Fast Charge Rates Research Articles

Counterion Transport and Transference Number in Aqueous and Nonaqueous Short-Chain Polyelectrolyte Solutions.

Nonaqueous polyelectrolyte solutions have recently been proposed as potential battery electrolytes due to their unique ability to tune the mobility of the anion relative to that of the electrochemically active lithium ion. This could potentially be used to study the effect of concentration polarization during battery charge, a major limiting factor in achieving fast charge rates that is caused by high anion mobility. An important consideration in the design of polyelectrolyte solutions for battery applications is the solubility of the polymer in battery-relevant carbonate blend solvents. Little is understood from a transport perspective, however, about the importance of designing the polymer to be solvophillic or if it is sufficient to obtain solubility through the incorporation of appended ions alone (as with polystyrene sulfonate in water). Using a model polysulfone-based system without added salt, we investigate the conductivity, viscosity, and diffusion of polyelectrolyte solutions over a range of concentrations and molecular weights in dimethyl sulfoxide (DMSO) and water. In both solvents, sulfonated polysulfone is readily soluble and the charged group is known to dissociate, but the neutral backbone polymer is only soluble in DMSO. We find marked differences in the transport behavior of polymer solutions prepared from the two solvents, particularly at high concentrations. Comparing this transport behavior to that of the monomer in solution demonstrates a larger decrease in lithium motion in DMSO than in water, even though the bulk viscosity in water increases far more rapidly. This study sheds light on the important parameters for optimizing polyelectrolyte solution transport in different solvents.

Photolithographic fabrication of graphene-based all-solid-state planar on-chip microsupercapacitors with ultrahigh power characteristics

The fabrication of all-solid-state planar on-chip microsupercapacitors with ultrahigh power characteristics was demonstrated by reduced graphene oxide and photolithography technology. In this paper, an ultrathin reduced graphene oxide film with a thickness of 8 nm was prepared by a modified spin coating method that makes the microsupercapacitors have higher power characteristics which appear in high conductivity and fast charge and discharge rates. The electrodes, with a width of 150 μm, are narrower than existing electrodes in the field and fabricated by photolithography. In terms of performance, these microsupercapacitors have an extremely short time constant which is 0.03 ms, a high power density which is 17.94 W cm−3, and an excellent cycle stability with a capacitance retention of 94.6% after 10 000 cycles.

Improvement of Hard Carbon Electrode Performance by Manipulating SEI Formation at High Charging Rates

There is a growing demand for high-rate rechargeable batteries for powering electric vehicles and portable electronics. Here, we demonstrate a strategy for improving electrode performance by controlling the formation of solid electrolyte interphase (SEI). A composite electrode consisting of hard carbon (HC) and carbon nanotubes (CNTs) was used to study the formation of the SEI at different charging rates in an electrolyte consisting of 1 M NaClO4 in a mixed solvent with ethylene carbonate (EC) and propylene carbonate (PC), as well as fluoroethylene carbonate (FEC) additive. The half-cell method was used to form the SEI at different charging rates (e.g., 1, 10, and 100 A/g). Symmetric capacitor cells were employed to study ion transport properties through the SEI. It was found that the SEI is a primary factor responsible for limiting the capacity of the composite anode material in conventional ester-based electrolytes. The electrode with the SEI formed at 100 A/g exhibited the lowest impedance and delivered nearly twice the capacity of the electrode with the SEI formed at 1 A/g. This significant difference is due to a thin SEI formed at the fast charging rate, as has been observed with ether-based electrolytes. An identical decay rate (0.11 mA h/g per cycle) was observed on the electrodes with SEIs formed at different charging rates in an ester electrolyte. No chemical difference among the three SEI layers was found. However, morphological differences of the SEI layers were observed. This difference is believed to account for the different electrochemical behaviors of the electrodes. This work shows that high charging rates can result in the formation of an optimal SEI layer, contradicting the widely accepted practice of using low charging rates during the SEI formation in alkali-ion batteries.

