High-performance Li-S Batteries Research Articles

Nickel-embedded hierarchically-porous carbon microspheres as a multifunctional separator modifier for achieving advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs), one of the most promising electrochemical energy storage systems, are in the spotlight due to their high theoretical energy density, alongside environmental friendliness and low cost of sulfur. Several unforgiving issues, however, hamper their commercial applications, such as the notorious shuttle effect of intermediary polysulfides and retarded redox kinetics, growth of dendritic Li, among other things. The crux of sorting out the problems above is designing a versatile material with good electrical conductivity, catalytic activity, together with abilities in suppression of polysulfide shuttling and Li dendrite growth. In this work, a composite of Ni nanoparticles embedded in the gradient-porous carbon microspheres (Ni/PCMS), acting like a miniature reactor, was fabricated as a separator modification material. Adequate electron conductivity can be guaranteed by the carbon substrate and the inlays of Ni nanoparticles. The physical/chemical adsorption and high Li+ transference number of Ni/PCMS assure suppressed shuttle effect and Li dendrite growth, respectively. Catalytic activity is fulfilled with the exposed Ni active sites. As a consequence, the batteries based on Ni/PCMS-modified separators achieve a high initial discharge capacity of 1426.7 mAh g−1 at 0.1 C and a low capacity fading rate of 0.078% per cycle over 800 cycles at 1 C. Even under a high sulfur mass loading of ∼ 3.0 mg cm−2, the battery still displays a superior rate performance of 555.6 mAh g−1 at 0.5 C. This work provides a thought for the rational design of a wide range of separator modifiers for high-performance Li-S batteries.

Engineering Triple-Phase Interfaces Enabled by Layered Double Perovskite Oxide for Boosting Polysulfide Redox Conversion.

The electrocatalytic conversion of polysulfides is crucial to lithium-sulfur batteries and mainly occurs at triple-phase interfaces (TPIs). However, the poor electrical conductivity of conventional transition metal oxides results in limited TPIs and inferior electrocatalytic performance. Herein, a TPI engineering approach comprising superior electrically conductive layered double perovskite PrBaCo2O5+δ (PBCO) is proposed as an electrocatalyst to boost the conversion of polysulfides. PBCO has superior electrical conductivity and enriched oxygen vacancies, effectively expanding the TPI to its entire surface. DFT calculation and in situ Raman spectroscopy manifest the electrocatalytic effect of PBCO, proving the critical role of enhanced electrical conductivity of this electrocatalyst. PBCO-based Li-S batteries exhibit an impressive reversible capacity of 612 mAh g-1 after 500 cycles at 1.0 C with a capacity fading rate of 0.067% per cycle. This work reveals the mechanism of the enriched TPI approach and provides novel insight into designing new catalysts for high-performance Li-S batteries.

Encapsulation of sulfur inside micro-nano carbon/molybdenum carbide by in-situ chemical transformation for high-performance Li-S batteries

Encapsulation of sulfur inside micro-nano carbon/molybdenum carbide by in-situ chemical transformation for high-performance Li-S batteries

Bi‐Metallic Coupling‐Induced Electronic‐State Modulation of Metal Phosphides for Kinetics‐Enhanced and Dendrite‐Free Li–S Batteries (Adv. Funct. Mater. 14/2023)

Bi-Metallic Coupling In article number 2213310, Ming Li and co-workers report the in-situ construction of bi-metallic phosphides nanoparticles-anchored N, P-co-doped porous carbons (NiCoP-NPPC) by a laser-induced micro-explosion strategy, exhibiting the well-matched distribution of electronic-state modulation via Ni-Co coupling. The proposed bi-metallic coupling effect can realize kinetics-enhanced and dendrite-free Li-S batteries, thereby offering an effective approach for developing high-performance Li-S batteries.

Highly Connected Three-Dimensional Covalent Organic Framework with Flu Topology for High-Performance Li-S Batteries.

