Separator For Lithium-sulfur Batteries Research Articles

Modified separator engineering with 2D ultrathin Ni3B@rGO: Extraordinary electrochemical performance of the lithium-sulfur battery with enormous-sulfur-content cathode in low electrolyte/sulfur ratio

Compared to other batteries, a next-generation lithium-sulfur (Li-S) battery's specific capacity and energy density are relatively high. However, the actual electrochemical performance (particularly for the cell with a high cathode sulfur content and a lean electrolyte/sulfur ratio) falls well short of practical usage requirements. The ultrathin Ni 3 B@rGO-PP is designed in this study as a unique modified separator for Li-S cells. Because of its distinct electronic structure, the modified separator shows outstanding adsorption ability toward polysulfide through the boron element's active sites. Additionally, it has excellent electrocatalytic activity, significantly enhancing the performance of Li-S batteries. After the 100th cycle, the cell with 80 wt% sulfur content can retain 819 mA h g −1 under 0.2 C. Also, when the electrolyte/sulfur ratio is reduced to 15 µL mg −1 and 5 µL mg −1 , respectively, considerable capacity retention of 736.3 mA h g −1 and 615 mA h g −1 is achieved after the 100th cycle at 0.2 C. What's more, for the high sulfur loading (single-side up to 4.5 mg cm −2 ) cathode, the cell obtains a retention capacity of 578 mA h g −1 after the 200th cycle under 0.2 C. The surface engineering strategy with the Ni 3 B@rGO modified coating adopted in this work would open an efficient route to acquire the Li-S battery's outstanding electrochemical capability in the practical application situation. The boron element's active cites provide a unique electronic structure to the Ni 3 B@rGO coating layer, which effectively enhance the adsorption ability toward polysulfide, and further provide excellent electrocatalytic activity during the charging/discharging process, greatly improving the electrochemical performance of Li-S batteries. Thus, the Ni 3 B@rGO-PP exhibits long cycling stability even at a low E/S ratio, fast Li + transportation, and high ionic conductivity. • The Ni 3 B@rGO nanohybrid developed as a novel modified coating on the celgard separator in Li-S batteries. • The Ni3B@rGO-PP show outstanding adsorption ability to LiPSs through B active cites and enhances the cell conductivity. • The Ni 3 B@rGO-PP exhibits excellent anti-self-discharge, high ionic conductivity, and fast Li + transportation. • The Ni3B@rGO-PP presents promising electrochemical performances with a high-sulfur-content cathode (up to 83 wt%).

Flexible and free-standing bacterial cellulose derived cathode host and separator for lithium-sulfur batteries

This study demonstrates flexible, ultra-high rate, and long cycle life lithium‑sulfur batteries using bacterial cellulose (BC) derived cathode host as well as separator. The work also includes a new strategy to use active sulfur in the form of catholyte added directly to the electrolyte for improved sulfur utilization. The fabricated LiS cell with carbonized bacterial cellulose (CBC) as a cathode host and BC as a separator (CBC@BC) delivers an impressive capacity of 740 mAh g−1 at 1C. It retains a capacity of 310 mAh g−1 even at an ultra-high rate of 4C. To have commercial adoption of CBC@BC, we tested LiS cells with a high areal loading of 5 mg cm−2. The cell shows promising electrochemical performance for 500 cycles with a capacity retention of 82 %. Furthermore, first-principle calculations are performed to understand the interaction of soluble lithium-polysulfides with bacterial cellulose-derived material.

