Lithium-based semi-solid flow battery (LSSFB) is expected to be applied in the field of large-scale energy storage. However, the rate performance of LSSFBs is unsatisfied due to the poor conductivity of active materials and the unstable contact with conductive additives. Herein, carbon coated MnO quantum dots derived from MIL-100 (Mn) were prepared. Such MnO quantum dots and carbon framework composite can not only increase the reactive active sites of MnO, but also avoid their agglomeration in the lithiation/delithiation process. Furthermore, the carbon framework and multi-walled carbon nanotubes (MWCNTs) are conducive to the rapid transport of electrons and can inhibit the volume expansion of MnO, achieving the high-rate performance and long cycling life. Moreover, MWCNTs can increase the suspension of the material and ensure the long-term stability of the slurry. These advantages endow the LSSFBs with high rate and long cycling performance. This work provides a promising strategy for the preparation of high-rate slurry electrode materials.