Good Cycle Life Research Articles

Facile and large-scalable synthesis of low cost hard carbon anode for sodium-ion batteries

Although hard carbons are considered to be applied as promising anode materials for sodium-ion batteries (SIBs) with improved specific capacity and good long-term cycle life. However, a significant low initial Coulombic efficiency (ICE) and high cost that consequently impede its use in future commercialization of SIBs. Herein, a cost effective strategy is used to prepare the large-scalable hard carbon (HC) anode material for SIBs, which shows excellent initial reversible capacity of 308 mA h g−1 under the current rate of 50 mA g−1 and considerable higher ICE of 78%. After more than 300 cycles, the material exhibits a specific capacity of 160 mA h g−1 and presenting superior capacity retention more than 94% under current density of 500 mA g−1. The obtained results establish a new technique to construct low cost hard carbon based anode materials for next-generation high performance SIBs.

Dendrite-Free Lithium Anodes with Ultra-Deep Stripping and Plating Properties Based on Vertically Oriented Lithium-Copper-Lithium Arrays.

Although lithium metal is the best anode for lithium-based batteries, the uncontrollable lithium dendrites especially under deep stripping and plating states hamper its practical applications. Here, a dendrite-free lithium anode is developed based on vertically oriented lithium-copper-lithium arrays, which can be facilely produced via traditional rolling or repeated stacking approaches. Such vertically oriented arrays not only enable both the lithium-ion flux and the electric field to be regulated, but also can act as a "dam" to guide the regular plating of lithium, thus efficiently buffering the volume change of the lithium anode upon cycling. As a consequence, the vertically oriented anode exhibits an excellent deep stripping and plating capability upto 50 mAh cm-2 , high rate capabilities (20 mA cm-2 ), and long cycle life (2000 h). Based on this anode, a full lithium battery with a LiCoO2 cathode delivers a good cycle life, holding great potential for practical lithium-metal batteries with high energy densities.

Low-cost and eco-friendly synthesis of octahedral LiMn2O4 cathode material with excellent electrochemical performance

Abstract Here, high-performance LiMn2O4 particles of octahedral morphology with exposed (111) planes were synthesized via an easy, inexpensive and eco-friendly process using octahedral-shaped Mn3O4 as precursor, which was fabricated by reacting potassium permanganate (KMnO4) with a tiny amount of ethylene glycol (C2H6O2) using the hydrothermal method. Without cation doping and surface modification, the octahedral LiMn2O4 particles showed very good cycling life and outstanding high-temperature performance. When cycled at 1.0 C, it exhibited a desirable capacity of 123.6 mAh g−1 (Retention after 200 cycles: 93.7%). At high rate of 10 C, this material delivered 85.7 and 85.3 mAh g−1 discharge capacities with excellent retentions of 94.7% and 90.5% after 200 cycles at 25 and 55 °C, respectively. Such impressive performance was obtained largely from the unique octahedral morphology with exposed (111) planes, high crystallinity and uniform particle size distribution, which effectively mitigated the dissolution of manganese, maintained the structural stability and accelerated the diffusion of lithium ions.

Magnesium–Graphene Composite Coated on SS Mesh as Cathode Material for Rechargeable Magnesium ion Battery

Rechargeable magnesium battery with a magnesium anode and magnesium–graphene (Mg–G) composite coated on SS mesh as cathode and ionic liquid electrolyte was developed. Magnesium–graphene composite was prepared by using the semi-metallurgy method. The composite was analyzed by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction studies. The electrochemical performance of magnesium–graphene composite was analyzed by cyclic voltammetry, impedance spectroscopy, and charge–discharge studies. The cyclic voltammetry of Mg–G cell showed good reversibility, and impedance spectra revealed reduced resistance of the cell. The cell-specific capacity was 55 mAh g−1, and average discharge voltage was 1.15 V at 0.1 mA cm−2 constant current. The cell showed good cycle life (80 cycles) indicating stable discharge capacity and electrochemical behavior.

Highly dense perovskite electrolyte with a high Li+ conductivity for Li–ion batteries