Composite cathodes and modified separators based on corn-silk-based porous carbon for high performance lithium–sulfur batteries

Corn by-products have been widely studied as a precursor of biomass carbon in energy storage systems. Without further doping or coating processes corn silk can achieve a high electrochemical performance when used as an anode of sodium and potassium ion batteries. Nonetheless, there is no report about corn silk used as a cathode for lithium-sulfur batteries. In this work, corn silk was made into porous carbon and used as sulfur scaffolds and modified materials for commercial separator in lithium-sulfur batteries. Corn silk possesses a natural pipe shape which grants the porous carbon a high specific surface area. With a simple dissolution crystallization method approximately 80% of the sulfur could be easily accommodated onto the porous carbon. The hierarchic pores not only limited the particle size of the sulfur to nanometers, but also buffered the volume expansion of sulfur and absorbed it tightly. Furthermore, with an ultralight porous carbon modified separator, significant improvement was achieved in the utilization of sulfur, cycling stability and alleviation of the polysulfide shuttling efficiently. The batteries delivered a specific capacity of 1290 mAh g-1 in the first discharge and 746 mAh g-1 after 100 cycles. The good electrochemical performance can be ascribed to the rational design of battery configuration.

Constructing Atomic Fe and N Co-doped Hollow Carbon Nanospheres with a Polymer Encapsulation Strategy for High-Performance Lithium-Sulfur Batteries with Accelerated Polysulfide Conversion.

As competitive next-generation rechargeable batteries, lithium-sulfur batteries (LSBs) suffer from the shuttle effect and the sluggish kinetics of intermediate polysulfides during charge and discharge processes, adversely affecting their electrochemical performances and actual applications. Herein, we demonstrate a polymer encapsulation strategy to synthesize atomic Fe and N co-doped hollow carbon nanospheres (Fe-NHC) with Fe-Nx sites for modifying commercial PP separator of LSBs to suppress the shuttle effect and promote the kinetics of intermediate polysulfides. Benefiting from the excellent structural design, the doped-N with positive charges could effectively adsorb negatively charged soluble polysulfides, help attract the soluble polysulfides to the Fe atoms and boost the catalytic transformation of the soluble polysulfides. Additionally, such a thin carbon shell could provide a short mass diffusion pathway and hence promote the adsorption and the catalytic conversion. Therefore, the battery with the Fe-NHC/PP separator delivers outstanding cycling and rate performances. At the large current density of 1 C, the specific capacity is 1079 mA h g-1 and maintains a low loss of 0.076 % per cycle within 500 cycles. Even at a harsh current density of 4 C, a high capacity of 824 mA h g-1 is still achieved, indicating the advantage of the Fe-NHC/PP separator in LSBs.

High absorption and fast polysulfides conversion of duel functional separator based on mesoporous-WC/rGO composite for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are next-generation energy storage devices owing to their high specific capacities and energy densities; however, critical problems remain unsolved, such as insulating sulfur as an active material and the dissolution of Li polysulfides into the liquid electrolyte during cycling, leading to low sulfur utilization, low rate performance, and rapidly decreasing capacity. Herein, we describe the synthesis of a nanocomposite structure comprising mesoporous tungsten carbide (meso-WC) and reduced graphene oxide (rGO) (meso-WC/rGO) and its application to an functional separator in LSBs. The resulting Li-S cell exhibits improved rate cycling performance: ~950 mAh g-1 at 1 C after 100 cycles. Moreover, even at a high sulfur loading of 3.0 mg cm-2, the Li-S cell with the meso-WC/rGO maintains enhanced performance, with a capacity of ~737 mAh·g-1 and a retention of 83% after 300 cycles. The Li-polysulfide shuttle effect was observed using H-type cells and adsorption tests. The enhanced performance results from suppression of the shuttle effect caused by the excellent adsorption of Li polysulfides, effective reuse of active materials, and promotion of the conversion reaction.

