Red Phosphorus Anchored on Nitrogen-Doped Carbon Bubble-Carbon Nanotube Network for Highly Stable and Fast-Charging Lithium-Ion Batteries.

A nitrogen-doped carbon bubble-carbon nanotube@red phosphorus (N-CBCNT@rP) network composite is fabricated, featuring an rP film embedded in a highly N-doped CBCNT network with hierarchical pores of different sizes and interior void spaces. Highly N-doped CBCNT with an optimized structure is utilized to achieve an ultrahigh rP content of 53 wt% in the N-CBCNT@rP composite by the NP bond, which shows a record rP content for rP-carbon composites by the vaporization-condensation process. When tested as an anode for lithium-ion batteries, the N-CBCNT@rP composite exhibits an ultrahigh initial Coulombic efficiency of 87.5%, high specific capacity, outstanding rate performance, and superior cycling stability at a high current density (capacity decay of 0.011% per cycle over 1500 cycles at 5 A g-1 ), which is the lowest capacity fading rate of those previously reported for rP-based electrodes. The superior lithium-ion storage performance of the N-CBCNT@rP composite electrode is primarily attributed to its structure. The 3D hierarchical conducting network of the N-CBCNT@rP composite with abundant N-P bonds endows the entire electrode with maximized conductivity for superior ion and electron transfer kinetics. Moreover, N-CBCNT networks with hierarchical pores of different sizes can fix the location of rP, prevent agglomeration, and avoid volume expansion of rP.

Boosting Charge Transfer Via Heterostructure Engineering of Ti2 CTx /Na2 Ti3 O7 Nanobelts Array for Superior Sodium Storage Performance.

The poor conductivity, inert charge transmission efficiency, and irreversible Na+ trapping of Na2 Ti3 O7 result in retardant electrons/ions transportation and deficient sodium-ion storage efficiency, leading to sluggish reaction kinetics. To address these issues, an urchin-like Ti2 CTx /Na2 Ti3 O7 (Ti2 C/NTO) heterostructure sphere consisting of Ti2 C/NTO heterostructure nanobelts array is developed via a facile one-step in situ hydrothermal strategy. The Ti2 C/NTO heterostructure can obviously decrease Na+ diffusion barriers and increase electronic conductivity to improve reaction kinetics due to the built-in electric field effect and high-quantity interface region. In addition, the urchin-like vertically aligned nanobelts can reduce the diffusion distance of electrons and ions, provide favored electrolyte infiltration, adapt large volume expansion, and mitigate the aggregation to maintain structural stability during cycles, further enhancing the reaction kinetics. Furthermore, the Ti2 C/NTO heterostructure can effectively suppress many unwanted side reactions between reactive surface sites of NTO and electrolyte as well as irreversible trapping of Na+ . As a result, systematic electrochemical investigations demonstrate that the Ti2 C/NTO heterostructure as an anode material for record sodium-ion storage delivers the highest reversible capacity, the best cycling stability with 0.0065% decay rate for 4500 cycles at 2.0 A g-1 , and excellent rate capability of 172.1 mAh g-1 at 10.0 A g-1 .

Enhancing the Electrochemical Performance of Sodium-Ion Batteries by Building Optimized NiS2 /NiSe2 Heterostructures.