Combining density functional theory and 23Na NMR to characterize Na2FePO4F as a potential sodium ion battery cathode

Sodium ion batteries offer an inexpensive alternative to lithium ion batteries, particularly for large-scale applications such as grid storage that do not require fast charging rates and high power output. Moreover, the use of polyanionic structures as cathode materials afford incredibly high structural stability relative to layered transition metal oxides that can undergo a structural collapse upon full removal of the charge carrying ions. Sodium iron fluorophosphate, Na2FePO4F, has demonstrated its viability as a potential cathode material for sodium ion batteries, having a robust framework even after multiple charge-discharge cycles. Although solid-state NMR has traditionally been an excellent method for the determination of local structure and dynamic properties of cathode materials during the electrochemical cycling process, reliable assignment of the 23Na chemical shifts resulting from the paramagnetic hyperfine interaction can be difficult when using only empirical rules. Here we present the use of density functional theory calculations to assign the experimentally observed NMR shifts to the crystallographic sites in Na2FePO4F, where it is found that the results do not agree with the previously reported assignment based upon simple geometry arguments. Furthermore, we report the justification of the proposed desodiation mechanism in Na2FePO4F on the basis of theoretical arguments, in good agreement with experimental NMR results reported previously.

Exploration of Li-Organic Batteries Using Hexaphyrin as an Active Cathode Material.

Lithium-collaborating organic batteries (Li-[28]hexs) were investigated with [28]hexaphyrin(1.1.1.1.1.1) as an active electrode material. Each hexaphyrin of [28]Hex cathode ideally involved four electrons per unit cycle and performed a typical charge/discharge processes of Li-organic battery. Li-[28]Hex batteries set with fast charging rates showed reasonably stable charge and discharge performances over 200 cycles even though it caused incomplete (2~3 electrons) charge/discharge cycles due to failing the complete charging process. UV absorption changes of [28]hexaphyrin in CH2Cl2 were supplementary for the electrochemical oxidation, which performed a conversion from [28]hexaphyrin to [26]hexaphyrin.

Infinitesimal sulfur fusion yields quasi-metallic bulk silicon for stable and fast energy storage

A fast-charging battery that supplies maximum energy is a key element for vehicle electrification. High-capacity silicon anodes offer a viable alternative to carbonaceous materials, but they are vulnerable to fracture due to large volumetric changes during charge–discharge cycles. The low ionic and electronic transport across the silicon particles limits the charging rate of batteries. Here, as a three-in-one solution for the above issues, we show that small amounts of sulfur doping (<1 at%) render quasi-metallic silicon microparticles by substitutional doping and increase lithium ion conductivity through the flexible and robust self-supporting channels as demonstrated by microscopy observation and theoretical calculations. Such unusual doping characters are enabled by the simultaneous bottom-up assembly of dopants and silicon at the seed level in molten salts medium. This sulfur-doped silicon anode shows highly stable battery cycling at a fast-charging rate with a high energy density beyond those of a commercial standard anode.

Theoretical prediction of germanium selenium nanosheet as a potential anode material for high-performance alkali-metal based battery

Alkali-metal (AM) ion batteries have been attracting great attention due to the high specific capacity, fast charging rate, and good reversibility. In this work, the adsorption and diffusion of Li, Na, and K atoms on a two-dimensional (2D) group-IV monochalcogenide, germanium selenium nanosheet (GeSeNS), have been systematically investigated by first-principles calculations. The considered AM atoms could form strong binding and exist in stable configuration with GeSeNS. A semiconducting to metallic transition induces an excellent electrical conductivity after AM intercalation on GeSeNS, that is essential for an optimal anode material. Our results show that the low energy barriers of AM atoms diffusion along zigzag direction are 0.329 (Li), 0.175 (Na) and 0.132 (K) eV, respectively, which are lower than values of the commercial graphite anode material and corresponding to ultrafast charge/discharge capability. The average voltages are about 1.82, 1.45 and 1.28 V for the LixGeSe, NaxGeSe and KxGeSe systems, respectively. Hence, our results suggest that GeSeNS could be a potential electrode material for application in low-cost AM ion batteries with a high rate capability and high charging voltage, thus encouraging further experimental work.