Lithium-sulfur batteries (LSBs) have been considered as a promising candidate for next-generation energy storage devices, which however still suffer from the shuttle effect of the intermediate lithium polysulfides (LiPSs). Covalent-organic frameworks (COFs) have exhibited great potential as sulfur hosts for LSBs to solve such a problem. Herein, a pentiptycene-based D2h symmetrical octatopic polyaldehyde, 6,13-dimethoxy-2,3,9,10,18,19,24,25-octa(4'-formylphenyl)pentiptycene (DMOPTP), was prepared and utilized as a building block toward preparing COFs. Condensation of DMOPTP with 4-connected tetrakis(4-aminophenyl)methane affords an expanded [8 + 4] connected network 3D-flu-COF, with a flu topology. The non-interpenetrated nature of the flu topology endows 3D-flu-COF with a high Brunauer-Emmett-Teller surface area of 2860 m2 g-1, large octahedral cavities, and cross-linked tunnels in the framework, enabling a high loading capacity of sulfur (∼70 wt %), strong LiPS adsorption capability, and facile ion diffusion. Remarkably, when used as a sulfur host for LSBs, 3D-flu-COF delivers a high capacity of 1249 mA h g-1 at 0.2 C (1.0 C = 1675 mA g-1), outstanding rate capability (764 mA h g-1 at 5.0 C), and excellent stability, representing one of the best results among the thus far reported COF-based sulfur host materials for LSBs and being competitive with the state-of-the-art inorganic host materials.

Facilitating polysulfide confinement using N-doped honeycomb-like carbon with high pyridinic-nitrogen content for high-performance Li-S batteries

Facilitating polysulfide confinement using N-doped honeycomb-like carbon with high pyridinic-nitrogen content for high-performance Li-S batteries

Selenium defects of 2D VSe2/CNTs composite as an efficient sulfur host for high-performance Li-S batteries

Introducing defects into two-dimensional materials can increase the ligand-unsaturated sites, thereby enhancing the redox catalysis of polysulphides. In this study, the selenium defects in the two-dimensional material VSe2 can effectively improve the electrochemical performance of lithium-sulfur batteries. Compared with VSe2, VSe2−x could strongly adsorb polysulfides, catalyze the conversion and accelerate the redox reactions of polysulfides. S/VSe2−x/CNTs cathode with an initial discharge specific capacity of 1457 mAh g−1 at 0.1 C current density and capacity decay rate per cycle of only 0.039% after 800 cycles at 0.5 C, showing excellent cycling stability. In addition, a high areal capacity of 4.35 mAh cm−2 and a reversible capacity of 4.106 mAh cm−2 after 100 cycles at 0.1 C can be achieved with the S/VSe2−x/CNTs cathode with a high areal sulfur loading of 4.5 mg cm−2. The results show that the shuttle effect is effectively suppressed by introducing defects in the two-dimensional transition metal dihalide compounds. Thus, the electrochemical performance of the sulfur electrode for lithium-sulfur batteries is improved. This work is expected to provide a new perspective for the rational design of sulfur host materials for high-performance lithium-sulfur batteries.

In situ composition of Thienothiophene-based covalent organic framework on carbon nanotube as a host for high performance Li-S batteries

Lithium-sulfur batteries (LSBs) is a promising secondary battery system with high energy density and environment-friendly characteristics, however, the severe “shuttle effect” and poor conductivity usually lead to short service life and low initial capacity. Carbon Nanotubes (CNTs) with excellent conductivity and large quantity of cavities are promising host materials, whereas, the weak interaction between CNTs and polysulfides usually leads to serious shuttle effect in charge/discharge processes. Herein, thienothiophene-based covalent organic framework is uniformly wrapped on the outer surface of CNTs to form a nanocomposite TT-BOST@CNT. It is observed that the coexistence of the electron-rich S, O and the electron-deficient B atoms enables the effective adsorption of both Li+ and Sx2− in lithium polysulfides (LiPSs). Studies reveal that the B, O and S atoms endow the nanocomposite with good catalysis ability, whereby, conversion of the insoluble long-chain polysulfides to the soluble short-chain polysulfides is accelerated. Consequently, the TT-BOST@CNT/S cathode displays outstanding electrochemical performance, with a high discharge specific capacity of 1545 mAh g−1 at 0.2 C and a small attenuation rate of 0.035% per cycle in 1000 cycles at 1 C.

