Application In Rechargeable Batteries Research Articles

Phase-field modeling of Li-insertion kinetics in single LiFePO4-nano-particles for rechargeable Li-ion battery application

We develop a continuum phase-field model for the simulation of diffusion limited solid-solid phase transformations during lithium insertion in LiFePO4-nano-particles. The solid-solid phase boundary between the LiFePO4 (LFP)-phase and the FePO4 (FP)-phase is modeled as a diffuse interface of finite width. The model-description explicitly resolves a single LiFePO4-particle, which is embedded in an elastically soft electrolyte-phase. Furthermore, we explicitly include anisotropic (orthorhombic) and inhomogeneous elastic effects, resulting from the coherency strain, as well as anisotropic (1D) Li-diffusion inside the nano-particle. In contrast to other related research work, we employ an Allen-Cahn-type phase-field approach for the diffuse interface modeling of the solid-solid phase boundary. The model contains an extra non-conserved order parameter field to distinguish the two different phases. The evolution of this order parameter field is controlled by an extra kinetic parameter independent from the Li-diffusion. Further, the effect of the nano-particle’s size on the kinetics of FP to LFP phase transformations is investigated by means of both model. Both models predict a substantial increase in the steady state transformation velocity as the particle-size decreases down to dimensions that are comparable with the width of the interface between the FP and the LFP-phase. However, the extra kinetic parameter of the Allen-Cahn-type description may be used to reduce the strength of the velocity-increase with the decreasing particle size. Further, we consider the influence of anisotropic and inhomogeneous elasticity on the lithiation-kinetics within a rectangularly shaped LiFePO4-particle embedded in an elastically soft electrolyte. Finally, the simulation of equilibrium shapes of LiFePO4-particles is discussed. Within a respective feasibility study, we demonstrate that also the simulation of strongly anisotropic particles with aspect ratios up to 1/5 is possible.

Preparation of poly (bis[2-(methacryloyloxy)ethyl] phosphate) crosslinked polymer brushes on Poly(vinylidene fluoride) nanofibers

In this study, a surface modification of poly(vinylidene fluoride) (PVDF) nanofibers by atom transfer radical polymerization (ATRP) was developed to form bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) crosslinked polymer brushes grafted on nanofibers for application in rechargeable lithium batteries. BMEP was polymerized by using a “grafting-from” technique on the PVDF nanofiber surface by direct initiation. FT-IR (Fourier transform infrared) spectroscopy and SEM (scanning electron microscopy) confirmed the formation of BMEP polymer brushes. Morphological analysis showed that the diameter of the nanofibers was increased by surface grafting. Nevertheless, the characteristic nanofibrillar structure was not changed significantly by ATRP. The thermal properties of the nanofibers were investigated by TGA (thermogravimetric analysis). The results showed that the thermo-oxidative stability of the nanofibers increased with the BMEP content. The conductivities of Li-salts containing nanofibers were in the range 3.41 × 10−3 S cm−1 to 8.26 × 10−4 S cm−1.

Dendrite-Free Sodium-Metal Anodes for High-Energy Sodium-Metal Batteries.

Sodium (Na) metal is one of the most promising electrode materials for next-generation low-cost rechargeable batteries. However, the challenges caused by dendrite growth on Na metal anodes restrict practical applications of rechargeable Na metal batteries. Herein, a nitrogen and sulfur co-doped carbon nanotube (NSCNT) paper is used as the interlayer to control Na nucleation behavior and suppress the Na dendrite growth. The N- and S-containing functional groups on the carbon nanotubes induce the NSCNTs to be highly "sodiophilic," which can guide the initial Na nucleation and direct Na to distribute uniformly on the NSCNT paper. As a result, the Na-metal-based anode (Na/NSCNT anode) exhibits a dendrite-free morphology during repeated Na plating and striping and excellent cycling stability. As a proof of concept, it is also demonstrated that the electrochemical performance of sodium-oxygen (Na-O2 ) batteries using the Na/NSCNT anodes show significantly improved cycling performances compared with Na-O2 batteries with bare Na metal anodes. This work opens a new avenue for the development of next-generation high-energy-density sodium-metal batteries.

