Dual‐Chain Functionalized CuS Cathode for Li ⁺ /Mg ²⁺ Co‐participation towards High‐Performance Magnesium‐Based Batteries

Abstract Compared with rechargeable magnesium batteries (RMBs), magnesium–lithium hybrid batteries (MLHBs) represent a promising energy storage technology by integrating the advantages of natural abundance and limited dendrite growth of magnesium anode with rapid kinetics of lithium ions in cathode. However, conventional MLHBs suffer from Li ⁺ ‐dominant electrochemistry, fundamentally limiting their energy storage potential. Herein, a Pluronic F127‐assisted copper sulfide (F127‐CuS) micro‐flower cathode material is designed, realizing the Li ⁺ /Mg ²⁺ co‐participation. The hydrophobic PPO chain segment in the introduced F127 surfactant inhibits CuS agglomeration, while the hydrophilic PEO chain segment improves electrolyte wettability. Density functional theory (DFT) calculations and experimental results reveal the preferential insertion of Li ⁺ , which facilitates the subsequent insertion of Mg ²⁺ . As expected, the F127‐CuS cathode delivers a high initial reversible capacity of 512 mAh g ⁻¹ at 0.5 A g ⁻¹ with a superior specific energy density of 492 Wh kg ⁻¹ , and good long‐term cycling stability with a capacity of 221 mAh g ⁻¹ at 1 A g ⁻¹ after 1300 cycles. This dual‐chain polymer modification and structure‐interface synergistic optimization strategy provides a reference for the designment of co‐participation type MLHBs with high energy density and long cycle life.