Increase In Discharge Capacity Research Articles

Improved Discharge Capacity of Zinc Particles by Applying Bismuth-Doped Silica Coating for Zinc-Based Batteries

Corrosion and discharge behavior of battery-grade zinc particles coated with a silica layer doped with bismuth was investigated and compared with untreated zinc powder. Electrochemical investigations were carried out in half-cell configuration. The electrolyte was 6 M KOH in excess. Coated zinc particles provided a discharge capacity of 737 mAh g−1 (89.9% DoD) versus 633 mAh g−1 (77.2% DoD) of untreated zinc particles after a dwell time of 1 h in KOH. The silica coating reduced the direct contact of the zinc surface with the electrolyte and thus minimized the hydrogen evolution reaction, which led to an increased discharge capacity. Additionally, bismuth doping enhanced conductivity within the silica coating and increased zinc utilization. Those coated zinc particles inhibited corrosion, i.e., corrosion efficiency reached 87.9% compared to uncoated zinc. Additionally, the coating achieved a capacity retention of 90.9% (670 mAh g−1) after 48 h dwell time in 6 M KOH. The coatings were prepared by sol-gel technology and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface determination.

Improving cyclic stability of LiCoO2 charged to 4.5 V by using succinic anhydride as co-solvent

Enhancing the cutoff charge voltage of LiCoO2 can obviously increase energy density but deteriorate its cyclic stability. To address this issue, succinic anhydride (SA) is chosen as an efficient co-solvent to improve the cyclic stability of LiCoO2 electrode charged to 4.5 V (vs. Li/Li+). LiCoO2/Li half-cell with 10 wt% SA achieves 39% increased discharge capacity after 200 cycles at 0.5 C (1 C = 185 mA h g−1), compared to the one in base electrolyte between 3 and 4.5 V. Additionally, the mechanism of how SA improves the cyclic stability of LiCoO2 under high charge voltage is elucidated by electrochemical impedance spectroscopy, linear sweep voltammetry, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. All the results consistently show that SA yields a more compact and stable passivation layer on the surface of LiCoO2 than that without SA, leading to the much higher cyclic stability for LiCoO2 electrode at high cutoff voltage.

Poly(3,4-ethylenedioxythiophene) coated lead negative plates for hybrid energy storage systems

Herein, we report Poly(3,4-ethylenedioxythiophene) coating on to lead negative plates as a hybrid electrode material for lead-acid batteries and supercapacitors. Poly(3,4-ethylenedioxythiophene) coating on to negative plate addresses the issue of sulfation at negative plate in a lead-acid cell. Poly(3,4-ethylenedioxythiophene) coating on to the conventional negative plates is wind up by electropolymerization technique. 2 V/2.1 A h lead-acid cells assemble with Poly(3,4-ethylenedioxythiophene) coating negative electrodes show ∼25% increase in initial discharge capacity, excellent cycle performance at 5 h rate, lower impedance, reduce hydrogen evolution and boost charge acceptance in relation to the conventional lead-acid cell. The Poly(3,4-ethylenedioxythiophene) coating lead-acid cells show 20% improvement in C/5 rate and 107% in high rate partial state of charge cycling. The specific capacitance of Poly(3,4-ethylenedioxythiophene) in 4.5 M H2SO4 medium is about 105 F g−1 with an excellent cycle life of over 20, 000 cycles at 2 A g−1. The superior performance is due to fast kinetics of Poly(3,4-ethylenedioxythiophene) in sulfuric acid electrolyte.

New Insight into Ethylenediaminetetraacetic Acid Tetrasodium Salt as a Sacrificing Sodium Ion Source for Sodium-Deficient Cathode Materials for Full Cells.

Sacrificing sodium supply sources is needed for sodium-deficient cathode materials to achieve commercialization of sodium-ion full cells using sodium-ion intercalation anode materials. Herein, the potential of ethylenediaminetetraacetic acid tetrasodium salt (EDTA-4Na) as a sacrificing sodium supply source was investigated by intimately blending it with sodium-deficient P2-type Na0.67[Al0.05Mn0.95]O2. The EDTA-4Na/Na0.67[Al0.05Mn0.95]O2 composite electrode unexpectedly exhibited an improved charge capacity of 177 mA h (g-oxide)-1 compared with the low charge capacity of 83 mA h (g-oxide)-1 for bare Na0.67[Al0.05Mn0.95]O2. The reversible capacity of an EDTA-4Na/Na0.67[Al0.05Mn0.95]O2//hard carbon full-cell system increased to 152 mA h (g-oxide)-1 at the first discharge with a Coulombic efficiency of 89%, whereas the Na0.67[Al0.05Mn0.95]O2 without EDTA-4Na delivered a discharge capacity 51 mA h g-1 because of the small charge capacity. The EDTA-4Na sacrificed itself to generate Na+ ions via oxidative decomposition by releasing four sodium ions and producing C3N as a decomposition resultant on charge. It is thought that the slight increase in discharge capacity is associated with the electroconducting nature of the C3N deposits formed on the surface of the Na0.67[Al0.05Mn0.95]O2 electrode. We elucidated the reaction mechanism and sacrificial activity of EDTA-4Na, and our findings suggest that the addition of EDTA-4Na is beneficial as an additional source of Na+ ions that contribute to the charge capacity.

