From Liquid to Solid-State Lithium Metal Batteries: Fundamental Issues and Recent Developments

The widespread adoption of lithium-ion batteries has been driven by the proliferation of portable electronic devices and electric vehicles, which have increasingly stringent energy density requirements. Lithium metal batteries (LMBs), with their ultralow reduction potential and high theoretical capacity, are widely regarded as the most promising technical pathway for achieving high energy density batteries. In this review, we provide a comprehensive overview of fundamental issues related to high reactivity and migrated interfaces in LMBs. Furthermore, we propose improved strategies involving interface engineering, 3D current collector design, electrolyte optimization, separator modification, application of alloyed anodes, and external field regulation to address these challenges. The utilization of solid-state electrolytes can significantly enhance the safety of LMBs and represents the only viable approach for advancing them. This review also encompasses the variation in fundamental issues and design strategies for the transition from liquid to solid electrolytes. Particularly noteworthy is that the introduction of SSEs will exacerbate differences in electrochemical and mechanical properties at the interface, leading to increased interface inhomogeneity-a critical factor contributing to failure in all-solid-state lithium metal batteries. Based on recent research works, this perspective highlights the current status of research on developing high-performance LMBs.

[Effect of recombinant human thrombin for hemostasis in liver resection: a randomized controlled phase Ⅲ clinical trial]

Objective: To evaluate the hemostatic efficacy, safety and immunogenicity of recombinant human thrombin in the treatment of liver wounds that still ooze after conventional surgical hemostasis. Methods: A multicenter, stratified randomized, double-blind, placebo-controlled phase Ⅲ trial with a planned enrollment of 510 subjects at 33 centers, with a 2∶1 randomization to the thrombin group versus the placebo group. An interim analysis will be conducted after approximately 70% of the subjects have completed the observation period. The primary efficacy endpoint was the rate of hemostasis within 6 minutes at the point of bleeding that could be evaluated. Safety analysis was performed one month after surgery, and the positive rates of anti-drug antibody (ADA) and neutralizing antibody were evaluated. Results: At the interim analysis, a total of 348 subjects had been randomized and received the study drug (215 were male and 133 were female). They were aged 19-69 (52.9±10.9)years. Among them, 232 were in the thrombin group and 116 were in the placebo group, with balanced and comparable demographics and baseline characteristics between the two groups. The hemostasis rate at 6 minutes was 71.6% (95%CI:65.75%-77.36%) in the thrombin group and 44.0% (95%CI: 34.93%-53.00%) in the placebo group, respectively (P<0.001). No grade≥3 drug-related adverse events and no drug-related deaths were reported from the study.No recombinant human thrombin-induced immunologically-enhanced ADA or immunologically-induced ADA was detected after topical use in subjects. Conclusion: Recombinant human thrombin has shown significant hemostatic efficacy and good safety in controlling bleeding during liver resection surgery, while also demonstrating low immunogenicity characteristics.

Fast Ionic Conducting Hydroxyapatite Solid Electrolyte Interphase Enables Ultra-Stable Zinc Metal Anodes

Zn metal has been extensively utilized as an anode in aqueous zinc-ion batteries attributed to its affordable cost and superior theoretical capacity. Nevertheless, the presence of dendrites and undesirable side reactions poses challenges to its widespread commercialization. To address these issues, herein, a surface coating composed of hydroxyapatite (HAP) was developed on the Zn anode to create an artificial solid electrolyte interphase. After the application of a hydroxyapatite layer, dendrites and corrosion of the Zn anode are sufficiently inhibited. Furthermore, the hydroxyapatite interphase with a low ionic diffusion barrier enables fast anodic redox kinetics. Consequently, the Zn@HAP symmetric cell possesses a durable lifespan over 2000 h at 1 mA cm-2, while maintaining minimal polarization. Moreover, the practical feasibilities of the Zn@HAP anode are also manifested in full batteries combined with MnO2 cathodes, exhibiting exceptional cycling performance up to 500 cycles at 1 A g-1 and excellent rate capability with a retention of 109 mAh g-1 at 5 A g-1.

Recent Advances and Perspectives of Lewis Acidic Etching Route: An Emerging Preparation Strategy for MXenes

Since the discovery in 2011, MXenes have become the rising star in the field of two-dimensional materials. Benefiting from the metallic-level conductivity, large and adjustable gallery spacing, low ion diffusion barrier, rich surface chemistry, superior mechanical strength, MXenes exhibit great application prospects in energy storage and conversion, sensors, optoelectronics, electromagnetic interference shielding and biomedicine. Nevertheless, two issues seriously deteriorate the further development of MXenes. One is the high experimental risk of common preparation methods such as HF etching, and the other is the difficulty in obtaining MXenes with controllable surface groups. Recently, Lewis acidic etching, as a brand-new preparation strategy for MXenes, has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations. However, a comprehensive review of Lewis acidic etching method has not been reported yet. Herein, we first introduce the Lewis acidic etching from the following four aspects: etching mechanism, terminations regulation, in-situ formed metals and delamination of multi-layered MXenes. Further, the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion, sensors and microwave absorption are carefully summarized. Finally, some challenges and opportunities of Lewis acidic etching strategy are also presented.

