RESUMO
Inorganic sulfide solid-state electrolytes, especially Li6PS5X (X = Cl, Br, I), are considered viable materials for developing all-solid-state batteries because of their high ionic conductivity and low cost. However, this class of solid-state electrolytes suffers from structural and chemical instability in humid air environments and a lack of compatibility with layered oxide positive electrode active materials. To circumvent these issues, here, we propose Li6+xMxAs1-xS5I (M=Si, Sn) as sulfide solid electrolytes. When the Li6+xSixAs1-xS5I (x = 0.8) is tested in combination with a Li-In negative electrode and Ti2S-based positive electrode at 30 °C and 30 MPa, the Li-ion lab-scale Swagelok cells demonstrate long cycle life of almost 62500 cycles at 2.44 mA cm-2, decent power performance (up to 24.45 mA cm-2) and areal capacity of 9.26 mAh cm-2 at 0.53 mA cm-2.
RESUMO
Li-rich cathodes have been in considerable attention for their high reversible capacity. However, they have serious problems like poor cycling with intense capacity decay and voltage fading, which restrict their access to practical applications. In this work, a facile and efficient strategy is proposed to alleviate these intrinsic issues with a high-efficiency electrolyte system. This special electrolyte enables Li-rich cathodes to deliver superior integrated performance with a high initial discharge capacity of 301 mAh·g-1, outstanding cycling stability with a capacity retention of 88% at 0.5 C over 500 cycles, and a remarkable rate capability of 136 mAh·g-1 at 5 C, respectively. What is more, the voltage fading is largely suppressed. Physical and electrochemical characterizations demonstrate that the robust CEI film formed on the cathode surface contributes to the improved electrochemical performance. This work provides a new approach to surmount defects of Li-rich materials and will largely promote their practical applications on Li-ion batteries.
RESUMO
The future energy needs have triggered research interest in finding novel energy storage systems with high energy density. Lithium-sulfur batteries are regarded as one of the most promising options for the next-generation energy storage applications because of their high theoretical energy and low cost. However, the electrochemical performances of lithium-sulfur batteries are seriously compromised by the polysulfide (LiPS) shuttling and the insulating nature of sulfur. To overcome these issues, novel CoNi1/3Fe2O4 (CNFO) nanoparticles uniformly covered on the carbon nanotubes are now reported as an efficient functional interlayer. Benefiting from the sufficient sulfiphilic sites of the CNFO for chemically bonding with LiPSs, as well as the conductive interconnected skeleton of carbon nanotubes, this composite material showed great enhancement on the rate capability and cycle stability of Li-S batteries. The Li-S battery using this interlayer exhibited a high initial capacity of 897 mA h g-1 and a low capacity decay of 0.063% per cycle within 250 cycles at 2 C. Meanwhile, an reversible specific capacity of 869 mA h g-1 (at 0.5 C) with high Coulombic efficiency could be obtained over 100 cycles at an elevated temperature (60 °C). We speculated that the chemical adsorption of CNFO for polysulfide-anchoring is extremely critical for the performances of Li-S batteries under high temperature.
