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Abstract The effect of Co amount on the sodium storage properties of Sn 1- x Co x (x = 0.2–0.5) alloys is systematically investigated. The trade-off between the cycle stability and the reversible capacity is identified. It is found that the reduced capacity with increased amount of Co is not only due to its inactive nature towards reaction with Na, but also because of its poor Na+ diffusion rate, which hinders the accessibility of "Sn" in Sn 1- x Co x (x = 0.2–0.5) alloys. The optimal sample, Sn 0.7 Co 0.3 , delivers a reasonably high reversible capacity and shows a good cycle stability (i.e. , delivers ∼200 mAh/g over 80 cycles and ∼300 mAh/g over 60 cycles at room temperature and 40 °C, respectively). Highlights • Sn 1- x Co x (x = 0.2–0.5) alloys have been synthesized via HEMM. • Effect of Co amount on the sodium storage properties of Sn 1- x Co x was investigated. • Co matrix helps to stabilize the cycle stability of Sn 1- x Co x in Na cell. • High testing temperature (40 °C) improves the sodiation/de-sodiation kinetics of Sn 1- x Co x. • Sn 0.7 Co 0.3 delivers a stable capacity as well as high volumetric capacity in Na cell. [ABSTRACT FROM AUTHOR]

Lithium-metal batteries have attracted extensive research attention because of their high energy densities. Developing appropriate electrolytes compatible with lithium-metal anodes is of great significance to facilitate their practical application. Currently used electrolytes still face challenges of high production costs and unsatisfactory Coulombic efficiencies of lithium plating/stripping. In this research, we have developed a diluted electrolyte which is compatible with both lithium-metal anode and sulfurized polyacrylonitrile cathode. It presents a very high Li plating/stripping Coulombic efficiency of 99.3% over prolonged cycling, and the as-assembled anode-free Li-S battery maintains 71.5% of the initial specific capacity after 200 cycles at 0.1 A g−1. This work could shed light on designing a low-cost and high-performance liquid electrolyte for next-generation high-energy batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of different-type diluents on manipulating solvation chemistry are highlighted. • An evolutive solvation structure and interfacial model are also presented. • Diverse behaviors for Li depositions and corresponding interfacial chemsitry are compared. • The full cells based high-voltage cathode with different systems are also explored. The growth of dendrites on lithium metal anode is troublesome because it induces irreversible capacity loss and safety hazards. Formulating localized high-concentration electrolytes (LHCEs) is an alternative solution to satisfy these challenges. However, the role of diluents in tailoring interfacial chemistry remains to be explicated. Herein, we decipher the direct relationship between different-type diluents and Li-coordinated solvation at the molecular scale. Compare to hydrofluoroethers (HFE), the "active" difluoro ethylene carbonate (DFEC) delivers a pronounced interaction with Li+ and 1, 2-dimethoxyethane (DME) molecule, resulting in a compressed but more accumulated aggregates (AGGs) solvation shell, assisting in the expected chemical nature of SEI with defluorination of DFEC. Consequently, DFEC-based LHCEs (D-LHCEs) realize a record-long lifespan over 3000 h with dendrite-free at 1 mA cm−2 and outstanding dendrite tolerance even under 3 mA cm−2 in symmetric cells. The assembled full cells with D-LHCEs outperform a superior capacity retention of ∼86.83 % with average CE of ∼99.42 % after 500 cycles at 0.5C and the remarkable cycling performance even under harsh conditions (including pouch cells or with controlled N/P of 1.8) in 4.45 V-level Li||LiCoO 2 cells. This work highlights the decisive role of diluents in pursuing high-efficiency electrolytes for high-energy Li metal batteries. [ABSTRACT FROM AUTHOR]

