Cycles For Lithium-ion Batteries Research Articles

Direct surface coating of high voltage LiCoO2 cathode with P(VDF-HFP) based gel polymer electrolyte.

For high-voltage cycling of lithium-ion batteries, a gel polymer Li-ion conductor layer, P(VDF-HFP)/LiTFSI (PHL) with high electrochemical stability has been coated on the surfaces of as-formed LiCoO2 (LCO) cathodes by a solution-casting technique at low temperature. An LCO cathode coated with around 3 μm thickness of the PHL ultrathin membrane, retains 88.4% of its original capacity (184.3 mA h g−1) after 200 cycles in the 3.0–4.6 V range with a standard carbonate electrolyte, while the non-coated one retains only 80.4% of its original capacity (171.5 mA h g−1). The reason for the better electrochemical behaviors and high-voltage cycling is related to the distinctive characteristics of the PHL coating layer that is compact, has highly-continuous surface coverage and penetrates the bulk of LCO, forming an integrated electrode. The PHL coating layer plays the role of an ion-conductive protection barrier to inhibit side reactions between the charged LCO surface and electrolyte, reduces the dissolution of cobalt ions and maintains the structural stability of LCO. Further, the PHL coated LCO cathode is well preserved, compared to the uncoated one which is severely cracked after 200 cycles at a charging cut-off voltage of 4.6 V.

In-situ synthesis of microspherical Sb@C composite anode with high tap density for lithium/sodium-ion batteries

Abstract The search for anode materials that suitable for both lithium-ion and sodium-ion batteries is one of the most top challenges in the field of rechargeable batteries. In this work, Sb@C composites are synthesized via in-situ calcination of as-prepared micro-spherical Sb2O3 in the presence of polyethylene glycol (PEG), which acts as a reductive agent and carbon source. The Sb@C composites with a structure of microspheres are composed of crystalline Sb nanoparticles coated by interconnected porous carbon. Such an unique structure not only provides a stable conductive matrix, but also leads to a high tap density of 1.35 g cm−3. A specific capacity of 280 mAh g−1 can be retained at 100 mA g−1 after 500 cycles for lithium-ion batteries and 130 mA g−1 at 100 mA g−1 after 100 cycles for sodium-ion batteries.

Superior full battery performance of tunable hollow N-Doped carbonaceous fibers encapsulating Ni3S2 nanocrystals with enhanced Li/Na storage

A controlled bioleaching strategy to embed Ni3S2 nanocrystals into 1D hollow carbonaceous fibers derived from renewable biomass was designed with enough inner voids as well as abundant natural pyridinic and pyrrolic nitrogen. The hollow fiber-based electrode can prevent the large volume expansion, improve the electronic conductivity and enhance the diffusion rate of Li+/Na+ ion. As a result, the synthesized Ni3S2/hollow carbonaceous fiber electrodes deliver excellent reversible capacity and outstanding cycle stability, i.e., 673.4 mAh g−1 at 0.1 A g−1 after 100 cycles for lithium-ion batteries (LIBs), 378.4 mAh g−1 at 1 A g−1 after 100 cycles for sodium-ion batteries (SIBs), in electrochemical half-cells. More importantly, a superior electrochemical performance is obtained in a full-cell when employing Na3V2(PO4)3 as cathode (i.e., 218.9 mAh g−1 after 100 cycles at 0.5 A g−1).

Artificial Solid Electrolyte Interphase Formation on Si Nanoparticles through Radiolysis: Importance of the Presence of an Additive

