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The sodium dual ion battery (Na‐DIB) technology is proposed as highly promising alternative over lithium‐ion batteries for the stationary electrochemical energy‐storage devices. However, the sluggish reaction kinetics of anode materials seriously impedes their practical implementation. Herein, a Na‐DIB based on TiSe2‐graphite is reported. The high diffusion coefficient of Na‐ions (3.21×10−11–1.20×10−9 cm2 s−1) and the very low Na‐ion diffusion barrier (0.50 eV) lead to very fast electrode kinetics, alike in conventional surface capacitive storage systems. In‐situ investigations reveal that the fast Na‐ion diffusion involves four insertion stage compositions. A prototype cell shows a reversible capacity of 81.8 mAh g−1 at current density of 100 mA g−1, excellent stability with 83.52 % capacity retention over 200 cycles and excellent rate performance, suggesting its potential for next‐generation large scale high‐performance stationary energy storage systems. [ABSTRACT FROM AUTHOR]

Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO2 nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li+ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO2/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO2/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g–1 at 1 C (1 C = 335 mA g–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g–1, respectively. Moreover, the formed Li2Ti2O4 nanodots facilitate reversed Li+ insertion-extraction during the cycling process. The above results indicate the best performance of TiO2-based materials as anodes for lithium-ion batteries reported in the literature. [ABSTRACT FROM AUTHOR]

A hierarchical mesoporous TiO2 nanowire bundles (HM‐TiO2‐NB) superstructure with amorphous surface and straight nanochannels has been designed and synthesized through a templating method at a low temperature under acidic and wet conditions. The obtained HM‐TiO2‐NB superstructure demonstrates high reversible capacity, excellent cycling performance, and superior rate capability. Most importantly, a self‐improving phenomenon of Li+ insertion capability based on two simultaneous effects, the crystallization of amorphous TiO2 and the formation of Li2Ti2O4 crystalline dots on the surface of TiO2 nanowires, has been clearly revealed through ex situ transmission electron microcopy (TEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Raman, and X‐ray photoelectron spectroscopy (XPS) techniques during the Li+ insertion process. When discharged for 100 cycles at 1 C, the HM‐TiO2‐NB exhibits a reversible capacity of 174 mA h g−1. Even when the current density is increased to 50 C, a very stable and extraordinarily high reversible capacity of 96 mA h g−1 can be delivered after 50 cycles. Compared to the previously reported results, both the lithium storage capacity and rate capability of our pure TiO2 material without any additives are among the highest values reported. The advanced electrochemical performance of these HM‐TiO2‐NB superstructures is the result of the synergistic effect of hybriding of amorphous and crystalline (anatase/rutile) phases and hierarchically structuring of TiO2 nanowire bundles. Our material could be a very promising anodic material for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] The voltage decay of Li-rich layered oxide cathode materials results in the deterioration of cycling performance and continuous energy loss, which seriously hinders their application in the high-energy–density lithium-ion battery (LIB) market. However, the origin of the voltage decay mechanism remains controversial due to the complex influences of transition metal (TM) migration, oxygen release, indistinguishable surface/bulk reactions and the easy intra/inter-crystalline cracking during cycling. We investigated the direct cause of voltage decay in micrometer-scale single-crystal Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 (SC-LNCM) cathode materials by regulating the cut-off voltage. The redox of TM and O2− ions can be precisely controlled by setting different voltage windows, while the cracking can be restrained, and surface/bulk structural evaluation can be monitored because of the large single crystal size. The results show that the voltage decay of SC-LNCM is related to the combined effect of cation rearrangement and oxygen release. Maintaining the discharge cutoff voltage at 3 V or the charging cutoff voltage at 4.5 V effectively mitigates the voltage decay, which provides a solution for suppressing the voltage decay of Li-rich and Mn-based layered oxide cathode materials. Our work provides significant insights into the origin of the voltage decay mechanism and an easily achievable strategy to restrain the voltage decay for Li-rich and Mn-based cathode materials. [ABSTRACT FROM AUTHOR]

