We performed density functional theory (DFT) calculations for a bi-layered heterostructure combining a graphene layer with a MoS2 layer with and without intercalated Li atoms. Our calculations demonstrate the importance of the van der Waals (vdW) interaction, which is crucial for forming stable bonding between the layers. Our DFT calculation correctly reproduces the linear dispersion, or Dirac cone, feature at the Fermi energy for the isolated graphene monolayer and the band gap for the MoS2 monolayer. For the combined graphene/MoS2 bi-layer, we observe interesting electronic structure and density of states (DOS) characteristics near the Fermi energy, showing both the gap like features of the MoS2 layer and in-gap states with linear dispersion contributed mostly by the graphene layer. Our calculated total density of states (DOS) in this vdW heterostructure reveals that the graphene layer significantly contributes to pinning the Fermi energy at the center of the band gap of MoS2. We also find that intercalating Li ions in between the layers of the graphene/MoS2 heterostructure enhances the binding energy through orbital hybridizations between cations (Li adatoms) and anions (graphene and MoS2 monolayers). Moreover, we calculate the dielectric function of the Li intercalated graphene/MoS2 heterostructure, the imaginary component of which can be directly compared with experimental measurements of optical conductivity in order to validate our theoretical prediction. We observe sharp features in the imaginary component of the dielectric function, which shows the presence of a Drude peak in the optical conductivity, and therefore metallicity in the lithiated graphene/MoS2 heterostructure.
Si-anodes have long been candidates thanks to an expected ten-fold increase in capacity compared to graphite. However, details of the mechanisms governing their degradation remain elusive, hindering science-guided development of long-lived Si-based anodes. Here we demonstrate how the latest developments in cryo-atom probe tomography enable the in-depth analysis of the electrode and electrolyte, and their interface at atomic-level.
We present a comparative ab initio computational study of sodium and lithium storage in amorphous (glassy) carbon (a-C) vs. graphite. Amorphous structures are obtained by fitting stochastically generated structures to a reference radial distribution function. Li insertion is thermodynamically favored in both graphite and a-C. While sodium insertion is thermodynamically unfavored in graphite, a-C possesses multiple insertion sites with binding energies stronger than Na cohesive energy, making it usable as anode material for Na-ion batteries.
In this paper, Al-Cu-Fe quasicrystal alloy was used as anode material of lithium-ion batteries. The first specific discharge capacity of quasicrystal was 204mAh/g. Cyclic voltammetry showed that oxidation peak of Al-Cu-Fe quasicrystal was at about 1.4V. The reduction peak was at 0.3V. Al-Cu-Fe quasicrystal have higher Li-ion diffusion impedance and Warburg in the first cycle. X-ray diffraction analysis demonstrate that Li atom enter into quasicrystal structure can not fully leave quasicrytal during first charge/discharge cycle which induce the irreversible capacity.
Li-ion rechargeable batteries have enabled the wireless revolution transforming global communication. Future challenges, however, demands distributed energy supply at a level that is not feasible with the current energy-storage technology. New materials, capable of providing higher energy density are needed. Here we report a new class of lithium-ion batteries based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode, we demonstrate an optimal battery performance in terms of spec…
The 3D ternary Li_4Ti_5O_12, the Li+-based battery anode, presents the unusual lattice symmetry (a triclinic crystal), band structure, charge density, and density of states, under the first-principles calculations. It belongs to a large direct-gap semiconductor of E_g^d~ 2,98 eV. The atom-dominated valence and conduction bands, the spatial charge distribution and the atom- and orbital-decomposed van Hove singularities are available in the delicate identifications of multi-orbital hybridizations in Li-O and Ti-O bonds. The extremely non-uniform chemical environment, which induce the very compli…
Extensive efforts have been devoted to C-Si compound materials for improving the limited specific capacity of graphite anode and avoiding the huge volume change of Si anode in Li-ion battery, but not much progress has been made during the past decades. Here, for the first time we apply the targeted structure search by using Li in desired quantity as chemical template to regulate the bonding between C and Si, which makes searching more feasible for us to find a new stable phase of C2Si (labelled as T-C2Si) that can better fit the XRD data of silicon dicarbide synthesized before. Different from …