In the context of energy transition, irradiation is a powerful tool to mimic quickly the modification of electrode materials upon charge/discharge cycles in lithium-ion batteries. In this study, the evolution of the surface of silicon nanoparticles upon irradiation in two electrolytes, containing or not fluoroethylene carbonate (FEC), was studied. In the presence of FEC, irradiation leads to the formation of a homogeneous layer of a few nanometers thick, covering the whole surface of the nanoparticles. The formation of an artificial solid electrolyte interphase (SEI) layer through radiolysis is thus achieved. Without FEC, only patches of degradation products are formed on the nanoparticle surfaces for the same irradiation dose. In the absence of FEC, LixPFyOz salts are formed. In the presence of FEC, LixPOy, LiF, and Si–F bonds are generated. In both cases, the interphase contains Li2CO3 and a polymer containing ethylene carbonate units. Slightly different polymers are formed at the surface of nanoparticles in the presence or absence of FEC, i.e., more cross-linked in the former case. The elastomeric properties of the polymer formed in the presence of FEC are thought to be responsible for the formation of the homogeneous layer on the Si surfaces, leading to the generation of an artificial solid SEI through the radiolysis process. This SEI, however, prevents the efficient transfer of Li+ ions, and more work is required to optimize its intrinsic (electro)chemical properties.

Evaluation of Gas Formation and Consumption Driven by Crossover Effect in High-Voltage Lithium-Ion Batteries with Ni-Rich NMC Cathodes.

Gas formation during lithium-ion battery (LIB) cycling impacts the stability and safety of these batteries, especially for those containing Ni-rich NMC cathodes. In this paper, the cycling performance and gassing behavior of NMC811/graphite full cells with 4.2 and 4.4 V upper cutoff voltages were first compared. Cells with a 4.2 V upper cutoff voltage had good cycling stability, exhibiting a capacity retention of 96.8% after 100 cycles and generated little gas. On the other hand, cells with a 4.4 V upper cutoff voltage lost over 25% of initial capacity after 100 cycles and generated large amounts of gas in the first 10 cycles. Electrochemical cycling of anode and cathode symmetric cells was implemented to isolate gases formed at the electrode. Gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy were used to characterize the gas formation and associated material surfaces and structural properties. It was found that CO2 and fluorinated alkanes were the dominant gases evolved on the cathode side during cycling to 4.4 V. Gas crossover to the anode led to the depletion of gaseous products, which stabilized the cell performance to some extent. However, the growing surface reconstruction layer at the cathode, the thickening of the solid electrolyte interphase layer at the anode, and the gradual depletion of lithium inventory collectively contributed to the continuous capacity loss of full cells cycled to 4.4 V.

NMR Study of the Degradation Products of Ethylene Carbonate in Silicon-Lithium Ion Batteries.

Ethylene carbonate (EC) is the most widely used electrolyte solvent in lithium ion batteries, but it fails to form a stable passivation layer on materials such as Si and Li metal, which will enable the long-term cycling of the next-generation high-capacity lithium ion batteries containing these anode materials. High concentrations of soluble degradation products are detected in the electrolyte after prolonged cycling, but the chemical structures of these species remain unclear. Here, we used 1D, 2D, and diffusion NMR techniques combined with mass spectrometry to analyze electrolyte-containing 13C-labeled EC, and we report on the formation of a series of linear oligomers consisting of ethylene oxide and carbonate fragments with methoxide end groups as the major soluble degradation products of EC. Oligomers with methoxide terminals are likely to have weak interaction toward the electrode; thus, they easily detach from the electrode and are unable to passivate the surface, which may explain the origin of the capacity fade for high-capacity Si-based or Li metal anodes.

Dislocation based stresses during electrochemical cycling and phase transformation in lithium-ion batteries