Multi-duties for one post: Biodegradable bacterial cellulose-based separator for lithium sulfur batteries

High-energy density lithium sulfur battery containing highly active materials is more prone to safety hazards. Besides, the infamous shuttle effect of lithium polysulfides (LiPSs) and listless redox kinetic limit its practical applications. Here, a “one-for-all” design concept for separator enabled by interfacial engineering is proposed to relieve the bottlenecks. For one thing, porous bacterial cellulose (PBC) membrane with high thermostability (no shrinking at 200 °C) and puncture resistance was employed to ensure the battery's safety. For another, a difunctional Ti3C2Tx-SnS2 modified layer could capture LiPSs through lewis-acid interaction and promoted the redox kinetics by catalytically active sites. The symmetric cell with anchoring-electrocatalysis Ti3C2Tx-SnS2-PBC separator infiltrated with the electrolyte delivered an ionic conductivity of 2.171 mS/cm at a high temperature of 180 °C. And a capacity retention is improved by 71.2% compared with PP separator. This work furnishes a facial engineering strategy for manufacturing a multifunctional separator for lithium sulfur batteries.

Constructing Interlayers with Micro-Nano Particles to Enhance the Fire Safety and Polysulfide Adsorption Ability of Polypropylene Separators for Lithium-Sulfur Batteries

Constructing Interlayers with Micro-Nano Particles to Enhance the Fire Safety and Polysulfide Adsorption Ability of Polypropylene Separators for Lithium-Sulfur Batteries

Multifunctional Hyphae Carbon Powering Lithium-Sulfur Batteries.

Biotechnology can bring new breakthroughs on design and fabrication of energy materials and devices. In this work, a novel and facile biological self-assembly technology to fabricate multifunctional Rhizopus hyphae carbon fiber (RHCF) and its derivatives on a large scale for electrochemical energy storage is proposed. Crosslinked hollow carbon fibers are successfully prepared by conversion of Rhizopus hyphae, and macroscopic production of centimeter-level carbon balls consisting of hollow RHCFs is further realized. Moreover, the self-assembled RHCF balls show strong adsorption characteristics on metal ions and can be converted into a series of derivatives such as RHCF/metal oxides. Notably, the designed RHCF derivatives are demonstrated with powerful multifunctionability as cathode, anode, and separator for lithium-sulfur batteries (LSBs). The RHCF can act as the host material to combine with metal oxide (CoO) and S, Li metal, and a polypropylene (PP) separator to form a new RHCF/CoO-S cathode, an RHCF/Li anode, and an RHCF/PP separator, respectively. Consequently, the optimized LSB full cell presents excellent cycling performance and superior high-rate capacity (881.3mA h g-1 at 1 C). This work provides a new method for large-scale preparation of hollow carbon fibers and derivatives for advanced energy storage and conversion.

Nickel‐Based Materials for Advanced Rechargeable Batteries

AbstractThe rapid development of electrochemical energy storage (EES) devices requires multi‐functional materials. Nickel (Ni)‐based materials are regarded as promising candidates for EES devices owing to their unique performance characteristics, low cost, abundance, and environmental friendliness. This review summarizes the scientific advances of Ni‐based materials for rechargeable batteries since 2018, including lithium‐ion/sodium‐ion/potassium‐ion batteries (LIBs/SIBs/PIBs), lithium–sulfur batteries (LSBs), Ni‐based aqueous batteries, and metal–air batteries (MABs). The Ni‐based materials are mainly classified by the various roles of anodes and cathodes for LIBs and SIBs, cathode hosts and separators for LSBs, cathodes for Ni‐based aqueous batteries, and catalysts for MABs, focusing on the relationship between the compositions, structures, and electrochemical performance. Finally, the challenges and prospects of Ni‐based materials for rechargeable batteries are briefly discussed.

Well-dispersed Li2CoTi3O8 nanoparticles as a multifunctional material for lithium-ion batteries and lithium-sulfur batteries