Rapid Electrochemical Assessment of the Leady Oxide Recovered from Spent Lead Pastes: A Case Study on the Effect of Iron and Antimony Doping

A rapid electrochemical assessment of the performance of novel leady oxide is demonstrated to provide an alternative route for the time-consuming battery tests. The leady oxide is recovered from spent lead pastes with different level of Fe and Sb doping. The rapid electrochemical assessment for leady oxide acting as positive active materials (PAMs) of a lead-acid battery (LAB) is conducted via cyclic voltammetry (CV) using a three-electrode system. The working electrode is the novel leady oxide which was coated on the current collector of glassy carbon. The current density and discharge capacity increase rapidly at first, then decrease and finally tend to be stable gradually. The rising and falling parts of the CV curves indicate the forming and discharging processes, respectively. The imax cycle and the discharge capacity of leady oxide in CV tests are proved to be ideal indicators of the initial capacity and cycle performance of a fabricated battery. Based on this rapid assessment method, the effects of iron and antimony on electrochemical performance of leady oxide have been clarified. This electrochemical evaluation procedure only takes less than 2 days, and the electrochemical performance of leady oxide represents the procedure of formation and cycling as a lead-acid battery.

Sulfur/CuxS hybrid material for Li/S primary battery with improved discharge capacity

Abstract Sulfur is potential for primary lithium battery with high power and energy. However, the discharge capacity is limited due to the low electrochemical activity of sulfur. In this work, CuxS is incorporated into sulfur cathode synergistically to improve discharge specific capacity for primary lithium battery. For the sulfur/CuxS hybrid cathodes, discharge capacity is higher than the sulfur cathode. With the CuxS in hybrid cathodes varying from 40% to 60 wt %, the discharge capacity increases and then decreases when CuxS reaches 80 wt %. An enhanced discharge capacity of 1618.5 mAh g−1(S) at the current rate of 0.1C, energy density of 1107 Wh kg−1(CuS+S) and power density of 2827 W kg−1(CuS+S) are obtained when CuxS reaches 60 wt %. The good discharge performance is derived from trapping of polysusfides through chemical redox of sulfiphilic CuxS and capacity contribution of semi–conductive CuxS. And, the self–discharge is limited of the sulfur/CuxS hybrid cathodes. This new cooperation provides a promising approach to significantly enhance the discharge performance of primary lithium batteries.

Spray-Printed and Self-Assembled Honeycomb Electrodes of Silicon-Decorated Carbon Nanofibers for Li-Ion Batteries.

Directional, micron-scale honeycomb pores in Li-ion battery electrodes were fabricated using a layer-by-layer, self-assembly approach based on spray-printing of carbon nanofibers. By controlling the drying behavior of each printed electrode layer through optimization of (i) the volume ratio of fugitive bisolvent carriers in the suspension and (ii) the substrate temperature during printing, self-assembled, honeycomb pore channels through the electrode were created spontaneously and reliably on current collector areas larger than 20 cm × 15 cm. The honeycomb pore structure promoted efficient Li-ion dynamics at high charge/discharge current densities. Incorporating an optimum fraction (2.5 wt %) of high-energy-density Si particulate into the honeycomb electrodes provided a 4-fold increase in deliverable discharge capacity at 8000 mA/g. The spray-printed, honeycomb pore electrodes were then investigated as negative electrodes coupled with similar spray-printed LiFePO4 positive electrodes in a full Li-ion cell configuration, providing an approximately 50% improvement in rate capacity retention over half-cell configurations of identical electrodes at 4000 mA/g.

