Electrode Materials For Li-ion Batteries Research Articles

Electrochemical Performance of Nitrogen-Doped TiO2 Nanotubes as Electrode Material for Supercapacitor and Li-Ion Battery.

Electrochemical anodized titanium dioxide (TiO2) nanotubes are of immense significance as electrochemical energy storage devices owing to their fast electron transfer by reducing the diffusion path and paving way to fabricating binder-free and carbon-free electrodes. Besides these advantages, when nitrogen is doped into its lattice, doubles its electrochemical activity due to enhanced charge transfer induced by oxygen vacancy. Herein, we synthesized nitrogen-doped TiO2 (N-TiO2) and studied its electrochemical performances in supercapacitor and as anode for a lithium-ion battery (LIB). Nitrogen doping into TiO2 was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performance of N-TiO2 nanotubes was outstanding with a specific capacitance of 835 µF cm−2 at 100 mV s−1 scan rate as a supercapacitor electrode, and it delivered an areal discharge capacity of 975 µA h cm−2 as an anode material for LIB which is far superior to bare TiO2 nanotubes (505 µF cm−2 and 86 µA h cm−2, respectively). This tailor-made nitrogen-doped nanostructured electrode offers great promise as next-generation energy storage electrode material.

Binary cobalt-iron oxides magnetic nanocomposites embedded porous carbon lawn with inherent [sbnd]N doping as promising electrode material for supercapacitors and Li-ion batteries

The next generation energy demands require to address the alternative energy resources and as well the energy storage technologies. The electrochemical supercapacitors and lithium ion batteries prove to be attractive devices to overcome the faced community challenges. There is a need to develop an innovative material owing high surface area with higher electrical & ionic conductivity and low diffusion distance for electrochemical energy storage electrodes. To this end, a unique electrode material is developed with these admirable properties for energy storage applications towards both directions such as, electrochemical supercapacitors and an anode material for lithium ion batteries. Nanostructured materials based on metallic binary oxides of cobalt and iron embedded in porous carbon lawn with inherent nitrogen doping are synthesized by dry-chemistry calcined process. The success of synthesis is later proved by materials characterizations. The magnetic nature of present electrode material with correlation of crystallite and morphological analysis revealed the signs of their excellence in energy storage behaviour. The testing of electrode material for electrochemical supercapacitors and lithium ion batteries depicted enhance performance with durable and long-run recycled capabilities.

Chemical Transformations in Li-Ion Battery Electrode Materials by Carbothermic Reduction

The effects of pyrolysis on the composition of the battery cell materials as a function of treatment time and temperature were investigated. Waste of Li-ion batteries was pyrolyzed in a nitrogen at...

Mo3Nb2O14: A high-rate intercalation electrode material for Li-ion batteries with liquid and garnet based hybrid solid electrolytes

Herein we report Mo3Nb2O14 possessing a layered open framework structure as potential candidate for Li-ion batteries with conventional liquid electrolyte as well as with a hybrid solid electrolyte (garnet oxide-ionic liquid). The material delivers a discharge capacity of 329 mA h g−1 at 1C rate in a liquid electrolyte-based cell, corresponding to insertion of 8.5 Li. Moreover, it exhibits excellent rate capability (up to 50C rate) and good capacity retention. Considering the high capacity and high rate capabilities of the material we further investigate its performance in presence of garnet based quasi (hybrid) solid electrolyte owing to the attractive features of solid-state batteries. When hybrid solid electrolyte is used, the electrode material delivers an initial discharge capacity of 206 mA h g−1 at high current rate of 1C and exhibits excellent capacity retention of 165 mA h g−1 (80%) at the end of 100 charge-discharge cycles. The ultra-fast Li+ insertion/extraction can be attributed to the three-dimensional channel structure of the Mo3Nb2O14 which allows facile lithium ion transport. Hence, this work supports the idea of revisiting layered type metal oxides as electrodes for developing high energy density and safe lithium ion batteries.