Selenium-sulfur (SeS) fast charging cathode for sodium and lithium metal batteries

We report a bifunctional sodium metal battery (SMB) and lithium metal battery (LMB) cathode based on 63 wt.%SeS covalently bonded to a co-pyrolyzed polyacrylonitrile (PAN) host, termed “SeSPAN”. This dense, low surface area, fully-amorphous electrode offers a highly favorable combination of reversible capacity, rate capability, and cycling life: At a fast charging rate of 1 A g−1, the reversible capacities with Na and Li are 632 and 749 mAh g−1 (based on active SeS), with cycle 1 CE of 81% in both cases. At an ultra-fast charging rate of 4 A g−1 (∼5C) the reversible capacities with Na and Li are 453 and 604 mAh g−1. Li-SeSPAN degrades 3% at cycle 500, while with Na-SeSPAN degrades by 17% after 150 cycles at 0.5 A g−1. Both Na and Li cells display a uniquely low voltage hysteresis (210 and 200 mV at a current density of 0.2 A g−1), indicative of facile charge-discharge kinetics. Analysis of the post-cycled anodes shows negligible S or Se crossover, with neither species being detected in the Li-SEI after extended cycling.

Performance of WS2 monolayers as a new family of anode materials for metal-ion (mg, Al and ca) batteries

Abstract We employed first-principle calculations to explore the possibility of using two-dimensional WS2 monolayer, as an anode material for Mg, Ca and Al ion batteries. In this study, we systematically investigated Mg, Ca and Al atoms intercalation and diffusion on the WS2 monolayer. The results show that all the studied metal atoms can be adsorbed on WS2 monolayer and the calculated density of states display metallic character for M@WS2 systems, which ensures good electronic conduction for using as battery electrodes. Study of the selected metals mobility indicates the low/moderate migration barriers on WS2, which confirm excellent cycling performance when acting as the battery electrode. In addition, Mg, Ca and Al are predicted to produce a voltage about 1.50, 1.63 and 3.13 V respectively and maximum capacity about 360.78, 326.09 and 531.58 mA h g−1, respectively. Our results suggest that WS2 monolayer can be employed as a promising anode material for the Mg, Ca and Al ion batteries with high power density and fast charge rates.

Toward Extreme Fast Charging: Challenges and Opportunities in Directly Connecting to Medium-Voltage Line

In this article, we present the current state-of-the-art fast-charging technologies. We discuss the state-of-the art-fast chargers, their design, and their main characteristics. Additionally, we detail how these chargers can be combined to form fast-charging stations that mimic the functionality of a gasoline refueling station. Various power delivery concepts for these charging stations are described, and we discuss the benefits and shortcomings of the current and proposed approaches. Finally, we present a novel approach in which the charging station directly connects to the medium-voltage (MV) line, thus eliminating a number of power electronics conversion stages and the low-frequency step-down transformer. We outline significant benefits of this technology when considering extreme fast-charging rates, and we identify the key technology gaps in making this technology more widely accepted.

Model Based Multiscale Analysis of Film Formation in Lithium‐Ion Batteries

AbstractEvidence for multiscale interaction of processes during surface film growth is provided using a multiscale modeling approach. The model directly couples a continuum pseudo two dimensional (P2D) battery model and a heterogeneous surface film growth model based on the kinetic Monte Carlo (kMC) method. Key parameters have been identified at basic electrochemical experiments, i. e., open circuit potential (OCP), C‐rate tests, and potential during filmformation. Simulations are in very good agreement with these experiments. Simulation results are shown for various formation procedures, i. e., for different applied C‐rates. Interaction between macroscopic transport processes on electrode scale and elementary reaction steps on atomistic scale are observed. Results reveal a distinct impact of the applied procedures on the atomistic structure of surface films. It can be seen that locally heterogeneous films are formed with very slow charging rate due to stochasticity of the growth process, while spatially heterogeneous films are formed with very fast charging rate due to the spatial heterogeneous distribution of concentration and potential. Therefore, the author's emphasize that in order to identify charging protocols for optimal film morphology multiscale interactions should be considered.

