Synergistic effect between S and Te enhancing the electrochemical behavior of heteroatomic TeS-x cathodes in aqueous Zn-TeS batteries.

Aqueous Zn-S batteries (AZSBs) have garnered increasing attention in the energy storage field owing to their high capacity, energy density, and cost effectiveness. Nevertheless, sulfur (S) cathodes face challenges, primarily stemming from sluggish reaction kinetics and the formation of an irreversible byproduct (SO42-) during the charge, hindering the progress of AZSBs. Herein, Te-S bonds within S-based cathodes were introduced to enhance electron and ion transport and facilitate the conversion reaction from zinc sulfide (ZnS) to S. This was achieved by constructing heteroatomic TeS-x@Ketjen black composite cathodes (HM-TeS-x@KB, where x  = 36, 9, and 4). The HM-TeS-9@KB electrode exhibits long-term cycling stability, maintaining a capacity decay rate of 0.1 % per cycle over 450 cycles at a current density of 10 A g-1. Crucially, through a combination of experimental data analysis and theoretical calculations, the impact mechanism of Te on the charge and discharge of S active materials within the HM-TeS-9@KB cathode in AZSBs was investigated. The presence of Te-S bonds boost the intrinsic conductivity and wettability of the HM-TeS-9@KB cathode. Furthermore, during the charge, the interaction of preferentially oxidized Te with S atoms within ZnS promotes the oxidation reaction from ZnS to S and suppresses the irreversible side reaction between ZnS and H2O. These findings indicate that the heteroatomization of chalcogen S molecules represents a promising approach for enhancing the electrochemical performance of S cathodes in AZSBs.

Processable Potassium-Carbon Nanotube Film with a Three-Dimensional Structure for Ultrastable Metallic Potassium Anodes.

K metal holds great promise as the ultimate anode candidate for K-ion batteries because of its high theoretical capacity and low operating potential. However, due to its high viscosity and poor mechanical processability, it remains challenging to manufacture potassium anodes with precise parameters by a simple and executable method. In this work, a high-performance potassium-carbon nanotubes (K@CNTs) composite film electrode with a three-dimensional (3D) skeleton and superior processability is prepared by simply incorporating CNTs into molten potassium. The in situ potassiation reaction between CNTs and molten K formed potassium carbide (KC8) so as to obtain a solid-liquid mixture, which can reduce the surface tension of molten potassium and promote the preparation of the K@CNTs film electrode. The composite electrode can be molded into a variety of shapes and thicknesses in accurate dimensions. The porous, well-conducting CNTs act as a 3D skeleton uniformly distributed in the K metal, providing adequate surface and space to accommodate and attract K metal, thereby inhibiting the growth of the potassium dendrites and the volume expansion upon cycling. As a result, the K@CNTs composite anode exhibits excellent cyclability and rate capability in both symmetric and full cells. The superior processability and excellent electrochemical performance make this composite an ideal anode candidate for commercial applications in potassium metal batteries.

Long Shelf-Life Efficient Electrolytes Based on Trace l-Cysteine Additives toward Stable Zinc Metal Anodes.

The unstable anode/electrolyte interface (AEI) triggers the corrosion reaction and dendrite formation during cycling, hindering the practical application of zinc metal batteries. Herein, for the first time, l-cysteine (Cys) is employed to serve as an electrolyte additive for stabilizing the Zn/electrolyte interface. It is revealed that Cys additives tend to initially approach the Zn surface and then decompose into multiple effective components for suppressing parasitic reactions and Zn dendrites. As a consequence, Zn|Zn symmetric cells using trace Cys additives (0.83 mm) exhibit a steady cycle life of 1600 h, outperforming that of prior studies. Additionally, an average Coulombic efficiency of 99.6% for 250 cycles is also obtained under critical test conditions (10 mA cm-2 /5 mAh cm-2 ). Cys additives also enable Zn-V2 O5 and Zn-MnO2 full cells with an enhanced cycle stability at a low N/P ratio. More importantly, Cys/ZnSO4 electrolytes are demonstrated to be still effective after resting for half year, favoring the practical production.

Stabilizing Zinc Anodes by Regulating the Electrical Double Layer with Saccharin Anions.

