| Lithium-sulfur(Li-S) batteries is one of the hottest high-energy-storage devices. However, praticcal application of Li-S batteries is being restricted by the solubility of the reaction intermediates in both discharge and charge processes, polysulfides can diffuse between the cathode and anode, as a result, Li–S battery generally exhibits low utilization and poor cycle stability. Here, Li-ion selective solid electrolyte that allow only the Li+ though while impermeable to polysulfides have been proposed for Li-S cells to improve the utility of active material and cycle performance.One of the most promising electrolytes, NASICON-typed Li1.4Al0.4Ti1.6(PO4)3(LATP) exhibits a high ionic conductivity, good stability. Sol-gel method, one way to prepare solid electrolyte LATP, the characteristic of sol-gel method is high purity and well-distributed chemical component, but the method is very time-consuming and complex. In order to improve the efficiency, solid electrolytes Li1.4Al0.4Zrx Ti1.6-x(PO4)3(LAZTP), Li1.4+y Al0.4Ti1.6Siy P3-y O12(LATSP)are formed by partially substituting Zr4+ for Ti4+, Si4+ for P5+, are synthesized by modified sol-gel method, the influence of Zr4+and Si4+doping on the structure and ionic conductivity of solid electrolytes are studied. Results show that partially substituting Zr4+ for Ti4+, the total conductivity in room temperature first increased and then decreased with increasing x, the maximum values of ?b and ?t, 2.81×10-3 S/cm and 1.4×10-3 S/cm, respectively, are obtained for Li1.4Al0.4Zr0.1Ti1.5(PO4)3; partially substituting Si4+ for P5+, the total conductivity in room temperature gradually decreased with increasing y.Solid electrolyte LAZTP(x=0.1) possess good hardness and can not contact with metal Li directly. Here we propose a new method to solve these problems effectively based on a semi-solid cell architecture in which the carbon-sulfur composite is coated onto solid electrolyte LAZTP as cathode materials, Au is sputtered onto the carbon-sulfur composite as a current collector and a polypropylene separator soaked with organic electrolyte is placed between the lithium metal anode and solid electrolyte. For the semi-solid battery, the first discharge capacity is as high as 1405 m Ah/g, and matains at 1276 m Ah/g after 50 cycles at the current density of 100 m Ah/g between 1-4 V. In comparison with the liquid battery, the as-prepared semi-solid battery shows a improved performance.To reduce costs, the second semi-solid cell architecture was put forward, in which the carbon-sulfur composite is coated onto Al foil, solid electrolyte is placed between the lithium metal anode and cathode, and a polypropylene separator soaked with organic electrolyte is placed on both sides of LAZTP to reduce the contact resistance. For the semi-solid battery, the intial discharge capacity is 1387 m Ah/g and remains at 1360 m Ah/g after 40 cycles at the current density of 50 m A/g between 1-4 V. Even at a current density of 200 m A/g, the battery still shows a good cycle performance with a capacity of 810 m Ah/g after 80 cycles. Through replacing the polypropylene separator soaked with organic electrolyte that placed between the cathode and LAZTP with an LAZTP soaked with organic electrolyte, the structure of semi-solid is simplified further more. The simplified semi-solid battery show a discharge capacity steady at 1100 m Ah/g, at the current density of 200 m A/g between 1-4 V. This suggests that the semi-solid cell structure can greatly improve the utility of active material and cycle performance. They have potential applications in electric vehicle and energy storage. |
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