Designing of trimetallic-phase ternary metal sulfides coupled with N/S doped carbon protector for superior and safe Li/Na storage

Fire-retardant and thermally conductive polyacrylonitrile-based separators enabling the safety of lithium-ion batteries

Lithium-ion batteries (LIBs) have broad application prospects in many fields because of their high energy density. However, the poor heat resistance of polyolefin membranes and uneven lithium deposition result in battery failure and even infamous thermal runaway behavior. To improve the intrinsic safety of batteries, fire-retardant, thermally conductive, electrospinning strategies are employed to acquire a functional polyacrylonitrile (PAN) nanofiber separator (PAN@FBN/TPP) containing modified boron nitride (FBN) and triphenyl phosphate (TPP). Compared with those of the Celgard separator, the porosity, contact angle, and electrolyte uptake of the Celgard separator are greatly improved. Moreover, the designed separator shows excellent thermal stability without shrinkage when heated at 220 °C. The char residue at 800 °C is 43.7 wt%, which is much greater than that of the Celgard separator (∼0.26 wt%). The maximal peak heat release rate (PHRRmax) is only 30 % that of the Celgard separator. The improvement in heat resistance laid a solid foundation for the preparation of high-safety LIBs. The advantages of a uniform pore size distribution and extremely high porosity provide abundant active sites and convenient channels for Li+ migration. The cell with the PAN@FBN/TPP separator shows excellent cycle stability and rate performance. Owing to the high heat resistance of PAN and the excellent flame-retardant capability of FBN, the LIBs presented the highest self-heating temperature (T0) and thermal runaway temperature (T1) and the smallest maximum temperature (Tmax) and heat release rate (HRRmax) in the safety performance test; compared with those of commercial separator batteries, the above thermal safety parameters increased by 16.9 %, 6.5 %, 21.8 % and 81.5 %, respectively. Overall, this work may provide an effective way to fabricate LIBs with high thermal safety.

Heterogeneous Engineering Strategy Derived In Situ Carbon-Encased Nickel Selenides Enabling Superior LIBs/SIBs with High Thermal Safety

Nowadays, the extended usage of lithium/sodium ion batteries (LIBs/SIBs) encounters nerve-wracking issues, including a lack of suitable reservoirs and high thermal runaway hazards. Although using TiO2 and Li4Ti5O12 has been confirmed to be effective in improving battery safety, their low theoretical capacities inevitably cause damage to the electrochemical performance of the battery. Achieving win-win results has become an urgent necessity. This study designed a metal-organic framework (MOF)-derived in situ carbon-coated metal selenide (Ni-Se@G@C) as the anode. When the current density is 0.1-0.3 A g-1, the initial capacity of LIBs reaches 993.2 mAh g-1, which increases to 1478.9 mAh g-1 after running 800 cycles. When running at 2 A g-1, the cell also offers a relatively high capacity of 458.3 mAh g-1 after 1500 cycles. After the replacement of graphite with Ni-Se@G@C, the self-heating temperature (T0) and thermal runaway triggering temperature (T1) of half and full cells are significantly increased. Meanwhile, the maximum thermal runaway temperature (T2) and maximal heating release rate (HRRmax) are significantly reduced. Of note, the usage of Ni-Se@G@C enables the battery with superior cycling and rate performance. When used in SIBs, the cell gives an initial discharge capacity of 624.9 mAh g-1, which still remains at 269.4 mAh g-1 after running 200 cycles at 1 A g-1. Notably, Ea of the Ni-Se@G@C cell is 5.6 times higher than that of the graphite cell, corroborating the promoted safety performance. This work provides a new paradigm for MOF-derived micro/nanostructures, enabling the battery with an excellent electrochemical and safety performance portfolio.

Catalytic chemistry inspired hollow carbon nanofibers loaded with NiS/Ni as high-performance and safe Li+ reservoir

Transition metal sulfides (TMSs) based anodes hold a very broad application prospect in lithium ion batteries (LIBs). In this work, the catalytic effect of metallic nickel at high temperature was used to generate hollow carbon nanofibers loaded with NiS and Ni (denoted as NiS/Ni@HCNF). The heteroatoms doped carbon fibers buffer the huge volumetric change of NiS during the discharge/charge process, and enhance the ion transport efficiency and electrical conductivity. In addition, the high specific surface area brought by the hollow carbon nanofibers can accelerate the electrolyte penetration and speed up the transport of ions as well as electrons. When used as anode of half cell, this electrode gives 958.5 and 612.9 mAh/g after running 1000 cycles under 1 and 2 A/g, showing the extremely-low attenuation rates of 0.0483 % per cycle and 0.0643 % per cycle, respectively. Impressively, NCM//NiS/Ni@HCNF battery shows the discharge capacity of 187.6 mAh/g at 1st cycle. Regarding the next 100 cycles, the relatively-high discharge capacities (>110 mAh/g) and coulombic efficiency (CE) values (>96 %) are discerned. It is noted that the usage of NiS/Ni@HCNF electrode improves the activation energy for thermal runaway, corroborating the elevated thermal safety of battery.