Impacts of the Properties of Anode Solid Electrolyte Interface on the Storage Life of Li-Ion Batteries

Storage life is critically important in applications of rechargeable batteries. The Li loss in graphite is the main cause during storage aging at a full state of charge while the solid electrolyte interface on the graphite acts as a protective layer to restrain the Li loss during aging. Focusing on the initial SEI electronic resistance as the rate-limiting factor during the aging progress, we investigated the properties of the SEIs formed under varied conditions. The main SEI components and corresponding electronic conductivity were analyzed, while the thicknesses of initial SEIs were estimated at the same time. The storage performance results confirmed that cells with high electronic resistance SEIs would have extended storage lifespan, but the performance should be based on well-formed SEIs. Cells with incomplete SEIs would have accelerated capacity loss rate during storage aging.

(Invited) Guided Growth and Smooth Deposition of Lithium Metal Film through Electrolyte Strategy

Lithium (Li) metal batteries have been regarded as the most promising candidate for next generation energy storage because Li metal as anode has extremely high theoretical specific capacity (3860 mAh g-1), the lowest negative electrochemical potential (-3.040 V vs. the standard hydrogen electrode) and low density (0.534 g cm-3). However, the safety concerns and the short cycle life due to Li dendrite growth and low Coulombic efficiency (CE) hinder the development and practical applications of rechargeable Li metal batteries. During the past four decades, several approaches have been reported to suppress the Li dendrite growth and improve the stability of Li metal anode, including using Li alloys, solid-state electrolytes, polymer electrolytes, ionic liquids, highly concentrated liquid electrolytes, additives, protecting layers, interlayers between Li and separator, nanoscale design, selective deposition, Li-reduced graphene oxide composites, and so on. However, the improvement on Li anode as far is still unsatisfactory. In the past six years, we at PNNL systematically investigated various strategies to suppress Li dendrite growth, increase Li CE and enhance Li structural stability through electrolyte formulations, separator modifications, 3D structured Li hybrid anodes, and so on. In this talk, the electrolyte strategy to guide uniform growth and to form smooth deposition of Li metal film will be discussed and the details of the investigations will be reported at the presentation. Acknowledgement The research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy (DOE) through the Advanced Battery Materials Research (BMR) Program. Figure 1

Bayesian-Driven First-Principles Calculations for Accelerating Exploration of Fast Ion Conductors for Rechargeable Battery Application

Safe and robust batteries are urgently requested today for power sources of electric vehicles. Thus, a growing interest has been noted for fabricating those with solid electrolytes. Materials search by density functional theory (DFT) methods offers great promise for finding new solid electrolytes but the evaluation is known to be computationally expensive, particularly on ion migration property. In this work, we proposed a Bayesian-optimization-driven DFT-based approach to efficiently screen for compounds with low ion migration energies ({{boldsymbol{E}}}_{{boldsymbol{b}}}{boldsymbol{)}}. We demonstrated this on 318 tavorite-type Li- and Na-containing compounds. We found that the scheme only requires ~30% of the total DFT-{{boldsymbol{E}}}_{{boldsymbol{b}}} evaluations on the average to recover the optimal compound ~90% of the time. Its recovery performance for desired compounds in the tavorite search space is ~2× more than random search (i.e., for {{boldsymbol{E}}}_{{boldsymbol{b}}} < 0.3 eV). Our approach offers a promising way for addressing computational bottlenecks in large-scale material screening for fast ionic conductors.

