Low Cell Resistance Research Articles

Dual surface-bulk aluminum modification in a-Al2O3@Na3VAl(PO4)3 sodium-ion batteries cathode to boost high voltage utilization and electrolyte protection

Amorphous alumina (a-Al2O3)-coated Na3VAl(PO4)3 samples are prepared by a low-cost, easily scalable, and environmentally friendly sol-gel process. X-ray diffraction reveals no significant structural changes after deposition. The presence of the amorphous carbon conductive and a-Al2O3 phases will be respectively confirmed in the light of Raman and NMR spectroscopies. Electron microscopy evidences the presence of alumina particles deposited on the substrate. Ex-situ XRD shows the reversible structural changes while sodium is inserted. Ex-situ XPS reveals the effective participation of V5+/V4+/V3+ species during the electrochemical reaction, while the formation of aluminum oxyfluorides justifies the efficient HF removal that prevents electrode degradation.Electrochemical tests will validate this proposal. Thus, rate capability essays indicate that 1–3 % a-Al2O3 coating enhances capacity at high rates, with coated samples exhibiting a fast sodium migration and lower cell resistance at both the beginning and conclusion of cycling tests. It is supported by evaluating the kinetic response showing their high capacitive contributions and diffusion coefficients, especially in the 2 % a-Al2O3 coated sample. Eventually, these findings are corroborated by the good capacity retention of the 2 % coated sample during prolonged cycling at both room and low temperatures.

The Effect of Shape in Porous Electrodes on Cell Resistance and Chemo-Mechanical Stresses

In contrast to conventional planar electrodes, the use of electrodes with a three-dimensional (3D) shape has been shown to be an effective way to increase both the power and energy densities of a Li-ion battery. These 3D shapes allow batteries to overcome some of the capacity and rate performance trade-offs. For instance, they enable higher active-material loading, while keeping the transport pathways fixed and allowing for better material utilization. There are a variety of ways electrodes can be shaped: each electrode can be individually shaped and separated by a planar separator, or they can be completely intertwined with one another. In this talk, we consider both cases: a half cell with an electrode shape described by a sine wave and a full cell following an interdigitated design, where alternating planar fins protruding from the cathode and anode sandwich the electrolyte. First, we seek to understand how the electrode shape affects the electrical resistance of the cell based on a simple electrostatics model with a linearized Tafel expression. We identify the regimes of electronic to ionic conductivity ratios, Wagner numbers, and porosities that benefit most from electrode shaping, with a particular focus on low temperature electrolytes with reduced conductivity. Next, battery cycling is known to cause volumetric expansion and contraction of the electrodes. Therefore, we explore the chemo-mechanical stresses that arise in the same shaped electrodes with a solid electrolyte. To do so, we solve for the mechanical equilibrium for stress and deformation in the presence of an applied isotropic strain. By examining the stress concentrations at the electrode/electrolyte interface, we elucidate the likely failure mechanisms – interface delamination, crack propagation – of shaped electrodes in comparison to planar electrodes. Overall, we aim to provide design guidelines for how electrode shapes can be chosen to provide both low cell resistance and acceptable mechanical resilience.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857536.

Liquid Binary and Ternary Electrolytes Mixtures for Low-Temperature Sulfurized Carbon Batteries