NiS1.23 Se0.77 nanosheets closely attached to the internal surface of hollow mesoporous carbon sphere (HMCS) to form a NiS1.23 Se0.77 nanosheets embedded in HMCS (NSSNs@HMCS) composite as the anode of sodium ion batteries (SIBs) is reported by a facile synthesis route. The anode exhibits a superior reversible capacity (520 mAh g-1 at 0.1 A g-1 ), impressive coulombic efficiency (CE) of up to 95.3%, a high rate capacity (353 mAh g-1 at 5.0 A g-1 ), excellent capacity retention at high current density (95.6%), and high initial coulombic efficiency (ICE) (95.1%). Firstly, the highest ICE for NiS2 /NiSe2 -based anode can be ascribed to ultrathin layered structure of NiS1.23 Se0.77 nanosheet and highly efficient electron transfer between the active material and HMCS. Secondly, the optimized NiS2 /NiSe2 heterostructure at the nanoscale of the inside HMCS is formed after the first discharge/charge cycles, which can provide rich heterojunction interfaces/boundaries of sulfide/selenides to offer faster Na+ pathways, decrease the Na+ diffusion barriers, increase electronic conductivity, and limit the dissolution of polysulfides or polyselenides in the electrolyte. Finally, the hollow structure of the HMCS accommodates the volume expansion, prevents the pulverization and aggregation issues of composite materials, which can also promote outstanding electrochemical performance.

Stabilizing Lithium-Sulfur Batteries through Control of Sulfur Aggregation and Polysulfide Dissolution.

Lithium-sulfur (Li-S) batteries are investigated intensively as a promising large-scale energy storage system owing to their high theoretical energy density. However, the application of Li-S batteries is prevented by a series of primary problems, including low electronic conductivity, volumetric fluctuation, poor loading of sulfur, and shuttle effect caused by soluble lithium polysulfides. Here, a novel composite structure of sulfur nanoparticles attached to porous-carbon nanotube (p-CNT) encapsulated by hollow MnO2 nanoflakes film to form p-CNT@Void@MnO2 /S composite structures is reported. Benefiting from p-CNTs and sponge-like MnO2 nanoflake film, p-CNT@Void@MnO2 /S provides highly efficient pathways for the fast electron/ion transfer, fixes sulfur and Li2 S aggregation efficiently, and prevents polysulfide dissolution during cycling. Besides, the additional void inside p-CNT@Void@MnO2 /S composite structure provides sufficient free space for the expansion of encapsulated sulfur nanoparticles. The special material composition and structural design of p-CNT@Void@MnO2 /S composite structure with a high sulfur content endow the composite high capacity, high Coulombic efficiency, and an excellent cycling stability. The capacity of p-CNT@Void@MnO2 /S electrode is ≈599.1 mA h g-1 for the fourth cycle and ≈526.1 mA h g-1 after 100 cycles, corresponding to a capacity retention of ≈87.8% at a high current density of 1.0 C.

Constructing a Micrometer-Sized Structure through an Initial Electrochemical Process for Ultrahigh-Performance Li+ Storage.

Orthorhombic niobium pentoxide (T-Nb2O5) is a promising anode to fulfill the requirements for high-rate Li-ion batteries (LIBs). However, its low electric conductivity and indistinct electrochemical mechanism hinder further applications. Herein, we develop a novel method to obtain a micrometer-sized layer structure of S-doped Nb2O5 on an S-doped graphene (SG) surface (the composite is denoted S-Nb2O5/SG) after the initial cycle, which we call "in situ electrochemically induced aggregation". In situ and ex situ characterizations and theoretical calculations were carried out to reveal the aggregation process and Li+ storage process. The unique merits of the composite with a micrometer-sized layer structure increased the reaction degree, structural stability, and electrochemical kinetics. As a result, the electrode exhibited a large capacity (∼598 mAh g-1 at 0.1 A g-1), outstanding cycling stability (∼313 mAh g-1 at 5 A g-1 and remains at ∼313 mAh g-1 after 1000 cycles), and a high Coulombic efficiency and has a high fast-charging performance and excellent cycling stability.

Tailoring the Void Space Using Nanoreactors on Carbon Fibers to Confine SnS2 Nanosheets for Ultrastable Lithium/Sodium-Ion Batteries.

