| High-energy-density Li-S batteries are considered as a promising next-generation energy-storage system.However,the sluggish redox kinetics and severe polysulfide shuttle effect in elemental sulfur cathodes,along with uncontrollable dendrite propagation in lithium metal anodes inevitably depress the electrochemical performance of Li-S batteries and impede their practical implementation.Motivated by unique hierarchical geometry,specific chemical affinity,and nitrogen-enriched collagen component of natural skin collagen fibers,here we proposed an effective structural engineering strategy for crafting collagen fibers-derived multifunctional integrated S or Li hosts to simultaneously address the challenges faced on the sulfur cathode and lithium anode in LSBs.The specific research content is as follows:（1）Collagen fibers,a natural biological macromolecule with a one-dimensional（1D）hierarchical fiber structure,was designed and constructed for porous carbon fibers with a regular fiber structure and high specific surface area relying on its unique functional group to react with metal ions.Realize the high-efficiency load of active material sulfur inside the carbon fiber pores,and finally prepare high-power,long-life,low-cost lithium-sulfur battery cathode materials.（2）Relying on unique hierarchical geometry of skin collagen fibers together with their high chemical affinity to multivalent metal cations,novel skin collagen fibers-derived nanocomposites composed of Ni nanoparticles/graphitic carbon nanocages co-embedded superhierarchical N-doped porous carbon nanofiber bundles（Ni/GCNs（?）N-PCFs）were successfully synthesized.Benefiting from high-surface-area micro-/mesoporous structure,highly graphitic carbon nanocages,and Ni/N-heteroatom co-enhanced surface polarity,as validated by theoretical calculation and experiment results,the as-developed Ni/GCNs（?）N-PCFs not only provides synergistic physical/chemical confinement of soluble polysulfides,but also exerts a catalytic effect to promote their fast redox reactions both at room and elevated temperature.Besides,the well-distributed electronegative N atoms with extra electrons transferred from Ni nanoparticles in the Ni/GCNs（?）N-PCFs host framework can greatly increase the surface lithiophilicity to reduce the Li nucleation overpotential and favor a highly reversible lithium stripping/plating as well as yield homogeneous dendrite-free Li deposition.On the basis,a full lithium-sulfur cell configuration is further engineered benefiting from the well-designed cathode and anode,which shows remarkably enhanced rate capability(5 C,555 m Ah g-1)and good cycling performance.（3）A conductive composite architecture that is made up of bio-derived N-doped porous carbon fiber bundles（N-PCFs）with co-imbedded cobalt and niobium carbide nanoparticles（Nb C/Co（?）N-PCFs）are employed as a multifunctional integrated host for simultaneously addressing the challenges on both Li anode and S cathode.The implantation of Co and Nb C nanoparticles bestows the N-PCFs matrix with synergistically enhanced graphitization degree,electrical conductivity,hierarchical porosity,and surface polarization.Theoretical calculations and experimental results unveil that Nb C with specific lithiophilic and sulfiphilic features can synchronously regulate the Li and S electrochemistry by realizing homogeneous lithium deposition with suppressed Li-dendrite growth and exerting catalytic effect for promoting the polysulfide conversion together with fast Li2S nucleation.Hence,the assembled Li-S full batteries exhibit superb rate capability(704 m Ah g-1 at 5 C)and cycling life（～82.3%capacity retention after 500cycles）at sulfur loading over 3.0 mg cm-2,as well as high reversible areal capacity(>6.0 m Ah cm-2)even at higher sulfur loading of 6.7 mg cm-2.（4）A carbon nanofiber host architecture with in-built Ti N/Ti O2 heterostructure configuration derived from natural skin collagen fibers is designed,targeting the construction of advanced lithium-polysulfide batteries and lithiated silicon-polysulfide batteries.Ti N/Ti O2 heterostructure is spontaneously generated in the carbon nanofibers upon the pyrolysis of inborn N-enriched bio-precursor accompanied by thermal-induced topochemical self-nitridation without any additional nitrogen sources.As the host matrix,the multichambered carbon nanofiber integrating ordered chamber-like internal space(0.81 cm3 g-1),high specific surface area(1090.3 m2 g-1),and effectively enhanced conductivity is an advanced host material for infusion and spatial accommodation of liquid Li2S6.Theoretical and experimental results unveil the strong trapping and enhanced charge transfer on the polar heterointerfaces,synchronously realizing the immobilization-diffusion-transformation of polysulfides.The constructed Ti N/Ti O2-MCF-based Li-polysulfide cells show high discharge capacity(1406 m Ah g-1 at 0.1 C),outstanding rate capability(692 m Ah g-1 at 5 C)and long-life cycling stabilities（an ultralow capacity decay of0.023%per cycle）.Besides,a high areal capacity approaching 6 m Ah cm-2 with high S loading of5.8 mg cm-2 at a lean electrolyte condition(3μL mg-1)is achieved.An ingenious full battery configurated with a lithiated silicon anode and a polysulfide cathode exhibits superior rechargeable characteristics,as reflected by high-rate charge/discharge（up to 5 C）,decent cycling life（500cycles）,constant Coulombic efficiency（over 98.5%）,and high gravimetric energy density(588Wh kg-1 after 100 cycles)under a low N/P ratio（～1.18）operation. |
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