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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. [ABSTRACT FROM AUTHOR]

Laser scribing technology is a straightforward technique to fabricate porous graphene, yet only conducted with polymeric precursors. Compared to polymers, molecular engineering of small organic molecules is much easier, which can be used to modify the graphene with tailored performance. Here we report the first employment of a laser to respectively transform small organic molecules, pentacene quinone and tetraazapentacene quinone (TAPQ), into graphene (P‐LIG and N‐LIG) as high‐performance lithium‐ion battery anodes. The TAPQ, as the N‐fused molecular precursor, produces nitrogen‐doped graphene. Both N‐LIG and P‐LIG exhibit significant self‐enhancement of capacity upon cycling; the N‐LIG anode delivers reversible capacities of 5863 mAh g‐1 at 0.2 A g‐1 and retains 1970 mAh g‐1 at 2 A g‐1 after another 500 cycles, which is the best performance for the graphene‐type anode. Kinetics studies and structural characterizations verify that the surface‐ and diffusion‐controlled processes are both progressively optimized, providing extra lithium storage upon cycling. It is also supported by small‐angle X‐ray scattering that the disordering level of micropores is increased upon cycling for N‐LIG, corresponding to the enhancement of microporous level. Our work successfully develops a novel facile approach to fabricating heteroatom‐doped microporous graphene exhibiting high performance and provides new insight into the lithium storage mechanism. [ABSTRACT FROM AUTHOR]

Hard carbon has the potential to serve as a high‐capacity anode material for sodium‐ion batteries (SIBs), however, its Na+ storage mechanism, particularly on the low potential plateau, remains controversial. To overcome this issue, two types of hard carbons with different microstructures are employed and the relationship between the microstructures and Na+ storage behaviors is evaluated. By the combination of operando X‐ray diffraction, ex situ Raman spectroscopy, NMR, and theoretical calculation, it is found that the sodium storage capacities of the hard carbons in the low potential plateau region contain the concurrent contributions from both interlayer intercalation and micropores filling, and the ratio of the two contributors greatly depends on the microstructure of hard carbon materials. Moreover, an electrochemical pointer (potential inflection point at the end of the discharge curve) is found to distinguish the dominance of interlayer intercalation and the micropores filling processes of sodium ions in the low potential plateau region. Based on this new finding, a microstructure‐dependent mechanism ("adsorption‐intercalation/filling" hybrid mechanism) is proposed to achieve an overall understanding of the sodium storage behaviors in different hard carbon materials, which may provide deep insight into the rational design of hard carbon structures as high‐performance anode materials for advanced SIBs. [ABSTRACT FROM AUTHOR]

The application of lithium metal anodes for practical batteries is still impeded by safety issues and low Coulombic efficiency caused mainly by the uncontrollable growth of lithium dendrites. Herein, two types of free‐standing nitrogen‐doped amorphous Zn–carbon multichannel fibers are synthesized as multifunctional hosts for lithium accommodation. The 3D macroporous structures endow effectively reduced local current density, and the lithiophilic nitrogen‐doped carbon and functional Zn nanoparticles serve as preferred deposition sites with low nucleation barriers to guide uniform lithium deposition. As a result, the developed anodes exhibit remarkable electrochemical properties in terms of high Coulombic efficiency for more than 500 cycles at various current densities from 1 to 5 mA cm−2, and symmetric cells show long‐term cycling duration over 2000 h. Moreover, full cells based on the developed anode and a LiFePO4 cathode also demonstrate superior rate capability and stable cycle life. [ABSTRACT FROM AUTHOR]

The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS2 coated hollow carbon particles preloaded with sulfur (C@MoS2/S), was designed to modify the LMA. The C@MoS2 hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium‐based components. These two factors together effectively suppress the growth of Li dendrites. The as‐modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm−2. When matched with a LiFePO4 cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA. [ABSTRACT FROM AUTHOR]