Lithium Plating–a Life-Limiting and Safety Issue in a Li-Ion Cell

Despite their advances and widespread use in various applications for the last two decades, Li-ion batteries continue to exhibit occasional failures from Li plating on the anode. Li plating can have immediate effects on performance and more devastating effects upon the safety, if the Li plating occurs in a dendritic form that could pierce through the separator causing an internal short. Even in a benign form, plated Li—lacking the protective SEI that protects the carbon anode —tends to react with electrolyte which results in a rapid growth in interfacial impedance and capacity loss during cycling. Li plating will manifest whenever intercalation kinetics (into carbon) are slower compared to lithium plating over carbon, despite the lower reversible potential of the latter. Poor cell design factors, i.e., improper matching of anode and cathode in terms of electrochemical capacities and geometric aspects with localized hotspots in current distribution, and inappropriate electrolyte, can cause Li plating on the anode. The nature of the anode, electrolyte and SEI are among the most important factors that can influence Li plating.1 Apart from the design/chemical abnormalities, lithium plating is also triggered by the operational conditions, such as fast charge rates and low operating temperatures relevant to planetary space missions. In our earlier study, we have demonstrated that the choice of the electrolyte is critical in determining the propensity towards lithium plating.2 Specifically, these studies indicate that the Li intercalation kinetics are mainly dictated by the anode surface films (SEI), which in turn could be controlled by a judicious selection of electrolyte solution, i.e., both solvent and salt. We have established a correlation between the poor lithium intercalation kinetics and the propensity towards lithium plating using different electrolytes with different solvent blends and different electrolyte additives. Recently, Li plating was observed in cells upon extended cycling at ambient temperature in a Low Earth Orbit (LEO) satellite simulation condition, involving 30 minutes of discharge and 60 minutes of charge continuously, possibly due to impeded intercalation kinetics at the anode. Likewise, exposure to high intensity radiation environments may have led to Li plating in prototype 18650 cells upon subsequent cycling. In this paper, we will discuss the Li plating phenomenon in these specific examples, and with reference to anode/cathode interfacial kinetics at low temperatures in different electrolytes. ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). REFERENCES B. V. Ratnakumar and M. C. Smart, ECS Trans. 25 (36), 241 (2010).M. C. Smart and B. V. Ratnakumar, J. Electrochem. Soc. 2011, 158 (4), A379.

Ultrafast-Charging Silicon-Based Coral-Like Network Anodes for Lithium-Ion Batteries with High Energy and Power Densities

Fast charging rate and large energy storage are becoming key elements for the development of next-generation batteries, targeting high-performance electric vehicles. Developing electrodes with high volumetric and gravimetric capacity that could be operated at a high rate is the most challenging part of this process. Using silicon as the anode material, which exhibits the highest theoretical capacity as a lithium-ion battery anode, we report a binder-free electrode that interconnects carbon-sheathed porous silicon nanowires into a coral-like network and shows fast charging performance coupled to high energy and power densities when integrated into a full cell with a high areal capacity loading. The combination of interconnected nanowires, porous structure, and a highly conformal carbon coating in a single system strongly promotes the reaction kinetics of the electrode. This leads to fast-charging capability while maintaining the integrity of the electrode without structural collapse and, thus, stable cycling performance without using binder and conductive additives. Specifically, this anode shows high specific capacities (over 1200 mAh g-1) at an ultrahigh charging rate of 7 C over 500 charge-discharge cycles. When coupled with a commercial LiCoO2 or LiFePO4 cathode in a full cell, it delivers a volumetric energy density of 1621 Wh L-1 with a LiCoO2 cathode and a power density of 7762 W L-1 with a LiFePO4 cathode.

