Silyl additives-driven synergistic inhibition engineering enables 4.9 V LiNi0.5Mn1.5O4 batteries beyond 300 Wh kg−1

Lithium-LiNi 0.5 Mn 1.5 O 4 (LNMO) batteries are considered promising candidates for high-energy–density storage due to their high operational voltage and low cost. However, existing electrolytes typically fail to balance high-voltage stability with electrode compatibility, thereby limiting their performance under practical conditions. In this study, we present a synergistic inhibition engineering in which silyl additives—triethylsilyl trifluoromethanesulfonate (TESOTf) and tris(trimethylsiloxy)boron (TMSB)—are incorporated into a conventional carbonate electrolyte, leading to stable cycling of Li-LNMO batteries at voltages as high as 4.9 V. Through in situ techniques and theoretical simulations, we demonstrate that TMSB immobilizes free PF 6 − ions in the electrolyte, while TESOTf preferentially consumes trace amounts of water, thereby shifting the hydrolysis reaction pathway of PF 6 − and reducing side reactions at the cathode. Electrochemical tests show that the addition of small quantities of TESOTf and TMSB significantly enhances the rate capability (10C for 85.2 mAh g −1 ), cycling stability (5C for 500 cycles), and high-temperature performance (60 °C, 5C for 300 cycles) of Li-LNMO cells. More importantly, a practical 3 Ah Li-LNMO pouch cell containing these additives demonstrated stable cycling under practical conditions (20 mg cm −2 , 20 μm Li, 2 g Ah −1 ), achieving an energy density exceeding 300 Wh kg −1 .