Freestanding and Flexible Interfacial Layer Enables Bottom-Up Zn Deposition Toward Dendrite-Free Aqueous Zn-Ion Batteries

Aqueous rechargeable zinc ion batteries are regarded as a competitive alternative to lithium-ion batteries because of their distinct advantages of high security, high energy density, low cost, and environmental friendliness. However, deep-seated problems including Zn dendrite and adverse side reactions severely impede the practical application. In this work, we proposed a freestanding Zn-electrolyte interfacial layer composed of multicapsular carbon fibers (MCFs) to regulate the plating/stripping behavior of Zn anodes. The versatile MCFs protective layer can uniformize the electric field and Zn²⁺ flux, meanwhile, reduce the deposition overpotentials, leading to high-quality and rapid Zn deposition kinetics. Furthermore, the bottom-up and uniform deposition of Zn on the Zn-MCFs interface endows long-term and high-capacity plating. Accordingly, the Zn@MCFs symmetric batteries can keep working up to 1500 h with 5 mAh cm^-2. The feasibility of the MCFs interfacial layer is also convinced in Zn@MCFs||MnO₂ batteries. Remarkably, the Zn@MCFs||α-MnO₂ batteries deliver a high specific capacity of 236.1 mAh g^-1 at 1 A g^-1 with excellent stability, and maintain an exhilarating energy density of 154.3 Wh kg^-1 at 33% depth of discharge in pouch batteries.

Facile Synthesis of Hybrid Anodes with Enhanced Lithium-Storage Performance Realized by a "Synergistic Effect"

Alloying-type anodes including Si- and Sn-based materials are considered the most exploitable anodes for high-performance lithium-ion batteries. However, problems of poor kinetics properties and structural failures such as grain pulverization and coarsening hinder their large-scale application. Herein, SnO₂/Si@graphite hybrid anodes, with nano-SnO₂ and nano-Si thoroughly mixed with each other and loaded onto graphite flakes, have been prepared by a facile ball milling method. Attributed to the "synergistic effect" between SnO₂ and Si, the mechanical stability and kinetics properties can be remarkably enhanced. Furthermore, graphite substrate supplies a fast electrically conductive path and buffers the volume expansion of active particles. Accordingly, SnO₂/Si@graphite delivers 798.9 mAh g^-1 at 200 mA g^-1 and maintains 550.8 mAh g^-1 after 1000 cycles at 1 A g^-1 in half cells. Impressively, a high energy density of 431.4 Wh kg^-1 (based on the mass of anode and cathode) can be obtained in full cells when paired with the NCM622 cathode. This work presents an effective strategy to exploit high-performance alloying-type anodes for LIBs by designing hybrid materials with multiple active components.

Electrochemical Performance Enhancement of Micro-Sized Porous Si by Integrating with Nano-Sn and Carbonaceous Materials

Silicon is investigated as one of the most prospective anode materials for next generation lithium ion batteries due to its superior theoretical capacity (3580 mAh g-1), but its commercial application is hindered by its inferior dynamic property and poor cyclic performance. Herein, we presented a facile method for preparing silicon/tin@graphite-amorphous carbon (Si/Sn@G-C) composite through hydrolyzing of SnCl2 on etched Fe-Si alloys, followed by ball milling mixture and carbon pyrolysis reduction processes. Structural characterization indicates that the nano-Sn decorated porous Si particles are coated by graphite and amorphous carbon. The addition of nano-Sn and carbonaceous materials can effectively improve the dynamic performance and the structure stability of the composite. As a result, it exhibits an initial columbic efficiency of 79% and a stable specific capacity of 825.5 mAh g-1 after 300 cycles at a current density of 1 A g-1. Besides, the Si/Sn@G-C composite exerts enhanced rate performance with 445 mAh g-1 retention at 5 A g-1. This work provides an approach to improve the electrochemical performance of Si anode materials through reasonable compositing with elements from the same family.

Rational Design of Pillared SnS/Ti3C2Tx MXene for Superior Lithium-Ion Storage

MXenes have been widely explored in energy storage because of their extraordinary properties; however, the majority of research on their application was staged at multilayered MXenes or assisted by carbon materials. Scientifically speaking, the two most distinctive properties of MXenes are usually neglected, composed of large interlayer spacing and abundant surface chemistry, which distinguish MXenes from other two-dimensional materials. Herein, few-layered MXene (f-MXene) nanosheet powders can be easily prepared according to the modified solution-phase flocculation method, completely avoiding the restacking phenomenon of f-MXene nanosheets in preparation and oxidation issues during the storage process. Via further employing the solvothermal reaction and annealing treatment, we successfully constructed pillared SnS/Ti₃C₂T_x composites decorated with in situ formed TiO₂ nanoparticles. In the composites, MXenes can play the role of a conductive network, a buffer matrix for volume expansion of SnS, while the active SnS nanoplates can fully deliver the advantage of high capacity and further induce interlayer engineering of Ti₃C₂T_x during cycling. As a result, the pillared SnS/Ti₃C₂T_x MXene composites exhibit obvious improvement in electrochemical performance. Interestingly, there is an apparent enhancement of capacity at succedent cycling, which can be ascribed to the "pillar effect" of Ti₃C₂T_x MXenes. The efforts and attempts made in this work can further broaden the development of pillared MXene composites.