Recent Progress in Some Amorphous Materials for Supercapacitors

A breakthrough in technologies having "green" and sustainable energy storage conversion is urgent, and supercapacitors play a crucial role in this area of research. Owing to their unique porous structure, amorphous materials are considered one of the best active materials for high-performance supercapacitors due to their high specific capacity, excellent cycling stability, and fast charging rate. This Review summarizes the synthesis of amorphous materials (transition metal oxides, carbon-based materials, transition metal sulfides, phosphates, hydroxides, and their complexes) to highlight their electrochemical performance in supercapacitors.

(Invited) First-Principles Simulation Study on the Nanomaterials for Battery and Solar Cell Applications

Recently, two-dimensional (2D) layered materials have emerged as possible anode materials for lithium ion batteries.1 Among them, the Group IV monochalcogenides are proposed as anode materials in the forms of nano- crystals2 and sheets.3 Herein, by using the density functional theory (DFT), we show that the GeSe monolayer is a promising candidate for an anode material for Na and K ion batteries. The GeSe monolayer is thermodynamically stable and can be experimentally exfoliated from its bulk counterpart.4 Our calculation shows that the GeSe monolayer has fast charge and discharge rates and low voltages suitable for alkali metal ion batteries. The theoretical capacities of Na and K ions are calculated to be 707 and 353 mAh g-1, respectively, which are larger than that of typical 2D anode materials. We also studied the dye sensitized solar cells (DSSCs) by simulating the adsorption of organic5 and organo-metallic6 sensitizers on a (TiO2)16 cluster. The electronic coupling between dye and semiconductor and the position of the TiO2 conduction band are strongly influenced by the dye@TiO2 interface and the adsorption configuration. We studied five organic double-donor-acceptor sensitizers bridged with different alkyl chain spacers to examine the effects of their alkyl chain lengths on the overall efficiency. The adsorption strengths of the dyes on TiO2 were correlated with overall efficiencies. We have also rationalized the effect of cyclometalation of a ruthenium sensitizer, an organo-metallic complex on the electron injection into the semiconductor. The band gap of the semiconductor decreased due to the sharply occupied molecular orbitals of the dye. Also, the LUMOs of the dyes strongly overlap with the TiO2 conduction bands to favor the electron injection. The wider broadening of the LUMO of cyclometalated ruthenium dye signifies the stronger electron overlap and better electron injection into semiconductor over its corresponding non-cyclometalated ruthenium dye. References H. R. Jiang, W. S., M. Liu, L. Wei, M. C. Wu and T. S. Zhao, Boron phosphide monolayer as a potential anode material for alkali metal-based batteries. J. Mater. Chem. A 2017, 5 (2), 672-679.Im, H. S. L., Y. R.; Cho, Y. J.; Park, J.; Cha, E. H.; Kang, H. S., Germanium and Tin Selenide Nanocrystals for High-Capacity Lithium Ion Batteries: Comparative Phase Conversion of Germanium and Tin. J. Phys. Chem. C 2014, 118 (38), 21884-21888.Ramasamy, P. K., D.; Lim, D.-H.; Ra, H.-S.; Lee, J.-S., Solution synthesis of GeS and GeSe nanosheets for high-sensitivity photodetectors. J. Mater. Chem. C 2016, 4 (3), 479-485.Karmakar, S. C., C.; Datta, A., Two-Dimensional Group IV Monochalcogenides: Anode Materials for Li-Ion Batteries. J. Phys. Chem. C 2016, 120 (27), 14522-14530.Lee, Y. H. C., R. K.; Jang, B. Y.; Jang, J.; Thogiti, S.; Kim, J. H., Alkyl chain length dependence of the charge-transfer, recombination and electron diffusion length on the photovoltaic performance in double donor-acceptor-based organic dyes for dye sensitized solar cells. Dyes Pigm. 2016, 133, 161-172.Chitumalla, R. K. J., J., Effects of Cyclometalation on the Panchromatic Ruthenium Sensitizer for DSSC Applications. Bull. Korean Chem. Soc. 2017, 38 (10), 1209-1213.