Active sulfurized carbon (SC) has been proposed as promising alternative to enable sulfur as the next generation cathode material due its ability to confine sulfur and suppresses polysulfide shuttling. Pragmatic cell performance of SC electrodes needs to extend over a wide range of temperatures from -20 °C to 60 °C. Low-temperature performance of SC cells is mainly limited by electrolyte wettability, ionic mobility between the electrodes, and the nature of the formed solid electrolyte interphase. In this work we have utilized electrolyte binary and ternary mixtures based on carbonates, ethers, and fluorinated solvents to enhance the SC cell discharge performance up to -20 °C. To understand the effects of electrolyte mixtures in the cell performance we have utilized electrochemical impedance spectroscopy (EIS) as a function of temperature and voltage. The lower cell resistance translates into a higher rate capability, cyclability, and low-temperature performance. Based on the EIS response and its spectra deconvolution we proposed an apparent electrical equivalent circuit that permits the elucidation of resistance elements and their magnitude such as the ohmic, electron charge transfer, surface film, and mass transport resistance to provide a phenomenological understanding on how the mixtures can enhance the electrochemical performance. Furthermore, differential capacity analysis and Hybrid Pulse Power Characterization (HPPC), are utilized to support the characterization. Finally, best performance electrolyte mixtures were utilized to build >0.5 Ah pouch cells for testing at low temperatures, discharge rates, and pressure conditions.

Rice powder template for hausmannite Mn3O4 nanoparticles and its application to aqueous zinc ion battery.

In this study, a simple calcination route was adopted to prepare hausmannite Mn3O4 nanoparticles using rice powder as soft bio-template. Prepared Mn3O4 was characterized by Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray microanalysis (EDX), Powder X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Solid state UV-Vis spectroscopic techniques. Mn-O stretching in tetrahedral site was confirmed by FTIR and Raman spectra. % of Mn and O content supported Mn3O4 formation. The crystallinity and grain size was found to be 68.76% and 16.43 nm, respectively; tetragonal crystal system was also cleared by XRD. TEM clarified the planes of crystal formed which supported the XRD results and BET demonstrated mesoporous nature of prepared Mn3O4 having low pore volume. Low optical band gap of 3.24 eV of prepared Mn3O4 nanoparticles indicated semiconductor property and was used as cathode material to fabricate CR-2032 coin cell of Aqueous Rechargeable Zinc Ion Battery (ARZIB). A reversible cyclic voltammogram (CV) showed good zinc ion storage performance. Low cell resistance was confirmed by Electrochemical Impedance Spectroscopy (EIS). The coin cell delivered high specific discharge capacity of 240.75 mAhg-1 at 0.1 Ag-1 current density. The coulombic efficiency was found to be 99.98%. It also delivered excellent capacity retention 94.45% and 64.81% after 300 and 1000 charge-discharge cycles, respectively. This work offers a facile and cost effective approach for preparing cathode material of ARZIBs.

Removal of total ammoniacal nitrogen from reject water through selective electrodialysis reversal and bipolar electrodialysis

The removal of ammonium and ammonia, represented as total ammoniacal nitrogen (TAN), from reject water through electro-dialysis (ED) and bipolar membrane electrodialysis (BPMED) encounters challenges such as organic fouling, NH3 back-diffusion, and high energy consumption. The efficacy of electrodialysis reversal (EDR) combined with bipolar membrane electrodialysis using cation-exchange membranes (BPC) was assessed as a more practical configuration (EDR + BPC). Additionally, a novel configuration involving monovalent selective cation-exchange membranes (MSCEMs) in an EDR + BPC setup (SEDR + BPC) was investigated. Comparisons were made among BPMED, EDR + BPC, and SEDR + BPC under three load ratios (LN) of 0.8, 1, and 1.3 during continuous operation. The innovative SEDR + BPC configuration, with an LN of 0.8, exhibited the lowest energy consumption for transported TAN (ETAN) at 4.4 MJ·kgN−1 removal and achieved the highest TAN removal efficiency of 78 % with an LN of 1.3. In contrast to conventional BPMED, SEDR + BPC allowed for the recovery of potentially back-diffused NH3 into the acid chamber, minimizing transport losses. Furthermore, scaling in the base chamber was reduced due to the contribution of MSCEMs when applying an LN of 0.8. The MSCEMs increased the molar ratio of TAN over (Mg2+ + Ca2+) in the concentrate and decreased it in the diluate. EDR + BPC and SEDR + BPC configurations exhibited stable and lower cell resistance throughout the operation compared to BPMED, attributed to their ability to generate higher concentration gradients. The results clearly demonstrated the feasibility of low-energy TAN removal from real reject water from sludge anaerobic digestion using the SEDR + BPC setup.