Li4V2Mn(PO4)4-stablized Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials for lithium ion batteries

Li-rich Mn-based cathode materials are regarded as promising cathode materials for Li-ion batteries (LIBs) owing to their high electrochemical capacity and low cost. However, residual Li compounds on the surface and dissolution of metal ions cause severe degradation of the electrochemical performance, thereby hindering their practical applications. Li4V2Mn(PO4)4 is a composite cathode material with three-dimensional Li-ion diffusion channels and a stable structure at high operating voltages (>4.5 V). Herein, we modify the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with Li4V2Mn(PO4)4. The Li4V2Mn(PO4)4 coating layer can not only reduce the content of residual Li compounds on the surface but also restrain the dissolution of transition metals. Theoretical calculations illustrate that Li4V2Mn(PO4)4 reduces the Li-ion diffusion energy barrier and provides efficient diffusion pathways. Li[Li0.2Mn0.54Ni0.13Co0.13]O2@Li4V2Mn(PO4)4 compounds deliver a discharge capacity of 300 mAh g−1 with a high initial coulombic efficiency (84.2%) and an excellent cycling stability (capacity retention of 78.1% after 200 cycles at 1C). Hence, the proposed modification strategy of phosphate-based materials could shed light on the structural design of surface-sensitive electrode materials for LIBs.

High Performance Silicon-Carbon Composite Powders Using Recycled Silicon from Solar Cells As Anode Material for Li-Ion Batteries

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim of this work is the development of silicon recovered during the dismantling of solar panels as negative electrode material for Li-ion batteries. The principal technological challenge associated with the use of silicon in this type of application is to control the volume expansion during charge/discharge cycles. This drawback can be avoided through the formation of Silicon/carbon composites in which the size of the silicon particles and their dispersion is controlled [1–4]. In this research, we develop a carbon matrix system using a conducting carbon source and a reduced carbon from organic source that will incorporate the silicon particles. The recycled Si wafers are leached to remove Al and Ag. The a grinding step is performed to obtain Si particles of <200nm and then a mixed suspension of Si, an organic carbon source and the conductive carbon source is prepared. This mixture is spray-dried followed by heat treatment to generate a carbon matrix that incorporates the silicon particles The morphology of the composite materials is analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Electrochemical performance of Si/C composites is characterized by Galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy (EIS).

Hierarchically porous structured carbon derived from peanut shell as an enhanced high rate anode for lithium ion batteries

Abstract In recent years, biomass-derived carbon in the energy storage system has attracted tremendous attention due to low cost, scalable, meso/microporous nature. Here we describe the synthesis of peanut shell activated carbon (PSAC) by scalable and low power microwave method using KOH as an activation agent. The structural, surface area, porosity, and morphological properties of PSAC are characterized by different techniques such as XRD, Raman, XPS, N2 adsorption/desorption, FESEM and HRTEM analysis. FESEM and HRTEM confirm the highly distributed interconnected hierarchically porous structure with uniform nanopores over the surface and the achieved high surface area of PSAC is 525.685 m2 g−1. Furthermore, the PSAC is explored as an anode electrode material for Li-ion batteries (LIBs). The obtained reversible capacity is 680 mAh g−1 at 0.05 C rate after 100 cycles. The achieved rate capability, high reversible capacity and stability of the PSAC electrode mainly depend on its excellent conductivity, high surface area, rich porosity, more edges defects sites and hierarchically porous structured morphology.

Scanning Spreading Resistance Microscopy: A Promising Tool for Probing the Reaction Interface of Li-Ion Battery Materials.