Lithium iron phosphate (LiFePO4) contains defects that play an important role in structural degradation of batteries. Linear defects called dislocations are introduced inside the lithium ion battery material during fabrication process accompanied by distortion produced stress fields around them. The present study deals with these mechanical stresses around dislocations in lithium iron phosphate and the change in stress field during phase transformation of lithium iron phosphate electrode material. A model consisting of multiple dislocations inside a lithium iron phosphate material incorporating anisotropic material properties is used to calculate stress fields using linear elastic theory and the superposition method. The stress fields around dislocations during phase transformation of lithium-iron phosphate are numerically calculated by incorporating the anisotropic properties of the material. The change in electrochemical behaviour of material due to change in stress field during phase transformation is also studied, where a modified electrochemical kinetics equation (i.e., Butler Volmer equation) is derived and used to account for dislocation induced stresses during the reversible cyclic voltammatery of the lithium iron phosphate. The results shows the stress inside material does not remain constant during phase transformation and its variations are dislocation orientation dependent. In addition, the result shows that the presence of stress fields around dislocations changes the electrochemical behaviour of the material as suggested by the shift in the cyclic voltammograms. The effect of increasing scan rate on cyclic voltammogram is also studied for lithium iron phosphate. The results show that the increase in current at peaks is independent of the orientation of dislocations studied. Moreover, the decrease in current corresponding to a particular overvoltage value before anodic peak and increase in current after the anodic peak is found to be somehow proportional to the scan rate. Increased scan rates show increased deviation of current from a cyclic voltammogram for material in which there is no phase transformation. The results provide an insight into how presence of defects and phase transformation changes the electrochemical behaviour of the material. It is concluded that the combined effect of the stresses induced around dislocations during phase transformation and high scan rate can be used for modifying battery materials for various applications by changing electrochemistry of electrodes. The present study incorporates electrochemistry, defects and phase transformation into one battery chemistry and thus is important in our understanding of the Li-ion batteries.

Structural Degradation of Cu Current Collector During Electrochemical Cycling of Sn-Based Lithium-Ion Batteries

It is an open question whether there exists structural degradation of current collectors, which likely can lead to the capacity loss of lithium-ion batteries. In this work, we investigate the cycling-induced structural degradation/damage of the Cu current collector used in Sn-based lithium half cells. Electrochemical cycling causes the formation of a layer of porous structure even after the first cycle and the formation of Li2SnCu. The thickness of the porous structure increases with the increase of the cycle number, and local separation between the porous layer and the “solid” Cu layer occurs after prolonged cycling. The nominal contact moduli of the porous layers formed after one and five electrochemical cycles are slightly larger than the pristine Cu current collector. For the porous layers formed after twenty or more electrochemical cycles, the normal contact modulus is generally less than the pristine Cu. The indentation hardnesses of the porous structures are generally less than the pristine Cu except for the porous structure formed after five electrochemical cycles.

Dicyanobenzoquinone Functionalized Carbon Nanotubes As Cathode Materials for Rechargeable Lithium and Sodium Ion Batteries

Currently, lithium ion batteries (LIBs) and sodium ion batteries (SIBs) mainly depend on inorganic cathode materials, which are still plagued by several issues restricting their advancement such as power density, sustainability, and safety. As alternatives, organic electrode materials have been intensively investigated for both LIBs and SIBs due to their advantages of sustainability, flexibility of structure design and environmental friendliness. Among them, organic quinone materials offer a sustainable approach for electric energy storage, however, their intrinsic electrical insulation and dissolution into the electrolyte during cycling have hampered their wide application. To tackle these two issues, we have synthesized novel organic cathode materials by anchoring a quinone compound, 2,3-dicyano-p-benzoquinone (DCBQ) with a high redox potential of 3.37 V vs. Li/Li+, onto carbon nanotubes (CNTs) (CNTs-DCBQ) through a facile ‘‘grafting to’’ method. The elaborate combination of excellent electron conductivity and large surface area of CNTs and stable and reversible redox reaction of DCBQ enables CNTs-DCBQ delivering high reversible capacities of 206.9 and 175.8 mA h g-1 at a current density of 10 mA g-1 and also remarkable capacities of 110.2 and 82.1 mA h g-1 at a higher current density of 200 mA g-1 with a capacity retention approaching 100 % after 1000 cycles for lithium and sodium ion batteries, respectively.

