Low-cost Lithium-sulfur Batteries Research Articles

Self-crystallized Interlayer Integrating Polysulfide-adsorbed TiO2/TiO and Highly-electron-conductive TiO for High-stability Lithium-sulfur Batteries

Low-cost lithium sulfur(Li-S) batteries afford preeminent prospect as a next-generation high-energy storage device by virtue of great theoretical capacity. Nevertheless, their applications are restricted by some challenging technical barriers, such as weak cycling stability and low poor-conductivity sulfur loading originated in notorious shuttling effect of polysulfide intermediates. Herein, free of any complicated compositing process, we design an interlayer of carbon fiber paper supported TiO2/TiO to impede the shuttle effect and enhance the electrical conductivity via physical isolation and chemical adsorption. Such a self-crystallized homogeneous interlayer, where TiO2/TiO enables absorbing lithium polysulfides(LiPSs) and TiO plays a key role of high-electron-conductivity exhibited ultrahigh capacities(1000 mA·h/g at 0.5 C and 900 mA·h/g at 1 C) and outstanding capacity retention rate(97%) after 100 cycles. Thus, our design provides a simple route to suppress the shuttle effect via self-derived evolution Li-S batteries.

Sulfur double encapsulated in a porous hollow carbon aerogel with interconnected micropores for advanced lithium-sulfur batteries

Abstract Due to high theoretical specific capacity, energy density, and low-cost lithium-sulfur (Li-S) batteries became the most potential energy storage devices for the next generation. The harsh shuttling effect, poor electroconductibility of sulfur, and volume change affect the Li-S battery’s practical application. Herein, the rational design of porous hollow carbon aerogel (PHCA) with an ultra-high specific surface area of 2054.5 m2 g−1 and outstanding adsorption ability is firstly fabricated to restrict the shuttling effect of lithium polysulfides (LiPSs) by using commercialized nano-CaCO3 as a template. As a sulfur host, the S/PHCA cathode delivers initially discharge specific capacity of 992.7 mAh g−1 with an average Coulombic efficiency of 97.6%. After 200 cycles, it obtains the reversible specific capacities of 600.1 mAh g−1 for S/PHCA cathode at 0.1C (2.2 mg cm−2) corresponding to 60.45% of their initial discharge specific capacity. As a PHCA interlayer, the Li-S battery with the PHCA interlayer exhibits initially discharge specific capacity of 1267.7 mAh g−1 with an average Coulombic efficiency of 99.36% at 0.1C (3.2 mg cm−2) and maintains at 863.3 mAh g−1 with the discharge specific capacity retention rate of 69.2%. This is an effective strategy to improve the outstanding electrochemical performance which is beyond reported carbon materials, which is attributed to stronger adsorption of LiPSs by the micropore. This work provides a new direction for the modification of a sulfur host and interlayer and simultaneously reveals the relationship between the heteroatom distribution and LiPSs.

Carbon confinement synthesis of interlayer-expanded and sulfur-enriched MoS2+x nanocoating on hollow carbon spheres for advanced Li-S batteries

High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems. However, the intrinsic problems of the sulfur cathode severely restrict their further practical application. Here, a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host. A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process, which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres. This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials, high electronic conductivity, and fast lithium-ion diffusive pathways. In addition, additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species, dramatically accelerating their conversion kinetics and re-utilization. The detailed defect-induced interface catalytic reaction mechanism is firstly proposed. As expected, the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g−1 at 0.2 C and a desirable rate performance (593 mAh·g−1 at 5.0 C), implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.

Encapsulation of Few-Layer MoS2 in the Pores of Mesoporous Carbon Hollow Spheres for Lithium-Sulfur Batteries.

Integrating a highly conductive carbon host and polar inorganic compounds has been widely reported to improve the electrochemical performances for promising low-cost lithium sulfur batteries. Herein, a MoS2/mesoporous carbon hollow sphere (MoS2/MCHS) structure has been proposed as an efficient sulfur cathode via a simple wet impregnation method and gas phase vulcanization method. Multi-fold structural merits have been demonstrated for the MoS2/MCHS structures. On one hand, the mesoporous carbon hollow sphere (MCHS) matrix, with abundant pore structures and high specific surface areas, could load a large amount of sulfur, improve the electronical conductivity of sulfur electrodes, and suppress the volume changes during the repeated sulfur conversion processes. On the other hand, ultrathin multi-layer MoS2 nanosheets are revealed to be uniformly distributed in the mesoporous carbon hollow spheres, enhancing the physical adsorption and chemical entrapment functionalities towards the soluble polysulfide species. Having benefited from these structural advantages, the sulfur-impregnated MoS2/MCHS cathode presents remarkably improved electrochemical performances in terms of lower voltage polarization, higher reversible capacity (1094.3 mAh g−1), higher rate capability (590.2 mAh g−1 at 2 C), and better cycling stability (556 mAh g−1 after 400 cycles at 2 C) compared to the sulfur-impregnated MCHS cathode. This work offers a novel delicate design strategy for functional materials to achieve high performance lithium sulfur batteries.

