This article presents a study on improving the performance of rechargeable magnesium (Mg) batteries through a dual cation co-intercalation strategy. The research focuses on the TiS₂ material, which is a promising cathode for Mg batteries, but suffers from sluggish Mg²⁺ ion mobility. To address this, the study explores the co-intercalation of Mg²⁺ with Li⁺ or Na⁺ in dual-salt electrolytes, leveraging the faster mobility of Li⁺ and Na⁺ to enhance electrochemical performance. The study combines experimental and theoretical approaches to investigate the charge storage and redox mechanisms of co-intercalating cations. Results show that the redox activity of Mg²⁺ can be significantly improved with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role in the strategy's viability. Specifically, a significantly higher amount of Mg²⁺ intercalates with Li⁺ than with Na⁺ in TiS₂ due to the absence of phase transition in the former case, which enables improved Mg²⁺ storage. The study also highlights the importance of thermodynamic and structural stability of the host compound in accommodating multiple cationic charge carriers. Structural characterization and density functional theory (DFT) studies demonstrate that the host compound's stability is crucial for reversible accommodation of more than one cationic charge carrier. Additionally, spectroscopic probing through ex situ electron energy-loss spectroscopy (EELS) of cycled TiS₂ positive electrodes helped clarify the redox mechanism. The study compares the performance of the Mg-Li and Mg-Na systems with a reference Mg system. The Mg-Li system showed improved electrochemical performance, including higher specific capacity, insertion voltage, and nominal voltage, as well as better rate performance. The Mg-Na system, on the other hand, showed significant structural degradation and limited co-intercalation due to the larger ionic radius of Na⁺, which led to phase transitions and structural instability. The study also examines the structural evolution of TiS₂ upon cycling, revealing that the layered structure of TiS₂ undergoes discernible structural changes as the concentration of intercalating ions increases. The co-intercalation of Mg and Li ions led to expansion of the crystal structure, while the co-intercalation of Mg and Na ions resulted in different structural changes due to the larger ionic radius of Na⁺. The study further investigates the local structure of TiS₂ using ex situ Raman spectroscopy and transmission electron microscopy (TEM), revealing changes in vibrational modes and interlayer distances upon intercalation of different charge carriers. The results indicate that the intercalation of Mg and Li ions leads to a more stable structure compared to the intercalation of Mg and Na ions. Finally, the study uses DFT calculations to analyze the thermodynamics and kinetics of the cation co-intercalation process. The results show that the activation energiesThis article presents a study on improving the performance of rechargeable magnesium (Mg) batteries through a dual cation co-intercalation strategy. The research focuses on the TiS₂ material, which is a promising cathode for Mg batteries, but suffers from sluggish Mg²⁺ ion mobility. To address this, the study explores the co-intercalation of Mg²⁺ with Li⁺ or Na⁺ in dual-salt electrolytes, leveraging the faster mobility of Li⁺ and Na⁺ to enhance electrochemical performance. The study combines experimental and theoretical approaches to investigate the charge storage and redox mechanisms of co-intercalating cations. Results show that the redox activity of Mg²⁺ can be significantly improved with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role in the strategy's viability. Specifically, a significantly higher amount of Mg²⁺ intercalates with Li⁺ than with Na⁺ in TiS₂ due to the absence of phase transition in the former case, which enables improved Mg²⁺ storage. The study also highlights the importance of thermodynamic and structural stability of the host compound in accommodating multiple cationic charge carriers. Structural characterization and density functional theory (DFT) studies demonstrate that the host compound's stability is crucial for reversible accommodation of more than one cationic charge carrier. Additionally, spectroscopic probing through ex situ electron energy-loss spectroscopy (EELS) of cycled TiS₂ positive electrodes helped clarify the redox mechanism. The study compares the performance of the Mg-Li and Mg-Na systems with a reference Mg system. The Mg-Li system showed improved electrochemical performance, including higher specific capacity, insertion voltage, and nominal voltage, as well as better rate performance. The Mg-Na system, on the other hand, showed significant structural degradation and limited co-intercalation due to the larger ionic radius of Na⁺, which led to phase transitions and structural instability. The study also examines the structural evolution of TiS₂ upon cycling, revealing that the layered structure of TiS₂ undergoes discernible structural changes as the concentration of intercalating ions increases. The co-intercalation of Mg and Li ions led to expansion of the crystal structure, while the co-intercalation of Mg and Na ions resulted in different structural changes due to the larger ionic radius of Na⁺. The study further investigates the local structure of TiS₂ using ex situ Raman spectroscopy and transmission electron microscopy (TEM), revealing changes in vibrational modes and interlayer distances upon intercalation of different charge carriers. The results indicate that the intercalation of Mg and Li ions leads to a more stable structure compared to the intercalation of Mg and Na ions. Finally, the study uses DFT calculations to analyze the thermodynamics and kinetics of the cation co-intercalation process. The results show that the activation energies