Heteroepitaxial growth of ZnO nanosheet bands on ZnCo204 submicron rods toward high-performance Li ion battery electrodes

We report the direct synthesis of ZnC0204 and ZnO/ZnC0204 submicron rod arrays grown on Ni foil current collectors via an ammonia-evaporation-induced method by controlling the ratio of Zn to Co. These three-dimensional （3D） hierar- chical self-supported nanostructures are composed of one-dimensional （1D） ZnCo204 rods and two-dimensional （2D） ZnO nanosheet bands perpendicular to the axis of the each ZnCo204 rod. We carefully deal with the heteroepitaxial growth mechanisms of hexagonal ZnO nanosheets from a crystallographic point of view. Furthermore, we demonstrate the ability of these high-surface-area ZnO/ZnCo204 heterostructured rods to enable improved electrolyte permeability and Li ion transfer, thereby enhancing their Li storage capability （-900 mA.h.g-1 at a rate of 45 mA.h.g-1） for Li ion battery electrodes.

Net-C18:A Predicted Two-Dimensional Planar Carbon Allotrope and Potential for an Anode in Lithium-Ion Battery

Net-C18,a predicted two-dimensional(2D)graphene-like carbon allotrope,is investigated via first-principles calculations.Its space group is Pmmm.There are 18 carbon atoms per cell.Net-C18 has five-,six-,and eight-membered rings.Net-C18 may be formed by adding even pairs of carbon atoms on the top of hexagons to reconstruct new five-and eight-membered rings,extending the strategy of Haeckelite.Compared to that of graphene(-9.28 e V atom^(-1)),the total energy of net-C18(-9.15 e V atom^(-1))is only 0.13 e V atom^(-1)higher,revealing that net-C18 is energetically metastable.The calculations of phonon and ab initio molecular dynamics(AIMD)demonstrate dynamical and thermal stability of net-C18.The independent elastic constants of net-C18 meet the criterial for the mechanical stability of 2D structure.Its in-plane stiffness along x or y axis is comparably large.The AIMD results reveal that net-C18 has good thermal stability at 1500 K.The band structure also demonstrates that it is metallic.Furthermore,the diffusion of Li atoms on net-C18 has a low energy barrier(0.32 e V),and net-C18 has a low open-circuit voltage(0.024 V)and a high theoretical specific capacity(403 m Ah g^(-1)).Thus,net-C18 may provide high-temperature resistant,flexible electrode in electronics and a promising metallic anode in lithium-ion battery.The proposed formation of net-C18 may open a new pattern defect for the designs of new carbon allotropes.

Recent progress on the recycling technology of Li-ion batteries

Lithium-ion batteries(LIBs)have been widely applied in portable electronic devices and electric vehicles.With the booming of the respective markets,a huge quantity of spent LIBs that typically use either LiFePO_(4) or Li N_(x)Co_(y)Mn_(z)O_(2) cathode materials will be produced in the very near future,imposing significant pressure for the development of suitable disposal/recycling technologies,in terms of both environmental protection and resource reclaiming.In this review,we firstly do a comprehensive summary of the-state-of-art technologies to recycle Li N_(x)Co_(y)Mn_(z)O_(2) and LiFePO_(4)-based LIBs,in the aspects of pretreatment,hydrometallurgical recycling,and direct regeneration of the cathode materials.This closed-loop strategy for cycling cathode materials has been regarded as an ideal approach considering its economic benefit and environmental friendliness.Afterward,as for the exhausted anode materials,we focus on the utilization of exhausted anode materials to obtain other functional materials,such as graphene.Finally,the existing challenges in recycling the LiFePO_(4) and Li N_(x)Co_(y)Mn_(z)O_(2) cathodes and graphite anodes for industrial-scale application are discussed in detail;and the possible strategies for these issues are proposed.We expect this review can provide a roadmap towards better technologies for recycling LIBs,shed light on the future development of novel battery recycling technologies to promote the environmental benignity and economic viability of the battery industry and pave way for the large-scale application of LIBs in industrial fields in the near future.