Defect-Rich W/Mo-Doped V2O5 Microspheres as a Catalytic Host To Boost Sulfur Redox Kinetics for Lithium–Sulfur Batteries

It is very important to develop ideal electrocatalysts to accelerate the sulfur redox kinetics in both the discharging and charging processes for high-performance lithium-sulfur batteries. Herein, defect-rich cation-doped V2O5 yolk-shell microspheres are reported as a catalytic host of sulfur. The doping of W or Mo cations induces no impurities, broadens the lattice spacing of V2O5, and enriches the oxygen vacancy defects. Thus, the doped V2O5 host affords sufficient active sites for chemically anchoring polysulfides and promising catalytic effect on the mutual conversion between different sulfur intermediates. As a result, the S/W-V2O5 cathode delivers a discharging capacity of 1143.3 mA g-1 at an initial rate of 0.3 C and 681.8 mA g-1 at 5 C. Even under a sulfur loading of up to 5.5 mg cm-2 and a minimal electrolyte/sulfur ratio of 6 μL mg-1, the S/W-V2O5 cathode could still achieve good sulfur utilization and dependable cycle stability. Thus, this work offers an electrocatalytic host based on the cation doping strategy to greatly enhance the sulfur redox kinetics for high-performance Li-S batteries.

Two-dimensional sandwich-like MXene–conductive polymer nanocomposite with in-plane cylindrical mesopores for long cycling lithium-sulfur batteries

Li-S batteries have received much attention due to their high energy density, low cost and environmental friendliness. However, the poor conductivity of sulfur and the ‘shuttle effect’ of polysulfides still impede their practical applications. In this study, thin layered MXene nanosheets sandwiched by conductive poly(m-phenylenediamine) with in-plane cylindrical mesochannels (mPmPD/MXene) are constructed as sulfur hosts for the cathode materials of Li–S batteries. The polar active sites on MXene and mesoporous conductive PmPD polymers synergistically alleviate the polysulfide shuttling through chemisorption and physical confinement; the high metallic conductivity of MXene and conductive PmPD ensure the transport of electrons and promote the redox kinetics; the in-plane cylindrical mesochannels on mPmPD/MXene provide hosting space for high sulfur loading (∼71 wt%) and facilitate smooth electrolyte transport in the internal space of the cathode. Profiting from these advantages, the Li–S battery based on the mPmPD/MXene cathode exhibits a capacity decay of 0.0593% after 800 cycles at 1 C (53% capacity retention). The optimized battery shows stable cycling performance even at high sulfur loading (6.8 mg cm−2) with 5.6 mAh cm−2 capacity remained after 60 cycles at 0.1 C. This study provides insights for the rational design of 2D heterostructures with in-plane mesochannels for high-performance Li-S batteries.

Heterojunction interlocked catalysis-conduction network in monolithic porous-pipe scaffold for endurable Li-S batteries

The development of high-performance Li-S batteries is impeded by polysulfide (LiPS) shuttling effect and slow conversion kinetics. Building durable catalyst systems with rational adsorption-catalysis-conduction configurations to alleviate these problems still remains a challenge. Herein, a novel heterojunction interlocked catalysis-conduction strategy is proposed to prepare monolithic porous-pipe scaffold for LiPS accommodation. Therein the Co terminal of Co/Mo2C heterostructure catalyzes the in-situ growth of carbon nanotubes (CNTs). The Co-bridging effect reinforces the charge transfer from CNT to the catalytic Mo2C terminal of Co/Mo2C and avoids the coarsening of heterostructure nanodomains with superior anchoring and dispersing abilities. This high tap-density electrocatalytic scaffold (Co/Mo2C@CNTs) without excessive carbon residue as separator modifier enables the excellent rate capability and long cycling stability of Li-S batteries even under the pouch cell configuration, high sulfur loading and decreased electrolyte amount. This work also provides a novel top-down method to prepare mesoporous host with built-in conductive network from simple compact precursor via C3N4 vapor modulation.