Insights from a Comprehensive Commercial Lithium Ion Battery Cycling and Aging Study

The single largest barrier to adoption of electrochemical storage in the grid is often stated to be the value of a battery over the life of the system. To ensure long-term system safety and reliability, batteries must be selected based on application specific requirements and performance characteristics. Our approach to addressing the uncertainty in the performance and cycle life of commercially viable lithium ion batteries for grid storage has been to design studies with multiple chemistries, and conduct long term life cycle evaluations with systematically varied cycling conditions. Namely, we initiated a large-scale, multi-year cycling study of commercial LiFePO4/LFP, LiNixCoyAl1-x-y­O2/NCA, and LiNixMnyCo1-x-yO2/NMC cells. This study looks at chemistry specific influences on efficiency and cycle life under variables that include discharge rate, depth of discharge (DoD) and temperature, and is complemented by a calendar aging study. The source of differences in aging behavior was investigated through electrochemical impedance spectroscopy and differential capacity analysis. We compare results to literature to identify the degree to which variations may be expected with manufacturer and version, as products can see manufacturing changes year to year. Understanding variations is critical for lifetime assessment and economic evaluation that is meaningful for installed systems. We further look at how these best-case scenario results from single cell studies may be used as a baseline in moving toward understanding aging in module and system configurations. The overarching goal is to begin to effectively understand laboratory cell studies in a context applicable to grid storage systems.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Synthesis and Electrochemical Performance of ZnSe Electrospinning Nanofibers as an Anode Material for Lithium Ion and Sodium Ion Batteries.

ZnSe nitrogen-doped carbon composite nanofibers (ZnSe@N-CNFs) were derived as anode materials from selenization of electrospinning nanofibers. Electron microscopy shows that ZnSe nanoparticles are distributed in electrospinning nanofibers after selenization. Electrochemistry tests were carried out and the results show the one-dimensional carbon composite nanofibers reveal a great structural stability and electrochemistry performance by the enhanced synergistic effect with ZnSe. Even at a current density of 2 A g−1, the as-prepared electrodes can still reach up to 701.7 mA h g−1 after 600 cycles in lithium-ion batteries and 368.9 mA h g−1 after 200 cycles in sodium-ion batteries, respectively. ZnSe@N-CNFs with long cycle life and high capacity at high current density implies its promising future for the next generation application of energy storage.

Structural evolutions of LiNi0.5Mn1.5O4 nanorods synthesized by different lithium sources and effects on electrochemical performances

It is crucial to prepare the material LiNi0.5Mn1.5O4 (LNMO) with good cycling and rate performances for lithium-ion batteries. The growing process of LNMO nanorods with different lithium sources was investigated with β-MnO2 nanofibers as the templates, and Li(CH3COO)·2H2O and LiOH·H2O as lithium sources respectively. The structures and morphologies of the LNMO samples were characterized by XRD, FTIR, Raman, SEM, and TEM. Results show that by taking Li(CH3COO)·2H2O as the lithium source, the LNMO nanorods grow slowly. The nanorod structure can be maintained in a larger range of annealing temperature (700–750 °C). XRD analysis results show that the nanocrystalline of LNMO synthesized by Li(CH3COO)·2H2O as lithium source is smaller and with lower disorder degree than that synthesized by LiOH·H2O as the lithium source under the same annealing temperatures. The LNMO synthesized by Li(CH3COO)·2H2O as lithium source performed better rate and cycling performances attributed to smaller polarization effect, which was confirmed by the CV results. EIS test data implied that the LNMO samples synthesized by Li(CH3COO)·2H2O as the lithium sources presented smaller charge transfer resistances. Consequently, Li(CH3COO)·2H2O is an ideal lithium source to control the disorder degree and growing process of LNMO nanorods.

Two-Dimensional Bismuth Oxide Heterostructured Nanosheets for Lithium- and Sodium-Ion Storages.

