Revealing the Charge Storage Mechanism in Porous Carbon to Achieve Efficient K Ion Storage.

Constructing a porous structure is considered an appealing strategy to improve the electrochemical properties of carbon anodes for potassium-ion batteries (PIBs). Nevertheless, the correlation between electrochemical K-storage performance and pore structure has not been well elucidated, which hinders the development of high-performance carbon anodes. Herein, various porous carbons are synthesized with porosity structures ranging from micropores to micro/mesopores and mesopores, and systematic investigations are conducted to establish a relationship between pore characteristics and K-storage performance. It is found that micropores fail to afford accessible active sites for K ion storage, whereas mesopores can provide abundant surface adsorption sites, and the enlarged interlayer spacing facilitates the intercalation process, thus resulting in significantly improved K-storage performances. Consequently, PCa electrode with a prominent mesoporous structure achieves the highest reversible capacity of 421.7 mAh g-1 and an excellent rate capability of 191.8 mAh g-1 at 5 C. Furthermore, the assembled potassium-ion hybrid capacitor realizes an impressive energy density of 151.7 Wh kg-1 at a power density of 398 W kg-1. The proposed work not only deepens the understanding of potassium storage in carbon materials with distinctive porosities but also paves a path toward developing high-performance anodes for PIBs with customized energy storage capabilities.

Aspergillus niger fermentation residues application to produce biochar for the anode of lithium-ion batteries.

Aspergillus niger is widely applied in the fermentation industry, but produce abundant mycelium residues every year. As a kind of solid waste, mycelium residues seriously affect the environment. How to manage and utilize this solid waste is a problem for the fermentation industry. It was reported that many kinds of biomass could be utilized to produce carbon materials, which would be further used to produce lithium-ion rechargeable batteries (LIBs). Here, porous biochar was prepared from A. niger mycelial residues and further used as an anode for LIBs. Since the A. niger mycelium contains abundant nitrogen (5.29%) from its chitosan-dominated cell wall, and silicon (9.63%) from perlite filter aid, respectively, the biochar presented an excellent cycle stability and rate performance when applied as the anode of LIBs. The conclusion of this research shows the wide application prospect of fungal fermentation residues as carbon precursors in energy storage devices. Meanwhile, this investigation provides an alternative management method for A. niger mycelium residues, with which the mycelium residues could be effectively recycled to avoid resource waste and environmental pollution.

ZnS/CoS@C Derived from ZIF-8/67 Rhombohedral Dodecahedron Dispersed on Graphene as High-Performance Anode for Sodium-Ion Batteries.

Metal sulfides are highly promising anode materials for sodium-ion batteries due to their high theoretical capacity and ease of designing morphology and structure. In this study, a metal-organic framework (ZIF-8/67 dodecahedron) was used as a precursor due to its large specific surface area, adjustable pore structure, morphology, composition, and multiple active sites in electrochemical reactions. The ZIF-8/67/GO was synthesized using a water bath method by introducing graphene; the dispersibility of ZIF-8/67 was improved, the conductivity increased, and the volume expansion phenomenon that occurs during the electrochemical deintercalation of sodium was prevented. Furthermore, vulcanization was carried out to obtain ZnS/CoS@C/rGO composite materials, which were tested for their electrochemical properties. The results showed that the ZnS/CoS@C/rGO composite was successfully synthesized, with dodecahedrons dispersed in large graphene layers. It maintained a capacity of 414.8 mAh g-1 after cycling at a current density of 200 mA g-1 for 70 times, exhibiting stable rate performance with a reversible capacity of 308.0 mAh g-1 at a high current of 2 A g-1. The excellent rate performance of the composite is attributed to its partial pseudocapacitive contribution. The calculation of the diffusion coefficient of Na+ indicates that the rapid sodium ion migration rate of this composite material is also one of the reasons for its excellent performance. This study highlights the broad application prospects of metal-organic framework-derived metal sulfides as anode materials for sodium-ion batteries.

Polyvinylpyrrolidone-derived nitrogen-doped carbon-coated MoS2 composites for enhanced sodium storage performance.