Dual Immobilization of SnOx Nanoparticles by N-Doped Carbon and TiO2 for High-Performance Lithium-Ion Battery Anodes

The grain aggregation engendered kinetics failure is regarded as the main reason for the electrochemical decay of nanosized anode materials. Herein, we proposed a dual immobilization strategy to suppress the migration and aggregation of SnO_x nanoparticles and corresponding lithiation products through constructing SnO_x/TiO₂@PC composites. The N-doped carbon could anchor the tin oxide particles and inhibit their aggregation during the preparation process, leading to a uniform distribution of ultrafine SnO_x nanoparticles in the matrix. Meanwhile, the incorporated TiO₂ component works as parclose to suppress the migration and coarsening of SnO_x and corresponding lithiation products. In addition, the N-doped carbon and TiO₂/Li_xTiO₂ can significantly improve the electrical and ionic conductivities of the composites, enabling a good diffusion and charge-transfer dynamics. Owing to the dual immobilization from the "synergistic effect" of N-doped carbon and the "parclose effect" of TiO₂, the conversion reaction of SnO_x remains fully reversible throughout the cycling. Thereby, the composites exhibit excellent cycling performance in half cells and can be fully utilized in full cells. This work may provide an inspiration for the rational design of tin-based anodes for high-performance lithium-ion batteries.

Rational Design of an Electron/Ion Dual-Conductive Cathode Framework for High-Performance All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) have been paid increasing attention because of the better security compared with conventional lithium-ion batteries with flammable organic electrolytes. However, the poor ion transport between the cathode materials greatly hinders the capacity performance of ASSLBs. Herein, an electron/ion dual-conductive electrode framework is proposed for superior performance ASSLBs. Highly electronic conductive reduced graphene oxide and carbon nanotubes interconnect with active materials in the cathodes, constructing a three-dimensional continuous electron transport network. The composite electrolyte penetrates into the porous structure of the electrode, forming a consecutive ionic conductive framework. Furthermore, the thin electrolyte film formed on the surface of the cathode effectively lowers the interfacial resistance with the electrolyte membrane. Highly electron/ion conductive electrodes, combined with the polyethylene oxide-Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (PEO-LLZTO) composite electrolyte, show excellent capacity performance for both LiFePO₄ and sulfur (lithium-sulfur battery) active materials. In addition, the LiFePO₄ cathode demonstrates superior capacity performance and rate capability at room temperature. Furthermore, the relationship between the low Coulombic efficiency and Li dendrite growth has been revealed in this work. An effective layer is formed on the surface of Li metal by the simple modification of cupric fluoride (CuF₂), which can stabilize the electrolyte/anode interface. Finally, high-performance ASSLBs with high Coulombic efficiency can be achieved.

[Selection and effects of flap/myocutaneous flap repair methods for the defect after perineum tumor resection]

Objective: To explore the selection and effects of flap/myocutaneous flap repair methods for the defect after perineum tumor resection. Methods: From January 2011 to February 2017, 31 patients with vulvar tumor who were admitted to Hunan Cancer Hospital underwent repair of wound after tumor resection with various flaps/myocutaneous flaps. The patients were composed of 5 males and 26 females, aged 39-76 years, with 27 vulvar cancer and 4 Paget's disease in primary diseases. The size of defects after vulvar tumor radical resection ranged from 8.0 cm×4.5 cm to 27.5 cm×24.0 cm. According to the theory of perforasome, the defects were repaired by the external pudendal artery perforator flap, deep inferior epigastric artery perforator flap, rectus abdominis myocutaneous flap, anterolateral thigh flap, internal pudendal artery perforator flap, gracilis myocutaneous flap, and profunda artery perforator flap based on the specific size and location of perineum and groin where the defect was located. According to the blood supply zone of flap, totally 17 local translocation flaps, 18 axial flaps/myocutaneous flaps, and 7 V-Y advancement flaps were resected, with an area of 7.0 cm×4.0 cm to 21.0 cm×13.0 cm. All the flaps/myocutaneous flaps were transferred in pedicled fashion, and the donor sites were closed without tension. The number of flaps/myocutaneous flaps, wound closure, flaps/myocutaneous flaps survival, and follow-up were observed and recorded. Results: Altogether 42 flaps/myocutaneous flaps were harvested in 31 patients. Two flaps/myocutaneous flaps were used in 11 cases for large circular defect repair. All the defects achieved tension-free primary closure. The blood supply of 32 flaps/myocutaneous flaps was good, while insufficient blood supply was noted in the other 10 flaps/myocutaneous flaps. Seventeen flaps/myocutaneous flaps survived smoothly. Wound dehiscence occurred in 5 flaps/myocutaneous flaps 8 to 14 days postoperatively, which was healed with dressing change. Temporary congestion was noted in 7 flaps/myocutaneous flaps 2 to 5 days postoperatively, which recovered without special treatment. Three flaps/myocutaneous flaps had infection 7 to 15 days postoperatively, two of which recovered after dressing change, while the other one had partial necrosis and received debridement and direct closure. Two flaps/myocutaneous flaps were totally necrotic 8 to 15 days postoperatively, which were repaired with pedicled rectus abdominis myocutaneous flap after debridement. Seven flaps/myocutaneous flaps had partial necrosis 7 to 20 days postoperatively and were healed after dressing change. Twenty-four patients were followed up for 9-38 months. The color of flaps/myocutaneous flaps was similar to that of the surrounding skin, the shape of vulva was natural, the movement of hip joint was not limited, the function of micturition and defecation was not affected, and tumor recurrence was noted in 3 patients. Conclusions: For the complicated large defect after perineum tumor resection, the flexible application of different forms of flaps/myocutaneous flaps to repair according to different areas regains the appearance and function. However, there are many complications, so it is necessary to further strengthen the postoperative care.