Two-dimensional (2D) bismuth oxide (Bi2O3) heterostructured nanosheets (BOHNs) were first fabricated by a solution-based molecular self-assembly approach. The synthesized BOHNs nanosheets feature mixed α- and β-phases and rich surface/edge-active sites. When utilized as anode materials for rechargeable batteries, dual-phase BOHNs deliver an initial discharge capacity as high as 647.6 mAh g-1 and an increased capacity of over 200 mAh g-1 remained after 260 cycles for lithium-ion batteries (LIBs), and a stable cycling capacity at ∼50 mAh g-1 after 500 cycles for sodium-ion batteries (SIBs). A novel flexible 2D/1D/2D structure is further developed by implanting 2D BOHNs into conductive 1D carbon nanotubes and 2D graphene to form composite (BOHNCG) paper as free-standing anodes for both LIBs and SIBs. The capacity of 2D/1D/2D BOHNCG as a LIB anode reaches 823.5 mAh g-1, corresponding to an enhancement of ∼27%, and remains at >110 mAh g-1 after 80 cycles as a SIB anode with greatly improved cycling stability. This work verifies the promising potential of 2D BOHNs for practical energy-related devices and enriches the current research on emerging 2D nanomaterials.

Few-layer graphene coated current collectors for safe and powerful lithium ion batteries

In the fabrication of safe, but powerful lithium ion batteries (LIBs), graphene-related materials are being actively examined in order to meet the demand for applications such as electric vehicles and smart grids. However, most of this work has focused on liquid-phase exfoliated graphene and reduced graphene oxide. Herein, we demonstrate a simple, but effective route for significantly improving the electrochemical performance of currently available LIBs by coupling current collector with catalytically grown large-area graphene. When coating current collectors with large-area three-layered graphene, a reduction in the internal resistance (or effective electron transfer) between the current collector and active materials was observed. The graphene also protected the underlying collector from corrosion, greatly improving the power capability and cyclability of LIBs. The three-layered graphene provided the best electrochemical performance and corrosion resistance because of its high electrical conductivity and mechanical stability during the transfer process. We believe that our approach using interfacial graphene coating can be used with all kinds of electrochemical energy-storage systems, in which high corrosion resistance, electrical conductivity, and flexibility are critical.

Recent Progress of Graphene as Cathode materials in Lithium Ion Batteries

Graphene, composed by one-atom-thick planar sheet with sp2 bonded carbon atoms, which is regarded as the basis for all fullerene allotropic forms. Its combination with electrode materials (LiFePO4, LiMn2O4, etc.) could dramatically increase the electrochemical performance of the rechargeable battery system. With relative poor rate capability, charge capacity, and cyclability of lithium ion batteries, this review analyses the prospects of graphene materials serve as lithium ion battery electrodes to meet such demands. Some important advances have been summarized, ranging from the synthesis of graphene-based lithium ion battery electrodes to their properties and underlying principles for electrochemical improvement of such materials.

Improved capacity and cycling stability of SnO2 nanoanode induced by amorphization during cycling for lithium ion batteries

Conversion reactions of SnO2-based anode materials have recently been confirmed reversible by using well-designed nanostructures, while the detailed mechanism during charging and discharging is still ambiguous. Unwrapping the real mechanism is helpful to design high-performance SnO2-based anode materials. In this work, we designed and fabricated a nanoarchitecture of ultrafine SnO2 (3–5 nm) anchored on the surfaces of carbon nanofibers (denoted as u-TOCNFs). The u-TOCNFs electrode exhibits high reversible capacity of 1006.4 mAh·g−1, high initial Coulombic efficiency of 71.3% and good cycle stability mainly due to good dispersion of ultrafine SnO2 on the conductive carbon nanofibers. The structure evolution is investigated by TEM observations that confirm the presence of amorphous SnO2 on the delithiated nanoanode at 1.28 V after 100 cycles. Charge/discharge induced amorphization of SnO2 nanocrystals is firstly observed that readily explain the capacity increasing around 100 cycles. In particular, we propose the mechanism of reversible conversion reactions of SnO2 and Sn induced by the amorphization of ultrafine SnO2 during lithiation/delithiation. We believe that it is a new direction to study SnO2-based anode materials to improve the electrochemical performance for lithium ion batteries.