Cubic spinel Li4Ti5O12 is a desired anode material for lithium-ion batteries (LIBs) due to high stability (the feature of “zero strain”) and good safety. Moreover, Li4Ti5O12 has a good affinity with sulfur for restraining lithium polysulfides (LiPSs) by the Ti-S bond in lithium-sulfur batteries (LSBs). Interestingly, extra cobalt element is introduced to form Li2CoTi3O8, which not only increases theoretical capacity for LIBs but also enhances the adsorption of sulfur for LSBs. In this paper, Li2CoTi3O8 nanoparticles are synthesized via a sol-gel method. As the anode for LIBs, Li2CoTi3O8 displays a desired specific capacity (335.3 mAh g−1 at 0.2 A g−1) and a better rate-capability (188.5 mAh g−1 at 5 A g−1; no capacity decay over 400 cycles), which is superior to electrochemical performances of the reported same substances. Besides, Li2CoTi3O8 nanoparticles are designed as both the sulfur host material and the modified separator in LSBs for the first time. Under the LCTO-coated separator, the Li2CoTi3O8/S electrode achieves a first capacity of 1048 mAh g−1 at 0.5 C and the stable capacity retention (732.7 mAh g−1 after 100 cycles). The enhanced performance of the Li2CoTi3O8 electrode is the result of synergistic effect of dispersed particles and larger contact area for LIBs and LSBs.

Design of a Metal–Organic Framework‐Derived Co9S8/S Material for Achieving High Durability and High Performance of Lithium–Sulfur Batteries

AbstractEnhancing the durability and performance of high‐energy‐density lithium–sulfur batteries (LSBs) is of paramount important for energy storage. We have fabricated a metal–organic framework‐derived (MOF) Co9S8/S (cobalt sulfide/sulfur) modified separator in LSBs which displays highest durability and excellent performance. The material successfully suppresses polysulfide shuttling, which is a determining factor in the deterioration of performance and lifetime of a battery. The Co9S8/S material is derived from a Co‐MOF. Its porosity and structural features make it an efficient material for capturing lithium polysulfides (LiPS), which is involved in chemical interactions with polarities within Co9S8/S. The kinetics of redox reactions involving LiPS are facilitated by the conductive properties of the material. A prolonged cycle life of 2000 charge–discharge cycles at a 1 C‐rate is observed when Co9S8/S is applied to the surface of a separator in the LSBs. An excellent discharge capacity of 879 mAh g−1 with the coulombic efficiency being maintained above 85 % throughout the course of 2000 charge–discharge cycles at a 1 C‐rate is achieved. Our strategy results in a material with unpresented high stability and durability of a MOF‐derived material which have fundamental importance in industrial and future commercialization of LSBs.

High thermal stability multilayered electrolyte complexes via layer-by-layer for long-life lithium-sulfur battery

In this work, polyacrylonitrile/sulfonated poly(ether ether ketone) (PAN/SPEEK) composite fiber membrane as separator for lithium-sulfur battery was first prepared by electrospinning. In order to reduce the shuttle effect, multilayered polyelectrolyte complexes (CS/CNTs)n as surface modification agents were prepared by alternating deposition of oppositely charged hydroxylated multi-walled carbon nanotubes (MWCNTs-COOH) and chitosan (CS) via the layer-by-layer method. The as-prepared fiber multilayered complex separator (FMCS) was finally treated by heating at 120 °C to form cross-linked network for better thermal stability. FMCS possessed much higher porosity than that of the commercial PP separator (44%). As expected, the assembled membranes remained intact even at 150 °C, while PP separator shrunk severely. Compared with PP, PAN/SPEEK/(CS/MWNTs-COOH)10 showed the discharge capacity of 956.9 mAh/g at 0.1 C and maintained 463 mAh/g after 100 cycles with the capacity retention rate of 48.4% which is higher than that of the commercial PP separator. Thus, this work can provide a simple method for modifying separator for long-life lithium-sulfur battery.

Coral-like interconnected carbon aerogel modified separator for advanced lithium-sulfur batteries

Lithium-sulfur batteries (LiSBs) have attracted great interest owing to their ultrahigh theoretical capacity. However, the poor utilization of active substrate, caused by the shuttle effect of soluble polysulfide and poor electrochemical kinetics, hinders the commercial application of LiSBs. Herein, N-doping and ultrahigh surface area carbon aerogel in coral-like structure (NHCA) used as a modification of separator in LiSBs was successfully prepared by atmospheric pressure drying and activation subsequently. The introduction of NHCA not only block the shuttle effect of polysulfide with a similar effect of molecular sieve, but also built a low-resistance conductive network between the cathode and separator. After 200 cycles at 1 A/g, the capacity of cell with NHCA-7/Celgard was retained at 820 mAh/g, with just 0.13% decay per cycle. The research outcomes of this study provide a new insight for the interlayer modification of advanced LiSBs.