Imaging of the Li-insertion/extraction [Li-in/out] interface of the electrode materials of Li-ion batteries is essential to reveal their bulk mechanism of electrochemical reaction and phase behavior in the crystal. Generally, the material properties significantly change at this interface. Therefore, direct probing of the changing properties is a promising approach to reliably investigate the Li-in/out interface in the bulk crystal of electrode materials. In this study, we investigated the change in electron conductivity of rutile-TiO2 with Li-insertion and extraction, as a model for the electrochemical interface of a bulk crystal of electrode material. In addition, we probed the interface using logarithm contact resistance [log R (Ω)] imaging via scanning spreading resistance microscopy (SSRM). A distinct Li-in/out interface on the rutile-TiO2(001) wafer was observed using this technique. The imaging resolution of this region was estimated to be approximately 40-50 nm in SSRM images, which was two to three times higher than the resolution of the topographic image (100-150 nm), which was restricted to the curvature radius of the SSRM probe tip. A high spatial resolution was obtained via SSRM imaging because this approach is not influenced by the geometric effects of the surface. This result demonstrated the potential of SSRM imaging for the study of the Li-in/out interface.

Vacancy-mediated lithium adsorption and diffusion on MXene

Abstract Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes), promising electrode materials for Li-ion batteries (LIBs), have recently been confirmed the formation of vacancies during etching process. However, the specific influence of vacancies on the performance of MXene-based LIBs and the corresponding mechanism still remain open issues. Herein, we highlighted that compared with other well-studied 2D materials (such as graphene, 2D MoS2), MXene are more likely to contain vacancies with defect formation energies as low as 0.96 eV. The difference of vacancy formation energy for MXenes mainly originates from the variation of M-X bonding strengths. Furthermore, the vacancy defect will enhance the adsorption of Li in the region near the defect through acting as a potential trap, which may cause the first cycle irreversibility for lithiation/delithiation process in Mo2C MXene LIBs. Nevertheless, Li tends to migrate on defect-free surface of Mo2C MXene with energy barrier of 0.096–0.115 eV and thus this potential trap has a minor influence on the charge-discharge rate of Mo2C MXene LIBs. We believe that our findings provide not only some insights into the recent experimental results but also guidance for the preparation and practical application of MXene in LIBs.

Novel 3D flower-like micro/nano-structure FeS/N-doped-C composites as advanced cathodes with high lithium storage performances

Due to their merits of high capacity, abundant resources and environmental benignity, Fe monosulfides are considered as attractive electrode materials for Li-ion batteries. However, inferior cyclability and rate performances resulted from inherent low conductivity limit their applications. Herein, we present novel 3D flower-like micro/nano-structure FeS/N-doped-C composites which are directly synthesized from low-cost organosulfur compounds through facile precipitation and subsequent calcination and for the first time applied as cathodes for lithium storage. The FeS nanoparticles are coated by highly conductive N-doped-C shells. Such a confinement of coating microstructures, especially outer N-doped-C, is highly beneficial for the conversion reactions (FeS+2Li++2e−↔Fe + Li2S), and could strengthen conductivity and simultaneously better protect FeS from electrolyte corrosions, ensuring stable conductive frameworks. Also, such N-doped-C anchor FeS, Fe, and Li2S effectively, as confirmed by density functional theory calculations. Thus, the FeS/N-doped-C cathodes exhibit remarkable cycling stability (621 mAh g−1 at 200th cycle at 1C, with a decay of 0.07%/cycle), and high rate performances (600 mAh g−1 even at 10C), delivering higher energy density than commercial LiCoO2 cathodes. This work discloses a novel and paramount route to exploit transition metal sulfides for lithium storage and helps us further understand the key role of N-doping in electrochemical energy storage.

Atomistic Modeling of Various Doped Mg2NiH4 as Conversion Electrode Materials for Lithium Storage

In this work, we have compared the potential applications of nine different elements doped Mg2NiH4 as conversion-type electrode materials in Li-ion batteries by means of state-of-the-art Density functional theory calculations. The electrochemical properties, such as specific capacity, volume change and average voltage, as well as the atomic and electronic structures of different doped systems have been investigated. The Na doping can improve the electrochemical capacity of the pristine material. Si and Ti doping can reduce the band gap and benefit the electronic conductivity of electrode materials. All of the nine doping elements can help to reduce the average voltage of negative electrodes and lead to reasonable volume changes. According to the computational screening, the Na, Si and Ti doping elements are thought to be promising to enhance the comprehensive properties of pure material. This theoretical study is proposed to encourage and expedite the development of metal-hydrides based lithium-storage materials.

