Hierarchical spherical Mo2C/N-doped graphene catalyst facilitates low-voltage Li2C2O4 prelithiation

The self-sacrificing Li2C2O4 is a promising lithium replenisher benefiting from its high specific capacity, residue-free and low-cost properties. However, the intrinsic low electrochemical activity leads to a decomposition potential up to 4.7 V, posing a challenge for the compatibility of electrolyte and cathode materials. Herein, a three-dimensional (3D) hierarchical spherical Mo2C/N-doped graphene co-catalysts is synthesized by self-polymerization and high-temperature annealing. It is shown that the synergistic catalytic effect of Mo2C and N-doped activated graphene enhances the reactivity of Li2C2O4 and the hierarchical three-dimensional conducting network accelerates the electron-ion transport. When the nano-Li2C2O4 is homogeneously encapsulated in the spherical catalytic center using a freeze-drying technique, the electrochemical reaction of Li2C2O4 is greatly promoted, resulting a significant drop of decomposition potential from 4.7 V to 4.16 V. As a result, the specific capacity of Gr||LFP and SiC||LFP full cells with composite lithium replenisher can be increased by 15% and 22%, respectively. Moreover, the solid electrolyte interface (SEI) is appropriately strengthened with pre-lithiation and thus guarantees superior cycling performance. [Display omitted] •Synergistic catalytic effect of Mo2C and N-doped graphene lowered the energy barrier.•Hierarchical conductive networks accelerate the electron-ion conduction.•Li2C2O4 activation potential reduced from 4.7 V to 4.16 V with efficiency to 100%.•Irreversible lithium loss of Gr/SiC||CM-LFP is reduced by 14.9%/21.7%.