First-Principles Study on the Gese Monolayer As an Anode Material for Alkali Metal Ion Batteries

Rechargeable Li-ion batteries (LIBs) are extensively utilized for sustainable and renewable energy storage,1 but the high cost and low abundance of lithium have prompted the quest for alternative energy storage systems such as Na and K ion batteries.2 An enhanced gravimetric energy density and a high diffusion rate of carrier ions are important aspects to consider in development of alkali metal ion batteries. Recently, 2D layered materials have emerged as anode materials for batteries.1 Among them, the Group IV monochalcogenides are proposed as anode materials in the forms of nano-crystals3 and sheets.4 Herein, by using the density functional theory calculation, we show that the GeSe monolayer can be an anode material for Na and K ion batteries. The calculations of the phonon dispersion and formation energy prove that the GeSe monolayer is a structurally and thermodynamically stable material which can be experimentally exfoliated from its bulk counterpart.5 The GeSe monolayer shows adsorption energies of 1.92, 1.22 and 1.32 eV, respectively, for Li, Na and K ions. Upon electrodeposition of an alkali metal ion, substantial charge transfers from the metal atom to the GeSe monolayer and the semiconducting GeSe monolayer turns into a metallic state. The GeSe monolayer gives an anisotropic diffusion of the metal ions with moderate/low energy barriers on GeSe (0.29, 0.11 and 0.10 eV along zigzag, respectively, for Li, Na and K) which ensures fast charge and discharge rates. The low average voltages suggest that the GeSe monolayer is a suitable anode for alkali metal ion batteries. The GeSe monolayer yields a capacity of nearly half (177 mAh g-1) of the commercial graphite anode. On the other hand, the theoretical capacities of Na and K ions are calculated to be 707 and 353 mAh g-1, respectively, which are larger than that of typical 2D anode materials. Reference: H. R. Jiang, W. S., M. Liu, L. Wei, M. C. Wu and T. S. Zhao, Boron phosphide monolayer as a potential anode material for alkali metal-based batteries. J. Mater. Chem. A 2017, 5 (2), 672-679.Joshi, R. P. O., B.; Barone, V.; Peralta, J. E., Hexagonal BC3 : Robust Electrode Material for Li, Na, and K Ion Batteries. J. Phys. Chem. Lett. 2015, 6 (14), 2728-2732.Im, H. S. L., Y. R.; Cho, Y. J.; Park, J.; Cha, E. H.; Kang, H. S., Germanium and Tin Selenide Nanocrystals for High-Capacity Lithium Ion Batteries: Comparative Phase Conversion of Germanium and Tin. J. Phys. Chem. C 2014, 118 (38), 21884-21888.Ramasamy, P. K., D.; Lim, D.-H.; Ra, H.-S.; Lee, J.-S., Solution synthesis of GeS and GeSe nanosheets for high-sensitivity photodetectors. J. Mater. Chem. C 2016, 4 (3), 479-485.Karmakar, S. C., C.; Datta, A., Two-Dimensional Group IV Monochalcogenides: Anode Materials for Li-Ion Batteries. J. Phys. Chem. C 2016, 120 (27), 14522-14530.

