Hard carbon has been regarded as the most promising anode material for sodium‐ion batteries (SIBs) due to its low cost, high reversible capacity, and low working potential. However, the uncertain ...sodium storage mechanism hinders the rational design and synthesis of high‐performance hard carbon anode materials for practical SIBs. During the past decades, tremendous efforts have been put to stimulate the development of hard carbon materials. In this review, we discuss the recent progress of the study on the sodium storage mechanism of hard carbon anodes, and the effective strategies to improve their sodium storage performance have been summarized. It is anticipated that hard carbon anodes with high electrochemical properties will be inspired and fabricated for large‐scale energy storage applications.
Hard carbon electrode materials have been considered as a state‐of‐the‐art anode material for sodium‐ion batteries. However, the uncertain sodium storage mechanism hinders the development of high‐performance hard carbon anode materials for practical application. Herein, the progress in the sodium storage mechanism of hard carbon anodes and the effective strategies to improve their sodium storage performance are summarized. It is anticipated that this article will facilitate a better understanding of the development of hard carbon anode materials.
Carbon coating is a popular strategy to boost the cyclability of Si anodes for Li-ion batteries. However, most of the Si/C nanocomposite anodes fail to achieve stable cycling due to the easy ...separation and peeling off of the carbon layer from the Si surface during extended cycles. To overcome this problem, we develop a covalent modification strategy by chemically bonding a large conjugated polymer, poly-peri-naphthalene (PPN), on the surfaces of nano-Si particles through a mechanochemical method, followed by a carbonization reaction to convert the PPN polymer into carbon, thus forming a Si/C composite with a carbon coating layer tightly bonded on the Si surface. Due to the strong covalent bonding interaction of the Si surface with the PPN-derived carbon coating layer, the Si/C composite can keep its structural integrity and provide an effective surface protection during the fluctuating volume changes of the nano-Si cores. As a consequence, the thus-prepared Si/C composite anode demonstrates a reversible capacity of 1512.6 mA h g–1, a stable cyclability over 500 cycles with a capacity retention of 74.2%, and a high cycling Coulombic efficiency of 99.5%, providing a novel insight for designing highly cyclable silicon anodes for new-generation Li-ion batteries.
Electrolytes as an important part of sodium-ion batteries have a pivotal role for capacity, rate, and durability of electrode materials. On account of the high reduction activity of sodium metal with ...organic solvents, it is very important to optimize the electrolyte component to realize high stability on Na metal and hard carbon anodes. Herein, chemical and electrochemical stability of propylene carbonate (PC)-based electrolytes on sodium metal and hard carbon anodes is investigated systematically. The results demonstrate that whether using NaClO4 or NaPF6, the PC-based electrolytes are not stable on Na metal, but adding of FEC can immensely enhance the stability of the electrolyte because of the compact solid electrolyte interphase film formed. The electrolytes containing FEC also exhibit high electrochemical compatibility on hard carbon anodes, showing high reversible capacity and excellent cycling performance. A reaction mechanism based on the Na+ induction effect is proposed by spectrum and electrochemical measurements. This study can provide a new insight to optimize and develop stable PC-based electrolytes and be helpful for understanding the other electrolyte systems.
As promising cathode materials, iron‐based phosphate compounds have attracted wide attention for sodium‐ion batteries due to their low cost and safety. Among them, sodium iron fluorophosphate ...(Na2FePO4F) is widely noted due to its layered structure and high operating voltage compared with NaFePO4. Here, a mesoporous Na2FePO4F@C (M‐NFPF@C) composite derived from mesoporous FePO4 is synthesized through a facile ball‐milling combined calcination method. Benefiting from the mesoporous structure and highly conductive carbon, the M‐NFPF@C material exhibits a high reversible capacity of 114 mAh g−1 at 0.1 C, excellent rate capability (42 mAh g−1 at 10 C), and good cycling performance (55% retention after 600 cycles at 5 C). The high plateau capacity obtained (>90% of total capacity) not only shows high electrochemical reversibility of the as‐prepared M‐NFPF@C but also provides high energy density, which mainly originates from its mesoporous structure derived from the mesoporous FePO4 precursor. The M‐NFPF@C serves as a promising cathode material with high performance and low cost for sodium‐ion batteries.