Magnetic and mesoporous Fe3O4-modified glass fiber separator for high-performance lithium-sulfur battery

Lithium-sulfur batteries are attractive for energy storage due to their ultrahigh theoretical energy density and low material cost. But the biggest factor impeding the development of the batteries is its rapid irreversible capacity decay due to the “shuttle effect.” To inhibit it, the glass fiber membrane modified by magnetic mesoporous Fe3O4 mixed with Ketjen black is designed and used as the separator for lithium-sulfur batteries in this work. The assembled battery using the modified separator exhibits an excellent initial capacity of 1274.5 mA h g−1 and a high coulombic efficiency of about 90% at 0.2 C first cycle. The improved performance of batteries can be ascribed to the good conductivity, mesoporosity, and magnetic property of Fe3O4 nanoparticles on the separator, which enables the trapping and activation of the soluble polysulfides in lithium-sulfur batteries. The work indicates that magnetic mesoporous Fe3O4 can open new avenues to improve the performance of lithium-sulfur batteries.

High sulfur loading application with the assistance of an extremely light-weight multifunctional layer on the separator for lithium-sulfur batteries

For high-energy density lithium-sulfur (Li-S) batteries, the effective active material loading, cyclic stability, and modification hardly any effect on energy density are crucial factors, but these three indicators seem contradictory in most case. In this paper, cells with a high sulfur loading, 4.3 mg cm−2, demonstrate excellent performances with the assistance of reduced graphene oxide (rGO) modified on the separator, and the density of modified layer is only 0.1 mg cm−2, which is hardly any effect on energy density. Moreover, in order to understand the improvement mechanism of the modified layer, graphene oxide (GO) modified layer is also to be applied for comparison, which is also helpful to establish cognition to select other modification layers. Most important of all, the application of high sulfur loading is generally required for practical Li-S batteries and the extremely light-weight modified layer is beneficial to the exertion of the whole energy density.

Functional double-layer membrane as separator for lithium-sulfur battery with strong catalytic conversion and excellent polysulfide-blocking

Lithium-sulfur (Li-S) battery with promising specific capacity and high energy density has attracted wide attention in recent years. However, the rapid capacity fading of the batteries caused by the “shuttle effect” of soluble polysulfides restricted its applications. Here, a novel thermostable double-layer membrane based on F-doped poly-m-phenyleneisophthalamide (PMIA) membrane and F-mangano-manganic oxide (Mn3O4) co-doped PMIA membrane is fabricated through electrospinning method. The F-PMIA membrane and F-Mn3O4-co-doped PMIA membrane in the double-layer membrane can act as the matrix to prepare gel polymer electrolyte (GPE). More importantly, the F-doped PMIA membrane in combination with F-Mn3O4-co-doped PMIA membrane, render the engineered functional separator with extraordinary high electrolyte uptake and eminent preserving liquid electrolyte, excellent thermal stability and shrinkage resistance, strong catalytic conversion, forceful chemisorption and physical blocking the “shuttle effect” of lithium polysulfides for Li-S battery. Based on these merits, the assembled batteries with the novel separator exhibited a high first-cycle discharge capacity with 1237.1 mAh g−1, excellent discharge capacity retention of 814.0 mAh g−1 and high Coulombic efficiency of 98.83% after 1000 cycles at the current density of 0.5 C rate. In addition, the obtained Li-S battery with GPE presented a low interfacial resistance and high rate capacity (624.1 mA h g−1 at 2 C rate after 600 cycles). The reasons of these excellent electrochemical performances for the battery using the prepared membrane were ascribed to the suppressed “shuttle effect” through both the physical trapping of lithium polysulfides by the GPE based as matrix on F-doped PMIA membrane and chemical binding of intermediates by F-Mn3O4-co-doped membrane. The new separator will open up an effective avenue to enhance the capability and cyclability of Li-S batteries.