Two-dimensional transition metal dichalcogenides, which display considerable theoretical capacity and large layer spacing, have been regarded as promising candidates as anode materials for sodium-ion batteries (SIBs). However, their low conductivity and large volume change during charge-discharge cycles leads to performance degradation. Herein, polyvinylpyrrolidone (PVP) is used as a soft template to synthesize PVP-derived nitrogen-doped carbon-coated MoS2 composites (MoS2/NC) by a simple hydrothermal method followed by high-temperature treatment. The as-prepared composite exhibits a flowerball-like morphology and a diameter of approximately 250 nm. The optimized MoS2/NC has the most uniform particle size and provides the best performance, with a stable capacity of 504.9 mAh g-1 after 120 cycles at a current density of 100 mA g-1. It has excellent rate performance, which can reach 524.6, 481.9, 447.7, 412.5, and 370.9 mAh g-1 at current densities of 0.1, 0.2, 0.5, 1 and 2 A g-1, respectively. The small particle size and the addition of carbonaceous materials play an important role in their excellent electrochemical properties. This study opens up a simple and effective way to synthesize high-performance two-dimensional MoS2 composite anodes for SIBs.

Induced bimetallic sulfide growth with reduced graphene oxide for high-performance sodium storage.

Metal sulfide has been considered an ideal sodium-ion battery (SIB) anode material based on its high theoretical capacity. Nevertheless, the inevitable volume expansion during charge-discharge processes can lead to unsatisfying electrochemical properties, which limits its further large-scale application. In this contribution, laminated reduced graphene oxide (rGO) successfully induced the growth of SnCoS4 particles and self-assembled into a nanosheet-structured SnCoS4@rGO composite through a facile solvothermal procedure. The optimized material can provide abundant active sites and facilitate Na+ ion diffusion due to the synergistic interaction between bimetallic sulfides and rGO. As the anode of SIBs, this material maintains a high capacity of 696.05 mAh g-1 at 100 mA g-1 after 100 cycles and a high-rate capability of 427.98 mAh g-1 even at a high current density of 10 A g-1. Our rational design offers valuable inspiration for high-performance SIB anode materials.

Polypyrrole Modified MoS2 Nanorod Composites as Durable Pseudocapacitive Anode Materials for Sodium-Ion Batteries.

As a typical two-dimensional layered metal sulfide, MoS2 has a high theoretical capacity and large layer spacing, which is beneficial for ion transport. Herein, a facile polymerization method is employed to synthesize polypyrrole (PPy) nanotubes, followed by a hydrothermal method to obtain flower-rod-shaped MoS2/PPy (FR-MoS2/PPy) composites. The FR-MoS2/PPy achieves outstanding electrochemical performance as a sodium-ion battery anode. After 60 cycles under 100 mA g-1, the FR-MoS2/PPy can maintain a capacity of 431.9 mAh g-1. As for rate performance, when the current densities range from 0.1 to 2 A g-1, the capacities only reduce from 489.7 to 363.2 mAh g-1. The excellent performance comes from a high specific surface area provided by the unique structure and the synergistic effect between the components. Additionally, the introduction of conductive PPy improves the conductivity of the material and the internal hollow structure relieves the volume expansion. In addition, kinetic calculations show that the composite material has a high sodium-ion transmission rate, and the external pseudocapacitance behavior can also significantly improve its electrochemical performance. This method provides a new idea for the development of advanced high-capacity anode materials for sodium-ion batteries.

Structural Characteristics and Electrochemical Performance of N,P-Codoped Porous Carbon as a Lithium-Ion Battery Anode Electrode.

