Lithium Deposition Process Based On Anode Lithiophilic Site Regulation

Lithium metal has been considered as the most important next generation rechargeable anode material due to its high theoretical specific capacity(3860 m A g h^-1).However,the lithium dendrite growth on the lithium metal surface during the cell cycle will lead to a series of problems,such as the SEI break,side effects and even pierced separator leading to short circuit and causing security problems.Therefore,it is important to solve the problem of lithium dendrite to stabilize the lithium anode.In this paper,the guiding effect of lithiophilic sites on lithium deposition behavior was explored from the two directions of constructing three-dimensional current collector electrode and modifying lithium anode interface,so as to realize controllable deposition of lithium metal and improve the stability of battery.To construct a lithiophilic–lithiophobic gradient collector has been regarded as an effective strategy to address the challenge of lithium dendrite growth in Li metal anode.However,it was also found that the uneven stress accumulation,induced by the directional deposition,would cause fatigue-like failure in the gradient structure.In this work,a hybrid carbon nano fiber structure,consisting of a gradient nitrogen doping carbon nano fiber(NCNF)layer and a Cu doped carbon nano fiber(Cu CNF)layer,was fabricated.The Cu-decorated carbon nanofibers not only provide a deposits-free(lithiophilic)surface,but also act as“reinforcing rib”to resist the fatigue stress.The unique hybrid structure delivers a high Coulomb efficiency and resistance to repeat stress application.Based on this special strategy,the Cu CNF-NCNF current collector could deliver an extremely high Coulomb efficiency of 97.7%at current density of 1m A cm^-2 after 500 cycles.Even at a high current density of 4 m A cm^-2,it could still circulate stably for 150 cycles,the symmetric cell can also maintain a stable cycle for260 h at 4 m A cm^-2.In the Li Fe PO₄ full cells test,it could maintain a capacity retention of 95.77%after 500 cycles at 0.5 C,The rate performance is also improved.In addition to the construction of a three-dimensional anode structure,a three-dimensional carbon tube material(CT)was designed and synthesized with lithiophilic nanoparticles distributed on the inner wall,and this unique three-dimensional carbon material was used to construct a lithium anode modification layer.By adjusting the thickness of the surface modification layer of lithium anode,the optimal preparation process of the surface modification layer of lithium anode was investigated.This three-dimensional carbon tube material can induce the deposition of lithium into the interior of the carbon tube material,prevent the dendrite growth of lithium,and alleviate the volume change caused by deposition and stripping of lithium,reduce the contact with the electrolyte,and then alleviate the occurrence of side reactions.Two kinds of carbon tube materials,Ag@CT and Cu O@CT,were prepared simultaneously in the experiment.It has been proved that the symmetric cell can cycle stably for 1200 h under the current density of 1 m A cm^-2 by forming such a protective layer.At higher current density and surface capacity,it also showde better performance than pure lithium foil symmetric cells.When matched with Li Fe PO₄,the discharge specific capacity of the lithium anode modified by the two kinds of carbon tube materials(>144 m Ah g^-1)is higher than that of the pure lithium(119.3 m Ah g^-1)at 0.5C.The performance was also significantly improved at Lithium sulfur cells.This kind of carbon tube structure@metal particle material also has a strong promotion and application in other energy devices.