A solid Li+ electrolyte, which has a high Li+ conductivity at 25 °C and a high density, is required in rechargeable Li–ion batteries including all–solid–state Li–metal batteries and Li–redox flow batteries. Here we prepare a fast cubic perovskite Li+ conductor, Li3/8Sr7/16Ta3/4Hf1/4O3 (LSTH), by reducing the grain boundary resistance with spark plasma sintering. The influence of the sintering temperature and time on the relative density and the total Li+ conductivity of Li3/8Sr7/16Ta3/4Hf1/4O3 are investigated; the LSTH pellets sintered by SPS at 1250 °C for 10 min has a much higher density (96.5%), a higher Li+ conductivity (5.2 × 10−4 S cm−1) at 25 °C and a lower activation energy (0.33 eV) than the Li3/8Sr7/16Ta3/4Hf1/4O3 pellet fired with conventional sintering. The symmetric Li/Li cell with a LSTH membrane, which is coated by a thin Li+–conducting solid polymer to avoid the chemical reduction of Li3/8Sr7/16Ta3/4Hf1/4O3 by a metallic lithium anode and to homogenize the current density at Li/electrolyte interface, shows a stable cycling at 0.3 mA cm−2; the all–solid–state Li/LiFePO4 battery and the Li–S cell with Li3/8Sr7/16Ta3/4Hf1/4O3 membranes show a high coulombic efficiency and a good cycling life.

(Keynote) Developing High Voltage Li-Ion Batteries Based on Lithium Cobalt Phosphate (LCP)

Olivine structured lithium cobalt phosphate, LiCoPO4 (LCP), is an attractive cathode material that has a theoretical energy density of 802 Wh/kg based on LCP’s 4.8 V redox potential and 167 mAh/g theoretical capacity. The investigation of this material was first reported in 2000 by Amine et al. [1] realizing a capacity of only 70 mAh/g. The low capacity was attributed to both the poor electronic conductivity of LCP and the initiation of the electrolyte salt decomposition [1]. Considerable efforts worldwide since then made on improving the utilization of LCP through the reduction of particle size, carbon blending, carbon coating and morphology improvement have led to an increase of capacity utilization to 140 mAh/g [2]. Efforts have also been made in developing compatible high voltage electrolytes [3]. However, these efforts had not resulted in a rechargeable LCP without substantial loss of capacity in limited cycles. A breakthrough in improving the cycle life of LCP against Li up to 500 times with 80% capacity retention was made by substituting part of Co by Fe, which was first reported by Allen et al. in 2011 [4]. Further substitutions by Cr and Si in Fe substituted LCP (s-LCP) with improved electrolyte improve the discharge capacity to 140 mAh, coulombic efficiency to 99.7% and cycle up to 250 times with almost no capacity fade [5]. The success in realizing the potential of this material is attributed to the success in modifying the electronic structure and stabilizing the electrochemical stability of LCP through atomic level substitutions. Good cycle life has also been demonstrated in full cells made of graphite anode and s-LCP cathode in coin cells and 1.2 Ah pouch cells [6]. This talk will present a progression of the s-LCP based Li-ion cells development and the importance of the atomic level engineering in improving the performance of the high voltage cathodes. References K. Amine, H. Yasuda, M. Yamachi, Olivine LiCoPO4 as 4.8 V Electrode Material for Lithium Batteries, Electrochem. Solid-State Lett. 2000, 3(4) 178-179.S.-M. Oh, S.-T. Myung, Y.-K. Sun, Olivine LiCoPO4–carbon composite showing high rechargeable capacity, J. Mater. Chem., 2012, 22, 14932.R. Sharabi, E. Markevich, K. Fridman, G. Gershinsky, G. Salitra, D. Aurbach, G. Semrau, M. A. Schmidt, N. Schall, C. Bruenig, Electrolyte solution for the improved cycling performance of LiCoPO4/C composite cathodes. Electrochem. Commun. 2013, 28, 20-23.J. L. Allen, T. R. Jow, J. Wolfenstine, Improved cycle life of Fe-substituted LiCoPO4, J. Power Sources, 2011, 196(20), 8656-8661.J. L. Allen, J. L. Allen, T. Thompson, S. A. Delp, J. Wolfenstine, T. R. Jow, Cr and Si Substituted-LiCo0.9Fe0.1PO4: Structure, Full and Half Li-ion Cell Performance, J. Power Sources, 2016, 327, 229-234.D. Liu, W. Zhu, C. Kim, M. Cho, A. Guerfi, S. A. Delp, J. L. Allen, T. R. Jow and K. Zaghib, High-Energy Lithium-Ion Battery Using Substituted LiCoPO4: From Coin Type to 1Ah Cell, J. Power Sources, 2018, 388, 52-56.