High-performance Ni-free sustainable cathode Na0.67Mg0.05Fe0.1Mn0.85O2 for sodium-ion batteries.

Having in mind the remarkable economic and environmental issues involved in the presence of nickel and cobalt metals in electrode compositions, new Na0.67Mg0.05Fe0.1NixMn0.85-xO2 (x=0.0, 0.05, 0.1, 0.15) with a P2 type layered structure, are synthesized to be essayed as positive electrodes in sodium-ion batteries. The sol-gel route here proposed favors the obtention of highly pure and crystalline samples with a homogeneous distribution of the constituting elements. Both galvanostatic and voltammetric tests reveal a superior electrochemical behavior for the Ni-free sample, which delivers 94 mA h g-1 at 5C. This excellent performance is associated with a good kinetic response in terms of low charge and discharge hysteresis, high Na+ diffusivity, and low cell resistance. Ex-situ measurements evidenced the combined contribution of both the reversible electrolyte insertion and the formation of peroxo species. These advantageous properties allow this electrode to reach a remarkable behavior when is cycled either to low temperatures or high rates.

Cross-Linked Anion Exchange Membranes for Non-Aqueous Redox Flow Battery

The development of redox flow batteries (RFBs) has been one of the primary responses to the need to store harvested renewable energy for improving grid reliability and utilization.1–6 In this study, we synthesized and characterized different Bromobutyl Norbornene backbone-based anion-exchange membranes (AEM) with different Tetramethyl hexadiamine crosslinker amounts and explored the performance of AEMs in non-aqueous redox flow batteries under ideal conditions. Performance was compared based on high stability in a non-aqueous solvent, high permeability to the charge-carrying ion, low electric cell resistance, low cross-over of the redox-active molecules, high mechanical property, and low cost. 100 cycles battery data indicates that Bromobutyl Norbornene-based AEM performance is far better than the commercial best membrane Fuma-375. The best membrane will be found which will show no cross-over of redox-active electrolytes after 1000 battery cycle experiments and exhibit low resistance and high structural/chemical stability in MeCN solvent. References (1) Mazumder, Md. M. R.; Burton, A.; Richburg, C. S.; Saha, S.; Cronin, B.; Duin, E.; Farnum, B. H. Controlling One-Electron vs Two-Electron Pathways in the Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate. Inorg. Chem. 2021, 60 (17), 13388–13399. https://doi.org/10.1021/acs.inorgchem.1c01699.(2) Mazumder, M. M. R.; Farnum, B. H. Two One Electron vs One Two-Electron Redox System of Nickel Diethyldithiocarbamate for Redox Flow Battery; ACS, 2021. https://doi.org/10.1021/scimeetings.1c00951.(3) Mazumder, M. M. R. Ni(IV/II) Redox Couple 2e- Reversibility Improvement for Redox Flow Battery. ECS Meet. Abstr. 2021, MA2021-02 (5), 1855–1855. https://doi.org/10.1149/ma2021-0251855mtgabs.(4) Islam, R.; Mazumder, M. M. R.; Farnum, B. H. Solvent Dependent Spectroscopic and Electrochemical Studies of Nickel (II) Diethyldithiocarbamate for Energy Storage. ECS Meet. Abstr. 2021, MA2021-01 (1), 54–54. https://doi.org/10.1149/ma2021-01154mtgabs.(5) Rahaman Mazumder, M. M.; Islam, R.; Khan, M. A. R.; Anis‐Ul‐Haque, K. M.; Rahman, M. M. Efficient AcFc‐[Fe III (Acac) 3 ] Redox Couple for Non‐aqueous Redox Flow Battery at Low Temperature. Chem. – Asian J. 2023, 18 (1). https://doi.org/10.1002/asia.202201025.(6) Mazumder, Md. M. R.; Dalpati, N.; Pokkuluri, P. R.; Farnum, B. H. Zinc-Catalyzed Two-Electron Nickel(IV/II) Redox Couple for Multi-Electron Storage in Redox Flow Batteries. Inorg. Chem. 2022, 61 (48), 19039–19048. https://doi.org/10.1021/acs.inorgchem.2c03124.