Here we report fabrication of flexible and stretchable battery composed of strain free LiFePO4 cathode, Li4Ti5O10 anode and a solid poly ethylene oxide (PEO) electrolyte as a separator layer. The battery is developed in a view of smart textile applications. Featuring solid thermoplastic electrolyte as a key enabling element this battery is potentially extrudable or drawable into fibers or thin stripes which are directly compatible with the weaving process used in smart textile fabrication. The paper first details the choice of materials, fabrication and characterisation of electrodes and a sep…
We have investigated adsorption of Na and Ca on graphene with divacancy (DV) and Stone-Wales (SW) defect. Our results show that adsorption is not possible on pristine graphene. However, their adsorption on defective sheet is energetically favorable. The enhanced adsorption can be attributed to the increased charge transfer between adatoms and underlying defective sheet. With the increase in defect density until certain possible limit, maximum percentage of adsorption also increases giving higher battery capacity. For maximum possible DV defect, we can achieve maximum capacity of 1459 mAh/g for…
The prospects of phosphorene as an anode material for high performance Li-ion battery was systematically investigated from the first principle calculations and experimental measurements. The diffusion energy barriers of a Li atom moving along various orientations on phosphorene layer were calculated from the Li adsorption energy landscape. It was found that the diffusion mobility of a Li atom along the zigzag direction in the valley of phosphorene could be about 7 to 11 orders of magnitude faster than that along the other directions, indicating its ultrafast and anisotropic diffusivity. The li…
Developing efficient anode materials with low electrode voltage, high specific capacity and superior rate capability is urgently required on the road to commercially viable sodium-ion batteries (SIBs). Aiming at finding a new SIB anode material, we investigate the electrochemical properties of NaxTiO2 compounds with unprecedented penta-oxygen-coordinated trigonal bipyramid (TB) structures by using the first-principles calculations. Identifying the four different TB phases, we perform the optimization of their crystal structures and calculate their energetics such as sodium binding energy, form…
The market quest for fast-charging, safe, long-lasting and performant batteries drives the exploration of new energy storage materials, but also promotes fundamental investigations of materials already widely used. Presently, revamped interest in anode materials is observed -- primarily graphite electrodes for lithium-ion batteries. Here, we focus on the upper limit of lithium intercalation in the morphologically quasi-ideal highly oriented pyrolytic graphite (HOPG), with a LiC$_6$ stoichiometry corresponding to 100\% state of charge (SOC). We prepared a sample by immersion in liquid lithium a…
The decomposition of ethylene carbonate (EC) during the initial growth of solid-electrolyte interphase (SEI) films at the solvent-graphitic anode interface is critical to lithium ion battery operations. Ab initio molecular dynamics simulations of explicit liquid EC/graphite interfaces are conducted to study these electrochemical reactions. We show that carbon edge terminations are crucial at this stage, and that achievable experimental conditions can lead to surprisingly fast EC breakdown mechanisms, yielding decomposition products seen in experiments but not previously predicted.
Inspired by a recent experimental and theoretical study [Yang et al., 2017], wherein protrusions in graphene have been proposed as an effective strategy to enhance the performance of sodium ion batteries, a comprehensive study of the effects of phosphorus doping in graphene on adsorption and diffusion behaviour of Li is carried out by using density functional theory. We find that protrusion introduced by P-dopant in graphene enhances the adsorption of a single Li atom onto the anode due to an additional partial covalent bonding character between Li and carbon atoms of the substrate. However, w…
Herein, in-situ reduction of bismuth and graphene oxide was performed by a solvothermal method under a nitrogen atmosphere, and the resulting Bi on RGO nanocomposites were used as an anode material for Mg-ion batteries. The nanocomposite of 60% Bi:40% RGO is a beneficial anode material, delivering a discharge capacity as high as 413 and 372 mAh per g at the specific current of 39 mA per g in the 1st and 50th cycles, respectively. In addition, it shows high-rate capability with the discharge capacities of 381, 372, 354, 295, and 238 mAh per g at the specific currents of 53, 100, 200, 500, and 7…
How surface chemistry influences reactions occurring thereupon has been a long-standing question of broad scientific and technological interest for centuries. Recently, it has re-emerged as a critical question in a subdiscipline of chemistry - electrochemistry at heterointerphases, where the answers have implications for both how, and in what forms, humanity stores the rising quantities of renewable electric power generated from solar and wind installations world-wide. Here we consider the relation between the surface chemistry at such interphases and the reversibility of electrochemical trans…
We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interacti…