Facile synthesis of NiCoSe2@carbon anode for high-performance sodium-ion batteries

Sodium-ion batteries offer significant advantages in terms of low-temperature performance and safety. In this study, we present a straightforward synthetic approach to produce bimetallic selenide NiCoSe2 nanoparticles grown on a three-dimensional porous carbon framework for application as anode materials in sodium-ion batteries. This unique architecture enhances reaction kinetics and structural stability. The three-dimensional interconnected porous carbon network establishes a continuous pathway of electronic conductive, while increasing specific surface area and mitigating volume expansion. Consequently, these features expedite ion transfer and enhance electrolyte interaction. Notably, compared to CoSe, NiCoSe2 exhibits reduced ion transport distances and lower sodium diffusion barriers. Leveraging these attributes, NiCoSe2/N, Se co-doped carbon composite materials (NiCoSe2/NSC) demonstrate a high specific capacity of 320.8 mAh/g, even after 1000 cycles at 5.0 A/g, with a capacity retention rate of 85.1%. The study further delves into the revelation of the reaction mechanism and ion transport pathway through in-situ X-ray diffraction (XRD) analysis and theoretical calculations. The development of these anode materials is poised to pave the way for advancements in sodium-ion battery technology.

Amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron as new high-capacity and high-rate anode materials for sodium-ion half/full cells

In this study, amorphous MoS3-modified porous Co4S3-embedded N,S co-doped carbon polyhedron (Co4S3@NSC/MoS3) was rationally prepared via a multi-step method. One-dimensional linear-like MoS3 with a high specific capacity of 894 mAh g-1 and abundant active sites compensated for the low capacity of Co4S3, thus enhancing the sodium ion storage capacity of the entire electrode. Moreover, three-dimensional N,S co-doped carbon networks (NSC) significantly inhibited large volumetric fluctuations in Co4S3 and MoS3, thereby sustaining the structural stability and enhancing the electron transfer efficiency. As a new anode material for sodium-ion half batteries, the constructed Co4S3@NSC/MoS3 with rapid Na+ diffusion and charge transfer kinetics demonstrated better sodium storage properties than Co4S3@NSC. At a rate of 0.5 A g-1 over 100 cycles, the reversible specific capacity of Co4S3@NSC/MoS3 reached 594 mAh g-1. Even when cycled at a rate of 2 A g-1 for 600 cycles, the charge capacity was stable at 435 mAh g-1. The rate performance of Co4S3@NSC/MoS3 was also found to be remarkable; when the rate increased to 10 A g-1, the average capacity was retained at 382 mAh g-1. Apart from half cells, reduced graphene oxide (rGO)-modified Na3V2(PO4)3 composite (Na3V2(PO4)3@rGO) was used as the cathode material to match with Co4S3@NSC/MoS3. The assembled full batteries were analyzed and their electrochemical properties were discussed. They also exhibited outstanding rate capability and high-rate long-life cyclic property. Even at 1 A g-1 over 500 cycles, the discharge capacity was stably maintained at 246 mAh g-1. The outstanding sodium storage properties of Co4S3@NSC/MoS3 mainly depended on the cooperative effects of MoS3 and Co4S3@NSC, indicating the potential application of Co4S3@NSC/MoS3 in energy storage fields.

Trimetallic sulfides coated with N-doped carbon nanorods as superior anode for lithium-ion batteries

Metal sulfides have been considered promising anode materials for lithium-ion batteries (LIBs), due to their high capacity. However, the poor cycle stability induced by the sluggish kinetics and poor structural stability hampers their practical application in LIBs. In this work, MoS2/MnS/SnS trimetallic sulfides heterostructure coated with N-doped carbon nanorods (MMSS@NC) is designed through a simple method involving co-precipitation, metal chelate-assisted reaction, and in-situ sulfurization method. In such designed MMSS@NC, a synergetic effect of heterojunctions and carbon layer is simultaneously constructed, which can significantly improve ionic and electronic diffusion kinetics, as well as maintain the structural stability of MMSS@NC during the repeated lithiation/delithiation process. When applied as anode materials for LIBs, the MMSS@NC composite shows superior long-term cycle performance (1145.0 mAh/g after 1100 cycles at 1.0 A/g), as well as excellent rate performance (565.3 mAh/g at 5.0 A/g). This work provides a unique strategy for the construction of multiple metal sulfide anodes for high-performance LIBs.