Cobalt phosphide microsphere as an efficient bifunctional oxygen catalyst for Li-air batteries

An efficient bifunctional catalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desired for the application of rechargeable metal air batteries. Herein, urchin-like CoP microspheres have been synthesized by a facile hydrothermal method with cetrimonium bromide as soft template. In alkaline solution, the as-prepared CoP catalyzes the ORR with an onset potential of −0.11 V (vs. Ag/AgCl) and a potential gap of 62 mV compared with commercial Pt/C catalyst. Meanwhile, the CoP catalyst exhibits better OER activities than the commercial RuO2 catalyst. Interestingly, when employed as cathodic catalyst for Li-air batteries, the battery shows good discharge capacity of 2994 mAh g−1 at 100 mA g−1, high round-trip efficiency of over 90%, excellent rate capability and cycle stability of sustaining 80 cycles without any capacity degradation at a high discharge current density of 500 mA g−1.

Surface modification of natural vein graphite for the anode application in Li-ion rechargeable batteries

Natural vein graphite with high purity and crystallinity is seldom used as anode material in lithium-ion rechargeable batteries (LIB) due to impurities and inherent surface structure. This study focuses on improving the surface properties of purified natural vein graphite surface by employing mild chemical oxidation. Needle-platy graphite sample with initial average carbon percentage of 99.83% was improved to 99.98% after treatment with 5 vol.% HCl. Surface modification of purified graphite was done by chemical oxidation with (NH4)(2)S2O8 and HNO3. Fourier-transform infrared spectra of graphite after chemical indicating surface oxidation of graphite surface. X-ray diffraction and scanning electron microscopic studies show the improvement of graphite structure without modification of crystalline structure. Electrochemical performance of lithium-ion cell assembled with developed anode material shows noticeable improvement of the reversible capacity and coulombic efficiency in the first cycle and cycling behavior after surface modification.

Enhanced Stability of Lithium Metal Anode by using a 3D Porous Nickel Substrate

AbstractLithium (Li) metal is considered as the “holy grail” anode for high energy density batteries, but its applications in rechargeable Li metal batteries are still hindered by the formation of Li dendrites and low coulombic efficiency for Li plating/stripping. An effective strategy to stabilize Li metal is to embed a Li metal anode in a three‐dimensional (3D) current collector. Here, a highly porous 3D Ni substrate is reported to effectively stabilize a Li metal anode. By using a galvanostatic intermittent titration technique combined with scanning electron microscopy, the underlying mechanism of the improved stability of the Li metal anode is revealed. It is clearly demonstrated that the porous 3D Ni substrate can effectively suppress the formation of “dead” Li and support the generation of a dense surface passivation layer, while a highly porous “dead” Li layer is accumulated on the two‐dimensional (2D) Li metal, which eventually limits mass transport. X‐ray photoelectron spectroscopy results further reveal the compositional differences in the solid‐electrolyte interphase layer formed on the Li metal embedded in the porous 3D Ni substrate and the 2D Li metal substrate. These results indicate that the use of 3D conductive host is critical for the long‐term stability of Li metal batteries.

Synthesis and characterization of electrospun molybdenum dioxide-carbon nanofibers as sulfur matrix additives for rechargeable lithium-sulfur battery applications.

One-dimensional molybdenum dioxide–carbon nanofibers (MoO2–CNFs) were prepared using an electrospinning technique followed by calcination, using sol–gel precursors and polyacrylonitrile (PAN) as a processing aid. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmet–Teller (BET) surface area measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MoO2–CNFs with an average diameter of 425–575 nm obtained after heat treatment were used as a matrix to prepare sulfur/MoO2–CNF cathodes for lithium–sulfur (Li–S) batteries. The polysulfide adsorption and electrochemical performance tests demonstrated that MoO2–CNFs did not only act as polysulfide reservoirs to alleviate the shuttle effect, but also improve the electrochemical reaction kinetics during the charge–discharge processes. The effect of MoO2–CNF heat treatment on the cycle performance of sulfur/MoO2–CNFs electrodes was examined, and the data showed that MoO2–CNFs calcined at 850 °C delivered optimal performance with an initial capacity of 1095 mAh g−1 and 860 mAh g−1 after 50 cycles. The results demonstrated that sulfur/MoO2–CNF composites display a remarkably high lithium–ion diffusion coefficient, low interfacial resistance and much better electrochemical performance than pristine sulfur cathodes.