Review of Recent Development of In Situ/Operando Characterization Techniques for Lithium Battery Research.

The increasing demands of energy storage require the significant improvement of current Li-ion battery electrode materials and the development of advanced electrode materials. Thus, it is necessary to gain an in-depth understanding of the reaction processes, degradation mechanism, and thermal decomposition mechanisms under realistic operation conditions. This understanding can be obtained by in situ/operando characterization techniques, which provide information on the structure evolution, redox mechanism, solid-electrolyte interphase (SEI) formation, side reactions, and Li-ion transport properties under operating conditions. Here, the recent developments in the in situ/operando techniques employed for the investigation of the structural stability, dynamic properties, chemical environment changes, and morphological evolution are described and summarized. The experimental approaches reviewed here include X-ray, electron, neutron, optical, and scanning probes. The experimental methods and operating principles, especially the in situ cell designs, are described in detail. Representative studies of the in situ/operando techniques are summarized, and finally the major current challenges and future opportunities are discussed. Several important battery challenges are likely to benefit from these in situ/operando techniques, including the inhomogeneous reactions of high-energy-density cathodes, the development of safe and reversible Li metal plating, and the development of stable SEI.

Anisotropic Compositional Expansion and Chemical Potential of Lithiated SiO2 Electrodes: Multiscale Mechanical Analysis.

The use of high-capacity electrode materials (i.e., Si) in Li-ion batteries is hindered by their mechanical degradation. Thus, oxides (i.e., SiO2) are commonly used to obtain high expected capacities and long-term cycle performances. Despite extensive studies of the electrochemical-mechanical behaviors of high-capacity energy storage materials, the mechanical behaviors of amorphous SiO2 during electrochemical reaction remain largely unknown. Here, we systematically investigate the stress evolution, electronic structure, and mechanical deformation of lithiated SiO2 through first-principles computation and the finite element method. The structural and thermodynamic role of O in the amorphous Li-O-Si system is reported and compared with that in Si. Strong Si-O bonds in SiO2 show high mechanical strength and brittle behavior, but as Li is inserted, the Li-rich SiO2 phases become mechanically softened. The relaxation kinetics of SiO2, inducing deviatoric inelastic strains under mechanical constraints, is also compared with that of Si. The finite element model including the kinetic model for anisotropic expansion demonstrates that the long-term cycling stability of core-shell Si-SiO2 nanoparticles mainly arises from the reaction kinetics and high mechanical strength of SiO2. These results provide fundamental insights into the chemomechanical behavior of SiO2 for practical use.

Facile synthesis of the 3D framework Si@N-doped C/Reduced graphene oxide composite by polymer network method for highly stable lithium storage

Silicon (Si) has received sustained attention as an anode electrode material for Li-ion batteries (LIBs). However, Si is extremely limited by rapid capacity decay due to considerable changes in the structure during lithiation/delithiation. A 3D framework Si@N-doped C/reduced graphene oxide (Si@NC/rGO) composite has been facilely prepared by a novel polymer network method by using GO, Si nanoparticles, polymer monomers (acrylic amide), and networking agents (N,N′-methylene bisacrylamide) as the raw materials, followed by carbonization under an Ar atmosphere. After the crosslinking reaction, approximately 30 nm Si nanoparticles are embedded in the 3D NC/rGO framework. The Si@NC/rGO composite has a large reversible specific capacity, good cycle stability, and excellent rate performance as an anode electrode material for LIBs. The specific capacity is maintained at 867.4 and 479.1 mA h g−1 at 0.1 and 2 A g−1 after the 200 cycles, respectively. The capacity is three to fourfold higher than that of commercial graphite anode materials. The excellent electrical properties are mainly ascribed to the collaboration of the C framework and the high electrical conductivity of graphene and N doping. The Si@NC/rGO composite shows growth potential as anode electrode materials for LIBs.