Herein, a rational design of SnS2 nanosheets confined into bubble-like carbon nanoreactors anchored on N,S doped carbon nanofibers (SnS2 @C/CNF) is proposed to prepare the self-standing electrodes, which provides tunable void space on carbon fibers for the first time by introducing hollow carbon nanoreactors. The SnS2 @C/CNF provides the stable support with greatly enhanced ion and electron transport, alleviates aggregation and volume expansion of SnS2 nanosheets, and promotes the formation of abundant exposed edges and active sites. The volume balance between SnS2 nanosheets and hollow carbon nanoreactors is reached to accommodate the expansion of SnS2 during cycles by controlling the thickness of SnO2 shells, which achieves the best space utilization. The doping of N,S elements enhances the wettability of the carbon nanofiber matrix to electrolyte and Li ions and further improves the electrical conductivity of the whole electrode. Thus, the SnS2 @C/CNF benefits greatly in structural stability and pseudocapacitive capacity for improved lithium/sodium storage performance. As a result of these improvements, the self-standing SnS2 @C/CNF film electrodes exhibit the highly stable capacity of 964.8 and 767.6 mAh g-1 at 0.2 A g-1 , and excellent capacity retention of 87.4% and 82.4% after 1000 cycles at high current density for lithium-ion batteries and sodium-ion batteries, respectively.

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium-Sulfur Batteries.

Catalysis has been regarded as an effective strategy to mitigate sluggish reaction kinetics and serious shuttle effect of Li-S batteries. Herein, a spherical structure consists of ultrathin layered Ti3C2Tx-TiN heterostructures (MX-TiN) through in-situ nitridation method is reported. Through controllable nitridation, highly conductive TiN layer grew on the surface and close coupled with interior MXene to form unique 2D heterostructures. The ultrathin heterostructure with only several nanometers in thickness enables outstanding ability to shorten electrons diffusion distance during electrochemical reactions and enlarge active surface with abundant adsorptive and catalytic sites. Moreover, the (001) surface of TiN is dominated by metallic Ti-3d states, which ensures fast transmitting electrons from high conductive MX-TiN matrix and thus guarantees efficient catalytic performance. Calculations and experiments demonstrate that polysulfides are strongly immobilized on MX-TiN, meanwhile the bidirectional reaction kinetics are catalytically enhanced by reducing the conversion barrier between liquid LiPSs and solid Li2S2/Li2S. As a result, the S/MX-TiN cathode achieves excellent long-term cyclability with extremely low-capacity fading rate of 0.022% over 1000 cycles and remarkable areal capacity of 8.27 mAh cm-2 at high sulfur loading and lean electrolytes.

Co0.85Se particles encapsulated in the inner wall of nitrogen-doped carbon matrix nanotubes with rational interfacial bonds for high-performance lithium-ion batteries.

Cobalt selenides based on the conversion reaction have been widely applied in lithium-ion batteries (LIBs) due to their high conductivity and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se/Co dissolution and serious volume change during the cycling process is still a challenge. Herein, a facile and efficient self-generated sacrificial template method is used to prepare Co0.85Se nanoparticles encapsulated in the inner wall of N-doped carbon matrix nanotubes (Co0.85Se@NCMT). In this strategy, the formation of stable Co-N/C and Se-C as well as enhancing the mechanical strength between active materials and N-doped carbon matrix nanotubes can critically affect the performance through suppressing the dissolution of Se/Co, decreasing energy band, promoting the shuttling of the ions/e- moving and mitigating the volume expansion during the charge-discharge process, which play a key role in improving the structure stability and electrochemical performance. Besides, Co0.85Se nanoparticles encapsulated in the robust carbon matrix inner wall can ensure good electron transfer and prevent the aggregation of nanoparticles, leading to superior electrochemical reversibility. Finally, carbon matrix nanotubes can provide sufficient space to effectively accommodate the volume changes of encapsulated Co0.85Se nanoparticles, thereby improving the cyclic stability. Based on the above advantages, as expected, the electrochemical investigations exhibited that the Co0.85Se@NCMT anode performs a stable reversible capacity of 462.9 mA h g-1 at a large current density of 5 A g-1 and a remarkable capacity retention of 99.5% after 800 cycles, suggesting its promising potential for the anode of LIBs.