Partial Atomic Tin Nanocomplex Pillared Few-Layered Ti3C2Tx MXenes for Superior Lithium-Ion Storage

MXenes have attracted great interest in various fields, and pillared MXenes open a new path with larger interlayer spacing. However, the further study of pillared MXenes is blocked at multilayered state due to serious restacking phenomenon of few-layered MXene nanosheets. In this work, for the first time, we designed a facile NH4+ method to fundamentally solve the restacking issues of MXene nanosheets and succeeded in achieving pillared few-layered MXene. Sn nanocomplex pillared few-layered Ti3C2Tx (STCT) composites were synthesized by introducing atomic Sn nanocomplex into interlayer of pillared few-layered Ti3C2Tx MXenes via pillaring technique. The MXene matrix can inhibit Sn nanocomplex particles agglomeration and serve as conductive network. Meanwhile, the Sn nanocomplex particles can further open the interlayer spacing of Ti3C2Tx during lithiation/delithiation processes and therefore generate extra capacity. Benefiting from the "pillar effect," the STCT composites can maintain 1016 mAh g-1 after 1200 cycles at 2000 mA g-1 and deliver a stable capacity of 680 mAh g-1 at 5 A g-1, showing one of the best performances among MXene-based composites. This work will provide a new way for the development of pillared MXenes and their energy storage due to significant breakthrough from multilayered state to few-layered one.

Fast and Universal Solution-Phase Flocculation Strategy for Scalable Synthesis of Various Few-Layered MXene Powders

MXenes have gained great attention in various fields because of their fascinating properties; however, the preparation of few-layered MXene powders is still limited by serious restacking of MXene nanosheets. Herein, for the first time, we have demonstrated an effective ammonium ion route to fundamentally address restacking and aggregation of the MXene nanosheets, using a solution-phase flocculation method (NH⁴⁺ method and modified NH⁴⁺ method) for large-scale preparation of few-layered Ti₃C₂T_x MXene powders in large quantities. The as-prepared few-layered MXene nanosheet powders show large size in the ab plane without the restacking phenomenon even at scanning electron microscopy measurements of 400× magnification, demonstrating the effectiveness of the proposed method. The method is also suitable for large-scale synthesis of other few-layered MXene powders, including Nb₄C₃T_x, V₂CT_x, Nb₂CT_x, etc., providing a general approach for the preparation of various few-layered MXene nanosheet powders, which represents a significant result for the development of MXenes.

Flowerlike Ti-Doped MoO3 Conductive Anode Fabricated by a Novel NiTi Dealloying Method: Greatly Enhanced Reversibility of the Conversion and Intercalation Reaction

Anodes made of molybdenum trioxide (MoO₃) suffer from insufficient conductivity and low catalytic reactivity. Here, we demonstrate that by using a dealloying method, we were able to fabricate anode of Ti-doped MoO₃ (Ti-MoO₃), which exhibits high catalytic reactivity, along with enhanced rate performance and cycling stability. We found that after doping, interestingly, the Ti-MoO₃ forms nanosheets and assembles into a micrometer-sized flowerlike morphology with enhanced interlayer distance. The density functional theory result has further concluded that the band gap of the Ti-doped anode has been reduced significantly, thus greatly enhancing the electronic conductivity. As a result, the structure maintains stability during the Li⁺ intercalation/deintercalation processes, which enhances the cycling stability and rate capability. This engineering strategy and one-step synthesis route opens up a new pathway in the design of anode materials.

Recent advances in MXenes and their composites in lithium/sodium batteries from the viewpoints of components and interlayer engineering

An up-to-date review about MXenes based on their distinguishing properties, namely, large interlayer spacing and rich surface chemistry.