Hierarchically structured porous TiO2-B spheres have been synthesized via a hydrothermal process using amorphous titania/oleylamine composites as a self-sacrificing template. The TiO2-B spheres are constructed by interconnected nanotubes and possess a high specific surface area of 295 m2 g-1. When evaluated as an anode material in lithium-half cells, the as-obtained TiO2-B material exhibits high and reversible lithium storage capacity of 270 mA h g-1 at 1 C (340 mA g-1), excellent rate capability of 221 mA h g-1 at 10 C, and long cycle life with over 70% capacity retention after 1000 cycles at 10 C. The superior electrochemical performance of TiO2-B material strongly correlates to the synergetic superiorities with a combination of TiO2-B polymorph, hierarchically porous structure, interconnected nanotubes and spherical morphology. Post-mortem structural analyses reveal some discrete cubic LiTiO2 nanodots formed on the outer surfaces of TiO2-B nanotubes, which might account for the slight capacity loss upon prolonged electrochemical cycling. [ABSTRACT FROM AUTHOR]

[Display omitted] • A CNTs interconnected yolk-shell Si/C anode (YS-Si@CoNC) is designed via the chelation competition-induced polymerization (CCIP) for LIBs. • The CNTs and carbon shell provide an excellent electronically conductive network for the fast diffusion of electrons and Li+. • The unique yolk-shell structure greatly reduces the volume expansion of SiNPs in the cycling. • The YS-Si@CoNC anode presents outstanding electrochemical performances and structural stability. As a viable replacement to commercial graphite anodes, silicon (Si) anodes have gained much attention from academics because of their considerable theoretical specific capacity and appropriate reaction voltage. Nevertheless, some limitations still exist in developing silicon anodes, including significant volume expansion and poor electrical conductivity. Herein, the carbon nanotubes (CNTs) interconnected yolk-shell silicon/carbon anodes (YS-Si@CoNC) were prepared via the chelation competition induced polymerization (CCIP) approach. The YS-Si@CoNC anode, designed in this study, demonstrates improved performance. At the current density of 0.5 A g−1 and 1 A g−1, a capacity of 1001 mAh g−1 and 956.5 mAh g−1 can be achieved after 150 cycles and after 300 cycles, respectively. In particular, at the current density of 5 A g−1, the reversible specific capacity of 688 mAh g−1 is realized. The exceptional outcomes are mainly attributed to the internal voids that adequately alleviate the volumetric expansion and the CNTs and carbon shells that provide an efficient conducting matrix to fasten the diffusion of electrons and lithium-ions. Our research presents a convenient way of designing Si/C anode materials with a yolk-shell structure to guarantee impressive electrical conductivity and robust structural integrity for high-performance LIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • An inner amorphous titanium dioxide (TiO 2) and an outer flexible conductive polyaniline (PANI) network dual modified Si@TiO 2 @PANI material is designed. • The inner TiO 2 layer effectively ensures a stable SEI film to effectively decrease the side reactions. • The outer PANI network layer buffers the volume expansion and increases the electronic conductivity. • The as-prepared Si@TiO 2 @PANI exhibits highly improved electrochemical performance for LIBs. Silicon (Si) anode material is promising in the next generation of lithium-ion batteries (LIBs) with high energy densities for its much higher capacity (4200 mAh/g) than that of commercial graphite (372 mAh/g). However, silicon anode material with low electronic conductivity suffers a huge volume variation and accompanies side reactions during alloyed and de-alloyed process. Here, we design an inner amorphous titanium dioxide (TiO 2) and an outer flexible conductive polyaniline (PANI) network dual modified Si@TiO 2 @PANI material for LIBs, where the TiO 2 avoids the side reactions and the PANI network layer buffers the volume expansion and increases the electronic conductivity. The as-prepared Si@TiO 2 @PANI exhibits a high initial discharge capacity of 3050 mAh/g and maintains 1583 mAh/g after 200 cycles at 0.5 A/g. It even delivers the discharge capacity of 1002 mAh/g after 600 cycles at 1 A/g, as well as an excellent rate ability with discharge capacity of 1890, 1260 and 432 mAh/g at the high current density of 1, 2 and 5 A/g, respectively. Our strategy shows that the innovative design of double buffer layers on Si can synergistically promote stability and accelerate kinetics of Li+ transport, offering novel resolution strategy to enhance the performance of Si-based anodes for LIBs. [ABSTRACT FROM AUTHOR]