Planar Sodium‐Nickel Chloride Batteries with High Areal Capacity for Sustainable Energy Storage

AbstractHigh‐temperature sodium‐nickel chloride (Na‐NiCl2) batteries are a promising solution for stationary energy storage, but the complex tubular geometry of the solid electrolyte represents a challenge for manufacturing. A planar electrolyte and cell design is more compatible with automated mass production. However, the planar cell design also faces a series of challenges, such as the management of molten phases during cycling. As a result, cycling of planar high‐temperature cells until now focused on moderate areal capacities and current densities. In this work, planar cells capable of integrating cost‐efficient nickel/iron electrodes at a substantially enhanced areal capacity of 150 mAh cm−2 is presented. Due to a low cell resistance during operation at 300 °C, these cells deliver a specific discharge energy of 300 Wh kg−1 at high discharge current densities of 80 mA cm−2 (C/2, 10%–100% state‐of‐charge). This results represent the first demonstration of planar Na‐NiCl2 cells at a commercially relevant combination of areal capacity, cycling rate, and energy efficiency. It is further identified the secondary molten NaAlCl4 electrolyte to contribute to the cell capacity during cycling. Mitigating electrochemical decomposition of NaAlCl4 will play an important role in further enhancing both cycling rates and cycle life of high temperature Na‐NiCl2 batteries.

Optimized synthesis of Na2/3Ni1/3Mn2/3O2 as cathode for sodium-ion batteries by rapid microwave calcination

Microwave calcination is proposed as an alternative route to conventional heating to prepare layered P2–Na2/3Ni1/3Mn2/3O2 as a positive electrode for sodium-ion batteries. The sample obtained by the fastest conditions, with a heating ramp of 20 °C min−1 for only 2 h, showed well-crystallized rounded particles. Cyclic voltammetry and impedance spectroscopy evidenced a low internal cell resistance, and high diffusion coefficients, which justify its capability to sustain the highest capacity at 1 C and retain the discharge capacity for at least two hundred cycles.

Cross-Linked Phenyl-Acrylate-Based Anion Exchange Membranes Synthesis, Characterization and Performance in Non-Aqueous Redox Flow Battery

The development of redox flow batteries (RFBs) has been one of the primary responses to the need to store harvested renewable energy for improving grid reliability and utilization.1–4 In this study, we synthesized and characterized seven types of Phenyl acrylate (PA) backbone-based anion-exchange membranes (AEM) and explored the performance of AEMs in non-aqueous redox flow batteries under ideal conditions. IR data (Figure 1 ) confirms the incorporation of ion carriers in the PA backbone. Methacroylcholine chloride (MACC) was used as an anion carrier, N, N-Methylenebis acrylamide (MBAA) was used as a cross-linker, and 1-Hydroxycyclohexyl phenyl ketone (HCPK) was used as a photoinitiator. Performance was compared based on high stability in a non-aqueous solvent, high permeability to the charge-carrying ion, low electric cell resistance, low cross-over of the redox-active molecules, high mechanical property, and low cost. The best membraned will be found which will show no cross-over of redox-active electrolytes after 1000 battery cycle experiments and exhibit low resistance and high structural/chemical stability in MeCN solvent. References (1) Mazumder, Md. M. R.; Burton, A.; Richburg, C. S.; Saha, S.; Cronin, B.; Duin, E.; Farnum, B. H. Controlling One-Electron vs Two-Electron Pathways in the Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate. Inorg. Chem. 2021, 60 (17), 13388–13399. https://doi.org/10.1021/acs.inorgchem.1c01699.(2) Mazumder, M. M. R.; Farnum, B. H. Two One Electron vs One Two-Electron Redox System of Nickel Diethyldithiocarbamate for Redox Flow Battery; ACS, 2021. https://doi.org/10.1021/scimeetings.1c00951.(3) Mazumder, M. M. R. Ni(IV/II) Redox Couple 2e- Reversibility Improvement for Redox Flow Battery. ECS Meet. Abstr. 2021, MA2021-02 (5), 1855–1855. https://doi.org/10.1149/ma2021-0251855mtgabs.(4) Islam, R.; Mazumder, M. M. R.; Farnum, B. H. Solvent Dependent Spectroscopic and Electrochemical Studies of Nickel (II) Diethyldithiocarbamate for Energy Storage. ECS Meet. Abstr. 2021, MA2021-01 (1), 54–54. https://doi.org/10.1149/ma2021-01154mtgabs. Figure 1