Rational Design of Porous N-Ti3C2 MXene@CNT Microspheres for High Cycling Stability in Li-S Battery

Herein, N-Ti3C2@CNT microspheres are successfully synthesized by the simple spray drying method. In the preparation process, HCl-treated melamine (HTM) is selected as the sources of carbon and nitrogen. It not only realizes in situ growth of CNTs on the surface of MXene nanosheets with the catalysis of Ni, but also introduces efficient N-doping in both MXene and CNTs. Within the microsphere, MXene nanosheets interconnect with CNTs to form porous and conductive network. In addition, N-doped MXene and CNTs can provide strong chemical immobilization for polysulfides and effectively entrap them within the porous microspheres. Above-mentioned merits enable N-Ti3C2@CNT microspheres to be ideal sulfur host. When used in lithium-sulfur (Li-S) battery, the N-Ti3C2@CNT microspheres/S cathode delivers initial specific capacity of 927 mAh g-1 at 1 C and retains high capacity of 775 mAh g-1 after 1000 cycles with extremely low fading rate (FR) of 0.016% per cycle. Furthermore, the cathode still shows high cycling stability at high C-rate of 4 C (capacity of 647 mAh g-1 after 650 cycles, FR 0.027%) and high sulfur loading of 3 and 6 mg cm-2 for Li-S batteries.

Novel Synthesis of Red Phosphorus Nanodot/Ti3C2Tx MXenes from Low-Cost Ti3SiC2 MAX Phases for Superior Lithium- and Sodium-Ion Batteries

MXenes, synthesized from MAX, have emerged as new energy-storage materials for a good combination of metallic conductivity and rich surface chemistry. The reported MXenes are synthesized mostly from Al-based MAX. It is still a big challenge to synthesize MXenes from abundant Si-based MAX because of its strong Ti-Si bonds. Here, we report for the first time a high-energy ultrasonic cell-crushing extraction method to successfully prepare Ti₃C₂T_x MXenes from Si-based MAX using a single low-concentration etchant. This novel strategy for preparing MXenes has a high extraction efficiency and is a fast preparation process of less than 2 h for selective etching of Si. Furthermore, through the high-energy ball-milling technology, unique P-O-Ti bonded red phosphorus nanodot/Ti₃C₂T_x (PTCT) composites were successfully prepared, which enable superior electrochemical performance in lithium- and sodium-ion batteries because of the double-morphology structure, where the amorphous nano red phosphorus particles were strongly absorbed to Ti₃C₂T_x MXene sheets, facilitating the transport of alkali ions during cycling processes. This novel synthesis method of Ti₃C₂T_x MXenes from Si-based MAX and unique P-O-Ti bonded PTCT composites opens a new door for preparing high-performance MXene-based materials and facilitating the development of low-cost MXenes and other two-dimensional materials for next-generation energy storage.

Vapor Deposition Red Phosphorus to Prepare Nitrogen-Doped Ti3C2Tx MXenes Composites for Lithium-Ion Batteries

MXenes have great application prospect in energy storage fields due to a series of special physicochemical properties. However, the application of MXenes is greatly limited due to low intrinsic capacity. Here, through spray drying and vapor deposition methods, N-doped Ti₃C₂T_x and phosphorus composites (N-Ti₃C₂T_x/P) were prepared for the first time. The red phosphorus particles were absorbed to a walnut-like N-Ti₃C₂T_x matrix, facilitating the transport of Li⁺ and electrons. When used as anodes for lithium-ion batteries, the battery can cycle up to 1040 cycles with a high stable capacity of 801 mAh/g at 500 mA/g. Impressively, there is an obvious increase of capacity in the subsequent cycles at higher current density due to the increment of interlayer spacing of Ti₃C₂T_x nanosheets. XPS measurements confirm that the Ti-O-P bond was formed in the composites, granting the robust structure of the composites and leading to superior performances during cycling. The facile synthesis method of red phosphorus by vapor deposition will facilitate the development of other 2D materials combined with high-capacity red phosphorus for energy storage.

A New Intermetallic NiSn5 Phase: Induced Synthesis, Crystal Structure Resolution, and Investigation of Its Mechanism

Benefiting from the nanoscale effect, some metastable compounds can be synthesized in nanoparticles under normal conditions. The new intermetallic NiSn₅ phase is synthesized by us for the first time by using a seed crystal induction method. This tetragonal phase in the P4/ mcc space group has stoichiometric Ni atom defects, yielding Ni_0.62Sn₅. A study of the growth mechanism reveals that the FeSn₅/CoSn₅ seed crystal plays a vital role in the formation of the NiSn₅ phase. An investigation of the phase evolution during lithiation/delithiation processes indicates the irreversibility of NiSn₅ as an anode for lithium ion batteries.