Silicon prepared by electro-reduction in molten salts as new energy materials

Silicon has a large impact on the energy supply and economy in the modern world. In industry, high purity silicon is firstly prepared by carbothermic reduction of silica with the produced raw silicon being further refined by a modified Siemens method. This process suffers from the disadvantages of high cost and contaminant release and emission. As an alternative, the molten salt electrolysis approach, particularly the FFC Cambridge Process(FFC: Fray-Farthing-Chen), could realize high purity silicon products with morphology-controllable nanostructures at low or mild temperatures(generally 650–900 ℃). In this article, we review the development, reaction mechanisms, and electrolysis conditions of silicon production by the FFC Cambridge Process. Applications of the silicon products from electrolysis in molten salts are also discussed in terms of energy applications, including using them as the photovoltaic element in solar cells and as the charge storage phase in the negative electrode(negatrode) of lithium ion batteries.

“All‐In‐One” integrated ultrathin SnS2@3D multichannel carbon matrix power high‐areal–capacity lithium battery anode

Construction of a thickness‐independent electrode with high active material mass loading is crucial for the development of high energy rechargeable lithium battery.Herein,we fabricate an all‐in‐one integrated SnS2@3D multichannel carbon matrix(SnS2@3DMCM)electrode with in‐situ growth of ultrathin SnS2 nanosheets inside the inner walls of three dimensional(3D)multichannels.The interconnected conductive carbon matrix derived from natural wood acts as an integrated porous current collector to avail the electrons transport and accommodate massive SnS2 nanosheets,while plenty of 3D aligned multichannels facilitate fast ions transport with electrode thickness‐independent even under high mass loading.As expected,the integrated SnS2@3DMCM electrode exhibits remarkable electrochemical lithium storage performance,such as exceptional high‐areal‐capacity of 6.4 mAh cm−2,high rate capability of 3 mAh cm−2 under current of 6.8 mAcm−2(10 C),and stable cycling performance of 6.8 mAcm−2 with a high mass loading of 7mg cm−2.The 3D integrated porous electrode constructing conveniently with the natural source paves new avenues towards future high‐performance lithium batteries.

Synthesis and Performance of LiMnO_2 as Cathodes for Li-ion Batteries

Two structure types of LiMnO 2 were synthesized by sol gel method and ion exchange method respectively.The results indicate that orthorhombic phase LiMnO 2 is more stable than layered LiMnO 2,o LiMnO 2 can be synthesized directly by sol gel methods followed by heat treated in argon,but layered LiMnO 2 was obtained only by indirect methods such as ion exchange method.In this paper,we first synthesized layered NaMnO 2 by the sol gel method,and then obtained layered LiMnO 2 by the ion exchange method.The phase constitution,chemical composition,and images of the products were tested by XRD,AAS (atomic absorption spectroscopy) and SEM.The electrochemical performances of the two structural types of LiMnO 2 are obviously different during the initial few cycles,but later they both have a good capacity retaining ability.The capacity of layered structure LiMnO 2 is higher than that of o LiMnO 2.

Preparation and electrochemical performance of Li_2Mn_(0.5)Fe_(0.5)SiO_4 cathode material with sol-gel method for lithium ion batteries

Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.

Low‐temperature synthesis of graphitic carbon‐coated silicon anode materials

We report the synthesis of a high‐performance graphitic carbon‐coated silicon(Si@GC)composite material for lithium‐ion batteries via a scalable production route.Porous Si is produced from the magnesiothermic reduction of commercial silica(SiO2)precursor followed by low‐temperature graphitic carbon coating using glucose as the precursor.The obtained Si@GC composite achieves an excellent reversible specific capacity of 1195 mAh g−1 and outstanding cycle stability.The thick Si@GC anode(3.4 mg cm^−2)in full cells with commercial lithium iron phosphate cathode delivers a remarkable performance of 800 mAh g^−1 specific capacity and 2.7 mAh cm^−2 areal capacity as well as 93.6%capacity retention after 200 cycles.