Tin dioxide (SnO 2) is a promising anode material for lithium-ion and sodium-ion batteries. However, the huge volume expansion during cycling makes it far away from practical application. Herein, we report a template-free "heterogeneous carbonization" strategy for fabricating SnO 2 /carbon/void/carbon nanofibers (SCVC) compound membrane with finite spatial domain in carbon matrix as buffer layer for volume changes of SnO 2. Reduced graphene oxide (rGO) is also imported into the SCVC membrane, acting as conductive binders to construct a free-standing SCVC-rGO electrode with exceptionally conductive network. The resultant SCVC-rGO anodes in lithium/sodium-ion batteries could deliver excellent electrochemical performances of higher reversible capacity, longer lifespan and superior rate capability. As lithium-ion battery anode, the SCVC-rGO electrode shows specific capacities of 950 mA h g−1 after 400 cycles at a current of 0.5 A g−1, and 824 mA h g−1 after 650 cycles at 1 A g−1. In sodium-ion batteries, the SCVC-rGO electrode gives rise to the specific capacity of 407 mA h g−1 after 2000 cycles at the current of 1 A g−1 with exceptional capacity retention. SnO 2 /carbon/void/carbon nanofibers membrane combined with reduced graphene oxide (SCVC-rGO) is constructed by a template free, one-step heterogeneous carbonization strategy. The internal void formed in situ in SnO 2 /C can be used as confined space to accommodate its volume expansion, while the residual ultrathin carbon layer on SnO 2 nanocrystals can prevent their amalgamation and recrystallization. The SCVC-rGO anodes exhibit excellent cycling stability and rate capability in LIBs and SIBs. [Display omitted] • One-step strategy of heterogenous carbonization to in-situ form buffering voids. • Based on the different carbon yields from various precursors and without the help of templates and corrosives. • Internal voids and residual ultrathin carbon layer ensure the complete reversibility of electrochemical reactions. • Excellent cycling stability and rate capability in half cells of LIBs and SIBs have been achieved. [ABSTRACT FROM AUTHOR]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Abstract: Li4Ti5O12 anode material is synthesized using TiO2 with different crystal structure as titanium source by solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test methods are applied to characterize the effects of TiO2 crystal structure on the structure, morphology and electrochemical performance of Li4Ti5O12. Results show that the reaction of TiO2 with Li2CO3 is an exothermic behavior. The reactivity of TiO2 with Li2CO3 gradually decreases and the particles size of Li4Ti5O12 increases with the TiO2 crystal structure changing from amorphous to rutile. The TiO2 crystal structure has a slight influence on the reversibility of Li4Ti5O12, while the specific capacities of Li4Ti5O12 at different current densities decreases obviously with the TiO2 crystal structure changing from amorphous to rutile and the sample using amorphous TiO2 as titanium sources shows highest specific capacity. The capacity retentions of all Li4Ti5O12 samples are above 97% after 50 cycles and these materials show good cycle performance. The TiO2 crystal structure has not large effects on the cycling performance of Li4Ti5O12 material. [Copyright &y& Elsevier]

As a promising anode for potassium-ion batteries (PIBs), graphite has drawn great attention due to easy availability, low cost and formation of potassium-based intercalation compound. However, poor cyclic and rate performances due to severe structural degradation limit the practical application of graphite anode. Herein, a low cost mildly-expanded graphite (MEG) with adjustable interlayer lattice distance is synthesized through a wet chemical oxidation route. As anode for PIBs, the MEG exhibited stable intercalation/deintercalation plateaus, outstanding cyclic stability and rate performance. By optimizing the mass ratio between graphite and potassium permanganate oxidant, the MEG anode retaining long-range-ordered domains of graphite delivers a capacity of 88 mAh/g at 1500 mA/g and a capacity retention of 72.3% after 200 cycles at 100 mA/g. The potassium ion full cell assembled with MEGs anode exhibites high energy density and outstanding cyclic stability. Our results demonstrate a promising graphite-based anode for PIBs and provide guidance for the designing of novel carbonic electrodes for PIBs. Image 1 [ABSTRACT FROM AUTHOR]