A mesoporous Na2FePO4F@C (M‐NFPF@C) composite derived from mesoporous FePO4 is synthesized through a facile ball‐milling combined calcination method. Benefiting from the mesoporous structure and highly conductive carbon, the M‐NFPF@C material exhibits a high reversible capacity of 114 mAh g−1 at 0.1 C, excellent rate capability (42 mAh g−1 at 10 C), and good cycling performance (55% retention after 600 cycles at 5 C).
Iron sulfides with high theoretical capacity and low cost have attracted extensive attention as anode materials for sodium ion batteries. However, the inferior electrical conductivity and devastating ...volume change and interface instability have largely hindered their practical electrochemical properties. Here, ultrathin amorphous TiO2 layer is constructed on the surface of a metal–organic framework derived porous Fe7S8/C electrode via a facile atomic layer deposition strategy. By virtue of the porous structure and enhanced conductivity of the Fe7S8/C, the electroactive TiO2 layer is expected to effectively improve the electrode interface stability and structure integrity of the electrode. As a result, the TiO2‐modified Fe7S8/C anode exhibits significant performance improvement for sodium‐ion batteries. The optimal TiO2‐modified Fe7S8/C electrode delivers reversible capacity of 423.3 mA h g−1 after 200 cycles with high capacity retention of 75.3% at 0.2 C. Meanwhile, the TiO2 coating is conducive to construct favorable solid electrolyte interphase, leading to much enhanced initial Coulombic efficiency from 66.9% to 72.3%. The remarkable improvement suggests that the interphase modification holds great promise for high‐performance metal sulfide‐based anode materials for sodium‐ion batteries.
Ultrathin amorphous TiO2 layer is directly constructed on the surface of Fe7S8/C electrode by facile atomic layer deposition strategy. Benefiting from TiO2 surface modification, the Fe7S8@C electrode exhibits much improved sodium storage performance (423.3 mA h g−1 after 200 cycles at 0.2 C with high capacity retention of 75.3% and enhanced initial coulombic efficiency of 72%).
Many renewable energy technologies, especially batteries and supercapacitors, require effective electrode materials for energy storage and conversion. For such applications, metal‐organic frameworks ...(MOFs) and covalent‐organic frameworks (COFs) have been recently emerged as promising candidates. Their high surface area, organized channel, and multiple functions make them highly versatile and flexible as electrodes, electrolytes, and electrocatalysts in electrochemical energy storage (EES) systems. In addition, many MOFs/COFs‐derived materials tend to possess high conductivity and diverse nanoarchitecture, and can also serve as high‐performance electrodes. In this review, we summarize the extensive potentials of both frameworks and their derivatives in a range of devices, including lithium/sodium ion, lithium‐sulfur, lithium‐oxygen batteries, and supercapacitors. In addition, we discuss the remaining challenges in this area and propose potential solutions for them as well as outline a few possible directions for further development for EES applications.
Metal/covalent organic frameworks (MOFs/COFs) have received wide attention for electrochemical energy storage (EES) due to their unique structural characteristics. Herein, we summarize the applications of MOFs/COFs and their derivatives in EES, including lithium/sodium ion, lithium‐sulfur, lithium‐oxygen batteries, and supercapacitors. Moreover, the development perspective of MOFs/COFs in EES is also outlined.
As a promising cathode material, Na3V2(PO4)2F3 (NVPF) has attracted wide attention for sodium-ion batteries (SIBs) because of its high operating voltage and high structural stability. However, the ...low intrinsic electronic conductivity and insufficient Na ion mobility of NVPF limit its development. Herein, K-doping NVPF is prepared through a facile ball-milling combined calcination method. The effects of K-doping on the crystal structure, kinetic properties and electrochemical performance are investigated. The results demonstrate that the Na2.90K0.10V2(PO4)3F3 (K0.10-NVPF) exhibits a high capacity (120.8 mAh g−1 at 0.1 C), high rate capability (66 mAh g−1 at 30 C) and excellent cycling performance (a capacity retention of 97.5% at 1 C over 500 cycles). Also, the occupation site of K ions in the lattice, electronic band structure and Na-ion transport kinetic property in K-doped NVPF are investigated by density functional theory (DFT) calculations, which reveals that the K-doped NVPF exhibits improved electronic and ionic conductivities, and located K+ ions in the lattice to contribute to high reversible capacity, rate capability and cycling stability. Therefore, the K-doped NVPF serves as a promising cathode material for high-energy and high-power SIBs.