Core-Shell Structure Trimetallic Sulfide@N-Doped Carbon Composites as Anodes for Enhanced Lithium-Ion Storage Performance

The high specific capacity of transition metal sulfides (TMSs) opens up a promising new development direction for lithium-ion batteries with high energy storage. However, the poor conductivity and serious volume expansion during charge and discharge hinder their further development. In this work, trimetallic sulfide Zn-Co-Fe-S@nitrogen-doped carbon (Zn-Co-Fe-S@N-C) polyhedron composite with a core-shell structure is synthesized through a simple self-template method using ZnCoFe-ZIF as precursor, followed by a dopamine surface polymerization process and sulfidation during high-temperature calcination. The obvious space between the internal core and the external shell of the Zn-Co-Fe-S@N-C composites can effectively alleviate the volume expansion and shorten the diffusion path of Li ions during charge and discharge cycles. The nitrogen-doped carbon shell not only significantly improves the electrical conductivity of the material, but also strengthens the structural stability of the material. The synergistic effect between polymetallic sulfides improves the electrochemical reactivity. When used as an anode in lithium-ion batteries (LIBs), the prepared Zn-Co-Fe-S@N-C composite exhibits a high specific capacity retention (966.6 mA h g-1 after 100 cycles at current rate of 100 mA g-1) and good cyclic stability (499.17 mA h g-1 after 120 cycles at current rate of 2000 mA g-1).

Copper sulfides (Cu7S4) nanowires with Ag anchored in N-doped carbon layers optimize interfacial charge transfer for rapid water sterilization

There are many methods of water disinfection, and how to realize low energy consumption, high efficiency and safety sterilization has always been a research hotspot. In this work, Cu7S4 nanowires were grown on copper foam, and coated with N-doped carbon layer and Ag particles, which not only improved the conductivity and local field enhancement regions of the material, but also improved the durability and mechanical stability of Cu7S4. DFT (Density functional theory) calculation shows that different kinds of N doping make the electron difference density and work function of the surrounding C different, which leads to high carrier transport capacity at the interface, and Ag anchored in N-doped carbon films can adsorb O2. The band gap of the material is 2.12 eV, and the material has the potential to generate superoxide anion under energy excitation. Under the condition of 6 V voltage and 1000 mL min-1 water flow rate, the long-term water filtration sterilization of high-concentration bacteria can be realized, and the removal efficiency can still reach 99% after 8 h continuous treatment. This work has great application prospects for the purification of highly polluted water in the future.

Three-dimensional micro-nanostructures based on binary transitional metal sulfides with doped carbon protector enabled high-performance and safe batteries

The lack of suitable Li⁺ reservoirs and the risk of thermal runaway have hindered the extended use of lithium-ion batteries. Although utilizing Li₄Ti₅O₁₂ or TiO₂ can improve the thermal safety, their low theoretical capacities compromise the electrochemical performance of the cell. In this study, a three-dimensional micro-nanostructure based on binary transitional metal sulfides (TMSs) with a doped carbon protector (SnS/Co₉S₈@HC) is designed. When operating at 0.1-1 A g^-1, the SnS/Co₉S₈@HC cell exhibits a high inceptive capacity of 1104.8 mAh g^-1 with a high coulomb efficiency of 97.1%. Even after 1000 cycles, it delivers a relatively-high capacity of 450.3 mAh g^-1, indicating a low capacity decay rate of 0.033% per cycle (from the 2nd to the 1000th cycle). The thermal runaway actions of the cells with graphite and SnS/Co₉S₈@HC anodes are investigated. The results demonstrate that the cell with the SnS/Co₉S₈@HC anode exhibits a significantly reduced maximum thermal runaway temperature of 473.5 ± 6.2℃ and maximum temperature increasing rate of 15.1 ± 0.6 °C min^-1 compared to the graphite cell. This indicates that SnS/Co₉S₈@HC cell holds higher thermal safety. The potential of SnS/Co₉S₈@HC as sodium ion batteries anode is also investigated. The results indicate an initial capacity of 631.7 mAh g^-1, with a low capacity decay rate of 0.063% per cycle when operating at 2 A g^-1. This work may be enlightening for constructing multi-phase TMSs based hierarchical structure towards superior and safe energy storage.