Co0.85Se Nanoparticles Encapsulated by Nitrogen-Enriched Hierarchically Porous Carbon for High-Performance Lithium-Ion Batteries

Hierarchical porous carbon materials for lithium storage: preparation, modification, and applications

Secondary battery as an efficient energy conversion device has been highly attractive for alleviating the energy crisis and environmental pollution. Hierarchical porous carbon (HPC) materials with multiple sizes pore channels are considered as promising materials for energy conversion and storage applications, due to their high specific surface area and excellent electrical conductivity. Although many reviews have reported on carbon materials for different fields, systematic summaries about HPC materials for lithium storage are still rare. In this review, we first summarize the main preparation methods of HPC materials, including hard template method, soft template method, and template-free method. The modification methods including porosity and morphology tuning, heteroatom doping, and multiphase composites are introduced systematically. Then, the recent advances in HPC materials on lithium storage are summarized. Finally, we outline the challenges and future perspectives for the application of HPC materials in lithium storage.

Molten salt-confined pyrolysis towards heteroatom-doped porous carbon nanosheets for high-energy-density Zn-ion hybrid supercapacitors

Carbon nanosheets with heteroatom doping and well-developed porosity exhibit broad application foreground for Zn-ion hybrid supercapacitors (ZHSCs), but the simple and controllable preparation is still of great challenge. In this study, by using LiCl-KCl as in-built templates, histidine as carbon and nitrogen sources, and KNO₃, K₂SO₄, KOH or Na₂S₂O₃ as active agent, a series of N and NS doped porous carbon nanosheets are developed. Results indicate that, with the activator introduction, pore structures of the carbonized products are notably boosted, showing an astounding 30-244 % increase in BET specific surface area, and meanwhile, heteroatom with a content of ca. 12 % can be doped into the resultant carbon skeletons. Specifically, the NSPCN-800 (activated by Na₂S₂O₃) with a large specific surface area of 1297 m²/g, a hierarchically porous structure composed of abundant micropores and mesopores, and a suitable heteroatom content (N: 11.9 wt%; S: 0.6 wt%) presents an impressive energy storage behavior as cathode for ZHSCs, including a specific capacitance of 165.8F/g, a specific capacity of 95.2 mAh/g, an energy density of 59.0 Wh kg^-1 and a cyclic stability with a 82.6 % capacity retention after 5000 cycles. These performance parameters surpass numerous reported ZHSCs, making NSPCN-800 a very promising cathode for practical use.

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 Co_0.85Se nanoparticles encapsulated in the inner wall of N-doped carbon matrix nanotubes (Co_0.85Se@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, Co_0.85Se 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 Co_0.85Se nanoparticles, thereby improving the cyclic stability. Based on the above advantages, as expected, the electrochemical investigations exhibited that the Co_0.85Se@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.

Ant-nest-like Cu2-xSe@C with biomimetic channels boosts the cycling performance for lithium storage

Controlling the microstructure and composition of electrodes is crucial to enhance their rate capability and cycling stability for lithium storage. Inspired by the highly interconnected network and good mechanical integrity of an ant-nest architecture, herein, a biomimetic strategy is proposed to enhance the electrochemical performance of Cu2-xSe. After facile carbonization and selenization treatments, the 3D Cu-MOF is successfully transformed into the final ant-nest-like Cu2-xSe@C (AN-Cu2-xSe@C). The AN-Cu2-xSe@C is composed of interconnected Cu2-xSe channels with amorphous carbon coated on the outer surface. The 3D interconnected channels within the AN-Cu2-xSe@C provide fast charge transport pathways and enhanced structural integrity to tolerate the large volume fluctuations of Cu2-xSe during cycling. When applied as the anode for lithium storage, the AN-Cu2-xSe@C shows remarkable electrochemical performance with a high capacity of 1452 mA h g-1 after 1200 cycles at 1.0 A g-1 and 879 mA h g-1 after 2500 cycles at 10.0 A g-1, respectively. Mechanism investigations demonstrate that the AN-Cu2-xSe@C experiences complicated conversion-intercalation co-existence reactions upon cycling. The existence of capacitive behaviour (74%) also contributes to the extended cycling performance. Our work offers a new avenue for designing a high performance electrode using the biomimetic concept.

Synthesis of a novel Ce(iii)/melamine coordination polymer and its application for corrosion protection of AA2024 in NaCl solution

We present the synthesis of a new cerium(iii)-melamine coordination polymer (CMCP) by a mixed-solvothermal method and its characterization. Characterization techniques included Raman, Fourier Transformation Infra-Red (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), in which the change in the electronic environment and the crystallinity were tracked. The characterization results confirm the coordination of cerium(iii) with melamine through -NH2 groups, instead of the N atoms of the triazine ring, for which we propose a mechanism of interaction. In addition, Biovia Materials Studio package was applied to determine and investigate the molecular structure of the CMCP. All simulations were done using COMPASS force-field theory and atom-based method for summation of electrostatic and van de Waals forces. The application of the CMCP for the corrosion inhibition of AA2024 in 3.5% NaCl solution was tested using the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results point out that the presence of cerium as cerium(iii) in the CMCP structure plays the fundamental role of inhibition, whereby the inhibition mechanism occurs by cathodic oxidation of Ce(iii) to Ce(iv) and cyclic reduction of Ce(iv) to Ce(iii) by melamine part of CMCP.

Ultrafine Co0.85Se nanocrystals dispersed in 3D CNT network as a flexible free-standing anode for high-performance lithium-ion battery

A flexible free-standing film electrode with high pseudocapacitive contribution and strengthened cyclic stability was successfully prepared.