In‐situ structural characterizations of electrochemical intercalation of graphite compounds

Graphite carbon has been successfully used for the anode materials of secondary ion batteries due to its capability of accommodating ions between graphite layers.The intercalation dynamics intrinsically determine the performance of the batteries.In this review,we summarize recent research progresses of structural characterizations on graphite intercalation in electrochemical devices,especially on the in‐situ study on the intercalations of Li/Na/K ions,AlCl4−and other anions,or solvents.These techniques,including X‐ray,electron microscopy,Raman,neutron scattering,nuclear magnetic resonance,and optical microscopy provide direct information of the reaction dynamics and help to understand the factors affecting the electrochemical performances of metallic ion batteries.

A strategy to improve the electrochemical performance of Ni-rich positive electrodes:Na/F-co-doped LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)

Ni-rich layered lithium transition metal oxides LiNi_xMn_yCo_zO_(2)(1-y-z≥0.6)are promising candidates for cathode materials,but their practical applications are hindered by high-voltage instability and fast capacity fading.Using density functional theory calculations,we demonstrate that Na-,F-doping,and Na/F-co-doping can stabilize the structure and result into a higher open circuit voltage than pristine LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)(NMC622)during the charging process,which may attain greater discharge capacity.F doping may inhibit the diffusion of Li ions at the beginning and end of charging;Na doping may improve Li ion diffusion due to the increase in Li layer spacing,consistent with prior experiments.Na/F-codoping into NMC622 promotes rate performance and reduces irreversible phase transitions for two reasons:(i)a synergistic effect between Na and F can effectively restrain the Ni/Li mixing and then enhances the mobility of Li ions and(ii)Ni/Li mixing hinders the Ni ions to migrate into Li layers and thus,stabilizes the structure.This study proposes that a layer cathode material with high electrochemical performance can be achieved via rational dopant modification,which is a promising strategy for designing efficient Li ion batteries.

Structure and Electrochemical Properties of LiMn_2O_(4-x)F_x

LiMn 2O 4-x F x prepared by the sol gel method has a perfect crystal formation .The crystal particle size of the material was medium and distributed uniformly. The substitution of F for O increased the specific capacity of the material at the cost of the cycleability .The explanation of this results is that the F decreases the valence of Mn,that is,more Mn 3+ and less Mn 4+ exist in the material.The increase of Mn 3+ will improve the initial specific capacity and Mn 3+ is the original reason for Jahn Teller effect that caused the poor cycleability of the cathode material by the micro distortion of the crystal structure. In addition, the expanded measurement of the crystal lattice is also the reason for the poor cycleability.Therefore,the results of F substitution and cation substitution are opposite.If the two methods are combined,they can compensate the inability each other and the satisfactory results may be obtained.

Doping of group IVB elements for nickel-rich cobalt-free cathodes

Hetero-element doping is a promising strategy to improve the cycling stability of nickel-rich cobalt-free cathodes for the next-generation high energy-density Li ion batteries.To make doping effective,it is important to understand the mechanism of how the dopants regulate the electronic band,lattice parameter adjusting,or hetero-phase formation to achieve high stability.In this study,we investigate LiNi_(0.9)Mn_(0.1)O_(2)cathodes doped with IVB grouping elements via multiple characterization techniques.By utilizing in situ XRD and TEM methods,we found that the stronger Ti-O bond effectively improves the cathode stability via a dual protection mechanism.Specifically,the bulk lattice of cathode is wellpreserved during cycling as a result of the suppressed H_(2)-H_(3)phase transition,while a in situ formed Ti-rich surface layer can prevent continuous surface degradation.As a result,the 5%Ti doped LiNi_(0.9)Mn_(0.1)O_(2)cathode exhibits a high capacity retention of 96%after 100 cycles.Whereas,despite IVB group elements Zr and Hf have stronger bonding energy with oxygen,their larger ionic radii actually impede their diffusion into the cathode,thereby they can not improve the cycling stability.Our findings uncover the functional origin of doped elements with their dynamic modification on cathode structure,providing mechanistic insights into the design of nickel-rich cobalt-free cathodes.

