A Solid-Phase Conversion Sulfur Cathode with Full Capacity Utilization and Superior Cycle Stability for Lithium-Sulfur Batteries

Solid phase conversion sulfur cathode is an effective strategy for eliminating soluble polysulfide intermediates (LiPSs) and improving cyclability of Li-S batteries. However, realizing such a sulfur cathode with high sulfur loading and high capacity utilization is very challenging due to the insulating nature of sulfur. In this work, a strategy is proposed for fabricating solid phase conversion sulfur cathode by encapsulating sulfur in the mesoporous channels of CMK-3 carbon to form a coaxially assembled sulfur/carbon (CA-S/C) composite. Vinyl carbonate (VC) is simultaneously utilized as the electrolyte cosolvent to in-situ form a dense solid electrolyte interface (SEI) on the CA-S/C composite surface through its nucleophilic reaction with the freshly generated polysulfides at the beginning of initial discharge, thus separating the direct contact of interior sulfur with the outer electrolyte. As expected, such a CA-S/C cathode can operate in a solid phase conversion manner in the VC-ether cosolvent electrolyte to exhibit a full capacity utilization (1667 mA h g^-1 , ≈100%), a high rate capability of 2.0 A g^-1 and excellent long-term cyclability over 500 cycles even at a high sulfur loading (75%, based on the weight of CA-S/C composite), demonstrating great promise for constructing high-energy-density and cycle-stable Li-S batteries.

High-Performance Lithium Sulfur Batteries Based on Multidimensional Graphene-CNT-Nanosulfur Hybrid Cathodes

Although lithium-sulfur (Li-S) batteries are one of the promising candidates for next-generation energy storage, their practical implementation is limited by rapid capacity fading due to lithium polysulfide (LiPSs) formation and the low electronic conductivity of sulfur. Herein, we report a high-performance lithium-sulfur battery based on multidimensional cathode architecture consisting of nanosulfur, graphene nanoplatelets (2D) and multiwalled carbon nanotubes (1D). The ultrasonic synthesis method results in the generation of sulfur nanoparticles and their intercalation into the multilayered graphene nanoplatelets. The optimized multidimensional graphene-sulfur-CNT hybrid cathode (GNS58-CNT10) demonstrated a high specific capacity (1067 mAh g−1 @ 50 mA g−1), rate performance (539 @ 1 A g−1), coulombic efficiency (~95%) and cycling stability (726 mAh g−1 after 100 cycles @ 200 mA g−1) compared to the reference cathode. Superior electrochemical performances are credited to the encapsulation of nanosulfur between the individual layers of graphene nanoplatelets with high electronic conductivity, and effective polysulfide trapping by MWCNT bundles.

Stabilizing cathode structure via the binder material with high resilience for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have been considered as one of the most promising next-generation energy storage systems with high-energy density. The huge volumetric change of sulfur (ca. 80% increase in volume) in the cathode during discharge is one of the factors affecting the battery performance, which can be remedied with a binder. Herein, a self-crosslinking polyacrylate latex (PAL) is synthesized and used as a binder for the sulfur cathode of a Li-S battery to keep the cathode structure stable. The synthesized PAL has nano-sized latex particles and a low glass transition temperature (T g), which will ensure a uniform dispersion and good adhesion in the cathode. This crosslinking structure can provide fine elasticity to recover from the deformation due to volumetric change. The stable cathode structure, stemming from the fine elasticity of the PAL binder, can facilitate ion migration and diffusion to decrease the polarization. Therefore, the Li-S batteries with the PAL binder can function well with excellent cycling stability and superior C-rate performance.

Sepiolite/CNT/S@PANI composite with stable network structure for high performance lithium sulfur batteries

Composite materials with a stable network structure consisting of natural sepiolite (Sep) powders, carbon nanotubes (CNTs) and conductive polymer (PANI) have been successfully synthesized using a simple vacuum heat treatment and chemical oxidation method, and they have been used as cathode materials for lithium sulfur batteries. It is found that Sep/CNT/S@PANI composites possess high initial discharge capacity, good cyclic stability and good rate performance. The initial discharge capacity of the Sep/CNT/S@PANI-II composite is about 1100 mA h g⁻¹ at 2C, and remained at 650 mA h g⁻¹ after 300 cycles, and the corresponding coulombic efficiency is above 93%. Such performance is attributed to specific porous structure, outstanding adsorption characteristics, and excellent ion exchange capability of sepiolite, as well as excellent conductivity of CNT. Furthermore, the PANI coating has a pinning effect for sulfur, which enhances the utilization of the active mass and improves the cycling stability and the coulombic efficiency of the composites at high current rates.

