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The presence of strong anharmonic effects in surface functionalized MXenes greatly challenges the use of harmonic lattice dynamics calculations to predict their phonon spectra and lattice thermal conductivity at finite temperatures. Herein, we demonstrate the workflow for training and validating machine learning potentials in terms of moment tensor potential (MTP) for MXenes including Mo 2 TiC 2 , Mo 2 TiC 2 O 2 , Mo 2 TiC 2 F 2 and Janus-Mo 2 TiC 2 OF monolayers. Then, the MTPs of MXenes are successfully combined with the harmonic lattice dynamics calculations to obtain the temperature renormalized phonon spectra, three-phonon scattering rates, phonon relaxation times and lattice thermal conductivity at finite temperatures. Furthermore, combining MTPs with classic molecular dynamics simulations at finite temperatures directly enables the calculation of phonon quasi-particle spectral energy density with a full inclusion of all anharmonic effects in MXenes. Our current results indicate that anharmonic effects are found to be relatively weak in Mo 2 TiC 2 and Mo 2 TiC 2 O 2 monolayers, whereas the phonon quasi-particle spectral energy densities largely resemble those of harmonic or renormalized lattice dynamics calculations. Significant broadening of spectral energy density at finite temperature is predicted for Mo 2 TiC 2 F 2 and Janus-Mo 2 TiC 2 OF monolayers, implying strong anharmonic effects in those MXenes. Our work paves a new way for fast and reliable calculation of the phonon scattering process and lattice thermal conductivity of MXenes within MTPs trained from first-principles molecular dynamics simulations in the future.

Ion migration and electron transmission are vital for manganese dioxides in zinc ion batteries. δ-MnO 2 is believed to be more suitable for zinc ion storage due to its layered structure. However, the performance of δ-MnO 2 is still hampered by the frustrating conductivity and sluggish reaction kinetics. Herein, atomic engineering is adopted to modify δ-MnO 2 at the atomic level to obtain oxygen-deficient δ-MnO 2 (N-MnO 2 ). Meanwhile, hollow carbon microtubes (HCMTs) obtained from green and renewable energy grass are proposed as cross-connected electron transmission matrices (CETMs) for MnO 2 . The biomass-derived CETMs not only optimize reaction kinetics but also facilitate the ion storage performance of MnO 2 . The as-prepared N-MnO 2 @HCMTs exhibit high rate capability and enhanced pseudocapacitve behavior contributed by the oxygen-deficient N-MnO 2 and CETMs. Ex situ analysis reveals the reversible insertion/extraction of H + and Zn 2+ in N-MnO 2 @HCMTs during charge/discharge processes. Moreover, the quasi-solid-state N-MnO 2 @HCMTs//Zn cells are assembled and they deliver extraordinary discharge capacity and a long cyclic lifespan. This study may provide insights for further exploration of cathode materials in AZIBs and promote the large-scale production of aqueous Zn-MnO 2 batteries.