Conductive metal–metal phase and built-in electric field of 1T-VSe2-MXene hetero-structure to accelerate dual-directional sulfur conversion for high-performance Li-S batteries

The shuttle effect and tardy redox kinetics of lithium-polysulfides (LiPSs) seriously restrict the electrochemical performance of lithium-sulfur batteries (LSBs). Here, 1T-VSe2-MXene hetero-structure catalysts with conductive metal–metal phase and built-in electric field (BIEF) as sulfur hosts are developed to accelerate the catalytic conversion of sulfur species. Theoretical and experimental analysis verify that because the difference of energy-level structure between conductive MXene and 1T-VSe2 drives the electron flow through the hetero-interface to construct the interfacial BIEF of metal–metal phase. In the effect of interfacial BIEF, more electrons are accumulated on Se surface sites, so enhancing Li-Se bonding for strong adsorption with LiPSs/Li2S. Meanwhile, the strengthened Li-Se bonding weakens the competing Li-S bonds in LiPSs/Li2S captured on the heterostructure, thus accelerating the dissociation of Li-S bonds yet reducing Li2S nucleation/decomposition energy barrier. Furthermore, abundant Li+ are quickly propelled at the BIEF of the hetero-interface with metal–metal phase, thereby offering a rapid Li+ transfer and boosting the redox kinetics of sulfur species. As expected, the S/1T-VSe2-MXene cathode displays a high reversible capacity of 1321 mAh g−1 at 0.1C, a superb long cyclic stability with a capacity decay of 0.058% per cycle for over 550 cycles at 0.5C, and a high initials areal capacity of 6.42 mAh cm−2 (sulfur loading: 6.9 mg cm−2) at 0.2C. This work reveals its absorption and catalytic conversion mechanism and offers an effective way to design conductively dual-directional Li-S catalysts for high-performance LSBs.

Theoretical Study on the Application of a Janus CoSTe Monolayer for Li-S Batteries

Li-S batteries show great promise for next-generation energy systems but suffer from sluggish reaction kinetics and the inevitable “shuttling effect” of dissolved lithium polysulfides (LiPSs). In this study, a structure model of a Janus CoSTe monolayer is constructed is to investigate the adsorption energy with LiPSs, adsorption decomposition energy, and diffusion barrier on Li2S for Li-S batteries. The results show that the adsorption energy of Li2Sn clusters on the surface of Janus CoSTe monolayers is much higher than that of graphite and organic electrolyte, and the decomposition of Li2Sn clusters cannot easily occur on the Janus CoSTe monolayer. Moreover, the diffusion of Li2Sn clusters on the surface of Janus CoSTe monolayers has its microscopic "channel", leading to the low dissociation energy of Li2S. Theoretically, the Janus CoSTe monolayer exhibits excellent catalytic capability for lithium-sulfur batteries and shows great potential to be an excellent anchoring material for high-performance Li-S batteries.

Synergetic effects of Fe[sbnd]N[sbnd]C and LiFePO4 in modified separator on improved adsorption and catalytic conversion reaction of soluble LiPSs for Lithium-sulfur batteries

“Shuttle effect” is a serious obstacle in the development of high-performance lithium-sulfur batteries and modified separator is considered an effective strategy to prevent the shuttle effect of soluble polysulfides (LiPSs). Herein, we demonstrate a modified polypropylene (PP) separator composed of nitrogen-doped carbon coated LiFePO4 (NC-LFP), Ketjen black carbon (KB) and polyvinylidene fluoride (PVDF) (NC-LFP interlayer), which can improve adsorption and catalytic conversion toward LiPSs. The analysis shows that NC-LFP interlayer could effectively adsorb LiPSs and therefore suppress its shuttle effects due to the FeNC functional groups in the nitrogen-doped carbon coated on LFP polar particles. The DFT analysis and the electrochemical performance test demonstrate the FeNC functional groups in NC-LFP interlayer provide lower activation barrier for catalytic conversion reaction of LiPSs to Li2S and vice versa. The coin cells with NC-LFP modified separator exhibit an initial discharge specific capacity of 907 mAh/g at 1C. After 500 cycles, the specific capacity is 702 mAh/g with a retention rate of 79.5 %. Moreover, at 8C rate, the discharge-specific capacity of 667.5 mAh/g is achieved. The use of NC-LFP interlayer modified separators realizes lithium-sulfur batteries with long-cycle life and high-rate performance, providing an emerging strategy for high-performance Li-S batteries.