New, Effective, and Low-Cost Dual-Functional Binder for Porous Silicon Anodes in Lithium-Ion Batteries

In this work, a new effective and low-cost binder applied in porous silicon anode is designed through blending of low-cost poly(acrylic acid) (PAA) and poly(ethylene- co-vinyl acetate) (EVA) latex (PAA/EVA) to avoid pulverization of electrodes and loss of electronic contact because of huge volume changes during repeated charge/discharge cycles. PAA with a large number of carboxyl groups offers strong binding strength among porous silicon particles. EVA with high elastic property enhances the ductility of the PAA/EVA binder. The high-ductility PAA/EVA binder tolerates the huge silicon volume variations and keeps the electrode integrity during the charge/discharge cycle process. EVA colloids acting as host materials for electrolytes increase the electrolyte uptake of electrodes. The porous silicon electrode with the PAA/EVA binder exhibits a reversible capacity of 2120 mA h g^-1 at 500 mA g^-1 after 140 cycles because of the excellent ductility and lithium-ion transport properties of the PAA/EVA binder.

Facile Synthesis of rGO/g-C3N4/CNT Microspheres via an Ethanol-Assisted Spray-Drying Method for High-Performance Lithium-Sulfur Batteries

rGO/g-C₃N₄ and rGO/g-C₃N₄/CNT microspheres are synthesized through the simple ethanol-assisted spray-drying method. The ethanol, as the additive, changes the structure of the rGO/g-C₃N₄ or rGO/g-C₃N₄/CNT composite from sheet clusters to regular microspheres. In the microspheres, the pores formed by reduced graphene oxide (rGO), g-C₃N₄, and carbon nanotube (CNT) stacking provide physical confinement for lithium polysulfides (LiPSs). In addition, enriched nitrogen (N) atoms of g-C₃N₄ offer strong chemical adhesion to anchor LiPSs. The dual immobilization mechanism can effectively alleviate the notorious "shuttle effect" of the lithium-sulfur battery. Meanwhile, the cathode with high cyclic stability can be achieved. The rGO/g-C₃N₄/CNT/S cathode delivers a discharge capacity of 620 mA h g^-1 after 500 cycles with a low capacity fading rate of only 0.03% per cycle at 1 C. Even, the cathode shows a retained capacity of 712 mA h g^-1 over 300 cycles with a high sulfur loading (4.2 mg cm^-2) at 0.2 C.

Ultra-stable binder-free rechargeable Li/I2 batteries enabled by "Betadine" chemical interaction

An activated carbon cloth/polymer-iodine (ACC/PVP-I2) composite was prepared by the "Betadine" method and employed as a high-performance cathode for rechargeable Li/I2 batteries. Due to the synergistic effect of ACC and PVP-I2, Li/I2 cells with ACC/PVP-I2 as the cathode exhibited superior electrochemical performance.

Polyiodide-Shuttle Restricting Polymer Cathode for Rechargeable Lithium/Iodine Battery with Ultralong Cycle Life

Rechargeable lithium/iodine (Li/I₂) batteries have attracted much attention because of their high gravimetric/volumetric energy densities, natural abundance and low cost. However, problems of the system, such as highly unstable iodine species under high temperature, their subsequent dissolution in electrolyte and continually reacting with lithium anode prevent the practical use of rechargeable Li/I₂ cells. A polymer-iodine composite (polyvinylpyrrolidone-iodine) with high thermostability is employed as cathode material in rechargeable Li/I₂ battery with an organic electrolyte. Because of the chemical interaction between polyvinylpyrrolidone (PVP) and polyiodide, most of the polyiodide in the cathode could be effectively trapped during charging/discharging. In-situ Raman observation revealed the evolution of iodine species in this system could be controlled during the process of I₅^- ↔ I₃^- ↔ I^-. Herein, the Li/I₂ battery delivered a high discharge capacity of 278 mAh g^-1 at 0.2 C and exhibited a very low capacity decay rate of 0.019% per cycle for prolonged 1100 charge/discharge cycles at 2 C. More importantly, a high areal capacity of 4.1 mAh cm^-2 was achieved for the electrode with high iodine loading of 21.2 mg cm^-2. This work may inspire new approach to design the Li/I₂ (or Li/polyiodide) system with long cycle life.

In Situ Observation of Single-Phase Lithium Intercalation in Sub-25-nm Nanoparticles

Many lithium-storage materials operate via first-order phase transformations with slow kinetics largely restricted by the nucleation and growth of a new phase. Due to the energy penalties associated with interfaces between coexisting phases, the tendency for a single-phase solid-solution pathway with exceptional reaction kinetics has been predicted to increase with decreasing particle size. Unfortunately, phase evolutions inside such small particles (tens of nanometers) are often shrouded by electrode-scale inhomogeneous reactions containing millions of particles, leading to intensive debate over the size-dependent microscopic reaction mechanisms. This study provides a generally applicable methodology capable of tracking lithiation pathways in individual nanoparticles and unambiguously reveals that lithiation of anatase TiO₂ , previously long believed to be biphasic, converts to a single-phase reaction when particle size reaches ≈25 nm. These results imply the prevalence of such a size-dependent transition in lithiation mechanism among intercalation compounds and provide important guidelines for designing high-power electrodes, especially cathodes.