• Micron-sized Sn 4 P 3 was prepared via high energy mechanical milling. • Initial capacity of Sn 4 P 3 in diglyme-based electrolyte is as high as 960.3 mAh/g. • Sn 4 P 3 shows a record capacity of 719.7 mAh/g after 100 cycles. • ICE of Sn 4 P 3 anode in diglyme-based electrolyte reaches up to 89.8%. • The superior sodium storage performance of Sn 4 P 3 is enabled by diglyme-derived SEI. Sodium-ion batteries (SIBs) have great potential for large scale energy storage applications due to geopolitical abundance of sodium resource. However, the development of SIBs is hindered by the available anodes with high reversible capacity and long cycle life. Herein, we report that micron-sized Sn 4 P 3 anode delivers superior sodium storage performance when used in combination with diglyme-based electrolyte. The first reversible capacity of Sn 4 P 3 anode in diglyme-based electrolyte reaches up to 960.3 mAh/g at current density of 100 mA/g, and a record capacity after 100 cycles (i.e. 719.7 mAh/g) is achieved for Sn 4 P 3 -based anodes to date. Moreover, the initial Coulombic efficiency of the anode is 89.8%, which is one of the highest values among Sn 4 P 3 -based anodes. Ex-situ SEM and XPS study reveals that the outstanding performance is mainly enabled by the ether-derived solid electrolyte interphase, which preserves the integrity of electrode and constructs a robust interphase with favorable kinetics. [ABSTRACT FROM AUTHOR]

Metallic Na possesses high specific capacity and lowest electrochemical potential of all possible candidates, and therefore being regarded as one of the most promising anode materials for Na batteries. Nevertheless, unstable solid electrolyte interface, infinite volume change and uncontrollable dendritic Na growth upon repeated Na plating/stripping processes lead to low Coulombic efficiency, poor cyclability and safety concerns of Na metal anode. Herein, a three-dimensional carbon felt host was employed to suppress Na dendrite growth, thus achieving highly reversible Na plating/stripping process. The interstitial space inside the carbon felt framework accommodates Na deposition, and the plentiful active sites guide homogenous Na nucleation and growth without dendrite formation. As a result, the carbon felt exhibits stable cycling lifetime for 1100 h and 350 h at 1 mA cm−2 and 2 mA cm−2 respectively, which are 5.6 and 3.9 times longer than that of Al foil. Moreover, the carbon felt possesses high average Coulombic efficiency of ∼99.3% for 500 cycles at 0.5 mA cm−2. When paired with Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode, the full cell delivers a high capacity retention of 95.1% over 150 cycles. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Efficient lithium-ion electrodes with impressive long-life cycling and high-rate performance are badly in need for large-scale energy storage systems, but it is challenging as well because of large volume expansion during lithium storage. Here through a facile and general strategy, we construct yolk-shell ZnCo 2 O 4 (Y-ZCO) spheres as an efficient anode for LIBs. The method involves a simple solvothermal process and subsequent annealing in air. The as-prepared Y-ZCO spheres reveal a high structural robustness and porous textural property. When acted as electrode material for LIBs, these Y-ZCO spheres show enhanced electrochemical performances. It displays a high specific capacity (1138 mA h g−1 at a current rate of 0.2 A g−1), superior capacity retention, and long-cycling stability (103.5% capacity retention ratio at 0.2 A g−1 for 100 cycles and 92.3% capacity retention ratio at 1 A g−1 for 300 cycles). All these results reveal that the Y-ZCO spheres could be potential anode materials for rechargeable batteries. More importantly, the present route is expedient and facile. It can be expected that the strategy could be spread to prepare other hollow mixed metal oxides with complex interior structures. Highlights • Yolk-shell ZnCo 2 O 4 spheres (Y-ZCO) are prepared by carbon-templating solvothermal synthesis. • The Y-ZCO anode shows excellent rate performance and cycling stability. • The Y-ZCO anode shows high structural robustness. [ABSTRACT FROM AUTHOR]

Sodium-ion hybrid capacitors (NIHC) with sodium ion battery type anodes and supercapacitor type cathodes are emerging as an attractive energy storage device due to the integration of high energy, high power and long lifetime. However, the battery type electrodes usually exhibit sluggish reaction kinetics than capacitor type cathodes due to slow Na ion insertion and extraction, which greatly hinders the rate performance. In this paper, carbon coated MoS 2 nanosheets are vertically grown on carbon cloth (CC) substrate using a hydrothermal reaction followed by calcination. The expanded interlayer distance of the MoS 2 ensures high ionic mobility while the highly conductive CC not only provides a self-supporting structure without the addition of insulative binder and additional conductive additive, but also effectively prevents the restacking of the MoS 2 sheets during cycling. Thus the architecture delivers a high area capacity of 0.511 mAh cm −2 at a current density of 0.2 mA cm −2 and a stable capacity retention of 83.3% after 200 cycles at 1 mA cm −2 . Furthermore, NIHC constructed with above anode delivers a high areal energy density of 1.22 mWh cm −2 at a power of 0.76 mW cm −2 , demonstrating an excellent energy-power delivery. [ABSTRACT FROM AUTHOR]