Engineering oxygen vacancies and surface chemical reconstruction of MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays for advanced aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (ZIBs) are emerging as promising alternatives among various energy storage devices. However, the lack of research on cathode materials with both high capacity and electrochemical stability restricts widespread applications of ZIBs. Herein, surface chemical reconstruction and partial phosphorization strategies are employed to synthesize MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays on Ni foam substrates as cathodes for ZIBs. The unique hierarchical nanostructure and multiple components with exposed surfaces and rich oxygen vacancies accelerate charge transfer and ion diffusion, expose more active sites, and promote the accessibility between the active materials and electrolyte. The oxide/phosphide composites obtained by novel partial phosphorization achieve a common improvement of performance and stability. As expected, the CoO/Ni2P-Co2P electrode delivers a high specific capacity (370.4 mA h g-1 at 3 A g-1) and excellent rate performance (63.3% retention after a six-fold increase in the current density). Moreover, when employed as the cathode of the CoO/Ni2P-Co2P-30//Zn battery, the assembled battery exhibits a superior specific capacity (322.8 mA h g-1 at 2 A g-1), a long cycle life (104.9% retention after 6000 cycles), a favorable energy density (547.5 W h kg-1) and power density (9.7 kW kg-1). Therefore, this study provides a suitable candidate which meets the requirements of high-performance cathode materials for ZIBs.

Multifunctional NiCo2O4 nanosheet-assembled hollow nanoflowers as a highly efficient sulfur host for lithium-sulfur batteries.

Herein, a simple approach was developed to fabricate novel NiCo2O4 hollow nanoflowers (NCOHFs), which were explored as a sulfur carrier material for lithium-sulfur (Li-S) batteries. Remarkably, the capacity of the NCOHF/S composite electrode was ∼666.8 mA h g-1 in the fourth cycle, which was maintained at ∼432.9 mA h g-1 in the 400th cycle under a current density of 1.0C, with a low decay rate of 0.087% per cycle. The overall outstanding properties of the NCOHF/S composite are attributed to the successful new strategy in structural design via in situ and ex situ procedures. Firstly, NCOHF with bifunctional catalytic activity and chemical adsorption can efficiently promote the redox reactions of lithium polysulfides (LiPSs) and suppress the diffusion of polysulfides. Secondly, NCOHF with inherently high electronic conductivity acts as a conduit to accelerate the transport of electrons and ions. Thirdly, the flower-like NiCo2O4 nanosheets are anchored tightly to the conductive carbon and binder during the Li+ insertion and extraction processes, which can effectively suppress the aggregation of the NCOHF/S composite during cycling. Finally, the hollow space inside the NCOHF/S composite provides sufficient free space for the expansion of encapsulated pure sulfur.

Enhanced conductivity and structure stability of BiPO4@void@C/CNT particles for high-performance bismuth-based batteries.

Bismuth is a promising candidate for next generation lithium-ion battery anodes; however, the unstable structure of Bi during delithiation and lithiation processes leads to poor cycling performance. Here, a BiPO4@void@C/CNT composite is prepared using a template by corrosion and calcination methods. The composite has a uniform structure, where BiPO4 is converted into Bi nanoparticles embedded within the Li3PO4 matrix by the first discharge process inside the C/CNT hollow structures. The Li3PO4 matrix can not only serve as a buffer layer to maintain the structural integrity during insertion/extraction processes, but also provides an electrolyte-blocking layer that limits the formation of the SEI layer on the surfaces of most of the Bi nanoparticles. Moreover, the CNTs on the surface of BiPO4@void@C offer an interconnected electron transportation pathway and also effectively prevent aggregation and separation of the active materials. In addition, the hollow porous structure provides sufficient free voids for expansion of the Bi/Li3PO4 matrix nanorods. As an anode for LIBs, BiPO4@void@C/CNT after rating performance testing delivers a high capacity of ∼347.0 mA h g-1 at a high current density of 1000 mA g-1 that is maintained for 530 cycles without capacity loss.