Biomass-derived heteroatom-doped carbons have been considered to be excellent lithium ion battery (LIB) anode materials. Herein, ultrathin g-C3N4 nanosheets anchored on N,P-codoped biomass-derived carbon (N,P@C) were successfully fabricated by carbonization in an argon atmosphere. The structural characteristics of the resultant N,P@C were elucidated by SEM, TEM, FTIR, XRD, XPS, Raman, and BET surface area measurements. The results show that N,P@C has a high specific surface area (S BET = 675.4 cm3/g), a mesoporous-dominant pore (average pore size of 6.898 nm), and a high level of defects (I D/I G = 1.02). The hierarchical porous structural properties are responsible for the efficient electrochemical performance of N,P@C as an anode material, which exhibits an outstanding reversible specific capacity of 1264.3 mAh/g at 100 mA/g, an elegant rate capability of 261 mAh/g at 10 A, and a satisfactory cycling stability of 1463.8 mAh/g at 1 A after 500 cycles. Because of the special structure and synergistic contributions from N and P heteroatoms, the resultant N,P@C endows LIBs with electrochemical performance superior to those of most of carbon-based anode materials derived from biomass in the literature. The findings in this present work pave a novel avenue toward lignin volarization to produce anode material for use in high-performance LIBs.

Achieving Cycling Durability of Lithium-Sulfur Batteries via Capturing Polysulfides through a Three-Dimensional Interconnected Carbon Network Anchored with Ultrafine FeS Nanoparticles.

Shuttle effect has always been a critical obstacle to the application of lithium-sulfur (Li-S) batteries for leading to unstable cycle performance and a short lifespan. To solve this problem, a particular strategy is put up to relieve shuttle effect by capturing soluble polysulfides through a three-dimensional interconnected carbon network. Due to the uniformly anchored ultrafine FeS nanoparticles on a 3D interconnected carbon network, the material could lock soluble polysulfides on the cathode side and promote electrochemical conversion reactions among sulfur species. By optimizing the active site exposure of FeS and designing a hierarchical porous and multichannel structure to ensure rapid migration of ions and electrons at the same time, the interlayer can effectively suppress the shuttle effect and enhance sulfur utilization. Thus, the Li-S battery presents excellent cycling stability and rate capability, namely, a reversible specific capacity of 560 mAh g-1 at 2.0 C over 500 cycles with a decay rate of 0.012% per cycle and a specific capacity of 597 mAh g-1 at a 5.0 C current rate. This study offers a promising strategy for designing the structure of an interlayer to achieve long-cycle stable Li-S batteries.

Sulfur-doped CoP@ Nitrogen-doped porous carbon hollow tube as an advanced anode with excellent cycling stability for sodium-ion batteries.

Transition metal phosphides have attracted increasing attention as anode materials for sodium-ion batteries (SIBs). Cobalt phosphide (CoP) has been deemed as prospective anode materials owing to its high theoretical capacity. Nevertheless, the defects of cobalt phosphides are evident. Low conductivity, the non-negligible volume expansion and aggregation of particles during sodiation/desodiation process result in poor cycling performance and rapid capacity decay, which greatly limit their applications. Herein, we designed a hollow-nanotube structure of sulfur-doped cobalt phosphide (S-CoP) nanoparticles coated by nitrogen-doped porous carbon (S-CoP@NPC), which can be successfully synthesized via an ordinary hydrothermal process followed by the low-temperature phosphorization/sulfuration treatment. The doping of sulfur element provides more active sites, meanwhile, the carbon coating largely helps to avoid the agglomeration of nanoparticles, alleviate volume expansion and improve the conductivity of materials. The S-CoP@NPC composite presents stable cycling performance, showing a discharge specific capacity of 230 mAh g-1 over 370 cycles at 0.2 A g-1. In addition, it also exhibits good rate capability with a discharge specific capacity of 143 mAh g-1 at 5 A g-1, even when the current density returns to 0.2 A g-1, the discharge specific capacity can recover 213 mAh g-1. Furthermore, the kinetic analysis of S-CoP@NPC composite explains that the excellent cycling and rate performance benefit from the extrinsic pseudocapacitive behavior.

MOF-templated self-polymerization of p-phenylenediamine to a polymer with a hollow box-assembled spherical structure.

This paper presents the first transformation of MOFs to polymers without any additives by using a one-step MOF-templated self-polymerization approach. We investigate the conversion process and demonstrate that the MOF-templated self-polymerization is a new and effective approach for the in situ conversion of organic ligands to polymers and even carbon nanomaterials with maintained MOF configurations.

1D ultrafine SnO2 nanorods anchored on 3D graphene aerogels with hierarchical porous structures for high-performance lithium/sodium storage.