Electrochemically-mediated amine regeneration of CO2 capture: From electrochemical mechanism to bench-scale visualization study

Electrochemically-mediated amine regeneration (EMAR) is a new CO2 capture technology with the potential to exploit the excellent removal efficiencies of thermal amine scrubbers while reducing parasitic energy losses and capital costs. To achieve higher efficiency and explore the industrial application of the promising EMAR system, a home-designed bench-scale modular flowing-through electrolysis cells (MFTECs) is proposed. The MFTECs with MEA solvent is carefully analyzed from electrochemical mechanism to bench-scale demonstration. Firstly, a series of electrochemical experiments were conducted in an H-cell to study the unknown electrochemical behaviors under various complex concentrations and temperatures, which provided a guidance to enhance the electrochemical performance. Subsequently, a visualization study of the CO2 desorption process in MFTECs was conducted at different operating conditions (current, complex concentration, electrode position, and reaction time) to investigate the desorption performance of the proposed MFTECs system. This framework allowed for direct observation and comprehension of the CO2 desorption process, as well as the movement and interaction of CO2 bubbles in MFTECs. Finally, results indicated that the proposed MFTECs enables higher electrode active surface area and lower cell resistance. This will contribute to enhancing the regeneration performance and promoting industrial application of CO2 desorption based on EMAR.

Paired and Tandem Electrochemical Conversion of 5‐(Hydroxymethyl)furfural Using Membrane‐Electrode Assembly‐Based Electrolytic Systems

AbstractPairing the electrocatalytic hydrogenation (ECH) reaction with different anodic reactions holds great promise for producing value‐added chemicals driven by renewable energy sources. Replacing the sluggish water oxidation with a bio‐based upgrading reaction can reduce the overall energy cost and allows for the simultaneous generation of high‐value products at both electrodes. Herein, we developed a membrane‐electrode assembly (MEA)‐based electrolysis system for the conversion of 5‐(hydroxymethyl)furfural (HMF) to bis(hydroxymethyl)furan (BHMF) and 2,5‐furandicarboxylic acid (FDCA). With (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO)‐mediated electrochemical oxidation (ECO) of HMF at the anode, the unique zero‐gap configuration enabled a minimal cell voltage of 1.5 V at 10 mA, which was stable during a 24‐hour period of continuous electrolysis, resulting in a combined faradaic efficiency (FE) as high as 139 % to BHMF and FDCA. High FE was also obtained in a pH‐asymmetric mediator‐free configuration, in which the ECO was carried out in 0.1 M KOH with an electrodeposited NiFe oxide catalyst and a bipolar membrane. Taking advantage of the low cell resistance of the MEA‐based system, we also explored ECH of HMF at high current density (280 mA cm−2), in which a FE of 24 % towards BHMF was achieved. The co‐generated H2 was supplied into a batch reactor in tandem for the catalytic hydrogenation of furfural or benzaldehyde under ambient conditions, resulting in an additional 7.3 % of indirect FE in a single‐pass operation. The co‐electrolysis of bio‐derived molecules and the tandem electrocatalytic‐catalytic process provide sustainable avenues towards distributed, flexible, and energy‐efficient routes for the synthesis of valuable chemicals.