Synergistic engineering of cobalt selenide and biomass-derived S, N, P co-doped hierarchical porous carbon for modulation of stable Li-S batteries

Hierarchical porous carbon co-doped with heterogeneous atoms has attracted much attention thanks to sizable internal void space accommodating electrolyte, high-density microporous structure physically confining polysulfides (LPS), and heterogeneous atoms serving as active sites to capture LPS. However, solely relying on carbon material defects to capture LPS proves ineffective. Hence, metal compounds must be introduced to chemisorb LPS. Herein, cobalt ions are in-situ grown on the polydopamine layer coated on the surface of biomass-derived S, N, P co-doped hierarchical porous carbon (SNP-PC). Then a layer of nitrogen-doped porous carbon (MPC) dotted with CoSe nanoparticles is acquired by selenizing. Thus, a strong-polar/weak-polar composite material of SNP-PC studded with CoSe nanoparticles is obtained ([email protected]@CoSe). Button cells assembled with [email protected]@CoSe-modified separator enable superb long-cycle stability and satisfactory rate performance. An excellent rate capacity of 796 mAh g−1 at a high current rate of 4 C with an ultra-low capacity fading of 0.06% over 700 cycles can be acquired. More impressively, even in a harsh test condition of 5.65 mg cm−2 sulfur loading and 4 μL mg−1 ratio of electrolyte to active materials, the battery can still display a specific capacity of 980 mAh g−1 (area capacity of ∼5.54 mAh cm−2) at 0.1 C. This work provides a promising route toward high-performance Li-S batteries.

Scissor g-C3N4 for high-density loading of catalyst domains in mesoporous thin-layer conductive network for durable Li-S batteries

The application of Li-S batteries (LSBs) is hindered by the undesired shuttle effect that leads to the fast consumption of active materials. The separator modification by using the carbon matrix with embedded metal nitride as catalyst can ease the problem. However, the previous synthesis processes of metal nitride catalysts are difficult to achieve a balance between their high-density production, homogenous distribution and excellent electronic contact with conductive substrates. Herein, we propose a bond scissoring strategy based on g-C3N4 to prepare NbN catalyst domains with high-density loading uniformly embedded in mesoporous thin-layer conductive carbon network (NbN/C) for durable LSBs. The molten salt reaction process is favorable for the diffusion of Nb cations into a porous g-C3N4 precursor to break the C-N bond and immobilize the N element. The residual monolithic carbon framework with space confinement effect limits the irregular growth and stacking of NbN precipitates. The NbN catalytic domains exhibit a strong adsorption effect on lithium polysulfides (LiPSs) and accelerate their liquid-solid conversion reactions. The LSBs utilizing an NbN/C-modified separator show superior cycling and rate performance, with a high-capacity retention of 72.7% after 1,000 cycles under 2 C and a high areal capacity of ~7.08 mA h cm-2 under a high sulfur loading of 6.6 mg cm-2. This g-C3N4-assisted strategy opens a new gate for the design of an integrated catalysis-conduction network for high-performance LSBs.

Uniting Young's modulus and the flexibility of solid-state electrolytes for high-performance Li-batteries at room temperature.

The use of solid-state composite electrolytes is a promising strategy to advance all-solid-state batteries. Great efforts have been devoted to improving the ionic conductivity of electrolytes, while little attention has been paid to studying the effect of their mechanical properties on electrochemical performance. The Young's modulus and flexibility are two important and contrary mechanical properties co-existing in electrolytes. Their effect on the electrochemical performance of all-solid-state batteries is important. Here, we study the effect of Young's modulus and flexibility based on a designed sandwich-structured solid-state composite electrolyte (SSCE) with high ionic conductivity (4.57 × 10-4 S cm-1 at 25 °C). In the SSCE, the middle layer with 9 : 1 : 0.5 mass ratio of Li6.4La3Zr1.4Ta0.6O12, poly(vinylidene fluoride-co-hexafluoropropylene) and bis(trifluoromethane)sulfonimide lithium is sandwiched by two outer layers with a 0.1 : 1 : 0.5 mass ratio among them, which can effectively suppress lithium dendrites and have intimate contact with the electrodes, leading to Li|SSCE|LiFePO4 with promising rate performance (155.5 mA h g-1 at 0.05 C and 124.4 mA h g-1 at 1 C) and excellent cycling stability with 98.8% capacity retention after 450 cycles at 25 °C. This work demonstrates that all-solid-state batteries have greatly enhanced electrochemical performance by uniting Young's modulus and flexibility via SSCEs, and provides a feasible strategy for the development of all-solid-state batteries.