High electrical conductivity of 3D mesporous carbon nanocage as an efficient polysulfide buffer layer for high sulfur utilization in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries display a high theoretical energy density compared with commercial lithium-ion batteries (LIBs). However, there are several major challenges including the poor conductivity and large volumetric expansion of sulfur, and the shuttle effect and uncontrollable deposition of lithium polysulfides, which lead to the low sulfur utilization and poor cycle life in practical applications. The fabrication of state-of-the-art separator based on high electrical conductivity of 3D porous carbon is believed to restrain the shuttle effect of lithium polysulfides and control the deposition of lithium sulfide. Herein, we report a kind of 3D mesporous carbon nanocage (PCN) with a high electrical conductivity as an efficient polysulfide buffer layer on PP separator in Li-S batteries for high sulfur utilization. The extraordinary electrical conductivity of the 3D PCN can promote the transformation reaction of Li2S/sulfur-to-lithium polysulfides between PCN separators and sulfur cathode. During charge/discharge, PCN serves as a buffer layer to redistribute the shuttling back of LiPSs owing to its abundant mesoporous structure. Thereby, Li-S batteries using PCN separator shows an extraordinary initial discharge capacity of 1044 mAh g−1 which still remains 652 mAh g−1 after 200 cycles at 1C. This is a significantly boost for sulfur utilization compared with that in Li-S batteries using PP separator. In addition, the advanced Li-S batteries with PCN separators reveal a superior areal capacity (2.5 mAh cm−2) at a high sulfur loading amount of 7.34 mg cm−2, showing the potential in practical application.

The Role of Cellulose Based Separator in Lithium Sulfur Batteries

In this work, abundant and environmentally friendly nano-fibrillated (NFC) cellulose is used for fabrication of porous separator membranes according to the procedure adopted from papermaking industry. As-prepared NFC separators were characterized in terms of thickness, porosity, wettability, electrochemical stability and electrochemical performance in lithium-sulfur and Li-symmetrical pouch cells and compared to a commercial Celgard 2320 separator membrane. Results demonstrated that morphology and electrochemical performance of NFC separator outperforms the conventional polyolefin separator. Due to exceptional interplay between lithium metal and cellulose, this research provides a self-standing NFC separator that can be used besides the lithium-sulfur also in other lithium metal battery configurations.

Double-Layered Modified Separators as Shuttle Suppressing Interlayers for Lithium-Sulfur Batteries.

The shuttling phenomena in lithium-sulfur batteries lead to drastic attenuation of the capacity. This can be suppressed effectively by modifying the separator. Herein, a double-layered separator composed of a macroporous polypropylene (PP) matrix layer and an arrayed poly(methyl methacrylate) (PMMA) microsphere retarding layer is designed as the separator for lithium-sulfur batteries. A sulfur positive electrode with the PP/PMMA separator exhibits a high initial capacity of 1100.10 mAh g-1 at a current density of 0.1 mA cm-2 along with a high Coulombic efficiency, which is higher than the corresponding first discharge capacity results obtained using the standard PP separator (948.60 mAh g-1). In the double-layered separator, the arrayed PMMA microspheres can inhibit the diffusion of polysulfides through physical and chemical adsorption, thereby improving the electrochemical performance of lithium-sulfur batteries. In addition, the PMMA microspheres enhance the affinity of the separator to the electrolyte, which will increase the adsorption of the electrolyte to the separator and accelerate the diffusion rate of lithium ions.

Effective Polysulfide Adsorption by Double Side Coated Separator in Lithium-Sulfur Batteries

Effective Polysulfide Adsorption by Double Side Coated Separator in Lithium-Sulfur Batteries