A dual vanadium substitution strategy for improving NASICON-type cathode materials for Na-ion batteries

Al substitution in Na3VAlxCr1−x(PO4)3 (0 ≤ x ≤ 1) induced a noticeable improvement of capacity at the highest rate, as evidenced by their high diffusion coefficients and low cell resistance.

High Rate Performance of Zinc-Nickel Secondary Battery Using Robust Zinc Electrode

A zinc rechargeable battery is one of the most promising candidates of next-generation energy storage devices with some merits such as a high energy density and a low-cost material, although no zinc has been used as the negative electrode for secondary uses. This is because some dendrites are generated on the zinc electrode during charge, which causes an internal short circuit. Our recent work [1] has developed a new zinc electrode that can operate at 1 C in alkaline aqueous solutions for 5,500 cycles or more, during which the charge and discharge voltages were stable and the initial capacity was kept over 90 %. In this work, we used this robust zinc electrode in zinc-nickel secondary batteries and examined high rate performance of the cell to know the cell resistance.The new zinc electrode used a copper plate as the current collector, on which zinc had been deposited by electroplating, and was designed so that the electrolyte was separated in some parallel zones. A nickel electrode and a 6 mol/L KOH solution containing saturated ZnO were also used to fabricate a zinc-nickel cell. The cell was operated at room temperature and the cell voltages during charge and discharge were measured. The operation was carried out with the following rate pattern: 1 C (1 min.) → 2 C (2 sec.) → 1 C (1 min.) → 4 C (2 sec.) → 1 C (1 min.) → 6 C (2 sec.) → 1 C (1 min.) → 8 C (2 sec.) → 1 C (1 min.) → 10 C (2 sec.). This pattern was repeated three times during each of discharge and charge. The capacity of the zinc electrode was calculated from the weight of deposited zinc and the C rate was further determined with the electrode’s capacity. The SOC range for charge and discharge was changed to know the effects on the rate performance and the cell resistance.The discharge voltage was stable even at 10 C and changed immediately from 1 C to 10 C or vice versa. The plots of the discharge voltage and the current density showed a linear relationship, and the cell resistance ranged from 1.0 ohm cm2 to 1.2 ohm cm2 in the SOC region between 40 % and 100 %. These results suggest that it is possible for the cell to discharge at 10 C in maximum with such a low cell resistance and respond to the rate change. The charge voltage at 2 C or 4 C was almost constant in 2 sec., while that at 6C, 8C, or 10 C changed 20 mV in maximum during the short period. The charge voltage at 1 C after 10 C charge was almost the same as that before it, indicating a quick charge response to the rate change even during charge. The charge voltage was also linear to the current density, and the cell resistance was 1.2 ohm cm2 to 1.4 ohm cm2 from the Ⅰ-Ⅴ relationship which excluded the charge voltage data suggesting hydrogen evolution. From the above results, we demonstrated that the new zinc electrode worked well in the zinc-nickel secondary cell at high rate up to 10 C and responded well to a quick change in C rate without dendrite issues. This work was financially supported by DOWA TECHNO FUND of DOWA Holdings, Co., Ltd.Reference[1] T. Okumura, K. Kawaguchi, M. Morimitsu, TMS 2020, San Diego (2020).

Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Summary Production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250°C is demonstrated. The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer. Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electrooxidation. Cells were operated at 250°C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode. A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 m o l H 2 / g c a t h .