Facial Synthesis of Three-Dimensional Cross-Linked Cage for High-Performance Lithium Storage

Silicon/C composite is a promising anode material for high-energy Li-ion batteries. However, synthesizing high-performance Si-based materials at large scale and low cost remains a huge challenge. Here, we for the first time report the preparation of an interconnected three-dimensional (3D) porous Si-hybrid architecture by using a spray drying method. In this unique structure, the highly robust C-CNT-RGO cages not only can improve the conductivity of the electrode and buffer the volume expansion but also suppress the Si nanoparticles aggregation. As a result, the 3D Si@po-C/CNT/RGO electrode achieves long-life cycling stability at high rates (a reversible capacity of 854.9 mA h g(-1) at 2 A g(-1) after 500 cycles and capacity decay less than 0.013% per cycle) and good rate capability (1454.7, 1198.8, 949.2, 597.8, and 150 mA h g(-1) at current densities of 1, 2, 4, 10, and 20 A g(-1), respectively). Moreover, this novel electrode could deliver high reversible capacities and long-life stabilities even with high mass loading density (764.9 mA h g(-1) at 1.0 mg cm(-2) after 500 cycles and 472.2 mA h g(-1) at 1.5 mg cm(-2) after 400 cycles, respectively). This cheap and scalable strategy can be extended to fabricate other materials with large volume expansion (Sn, Ge, transition-metal oxides) and 3D porous carbon for other potential applications.

A composite with SiOx nanoparticles confined in carbon framework as an anode material for lithium ion battery

A composite with ultrafine SiO_x (x = 1.57, around 2 nm) nanoparticles confined in a carbon framework is synthesized by a simple thermopolymerization process and subsequent heat treatment.

Hollow silica-copper-carbon anodes using copper metal-organic frameworks as skeletons

Hollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO(2) and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and cushion the volume change. In consequence, the resulting material as an anode for lithium-ion batteries (LIBs) delivers a reversible capacity of 495 mA h g(-1) after 400 cycles at a current density of 500 mA g(-1). The synthetic method presented in this paper provides a facile and low-cost strategy for the large-scale production of hollow silica/copper/carbon nanocomposites as an anode in LIBs.

Average and Local Crystal Structures of (Ga(1-x)Znx)(N(1-x)Ox) Solid Solution Nanoparticles

We report a comprehensive study of the crystal structure of (Ga(1-x)Znx)(N(1-x)Ox) solid solution nanoparticles by means of neutron and synchrotron X-ray scattering. In our study, we used four different types of (Ga(1-x)Znx)(N(1-x)Ox) nanoparticles, with diameters of 10-27 nm and x = 0.075-0.51, which show energy band gaps from 2.21 to 2.61 eV. Rietveld analysis of the neutron diffraction data revealed that the average crystal structure is hexagonal wurtzite (space group P63mc) for the larger nanoparticles, while the crystal structure of smaller nanoparticles is disordered hexagonal. Pair-distribution-function analysis found that the intermediate crystal structure retains a "motif" of the average one; however, the local structure is more disordered. The implications of disorder on the reduced energy band gap are discussed.

Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium-Sulfur Battery

A porous interconnected 3D boron-doped graphene aerogel (BGA) was prepared via a one-pot hydrothermal treatment. The BGA material was first loaded with sulfur to serve as cathode in lithium-sulfur batteries. Boron was positively polarized on the graphene framework, allowing for chemical adsorption of negative polysufide species. Compared with nitrogen-doped and undoped graphene aerogel, the BGA-S cathode could deliver a higher capacity of 994 mA h g(-1) at 0.2 C after 100 cycles, as well as an outstanding rate capability, which indicated the BGA was an ideal cathode material for lithium-sulfur batteries.

In Situ AFM Imaging of Solid Electrolyte Interfaces on HOPG with Ethylene Carbonate and Fluoroethylene Carbonate-Based Electrolytes

Chemical and morphological structure of solid electrolyte interphase (SEI) plays a vital role in lithium-ion battery (LIB), especially for its cyclability and safety. To date, research on SEI is quite limited because of the complexity of SEI and lack of effective in situ characterization techniques. Here, we present real-time views of SEI morphological evolution using electrochemical atomic force microscopy (EC-AFM). Complemented by an ex situ XPS analysis, fundamental differences of SEI formation from ethylene carbonate (EC) and fluoroethylene carbonate (FEC)-based electrolytes during first lithiation/delithiation cycle on HOPG electrode surface were revealed.

Enhanced Electrochemical Performance of Fe0.74Sn5@Reduced Graphene Oxide Nanocomposite Anodes for Both Li-Ion and Na-Ion Batteries

The recently found intermetallic FeSn5 phase with defect structure Fe0.74Sn5 has shown promise as a high capacity anode for lithium-ion batteries (LIBs). The theoretical capacity is as high as 929 mAh g(-1) thanks to the high Sn/Fe ratio. However, despite being an alloy, the cycle life remains a great challenge. Here, by combining Fe0.74Sn5 nanospheres with reduced graphene oxide (RGO) nanosheets, the Fe0.74Sn5@RGO nanocomposite can achieve capacity retention 3 times that of the nanospheres alone, after 100 charge/discharge cycles. Moreover, the nanocomposite also displays its versatility as a high-capacity anode in sodium-ion batteries (SIBs). The enhanced cell performance in both battery systems indicates that the Fe0.74Sn5@RGO nanocomposite can be a potential anode candidate for the application of Li-ion and Na-ion battery.