Extremely Stable Sodium Metal Batteries Enabled by Localized High-Concentration Electrolytes

Sodium (Na) metal is a promising anode for Na-ion batteries. However, the high reactivity of Na metal with electrolytes and the low Na metal cycling efficiency have limited its practical application in rechargeable Na metal batteries. High-concentration electrolytes (HCE, ≥4 M) consisting of sodium bis(fluorosulfonyl)imide (NaFSI) and ether solvent could ensure the stable cycling of Na metal with high Coulombic efficiency but at the cost of high viscosity, poor wettability, and high salt cost. Here, we report that the salt concentration could be significantly reduced (≤1.5 M) by a hydrofluoroether as an “inert” diluent, which maintains the solvation structures of HCE, thereby forming a localized high-concentration electrolyte (LHCE). A LHCE [2.1 M NaFSI/1,2-dimethoxyethane (DME)–bis(2,2,2-trifluoroethyl) ether (BTFE) (solvent molar ratio 1:2)] enables dendrite-free Na deposition with a high Coulombic efficiency of >99%, fast charging (20C), and stable cycling (90.8% retention after 40 000 cycles) of Na∥Na...

Ion conducting behaviour of silsesquioxane-based materials used in fuel cell and rechargeable battery applications

Ion conducting behaviour of silsesquioxane-based materials used in fuel cell and rechargeable battery applications

Preparation of MoS2/TiO2 based nanocomposites for photocatalysis and rechargeable batteries: progress, challenges, and perspective.

The rapidly increasing severity of the energy crisis and environmental degradation are stimulating the rapid development of photocatalysts and rechargeable lithium/sodium ion batteries. In particular, MoS2/TiO2 based nanocomposites show great potential and have been widely studied in the areas of both photocatalysis and rechargeable lithium/sodium ion batteries due to their superior combination properties. In addition to the low-cost, abundance, and high chemical stability of both MoS2 and TiO2, MoS2/TiO2 composites also show complementary advantages. These include the strong optical absorption of TiO2vs. the high catalytic activity of MoS2, which is promising for photocatalysis; and excellent safety and superior structural stability of TiO2vs. the high theoretic specific capacity and unique layered structure of MoS2, thus, these composites are exciting as anode materials. In this review, we first summarize the recent progress in MoS2/TiO2-based nanomaterials for applications in photocatalysis and rechargeable batteries. We highlight the synthesis, structure and mechanism of MoS2/TiO2-based nanomaterials. Then, advancements and strategies for improving the performance of these composites in photocatalytic degradation, hydrogen evolution, CO2 reduction, LIBs and SIBs are critically discussed. Finally, perspectives on existing challenges and probable opportunities for future exploration of MoS2/TiO2-based composites towards photocatalysis and rechargeable batteries are presented. We believe the present review would provide enriched information for a deeper understanding of MoS2/TiO2 composites and open avenues for the rational design of MoS2/TiO2 based composites for energy and environment-related applications.

Multifunctional nanostructured electrocatalysts for energy conversion and storage: current status and perspectives.

Electrocatalytic oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have attracted widespread attention because of their important role in the application of various energy storage and conversion devices, such as fuel cells, metal-air batteries and water splitting devices. However, the sluggish kinetics of the HER/OER/ORR and their dependency on expensive noble metal catalysts (e.g., Pt) obstruct their large-scale application. Hence, the development of efficient and robust bifunctional or trifunctional electrocatalysts in nanodimension for both oxygen reduction/evolution and hydrogen evolution reactions is highly desired and challenging for their commercialization in renewable energy technologies. This review describes some recent developments in the discovery of bifunctional or trifunctional nanostructured catalysts with improved performances for application in rechargeable metal-air batteries and fuel cells. The role of the electronic structure and surface redox chemistry of nanocatalysts in the improvement of their performance for the ORR/OER/HER under an alkaline medium is highlighted and the associated reaction mechanisms developed in the recent literature are also summarized.

