Zi-Xian Chen

Lithium-sulfur (Li-S) batteries are promising in achieving high energy density but inferior in cycling lifespan since Li polysulfides (LiPSs) corrode Li metal anode. Weakening the electrolyte solvating power (ESP) for LiPSs effectively mitigates anodic corrosion but inevitably retards cathodic reaction kinetics. Herein, the correlation between the ESP and the LiPS redox kinetics in weakly solvating electrolyte is unveiled for achieving high-performance Li-S batteries. The ESP exhibits a two-stage variation tendency as the weakly solvating solvent (WSS) content increases, where the transition depends on whether the WSS enters the LiPS inner solvation shell. Once the WSS directly coordinates with LiPSs, the LiPS charge-transfer kinetics deteriorate dramatically, with a rapid increase in activation polarization. To overcome the kinetic sluggishness, advanced electrocatalysts are introduced to endow Li-S batteries with reduced polarization and prolonged cycling lifespan. An ultrahigh energy density of 607 W h kg^-1 is realized in 10 Ah-level pouch cells with a stable cycling lifespan. This work deepens the current understanding of LiPS solvation and kinetics, highlighting the significance of weakly solvating electrolytes toward high-energy-density and long-cycling Li-S batteries.

Lithium-sulfur (Li-S) batteries are highly considered as next-generation energy storage techniques. Weakly solvating electrolyte with low lithium polysulfide (LiPS) solvating power promises Li anode protection and improved cycling stability. However, the cathodic LiPS kinetics is inevitably deteriorated, resulting in severe cathodic polarization and limited energy density. Herein, the LiPS kinetic degradation mechanism in weakly solvating electrolytes is disclosed to construct high-energy-density Li-S batteries. Activation polarization instead of concentration or ohmic polarization is identified as the dominant kinetic limitation, which originates from higher charge-transfer activation energy and a changed rate-determining step. To solve the kinetic issue, a titanium nitride (TiN) electrocatalyst is introduced and corresponding Li-S batteries exhibit reduced polarization, prolonged cycling lifespan, and high actual energy density of 381 Wh kg^-1 in 2.5 Ah-level pouch cells. This work clarifies the LiPS reaction mechanism in protective weakly solvating electrolytes and highlights the electrocatalytic regulation strategy toward high-energy-density and long-cycling Li-S batteries.

Lithium-sulfur (Li-S) batteries afford great promise on achieving practical high energy density beyond lithium-ion batteries. Lean-electrolyte conditions constitute the prerequisite for achieving high-energy-density Li-S batteries but inevitably deteriorates battery performances, especially the sulfur cathode kinetics. Herein, the polarizations of the sulfur cathode are systematically decoupled to identify the key kinetic limiting factor in lean-electrolyte Li-S batteries. Concretely, an electrochemical impedance spectroscopy combined galvanostatic intermittent titration technique method is developed to decouple the cathodic polarizations into activation, concentration, and ohmic parts. Therein, activation polarization during lithium sulfide nucleation emerges as the dominant polarization as the electrolyte-to-sulfur ratio (E/S ratio) decreases, and the sluggish interfacial charge transfer kinetics is identified as the main reason for degraded cell performances under lean-electrolyte conditions. Accordingly, a lithium bis(fluorosulfonyl)imide electrolyte is proposed to decrease activation polarization, and Li-S batteries adopting this electrolyte provide a discharge capacity of 985 mAh g^-1 under a low E/S ratio of 4 μL mg^-1 at 0.2 C. This work identifies the key kinetic limiting factor of lean-electrolyte Li-S batteries and provides guidance on designing rational promotion strategies to achieve advanced Li-S batteries.

Practical lithium–sulfur (Li−S) batteries are severely plagued by the instability of solid electrolyte interphase (SEI) formed in routine ether electrolytes. Herein, an electrolyte with 1,3,5‐trioxane (TO) and 1,2‐dimethoxyethane (DME) as co‐solvents is proposed to construct a high‐mechanical‐stability SEI by enriching organic components in Li−S batteries. The high‐mechanical‐stability SEI works compatibly in Li−S batteries. TO with high polymerization capability can preferentially decompose and form organic‐rich SEI, strengthening mechanical stability of SEI, which mitigates crack and regeneration of SEI and reduces the consumption rate of active Li, Li polysulfides, and electrolytes. Meanwhile, DME ensures high specific capacity of S cathodes. Accordingly, the lifespan of Li−S batteries increases from 75 cycles in routine ether electrolyte to 216 cycles in TO‐based electrolyte. Furthermore, a 417 Wh kg⁻¹ Li−S pouch cell undergoes 20 cycles. This work provides an emerging electrolyte design for practical Li−S batteries.

