High Capacity Li-ion Batteries Research Articles

Chemical Vapor Deposition-Assisted Fabrication of Self-Assembled Co/MnO@C Composite Nanofibers as Advanced Anode Materials for High-Capacity Li-Ion Batteries.

Constructing the nanostructure of transition metal oxides for high energy density lithium-ion batteries has been widely studied recently. Prompted by the idea that the transition metal can serve as a catalyzer influence on the reversibility of solid-electrolyte interphase films, Co/MnO@C composite nanofibers were designed by electrospinning and chemical vapor deposition methods. The Co/MnO@C electrode showed superior electrochemical performance with a large capacity increase for the first 400 cycles and a high rate performance of 1345 mA h g-1 at 1000 mA g-1. There was no obvious decay of capacity over the whole 1000 cycles, demonstrating the excellent cycling stability of the samples. The new design and synthesis of the anodic materials may offer a prototype for high-performance and strong-stability batteries.

Zn–Mn-ptcda derived two-dimensional leaf-like Zn0·697Mn0·303Se/C composites as anode materials for high-capacity Li-ion batteries

As the most widely used energy storage device today, lithium-ion batteries (LIBs) will determine the convenience and durability of people's future energy life to a certain extent. At present, there are many and mature researches on cathode materials for LIBs, so it is crucial to seek a high-performance anode material. In recent years, due to considerable theoretical capacity, abundant raw material reserves and unique physicochemical properties, Zn and Mn selenium compounds have become research hotspots for LIBs anode materials. In this work, a new MOF material Zn–Mn-ptcda was synthesized by a simple hydrothermal reaction. Using Zn–Mn-ptcda as the precursor, two-dimensional (2D) elliptical leaf-shaped Zn0·697Mn0·303Se/C composites were synthesized by direct selenization. Zn0.697Mn0.303Se/C has a large specific surface area of 213.9 m2 g−1, belongs to the mesoporous structure, and possesses excellent lithium storage performance, especially the rate performance. It has a reversible capacity of 1005.14 mAh g−1 after 110 cycles at a current density of 100 mA g−1. After 1000 cycles at a high current density of 1 A g−1, it still maintains a good capacity of 653.79 mAh g−1.

Enabling Facile Anionic Kinetics through Cationic Redox Mediator in Li-Rich Layered Cathodes

Anionic oxygen redox has aroused great interest in developing high-capacity Li-ion battery cathode materials. The fundamental understanding of this concept, compared to cationic redox, has promoted...

Si nanoparticles confined within a conductive 2D porous Cu-based metal–organic framework (Cu3(HITP)2) as potential anodes for high-capacity Li-ion batteries

The utility of metal–organic frameworks (MOFs) as active agents in electronic appliances is beneficial owing to their outstanding properties, particularly their high porosity, high surface area, and unique chemical stability. Herein, we report the in-situ growth of Cu3(HITP)2, a two-dimensional (2D) conductive MOF with Cu at the center, around Si nanoparticles (SiNPs) at 27 °C. Enclosing the Si nanoparticles with the Cu-MOF yielded a desired buffer against the volume expansion and also effective electron- and ion-conducting channels for the SiNPs. Accordingly, the Cu-MOF-coated Si electrode exhibited high structural stability and low electrochemical degradation during lithiation/delithiation cycles. The electrode composed of SiNPs coated with 5% Cu-MOF exhibited an extremely high initial reversible capacity of 2511 mAh g−1 at the 0.1C rate with a coulombic efficiency of 78.5% in the first cycle and a capacity of 2483 mAh g−1 after 100 cycles. The reversible capacities during rate capability were 1303, 785, and 404 mAh g−1 at the rates of 5, 10, and 20C, respectively. The Cu-MOF (5%) delivered a reversible capacity of 1039 mAh g−1, even after 1000 cycles, at the high rate of 1C. The full-cell, composed of the Cu-MOF-coated Si anode and a LiCoO2 cathode, exhibited a remarkable rate capability and cyclability at 0.1C. This full-cell supplied a reversible (discharge) capacity of 1267 and 1105 mAh g−1 at rates of 0.5C and 1C, respectively. These results demonstrate the considerable potential of the synthesized Cu-MOF-encaged Si as a competitive anode material for next-generation LIBs in the near future.