1D Nb-doped LiNi1/3Co1/3Mn1/3O2 nanostructures as excellent cathodes for Li-ion battery

The effect of niobium (Nb) doping in one-dimensional (1D) nanostructured LiNi1/3Co1/3Mn1/3O2 (NCM) cathode has been investigated for this study. Nb-doped NCM nanofibres have been prepared through an electrospinning method followed by controllable sintering process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed that Nb-doping can effectively reduce cation mixing, thus improve the structural stability. In addition, due to the valence compensation balance, Mn4+ ions are partially reduced to Mn3+ ions, which can further improve the conductivity and stable cycling performance. Therefore, increased discharge capacities, high first cycle efficiencies and superior cycling and rate behaviors are observed between normal voltage limits for the Nb-doped NCM compositions in electrochemical cells. Specifically, Nb-doped NCM nanofibres achieve a high discharge capacity of 200.4 mAh/g at 0.1 C with a high Coulombic efficiency of 92.3%. Moreover, a high discharge capacity of 118.7 mAh/g even at 5 C with 83.3% capacity retention after 200 cycles is also achieved. Also, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results demonstrate that Nb-doping can mitigate the electrochemical polarization of NCM and improve the lithium ion diffusion coefficient, leading to the improvement of electrochemical performances. It is highly expected that our findings can provide a general approach to improve the electrochemical properties of cathode materials for lithium-ion batteries.

Electrochemical characterization of nanocrystalline hydrogen storage La1.5Mg0.5Ni6.5Co0.5 alloy covered with amorphous nickel

Nanocrystalline hydrogen storage La1.5Mg0.5Ni6.5Co0.5 alloy was obtained by mechanical alloying and heat treatment (850 °C/0.5 h). The A2B7 phase is dominant in so synthesized material. Concentration of AB5 phase is close to 3 at. % and is 2.6 times lower than that in Co-free La1.5Mg0.5Ni7 alloy. The La1.5Mg0.5Ni6.5Co0.5 powder fraction of 20–50 μm was encapsulated with thin (0.48 μm thick), amorphous nickel by magnetron sputtering. The electrochemical charge/discharge multicycling of powder composite electrodes was carried out in view of material potential usefulness as electrode material for Ni/MHx batteries. Partial substitution of Ni by Co in La1.5Mg0.5Ni7 nanocrystalline alloy is prone to increase of electrode discharge capacity (up to 14%) and enhances its activation (strong decrease of Nmax cycle and simultaneous increase of QNmax). On the other hand, Co addition worsens corrosion degradation behavior, but the corrosion resistance can be improved (≈30%) by the application of amorphous nickel coating. Finally, Co modified La1.5Mg0.5Ni7 nanocrystalline alloy reveals 15% greater exchange current density of H2O/H2 system and improved hydrogen diffusivity compared to the reference, nanocrystalline Co-free La1.5Mg0.5Ni7 hydrogen storage material.

Poly(imide-co-siloxane) as a Thermo-Stable Binder for a Thin Layer Cathode of Thermal Batteries

The polymer binder, poly(imide-co-siloxane) (PIS), was synthesized and applied to form a thin cathode layer of composites for a thermal battery that has an unusually high operating temperature of 450 °C. The PIS was prepared through cross-linking of the polyimide with polysiloxane. The morphology of FeS2/PIS composites showed that FeS2 particles was coated with the PIS cross-linked gel. The FeS2/PIS composites enabled to fabricate mechanically stable thin cathode layer that was 10–20% of the thickness of a conventional pellet-type cathode. The FeS2/PIS composites were stable up to 400 °C and maintained their morphology at this temperature. PIS coating layers decomposed at 450 °C, and a new residue was generated, which was observed by transmission electron microscopy, and the compositional change was analyzed. The FeS2/PIS composites showed enhanced thermal stability over that of FeS2 in thermogravimetric analysis. The thermal battery with the PIS polymer binder showed a 20% discharge capacity increase when compared to a conventional pellet-type cathode.

In-situ nitrogen-doped hierarchical porous hollow carbon spheres anchored with iridium nanoparticles as efficient cathode catalysts for reversible lithium-oxygen batteries

One of the biggest challenges on the way to the commercialization of lithium-oxygen (Li-O2) batteries (LOBs) is the exploration of an air electrode with high electronic conductivity, steadily porous architecture, and high-efficiency bifunctional catalytic activity. In this study, nitrogen-doped and iridium decorated carbon spheres with hollow and hierarchical porous structure were successfully fabricated and used as excellent bifunctional electrocatalysts in alkaline aqueous environment as well as in non-aqueous LOBs. This material structure with large pore volume and high specific surface area provides sufficient room and numerous active sites for the deposition of Li2O2 product. Moreover, the in-situ nitrogen doping further enhances the electron conductivity as well as the electrocatalytic activity toward oxygen, yielding a gratifying discharge platform potential of 2.77 V, and a high discharge capacity (6849 mAh g−1). After anchoring with Ir nanoparticles, the resulting composite material presented significantly reduced charge overpotential (0.83 V) and improved reversibility. Meanwhile, owing to the synergistic effect among the porous carbon, nitrogen heteroatom, and Ir nanocrystals, the increased discharge capacity of 8239 mAh g−1 and high discharge plateau of 2.80 V were also achieved. Besides, the excellent stability of the recharged air-cathode architecture was confirmed via ex-situ scanning electron microscopy.