SnO_2 hollow nanospheres assembled by single layer nanocrystals as anode material for high performance Li ion batteries

SnO2 hollow nanospheres were successfully synthesized via a facile one-step solvothermal method.Characterizations show that the as-prepared SnO2 spheres are of hollow structure with a diameter at around 50 nm,and especially,the shell of the spheres is assembled by single layer SnO2 nanocrystals.The surface area of the material reaches up to 202.5 m^2/g.As an anode material for Li ion batteries,the sample exhibited improved electrochemical performance compared with commercial SnO2 particles.After cycled at high current rate of 0.5 C,1 C and 0.5 C for 20 cycles,respectively,the electrode can maintain a capacity of 509 mAh/g.The suitable shell thickness/diameter ratio endows the good structural stability of the material during cycling,which promises the excellent cycling performance of the electrode.The large surface area and the ultra thin shell ensure the high rate performance of the material.

Recent progress of computational investigation on anode materials in Li ion batteries

Computations have been widely used to explore new Li ion battery materials because of its remarkable advantages. In this review, we summarize the recent progress on computational investigation on anode materials in Li ion batteries. By introducing the computational studies on Li storage capability in carbon nanotubes, graphene, alloys and oxides, we reveal that computations have successfully addressed many fundamental problems and are powerful tools to understand and design new anode materials for Li ion batteries.

Ultrathin MoS2 with expanded interlayers supported on hierarchical polypyrrole-derived amorphous N-doped carbon tubular structures for high-performance Li/Na-ion

Layered molybdenum disulfide （MoS2） has received much attention as one of the most promising energy-storage and conversion materials for Li/Na ion batteries. Here, a simple and effective approach is proposed for the rational design and preparation of hierarchical three-d imensional （3D） amorphous N-doped carbon nanotube@MoS2 nanosheets （3D-ANCNT@MoS2） via a simple hydrothermal method, followed by an annealing process. With such a unique nanoarchitecture, ultrathin MoS2 nanosheets grown on the external surfaces of polypyrrole-derived ANCNTs are assembled to form a hierarchical 3D nanoarchitecture, where the adopted ANCNTs serve not only as the template and continuous conductive matrix, but can also prevent MoS2 from aggregating and restacking, and help to buffer the volumetric expansion of MoS2 during cycling. More importantly, when evaluated as an anode material for lithium-ion batteries, the 3D-ANCNT@MoS2 composite exhibits excellent cycling stability, superior rate performance, and reversible specific capacity as high as 893.4 mAh·g^-1 at 0.2 A·g^-1 after 200 cycles in a half battery, and 669.4 mAh·g^-1 at 0.2 A·g^-1 after 100 cycles in the 3D-ANCNT@Mo2//LiCoO2 full battery. With respect to sodium-ion batteries, the outstanding reversible capacity, excellent rate behavior, and good cycling performance of 3D-ANCNT@MoS2 composites are also achieved.

The electrochemical performance of super P carbon black in reversible Li/Na ion uptake

Super P carbon black (SPCB) has been widely used as a conducting additive in Li/Na ion batteries to improve the electronic conductivity. However, there has not yet been a comprehensive study on its structure and electrochemical properties for Li/Na ion uptake, though it is important to characterize its contribution in any study of active materials that uses this additive in non-negligible amounts. In this article the structure of SPCB has been characterized and a comprehensive study on the electrochemical Li/Na ion uptake capability and reaction mechanisms are reported. SPCB exhibits a considerable lithiation capacity (up to 310 mAh g^(–1)) from the Li ion intercalation in the graphite structure. Sodiation in SPCB undergoes two stages: Na ion intercalation into the layers between the graphene sheets and the Na plating in the pores between the nano-graphitic domains, and a sodiation capacity up to 145 mAh g^(–1) has been achieved. Moreover, the influence of the type and content of binders on the lithiation and sodiation properties has been investigated. The cycling stability is much enhanced with sodium carboxymethyl cellulose (NaCMC) binder in the electrode and fluoroethylene carbonate (FEC) in the electrolyte; and a higher content of binder improves the Coulombic efficiency during dis-/charge.