Abstract: The development of lithium (Li) metal anodes Li metal batteries faces huge challenges such as uncontrolled Li dendrite growth and large volume change during Li plating/stripping, resulting in severe capacity decay and high safety hazards. A 3D porous copper (Cu) current collector as a host for Li deposition can effectively settle these problems. However, constructing a uniform and compact 3D porous Cu structure is still an enormous challenge. Herein, an electrochemical etching method for Cu–Zinc (Zn) alloy is reported to precisely engrave a 3D Cu structure with uniform, smooth, and compact porous network. Such a continuous structure endows 3D Cu excellent mechanical properties and high electrical conductivity. The uniform and smooth pores with a large internal surface area ensures well dispersed current density for homogeneous Li metal deposition and accommodation. A smooth and stable solid electrolyte interphase is formed and meanwhile Li dendrites and dead Li are effectively suppressed. The Li metal anode conceived 3D Cu current collector can stably cycle for 400 h under an Li plating/stripping capacity of 1 mA h cm−2 and a current density of 1 mA cm−2. The Li@3D Cu||LiFePO4 full cells present excellent cycling and rate performances. The electrochemical dealloying is a robust method to construct 3D Cu current collectors for dendrite‐free Li metal anodes. [ABSTRACT FROM AUTHOR]

Abstracts Hollow and urchin-like CoCO 3 dumbbell microspheres (HCCM) and CoCO 3 @reduced graphene oxide composite microspheres (CC@rGO) were synthesized by one-step solvothermal methods. RGO modification significantly improves the cycling stability of CoCO 3 microsphere anodes at low current densities. CC@rGO delivers 1067 and 997 mAh/g after 50 cycles at 0.1 C and 100 cycles at 0.2 C, respectively. Interestingly, HCCM shows rising cycling stability with increased rates while CC@rGO exhibits slight and continuous capacity fading at almost all rates thus declining advantage with rising rates. A competition theory between “protective force” mainly from solid electrolyte interface (SEI) or rGO layer and “destructive force” from volume swing applied on the microspheres was raised to clarify this phenomenon. The changing volume swing degree and SEI formation rate with increased rates, as well as different protective effects of HCCM and CC@rGO's SEI film or rGO layer, determined various competition results of the two forces at each rate thus various structural stability and cycling performance of the two samples. Furthermore, the application prospect of CoCO 3 anodes in lithium ion full cells has been explored and the assembled LiCoO 2 ||CC@rGO exhibits an initial coulombic efficiency of 92.9%, a discharge mid-voltage of 2.3 V and stable cycling performance. [ABSTRACT FROM AUTHOR]

