| Promoting the dynamic storage and secondary deployment of clean energy is of vital importance for realizing the goal of peaking carbon dioxide emissions and carbon neutrality.Owing to the finite reserves and wildly fluctuating prices of Li,sodium with sufficient reserves and low price is deemed as promising candidate in the field of urban public transport and large-scale energy storage system to replace lithium ion batteries.However,the application of Sodium ion batteries（SIBs）still faces with several scientific issues.Na+ shows larger size and sluggish dynamics,which may induce severe lattice deformation among limited variety of anode materials,thus resulting in the destruction of original crystal structure and irreversible decay of electrochemical performance.In addition,the conventional liquid organic electrolytes generally possess undesired fluidity and flammability,which may lead to short-circuit,thermal runaway and potential burning hazards.Reduced graphene oxide aerogel（rGOA）,which shows stable 3D interconnected architecture,is deemed as excellent auxiliary for high performance electrodes to alleviate the volume expansion and improve the charge transfer dynamics.Moreover,the employment of inorganic solid-state electrolytes（SSEs）and high-capacity Na metal anodes as well as the interfacial modification between them can improve the cycling capacity and stability of SIBs simultaneously.In this case,the design of highperformance rGOA based SIB anodes and the modification of Na/SSE interface were precisely conducted respectively.Accompanied by the strategies of surface functionalization,3D heterostructure construction,interfacial structure design and organic-inorganic complex,the component and microstructure of crucial materials were investigated thoroughly to research Na+ transport/storage characteristics,mechanism and overall performance.The main research content includes the following five parts.（1）Under the surface activation of polyvinyl pyrrolidone（PVP）and sodium dodecyl benzene sulfonate（SDBS）,the monodispersed core-shell Ni（OH）2@PVP nanoparticles are homogenously embedded on the surface of 3D graphene aerogel（GA）nanosheets by a simple solvothermal reaction.After subsequent low-temperature phosphorization process,the unique Ni2P@C/GA composite anode is synthesized.The synergistic effect between core-shell structure and 3D aerogel architecture endows Ni2P@C/GA with superior electrochemical performance,retaining a reversible capacity of 124.5 mAh g-1 after 2000 cycles at a large current density of 1 A g-1.The interconnected 3D GA matrix with abundant open pores can provide abundant active sites and facilitate electrolyte penetration,thus improving the electrode/electrolyte contact area and enhancing the electrochemical reaction dynamics.The carbon layer and GA architecture together build an interconnected matrix,which not only facilitates charge transfer processes,but also prevent Ni2P nanoparticles from aggregation and pulverization as well as tolerates the volume expansion during cycling.（2）The active functional groups on graphene oxide（GO）substrates can be modulated by pre-controlling the gelation degree of GO,which can in-situ regulate the active materials growth process on the substrates due to Ostwald ripening.Meanwhile,the formation of 3D aerogel architecture can be modulated at the same time.The dispersed CoSn（OH）6 nanoparticles are adjusted to be large-quantity but with small particle size.After subsequent thermal treatment process,the optimized SnO2/Co2SnO4@rGOA-10 composite is obtained,showing improved electrochemical performance when used as SIBs anodes.Benefitting from the synergistic effect between improved structural stability and kinetics,it shows superior property of 193.6 mAh g-1 after 1000 cycles at 0.1 A g-1.The 3D rGOA matrix with abundant open pores can provide unblocked channels for electrolyte penetration and simultaneously,improve the conductivity of the hybrids.The decrease of particle size can not only alleviate volume expansion to maintain excellent structural stability,but also shorten Na+/e-transfer route within the bulk phase to promote electrochemical dynamics,thus improving the cycling performance of obtained composite anodes.（3）The AlF3 coating layer with high band gap is modified on the surface of Na super ionic conductor（NASICON）SSE through facile spin-coating and sintering processes.Profiting from the intimate modification,the interfacial wettability between the SSE and Na metal anode is extremely ameliorated,thus improving the contact area and decreasing the interfacial impedance.The dendrites resistant ability of SSE is highly strengthened,with the critical current density of Na/AlF3-NASICON/Na cells multiplying three-fold to 1.2 mA cm-2 at 60℃,and can operate up to 300 h without short-circuit.The intimate modification can avoid the contact of intrinsic defects on NASICON surface with Na,and the critical dendrites length is further enlarged due to the increased interfacial energy between AlF3-induced interlayer and Na anode.In addition,the reaction between AlF3 and Na possesses typical "overpotential triggering"character.Locally agminated e-at Na/SSE interface or enlarged overpotential will preferentially drive more Na+ to react with residual AlF3 instead of forming dendrites,thus improving the cycling stability at large current density.（4）The Na dendrites distribution characteristics and propagation mechanisms among solid-state SIBs are comprehensively researched,revealing that violent spalling,straight,branching,and gathering-types Na dendrites are extensively distributed among cycled SSEs,together leading to short-circuits of the batteries.Based on the structural instability of ZIF-62 induced by the composed competitive ligands,a new route is developed to in-situ prepare compact and uniform ZnO-N/C coating layer on NASICON surface through direct derivation of continuous monophasic liquid metal organic frameworks precursor,not interfering with intermediate recrystallization.The interlayer can highly improve the interfacial compatibility with Na anode and homogenize interfacial transported e-/Na+,thus leading to lateral flat-shape Na deposition/exfoliation process.Meanwhile,it possesses superior sodiophilicity and can relieve generated stress/strain,which can help to maintain interfacial stability during cycling.The assembled Na symmetric batteries demonstrate highly improved cycling stability,and the integrated full cells with NVP cathodes show a specific capacity of 91.3 mAh g-1 after 500 cycles at 1 C.（5）With the help of introducing S to trigger the dehydrogenation and cyclization of polyacrylonitrile（PAN）,the favorable isotropous sulfurized polyacrylonitrile（SPAN）interlayer is modified on the surface of NASICON SSE through a scalable powderpolishing method.The interfacial compatibility with Na anode is highly improved with the flexible organosulfur modification.Electrochemical impedance spectroscopy（EIS）,cyclic voltammetry（CV）and galvanostatic intermittent titration technique（GITT）measurements further prove that SPAN shows excellent Na+ diffusion performance.The chemically-bonded short-chain S-S segments can connect with transported Na+easily to homogenize interfacial Na+/e-flux,making interfacial Na deposition behavior transform from vertical dendrite mode to lateral flat-shape tendency.Meanwhile,the polymer backbones possess delocalized radicals that can activate formed short-chain sulfides to reconnect to the backbones during cycling,thus maintaining superior structural stability.The assembled Na/SPAN-NASICON/Na cells demonstrate high critical current density of 1.4 mA cm-2,and the full cells with both NVP and SPAN cathodes demonstrate superior cycling performance with good application prospects. |
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