First-principles insight into the entanglements between superionic diffusion and Li/Al antisite in Al-doped Li1+xAlxGe2–x(PO4)3(LAGP)

As an ion conductor, the Al-doped Li1+xAlxGe2-x(PO4)3(LAGP) demonstrates the superionic Li diffusion behavior, however,without the convinced verifications. In this context, the density functional theory(DFT) calculations are employed to clarify the structural origin of the fast Li ion migration kinetics in LAGP solid electrolytes. The calculated results show that doping of Al leads to an emerging high-energy 36 f Li site, which plays an important role in promoting the Li diffusion and can largely lower the Li ion diffusion energy barrier. Moreover, the Li/Al antisite defect is investigated firstly, with which the Li ions are excited to occupy a relatively high energy site in LAGP. The obvious local structural distortion by Li/Al antisite results in the coordination change upon Li diffusion(lattice field distortion), which facilitates the Li diffusion significantly and is probably the main reason to account for the superionic diffusion phenomenon. Therefore, the occupation of Li at high-energy sites should be an effective method to establish the fast Li diffusion, which implies a rewarding avenue to build better Li-ion batteries.

Recent Advances in Atomic-scale Storage Mechanism Studies of Two-dimensional Nanomaterials for Rechargeable Batteries Beyond Li-ion

Developing new types of rechargeable batteries with high energy densities and low cost have received in creasing attentions,aiming to reduce the dependence on high-priced lithium.Bevond Li-ion batteries,the potential alternatives including Na-ion batteries,Li-S batteries and Li-air batteries have been investigated recently,which are required to be viable for commercial applications.From this point of view,to understand the electrochemical reaction mechanisms and kinetics of these batteries has become the key challenge to make breakthroughs in the field of new energy storage.In this review,we present a critical overview of the two dimensional nanomaterials-based batteries(except Li-ion-based batteries)that could meet such demonds.To develop new energy storage devices with more promising performances,the microstructure evolution and atomic scale storage mechanism of these batteries are comprehensively summarized.In addition,the major challenges and opportunities of advanced characterization techniques are finally discussed.We do hope that this review will give the readers a clear and profound understanding of the electrochemical reaction mechanisms and kinetics of the as-discussed batteries.thus effectively contributing to the smart design of future-generation energy storage devices.

Covalent interfacial coupling of vanadium nitride with nitrogen-rich carbon textile boosting its lithium storage performance as binder-free anode

Eliminating the usage of metal current collectors and binders in traditional battery electrode configuration is an effective strategy to significantly improve the capacities of lithium ion batteries (LIBs). Herein, we demonstrate the construction of porous vanadium nitride (VN) nanosheet network in situ grown on nitrogen-rich (N-rich) carbon textile (N-C@P-VN) as lightweight and binder-free anode for LIBs. The N-rich carbon textile is used both as the current collector and host to store Li^(+), thus improving the specific capacities of binder-free VN anode and meanwhile reducing the inert mass of the whole cell. Moreover, the open spaces in carbon textile and vertically aligned pores in VN nanosheet network can not only provide an expressway for Li+ and e− transport, but also afford more active sites. As a result, the binder-free N-C@P-VN anode maintains a specific capacity of 1,040 mAh·g^(−1) (or an areal capacity of 2.6 mAh·cm^(−2)) after 100 cycles at 0.1 mA·cm^(−2) in half cell. Moreover, in an assembled N-C@P-VN//LiFePO4 full cell, it exhibits an areal capacity of 1.7 mAh·cm^(−2) after 300 cycles at 0.1 C. The synergistic strategy of N-C substrate and porous VN network could be applied to guide rational design of similar N-C@nitride or sulfide hybrid systems with corresponding sulfur-doped carbon textile as the substrate.