A novel cathode, K doped Na3V2(PO4)2F3 is synthesized by a facile ball-milling method. With the structural advantages and the suitable K doping site, the K-doped Na3V2(PO4)2F3 cathode exhibits enhanced sodium storage performance in terms of high specific capacity, excellent rate capability, and superior cycling stability. Display omitted
To understand Baduanjin rehabilitation therapy in mild COVID-19 patients.
A narrative review.
A literature search for COVID-19 and Baduanjin treatments was conducted on Chinese and English electronic ...databases: China National Knowledge Infrastructure, Wanfang Data, Embase, PubMed, Scopus, Science Direct, Ebscohost, SPORTDiscus and ProQuest.
Twelve studies on the Baduanjin rehabilitation for COVID-19 patients have been included. We acknowledged the considerable published research and current clinical practice using Baduanjin for COVID-19 treatment in the following areas: anxiety, depression, insomnia, lung function rehabilitation, immunity and activity endurance.
The use of Baduanjin as adjuvant therapy for COVID-19 patients' rehabilitation is still limited, therefore, more clinical studies are needed to confirm its efficacy.
Hard carbons (HC) have potential high capacities and power capability, prospectively serving as an alternative anode material for Li‐ion batteries (LIB). However, their low initial coulombic ...efficiency (ICE) and the resulting poor cyclability hinder their practical applications. Herein, a facile and effective approach is developed to prelithiate hard carbons by a spontaneous chemical reaction with lithium naphthalenide (Li‐Naph). Due to the mild reactivity and strong lithiation ability of Li‐Naph, HC anode can be prelithiated rapidly in a few minutes and controllably to a desirable level by tuning the reaction time. The as‐formed prelithiated hard carbon (pHC) has a thinner, denser, and more robust solid electrolyte interface layer consisting of uniformly distributed LiF, thus demonstrating a very high ICE, high power, and stable cyclability. When paired with the current commercial LiCoO2 and LiFePO4 cathodes, the assembled pHC/LiCoO2 and pHC/LiFePO4 full cells exhibit a high ICE of >95.0% and a nearly 100% utilization of electrode‐active materials, confirming a practical application of pHC for a new generation of high capacity and high power LIBs.
A facile chemical prelithiation approach is developed to eliminate the irreversible capacity loss of hard carbon (HC) anode via a spontaneous chemical reaction with lithium naphthalenide reagent. When paired with LiCoO2 cathode, the HC/LiCoO2 full cell demonstrates a high initial coulombic efficiency of >95.0%, confirming a practical application for high energy and high power Li‐ion batteries.
Sodium-ion batteries(SIBs) are promising for grid-scale energy storage applications due to the natural abundance and low cost of sodium. Among various Na insertion cathode materials, Na
0.44
MnO
2
...has attracted the most attention because of its cost effectiveness and structural stability. However, the low initial charge capacity for Na-poor Na
0.44
MnO
2
hinders its practical applications. Herein, we developed a facile chemical presodiated method using sodiated biphenly to transform Na-poor Na
0.44
MnO
2
into Na-rich Na
0.66
MnO
2
. After presodiation, the initial charge capacity of Na
0.44
MnO
2
is greatly enhanced from 56.5 mA·h/g to 115.7 mA·h/g at 0.1 C(1 C=121 mA/g) and the excellent cycling stability(the capacity retention of 94.1% over 200 cycles at 2 C) is achieved. This presodiation strategy would open a new avenue for promoting the practical applications of Na-poor cathode materials in sodium-ion batteries.
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