SnO2 is considered as one of the most promising alternative anode materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs) due to high specific capacity, low discharge voltage plateau and environmental friendliness. In this work, 1D ultrafine SnO2 nanorods anchored on 3D graphene aerogel (SnO2 NRs/GA) composite is prepared through a simple reduction-induced self-assembly method in the solution of graphene oxide (GO), Vitamin C and SnO2 nanoparticles. Vitamin C plays an important role in the reduction of GO. The structural and morphological characterizations demonstrate that 1D ultrafine SnO2 nanorods are uniformly and tightly anchored on the surface of 3D graphene nanosheet aerogels. The unique 3D network structure as well as the synergistic effect between 3D graphene nanoshhet and 1D SnO2 nanorods endows the as-prepared SnO2 NRs/GA composite with the good electrochemical lithium/sodium storage performance. It delivers the high initial discharge capacity (1713 mA h g-1 at 0.1 A g-1 for LIBs and 539 mA h g-1 at 0.05 A g-1 for SIBs) and good cycle stability (869 mA h g-1 at 0.1 A g-1 after 50 cycles for LIBs and 232 mA h g-1 at 0.05 A g-1 after 100 cycles for SIBs). Moreover, the SnO2 NRs/GA composite exhibits excellent cycle stability for SIBs with a high reversible capacity of 96 mA h g-1 at as high as 1 A g-1 for 500 cycles. This work provides a simple method to fabricate the electro-active materials-graphene aerogel composites for high-performance LIBs and SIBs.

3D-0D Graphene-Fe3O4 Quantum Dot Hybrids as High-Performance Anode Materials for Sodium-Ion Batteries.

Transition metal oxides can be considered as appealing candidates for sodium ion battery anode materials because these low-cost materials possess high capacity and enhanced safety. However, the practical application of these materials is usually limited by their low electronic conductivity and serious volume change during the charging-discharging process. Herein, we report the fabrication of 3D-0D graphene-Fe3O4 quantum dot hybrids by a facile one-pot hydrothermal approach as anode materials for sodium-ion batteries. Fe3O4 quantum dots with an average size of 4.9 nm are anchored on the surface of 3D structured graphene nanosheets homogeneously. Such unique hierarchical structure are advantageous for enlarging the electrode/electrolyte interface area and enhancing the electrochemical activity of the hybrid materials, inhibiting particle aggregation of Fe3O4 and accommodating their volume change during the charging-discharging process as well as enabling fast diffusion of electrons and rapid transfer of electrolyte ions. Consequently, the 3D-0D graphene-Fe3O4 quantum dot hybrids exhibit ultrahigh sodium storage capacity (525 mAh g-1 at 30 mA g-1), outstanding cycling stability (312 mAh g-1 after 200 cycles at 50 mA g-1) and superior rate performance (56 mAh g-1 at 10 A g-1).

Nitrogen-Rich Mesoporous Carbon as Anode Material for High-Performance Sodium-Ion Batteries.

Nitrogen-rich carbon with interconnected mesoporous structure has been simply prepared via a nano-CaCO3 template method, using polyaniline as carbon and nitrogen precursors. The preparation process includes in situ polymerization of aniline in a nano-CaCO3 aqueous solution, carbonization of the composites and removal of the template with diluted hydrochloric acid. Nitrogen sorption shows the carbon-enriched mesopores with a specific surface area of 113 m(2) g(-1). The X-ray photoelectron spectroscopy (XPS) analysis indicates that the carbon has a high nitrogen content of 7.78 at. %, in the forms of pyridinic and pyrrolic, as well as graphitic nitrogen. The nitrogen-rich mesoporous carbon shows a high reversible capacity of 338 mAh g(-1) at a current density of 30 mA g(-1), and good rate performance as well as ultralong cycling durability (110.7 mAh g(-1) at a current density of 500 mA g(-1) over 800 cycles). The excellent sodium storage performance of the nitrogen-rich mesoporous carbon is attributed to its disordered structure with large interlayer distance, interconnected porosity, and the enriched nitrogen heteroatoms.