The cathode composite materials for lithium sulfur batteries with a stable network structure consisting of natural sepiolite powders, carbon nanotubes and conductive polymer were synthesized by vacuum heat treatment and chemical oxidation method.

Ionothermal synthesis of graphene-based microporous carbon for lithium–sulfur batteries

Graphene-based microporous carbon with a high conductivity and diverse porous structure was designed via an ionothermal method for lithium–sulfur batteries.

Ultrathin Cobaltosic Oxide Nanosheets as an Effective Sulfur Encapsulation Matrix with Strong Affinity Toward Polysulfides

Two-dimensional ultrathin cobaltosic oxide nanosheets with numerous geometrical holes were synthesized by the hydrothermal method, and further used as an effective encapsulation matrix for sulfur and polysulfides in lithium-sulfur batteries. The cobaltosic oxide/sulfur nanosheet composite electrode exhibits high Coulombic efficiency (99%), a suppressed shuttle effect, and a reversible capacity of 656 mA h g^-1 at 0.2 C after 200 cycles, with small capacity fading of 0.219% per cycle, whereas its carbon-sulfur electrode counterpart only retains a capacity of 386 mA h g^-1 after 100 cycles. The improved performance is attributed to the strong chemical interaction between polysulfides and cobaltosic oxide, and its facile ionic transport and enhanced reaction kinetics, which can effectively control the diffusion of polysulfides and keep them within the cathode region, leading to good electrochemical stability.

A polymer enhanced sulfur/graphene aerogel as a no-slurry cathode for lithium–sulfur batteries

We presented a facile no-slurry method to synthesize a three-dimensional polyvinylpyrrolidone–sulfur/graphene aerogel composite, which can be pressed into flexible sheets and directly used as a cathode without any additives.

A novel compact cathode using sponge-like RANEY® nickel as the sulfur immobilizer for lithium–sulfur batteries

A novel sulfur immobilizer named RANEY® nickel is introduced for lithium–sulfur batteries for the first time.

Efficient Fabrication of Hierarchically Porous Graphene-Derived Aerogel and Its Application in Lithium Sulfur Battery

Hierarchically porous carbon/graphene aerogel (CGA) with relatively high surface area and pore volume is synthesized through an efficient fabrication strategy, which involves forming hydrothermal carbon layer on the pore wall as upholder and directly carbonizing the wet hydrogel from hydrothermal reaction, without using any special drying techniques. Cassava powder is used as carbon precursor which enables sustainable synthesis. Carbonizing the wet hydrothermal product is found to be a self-activation process, through which abundant pores are generated. The aerogel is used as host to encapsulate sulfur for lithium sulfur battery. Graphene, served as highly conductive scaffold, accelerates the transport of the electrons. The hierarchically porous structure is in favor of improving the electrochemical performance of lithium sulfur battery. Therefore, the cathode with high sulfur loading and high sulfur content can deliver very good performance.

A novel facile and fast hydrothermal-assisted method to synthesize sulfur/carbon composites for high-performance lithium–sulfur batteries

Hydrothermal-assisted sulfur impregnation method was first proposed to prepare sulfur/carbon (S/C) composites for lithium–sulfur (Li–S) battery applications.

Sandwich-type porous carbon/sulfur/polyaniline composite as cathode material for high-performance lithium–sulfur batteries

Sandwich-type porous carbon/sulfur/polyaniline (SPC–S–PANI) composite with active sulfur nanoparticles confined within porous carbon is prepared.

Mango stone-derived activated carbon with high sulfur loading as a cathode material for lithium–sulfur batteries

A mango stone-derived activated carbon/sulfur composite cathode with a high sulfur loading of 71 wt% for long cycle-life Li–S batteries.