In situ TiO2 decorated carbon paper as negative electrode for vanadium redox battery

Developing high-performance electrode is crucial to energy storage performance of vanadium redox battery. Herein, TiO2 decorated carbon paper was developed by hydrothermal route with various treatment time, and employed as negative electrode for vanadium redox battery. TiO2 can be in situ covered on carbon paper by hydrothermal route. Wetting performance of carbon paper is markedly enhanced by introduction of TiO2. Compared with raw carbon paper, TiO2 decorated carbon paper demonstrates excellent electrochemical performance towards V3+/V2+ couple. The sample treated for 6 h (CP-H06) exhibits the best electrochemical properties. The enhanced performance comes from the accelerated transfer of vanadium ions and electrons. The single cell testing indicates that the cell performances are improved significantly by using CP-H06 as negative electrode in terms of increased discharge capacity and energy efficiency. Discharge capacity and energy efficiency increase by 17.8% and 6.4% by using CP-H06 at 100 mA cm−2, respectively. Our study reveals that TiO2 decorated carbon paper with outstanding electrochemical performance exhibits a promising prospect in the energy storage system of vanadium redox battery.

Enhancing the performance of all-vanadium redox flow batteries by decorating carbon felt electrodes with SnO2 nanoparticles

An all-vanadium redox flow battery (VRFB) is an attractive candidate as an electrochemical energy storage system that uses conversion technology for applications that range from those requiring only a few kilowatts to those that must perform on a megawatt scale. Issues to be resolved, however, include problems with increasing the rates of charge/discharge (due to an increase in overpotentials) and cycling stability (due to the irreversibility of redox reactions at the electrodes as well as crossover of the vanadium species) that have prevented a broader market penetration of VRFB systems. One of the strategies to overcome these problems may be the introduction of electrocatalysts to the electrode surface to improve the reaction kinetics of the positive and negative redox couples, thus enabling the achievement of higher levels of power density. Therefore, carbon felt electrodes decorated with SnO2 nanoparticles were evaluated in this study. The performance of VRFBs at a high current density of 150 mA cm−2 with SnO2-deposited carbon felts returned an energy efficiency of 77.3%, with a corresponding increase in discharge capacity of 23.7% over a pristine electrode. Cycling stability of the system was also improved almost 2.7-fold compared with that of a pristine electrode at 50 mA cm−2. The electrocatalytic activity of SnO2 nanoparticles facilitates a reduction in the overpotentials, which enables charge/discharge reactions at faster rates, which was confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. Furthermore, confirmation of the formation of clusters of SnO2 nanocrystals as well as their chemical and physical stability after cycling (as probed by various characterization techniques including synchrotron-based X-ray absorption) supports their feasibility as a stable, efficient and cost-effective electrocatalyst for use in VRFB systems.

Dual Roles of Li3 N as an Electrode Additive for Li-Excess Layered Cathode Materials: A Li-Ion Sacrificial Salt and Electrode-Stabilizing Agent.

Li2 CO3 -passivated Li3 N with high stability is prepared by aging Li3 N powder in dry air, and is then used as an electrode additive for a Li(Li0.18 Ni0.15 Co0.15 Mn0.52 )O2 (LLMO) cathode material. The material shows a large irreversible capacity of 800 mA h g-1 during the first charge, with the formation of a Li2 N intermediate product. Acting as a Li+ sacrificial salt for a LLMO(+)/graphite(-) Li-ion battery, 2 wt % Li3 N results in a 10 % increase in discharge capacity. The Li2 N intermediate product reacts with the electrolyte, forming a uniform and regular surface film on the cathode. Moreover, chemical bonding between LLMO and N improves the electrode stability, resulting in excellent electrochemical performance.

Optimizing the Structural Evolution of Li-Rich Oxide Cathode Materials via Microwave-Assisted Pre-Activation

Preactivation can play a promising role in suppressing oxygen loss during the first charging process in Li-rich oxide cathode materials, relieving a series of problems such as large initial irreversible capacity loss, structure transformation due to ion rearrangement, and oxidation/decomposition of the electrolyte. However, the strategies previous adopted are mainly chemical delithiation, which has violent effect on the crystal structure and deteriorates the cycle performance. Here, we report a facile and effective microwave-assisted treatment method to preactivate Li-rich layered oxides without structural distortion. The microwave-treated sample shows a high discharge capacity of about 281 mAh g–1 with a Coulombic efficiency of 87% at 0.1 C and exhibits unnormal continuous increase of discharge capacity from 203 mAh g–1 to 218 mAh g–1 during 110 cycles at 1 C as well as presents distinctly improved cycling stability. EIS, GITT and XRD studies reveal that the kinetics of electrochemical reaction on electr...