Ab initio study of N-doped graphene oxide (NDGO) as a promising anode material for Li-ion rechargeable battery

ABSTRACT Since high capacity small rechargeable ion storage batteries are greatly required due to the increasing development of mobile technologies, search for new types of electrode materials with superior electrochemical properties are being explored. From its synthesis, graphene and its derivatives have been hypothesised as potential candidates for the anode material for Li-ion batteries (LIB) for their excellent electronic properties. In this work, first-principles simulation has been performed to investigate structural, electronic, adsorption and electrochemical properties of LIB where three different nitrogen-doped graphene oxide nanosheets (NDGO), with one, two and three oxygen atoms, have been chosen as anode materials with density functional theory using GGA-PBE functional. Our electrode materials predict superior structural stability without significant structural deformation. We have found that the Li+ ions are adsorbed on the electrode materials with favourable adsorption energy of 2.68 eV. The theoretical specific capacity has been found to be 1150 mAh/g which is three times higher than conventional bulk graphite. Moreover, during the lithiation process, the open-circuit voltage is found to be of 2.19 V which is benign for suppressing the dendrites formation. Our investigations provide an indication to develop better anode materials with high structural stability and high-capacity Li-ion batteries.

Analysis of nanostructured cobalt ion beam-modified Ge surface for high capacity Li-ion battery anodes by X-ray photoelectron spectroscopy

The results of the study of nanostructured germanium (Ge), intended for its subsequent use as electrodes of lithium-ion batteries are presented. Single-crystal germanium plate was irradiated by cobalt ions with an energy of 40 keV in the dose 4×1016 Co+ / cm2 for the nanostructuring. The changes in the elemental composition occurring during the electrochemical lithiation of manufactured germanium electrode were investigated by X-ray photoelectron spectroscopy (XPS).

57Fe Mössbauer study of high-valent Fe ions in Fe-substituted Li2MnO3

The valence of Fe is important not only for chemical properties but also for magnetism and catalytic activity and so on. Fe substituted Li2MnO3 is known as a novel positive electrode material for high-capacity Li-ion battery. In the study of this material, high-valent (4+ or over) Fe ions were observed. In the previous studies, most of such high-valent Fe ions had been observed in the octahedral site of perovskite structure, for example, SrFeO3. However, Li2MnO3 has a rock-salt related structure. To elucidate the origin of this high-valent Fe, we observed 57Fe Mossbauer spectroscopy of Li1 + x(Fe0.2Mn0.8)1-xO2. The Mossbauer spectra measured at 3 K contained magnetic Fe4+ and Fe5+. The area ratios of these components in the sample calcined in oxide were larger than those in the sample calcined in nitrogen. This result did not agree with the ratio of Fe sites obtained from X-ray diffraction. These high iron oxides are thought to be expressed by interaction with oxygen rather than site differences.

Vulnerable window of yield strength for swelling-driven fracture of phase-transforming battery materials

Despite numerous experimental and theoretical investigations of the mechanical behavior of high-capacity Si and Ge Li-ion battery anodes, our basic understanding of swelling-driven fracture in these materials remains limited. Existing theoretical studies have provided insights into elasto-plastic deformations caused by large volume change phase transformations, but have not modeled fracture explicitly beyond Griffith’s criterion. Here, we use a multi-physics phase-field approach to model self-consistently anisotropic phase transformation, elasto-plastic deformation, and crack initiation and propagation during lithiation of Si nanopillars. Our computational results reveal that fracture occurs within a “vulnerable window” inside the two-dimensional parameter space of yield strength and fracture energy and highlight the importance of taking into account the surface localization of plastic deformation to accurately predict the magnitude of tensile stresses at the onset of fracture. They further demonstrate how the increased robustness of hollow nanopillars can be understood as a direct effect of anode geometry on the size of this vulnerable window. Those insights provide an improved theoretical basis for designing next-generation mechanically stable phase-transforming battery materials undergoing large volume changes.

