Application Of Three-dimensional Conductive Framework Composite Lithophilic Coating In Stabilizing Lithium Metal Anodes

Energy is an important cornerstone of human survival and development.As an important energy storage method,batteries alleviate human dependence on fossil energy.In the past 30 years,lithium-ion batteries（LIBs）have dominated,but the energy density is approaching the limit due to the low specific capacity of the graphite anode,which is difficult to meet the demand for high energy density rechargeable batteries.Li metal has attracted widespread attention from researchers because of its ultra-high theoretical specific capacity(3860 m Ah g^-1)and low redox potential（-3.04 V vs standard hydrogen electrode）as a highly competitive anode candidate for next-generation energy storage devices.However,due to the high electrochemical activity and hostless properties of Li,it also faces great challenges in practical applications.Such as unstable interfaces,uncontrollable dendrite growth,infinite volume changes,etc.,which will have a great negative impact on battery performance.To solve the above problems,this paper mainly starts from the modification of electrode structure,combines the three-dimensional conductive carbon framework and lithiophilic coating to jointly construct a composite Li metal anode.The main work contents are summarized as follows:（1）Three-dimensional conductive carbon fiber surface was successfully modified by hyperbranched polyol（HP）through a simple esterification reaction（CFC@HP）,and the CFC@HP-Li composite Li metal anode was prepared by the rolling method.Among them,the porous structure of the carbon fiber network is not only beneficial to reducing the local current density but also provides enough space to accommodate Li.The HP with a large number of Li affinity sites can guide the uniform deposition of Li,regulate the local area current density,and then homogenize Li⁺flux to suppress the formation of dendritic Li.Notably,the symmetric batteries with CFC@HP-Li as the anode exhibit more stable cycling and smaller voltage hysteresis than the pure Li electrode,especially at a current density of 2 m A cm^-2.Furthermore,when used in conjunction with commercial Li Fe PO₄（LFP）cathodes,the capacity retention rate of the CFC@HP-Li//LFP full batteries is still as high as 88.9%after 500 cycles at 2 C.Such Li composites with optimized structural design and lithiophilic modification will open new avenues for the safety and stability of high-energy-density energy storage applications.（2）The dual-interface protection of Li metal anode is achieved by modifying lithiophilic layers on the three-dimensional conductive carbon framework and separator,respectively.First,a lithiophilic TiN coating was decorated on a three-dimensional conductive carbon framework by magnetron sputtering,and a composite Li metal anode（CFC@TiN-Li）was prepared by a high-temperature melting method.The lithiophilicity of TiN significantly improves the efficiency of the high-temperature melting method to prepare the composite anode and realizes the uniform modification of Li on the three-dimensional conductive carbon framework.In addition,this dual-interface synergistic protection also enables Li⁺to migrate along a certain trajectory from the beginning to the end of transmission,further enhancing the interfacial stability of the Li metal anode and the uniformity of ion transport and deposition.Symmetric batteries assembled with dual-interface modified electrodes（Al-CFC@TiN-Li）can cycle stably without any significant short circuits even at high current density(6 m A cm^-2)and high areal capacity(10 m Ah cm^-2).SEM characterization shows that the electrode still maintains the intact structural morphology after cycling.When assembled with commercial LFP cathode to form a full battery,the Al-CFC@TiN-Li anode still exhibits a higher capacity than pure Li anode at a high rate of 3 C,and the reversible specific capacity can be stabilized at 88.4 m Ah g^-1after 400 cycles,and the capacity retention rate is as high as 92.57%.Not only that,but the Al-CFC@TiN-Li electrode also has certain universality,can be assembled with the ternary cathode（NCM523）to form a full cell,and exhibits excellent cycling stability and high capacity retention.The above experiments collectively demonstrate that starting from the dual-interface modification strategy,highly stable and safe Li metal anodes can be developed.