Real-Time Operando SEM Investigation into Lithium Ion Battery Degradation

Lithium ion batteries (LIBs) are the preferred rechargeable battery choice for a range of electric technologies, and have increasingly become an integral part of our lives due to their high energy density, low memory effect, low self-discharge and good cycle life during operation. However, they are complicated by a variety of chemical, electrochemical and physical processes that take place within dynamic microstructures (anodes and cathodes). Hence, extensive research efforts are being invested in improving existing battery components, but greater fundamental understanding within these processes remains critical for optimising the battery design and addressing issues such as safety, long cycle life and efficiency. An attractive approach is to couple a powerful microscopic characterisation technique with electrochemical operation, enabling critical studies with direct real-time monitoring around capacity fading issues, such as dendrite formation and physical degradation under realistic conditions to be carried out. These studies enable correlations between physical and chemical processes to the electrochemical responses of a battery, producing powerful information, leading to a better understanding of LIB degradation processes. One effective example is the coupling of scanning electron microscopy (SEM) with electrochemistry, enabling information on structure, morphology, composition and performance to be acquired at electrode surfaces, under operando conditions, during the course of experiment and down to μm resolution. In recent years, several studies have reported on attempts to investigate degradation in real-time employing SEM coupled with electrochemistry. However, these studies have either exposed battery material to atmospheric moisture or have required the use of alternative electrolytes to that generally employed in real battery systems, e.g. ionic liquids or the use of polymeric electrolytes. In order to simulate real conditions, a bespoke in situ coin cell design has been designed in order to visualise electrode/electrolyte interfaces and capture morphological changes at μm resolution. The fabrication steps protect the battery material (particularly important for the nickel-rich cathode) from exposure to moisture in the air, and during cycling to avoid degradation of typical battery electrolytes. This ensures maximum investigation possibilities including dendrite growth, where the morphology variations and growth extent can be characterised and correlated with electrochemical data. The electrochemical activity of the bespoke coin cell is compared to that of a conventionally fabricated coin cell battery. The degradation processes under a range of operando conditions is explored by varying the temperature of the sample stage or the pressure of the SEM chamber. This study gathers information by characterising electrode structures in order to compare microstructural architecture with performance. The results are expected to enhance our understanding of the processes taking place that lead to electrode degradation and failure, therefore contribute to improvements in the design of LIB materials and their processing, which in turn will positively impact cell performance.

Electrochemical Analysis of the Printed NiCo2O4 // Reduced Graphene Oxide Solid-State Hybrid Supercapacitors on Fabric Substrates for Wearable Applications

The rapid developments of the wearable or body-integrated electronics and boom in the portable healthcare devices have increased the demand of the wearable energy storage devices [1-3]. Inkjet printing is an emerging technology to transfer the device components on the variety of the substrates at the specific locations. However, achieving the good electrochemical performance of the printed electrode materials on wearable substrates is still a major challenge [4, 5]. Here we report a printed, binder-free, flexible, and high-performance NiCo2O4// Reduced Graphene Oxide (rGO) battery- supercapacitor hybrid device on cotton fabric substrates. A thin layer of polydimethysiloxane (PDMS) polymer was applied over the textile fabric for surface planarization. The NiCo2O4 micro-flower arrays were successfully fabricated over this cloth substrates using printing and low-temperature heat treatment method and further treated with the UV irradiation. The crystalline and conducting NiCo2O4 micro-flower array layer acts as a self-supporting electrode, and its open space structure ensures the fast electron transport and full utilization of the electrode surface. The printed NiCo2O4 // rGO asymmetric device with the LiCl –PVA gel electrolyte displays good electrochemical performance within a potential window of 0 to 1.6 V. The fabricated device exhibited excellent electrochemical performance including high areal capacitance of 7.2 F/cm2 (2650 F/g) at a current density of 1 mA/cm2, good cycle life (89 % capacitance retention after 5000 charge-discharge cycles), high rate capability, high power density, high energy density, and low charge transfer resistance both in the normal and flexed conditions. The obtained results are comparable to the existing literature for the high temperature processed NiCo2O4 based energy storage devices, and therefore the reported method has a great potential for the direct fabrication of electrode materials over the temperature sensitive fabric substrates. These fabric based supercapacitors can be easily integrated with the various flexible and wearable devices and exhibit the great beneficial for the next generation of the wearable electronic devices. References Zeng, W., et al., Fiber‐based wearable electronics: a review of materials, fabrication, devices, and applications. Advanced Materials, 2014. 26(31): p. 5310-5336.Kim, J., et al., Advanced materials for printed wearable electrochemical devices: A review. Advanced Electronic Materials, 2017. 3(1): p. 1600260.Bandodkar, A.J., Wearable biofuel cells: Past, present and future. Journal of The Electrochemical Society, 2017. 164(3): p. H3007-H3014.Sundriyal, P. and S. Bhattacharya, Inkjet-Printed Electrodes on A4 Paper Substrates for Low-Cost, Disposable, and Flexible Asymmetric Supercapacitors. ACS applied materials & interfaces, 2017. 9(44): p. 38507-38521.Choi, K.-H., D.B. Ahn, and S.-Y. Lee, Current status and challenges in printed batteries: toward form factor-free, monolithic integrated power sources. ACS Energy Letters, 2017. 3(1): p. 220-236.

