Trumpet-Like ZnS@C Composite for High-Performance Potassium Ion Battery Anode.

ZnS has acquired increasing attention for high-performance PIBs anode because of its remarkable theoretical capacity, and redox reversibility for conversion reaction. However, the larger volume variation and delayed reaction kinetics for the ZnS in the discharge/charge processes lead to pulverization and severe capacity degradation. Herein, the trumpet-like ZnS@C composite was synthesized by template method by using sodium citrate as carbon source followed by vulcanization process. As potassium ion batteries (PIB) anode, ZnS@C composite exhibits good rate performance and long life (stable reversible capacity of 107.8 mAh/g over 2000 charge-discharge cycles at 5 A/g and high reversible capacity of 310 mAh/g at 0.1 A/g). The outstanding electrochemical performance of the ZnS@C composite is ascribed to its unique structure, which can mitigate the volume expansion of ZnS in the charge discharge process, expand the contact area between the electrode and electrolyte, and improve the conductivity of electrode materials by the introduction of carbon layer. This method of synthesizing trumpet-like ZnS@C composite provides an important strategy for obtaining potassium ion batteries anode with long cycle.

Ultra-thick electrodes based on activated wood-carbon towards high-performance quasi-solid-state supercapacitors.

Wood carbon (WC)-derived thick electrode design has recently received increasing interest because of its high energy density at the device level. Herein, a facile, low-cost, and efficient strategy by surface engineering to synthesize ultrathick electrodes of quasi-solid-state symmetric supercapacitors (SSCs) based on activated wood-carbon (AWC) monoliths is presented. The AWC as a freestanding ultrathick electrode shows an impressive areal capacitance of 6.85 F cm-2 at 1 mA cm-2 and 4.55 F cm-2 at 20 mA cm-2. Furthermore, a quasi-solid-state SSC assembled by two identical AWC monoliths delivers an excellent energy density of 0.23 mW h cm-2 (4.59 W h kg-1 and 0.77 W h L-1) at 500 mW cm-2 (9.9 mW kg-1 and 2500 W L-1) while maintaining a capacitance retention of 86% after 10 000 cycles. The remarkable electrochemical performance is associated with the structural integrity of natural wood, the introduction of oxygen-containing functional groups, and the ultrathick electrode design, which significantly enhance electroactive material loading and device integration.

Heterostructured Co/CeO2-Decorating N-Doped Porous Carbon Nanocubes as Efficient Sulfur Hosts with Enhanced Rate Capability and Cycling Durability toward Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have gained significant interest thanks to their satisfactory energy density and abundant earth resources. Nevertheless, practical implementations of RT Na-S batteries are still impeded by serious shuttle effects of sodium polysulfide (NaPS) intermediates, sluggish redox kinetics of cathodes, and poor electronic conductivity from S-species. To solve these problems, heterostructured Co/CeO2-decorating N-doped porous carbon nanocubes (Co/CeO2-NPC) are constructed as a S support, which integrates the strong adsorption and fast conversion of NaPSs, together with superior electronic conductivity. Consequently, the as-synthesized S@Co/CeO2-NPC cathode for RT Na-S batteries exhibits improved rate performance (1275, 561.1, and 485 mAh g-1 at 0.1, 5, and 10 C, respectively) and superior cyclic durability (capacity degeneration of 0.027% per cycle after 1000 cycles at 5 C). Such a S cathode combining a heterostructure interface, hierarchical porous carbon nanocubes, and polar compositions can considerably increase electronic conductivity and promote NaPS adsorption and conversion, achieving superior performance toward RT Na-S batteries.

Construction of Porous Carbon Nanosheet/Cu2S Composites with Enhanced Potassium Storage.

Porous C nanosheet/Cu2S composites were prepared using a simple self-template method and vulcanization process. The Cu2S nanoparticles with an average diameter of 140 nm are uniformly distributed on porous carbon nanosheets. When used as the anode of a potassium-ion battery, porous C nanosheet/Cu2S composites exhibit good rate performance and cycle performance (363 mAh g-1 at 0.1 A g-1 after 100 cycles; 120 mAh g-1 at 5 A g-1 after 1000 cycles). The excellent electrochemical performance of porous C nanosheet/Cu2S composites can be ascribed to their unique structure, which can restrain the volume change of Cu2S during the charge/discharge processes, increase the contact area between the electrode and the electrolyte, and improve the electron/ionic conductivity of the electrode material.

Metal-Organic Frameworks-Derived Nitrogen-Doped Porous Carbon Nanocubes with Embedded Co Nanoparticles as Efficient Sulfur Immobilizers for Room Temperature Sodium-Sulfur Batteries.

