na+)further increased the lifespan to over 300 cycles with a high retained specific energy of 320 Wh kg^(-1).Therefore,the proposed SFA-SMB configuration opens a new avenue for fabricating next-generation batteries with high energy densities and long lifetimes.

Stable sodium metal anode enhanced by advanced electrolytes with SbF_(3) additive

The practical application of sodium metal batteries(SMBs)is hampered due to the inferior interfacial stability between Na metal and conventional electrolytes.Therefore,a high-concentration electrolyte is proposed to solve this issue.However,high viscosity,low ionic conductivity,and unsatisfactory wettability toward the separator need to be overcome.In this study,a localized highconcentration electrolyte(LHCE)is formulated with1 wt%SbF_(3)as an interface-stabilized additive to protect the Na metal anode.This reformulated LHCE retains the special coordination structure in HCE with improved wettability and high ionic conductivity.Moreover,the introduction of the SbF_(3)additive into the LHCE resulted in a bilayer-structured solid electrolyte interface(SEI)including a Na-Sb alloy inner layer and a NaF-rich outer layer on the Na metal.As expected,the NaIINa cells using LHCE+1 wt%SbF_(3)show a long cycle lifespan of over1200 h at 0.5 mA·cm^(-2)with negligible polarization,and NaIINa_(3)V_(2)(PO_(4))_(3)cells exhibit a high capacity exceeding 97 mAh·g^(-1)at 40 C.