| With the proposal of the carbon peaking and carbon neutrality goals,clean energy technology ushered in high-quality development opportunities.All-solid-state lithium metal batteries are considered to be the most promising next-generation battery system due to their advantages of high energy density,high safety,and green environmental protection.As the core of solid-state lithium battery technology,the performance of solid electrolyte materials largely determines the performance parameters of the battery.The development of commercial solid-state batteries has been hampered by the respective limitations of inorganic and organic solid-state electrolytes.To combine the advantages of both,a compromise strategy of organic/inorganic composite electrolytes has been inspired.However,the room temperature conductivity of the composite electrolytes and the interface stability between the electrodes are still not enough to support the required battery performance,which seriously affects the energy density,fast charging,safety,and service life of the battery.In the research of solid-state batteries based on organic/inorganic composite electrolytes,the interface problem is particularly critical,which mainly involves two aspects.On the one hand,there is a problem with the interface between organic and inorganic components inside the composite electrolytes.Weak bonding between ceramic and polymer matrix leads to severe aggregation of nanofillers,which disconnects the lithium-ion conduction channels inside the composite electrolyte,resulting in low room temperature ion conductivity(<10-4 S cm-1)and non-uniform ion distribution.On the other hand,the interface between the composite electrolytes and the solid electrodes is another issue.First of all,the solid-state electrolytes cannot flow like the liquid electrolytes,which is more likely to produce physical and mechanical decay at the solid-solid interface.Secondly,because the frontier orbital energy level of the composite electrolytes is not coordinated with the high-voltage cathode and lithium-metal anode,there is also the problem of interface（electrical）chemical instability,especially the interface problem between the composite electrolytes and lithium-metal anode with active nature and huge volume change has become a bottleneck restricting the development of solid-state batteries.Recent studies have proved that the ceramic nanofibers prepared by electrospinning technology are expected to improve the above problems,and also provide the possibility to further improve the electrochemical performance,and bring new structural and surface/interface design advantages.Therefore,starting from the basic component and structure design,this paper uses flexible ceramic nanofiber membranes as the supporting framework,and composite with polymer electrolyte matrix,achieving controllable construction of a series of composite electrolytes integrating the advantages of each component.Based on overcoming the problems of uneven ion transport,poor mechanical strength,and lithium dendrite growth caused by the agglomeration of ceramic nanoparticles or nanowires in the composite electrolyte,the correlation mechanism between the structure/surface chemistry of ceramic fiber materials and ion transport performance&lithium deposition behavior on the electrode surface is established,and the rapid ion transport of the bulk phase and interface of the composite electrolyte is realized.It provides a new regulation strategy and general concept for customized composite electrolytes with high ionic conductivity and high anodic cycle stability.The research results obtained are as follows:（1）A composite electrolyte with a"reinforced concrete"structure was constructed with flexible Si O2 nanofiber membranes as the framework,PEO,and Li TFSI as the cathode binder and electrolyte matrix.A low-resistance integrated all-solid-state battery with excellent electrochemical performance was designed by a simple in-situ casting process.Due to the continuous extension of the ceramic nanofiber/polymer interface,the composite electrolytes based on the ceramic nanofiber 3D framework have higher ionic conductivity,which overcomes the problem that the isolated inorganic particles in the composite electrolyte do not form a connected lithium ion transfer network,and makes the advantages of organic/inorganic interface enhancement better play.The porous nanofiber provides enough contact sites for the polymer electrolyte matrix to stabilize the structure of the electrolytes and generate more fast ion channels.The PEO in the cathode and the composite electrolyte fuse at high temperatures to form an integrated all-solid-state battery structure,which effectively strengthens the interface compatibility and stability between the cathode and the composite electrolyte.The Si O2nanofibers uniformly distributed in the composite electrolyte produce Lewis acid-base adsorption,which can effectively adsorb anions,and improve the lithium-ion transform number,thus inducing uniform deposition of Li+and inhibiting the growth of lithium dendrites.The 9wt%Si O2 nanofiber improves the toughness and thermal stability of the composite electrolytes.The prepared composite electrolyte film is uniform and has a small thickness（28μm）.The ionic conductivity of the composite electrolyte at 30℃is 1.3×10-4 S cm-1,and the all-solid Li Fe PO4//Li at 0.5C,The discharge capacity at 60℃and 45v℃is 159 m A·h·g-1 and 132 m A·h·g-1,respectively.The excellent electrochemical performance and industrialization-compatible process make it have broad commercial prospects in the large-scale production of high-efficiency solid electrolytes.（2）Based on the enhanced structure design mentioned above,to increase ion transport channels,active components are introduced.The ion conductor Li0.33La0.56Ti O3（LLTO）nanofiber film is selected as the 3D network framework.The flexible electrolyte membrane was prepared by using the block copolymer PVDF-b-PTFE with high elasticity and piezoelectric properties as the polymer matrix.The PVDF-b-PTFE has a high dielectric constant,which effectively improves the dissociation ability of lithium ions and hinders anions migration,increasing the concentration of free lithium ions.The ionic conductivity is 1.4×10-4 S cm-1,at 25℃,the lithium-ion transform number is 0.58,and the electrochemical window is up to 5.3V.In addition,the composite electrolyte has high mechanical strain and a viscoelastic surface,which is conducive to enhancing the interface contact stability of solid-state batteries.At the same time,a new strategy of"transient adjustment of lithium-ion distribution"on the surface of lithium metal anode is proposed,and a transition layer combining piezoelectric response and hybrid conductive function is designed,which overcomes the problem of interface dynamic failure during long-term cycling,reduces the battery overpotential,inhibits the dendrite growth,and effectively prolongs the cycling life of lithium metal anode in the solid-state battery.Li Fe PO4//Li battery provides high Coulomb efficiency in 550 cycles（>99.5%）and capacity retention（>85%）.（3）To further increase the interaction strength between ceramic nanofiber and polymer matrix,and improve the lithium-ion transmission performance on inorganic/organic interfaces,the composite electrolytes were prepared by combining mesoporous LaxCo O3-δ（LCO）nanofiber film with adjustable cation defects into PEO/Li TFSI matrix.The regulatory mechanism of the surface defect chemistry of ceramic materials on the molecular coupling between components is deeply explored,which provides new insights for the realization of efficient Li+transport and controllable lithium deposition behavior at the electrolyte/electrode interface.LCO prepared by simple non-stoichiometric methods has abundant A-site cationic defects,which can adjust the local unsaturated coordination states of Co atoms.These abundant crystal defects give LCOs strong coordination chemistry,which can coordinate with polymers and anions to regulate the molecular coupling in the composite electrolyte.By precisely adjusting the A-site cation defect from x=1.0 to 0.8,the coordination between LCO nanofibers and lithium-salt,and PEO was gradually enhanced,and the ionic conductivity of the composite electrolyte was increased to 2.5×10-4 S cm-1（30°C）.At the same time,the defect crystal with high catalytic activity can accelerate the interface reaction of lithium metal/electrolyte.The introduction of LCO nanofiber accelerates the decomposition of N（CF3SO2）2-,forming a Li F/Li3N-rich interface with high interface energy and fast ion transport capability.The critical current density of the composite electrolyte was increased to 1.8 m A cm-2.Li Fe PO4//Li batteries have high Coulomb efficiency of～99.9%and can stably cycle more than 1000 cycles. |
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