Hierarchical Core-Shell Nickel Cobaltite Chestnut-like Structures as Bifunctional Electrocatalyst for Rechargeable Metal-Air Batteries.

Nano-engineered hierarchical core-shell nickel cobaltite chestnut-like structures were successfully synthesized as a bifunctionally active electrocatalyst for rechargeable metal-air battery applications. Both the morphology and composition of the catalyst were optimized by a facile hydrothermal reaction, resulting in a 10 h reacted sample demonstrating significantly enhanced activity toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in 0.1 m KOH. Specifically, the catalyst demonstrated -0.28 and 0.60 V versus SCE (saturated calomel electrode) at the ORR half-wave potential and an OER current density of 10 mA cm-2 , respectively. The resulting ORR/OER potential difference of 0.90 V was the smallest compared to the catalysts synthesized using 2, 6, and 12 h of hydrothermal reaction time. The excellent bifunctional activity of the catalyst is attributed to the nanoscale porous morphology and the spinel nickel cobaltite composition, which improved the active site exposure and transport of reactants and charges during the oxygen reactions.

Boosting Bifunctional Oxygen Electrocatalysis with 3D Graphene Aerogel-Supported Ni/MnO Particles.

Electrocatalysts for oxygen-reduction and oxygen-evolution reactions (ORR and OER) are crucial for metal-air batteries, where more costly Pt- and Ir/Ru-based materials are the benchmark catalysts for ORR and OER, respectively. Herein, for the first time Ni is combined with MnO species, and a 3D porous graphene aerogel-supported Ni/MnO (Ni-MnO/rGO aerogel) bifunctional catalyst is prepared via a facile and scalable hydrogel route. The synthetic strategy depends on the formation of a graphene oxide (GO) crosslinked poly(vinyl alcohol) hydrogel that allows for the efficient capture of highly active Ni/MnO particles after pyrolysis. Remarkably, the resulting Ni-MnO/rGO aerogels exhibit superior bifunctional catalytic performance for both ORR and OER in an alkaline electrolyte, which can compete with the previously reported bifunctional electrocatalysts. The MnO mainly contributes to the high activity for the ORR, while metallic Ni is responsible for the excellent OER activity. Moreover, such bifunctional catalyst can endow the homemade Zn-air battery with better power density, specific capacity, and cycling stability than mixed Pt/C + RuO2 catalysts, demonstrating its potential feasibility in practical application of rechargeable metal-air batteries.

Synthesis and characterization of novel polyindole/metal oxide nanocomposites and its evaluation for lithium ion rechargeable battery applications

Two novel conducting polyindole (PIn) based on γ‐Fe2O3 and γ‐Al2O3 nanocomposites with LiClO4 on Au electrode (Au/PIn/ @γ‐Al2O3 and Au/PIn/ @γ‐Fe2O3) as cathode materials for lithium‐ion rechargeable batteries were fabricated via an in situ electropolymerization approach. The PIn and polymer nanocomposites were characterized by FT‐IR, SEM, TEM, EDX, and TGA. The electrochemical properties of PIn and polymer nanocomposites were studied by cyclic voltammetry (CV), in situ conductivity measurements, electrochemical impedance spectroscopy and charge–discharging test. The optical properties of the samples were also investigated by in situ UV‐Visible spectroscopy. The CV results show better reversibility for polymer nanocomposites in compered PIn. The intermolecular interaction between nanoparticles and PIn were confirmed by FT‐IR. The TEM images of polymer nanocomposites show that γ‐Fe2O3 and γ‐Al2O3 are embedded in PIn matrix. The thermal stability of the polymer nanocomposites has increased compared to that of PIn. The in situ conductivity of polymer nanocomposites were increased at about 0.20 order of magnitudes in compared to PIn. The electrochemical properties and charge–discharging behavior of the materials were measured with Li/LiClO4+ACN/Au‐PIn, Li/LiClO4+ACN/Au‐PIn‐γ‐Al2O3, and Li/LiClO4+ACN/Au‐PIn‐γ‐Fe2O3 cells using a constant current of 0.5 mA/cm2. The results for polymer nanocomposites cells indicated better discharging characteristics at about 116–124 mAh/g with very good cyclic properties in compered to PIn cell. The discharge capacities achieve the best value after 30–40 cycles with around drops 3–6% after 20,000 times. POLYM. COMPOS., 40:496–505, 2019. © 2017 Society of Plastics Engineers