Design and interface optimization of a sandwich-structured cathode for lithium-sulfur batteries

The high-energy and low-cost lithium-sulfur (Li-S) battery is regarded as a new generation energy-storage device. However, the Li-S battery mostly suffers from low electronic conductivity and poor cycle capability. This study reports on a novel sandwich-structured cathode with optimized electrode architecture and interface design of the current collector (named as M-S-LTO) made by a facile layer-by-layer slurry coating process. The new integrated electrode is composed of a micro-cracked current collector (MCC) based on multi-wall carbon nanotubes, a middle layer of sulfur/carbon material and an upper current collector&interlayer (UCC&I) based on multi-wall carbon nanotubes and Li4Ti5O12 nanospheres. The M-S-LTO cathode produces a better electrochemical performance because of its improved internal electrical and ionic conductivity, stable structure and mitigation of shuttle effect, in contrast to the sulfur electrode with either an MCC (M-S cathode) or a smooth aluminum foil current collector (S cathode). At a current density of 0.2 C, the Li-S battery with the M-S-LTO cathode delivers a high initial capacity of 1248.6 mAh g−1 and retains a reversible capacity of 960.3 mAh g−1 after 200 cycles. Even at 1 C, its capacity can reach 773.4 mAh g−1 after 200 cycles. The battery with the M-S-LTO cathode shows a higher cycle performance than most of other reported cells based on the interlayer design with a comparable sulfur loading. With the enhanced electrochemical performance, the new cathode offers a promising avenue to fabricate high-performance Li-S batteries.

Strong charge polarization effect enabled by surface oxidized titanium nitride for lithium-sulfur batteries

The commercialization of high-energy-density and low-cost lithium-sulfur batteries has been severely impeded by capacity fading and electrochemical polarization. Here we report a strategy to entrap polysulfides and boost the cathodic redox kinetics by embedding the surface oxidized quantum-dot-size TiN (TiN-O) within the highly ordered mesoporous carbon matrix. While the carbon scaffold offers sufficient electrical contact to the insulate sulfur, benefiting the full usage of sulfur and physical confinement of polysulfides. The surface oxygen renders TiN-O with a strong charge polarization effect for polysulfides via S-O-Ti bond as verified experimentally and theoretically. The suppressed shuttle effect and high lithium ion diffusion coefficient (7.9 × 10−8 cm2 s−1) lead to a high capacity of 1264 mA h g−1 at 0.2 C with a negligible capacity fading rate of 0.06% per cycle. Additionally, TiN-O based prototype soft-package cells also exhibit excellent cycling stability with flexibility, demonstrating their potential for practical applications.

Enhanced cycling performance of a high-energy and low-cost lithium–sulfur battery with a sulfur/hardwood charcoal composite cathode material

Lithium–sulfur battery is an attractive candidate for advanced energy storage devices due to its high specific energy of 2600 Wh kg−1 arising from the high theoretical specific capacity (1675 mAh g−1) of the sulfur cathode. However, short cycle life and low cycling efficiency are still the main obstacles preventing the practical development of this promising battery system. In this work, we show that a low-cost Li/S cell employing an activated hardwood charcoal–sulfur (S–AHC) nanocomposite cathode can be operated for more than 300 cycles while still maintaining high specific capacity (600 mAh g−1) and coulombic efficiency of 97 %, achieved by a new formulation of liquid electrolyte containing a fluorinated solvent. Such an improved capacity retention and cycle life, as compared to its conventional counterparts, prove that active mass lost via polysulfide dissolution can be effectively inhibited by utilization of this liquid electrolyte solution. Considering these results, we believe that the Li/S battery consisted of this composite cathode and the liquid electrolyte may be proposed as a promising candidate for low-cost energy storage applications.

A novel sulfur/carbon composite for low cost lithium–sulfur batteries with high cycling stability

Coconut shells were used as a starting material to prepare a novel C/S composite for low-cost Li–S batteries with high cycling performance.