Microspherical assembly of selectively pyridinic N-doped nanoperforated graphene for stable Li-metal anodes: Synergistic coupling of lithiophilic pyridinic N on perforation edges and low tortuosity via graphene nanoperforation

Abstract

Li-metal is considered the most attractive anode material for high-energy Li batteries. However, its direct use is severely hindered by the uncontrollable growth of Li dendrites and severe volume changes. Herein, the synergistic coupling of lithiophilicity and low-tortuosity channels of a microspherical graphene assembly host for stable Li-metal anodes are achieved via in-plane nanoperforation of graphene and selective doping of high level of pyridinic N on perforation edges. Specifically, 5–10 nm in-plane nanoperforations that are evenly spaced ∼15 nm apart are introduced to graphene. While nanoperforations provide low-tortuosity channels for the Li-ion diffusion throughout the graphene host, perforation edges act as preferential sites to selectively dope pyridinic N. The microspherical assembly of N-doped nanoperforated graphene (N-PSB) possesses the following advantageous features as a Li-metal host: (i) selective pyridinic N-doping on the nanoperforation edges, (ii) high level and uniform distribution of lithiophilic pyridinic N, (iii) electrical conductivity improvement via N-doping, and (iv) low tortuosity to enhance Li-ion transport through in-plane nanoperforations. Owing to the synergistic coupling of these advantageous features, N-PSB guides the uniform deposition of Li and suppresses Li dendrite growth, resulting in excellent cycling stability. Furthermore, pyridinic-N-doped at the nanoperforation edges shows higher lithiophilicity than the carbon radicals at the edges. The reported results are supported by density functional theory calculations. Finally, practical applicability of the N-PSB host is investigated by assembling a full cell with a LiNi0.6Co0.2Mn0.2O2 cathode.