Ultrathin Defective C–N Coating to Enable Nanostructured Li Plating for Li Metal Batteries

Abstract

Lithium metal batteries (LMBs) are obtaining increasing attention in view of their advantage of theoretical energy density up to 500 Wh kg −1 or higher. However, their performance exploitation is still retarded by anode dendrite growth, dead Li buildup, and electric contact loss at the interface. In order to overcome these challenges, herein, we proposed a defect engineering of a C−N polymer to construct a N-deficient ultrathin film (27 nm) with an unusually narrow bandgap (0.63 eV) as an artificial solid electrolyte interphase (SEI) by reactive thermal evaporation. This defective C−N film enables a nanostructured modulation of Li plating without severe dendrite extrusion and electric disconnection. Its high lithiophilicity is expected to trigger a desired space charge effect in the SEI with enhanced charge-transfer ability, which leads to significant reduction of both the nucleation (17.5 mV at 1 mA cm −2 ) and plateau overpotentials (70 mV at 3 mA cm −2 ) during Li plating and stripping. This interposition of a defect structure also endows Li/ Cu cells with extended cycling reversibility over 400 cycles and a highly stable Coulombic efficiency of 99% at 3 mA cm −2 . The interconnection preservation of the Li plating network modulated by the C−N interphase guarantees a high capacity retention of LiFePO 4 -based LMBs. The advantage of N-extraction from C 3 N 4 is comprehensively discussed in combination with the results based on g-C 3 N 4 decoration.

Rapid Interfacial Exchange of Li Ions Dictates High Coulombic Efficiency in Li Metal Anodes

“…Forming more of these heterogeneous grain boundaries through the use of readily oxidizing electrolyte additives such as LiNO3, particularly those which form highly defective, ionconducting reduction products on the Li metal surface, may be an effective route to improving Li ion transport at SEI/SEI interfaces. Taken together, our data suggest that modulating space-charge effects between grains in the SEI layer (e.g., through defect engineering92 ) may provide a promising route to achieving smooth Li deposition [97][98][99][100][101]. Finally, measurements at the electrolyte/SEI interface show that Li ion transport in this region is dominated by electrolyte salt concentration.…”

Superior thermal conductivity of poly (ethylene oxide) for solid-state electrolytes: A molecular dynamics study

“…The equilibrium molecular dynamics (EMD) simulation method (Green-Kubo method), which has been widely used to calculate thermal transport properties. [17][18][19][20] Green-Kubo formula 21,22 is a result of the linear response theory and the fluctuation dissipation theorem, which relates the heat flux autocorrelation to the thermal conductivity. The heat current is defined as ,…”

Phonon Transport within Periodic Porous Structures — From Classical Phonon Size Effects to Wave Effects

“…The reduction in the thermal conductivity is due to more phonons localized in a Si phononic crystal at boundaries. 126 In contrast to the huge thermal conductivity reduction, the electronic transport coefficients of a Si phononic crystal at 300 K are reduced slightly, and the Seebeck coefficient is similar to that of bulk Si. This leads to a higher ZT = 0.66 of a Si phononic crystal, which is about 66 times of that of bulk Si.…”