Electrochemical Study of Li-Ion Battery Anode (Graphite) and Cathode (NMC811) Surface Film Formation By in-Situ Scanning Probe Microscopy

Lithium ion battery usage has grown significantly in recent years. To obtain the best from the li-ion battery technology, it is important to understand both advantages and the limitations from the fundamental point of view. In lithium-ion batteries, layer structured graphite is the most commonly used anode material and NMC is one of the modern choices of cathode materials for high capacity Li-ion batteries in the electric vehicle applications [1,2,3].During the first charging process, the electrochemical reduction of electrolyte components gets deposited on the surface of anode resulting solid electrolyte interface (SEI) layer formation [4,5,6]. It is widely accepted that the batteries benefit from a proper SEI formation, as it can improve their lifetime, cycle life, power capability and safety [7].Morphological structure of SEI layer formed on HOPG and cathode electrolyte interface (CEI) layer formed on NMC plays an important role in lithium-ion battery (LIB), particularly for its cyclability and safety. For the development of high-performance LIB’s, it is crucial to understand the SEI layer formation on anode side [8] and the less studied corresponding layer formed on cathode side termed as CEI, whose composition and role are debated [9].Microscopic techniques, which include scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are the most powerful tools to measure the electric current and surface topography [10,11]. Within this work, we present in-situ electrochemical atomic force microscopic (EC-AFM) studies of surface reaction and topographic evolution of SEI and CEI layers formed on HOPG and NMC811 substrates. EC-AFM morphological analysis is also complemented with XPS (X-ray Photoemission Spectroscopy) characterisation for elemental composition, which brings a new insight in the comparison of SEI/CEI decomposition products. Acknowledgements: This work is partially supported by Faraday Institution (EP/S003053/1) and North-East Centre of Energy Materials-NECEM (EP/R021503/1) funded by EPSRC.

Interconnected conductive gel binder for high capacity silicon anode for Li-ion batteries

A new design for conjugation and crosslinking combined with a conjugated polymer and its application for high capacity Li-ion battery are demonstrated. Polyfluorene (PF), poly(phenylene) (PP), with lateral substituents, namely carboxylic acids, as a potential building block for conjugation was synthesized and characterized. The synthesis was achieved through Suzuki polycondensation reaction in the presence of Pd(PPh3)4 catalyst by using dibromo benzoic acid in conjunction with dioctylfluorene-diboronic acid bis(1,3-propanediol) ester. Thermal chemical cross-linking between carboxylic acid in the polymer backbone and free hydroxyl groups in poly(vinyl alcohol) (PVA) has been performed in the presence of Si. This approach enables a polymer binder with multi-functionality providing a high electronic conductivity and good cycling stability. Overall, we report on a Si-anode with capacity of 1932 mAh/g at C/3, demonstrating the improvement of the electrode using gel polymer binder.

A novel designed visualized Li-ion battery for in-situ measuring the variation of internal temperature

Since thermal safety is a significant topic in Li-ion batteries (LIBs), monitoring the internal temperature can offer valuable information to clarify the mechanism of heat accumulation. However, it is a challenge to measure the internal temperature of LIBs due to the harsh electrochemical environment and unexpected impacts on the battery performance. For addressing such issue, a novel internal temperature measurement technique with a minimized influence on the electrochemical performance is developed for in situ measuring the internal temperature of the LIB. In the specific design, one end of the LIB is sealed with a BaF2 optical glass, through which the infrared camera is allowed for real-time monitoring the internal temperature during charging and discharging processes. In addition to a stable electrochemical performance in such the visualized LIB, the observation results indicate that the temperatures are different during the charging and discharging processes. A maximum temperature difference 2.0°C between internal and surface of the visualized LIB is observed at the end of discharge process under 2C rate condition. It indicates that internal temperature is more important to analyze the effects of temperature on the thermal safety of the high capacity LIBs. The proposed internal temperature measurement technique could be widely used for analyzing the effects of temperature on the thermal safety of LIBs in further work.

Hybrid Nanostructured Ni(OH)2/NiO for High-Capacity Lithium-Ion Battery Anodes

Abstract A straightforward hydrothermal process followed by a controlled calcination technique is proposed for the synthesis of a Ni(OH)2 modified NiO nanohybrid structure. Conversion materials such as Li-ion battery anodes, NiO in this case, suffer from capacity fade and structural/morphological instability during lithiation and delithiation. The novelty of this work is in utilizing this hybrid configuration to increase the specific capacity and enable reversible electrochemistry. In the present work, we study the lithiation/delithiation process of NiO using a suite of spectroscopy and microscopy techniques from the atomic to electrode scale. We propose a mechanism for a reversible redox couple behavior of the NiO electrode by means of a hybrid Ni(OH)2/NiO structure. The ultimate objective of this work is to guide the development of anode with rationally designed heterogeneity to create high-capacity Li-ion batteries with excellent cycling and rate performance.