Ultrastable α phase nickel hydroxide as energy storage materials for alkaline secondary batteries

α Phase nickel hydroxide (α-Ni(OH)2) has higher theoretical capacity than that of commercial β phase Ni(OH)2. But the low stability inhibits its wide application in alkaline rechargeable batteries. Here, we propose a totally new idea to stabilize α phase Ni(OH)2 by introducing large organic molecule into the interlayer spacing together with doping multivalent cobalt into the layered Ni(OH)2 host. Ethylene glycol is served as neutral stabilizer in the interlayer spacing. Nickel is substituted by cobalt to increase the electrostatic attraction between layered Ni(OH)2 host and anion ions in the interlayer spacing. Polyethylene glycol (PEG-200) is utilized to design a three-dimensional network structure. This prepared α-Ni(OH)2-20 exhibits specific capacity as high as 334 mAh g−1and good structural stability even after immersing into strong alkaline zincate solution for 20 days. Ni(OH)2 electrode with a specific capacity of 35 mAh cm−2 is fabricated and used as positive electrode in zinc-nickel single flow batteries, which also shows good cycling stability. This result can provide an important guideline for the rational design and preparation of highly active and stable α phase Ni(OH)2 for alkaline secondary battery.

Polyethylene separators modified by ultrathin hybrid films enhancing lithium ion transport performance and Li-metal anode stability

Poor stability of lithium metal anodes in liquid electrolytes hinders its practical application in rechargeable batteries with very high energy density. Herein, we present an approach to tackle the intrinsic problems of Li metal anodes from the standpoint of separators. By a facile and versatile method based on mussel-inspired surface chemistry, a hybrid polydopamine/octaammonium POSS (PDA/POSS) coating was spontaneously formed on the surface of PE separators through the self-polymerization and strong adhesion feature of dopamine. This ultrathin PDA/POSS coating endows PE separators with different surface characteristics while keeping its microporous structure almost unchanged. The altered surface characteristics influence the separator/electrolyte interaction, and lead to remarkable enhanced ionic conductivity (from 0.36 mS cm−1 to 0.45 mS cm−1) and Li+ ion transference number (from 0.37 to 0.47) of PE separators as well as the improved stability of lithium/electrolyte interface, which effectively decreases the electrode polarization and suppresses the lithium dendrites formation, contributing to superior C-rates capability and cycling performance of cells.

Stabilized Lithium, Manganese AB2O4 Spinel for Rechargeable Lithium Electrochemical Systems through A and B Site Doping

Lithium manganese oxide doped with potassium and cobalt produces a promising cathode material for rechargeable lithium-ion cells. Modifying the A site and B site of the spinel structure works to limit cathodic capacity fading by enhancing the robustness of the material. LixKyMn2-zCozO4 was synthesized as the active ingredient for the cathode with x=1, y=0.1, and both z=0.1 and 0.2, and was tested against metallic lithium to evaluate performance. Through high-rate discharge, pulse cycling, and deep discharge tests, the electrochemistry of the cathode exhibited excellent reversibility and overall performance stability. LiK0.1Mn2-zCozO4 proved to be a capable abuse tolerant option for use in rechargeable battery applications.