Amorphous polymer derived silicon oxycarbide (SiOC) is an attractive candidate for Lithium ion battery anodes, as an alternative to graphite, which is limited to a theoretical capacity of 372 mAh/g. However, SiOC tends to exhibit poor transport properties and cycling performance as a result of sparsely distributed carbon clusters and inefficient active sites. To overcome these limitations, we designed and fabricated a layered graphene SiOC heterostructure by solvent assisted infiltration of a polymeric precursor into a modified three dimensional graphene aerogel skeleton. The use of a high mel…
Existence of van der Waals gaps renders two-dimensional (2D) materials ideal passages of lithium for being used as anode materials. However, the requirement of good conductivity significantly limits the choice of 2D candidates. So far only graphite is satisfying due to its relatively high conductivity. Recently, a new polymorph of layered germanium selenide (Gamma-GeSe) was proven to be semimetal in its bulk phase with a higher conductivity than graphite while its monolayer behaves semiconducting. In this work, by using first-principles calculations, we examined the possibility of using this n…
Searching for three-dimensional(3D) semiconducting carbon allotropes with proper bandgaps and excellent optoelectronic properties is always the chasing goal for the new emerging all-carbon optoelectronics. On the other side, 3D carbon materials have also been recognized as promising anode materials superior to commercialized graphite in Li-ion batteries (LIBs). Here, using first-principles calculations, we propose two novel 3D carbon allotropes through acetylenic linkages modification of two structurally intimately correlated 3D carbon structures - carbon kagome lattice(CKL)and interpenetrated…
We report a comprehensive study on the electrochemical performance of four different Transition Metal Oxides encapsulated inside carbon nanotubes (CNT). Irrespective of the type of oxide-encapsulate, all these samples exhibit superior cyclic stability as compared to the bare-oxide. Innovative use of camphor during sample synthesis enables precise control over the morphology of these self-organized carbon nanotube structures, which in turn appears to play a crucial role in the magnitude of the specific capacity. A comparative evaluation of the electrochemical data on different samples bring for…
Lithium ion batteries (LIB) can feature reactive anodes that operate at low potentials, such as lithium metal or silicon, passivated by solid electrolyte interphase (SEI) films. SEI is known to evolve over time as cycling proceeds. In this modeling work, we focus on the stability of two main SEI components, lithium carbonate (Li2CO3) and lithium ethylene dicarbonate (LEDC). Both components are electrochemically stable but thermodynamically unstable near the equilibrium Li+/Li(s) potential. Interfacial reactions represent one way to trigger the intrinsic thermodynamic instability. Both Li(2)CO(…
A 3D mechanical stable scaffold is shown to accommodate the volume change of a high specific capacity nickel-tin nanocomposite Li-ion battery anode. When the nickel-tin anode is formed on an electrochemically inactive conductive scaffold with an engineered free volume and controlled characteristic dimensions, it exhibits significantly improved the cyclability.
A high reversible capacity is a key feature for any rechargeable battery. In the lithium-ion battery technology, tin-oxide anodes do fulfill this requirement, but a fast loss of capacity hinders a full commercialization. Using first-principles calculations, we propose a microscopic model that sheds light on the reversible lithiation/delithiation of SnO and reveals that a sintering of Sn causes a strong degradation of SnO-based anodes. When the initial irreversible transformation ends, active anode grains consist of Li-oxide layers separated by Sn bilayers. During the following reversible lithi…
A novel WS2-graphite dual-ion battery (DIB) is developed by combining together a conventional graphite cathode and high-capacity few-layer WS2 flakes anode. The WS2 flakes are produced by exploiting wet-jet milling (WJM) exfoliation, which allows mass production of few-layer WS2 flakes in dispersion, with an exfoliation yield of 100%. The WS2-anodes enable DIBs, based on hexafluorophosphate (PF6-) and lithium (Li+) ions, to achieve charge specific capacities of 457, 438, 421, 403, 295 and 169 mAh g-1 at current rates of 0.1, 0.2, 0.3, 0.4, 0.8 and 1.0 A g-1, respectively, outperforming convent…
Batteries are the most abundant form of electrochemical energy storage. Lithium and sodium ion batteries account for a significant portion of the battery market, but high-performance electrochemically active materials still need to be discovered and optimized for these technologies. Recently, tin(II) oxide (SnO) has emerged as a highly-promising battery electrode. In this work, we present a facile synthesis method to produce SnO nanoparticles whose size and shape can be tailored by changing the solvent nature. We study the complex relationship between wet chemistry synthesis conditions and res…