High mass loading additive-free LiFePO4 cathodes with 500 μm thickness for high areal capacity Li-ion batteries

We report the preparation of thick ceramic electrodes of the olivine LiFePO4 (LFP) with high mass loading. These electrodes are preparated by means of Powder Extrusion Moulding (PEM), which is a technology easily scalable and cheap. These LFP cathodes are additive-free (neither binder nor extra carbon black) with ~0.5 mm thickness, allowing to develop very high areal capacity (13.7 mA h cm−2). By means of a strict control of sintering process, the carbon coating of the commercial LFP powder remains and the decomposition of the active material is prevented. The optimized self-supported LFP cathode presents good cyclability over 20 cycles at C/10 with no capacity loss. The good electrochemical performance of these novel LFP thick electrodes and their non-flammability make them interesting candidates for both mobile and stationary applications.

Nitrogen Doped Multi-channel Graphite for High Rate and High Capacity Li Ion Battery

Nitrogen doped multi-channel graphite was successfully prepared by using nitrogen doping and KOH etching technologies. The three-electrode and EIS tests indicates that the etched graphite possesses lower electrochemical resistance than the pristine graphite. The coin cell tests demonstrate that N doped multichannel graphite possesses a specific capacity of 361 mAh/g and coulombic efficiencies of 91.4%. No dramatic irreversible capacity loss results from the increased specific surface area (from 1.60 to 2.08 m2/g), removing the need for a trade-off between irreversible capacity loss and surface area. Full polymer cells were fabricated and electrochemical capabilities were measured. In 3C fast charge protocol, the charging capacity can reach 51% within 10 min charge, and 100% within 30 min, demonstrating excellent fast charging characteristic. The fast charge cycle performance with 3C-rate charge and 1C-rate discharge from 4.35-3.0 V was conducted at RT temperature. The capacity retention is 94% after 600 cycles, which shows good cycle performance.

Using nanoconfinement to inhibit the degradation pathways of conversion-metal oxide anodes for highly stable fast-charging Li-ion batteries

Nanostructured hybrids that physically encapsulate highly morphable, high capacity Li-ion battery anodes can potentially enable much longer cycle life than straightforward deployment of the same chemistry.

Temperature-Controlled Synthesis of Li- and Mn-Rich Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Nano/Sub-Microsphere Electrodes for High-Performance Lithium-Ion Battery.

The calcination temperature plays a significant role in the structural, textural, and energy-storage performance of metal oxide nanomaterials in Li-ion battery application. Here, we report the formation of well-crystallized homogeneously dispersed Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere architectures through a simple cost-effective coprecipitation and chemical mixing route without surface modification for improving the efficiency of energy storage devices. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere cathode materials are calcined at 800, 900, 950, and 1000 °C. Among them, Li1.2Mn0.54Ni0.13Co0.13O2 calcined at 950 °C exhibits a high discharge capacity (277 mAh g–1 at 0.1C rate) and excellent capacity retention (88%) after 50 cycles and also delivers an excellent discharge capacity of >172 mAh g–1 at 5C rate. Good electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2-950 is directly related to the optimized size of its primary particles (85 nm) (which constitute the spherical secondary particle, ∼720 nm) and homogeneous cation mixing. Higher calcination temperature (≥950 °C) leads to an increase of the primary particle size, poor cycling stability, and inferior rate capacity of Li1.2Mn0.54Ni0.13Co0.13O2 due to smashing of quasi-hollow spheres upon repeated lithium ion intercalations/deintercalations. Therefore, Li1.2Mn0.54Ni0.13Co0.13O2-950 is a promising electrode for the next-generation high-voltage and high-capacity Li-ion battery application.