Optimizing high voltage Na3V2(PO4)2F3 cathode for achieving high rate sodium-ion batteries with long cycle life

Sodium-ion batteries have gained an intense attention as a promising alternate for Li-ion batteries due to their low cost, and abundant availability. To meet high energy density requirements, developing a high voltage cathode with ultra-long cycle life is of great importance. Na3V2(PO4)2F3 (NVPF) features a high working voltage, fast sodium-ion diffusion channels, and small volume change during the cycling process. However, the practical performance of NVPF cathode is currently hindered by poor Na+ ion diffusion at high voltage, low cycle life, and limited rate behavior. Herein, we evaluate the effect of synthesis conditions in sol–gel technique, binders (PVDF, PAI and CMC), and electrolytes (ether, and ester based solvents) to overcome the diffusion limitation in high voltage NVPF cathode. Benefiting from the synergistic effect of CMC binder, and DEGME electrolyte, and reduced graphene oxide composite, NVPF effectively overcome the potential barrier during Na+ ion insertion/extraction at high voltage. NVPF with CMC binder and DEGDME electrolyte displayed a high Na+ ion diffusion kinetics, low cell resistance, and delivered an excellent electrochemical performance. NVPF delivered a high coulombic efficiency (92%), long cycle life (10,000 cycles), and an excellent rate performance (50 C), outperforming the conventional PVDF binder, and carbonate based electrolytes. Furthermore, the full-cell constructed by NVPF cathode, and Na3V2(PO4)3 anode delivered an capacity retention. The current study provides new insights for overcoming the kinetic barrier during sodium ion storage in high voltage cathode that could direct the research development towards high energy sodium-ion batteries.

Centrifugally spun porous carbon microfibers as interlayer for Li–S batteries

Lithium–sulfur (Li–S) batteries have attracted great interest owing to their high energy density. However, shuttling of polysulfides deteriorates the electrochemical performance of Li–S batteries and prevents their practical applications. Placing a conductive and porous interlayer structure between the cathode and the separator limits the shuttling effect and improves the cycling performance. Here, porous carbon microfibers are fabricated via a fast, safe and cost-effective centrifugal spinning approach and the resultant centrifugally spun porous carbon microfibers (CS-PCMFs) are evaluated for use as an interlayer in Li–S batteries. The highly porous fibrous structure is observed from SEM and TEM images, and a high initial discharge capacity of 1485 mAh g−1 is achieved. A high reversible capacity of 615 mAh g−1 is reached after 200 cycles at 0.2 C. In addition, the cell with CS-PCMF interlayer has low cell resistance of 25 O, whereas that of Li–S cell without interlayer is 55 O. Owing to the low cell resistance, the cell with CS-PCMF interlayer delivers the reversible capacity of around 600 mAh g−1 at 1 C, while the cell without interlayer exhibits a lower capacity of 250 mAh g−1. Therefore, this work provides a new approach for designing highly porous carbon microfiber interlayer for Li–S batteries with exceptional electrochemical performance.

(Invited) ALD and MLD of Functional Thin-Film Coatings for Enhanced Performance in Li-Ion and Li-Metal Solid-State Batteries

