Lithium secondary batteries have attracted considerable attention due to their great potential to achieve ultrahigh energy density for future use. However, the Li metal anode suffers dendrite formation during repeated stripping/plating, hindering its practical realization. Herein, for the first time, an artificial solid electrolyte interphase layer, lithium phosphorus oxynitride (LiPON), is introduced for the lithium anode, and the viable application in highenergy lithium secondary pouch cell is probed. LiPON is stable with lithium and in the air, which can protect the lithium from the side reaction with H 2 O and O 2 effectively. In low-energy batteries, the LiPON layer can enhance the efficiency of lithium deposition/dissolution and prolong the lifespan of the batteries. Further on, the discharge capacities of the lithium secondary cells with an energy density over 350 Wh kg −1 deploying LiPON-coated Li anodes drop fast, and the batteries are prone to severe polarization leading to the termination of life. Nonuniform current density resulting from the cracks caused by the large mass of lithium stripping/plating is ascribed to being the decisive factor shortening the life of batteries. Generally speaking, more and further exploration should be focused on the modification of the large-area lithium anode to accomplish high-energy-density lithium batteries for practical applications.

A strategy for enabling a novel carbon fluoride (CF x ) to be a high-performance cathode material for sodium batteries is proposed and realized. An amorphous and highly disordered CF x , denoted as d-CF x , is prepared through a facile synthesis route. Herein we report on a Na/d-CF x cell reversibly discharging/charging at such a low overpotential and capacity-decay rate. The polarization of the Na/d-CF x cell is about 780 mV, the lowest value reported in the state-of-the-art Na/CF x system. The initial discharge capacity is 582.5 mA h/g, with a capacity of 412.5 mA h/g after 12 cycles. The designed d-CF x improves the Na+ diffusion rate and facilitates the reaction with larger sodium ions during the discharging process. Amorphous discharge products NaF are easily decomposed, enhancing the charge reaction. The small grain size of NaF is believed to be another key factor that enables the minimal charge gap of Na/d-CF x cells and a slower capacity-decay rate, which can facilitate the decomposition of NaF and the reformation of C–F bonds during the charging process. Generally speaking, this study encourages the further exploration of secondary sodium/CF x batteries, and the cyclability of the sodium anode is included.

Carbon fluoride/graphene oxide/polyacrylonitrile (CFx/GO/PAN, denoted as CGP) electrodes are prepared for lithium primary and sodium secondary batteries. The introduction of GO sheets and PAN built a sandwich‐like structure. The rate performances of Li/CGP batteries verify that PAN and GO materials have negligible effects on the electrochemical properties of lithium primary batteries. In Na/CGP batteries, GO sheets have more defects to facilitate sodium ions transfer and offer more active sites for NaF deposition and decomposition. Meanwhile, the GO network coating of the CFx particles confines active fluorine during the cycles. Cubic and nanoscale discharge products of NaF form both on the surface of CFx particles and the GO sheets, respectively. Na/CGF batteries achieve an initial discharge capacity of 507.0 mAh g−1 and a voltage polarization of 0.75 V, except in the first cycle. These results demonstrate that CGP electrodes with a sandwich‐like structure have favorable electrochemical properties, resulting in the synergetic effect of GO sheets and PAN.

Poly­(vinylidene fluoride-co-hexafluoropropylene) and Li7La3Zr2O12-poly­(vinylidene fluoride-co-hexafluoropropylene) films were introduced to both Li and non-Li anodes. Via the recombination of poly­(vinylidene fluoride-co-hexafluoropropylene)-Li7La3Zr2O12, the ionic conductivity of the anodes has been greatly improved, and the deposition/plating barrier has been decreased. On the one hand, the thin film introduced upon lithium metal ensures cyclic stability in both symmetrical cells and full cells. The Li metal with Li7La3Zr2O12-poly­(vinylidene fluoride-co-hexafluoropropylene) films behaved stably over 500 h with little increase in polarization. On the other hand, the modification upon Cu foil provided a long cycle life over 300 cycles in Li–Cu cells. When the poly­(vinylidene fluoride-co-hexafluoropropylene)-Li7La3Zr2O12@Cu foil (non-Li anode) failed, a type of self-protected mechanism was activated, ensuring better mechanical properties and safety.