The as-fabricated Mn 3 O 4 /graphene nanocomposite by a novel Mn-alkoxide nanoplates hydrolysis method exhibits excellent performance in terms of cycling performance and rate capability for lithium storage. [Display omitted] Herein we develop a novel and effective alkoxide hydrolysis approach to in-situ construct the trimanganese tetraoxide (Mn 3 O 4)/graphene nanostructured composite as high-performance anode material for lithium-ion batteries (LIBs). This is the first report on the synthesis of Mn 3 O 4 /graphene composite via a facile hydrolysis of the manganese alkoxide (Mn-alkoxide)/graphene precursor. Before hydrolysis, two dimensional (2D) Mn-alkoxide nanoplates are closely adhered to 2D graphene nanosheets via Mn-O chemical bonding. After hydrolysis, the Mn-alkoxide in-situ converts to Mn 3 O 4 , while the Mn-O bond is preserved. This leads to a robust Mn 3 O 4 /graphene hybrid architecture with 15 nm Mn 3 O 4 nanocrystals homogeneously anchoring on graphene nanosheets. This not only prevents the Mn 3 O 4 nanocrystals agglomeration but also inversely mitigates the graphene nanosheets restacking. Moreover, the flexible and conductive graphene nanosheets can accommodate the volume change. This maintains the structural and electrical integrity of the Mn 3 O 4 /graphene electrode during the cycling process. As a result, the Mn 3 O 4 /graphene composite displays superior lithium storage performance with high reversible capacity (741 mAh g−1 at 100 mA g−1), excellent rate capability (403 mAh g−1 at 1000 mA g−1) and long cycle life (527 mAg g−1 after 300 cycles at 500 mA g−1). The electrochemical performance highlights the importance of rational design nanocrystals anchoring on graphene nanosheets for high-performance LIBs application. [ABSTRACT FROM AUTHOR]

N, O, S co-doped hierarchically porous carbon nanobelts with fast channels and special defects exhibit high capacity and excellent cycling stability for Li-ion and Li-Se batteries. • Defect-rich HPCNBs are derived from the whole organic Melamnie-based polymer network. • N, O, S co-doping HPCNBs enhances the electrical conductivity and chemical affinity. • The Se@HPCNB nanocomposite has fast channels and dual confinement for active species. • The Se@HPCNB nanocomposite demonstrates stable and long-term cycle for Li-ion and Li-Se batteries. Li-Se battery is a promising energy storage candidate owing to its high theoretical volumetric capacity and safe operating condition. In this work, for the first time, we report using the whole organic Melamine-based porous polymer networks (MPNs) as a precursor to synthesize a N, O, S co-doped hierarchically porous carbon nanobelts (HPCNBs) for both Li-ion and Li-Se battery. The N, O, S co-doping resulting in the defect-rich HPCNBs provides fast transport channels for electrolyte, electrons and ions, but also effectively relieve volume change. When used for Li-ion battery, it exhibits an advanced lithium storage performance with a capacity of 345 mAh g−1 at 500 mA g−1 after 150 cycles and a superior rate capacity of 281 mAh g−1 even at 2000 mA g−1. Further density function theory calculations reveal that the carbon atoms adjacent to the doping sites are electron-rich and more effective to anchor active species in Li-Se battery. With the hierarchically porous channels and the strong dual physical–chemical confinement for Li 2 Se, the Se@ HPCNBs composite delivers an ultra-stable cycle performance even at 2 C after 1000 cycles. Our work here suggests that introduce of heteroatoms and defects in graphite-like anodes is an effective way to improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

The voltage fade of Li-rich layered oxide cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 (LNCM) heavily hinders its application in Li-ion batteries. Herein, we revisit the origin of the voltage fade of LNCM and propose a solution to suppress this effect. It is demonstrated that the voltage fade of the LNCM cathode comes from the structural change of the crystal from layer structure to spinel structure, involving all the cations rearrangement. Such rearrangement of all the cations in LNCM is due to the high degree of delithiation and oxygen release at high cutoff voltage of 4.8 V. It is also evidenced that nickel and cobalt change from low valence to high valence at the discharged state, which not only inhibits the transport of lithium ions, but also leads to the loss of high voltage platforms. In particular, the cation rearrangement of Li/Mn causes valence change from Mn4+ to Mn3+, resulting in the decrease of discharge voltage platform at the cutoff voltage of 4.8 V much higher than at 4.6 V. The lower charge cutoff voltage can be a solution to suppress the voltage fade of LNCM cathode materials and have a good stability of LNCM cathode materials without compromising the battery performance. Image 1 • The voltage fade of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 comes from the layer to spinel structure. • All the cations rearrangement involves in the structure change. • Nickel and cobalt change from low valence to high valence at the discharged state. • The Mn4+ to Mn3+ in Mn rearrangement decreases the discharge voltage platform. • The lower charge cutoff voltage is a solution to suppress the voltage fade of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 without compromising the battery performance. [ABSTRACT FROM AUTHOR]