Zn anodes suffer from poor Coulombic efficiency (CE) and serious dendrite formation due to the unstable anode/electrolyte interface (AEI). The electrical double layer (EDL) structure formed before cycling is of great significance for building stable solid electrolyte interphase (SEI) on Zn surface but barely discussed in previous research about the stabilization of Zn anode. Herein, saccharin (Sac) is introduced as electrolyte additive for regulating the EDL structure on the AEI. It is found that Sac derived anions are preferentially adsorbed on the Zn metal surface instead of water dipole, creating a new H2 O-poor EDL structure. Moreover, the unique SEI is also detected on the Zn surface due to the decomposition of Sac anions. Both are proved to be capable of modulating Zn deposition behavior and preventing side reactions. Encouragingly, Zn|Zn symmetric cells using Sac additive deliver a high cumulative plated capacity of 2.75 Ah cm-2 and a high average CE of 99.6% under harsh test condition (10 mA cm-2 , 10 mAh cm-2 ). The excellent stability is also achieved at a high rate of 40 mA cm-2 . The effectiveness of this Sac additive is further demonstrated in the Zn-MnO2 full cells.

Metallic-State MoS2 Nanosheets with Atomic Modification for Sodium Ion Batteries with a High Rate Capability and Long Lifespan.

Exploring active materials with a high rate capability and long lifespan for sodium ion batteries attracts much more attention and plays an important role in realizing clean energy storage and conversion. The strategy of optimizing the electronic structure by atomic element substitution within MoS2 layers was employed to change the inherent physical property. The enhanced electronic conductivity from a decreased bandgap and increased surface Na+ adsorption energy can efficiently and dramatically optimize the electrochemical performance for sodium storage. Attempting to limit the large volume variation and avoid MoS2 nanosheet stacking and restacking, numerous nanosheets are in situ grown into a designed hierarchical mesopore carbon matrix. This structure can tightly capture the nanosheets to prevent them from aggregating and offer a sufficient buffer zone for alleviating severe volume changes during the discharging/charging process, contributing remarkably to the structural integrity and superior rate performance of electrodes.

Enhanced Potassium-Ion Storage of the 3D Carbon Superstructure by Manipulating the Nitrogen-Doped Species and Morphology.

Potassium-ion batteries (PIBs) are attractive for grid-scale energy storage due to the abundant potassium resource and high energy density. The key to achieving high-performance and large-scale energy storage technology lies in seeking eco-efficient synthetic processes to the design of suitable anode materials. Herein, a spherical sponge-like carbon superstructure (NCS) assembled by 2D nanosheets is rationally and efficiently designed for K+ storage. The optimized NCS electrode exhibits an outstanding rate capability, high reversible specific capacity (250 mAh g-1 at 200 mA g-1 after 300 cycles), and promising cycling performance (205 mAh g-1 at 1000 mA g-1 after 2000 cycles). The superior performance can be attributed to the unique robust spherical structure and 3D electrical transfer network together with nitrogen-rich nanosheets. Moreover, the regulation of the nitrogen doping types and morphology of NCS-5 is also discussed in detail based on the experiments results and density functional theory calculations. This strategy for manipulating the structure and properties of 3D materials is expected to meet the grand challenges for advanced carbon materials as high-performance PIB anodes in practical applications.

Enhanced performance of lithium-sulfur batteries based on single-sided chemical tailoring, and organosiloxane grafted PP separator.

Even after a decade of research and rapid development of lithium-sulfur (Li-S) batteries, the infamous shuttle effect of lithium polysulfide is still the major challenge hindering the commercialization of Li-S batteries. In order to further address this issue, a functionalized PP separator is obtained through selective single-sided chemical tailoring, and then organosiloxane fumigation grafting. During the charge-discharge process, the grafted functional groups can effectively block the transportation of the dissolved polysulfides through strong chemical anchoring, inhibit the shuttle effect and greatly enhance the cycle stability of the Li-S battery. Interestingly, the specially designed single-sided enlarged channel structure formed by chemical tailoring can well accommodate the deposition with intermediate polysulfides on the separator surface toward the cathode chamber, resulting in enhanced initial discharge capacity and rate performance. Compared to the battery assembled with PP, the Li-S battery employing the separator grafted with a 3-ureidopropyltrimethoxysilane (PP-O x--U) displays better electrochemical performance. Even at 2C, it can still deliver a high capacity of 786 mA h g-1, and retain a capacity of 410 mA h g-1 with a low capacity fading of 0.095% per cycle over 500 cycles. This work provides a very promising and feasible strategy for the development of a special functionalization PP separator for Li-S batteries with high electrochemical performance.

Room temperature ultrafast synthesis of N- and O-rich graphene films with an expanded interlayer distance for high volumetric capacitance supercapacitors.