Sb2S3 embedded in carbon–silicon oxide nanofibers as high-performance anode materials for lithium-ion and sodium-ion batteries

Based on the conversion and alloying reactions, antimony sulfide (Sb2S3) with a theoretical discharge specific capacity of 946 mAh g−1 is a hopeful anode material for lithium/sodium ion batteries. Nevertheless, the poor electronic conductivity of Sb2S3 and the serious volume expansion during alloying reaction bring about the rapid capacity fading, which severely hinder its practical application. The design of morphology/structure and/or combining with carbon materials is the common strategies to address these issues. Herein, a simple electrospinning technology coupled with hydrothermal reaction is employed to synthesize the Sb2S3/carbon-silicon oxide (Sb2S3/CS) nanofibers for the first time. The obtained Sb2S3/CS nanofibers show superior lithium/sodium storage properties. Specifically, the Sb2S3/CS electrode maintains a high discharge specific capacity of 566 mAh g−1 under 200 mA g−1 after 200 cycles in lithium-ion batteries. For sodium storage, the Sb2S3/CS electrode obtains a discharge specific capacity of 321 mAh g−1 under 200 mA g−1 over 200 cycles. One-dimensional Sb2S3/CS nanofibers with good electronic conductivity accelerate the transport of ions and electrons, and effectively buffer the volume change of Sb2S3 nanoparticles during electrochemical reaction process, bringing about the excellent electrochemical properties.

Kerr Gated Raman Spectroscopy to Investigate Lithium-Ion Battery Interfaces

Fluorescent species are formed during cycling of lithium ion batteries as a result of electrolyte decomposition due to the instability of the non-aqueous electrolytes and side reactions that occur at the electrode surface. The increase in the background fluorescence due to the presence of these components makes it harder to analyse data due to the spectroscopic overlap of Raman scattering and fluorescence. In this talk we will demonstrate that Kerr gate Raman is an effective technique for the isolation of the scattering effect from the fluorescence enabling the collection of the Raman spectra of Li-ion electrolyte materials, without the interference of the fluorescence component. In particular we will present proof-of-concept experiments that the background fluorescence emission in the scattering spectrum of LiPF6 as salt and in the conventional battery electrolyte with ethylene carbonate: dimethyl carbonate solvents can be minimised or suppress by Kerr gated Raman. It was possible to detect degradation products resulting from the decomposition of LiPF6, which has not previously been observed by Raman scattering due to the fluorescence emission. It was also possible to investigate the reactivity of LiPF6 against decomposition in the electrolyte is slower than as with the pure salt.

Hierarchical flower-like Fe2O3 mesoporous nanosheets with superior electrochemical lithium storage performance

Abstract In order to satisfy the requirement of high energy density and long cyclability for lithium-ion batteries, Fe2+ self-doped hierarchical flower-like mesoporous Fe2O3 nanosheets with a high specific surface area of 120.57 m2 g−1 are prepared through ultrafast microwave assisted systhesis and post calcination. The obtained Fe2O3 exhibits a superior electrochemical performance on lithium storage (2000 mA h g-1 at 400 mA g-1 up to 300 cycles and 1750 mA h g−1 at 1 A g-1 even up to 1000 cycles) and excellent cycling stability, which are likely to be associated with the specific structure and increased electronic conductivity contributed from Fe2+ defects. These findings not only enormously improve the electrochemical property of Fe2O3 anode, but offer a new perspective for designing of distinctive nanomaterials for various energy devices.

Dynamic imaging of crystalline defects in lithium-manganese oxide electrodes during electrochemical activation to high voltage

Crystalline defects are commonly generated in lithium-metal-oxide electrodes during cycling of lithium-ion batteries. Their role in electrochemical reactions is not yet fully understood because, until recently, there has not been an effective operando technique to image dynamic processes at the atomic level. In this study, two types of defects were monitored dynamically during delithiation and concomitant oxidation of oxygen ions by using in situ high-resolution transmission electron microscopy supported by density functional theory calculations. One stacking fault with a fault vector b/6[110] and low mobility contributes minimally to oxygen release from the structure. In contrast, dissociated dislocations with Burgers vector of c/2[001] have high gliding and transverse mobility; they lead to the formation, transport and release subsequently of oxygen related species at the surface of the electrode particles. This work advances the scientific understanding of how oxygen participates and the structural response during the activation process at high potentials.