The effect of pore structure and surface properties of carbon nanotube films on the performance of a lithium sulfur battery

We fabricated a Li-S battery with post-treated carbon nanotube (CNT) films which offered better support for sulfur, and investigated the effect of the surface properties and pore structure of the post-treated CNT films on Li-S battery performance. Post-treatments, i.e., acid treatment, unzip process and cetyltrimethylammonium bromide (CTAB) treatment, effectively modified the surface properties and pore structure of the CNT film. The modified pore structure impacted the ability of the CNT films to accommodate the catholyte, resulting in an increase in initial discharge capacity.

Ethanol as an electrolyte additive for alkaline zinc-air flow batteries

Zinc-air flow batteries exhibit high energy density and offer several appealing advantages. However, their low efficiency of zinc utilization resulted from passivation and corrosion of the zinc anodes has limited their broad application. In this work, ethanol, which is considered as an environmentally friendly solvent, is examined as an electrolyte additive to potassium hydroxide (KOH) aqueous electrolyte to improve electrochemical performance of the batteries. Besides, the effects of adding different percentages of ethanol (0–50% v/v) to 8 M KOH aqueous electrolyte were investigated and discussed. Cyclic voltammograms revealed that the presence of 5–10% v/v ethanol is attributed to the enhancement of zinc dissolution and the hindrance of zinc anode passivation. Also, potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that adding 5–10% v/v ethanol could effectively suppress the formation of passivating layers on the active surface of the zinc anodes. Though the addition of ethanol increased solution resistance and hence slightly decreased the discharge potential of the batteries, a significant enhancement of discharge capacity and energy density could be sought. Also, galvanostatic discharge results indicated that the battery using 10% v/v ethanol electrolyte exhibited the highest electrochemical performance with 30% increase in discharge capacity and 16% increase in specific energy over that of KOH electrolyte without ethanol.

Electrochemical and kinetic performance of amorphous/nanostructured TiNi-based intermetallic compound with Nb substitution synthesized by mechanical alloying

Abstract

Femtosecond laser structuring of graphite anodes for improved lithium-ion batteries: Ablation characteristics and process design

Lithium-ion batteries are widely used as energy storage devices due to their high energy density and versatile applicability. Key components of lithium-ion batteries are electrically isolated electrodes and a liquid electrolyte solution which enables ion transport between the electrodes. Laser structuring of electrodes is a promising approach to enhance the high-current capability of lithium-ion batteries by reducing cell internal resistances, as a larger contact area of the active material with the electrolyte solution is created. In the work described here, lithium-ion battery anodes were structured by locally ablating small fractions of the coating using femtosecond laser pulses with infrared wavelengths. A study on ablation characteristics depending on different process parameters such as laser fluence and repetition rate was performed. Special focus was on the ablation efficiency, enabling an optimized process design. The influence of the electrode composition was taken into account by studying the ablation behavior at a varying binder content. Evenly distributed micro holes were chosen in order to keep active material removal at a minimum. To evaluate the effect of structured graphite anodes on the electrochemical properties of lithium-ion batteries, test cells were manufactured and galvanostatically cycled at different current rates. Results show improvements in high-current performance which is expressed by an increased discharge capacity yield.

Binder-free hybrid Li4Ti5O12 anode for high performance lithium-ion batteries

We have developed a new binder-free hybrid anode material for lithium-ion batteries, by directly coating spinel Li4Ti5O12 particles using in-situ polymerization of styrenesulfonate (SS) to form a core-shell structure. The resulting hybrid anode has significantly improved electrochemical performance, with higher reversible capacity, rate-capability, and capacity value compared with pure Li4Ti5O12. Of the initial discharge capacity of 239.2 mAh g−1, 95.6% was retained after 100 cycles at 0.1 C-rate. The high cycle performance with increased discharge capacity is attributed to the coated poly (styrenesulfonate) (PSS) shell, which takes part in lithium ion storage and prevents the growth of a solid electrolyte interface (SEI) layer. The fast electron transfer in PSS also allows high rate-capability. Moreover, we clarify the contribution of carbon conductor in the range of 0.01 V–1.0 V.