Practical lithium–sulfur (Li−S) batteries are severely plagued by the instability of solid electrolyte interphase (SEI) formed in routine ether electrolytes. Herein, an electrolyte with 1,3,5‐trioxane (TO) and 1,2‐dimethoxyethane (DME) as co‐solvents is proposed to construct a high‐mechanical‐stability SEI by enriching organic components in Li−S batteries. The high‐mechanical‐stability SEI works compatibly in Li−S batteries. TO with high polymerization capability can preferentially decompose and form organic‐rich SEI, strengthening mechanical stability of SEI, which mitigates crack and regeneration of SEI and reduces the consumption rate of active Li, Li polysulfides, and electrolytes. Meanwhile, DME ensures high specific capacity of S cathodes. Accordingly, the lifespan of Li−S batteries increases from 75 cycles in routine ether electrolyte to 216 cycles in TO‐based electrolyte. Furthermore, a 417 Wh kg⁻¹ Li−S pouch cell undergoes 20 cycles. This work provides an emerging electrolyte design for practical Li−S batteries.

Lithium–sulfur (Li–S) batteries are regarded as promising high‐energy‐density energy storage devices. However, the cycling stability of Li–S batteries is restricted by the parasitic reactions between Li metal anodes and soluble lithium polysulfides (LiPSs). Encapsulating LiPS electrolyte (EPSE) can efficiently suppress the parasitic reactions but inevitably sacrifices the cathode sulfur redox kinetics. To address the above dilemma, a redox comediation strategy for EPSE is proposed to realize high‐energy‐density and long‐cycling Li–S batteries. Concretely, dimethyl diselenide (DMDSe) is employed as an efficient redox comediator to facilitate the sulfur redox kinetics in Li–S batteries with EPSE. DMDSe enhances the liquid–liquid and liquid–solid conversion kinetics of LiPS in EPSE while maintains the ability to alleviate the anode parasitic reactions from LiPSs. Consequently, a Li–S pouch cell with a high energy density of 359 Wh kg⁻¹ at cell level and stable 37 cycles is realized. This work provides an effective redox comediation strategy for EPSE to simultaneously achieve high energy density and long cycling stability in Li–S batteries and inspires rational integration of multi‐strategies for practical working batteries.

Lithium–sulfur (Li–S) batteries are regarded as promising high‐energy‐density energy storage devices. However, the cycling stability of Li–S batteries is restricted by the parasitic reactions between Li metal anodes and soluble lithium polysulfides (LiPSs). Encapsulating LiPS electrolyte (EPSE) can efficiently suppress the parasitic reactions but inevitably sacrifices the cathode sulfur redox kinetics. To address the above dilemma, a redox comediation strategy for EPSE is proposed to realize high‐energy‐density and long‐cycling Li–S batteries. Concretely, dimethyl diselenide (DMDSe) is employed as an efficient redox comediator to facilitate the sulfur redox kinetics in Li–S batteries with EPSE. DMDSe enhances the liquid–liquid and liquid–solid conversion kinetics of LiPS in EPSE while maintains the ability to alleviate the anode parasitic reactions from LiPSs. Consequently, a Li–S pouch cell with a high energy density of 359 Wh kg⁻¹ at cell level and stable 37 cycles is realized. This work provides an effective redox comediation strategy for EPSE to simultaneously achieve high energy density and long cycling stability in Li–S batteries and inspires rational integration of multi‐strategies for practical working batteries.

Lithium-sulfur (Li-S) batteries have great potential as high-energy-density energy storage devices. Electrocatalysts are widely adopted to accelerate the cathodic sulfur redox kinetics. The interactions among the electrocatalysts, solvents, and lithium salts significantly determine the actual performance of working Li-S batteries. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a commonly used lithium salt, is identified to aggravate surface gelation on the MoS₂ electrocatalyst. In detail, the trifluoromethanesulfonyl group in LiTFSI interacts with the Lewis acidic sites on the MoS₂ electrocatalyst to generate an electron-deficient center. The electron-deficient center with high Lewis acidity triggers cationic polymerization of the 1,3-dioxolane solvent and generates a surface gel layer that reduces the electrocatalytic activity. To address the above issue, Lewis basic salt lithium iodide (LiI) is introduced to block the interaction between LiTFSI and MoS₂ and inhibit the surface gelation. Consequently, the Li-S batteries with the MoS₂ electrocatalyst and the LiI additive realize an ultrahigh actual energy density of 416 W h kg^-1 at the pouch cell level. This work affords an effective lithium salt to boost the electrocatalytic activity in practical working Li-S batteries and deepens the fundamental understanding of the interactions among electrocatalysts, solvents, and salts in energy storage systems.