Thermal behavior analysis of stacked-type supercapacitors with different cell structures

As a new energy storage element, supercapacitors have characteristics such as high power density, fast charge and discharge rates, green environmental protection, and long cycle life. Temperature is an important parameter of supercapacitors which significantly influences the stability of the supercapacitors. In this study, the finite element method is used to realize a coupling between a one-dimensional electrochemical model and a three-dimensional thermal model. Then, based on this model, the concept of limited cycle numbers is defined, and different unit quantities, unit size, and the effect of temperature under different temperature environments such as low temperature, room temperature, and high temperature on stacked-type supercapacitors is studied. Finally, stacked-type supercapacitors are compared with rolled-type supercapacitors considering the same cell size, density, and volume approximations. The simulation results show that the higher the number of packaging units, the lower is the limit cycle number. This phenomenon is more pronounced under high current than under low current conditions. Increasing the package size of the porous electrode or separator decreases the limiting cycles. Under the same unit volume scenario, improving the separator size proportion can accurately control the temperature rise at small current values. Under the same material, volume, and density approximations, the temperature rises slowly for stacked-type supercapacitors as compared to rolled-type supercapacitors. This phenomenon is more pronounced with an increase in current.

Ag-coated one-dimensional orthorhombic Nb2O5 fibers as high performance electrodes for lithium storage

In the recent times, pseudocapacitive electrode materials have received great attention due to their considerable capability in storing ions at relatively fast charging rates. Among various candidates, niobium (V) pentoxide (Nb2O5) has gained much attraction for lithium-ion batteries (LIBs) due to its insertion/extraction reaction with Li, safe redox potential, and considerably good capacity (about 200 mAhg−1). Nevertheless, low conductivity of Nb2O5 has so far prevented its use as a viable electrode material for LIBs. In this study, we have successfully coated silver (Ag) nanoparticles (NPs) on the surface of one-dimensional orthorhombic Nb2O5 fiber (1D T-Nb2O5) using simple electrospinning processing. Ag NPs coated Nb2O5 fibers (Ag-1D T-Nb2O5) provided faster electron pathways, resulting in much improved capacity at a given current density with superior rate capabilities compared with pristine 1D T-Nb2O5. In addition, 1D T-Nb2O5 was more suitable for coating Ag NPs compared with T-Nb2O5 NPs, where its structural integrity was maintained even after cycling. As a result, effective coating of conductive Ag NPs on the 1D T-Nb2O5 resulted in excellent cycle retention characteristics (179.7 mAhg−1 after 500 cycles at 500 mA g−1) as well as superior rate capabilities (103.6 mAhg−1 at a current density of 5000 mA g−1).

Mesoporous TiO2 microparticles formed by the oriented attachment of nanocrystals: A super-durable anode material for sodium-ion batteries

Spindle-shaped anatase TiO2 secondary particles were successfully fabricated via the oriented attachment of primary nanocrystals. By adjusting the concentration of tetrabutyl titanate, the size of the TiO2 nanocrystals and particles could be controlled, resulting in pore evolution. Pores for the random aggregation of secondary particles gradually transformed to nanopores originating from the oriented attachment of the primary nanocrystals, resulting in an excellent micro/nanostructure that increased the performance of a sodium-ion battery. The mesoporous TiO2 microparticle anode, with its unique combination of nanocrystals and uniform nanopores, displays super durability (95 mAh/g after 11,000 cycles at 1 C), high initial efficiency (61.4%), and excellent rate performance (265 and 77 mAh/g at 0.1 and 20 C, respectively). In particular, at slow discharge (0.1 C) and fast charge (5, 50, and 100 C) rates, the anatase TiO2 shows remarkable initial charge capacities of 200, 119, and 56 mAh/g, corresponding to 172, 127, and 56 mAh/g, after 150 cycles, respectively, thus meeting the requirements for fast energy storage. This excellent performance can be attributed to the stability of the material and its high ionic conductivity, resulting from the stable architecture with a mesoporous microstructure and without the random aggregation of secondary particles. A fundamental understanding of the pore structure and controllable pore construction has been proven to be effective in increasing the rate capability and durability of nanostructured electrode materials.

Bioinspired sea-sponge nanostructure design of Ni/Ni(HCO3)2-on-C for a supercapacitor with a superior anti-fading capacity

Rational design of novel structures plays a key role in achieving high specific capacities and fast charge rates with a long cycling life for battery-type electrodes of supercapacitors.