Poor electrical conductivity and large volume expansion during repeated charge and discharge is what has characterized many battery electrode materials in current use. This has led to 2D materials, specifically multi-layered 2D systems, being considered as alternatives. Among these 2D multi-layered systems are the graphene-based van der Waals heterostructures with transition metal di-chalcogenides (TMDCs) as one of the layers. Thus in this study, graphene-Hafnium disulphide (Gr-HfS$_2$) system, has been investigated as a prototype Gr-TMDC system for application as battery electrode. Density fu…
Solid state battery technology has recently garnered considerable interest from companies including Toyota, BMW, Dyson, and others. The primary driver behind the commercialization of solid state batteries (SSBs) is to enable the use of lithium metal as the anode, as opposed to the currently used carbon anode, which would result in ~20% energy density improvement. However, no reported solid state battery to date meets all of the performance metrics of state of the art liquid electrolyte lithium ion batteries (LIBs) and indeed several solid state electrolyte (SSE) technologies may never reach pa…
In the quest to increase battery performance, nanostructuring battery electrodes gives access to architectures with electrical conductivity and solid-state diffusion regimes not accessible with traditional electrodes based on aggregated spherical microparticles, while often also contributing to the cyclability of otherwise unstable active materials. This work describes electrodes where active material and current collector are formed as a single nanostructured composite network, consisting of macroscopic fabrics of carbon nanotube fibers covered with conformal MoS2 grown preferentially aligned…
Magnesium (Mg) metal has been widely explored as an anode material for Mg-ion batteries (MIBs) owing to its large specific capacity and dendrite-free operation. However critical challenges, such as the formation of passivation layers during battery operation and anode-electrolyte-cathode incompatibilities, limit the practical application of Mg-metal anodes for MIBs. Motivated by the promise of group XIV elements (namely Si, Ge and Sn) as anodes for lithium- and sodium-ion batteries, here we conduct systematic first principles calculations to explore the thermodynamics and kinetics of group XIV…
Conditional spinodal decomposition in Li-Mg anodes for lithium metal batteries
Max Planck Institute for Sustainable Materials（马克斯·普朗克可持续材料研究所）；Aeronautics Institute of Technology（航空技术学院）；Université de Picardie Jules Verne（亚眠儒勒·凡尔纳大学）；University Grenoble Alpes, CNRS, Grenoble INP, SIMAP（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，格勒诺布尔理工学院，SIMAP）；Thermo-Calc Software AB（Thermo-Calc软件有限公司）；Federal University of São Carlos（圣卡洛斯联邦大学）；Korea University（高丽大学）；Univ Rouen Normandie, CNRS, INSA Rouen Normandie, Groupe de Physique des Matériaux, UMR 6634（鲁昂诺曼底大学，法国国家科学研究中心，鲁昂诺曼底国立应用科学学院，材料物理研究组）
Benefited from the advantages on environmental benign, easy purification, and high thermal stability, the recently synthesized two-dimensional (2D) material MoN2 shows great potential for clean and renewable energy applications. Here, through first-principles calculations, we show that the monolayered MoN2 is promising to be a high capacity electrode material for metal ion batteries. Firstly, identified by phonon dispersion and exfoliation energy calculations, MoN2 monolayer is proved to be structurally stable and could be exfoliated from its bulk counterpart in experiments. Secondly, all the …
B$_5$Se this work we investigate the Li adsorption properties of a hybrid 2D material, namely monolayer B5Se with first principles calculations. 2 dimensional B$_5$Se was found to have a distorted hexagonal structure with five B atoms and one Se atom at the vertices of each hexagon. The density functional theory (DFT) calculations are performed with the generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhoff (PBE) exchange correlation functional. The results were inclusive of van der Waals corrections with Grimmes DFT-D2 scheme. Electrode performance metrics, as the most preferred…
As renewable energy is becoming a critical energy source to meet the global demand, electrochemical energy storage devices become indispensable for the efficient energy storage and reliable supply. The electrode material is the key factor determining the energy storage capacity and the power delivery of the devices. Carbon-based materials are emerging as a viable candidate for electrodes, yet their low energy densities impede the development of advanced energy storage materials. Nanoparticle decoration of the carbon structures is one of the most promising and easy-to-implement a strategy to en…
Phosphorus is one of the most promising anodes for sodium ion batteries (SIBs). Little is known about the structural mechanism of Na/P cycling due to the fact that only one of the structures involved (Na3P) is crystalline. Using operando X-ray diffraction computed tomography (XRD-CT) analysed by Rietveld and pair distribution (PDF) methods combined with density functional theory (DFT) calculations we show that the sodiation and desodiation mechanisms of phosphorus are very different. Sodiation follows the thermodynamic path of lowest energy from P via NaP to Na3P while desodiation follows a ki…
