In recent years, modifying cathode materials' surfaces become a popular pursuit. This paper reveals a novel spinel LiMn2O4 in situ coated with graphene-like membrane prepared using liquid-polyacrylonitrile (LPAN) as the carbon source. The structure and electrochemical performance of graphene-like membrane-coated spinel LiMn2O4 are investigated systematically. The membrane has a typical graphene-like layer carbon structure that can be applied the LiMn2O4 particles' surfaces in situ without affecting their crystal structure. Moreover, the graphene-like membrane helps to increase the particle size. The electrochemical performance reveals that coating the graphene-like membrane in situ significantly improves the discharge capacity and cycling stability of the spinel LiMn2O4. In particular, the spinel LiMn2O4 coated with a calcined 20 wt% LPAN graphene-like membrane in situ reached 131.1 mAh g−1 at room temperature, and up to 96% capacity is retained after 50 cycles at 0.1 C. The cyclic voltammetry and electrochemical impedance spectra analyses indicate that the graphene-like membrane does not influence the insertion or desertion of Li+. The improved electrochemical performance is attributed to the decreased manganese dissolution in the electrolyte and the smaller charge transfer resistance generated by the graphene-like membrane coating.