MXene nanofibers confining MnO nanoparticles: a flexible anode for high-speed lithium ion storage networks

The electron and ion conductivities of anode materials such as MnO affect critically the properties of anodes in Li-ion batteries. Herein, a three-dimensional (3D) nanofiber network (MnO-MXene/CNFs) for high-speed electron and ion transport with a MnO surface anchored and embedded inside is designed via electrospinning manganese ion-modified MXene nanosheets and subsequent carbonization. Ion transport analysis reveals improved Li⁺ transport on the MnO-MXene/CNF electrode and first-principles density functional theory (DFT) calculation elucidates the Li⁺ adsorption and storage mechanism. The surface-anchored MnO nanoparticles form extremely strong bonds with the nanofibers, and the internally embedded MnO nanoparticles, due to the fiber confinement effect, ensure the structural stability during charging and discharging, achieving the so-called dual stabilization strategies for cyclic fluctuation. By electrospinning, self-restacking of MXene flakes can be prevented, thereby giving rise to a larger surface area and more accessible active sites on the flexible anode. Benefiting from the 3D network with excellent conductivity and stability, at high current densities, the MnO-MXene/CNF anode exhibits outstanding electrochemical characteristics. Even after 2000 cycles, a reversible capacity of 1098 mA h g^-1 can be obtained at 2 A g^-1 with only 0.007208% decay rate. The MnO-MXene/CNF anode also shows a significant rate performance such as 1268 mA h g^-1 at 2 A g^-1 and 1137 mA h g^-1 at 5 A g^-1 corresponding to an area specific capacity of 2.536 mA h cm^-2 at 4 mA cm^-2 and 2.274 mA h cm^-2 at 10 mA cm^-2, respectively. The results indicate that the MnO-MXene/CNF anode has excellent Li-ion storage properties and great commercial potential.