On Ionic and Covalent Cross-Linking of Alginic Acid Derived Binders for High Capacity Silicon Anodes

The anode market for automotive Li-ion batteries is still governed by carbonaceous materials with a market share of 96%.[1] The graphite electrodes used today can only deliver a moderate capacity of 300-350 mAh/g, and improvements are highly sought. Silicon, often in the form of a silicon/carbon composite, is a promising alternative material with its high theoretical capacity of about 3600 mAh/g. As an alloy former this capacity is accompanied with a huge volume change of over 300%, deeming PVDF unsuitable as binder as it cannot withstand the volume changes upon cycling. A variety of technical and biopolymers were shown to drastically increase the cyclability of silicon based anodes. Prominent examples are s poly (acrylic acid) (PAA), carboxymethyl cellulose (CMC) and alginic acid (algin) derivatives. Algin, often purified as water soluble Na alginate, is a polysaccharide found in the cell walls of brown algae. It consists of the two epimers D-mannuronic acid (M) and L-guluronic acid (G), which's content and distribution have a strong impact on the 3D structure and properties. Superior cycling of Na alginate bound Si anodes was first described by Kovalenko et al..[2] The incorporation of divalent ions such as calcium, strontium, barium or transition metals causes strong chelation of the ions resulting in a hydrogel. Several studies have described that this ionic cross-linking has a profound effect on the cyclability of Si based anodes. [3],[4],[5],[6] Divalent ions are usually chelated by two adjacent G units on two polymer chains forming a so called egg-box and high degrees of saturation cause gelling, which obstructs processing. Since chelation including G units only is much stronger than the interaction with M groups, the M to G ratio should have a strong effect on the stability of the network. Covalent cross-linking should have an even stronger effect on the stability of the binder network as it is constructed of chemical bonds rather than ionic interactions. This study concerns the effect of different saturation degree of calcium and barium cross-linking on alginates with different M to G ratio as binder for Si based anodes. Furthermore, we discuss routes to form a covalently cross-linked algin derived network that is grafted to the Si surface. [1] Schmuch R., Wagner R., Hoerpel G., Placke T., Winter M., Performance and cost of materials for lithium-based rechargeable automotive batteries, Nature Energy, 3 (2018), 267-278. [2] Kovalenko, I., et al., A Major Constituent of Brown Algae for Use in High-Capacity Li-Ion Batteries. Science, 2011. 334(6052): p. 75-79. [3] Wua Z-Y., Deng L., Li J-T., et al. Multiple hydrogel alginate binders for Si anodes of lithium-ion battery. Electrochimica Acta, 245 (2017), 371–378. [4] Gu Y., Yang S., Zhu G., et al. The effects of cross-linking cations on the electrochemical behavior of silicon anodes with alginate binder, Electrochimica Acta, 269 (2018), 405-414. [5] Zhang L., Zhang L., Peng L. C., et al. A coordinatively cross-linked polymeric network as a functional binder for high-performance silicon submicro-particle anodes in lithium-ion batteries, J. Mater. Chem. A,2 (2014), 19036–19045 [6] Yoon J., Oh D. X., Jo C. et al., Improvement of desolvation and resilience of alginate binders for Si-based anodes in a lithium ion battery by calcium-mediated cross-linking, PCCP, 16 (2014), 25628-25635. Figure 1

Single Particle Characterization of Dynamic Morphological and Phase Changes in Selenium-Doped Germanium Anode during (de)Lithiation Processes