The key figures of merit for batteries are Energy density, charging time (C-rate) and cycling Life time. In this invited talk we will focus on the application of continuous closed thin films as artificial interfaces in large capacity batteries or for the fabrication of functional battery components in micro-batteries. We will deal mostly with the perspective of device performance where the ALD and MLD processes merely provide the films and enable their ultrathin, continuous and conformal nature. Nanoscale film thickness allows for low interface and cell resistance even when the materials themselves are poor conductors. For example. LiPON (N-doped Li3PO4) is a solid electrolyte interesting because it is stable against metallic lithium but, because of its poor ionic conductivity (<10-6 S/cm) only practically useful for thicknesses under few hundred nanometers. Even further, materials which are not solid electrolytes by their own merit (e.g. TiO2) still have ion-transparent properties up to several tens of nanometer and can be used as ion transparent artificial interfaces in contrast to alumina which is an insulator for Li-ions. For coating of individual particles, ideally coatings which have both electronic and ionic conducting (or transparent) properties. Doping is one approach to enhance either conductivity. When scaling down of the film thickness also finite size effects have to be considered, for example, the thickness of the electrical double layer, diffusion layer thickness and the electric field over the dielectric. ALD and MLD can be used also to fabricate functional nanomaterials; i.e. by harvesting nanoscale effects. For example, nanocomposite solid electrolyte films of a few tens of nanometers were fabricated by a combination of MLD of inorganic-organic hybrid alucone thin-films, etching the organic fraction in water and functionalization by ALD of Li2CO3 and Li3PO4. For the first time, enhanced ion conductivity is shown by harvesting the enhanced ion conductivity at oxide/ion conductor interfaces. Finally, volume changes during charge and discharge are limiting the cycle life-time of batteries, especially for rigid solid-state batteries. Also ALD thin-films suffer from the mechanical strain and the benefits of the “closed” protective film are lost. Therefore, MLD of hybrid organic/inorganic coatings is explored to enable more elastic coatings for improved cycle life time.

Reactive template synthesis of Li1.2Mn0.54Ni0.13Co0.13O2 nanorod cathode for Li-ion batteries: Influence of temperature over structural and electrochemical properties

Common preparation methods of manganese-based Li-rich layered oxides include co-precipitation, combustion, spray pyrolysis, and molten salt synthesis. Herein, we present a facile new reactive-templating route to prepare manganese-based lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 using β−MnO2 nanorod, which plays a dual role as reactive template as well as Mn-source. Rietveld refinement and electron diffraction patterns confirm the formation of phase pure, highly crystalline Li1.2Mn0.54Ni0.13Co0.13O2 with two integrated layered components of 0.5(Li2MnO3).0.5(LiMn1/3Ni1/3Co1/3O2). Electron microscopy studies reveal the formation of anisotropic rod-like crystals of 0.8–1.0 μm in length and ∼200 nm in thickness. The Li1.2Mn0.54Ni0.13Co0.13O2 nanorod as cathode for Li-ion battery, delivers an impressive reversible capacity of 223 mAh.g−1 at 0.1C rate after 150 cycles and 161 mAh.g−1 at 1 C rate after 300 cycles. Rapid structural transition from layered to spinel-like phase at high temperature (55 °C) leads to gradual decay in discharge capacity upon cycling, whereas low Li-ion diffusivity, cell resistance, and high viscosity hampers the performance at low temperature (5 °C). Impedance spectroscopy along with (dis)charge differential plots corroborate that activation of Li2MnO3 and Li-ion de(intercalation) into the MnO2 phase is very facile at high temperature (55 °C), which leads to high specific capacity, high coulombic efficiency, and high-power capability.

Improving Cell Resistance and Cycle Life with Solvate/Thiophosphate Hybrid Electrolytes in Lithium Batteries

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature are comparable to those of the commercially-utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. In this study, we add lithium bis(triflouromethane sulfonyl)imide (LiTFSI) and a highly fluorinated ether (HFE) solvate electrolyte to the surface of Li7P3S11 (LPS) and Li10GeP2S12 (LGPS) pellets and evaluate their overall cell resistance in Li-Li symmetric cells relative to their bare Li/SE/Li counterparts. Time-resolved electrochemical impedance spectroscopy (EIS) shows an order of magnitude lower cell resistance for the LGPS-solvate than for the bare LGPS. Cyclic voltammetry (CV) of the bare and hybrid SE cells shows an order of magnitude higher current density for the LGPS-solvate cell over the bare LGPS. Interestingly, hybrid electrolytes made by combining HFE-modified solvates and SE exhibit all the benefits of the interlayer modified SEs, without the necessity of pellet manufacture. This study suggests that solvates can be used to improve the cell resistance and current density of solid electrolytes by altering the grain boundary structures and the interphase between electrode and electrolyte.