The design and synthesis of hierarchical microboxes, assembled from SnS nanoplates coated with nitrogen‐doped carbon (NC) as an anode material for sodium‐ion batteries, is demonstrated. The template‐engaged multistep synthesis of the SnS@NC microboxes involves sequential phase transformation, polydopamine coating, and thermal annealing in N2. The SnS@NC composite with two‐dimensional nano‐sized subunits rationally integrates several advantages including shortening the diffusion path of electrons/Na+ ions, improving electric conductivity, and alleviating volume variation of the electrode material. As a result, the SnS@NC microboxes show efficient sodium storage performance with high capacity, good cycling stability, and excellent rate capability. Thinking outside the box: Hierarchical microboxes constructed from SnS nanoplates coated with N‐doped carbon (NC) were synthesized as an anode material for sodium‐ion batteries. Benefiting from the unique structural and compositional advantages, the SnS@NC microboxes show efficient sodium storage performance with high capacity, long cycling stability, and superior rate capability. [ABSTRACT FROM AUTHOR]

Tin(II) sulfide (SnS) has been an attractive anode material for sodium ion batteries. Herein, an elegant templating method has been developed for the rational design and synthesis of hierarchical SnS nanotubes composed of ultrathin nanosheets. In order to enhance the electrochemical performance, carbon coated hierarchical SnS nanotubes (denoted as SnS@C nanotubes) have also been obtained by simply adding glucose into the reaction system. Benefiting from their unique structural merits, the SnS@C nanotubes exhibit enhanced sodium storage properties in terms of good cycling performance and superior rate capability. [ABSTRACT FROM AUTHOR]

3D graphene decorated NaTi2(PO4)3 (NTP@rGO) is successfully synthesized through a facile spray‐drying method. This NTP@rGO material can deliver high reversible capacity (130 mAh g−1 at 0.1 C), superior high‐rate rate capability (38 mAh g−1 at 200 C) and long cycling stability (77% capacity retention after 1000 cycles), suggesting its applicability as a high rate and cycle‐stable anode for the development of high‐power and long cycle life sodium ion batteries for energy storage applications. [ABSTRACT FROM AUTHOR]

A TiO2@reduced graphene oxide (TiO2@rGO) composite is synthesized successfully by a simple spray-drying method. The structural and morphological characterizations reveal that the TiO2@rGO composite has a sphere-like morphology with diameters of 5-15 µm, and each microsphere is actually a random aggregation of primary TiO2 nanoparticles, which are tightly covered by soft graphene sheets. The TiO2@rGO electrode exhibits enhanced electrochemical performance of high charge capacity (170 mA h g−1 at 0.1 C), long cycling life (87% of capacity retention after 300 cycles at 0.2 C), and high rate capability (55 mA h g−1 at 10 C). Compared with bare TiO2 microspheres, the improved electrochemical performance of the TiO2@rGO composite benefits from the introduction of graphene as a highly conductive, flexible, and large-surface-area scaffold to provide good electronic contact between active materials, suppress the aggregation of intermediate products, and alleviate the volume change during sodiation and desodiation. The encouraging experimental results suggest that the TiO2@rGO composite has great potential as a high-capacity and high-stability anode for the sodium-ion batteries. [ABSTRACT FROM AUTHOR]

The reduced surface porosity of highly compacted graphite anode after calendering is one of the major obstacles restraining the fast‐charging capability and low‐temperature adaptability of lithium‐ion batteries. In this work, through‐hole carbon spheres (THCS) synthesized by coaxial electrospinning and the following template sacrifice method are employed as a pore‐forming agent on graphite surfaces for the first time. The established gradient porosity architecture endows graphite anode with interconnected conductive networks and abundant Li+ transport channels. Therefore, the THCS pouch cell exhibits fast charging capability (charging efficiency of 49.2% at 5 C), superior cycling stability (96% capacity retention after 500 cycles at 1 C), and low‐temperature adaptability (high lithium plating resistance at −10 °C). By contrast, severe lithium‐plating behavior is observed in the blank pouch cell under the same testing conditions. It is believed that the facile and scalable gradient pore structure manufacturing technology will succeed in promoting the fast‐charging capability and low‐temperature adaptability of commercial Li‐ion batteries. [ABSTRACT FROM AUTHOR]