The Effect of Metal-Oxide Coating on the Electrochemical Performance of Carbon-Nanofibers Anodes in Lithium-ion Batteries

With the invention of the electric cars and the exponential growth in portable electronics over the last decade, energy storage systems that can supply and store more power are of utmost importance. Li-ion batteries (LIBs) entered the market less than a decade ago to keep up with market demands and have since become the most efficient way to store energy due to their reversible nature. Graphite is currently the most widely used material in (LIB) anodes due to its long cycle life and low manufacturing cost, its main drawback being its low theoretical capacity of 372 mAg-1. Metal oxides have been of interest as electrode materials for (LIBs) due to their inherently high theoretical capacities and low cost. However, the main drawback of metal oxide-based anodes includes high volume expansion, particle agglomeration, and dendrite formation. Developments in composites and novel micro/nano-structures that withstand large temperature ranges and maintain structural stability have attracted interest for their use as electrode materials in LIBs. Here, we explore the performance of Iron Oxide (Fe2O3), Tin Oxide (SnO2), Zinc Oxide (ZnO), and Cobalt Oxide (Co3O4), coated on carbon fibers as hosts for lithium ion insertion/de-insertion during charge/discharge process. The synthesis and design of Fe2O3/Carbon and SnO2/C composite fibers were reiliazed by the centrifugal spinning of metal-oxides precursors in polyacrylonitrile (PAN)/ dimethylformamide (DMF) solutions and followed by calcination at 600 °C in an inert gas. The characterization of Fe2O3/C, ZnO/C, Co3O4/C and SnO2/C composite fibers was conducted using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and energy dispersive X-ray analysis (EDAX). The pre-coated carbon fibers with metal-oxide nanoparticle precursors showed improved electrochemical performance compared to the pristine composite carbon-fibers anodes.

Electrochemical Properties of Amorphous Silica As an Anode Material for Li-Ion Batteries