An electrochemical functionalization method is developed to fabricate N- and O-rich graphene films (F-RGO-60) with an expanded interlayer distance. In particular, the functionalization process could be completed within 60 seconds at room temperature, which is conducive to large-scale commercial applications. Electrochemical synthesis of F-RGO-60 leads to two synergetic effects simultaneously: (1) the expansion of the interlayer distance caused by a bubble effect, which leads to more exposure of the active surface area and (2) the introduction of N-doped sites and oxygen-containing functional groups, which not only improves the hydrophilicity of F-RGO-60 but also provides extra pseudocapacitance. It is worth mentioning that after electrochemical functionalization, F-RGO-60 can still maintain a high density of 1.47 g cm-3. Due to their optimal surface area, good electrolyte wettability and massive redox-active sites, the specific capacitance of F-RGO-60 films can reach up to 319.4 F cm-3 (217.3 F g-1) at 1 A g-1 in a three-electrode system, which is about 3.6 times larger than that of RGO films (60 F g-1). The integration of the low-cost preparation method and outstanding performance suggests that F-RGO-60 has great development prospects as supercapacitor electrode materials.

Metallic-State SnS2 Nanosheets with Expanded Lattice Spacing for High-Performance Sodium-Ion Batteries.

Metallic-state 2D SnS2 nanosheets with expanded lattice spacing and a defect-rich structure were synthesized by the intercalation of Ni into the van der Waals gap of SnS2 . The expanded lattice spacing efficiently enhanced the electrochemical performance of the SnS2 for sodium-ion batteries owing to the change electron state density and energy band structure. In operando synchrotron XRD and theoretical calculations were used to gain insight into the influence of foreign metal-ion doping and its location. The optimized architecture obtained by in situ uniform growth of nanosheets on carbon fibers significantly enhanced the electrochemical performance. The inherent advantages of this architecture are shorter paths for ion insertion and extraction, larger contact area for more sodium diffusion pathways, and superior electrolyte penetration. Benefiting from the Ni intercalated SnS2 bilayer, the internal adjustment of the electronic state and the enlarged interlayer spacing significantly enhanced the electron transport kinetics, which can be explained by the metallic-state properties. The integrated electrode exhibited an initial high reversible capacity of 795 mAh g-1 at 0.1 A g-1 , with a stable capacity retention of 666 mAh g-1 after 100 cycles. Good rate capability was also exhibited with specific capacities of 691, 564, 437 mAh g-1 at current densities of 200, 500, and 1000 mA g-1 , respectively.

Compact-Nanobox Engineering of Transition Metal Oxides with Enhanced Initial Coulombic Efficiency for Lithium-Ion Battery Anodes.

A novel strategy is proposed to construct a compact-nanobox (CNB) structure composed of irregular nanograins (average diameter ≈ 10 nm), aiming to confine the electrode-electrolyte contact area and enhance initial Coulombic efficiency (ICE) of transition metal oxide (TMO) anodes. To demonstrate the validity of this attempt, CoO-CNB is taken as an example which is synthesized via a carbothermic reduction method. Benefiting from the compact configuration, electrolyte can only contact the outer surface of the nanobox, keeping the inner CoO nanograins untouched. Therefore, the solid electrolyte interphase (SEI) formation is reduced. Furthermore, the internal cavity leaves enough room for volume variation upon lithiation and delithiation, resulting in superior mechanical stability of the CNB structure and less generation of fresh SEI. Consequently, the SEI remains stable and spatially confined without degradation, and hence, the CoO-CNB electrode delivers an enhanced ICE of 82.2%, which is among the highest values reported for TMO-based anodes in lithium-ion batteries. In addition, the CoO-CNB electrode also demonstrates excellent cyclability with a reversible capacity of 811.6 mA h g-1 (90.4% capacity retention after 100 cycles). These findings open up a new way to design high-ICE electrodes and boost the practical application of TMO anodes.

LifePo4 Coated Homogeneously with 3D Carbon Nanotube Conductive Networks for Enhanced Electrochemical Performance.