Graphical abstract The nitrogen-doped graphene (NG) in-situ modification of MnO nanoparticles (MnO/NG) can largely improve the electrochemistry performance for lithium storage. Highlights • The nitrogen-doped graphene (NG) in-situ modifying MnO nanoparticles (MnO/NG) • NG promoting the electron transfer and improving the reaction activity. • NG alleviating the MnO agglomeration during the reaction. • NG accommodating the volume change of MnO during the cycling process. • MnO/NG exhibiting highly enhanced reversible capacity and cycling capability. Abstract We report the nitrogen-doped graphene (NG) in-situ modifying MnO nanoparticles (MnO/NG) to improve the electrochemistry performance for lithium storage. The NG in-situ modification not only improves the electrical conductivity but also alleviates the agglomeration and accommodates the volume change of MnO nanoparticles during the cycling process. More importantly, the non-heat treatment is beneficial to maintain the original structure and crystal shape of MnO. As a results, the MnO/NG exhibits a high reversible capacity of 1005 mAh/g after 100 cycles at 100 mA/g, four times that of pure MnO nanoparticles (209 mAh/g) and almost twice that of in-situ carbonization of MnO nanoparticles (MnO/C) (490 mAh/g). Particularly, the MnO/NG demonstrates a stable cycling capacity of 549 mAh/g after 1000 cycles at 1000 mA/g without pulverization. This work confirms that nitrogen-doped graphene in-situ modification is a more efficient strategy comparing to carbon modification for transition metal oxides as anode materials for highly improved lithium storage. [ABSTRACT FROM AUTHOR]

• A surface K + and PO 4 3− co-doped Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 is synthesized by a facile one-pot method. • The K + and PO 4 3− doping can enlarge the Li+ slabs to facilitate the diffusion of Li+ and suppress the irreversible release of lattice oxygen. • This co-doping inhibits the phase transformation, thus improving the electrochemical performance of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 cathode. The high specific capacity and voltage of Li-rich Mn-based oxides make them promising cathode materials for high-energy-density lithium-ion batteries (LIBs). However, the problems such as low initial coulombic efficiency, fast capacity and voltage fading, poor kinetics, large voltage hysteresis, and poor safety performance hamper their fast commercialization. Herein, we report one-pot K+ and PO 4 3− co-doping Li-rich Mn-based oxides Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 cathode material to improve the electrochemical performance of the lithium-ion battery. On the one hand, K+ doping can stabilize the bulk structure and enlarge the Li slabs to facilitate the diffusion of Li+, resulting in enhanced cycling and rate performance. On the other hand, PO 4 3− doping changes the electronic structure of the material and weakens the covalency of TM-O, decreasing the irreversible loss of lattice oxygen and stabilizing the structure. As a result, the K+ and PO 4 3− co-doping can effectively alleviate the capacity and voltage decay and the modified sample shows better cycling stability (88.6%@0.5 C@250 cycles) and rate performance (155.5 mAh g −1@5 C) compared to the pristine material. Our strategy here provides a facile one-pot method to modify Li-rich Mn-based oxides cathode material for high-performance LIBs. [Display omitted] [ABSTRACT FROM AUTHOR]

