12/23/2023 0 Comments Affinity photo 1.7 new features![]() In such systems, the fraction of free solvent molecules is significantly reduced or eliminated, which effectively minimizes dissolution of the polysulfides in the electrolyte and suppresses the shuttle effect. ![]() Most of these electrolytes consist of an equal volume mixture of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) as solvent and contain a relatively low concentration (3 M) in organic solvents, 17,18 have been proposed to improve the stability and safety of Li–S batteries. To date, several different types of electrolytes have been used in Li–S batteries. Much effort has been dedicated, albeit with limited success, to solving these problems by developing suitable sulfur hosts and membrane materials that physically or chemically bind polysulfides, with the aim of suppressing polysulfide shuttling and enhancing sulfur cathode kinetics. These problems can be traced back to two important issues: (1) the shuttle effect of polysulfides and (2) nonoptimal Li ion solvation structures. ![]() ![]() These include rapid capacity decay, sluggish cathode kinetics and Li dendrite formation, the last of which can be a safety risk. 3 Unfortunately, with currently used electrolytes, Li–S batteries still have a number of problems. 2 In common Li–S batteries, the electrolyte solvates Li ions produced by oxidation of the Li metal anode along with the various sulfur-based intermediates generated during charge–discharge cycles. 1 As in any battery, the electrolyte is an indispensable component of Li–S batteries, since it not only transports ions but also regulates the chemical reactions occurring at the electrodes. In view of sulfur's high theoretical specific capacity (1672 mA h g −1) in combination with a high natural abundance and low toxicity, lithium–sulfur (Li–S) batteries are often regarded as ideal next generation high-energy density storage devices to replace the ubiquitous Li-ion batteries. This work demonstrates that the effective solvation of critical ions in energy storage devices is paramount to achieving peak performance. Furthermore, pouch-type cells can be prepared with high sulfur loadings (e.g., 3.43 mg cm −2) and a low electrolyte to sulfur ratio (e.g., 6.16 μl mg −1) while maintaining a high areal specific capacity (3.38 mA h cm −2). As a result, coin-type cells prepared with TMTAC-based electrolytes exhibit outstanding performance metrics for all key device parameters. Moreover, the shuttle effect of polysulfides is effectively suppressed as the quantity of free TMTAC in the TMTAC-based electrolyte is substantially reduced. Such a solvation structure not only leads to 3D deposition of Li 2S on the cathode, which is responsible to the reduced overpotentials of Li 2S nucleation and decomposition, but also suppresses Li dendrite growth on the anode. Theoretical studies and experimental data indicate that the cavity of TMTAC matches a Li ion to form a robust solvation structure. We show that these challenges can be overcome by replacing a linear ether (i.e., 1,2-dimethoxyethane) in commonly used electrolytes with a macrocyclic amine, 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (TMTAC). The widespread use of lithium–sulfur (Li–S) batteries is hindered by slow cathode kinetics, the shuttle effect, and dendrite growth on the anode. ![]()
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