Cobalt Nanocluster-Doped Carbon Micro-Spheres with Multilevel Porous Structure for High-Performance Lithium-Sulfur Batteries

Lithium-Sulfur batteries (Li-S batteries) have gained great interest in next-generation energy storage systems due to their high energy density and low-cost sulfur cathodes. There is, however, a serious obstacle in the commercial application of Li-S batteries due to the poor kinetics of the redox process at the sulfur cathode and the “shuttle effect” caused by lithium polysulfide (LiPSs). Herein, we report the synthesis of a sulfur cathode host material that can drastically inhibit the “shuttle effect” and catalyze the conversion of LiPSs by a simple electrostatic spray technique, namely, cobalt (Co) nanoclusters doped with N-containing porous carbon spheres (Co/N-PCSs). The results show that Co/N-PCSs has catalytic activity for the transformation of liquid LiPSs to solid Li2S and alleviates the notorious “shuttle effect.” This new sulfur cathode exhibits stable running for 300 cycles accompanied by a capacity of 650 mAh g−1 at a current density of 1 C, a capacity fading rate of 0.051% per cycle, and a Coulombic efficiency maintained at close to 100%. The results demonstrate that Co/N-PCSs offers the possibility of practical applications for high-performance Li-S batteries.

Ultrafast microwave synthesis of MoTe2@graphene composites accelerating polysulfide conversion and promoting Li2S nucleation for high-performance Li-S batteries

In this report, MoTe2 nanosheets were grown on highly conductive graphene support through a simple and ultrafast microwave-assisted chemical coupling and heating method to develop hybrid sulfur host materials for Li-S batteries. MoTe2 nanosheets with superb electrocatalytic activity combined with highly conductive graphene form a nano reservoir for containing elemental sulfur, intermediate polysulfide species, discharge product Li2S, and accelerating the electron transfer. Accordingly, the Li-S battery with the MoTe2@graphene@carbon cloth electrode exhibited a high initial discharge capacity of 1246 mAh g−1 at 0.2C for the first galvanostatic cycle, good cycle stability (98.7% capacity retention after 100 cycles at 0.2C) and superb rate performance. The synergistic effect of the chemical affinity and superior electrocatalytic capability of polar MoTe2, along with the effective physical confinement by graphene and free-standing carbon cloth, provides a promising way to design host materials to mitigate the shuttling effect in rechargeable Li-S batteries.

Cation-doped V2O5 microsphere as a bidirectional catalyst to activate sulfur redox reactions for lithium-sulfur batteries

An ideal electrocatalyst for sulfur redox reactions (SRRs) should afford an exception catalysis upon the conversion between different sulfur compounds during both discharge and charge processes. Herein, we report transition-metal (M = Fe, Co, Ni) doped V2O5 yolk-shell microspheres (M-V2O5-YS) as a bidirectional catalytic host of sulfur. After doping, the M-V2O5-YS samples show abundant lattice defects and improved conductivity. Moreover, the doped metal ions enrich the active sites for the adsorption-catalysis of sulfur species. Kinetics tests results demonstrate the role of bidirectional catalyst for M-V2O5-YS hosts in speeding up the kinetics of the reduction of LiPSs, as well as the re-oxidation of the deposited Li2S. In particular, the S/Co-V2O5-YS composite shows an outstanding initial discharge capacity up to 1168.1 mAh/g at 0.3 C, rate capability (693.7 mAh/g at 5 C) and cycle stability. Even at low E/S ratio (6 μL mg−1) and high sulfur loading (4.9 mg cm−2), S/Co-V2O5-YS composite still harvest excellent capacity and satisfactory cycle stability. Therefore, this study displays an effective and feasible method to explore bidirectional catalytic materials to activate SRRs for high performance Li-S batteries.