To develop high-performance anode materials of lithium ion batteries (LIBs) for practical high energy application, a grain boundaries enriched hierarchically mesoporous MnO/C microsphere composite has been fabricated by an in-situ carbonization process. The mesoporous MnO/C microsphere is constructed by abundant grains and grain boundaries that are uniformly embedded in a carbon matrix. Such unique nanoarchitecture exhibits high tap density and structural stability, and provides 3D continuous transport pathways for electrons and Li-ions, enabling high electrochemical stability and improved lithium storage kinetics. As a consequence, the mesoporous MnO/C electrode delivers ever-increasing specific capacity (1200 mAh g −1 after 100 cycles at 100 mA g −1 ) and excellent rate capability (588 mAh g −1 at 2 A g −1 ). Such superior lithium storage performance suggests that the hierarchically mesoporous MnO/C microsphere electrode should be one of the most promising anode materials for electric vehicle and grid energy storage application. [ABSTRACT FROM AUTHOR]

Porous TiO 2 urchins have been synthesized by a hydrothermal route using TiO 2 /oleylamine as precursors with subsequent ion-exchange and calcination. The resultant material consists of porous spherical cores and nanochains-constructed shells with straight channels. Electrochemical measurements indicate the TiO 2 urchins deliver superior lithium storage capability in terms of high capacity (206.2 mA h g −1 at 0.5 C), superior rate performance (94.4 mA h g −1 at 20 C) and stable cycling stability (94.3% capacity retention over 1000 cycles at 10 C versus the third cycle). Such performance enhancement is mainly due to the increased electrode/electrolyte contact interface, reduced Li + diffusion pathways and improved mass transfer of electrolyte in the unique 3D interconnected hierarchical network. In addition, ex-situ XRD, SEM and TEM analyses further reveal high structure integrity of the porous TiO 2 urchins during the electrochemical lithiation, leading to enhanced lithium storage stability. Moreover, we detected that some anatase nanocrystals evolved into electrochemically inactive Li 1 TiO 2 dots (∼10 nm in size) during long-term electrochemical cycling. Our findings provide more insights for better understanding of the structure evolution and capacity decay mechanism in porous TiO 2 nanostructures. [ABSTRACT FROM AUTHOR]

Highlights: [•] A facile and fast refluxing method develops hierarchical and porous V2O5 spheres. [•] The porosity and morphology of vanadyl glycolate can be tuned by rinsing with water. [•] Hierarchical and porous V2O5 spheres possess high lithium ion storage property. [ABSTRACT FROM AUTHOR]

Highlights: [•] A fast microwave hydrothermal route is developed to prepare porous anatase spheres. [•] The TiO2 spheres are constructed of interconnected nanocrystals with wormlike pores. [•] The TiO2 spheres exhibit high Li ion storage capacity and good rate capability. [•] The Li ion storage property of TiO2 spheres varies with pore size and crystallinity. [ABSTRACT FROM AUTHOR]

Growing ordered CuO nanorods on 2D Cu/g-C 3 N 4 nanosheets as stable freestanding anode exhibits outstanding electrochemical performance for lithium storage. • 2D Cu nanosheets are grown on porous g-C 3 N 4 nanosheets (Cu/g-C 3 N 4). • Ordered CuO nanorods are grown on Cu/g-C 3 N 4 nanosheets (CuO@Cu/g-C 3 N 4). • The freestanding CuO@Cu/g-C 3 N 4 anode achieves outstanding lithium storage. Two dimensional (2D) nanostructures are promising to provide a new hierarchical architecture for transition metal oxides (TMOs) with outstanding lithium storage. In this work, we grew ordered CuO nanorods on 2D Cu/g-C 3 N 4 nanosheets to form the hierarchical CuO@Cu/g-C 3 N 4 nanorods film as freestanding anode for advanced lithium storage. This assembled freestanding film demonstrates a high discharge specific capacity at 726 mAhg−1 after 200 cycles at 0.1C and a discharge specific capacity of 457 mAhg−1 after 625 cycles at 1C, among the best performance in CuO and CuO based nanostructures for lithium storage. Its outstanding stability and cyclic performance are ascribed to the following aspects during the reaction process: (i) the unique 2D nanostructure provides large exposed area for Li+ insertion, (ii) the ordered CuO nanorods provide interior spaces to accommodate the volume change and offer more paths for charges and Li+ transfer, (iii) the existence of Cu nanosheets increases the electrons transport and (iv) the porous g-C 3 N 4 nanosheets endow the prepared structure more active sites for facilitating Li+ transport and accommodating volume change. Our strategy on growing ordered nanostructures on 2D nanosheets will be an effective way to modify TMOs for advanced lithium-ion batteries. [ABSTRACT FROM AUTHOR]