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Lithium–sulfur batteries (LSBs) are promising candidates for next-generation energy storage equipment due to their high theoretical energy density.

Li-rich cathode materials possess a much higher theoretical energy density than all intercalated cathode materials currently reported and thus are considered as the most promising candidate for next-generation high-energy density Li-ion batteries. However, the rapid voltage decay and the irreversible phase transition of O3-type Li-rich cathode materials often lessen their actual energy density and limit their practical applications, and thus, effectively suppressing the voltage decay of Li-rich cathodes becomes the hotspot of the current research. Herein, the F-doped O2-type Li-rich cathode materials Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2+δ−x F x (F-O2-LRO) are designed and prepared based on the P2-type sodium-ion cathode materials Na 5/6 Li 1/4 (Mn 0.54 Ni 0.13 Co 0.13 ) 3/4 -O 2+δ (Na-LRO) by ion exchange. It has been found that the asprepared F-O2-LRO exhibits excellent electrochemical performance, for example, a high discharge specific capacity of 280 mA h g −1 at 0.1 C with an initial Coulombic efficiency of 94.4%, which is obviously higher than the original LRO (77.2%). After 100 cycles, the F-O2-LRO cathode can still maintain a high capacity retention of 95% at a rate of 1 C, while the capacity retention of the original LRO is only 69.1% at the same current rate. Furthermore, the voltage difference (ΔV) of F-O2-LRO before and after cycling is only 0.268 V after 100 cycles at 1 C, which is less than that of the LRO cathode (0.681 V), indicating much lower polarization. Besides, even at a high current rate of 5 C, F-O2-LRO still displays a satisfactory discharge capacity of 210 mA h g −1 with a capacity retention of 90.1% after 100 cycles. Therefore, this work put forward a new strategy for the development and industrial application of Li-rich cathode materials in high-energy Li-ion batteries.