After conquering the scene of portable electronics (i.e. mobile phones and laptop computers) since their introduction to the marketplace in 1991, lithium ion batteries (LIBs) are set to further enable wide-scale deployment of electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, a series of challenges still remain with respect to a number of important factors, such as the operational safety of LIBs, raw material supply, cost, recycling and environmental aspects. In order to fulfill future demands for large-scale applications, significant improvements and deeper understanding are required in these areas. As of today, graphite is the anode (negative electrode) material primarily used in commercial LIBs, mainly due to its charge-discharge capacity retention capability and an attractively low, flat operational voltage as well as a manageable voltage hysteresis upon (de)intercalation which altogether maximizes both the energy density and energy efficiency of the cell in which it is employed. However, recent projections regarding the future cost and availability of graphite have prompted researchers to explore alternatives in the context of cheap and sustainable materials for electrochemical energy storage. Silica (SiO2) is currently being explored as a possible alternative candidate material in this context. SiO2 was long disregarded as a potential electrode material due to its apparent electrochemical inactivity. However, studies in recent years have sparked renewed interest in SiO2 after it was demonstrated that modified nano-SiO2 may indeed be electrochemically active. SiO2 is a conversion-type anode material which irreverisbly produces various silicates (e.g. Li4SiO4 and Li2Si2O5) as well as elemental Si during electrochemical lithiation. Although the precise reaction mechanism is still a topic for debate, it is believed that the by-products formed in-situ during electrochemical cycling can mechanically buffer the stress and strain associated with continued (de)lithiation of Si and thereby extending the cycle life of the electrode material. The present study systematically investigates the electrochemical properties of amorphous SiO2 as a negative electrode material for Li-ion batteries. The SiO2 materials in question include spherical nano-particulate SiO2 recovered as an industrial by-product or naturally nano-sized 3D-architectured SiO2 extracted from a renewable resource of biological origin – the main motivation here clearly being the study of dirt-cheap, highly abundant materials and the possible prospect of their implementation in electrochemical storage devices. By virtue of its electronically insulating properties, SiO2 needs to be carefully engineered in order to activate the material. Important factors in this regard include control of particle morphology, surface area and porosity as well as enhancement of electronic conductivity. Consequently, various carbon sources (i.e. glucose, sucrose, starch) have been utilized in varying amounts in order to achieve a conductive carbon coating on the SiO2 particles via high-temperature pyrolysis (i.e. carbonization), ultimately yielding SiO2/C composites with improved electrochemical properties in relation to bare SiO2. Here, these variations in carbon precursor, carbon content and coating thickness etc. are directly related to the electrochemical activity of the different SiO2 materials. These aspects are additionally highlighted by means of a series of advanced characterization techniques. The influence of particle size and morphology is further made possible by the direct comparison of spherical SiO2 nanoparticles to the intricate 3D-architecture of the SiO2 derived from harvested biomass. Preliminary results indicate it appears possible to electrochemically activate (i.e. displace Si followed by its electrochemical lithiation at low voltages vs. Li+/Li) the latter via careful considerations in terms of electrode design and electrochemical testing procedures which results in gravimetric capacities of >1000 mAh g-1 at an average (de)lithiation voltage in the range of 0.2-0.4 V vs. Li+/Li. By comparison, the spherical nanoparticles exhibit significantly lower electrochemical activity, i.e. a reversible gravimetric capacity of 300-400 mAhg-1 with highly sloping voltage profiles in an electrochemical cycling windowof ~0-2 V vs. Li+/Li.

Ceramic Synthesis of Disordered Lithium Rich Oxyfluoride and the Impact of Their Defects in Electrochemical Performances

We recently focused our interest on oxyfluorides as positive electrode materials for Li-ion batteries because they were proved to exhibit higher operating voltages vs. Li than oxides due to an increased ionicity of the M–(O,F) bonds. As an example, Li2VO2F exhibits a potential of 2.7 V vs. Li+/Li which is 200 mV higher than for Li2VO3 [1-3]. Interestingly, lithium-rich oxyfluorides display high theoretical capacity (463 mA.h/g) much higher than the well-known LiCoO2 (274mA.h/g) or LiFePO4 (170 mA.h/g). Our attention was also turn to other analogous phases of Li2VO2F such as Li2FeO2F and Li2TiO2F. Li2MIIIO2F (with M = V, Ti and Fe) were synthesized by high energetically ball milling. The obtained materials prove to be metastable (highly non-equilibrium state) with compositional inhomogeneity. Moreover, the reactants are not well mixed on the atomic scale and can produce amorphous phase. To the best of our knowledge ceramic synthesis of Li2MO2F have never been reported. Yet, the ceramic route performed at high temperature can result in more crystalline and stable phase. Recently, we have shown that the ceramic synthesis of Li2MIIIO2F is possible [4-5]. The oxyfluorides obtained in this work by ceramic synthesis crystalize in FCC (Space group N° 225). The structure can be described as a layered phase, in which lithium and the transition metal cations segregate into layers in the cubic (111) direction (Figure 1). The process by which energy is stored in these materials constitutes a change in the design of battery materials and involves unexpected and surprisingly effective mechanisms: instead of storing lithium ions by intercalation into a stable host, lithium ions are populating and vacating lattice sites of the material itself [1,2]. This new principle leads to unprecedented higher energy and higher power density compared to other battery materials. As results, large amounts of energy and power can be stored and/or supplied from small spaces. Moreover, the presence of defect (intrinsic and/or extrinsic schottky defects) plays and important role in the electrochemical performances of lithium rich oxyfluoride. Futhermore, the study of Li2MIIIO2F materials was followed up by various techniques among which X-rays absorptions spectroscopy, NMR, Mössbauer spectroscopy and neutron diffraction.

