Microwave-Assisted rGO Coupling for Stabilizing a V-Doped Co-Free Li-Rich Layered Cathode with High Discharge Capacity at 5C and 10C

Co-free Li-rich layered oxides are promising cathodes for high-energy lithium-ion batteries, but their practical use is limited by structural degradation, voltage decay, and poor cycling stability at high rates. Here, we investigate microwave-assisted coupling with reduced graphene oxide (rGO) as a strategy to stabilize a V-doped Co-free Li-rich layered cathode, Li_1.2Ni_0.3Mn_0.49V_0.01O₂, using a composite containing 1 wt% rGO. Thermal analysis showed that 1 mol% V does not significantly modify the formation range of the layered phase, supporting calcination at 800 C for 12 h. Raman spectroscopy and X-ray diffraction confirmed the preservation of the layered framework after both Li_1.2Ni_0.3Mn_0.49V_0.01O₂ and microwave-assisted rGO coupling. Rietveld refinement revealed very similar lattice parameters for the Li_1.2Ni_0.3Mn_0.49V_0.01O₂ and Li_1.2Ni_0.3Mn_0.49V_0.01O₂@rOG samples, indicating that the rGO treatment does not induce structural collapse. A low but measurable amount of Ni in the Li layer was detected in both samples, consistent with moderate antisite disorder. Electrochemically, V doping alone improved the high-rate response but reduced cycling stability. After microwave-assisted anchoring with 1 wt% rGO, the composite recovered the lost stability while maintaining strong rate capability. The Li_1.2Ni_0.3Mn_0.49V_0.01O₂@rGO cathode delivered 84.85% discharge-capacity retention after 80 cycles, compared with 79.63% for the Li_1.2Ni_0.3Mn_0.49V_0.01O₂ sample, and achieved discharge capacities of 148.47 and 113.58 mAh g^-1 at 5C and 10C, respectively. These results show that microwave-assisted rGO coupling is an effective route for stabilizing a V-doped Co-free Li-rich layered cathode under demanding rate conditions. Vanadium improves bulk kinetic behavior, whereas rGO enhances interfacial charge transfer and electronic connectivity, thereby improving cycling stability and enabling high discharge capacities at 5C and 10C.