A scalable formation of nano-SnO2 anode derived from tin metal–organic frameworks for lithium-ion battery

In this work, for the first time, we synthesize a SnO₂ nanomaterial through the calcination of tin metal–organic framework (MOF) precursors.

Structure and luminescence properties of 10-BN sheets

Isotopic (10)BN sheets were first prepared using graphene sheets as templates to react with (10)B(2)O(3). The edge-areas of BN sheets have much higher oxygen-doping ratios compared to other areas. The emission peak of X-ray excited optical luminescence spectra of the (10)BN-sheets is broader and red-shifted because of the isotopic effect. A broad violet-blue emission at a wavelength centered at ∼400 nm is assigned to the defect emission due to oxygen-doping and defects in the BN network.

CoSn5 Phase: Crystal Structure Resolving and Stable High Capacity as Anodes for Li Ion Batteries

Tin alloys form a class of interesting high-energy-density anode materials for Li ion batteries, but the improvement of their cycling stability is elusive. Here, we provide new insight on this fatal issue by synthesizing novel CoSn5-phase nanospheres via a conversion chemistry route and directly comparing their cell behavior with that of recently found FeSn5-phase nanospheres. The CoSn5 phase is absent in previous Co-Sn phase diagrams. Co0.83Sn5 nanospheres show a much longer cycle life, which partially is related to milder evolution of their cycling profiles over time.

Amorphous hierarchical porous GeO(x) as high-capacity anodes for Li ion batteries with very long cycling life

Many researchers have focused in recent years on resolving the crucial problem of capacity fading in Li ion batteries when carbon anodes are replaced by other group-IV elements (Si, Ge, Sn) with much higher capacities. Some progress was achieved by using different nanostructures (mainly carbon coatings), with which the cycle numbers reached 100-200. However, obtaining longer stability via a simple process remains challenging. Here we demonstrate that a nanostructure of amorphous hierarchical porous GeO(x) whose primary particles are ~3.7 nm diameter has a very stable capacity of ~1250 mA h g(-1) for 600 cycles. Furthermore, we show that a full cell coupled with a Li(NiCoMn)(1/3)O(2) cathode exhibits high performance.

Graphene enhances Li storage capacity of porous single-crystalline silicon nanowires

We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO3 etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g(-1) that is much higher than the 1256 mAh g(-1) of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphene with the porous Si 1D nanostructure.

Single-crystal intermetallic M-Sn (M = Fe, Cu, Co, Ni) nanospheres as negative electrodes for lithium-ion batteries

FeSn(2), Cu(6)Sn(5), CoSn(3), and Ni(3)Sn(4) single-crystalline nanospheres with a characteristic uniform particle size of approximately 40 nm have been synthesized via a modified polyol process, aiming at determining and understanding their intrinsic cycling performance as negative electrode materials for lithium-ion batteries. We find that, in this morphologically controlled condition, the reversible capacities follow FeSn(2) > Cu(6)Sn(5) approximately CoSn(3) > Ni(3)Sn(4), which is not directly decided by their theoretical capacities or lithium-driven volume changes. FeSn(2) exhibits the best electrochemical activity among these intermetallic nanospheres and an effective solid electrolyte interface, which explains its superior cycling performance. The small particle dimension also improves cycling stability and Li(+) diffusion.

Tri- and quadri-metallic ultrathin nanowires synthesized by one-step phase-transfer approach

We synthesized, at room temperature, noble multi-metallic (Pt-Pd-Rh, and Pt-Pd-Au-Rh) ultrathin nanowires using a one-step phase-transfer approach. These multi-metallic nanowires then were characterized by x-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy. The diameters of the nanowires range from 2 to 2.7 nm, and their lengths from tens to hundreds of nanometers. The multi-metallic nanowires were determined to be face-centered cubic structures. The compositions of the nanowires are quite uniform from wire to wire. Our results verify that the phase-transfer is a robust method for synthesizing various multi-metallic nanowires, which are expected to have potential applications in catalysis, magnetic storage, and bio-sensors.

Isotope effect on band gap and radiative transitions properties of boron nitride nanotubes

We have carried out an isotope study on the band gap and radiative transition spectra of boron nitride nanotubes (BNNTs) using both experimental and theoretical approaches. The direct band gap of BNNTs was determined at 5.38 eV, independent of the nanotube size and isotope substitution, by cathodoluminescences (CL) spectra. At lower energies, several radiative transitions were observed, and an isotope effect was revealed. In particular, we confirmed that the rich CL spectra between 3.0 and 4.2 eV reflect a phonon-electron coupling mechanism, which is characterized by a radiative transition at 4.09 eV. The frequency red shift and peak broadening due to isotopic effect have been observed. Our Fourier transform infrared spectra and density functional theory calculations suggest that those radiative transitions in BNNTs could be generated by a replacement of some nitrogen atoms with oxygen.