High-efficiency and safe sulfur-doped iron oxides for magnetic resonance imaging-guided photothermal/magnetic hyperthermia therapy.

Heat therapy is a promising therapeutic modality for cancer treatment due to the minimum adverse effects of selective local hyperthermia; however, the low heating efficiency of heat therapy under safe conditions is an issue for its bioapplication. Here, we report the synthesis of water-dispersible sulfur doped iron oxides (SDIOs) with different phase structures and the exploration of the relationships between the different SDIOs and their induction heating capacities as a guideline to obtain a photo-magnetic hyperthermia agent. The agent exhibits good biocompatibility, excellent photothermal conversion efficiency (55.8%) and great T2 weighted magnetic resonance imaging (63.7 mM-1 s-1). Significantly, the SDIOs effectively eliminate tumours in a biologically safe AC magnetic field range (H·f = 4.3 < 5.0 × 106 kA m-1 s-1) and with 808 nm laser irradiation at a safe density of 0.33 W cm-2; also, they can be mostly metabolized from the body after one month. The work presented here adopts anion-doped iron oxides to dramatically improve photo-magnetic hyperthermia effects and may enable further exploration in thermotherapeutic research.

Graphene-Like Carbon Film Wrapped Tin (II) Sulfide Nanosheet Arrays on Porous Carbon Fibers with Enhanced Electrochemical Kinetics as High-Performance Li and Na Ion Battery Anodes.

SnS, is a promising anode material for lithium ion batteries (LIBs) and sodium ion batteries (SIBs), however, undergoes poor cyclic lifespan due to its huge volume changes and bad electroconductivity. Here, a modified CVD method is used to directly grow graphene-like carbon film on the surface of SnS nanosheet arrays which are supported by Co-, N-modified porous carbon fibers (CCF@SnS@G). In the strategy, the SnS nanosheet arrays confined into the integrated carbon matrix containing porous carbon fibers and graphene-like carbon film, perform a greatly improved electrochemical performance. In situ TEM experiments reveal that the vertical graphene-like carbon film can not only protect the SnS nanosheet from destruction well and enhance the conductivity, but also transforms SnS nanosheet into ultrafine nanoparticles to promote the electrochemical kinetics. Systematic electrochemical investigations exhibit that the CCF@SnS@G electrode delivers a stable reversible capacity of 529 mAh g-1 at a high current density of 5 A g-1 for LIBs and 541.4 mAh g-1 at 2 A g-1 for SIBs, suggesting its good potential for anode electrodes.

New Strategy for Specific Eradication of Implant-Related Infections Based on Special and Selective Degradability of Rhenium Trioxide Nanocubes.

The greatest bottleneck for photothermal antibacterial therapy could be the difficulty in heating the infection site directly and specifically to evade the unwanted damage for surrounding healthy tissues. In recent years, infectious microenvironments (IMEs) have been increasingly recognized as a crucial contributor to bacterial infections. Here, based on the unique IMEs and rhenium trioxide (ReO3) nanocubes (NCs), a new specific photothermal antibacterial strategy is reported. These NCs synthesized by a rapid and straightforward space-confined on-substrate approach have good biocompatibility and exhibit efficient photothermal antibacterial ability. Especially when they are utilized in antibiofilm, the expression levels of biofilm-related genes (icaA, fnbA, atlE, and sarA for Staphylococcus aureus) can be effectively inhibited to block bacterial adhesion and formation of biofilm. Importantly, the ReO3 NCs can transform into hydrogen rhenium bronze (HxReO3) in an aqueous environment, making them relatively stable within the low pH of IMEs for photothermal therapy, while rapidly degradable within the surrounding healthy tissues to decrease photothermal damage. Note that under phosphate-buffered saline (PBS) at pH 7.4 without assistant conditions, these ReO3 NCs have the highest degradation rate among all known degradable inorganic photothermal nanoagents. This special and IME-sensitive selective degradability of the ReO3 NCs not only facilitates safe, efficient, and specific elimination of implant-related infections, but also enables effective body clearance after therapy. Solely containing the element (Re) whose atomic number is higher than clinic-applied iodine in all reported degradable inorganic photothermal nanoagents under the PBS (pH 7.4) without any assistant condition, the ReO3 NCs with high X-ray attenuation ability could be further applied to X-ray computed tomography imaging-guided therapy against implant-related infections. The present work described here is the first to adopt degradable inorganic photothermal nanoagents to achieve specific antibacterial therapy and inspires other therapies on this concept.

