In-situ Construction Of Self-Supporting Micronano-Pores Film For Negative Electrode Of Lithium Metal Battery

With the booming advances in high-end electronic devices,commercial lithium ion batteries are currently difficult to meet the urgent need for high-energy-density storage batteries.With the ultra-high capacity(3860 mA h g^-1),low gravimetric density(0.534 g cm^-3)and the most negative electrochemical potential?-3.04 V?,lithium metal is regarded as a“Holy Grail”electrode and has received extensive attentions.However,the Li dendrites and“dead”Li are easily formed during charge/discharge processes due to the nucleation sites for Li plating are isolated and randomly on anode material,which brings about safety problems and low Coulombic efficiency.Besides,Li metal anode exhibits a“hostless”feature which can bring about infinite relative volume change during cycling,and induced internal stress changes will cause solid electrolyte interphase?SEI?cracks,thereby deteriorating electrochemical performance.For the isolated and random distribution of nucleation sites,metal lithium dendrites are easily formed,and a self-supporting structure is designed to avoid the use of binders and ensure sufficient nucleation sites;for“hostless”matrix of the Li metal anode,the volume expansion is easily caused.The micro-nano-host matrix is designed to ensure that more metal lithium can be stored while providing the host structure.Therefore,a micro-nanoporous film with self-supporting structure is constructed in situ as a host material for metal anodes to inhibit lithium dendrite growth and improve the stability of metal lithium long-period deposition/dissolution process.This paper has made the following research progress:?1?Self-supporting lithiophilic nitrogen doped carbon rod array?NCRA?was constructed in situ based on spontaneous redox reaction and pyrolysis conversion between copper foil and TCNQ.The deposition/dissolution behavior and long-term cycling stability of metallic lithium were systematically studied when NCRA was used as the host matrix.It was found that the doping amount of lithiophilic nitrogen in NCRA can reach9.43at%.The uniform distribution of nitrogen as active point on the self-supporting NCRA structure could induce uniform nucleation and growth of metallic lithium,thus effectively inhibiting the formation of lithium dendrites.Hence,the NCRA matrix exhibited low lithium loss mass and good long-term cycling stability during Li plating/stripping.The loss mass of Li in each cycle on NCRA was less than 0.01 mg cm^-2 at 1.0 mA cm^-2and the value was much smaller than that(0.063 mg cm^-2)on Cu foil.The Li|NCRA@Li symmetric cell had ultralong lifespan beyond 620 h and small voltage hysteresis of less than 40 mV at 2.0 mA cm^-2.In addition,it also showed good electrochemical performance in the NCRA@Li|LiFePO₄ full battery test.?2?Self-supporting dendritic copper porous film?DCPF?is formed by one-step electrodeposition at gas-liquid-solid interface.The lateral growth behavior of Li induced by self-supporting DCPF,long-term deposition/dissolution stability and full cell performance were investigated.It was found that Li nucleates on the surface of Cu nanoparticles and grows laterally by the induced action of lateral Cu dendrites consisting of nanoparticles.Thereby suppressing the vertical growth of the Li dendrites.Meanwhile,Self-supporting DCPF with dendritic walls not only provides space for Li storage,but also provides more nucleation sites for uniform deposition of Li,thereby reducing local current density.On this basis,high and stable Coulombic efficiency of 98%after 600 cycles at 1 mA cm^-2 and prolong lifespan of 2400 h in the symmetric cell are achieved.Coupled with a LiFePO4 cathode,the full cell exhibits good rate performance and cycle stability with capacity retention of 82.4%for 250 cycles at 1 C.