LiFePO4 (LFP) microparticles coated homogeneously with three-dimensional (3D) carbon nanotube (CNT) conductive networks were successfully prepared via a simple and effective ball milling method by controlling Polyvinylidene fluoride (PVDF) content in cathode electrode slurry. Scanning electron microscopy (SEM) demonstrated that the electrical bridge between the LFP could be well modulated by varying the amount of the CNTs and PVDF. The LFP/CNTs composite with 3 wt% CNTs and 5 wt% PVDF, in which CNTs are embedded in the microspheres homogeneously, possesses the best 3D CNT conductive networks and exhibits the best electrochemical property with high capacity retention of 95.72% at 0.25 C after 50 cycles. Essentially, in comparison with those samples without CNT networks, this CNT network structure can greatly enhance the electrical conductivity, thus markedly improving the electrochemical performance. (LFP) microparticles coated homogeneously with three-dimensional (3D) carbon nanotube (CNT) conductive networks were successfully prepared via a simple and effective ball milling method by controlling Polyvinylidene fluoride (PVDF) content in cathode electrode slurry. Scanning electron microscopy (SEM) demonstrated that the electrical bridge between the LFP could be well modulated by varying the amount of the CNTs and PVDF. The LFP/CNTs composite with 3 wt% CNTs and 5 wt% PVDF, in which CNTs are embedded in the microspheres homogeneously, possesses the best 3D CNT conductive networks and exhibits the best electrochemical property with high capacity retention of 95.72% at 0.25 C after 50 cycles. Essentially, in comparison with those samples without CNT networks, this CNT network structure can greatly enhance the electrical conductivity, thus markedly improving the electrochemical performance.

Dual-Confined Sulfur Nanoparticles Encapsulated in Hollow TiO2 Spheres Wrapped with Graphene for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are attractive owing to their higher energy density and lower cost compared with the universally used lithium-ion batteries (LIBs), but there are some problems that stop their practical use, such as low utilization and rapid capacity-fading of the sulfur cathode, which is mainly caused by the shuttle effect, and the uncontrollable deposition of lithium sulfide species. Herein, we report the design and fabrication of dual-confined sulfur nanoparticles that were encapsulated inside hollow TiO2 spheres; the encapsulated nanoparticles were prepared by a facile hydrolysis process combined with acid etching, followed by "wrapping" with graphene (G-TiO2 @S). In this unique composite architecture, the hollow TiO2 spheres acted as effective sulfur carriers by confining the polysulfides and buffering volume changes during the charge-discharge processes by means of physical force from the hollow spheres and chemical binding between TiO2 and the polysulfides. Moreover, the graphene-wrapped skin provided an effective 3D conductive network to improve the electronic conductivity of the sulfur cathode and, at the same time, to further suppress the dissolution of the polysulfides. As results, the G-TiO2 @S hybrids exhibited a high and stable discharge capacity of up to 853.4 mA h g-1 over 200 cycles at 0.5 C (1 C=1675 mA g-1 ) and an excellent rate capability of 675 mA h g-1 at a current rate of 2 C; thus, G-TiO2 @S holds great promise as a cathode material for Li-S batteries.

Alignment and structural control of nitrogen-doped carbon nanotubes by utilizing precursor concentration effect.

Nitrogen-doped carbon nanotubes (NCNTs) were prepared using a simple ultrasonic spray pyrolysis method. The precursor concentration effect was examined to effectively control alignment, open tip and diameter of the NCNTs by changing xylene/cyclohexylamine ratio. The structure and morphology of the resultant NCNTs were characterized by scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. The degree of alignment and the diameter of the NCNTs increased as the xylene/cyclohexylamine precursor mixture was changed from 0 to 35% cyclohexylamine. This precursor composition also caused a large number of open-ended nanotubes to form with graphite layers inside the cavities of the NCNTs. However, further increase cyclohexylamine content in the precursor reduced the degree of alignment and diameter of the NCNTs. We demonstrate control over the NCNT alignment and diameter, along with the formation of open-ended nanotube tips, and propose a growth mechanism to understand how these properties are interlinked.

Studies on a new carrier of trimethylsilyl-modified mesoporous material for controlled drug delivery.

To better control drug delivery rate, a simple and effective approach has been developed for controlled drug delivery carrier system through one-step surface modification of the ibuprofen-impregnated silica MCM-41 with 1, 1, 1, 3, 3, 3-hexamethyldisilazane (HMDS). The 29Si MAS NMR characterization demonstrated that different contents of trimethylsilyl (TMS) groups were successfully grafted onto the samples modified with different silylation times. The results obtained from in vitro tests exhibited that the introduction of TMS groups greatly retarded the ibuprofen release rate. Even after in vitro test for 48 h, only 75% of the impregnated ibuprofen could be released from the modified sample with TMS groups content of 14.5% (related to the total silicon atoms). However, the release of ibuprofen could be completed just after about 1 h from the pure silica MCM-41 under the same release conditions. Furthermore, the release rate of ibuprofen could be well modulated by changing the grafted content of TMS groups, and was found to decrease with increasing grafted amount of TMS groups.