Flower-like Fe7S8/Bi2S3 superstructures with improved near-infrared absorption for efficient chemo-photothermal therapy.

Although various photothermal therapy (PTT) nanoagents have been developed in recent years, the rational design and easy synthesis of a PTT nanoplatform with improved near-infrared (NIR) absorption have remained challenging. Herein, via a facile one-pot solvothermal strategy, hydrophilic nanosheet-assembled flower-like Fe7S8/Bi2S3 superstructures were fabricated successfully. Such nanoflowers exhibit improved NIR absorption, which is 1.54 times higher than that of pure Bi2S3 nanosheets at a wavelength of 808 nm. Attractively, these nanoflowers could serve as a drug delivery carrier with controlled release under pH/NIR stimuli and display a fascinating chemo-photothermal synergetic therapeutic effect both in vitro and vivo. The resulting nanoflowers may open up a way for the design of other nanoagents with an improved NIR absorption and chemo-photothermal cancer therapy effect.

Improving the cycling stability of lithium-sulfur batteries by hollow dual-shell coating.

Herein, a novel hybrid S@MnO2@C nanosphere, comprising sulfur nanoparticles encapsulated by a MnO2@C hollow dual-shell, is reported. Benefiting from a conductive C outer layer, the S@MnO2@C hybrid nanosphere provided highly efficient pathways for fast electron/ion transfer and sufficient free space for the expansion of the encapsulated sulfur nanoparticles. Moreover, the dual-shell composed of a MnO2 inner layer and a C outer layer coating on S not only improved the efficacious encapsulation of sulfur, but also significantly suppressed the dissolution of polysulfides during cycling. As a result, the S@MnO2@C electrode shows high capacity, high coulombic efficiency and excellent cycling stability. The S@MnO2@C cathode delivered a discharge capacity of 593 mA h g-1 in the fourth cycle and was able to maintain 573 mA h g-1 after 100 charge-discharge cycles at 1.0C, corresponding to a capacity retention of 96.6%.

UV and visible light synergetic photodegradation using rutile TiO2 nanorod arrays based on a p-n Junction.

Herein, we report a photocatalytic heterojunction device of rutile TiO2 nanorod arrays based on a p-n silicon junction (TiO2@PN) and its full absorption of ultraviolet and visible light for synergistic photodegradation. The fabricated TiO2@PN had excellent photocatalytic degradation of methyl orange (MO) under irradiation of a 300 W Xe lamp, and its pseudo-first-order rate constant k was 0.221 h-1, which was greatly higher than that for TiO2 nanorod arrays based on an n-p silicon junction (TiO2@NP, 0.078 h-1) and glass (TiO2@G, 0.032 h-1). The higher photocatalytic performance of TiO2@PN could be attributed to the fact that the photovoltage (PV) of the p-n junction promotes separation of the electron-hole pairs of the TiO2, and the holes are thus left within the TiO2 nanorods to produce a strong oxidant of hydroxyl radicals (˙OH). Moreover, this heterojunction device could be easily fabricated in a large size for easy recovery and recycling, which shows its promise in the solar-driven degradation of environmental pollution.