To boost the commercialization of high energy density lithium ion batteries (LIBs) used for electric vehicles, the development of electrode materials with high volumetric capacity is of great significance. In this work, a novel Si/slightly exfoliated graphite (SEG)/carbon composite used as anode for LIBs with high volumetric capacity is fabricated. The Si nanoparticles are uniformly intercalated in the squashed interlayers of SEG which are then further filled by amorphous carbon. The SEG acts as a conductivity skeleton, while the spaces between squashed interlayers(folds) in SEG function as buffer spaces for the expansion of Si nanoparticles during lithiation reactions. The amorphous carbon connects the Si nanoparticles with SEG to form a 3D conductive network. Owing to the high packing density (0.7 g cm −3 ) and unique structure, this material possesses a high volumetric capacity of 1050 mAh cm −3 . Meanwhile, the Si/SEG/C composite also exhibits excellent rate and cyclic performance, presenting a reversible capacities of 1456 and 1056 mAh g −1 at 100 and 500 mA g −1 with capacity retention of 84.7% after 50 cycles at 500 mA g −1 . This work opens up an avenue to craft the Si/C composite with high volumetric energy densities and rate performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A uniform protective layer composed of Li x Al y SiO z /Li 2 O is formed by the chemical reaction of aluminum isopropoxide with Li x Si. • The modified Li x Si has high lithium reserves and great environmental adaptability. • The storage time under the condition of certain oxygen and water content can be prolonged. In recent years, lots of efforts have been applied to improve the initial Coulombic efficiency (ICE) of lithium-ion batteries (LIBs), among which prelithiation is considered to be one of the most promising schemes. Here we report a modified Li x Si with high lithium reserves and great environmental adaptability as the prelithiation reagent, which can make up for the capacity loss of the negative electrode in the first cycle. Through the chemical reaction between aluminum isopropoxide and Li x Si, a protective layer consisting of Li x Al y SiO z /Li 2 O is formed on the surface of Li x Si particles. This synthesized material provides a new idea for the actual industrial production of prelithiation. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the formation of SEI films on Li4Ti5O12 (LTO) anodes offers a major benefit to large-scale applications of lithium ion batteries made therefrom. This paper reveals that an SEI film is formed above 1 V due to the interfacial reaction between the electrode and electrolyte: LTO anodes are previously considered free from SEI films when cycled between 1 and 3 V. The reactivity and the formation of SEI films are much affected by the morphology and surface area of the electrode. To study the above, LTO powders with different morphologies are synthesized using lithium acetate (LA) and lithium hydroxide (LH) as the lithium sources. LTO–LH consisting of agglomerates of primary small particles with a large surface area has higher reactivity than LTO–LA with a cubic structure and small surface area. As a result, the LTO–LH anode with a smooth SEI film offers better cyclic performance than the LTO–LA anode with a porous SEI film. The addition of vinylene carbonate to the electrolyte facilitates rapid formation of a protective SEI film on LTO–LA, greatly improving the rate and cyclic performance: stable specific capacity of 155.6 mAh g−1 and remarkable 135.2 mAh g−1 after 500 cycles at 10 C are recorded. [Copyright &y& Elsevier]

Abstract: Bamboo-shaped carbon nanotubes (BCNTs), with a large amount of pentagon defects introduced in the walls, were explored as the support of high loaded Pt–Ru catalysts for the anode of direct methanol fuel cells (DMFCs) in comparison with conventional carbon nanotubes (CNTs) and Vulcan XC carbon black. By ethylene glycol reduction, Pt–Ru catalysts with a high loading (60wt%) and uniform particle size of 2–3nm were uniformly deposited on BCNTs; while 60wt% Pt–Ru catalysts on CNTs resulted in significant agglomeration. The Pt–Ru/BCNT catalyst showed the highest activity on methanol oxidation in cyclic voltammetry and highest performance as the anode in a DMFC single cell. Such an enhancement was largely ascribed to an enhanced interaction of the introduced pentagon defects with Pt–Ru, which could promote a high loading and well dispersion of Pt–Ru catalysts and the charge transfer from Pt–Ru to the tubes. [Copyright &y& Elsevier]

Nonuniform local electric field and few nucleation sites on the reactive interface tend to cause detrimental lithium (Li) dendrites, which incur severe safety hazards and hamper the practical application of Li metal anodes in batteries. Herein, a carbon nanofiber (CNF) mat decorated with ultrafine titanium nitride (TiN) nanoparticles (CNF‐TiN) as both current collector and host material is reported for Li metal anodes. Uniform Li deposition is achieved by a synergetic effect of lithiophilic TiN and 3D CNF configuration with a highly conductive network. Theoretical calculations reveal that Li prefers to be adsorbed onto the TiN sheath with a low diffusion energy barrier, leading to controllable nucleation sites and dendrite‐free Li deposits. Moreover, the pseudocapacitive behavior of TiN identified through kinetics analysis is favorable for ultrafast Li+ storage and the charge transfer process, especially under a high plating/stripping rate. The CNF‐TiN‐modified Li anodes deliver lower nucleation overpotential for Li plating and superior electrochemical performance under a large current density (200 cycles at 3 mA cm−2) and high capacity (100 cycles with 6 mAh cm−2), as well as a long‐running lifespan (>600 h). The CNF‐TiN‐based full cells using lithium iron phosphate and sulfur cathodes exhibit excellent cycling stability. [ABSTRACT FROM AUTHOR]