Germanium (Ge) is a promising candidate for high-capacity Li-ion battery anode due to its high theoretical capacity of 1384 mAh/g (for the charged Li15Ge4 phase), low operation voltage, fast bulk Li diffusion, and high electrical conductivity. However, the major challenge in the development of Ge anode is the large volume change involved in the reaction scheme, which could result in rapid loss of specific capacity. We recently reported that selenium (Se) -doped Ge (GeSe) forms an inactive phase that buffers the volumetric expansion of Ge which provides better cycling life and performance (1). However, the dynamic morphological and chemical transformations of GeSe that occur during battery cycling processes is still elusive. The traditional in-situ coin cell has rotating limitations which makes three-dimensional experiment difficult except via limited angle tomography. It also suffers from X-ray damage problems to the binder. To understand the dynamic morphological and chemical changes of GeSe, we developed a single particle battery cell for operando TXM and XANES. A micron-sized GeSe particle was attached to a pre-coated tungsten probe by ion beam carbon deposition on a Zeiss Nvision 40 FIB-SEM at the Center for Nanoscale Materials, Argonne National Laboratory. The single particle battery cell was assembled in an argon-filled glovebox. A small piece of Li metal was attached to a copper wire as the counter electrode. Both the tungsten and lithium electrodes were carefully inserted into a funnel-shaped open-ended silica capillary and stabilized via epoxy. The quartz housing was fully filled with 1 M LiPF6 EC/DEC electrolyte through a micro-syringe and sealed with torr seal epoxy. This binder free operando single particle cell eliminates discrepancies caused by particles overlapping in the in-situ coin cell during TXM and the impact of X-ray damage to the binder (2). It provides chemical and morphological information in three-dimensional space via computed nanotomography coupled with XANES. Figure 1 shows the performance of operando GeSe cell and the 2D morphological change of a GeSe particle attached to the tungsten probe at 11.113 keV. Regardless of the defect caused by the carbon deposition process, the results indicate that GeSe undergoes a different dynamic chemical transformation compared to pure Ge. The selenium-doped germanium has the ability to reinstate its original shape after cycling. This study can help to understand the mechanical stability and degradation mechanism of high capacity lithium alloy anode with additional stress-accommodating phase. K. C. Klavetter, J. Pedro de Souza, A. Heller, C. B. Mullins, High tap density microparticles of selenium-doped germanium as a high efficiency, stable cycling lithium-ion battery anode material. Journal of Materials Chemistry A 3, 5829-5834 (2015).L. Y. Lim, N. Liu, Y. Cui, M. F. Toney, Understanding Phase Transformation in Crystalline Ge Anodes for Li-Ion Batteries. Chemistry of Materials 26, 3739-3746 (2014). Figure 1

Carbon-coated silicon/crumpled graphene composite as anode material for lithium-ion batteries

Silicon is a promising anode material for high-capacity Li-ion batteries (LIBs). However, its insulating property and large volume change during the lithiation/delithiation process result in poor cycling stability and in pulverization of Si. In this work, glucose-derived carbon-coated Si nanoparticles (C–Si NPs) are in conjunction with crumpled graphene (cGr) particles by a spray-drying method to prepare a novel composite (C–Si/cGr) material. The prepared C–Si NPs are uniformly embedded in the ridges of the cGr particles. The carbon layer of C–Si can make a good contact with the graphene sheet, resulting in enhanced electrical conductivity and fast charge transfer. In addition, the unique crumpled structure of the cGr can buffer the large volume change upon cycling process and facilitate the diffusion of electrolyte into the composite material. When employed as an anode electrode of LIBs, the C–Si/cGr composites deliver enhanced electrochemical performance, including stable cycling with a discharge capacity of 790 mAh·g−1 after 100 cycles and a rate capability of 654 mAh·g−1 at 2C. The synergistic effect of the carbon layer coating of Si NPs and the crumpled structure of the cGr particles results in a composite with improved the electrochemical performance, which is likely related to its high electrical conductivity and good mechanical stability of composite material.

Lithium Nickel Manganese Oxide-Carbon Composite Nanoparticles Synthesized By a Flame Spray Pyrolysis Process

The nanoparticles based on either nickel-manganese oxide or carbon-coated LiNi0.5Mn1.5O4 are synthesized by flame spray pyrolysis technology with controlled particle sizes. The structural properties of nanoparticles are characterized by x-ray diffraction and high resolution electron microscopy. It is observed that the higher surface tension of precursors in the flame spray pyrolysis setup increases the particle sizes. The post annealing treatment significantly enhances the crystallinity of nanoparticles due to the favorable oxidation process and the structure conversion from NiMn2O4 to NiMnO3. In addition, the solid state reaction of as-prepared NiMn2O4 results in the LiNi0.5Mn1.5O4 nanoparticles which can be applied to cathode materials in Li-Ion batteries. The carbon-coated LiNi0.5Mn1.5O4 nanoparticles are also made by additional carbonization reaction. The control of surface tension of precursors in the flame spray pyrolysis process is expected to result in the small size of nanoparticles for cathode materials in high cyclic stability and high capacity Li-ion batteries.