Enhanced EV market penetration requires durability of the battery with high energy throughput. For long-term cycle stability of silicon-graphite anode capable of high energy density, the reversible redox reactions are crucial. Here, we unveil intriguing electrochemical phenomena such as crosstalk of lithium ion ($Li^{+}$) between silicon and graphite, $Li^{+}$ accumulation in silicon, and capacity depression of graphite under high pressure, which engender the irreversible redox reactions. Active material properties, i.e. the size of silicon and the hardness of graphite, silicon-graphite anode,…
Many key performance characteristics of carbon-based lithium-ion battery anodes are largely determined by the strength of binding between lithium (Li) and sp2 carbon (C), which can vary significantly with subtle changes in substrate structure, chemistry, and morphology. Here, we use density functional theory calculations to investigate the interactions of Li with a wide variety of sp2 C substrates, including pristine, defective, and strained graphene; planar C clusters; nanotubes; C edges; and multilayer stacks. In almost all cases, we find a universal linear relation between the Li-C binding …
Battery interfaces help govern rate capability, safety/stability, cycle life, and self-discharge, but significant gaps remain in our understanding at atomic length scales that can be exploited to improve interfacial properties. In particular, Li partially plated on copper current collectors, relevant to the anodeless, lithium metal cell which is a holy grail of high density energy battery research, has recently been reported to undergo galvanic corrosion and exhibit short shelf lives. We apply large scale Density Functional Theory (DFT) calculations and X-ray photoelectron spectroscopy to exam…
Theoretical Studies on Sodium Storage Mechanism in Hard Carbon Anodes of Sodium-Ion Batteries: Molecular Simulations Based on Machine Learning Force Fields
Black phosphorous is a layered material having a high capacity of 2596 mAh/g as a battery electrode, however it suffers from cracking due to high volume expansion during lithiation. These cracks causes loss of electrical contact in the whole material, therefore capacity fades after further cycles of charging and discharging. One needs a support material which would not crack with lithiation of phosphorous in order to keep the electrical contact of the material. Here, we considered phosphorene sandwiched between graphene layers. By using density functional theory, we calculated voltages of lith…
Identifying applicable anode materials is a significant task for Li- and Na-ion battery (LIB and NIB) technologies. We propose the GaN monolayer (2D GaN) can be a good anode candidate. The GaN monolayer manifests stable Li/Na adsorption and inherently low theoretical voltages. Most excitingly, both high storage capacity and extremely fast Li/Na diffusion can be simultaneously realized in the GaN monolayer. For Li, the storage capacity and diffusion barrier is 938 mA h g-1 and 80 meV , respectively. And the values for Na are 625 mA h g-1 and 22 meV. Comparing with known 2D anode materials with …
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 pro…
The diffusion of Li in electrode materials is key factor to charging/discharging rate capacity of Li-ion battery (LIB). Recently, two-dimensional phosphorene has been proposed as a very promising electrode material due to its ultrafast and directional lithium diffusion, as well as large energy capacity. Here, on the basis of density functional theory, we report that the intrinsic point defects, including vacancy and stone-wales defects, will block the directional ultrafast diffusion of lithium in phosphorene. On the defect-free phosphorene, diffusion of Li along the zigzag lattice direction is…
Next-generation high-energy-density batteries require ideally stable metal anodes, for which smooth metal deposits during battery recharging are considered a sign of interfacial stability that can ensure high efficiency and long cycle life. With the recent successes, whether the absolute morphological stability guarantees absolute electrochemical stability and safety emerges as a critical question to be investigated in systematic experiments under practical conditions. Here, we use the ideally stable ingot-type sodium metal anode as a model system to identify the fast-charging limits, i.e. hig…
It is shown that continuously occurring electrolyte-reduction reaction on freshly-exposed electrode surfaces during lithiation/delithiation cycles causes the lowering of cycling efficiency, and hence, capacity fade in well-cycled silicon anodes in lithium-ion batteries. Using galvanostatic lithiation/delithiation data from multiple cycles on a Li/Si half-cell, a methodology to separate the charge due to the main reaction (lithiation/delithiation of Si) from the side-reaction (electrolyte-reduction) is presented. The rate of this parasitic side reaction is estimated on well-cycled amorphous sil…