Room temperature sodium-sulfur (RT Na-S) batteries are considered a promising candidate for energy-storage due to their high energy-density and low-cost. However, the shutting effect of polysulfides and sluggish kinetics of sulfur redox reactions still severely limit their practical implementation. Herein, a new type of 3D hierarchical porous carbonaceous nanocubes is reported as efficient sulfur hosts, composed of carbon nanotubes (CNT) and Co nanoparticles (NPs) uniformly embedded into a nitrogen-doped carbon matrix (NC). Because of the high specific surface area, large degree of graphitization, and the synergetic effects between Co NPs and N-doping, the as-designed CNTs/Co@NC electrodes not only significantly increase polysulfides immobilization, but also efficiently catalyze sulfur redox reactions, as confirmed by experimental results and DFT calculations. When tested in a RT Na-S battery, the S@CNTs/Co@NC-0.25 cathode demonstrates outstanding electrochemical performance, achieving high initial specific capacity of 1200.3 mAh g-1 at 0.1 C, remarkable rate capability up to 5.0 C (474.2 mAh g-1 ), and superior cyclic performance of 450.5 mAh g-1 (292 mAh g-1 ) after 400 cycles at 1.0 C (5.0 C). The integration of a 3D hierarchical porous architecture with well-dispersed Co NPs of an electro-catalyst provides valuable insights based on structure-adsorption-catalysis engineering for advanced RT Na-S batteries.

Single Cobalt Atoms Decorated N-doped Carbon Polyhedron Enabled Dendrite-Free Sodium Metal Anode.

Uncontrollable growth of sodium dendrites during the sodium deposition and stripping processes remains a huge challenge for achieving high-performance sodium metal batteries (SMBs), which results in ineffective utilization of metallic Na, low Coulombic efficiency, and inferior cycling life. Here, a single Co atom uniformly decorated porous nitrogen-doped carbon polyhedron (CoSA @NC) matrix has been fabricated and introduced to control the Na growth and achieve uniform Na nucleation/deposition. Cryo-electron microscopy and in situ optical microscopy techniques have been utilized to analyze the morphology change of metallic Na during plating/stripping processes. The single Co atoms evenly embedded in NC electrodes can provide stable Na-philic sites for Na ions adsorption, which is helpful to guide the uniform sodium deposition and prevent Na dendrites growth. This work thus provides an effective solution to inhibit Na dendrite growth and control Na nucleation behavior from the perspective of atomic level, towards the fabrication of high-safety and long-cycling SMBs.

Excellent rate capability and cycling stability in Li+-conductive Li2SnO3-coated LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries.

High-voltage LiNi0.5Mn1.5O4 is a promising cathode candidate for lithium-ion batteries (LIBs) due to its considerable energy density and power density, but the material generally undergoes serious capacity fading caused by side reactions between the active material and organic electrolyte. In this work, Li+-conductive Li2SnO3 was coated on the surface of LiNi0.5Mn1.5O4 to protect the cathode against the attack of HF, mitigate the dissolution of Mn ions during cycling and improve the Li+ diffusion coefficient of the materials. Remarkable improvement in cycling stability and rate performance has been achieved in Li2SnO3-coated LiNi0.5Mn1.5O4. The 1.0 wt% Li2SnO3-coated LiNi0.5Mn1.5O4 cathode exhibits excellent cycling stability with a capacity retention of 88.2% after 150 cycles at 0.1 C and rate capability at high discharge rates of 5 C and 10 C, presenting discharge capacities of 119.5 and 112.2 mAh g-1, respectively. In particular, a significant improvement in cycling stability at 55 °C is obtained after the coating of 1.0 wt% Li2SnO3, giving a capacity retention of 86.8% after 150 cycles at 1 C and 55 °C. The present study provides a significant insight into the effective protection of Li-conductive coating materials for a high-voltage LiNi0.5Mn1.5O4 cathode material.

A core-shell structured LiNi0.5Mn1.5O4@LiCoO2 cathode material with superior rate capability and cycling performance.

A core-shell structured LiNi0.5Mn1.5O4@LiCoO2 cathode material has been successfully synthesized by the combination of sol-gel and solid state methods. The coating of LiCoO2 has a significant effect on the electrochemical performance of the spinel LiNi0.5Mn1.5O4-based cathode material, especially the cycling stability at high temperature and rate capability. After modification, the ionic conductivity of the material is greatly improved due to the high ion conductivity of LiCoO2. The LiNi0.5Mn1.5O4@LiCoO2 with 1% LiCoO2 presents the optimal rate capability and delivers a relatively high discharge capacity of 122 mA h g-1 at 10C. On the other hand, the surface coating of LiCoO2 can effectively facilitate Li+ interfacial diffusion, and alleviate the side reactions between the active material and the electrolyte; as a result, the capacity retention of 96.17% for the LiNi0.5Mn1.5O4@LiCoO2 electrode with 1% LiCoO2 is much higher than that for the bare LiNi0.5Mn1.5O4 (74.93%) after 100 cycles at elevated temperature. Our study confirms that the core-shell structure construction caused by the coating of LiCoO2 plays a critical role in the improvement of the electrochemical cycling stability at elevated temperatures and rate capability.