Effect of nitrogen and sulfur co-doping on the performance of electrochemical hydrogen storage of graphene

Abstract In recent decades, finding a solution to replace metal catalysts with inexpensive and available elements has been investigated extensively. Carbon nanomaterials doped with heteroatom such as (N, B and S) which do not have any metal content can provide sustainable materials with a remarkable electrocatalytic activity that can compete with their metal counterparts. Doped graphene has been considered as an electrode material for oxygen reduction reaction, supercapacitor and Li-ion batteries. In this present account, co-doped graphene with nitrogen and sulfur was studied in order to investigate their electrochemical hydrogen storage performance. The dual doped sample was prepared via a simple hydrothermal method, using thiourea as a nitrogen and sulfur source. The nitrogen and sulfur co-doped graphene (NSG) showed excellent electrical conductivity and electrochemical performance compared with the nitrogen doped graphene (NG) and graphene oxide (GO). Doping graphene with foreign atoms is a method to create a semiconducting gap in it and can act as an n-type semiconductor, therefore the electrochemical performance is remarkable when used as an electrode. According to the results by increasing the electrical conductivity of graphene, the storage capacity of hydrogen was increased. The discharge capacity of GO after 20 cycles was increased from 653 mAh/g to 1663 mAh/g (5.88 wt% hydrogen) and 2418 mAh/g (8.55 wt% hydrogen) in single doped graphene (NG) and co-doped graphene (NSG), respectively. The prepared samples were characterized via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmet-Teller analysis (BET), vibration sample magnetometer (VSM) and infrared spectrum (FT-IR).

Synthesis of β-FeOOH nanorods adhered to pine-biomass carbon as a low-cost anode material for Li-ion batteries

Looking for low-cost materials for high energy storage has been a hot topic in recent years. Iron materials and biomass carbon, which both have the properties of good natural abundance and low cost, are very promising materials for large-scale use. Here, β-FeOOH nanorods adhered to pine-biomass carbon (BC/FeOOH) were synthesized by a facile precipitation method. TEM and SEM results show that β-FeOOH nanorods grow in the inner pores and are inserted into the surface pores. We analyzed the effects of the amount of BC in the composite on the electrode performance in Li-ion battery cells. The as-prepared composites showed excellent electrochemical performance as the anode electrode material in Li-ion batteries, which maintained a current density of 650 mAh g−1 at 1 C (1 C = 1000 mA g−1) and above 660 mAh g−1 at 0.2 C after 450 cycles.

Phase Transformation Behavior and Stability of LiNiO2 Cathode Material for Li-Ion Batteries Obtained from In Situ Gas Analysis and Operando X-Ray Diffraction.

Ni-rich layered oxide cathode materials, in particular the end member LiNiO2 , suffer from drawbacks such as high surface reactivity and severe structural changes during de-/lithiation, leading to accelerated degradation and limiting practical implementation of these otherwise highly promising electrode materials in Li-ion batteries. Among all known phase transformations occurring in LiNiO2 , the one from the H2 phase to the H3 phase at high state of charge is believed to have the most detrimental impact on the material's stability. In this work, the multistep phase transformation process and associated effects are analyzed by galvanostatic cycling, operando X-ray diffraction, and in situ pressure and gas analysis. The combined results provide thorough insights into the structural changes and how they affect the stability of LiNiO2 . During the H2-H3 transformation, the most significant change occurs in the c-lattice parameter, resulting in large mechanical stress in LiNiO2 . As for electrochemical stability, it suffers strongly in the H3 region. Oxygen evolution is observed not only during charge but also during discharge and found to be correlated with the presence of the H2 and H3 phases. Taken together, the experimental data improve the understanding of the degradation processes and the inherent instability of LiNiO2 in Li-ion cells when operated above around 75 % state of charge.