Understanding of Correlation between Li Diffusion and Local Environments in Solid Electrolyte Based on Kinetic Energy Barriers As Local Structure Variations By First Principles Calculation

Recently, demands on energy storage systems of high capacity and efficiency are continuously increased as the growth in commercialization of new renewable energy generation, such as wind and solar power, electric vehicle and portable electronic devices. Li-ion battery(LIB) has been introduced in diverse electronic products as one of the promising energy storage devices because of good energy density and long cycle life to answer these demands. For these reasons, study on LIB actively progressed to improve the performance of LIB. However, there are critical obstacles to make advance in energy density, such as increase in voltage and capacity, of conventionally used LIB. The commercialized LIB system use liquid electrolytes as for Li-ion migration between two electrodes. This liquid electrolyte deteriorate the stability of LIB, bring about overheating and explosion as temperature changes originated mainly from increase in operating voltage. In addition, leakage of organic based liquid electrolyte from the inside of LIB could have noxious effect on health. Therefore, alternatives on liquid electrolyte have been highly required to resolve these limitations. As increase in efforts to develop new electrolyte types, Inorganic solid electrolytes have received attentions to substitute it for liquid electrolytes. Inorganic solid electrolytes is one of the promising alternatives of liquid electrolyte because of their excellent thermal stability and good Li ion conductivity. Among inorganic electrolytes, Li10GeP2S12 (LGPS) indicates the great Li ion conductivity to be comparable with Li ion conductivity of liquid conductivity. Despite of this superior Li ion conductivity, the understanding of mechanism for Li ion diffusion in LGPS has not been clearly understood. This study explains correlation between Li ion diffusion and local environments of LGPS to understand mechanism of Li ion migration by first principles calculation. LGPS has enough Li ion concentrations and two types of migration paths. Li ion could migrate in frameworks of Ge-S and P-S(fig.1a). These frameworks secure c-axis and ab-plane paths for Li ion diffusions. There are also two types of methods for first principles calculation of Nudged Elastic Band(NEB) method of Li ion diffusion. One is defect migration (single ion migration) and the other is multi ion concentration migration(fig.1). Firstly, defect migration was analyzed by NEB. We setup three local environments for understanding the correlation in c-axis direction migration. The three situations are only one Li ion without any other Li ions in LGPS(fig.1b), one Li ion in the migration path around Li ions existent in the other non-migration paths(fig.1c) and only one vacancy with existent of Li ions in the migration path(fig.1b). Although the first and second cases of Li ion migration indicates similar tendency and energy barrier for Li ion migration, the third case shows that energy barrier in same migration path is more higher than the energy barrier of the other cases. This means that the factor influencing the Li ion diffusion is not the local Li ions in non-migration path but the near Li ions in the migration path. In addition to single ion diffusion, multi ion concentration migration is examined and this type has no vacancy and assumes that the all Li ions in the path diffuse all together. The energy barrier is lower than the energy barrier in all of single ion migration cases(fig.1f). This indicates that simultaneous migration of all Li ions in migration path is energetically beneficial. The ab-plane migration has two migration paths and the energy barriers are relatively higher than the energy barrier of c-axis migration path(fig.1e). This means that Li ion migration is mainly progressed in c-axis rather than ab-plane regardless of local environments in LGPS. Therefore, this understanding of mechanism for Li ion diffusion in LGPS would be effective guide line for developing the superior inorganic solid electrolyte based on LGPS. Figure 1

Inhibiting Thermal Runaway in Large Format Li-Ion Batteries

NOHMs Technologies is developing novel safe solvent hybrid electrolytes for safe, high energy density, high voltage, and high-power lithium-ion batteries for mobility and consumer applications. Over the past 25 years there has been a proliferation in the use of lithium ion technology and with that ever-increasing market demand for higher energy density cells – demand primarily met by advancements in the cathode and anode. This proliferation has come with the increased rise of safety concerns. There have been high profile incidents of what is known as thermal runaway across a wide variety of applications ranging from consumer electronics to electric vehicles. It is well understood that thermal runaway occurs when the self-heating rate in the cell exceeds the heat dissipation out of the cell. This self-heating is the product of undesired side-reactions in the cell which are onset by abuse conditions such as excess heat, internal short circuits, etc. The key to inhibiting thermal runaway is to modify the cell such that the self-heating rate under abuse conditions is significantly reduced. Reducing the self-heating rate is important when considering battery packs that consist of many cells as is the case in electric vehicles, so that if one cell fails in a pack the thermal runaway does not propagate to adjacent cells. Given that market trends are moving away from low energy electrodes, our approach therefore is to modify the electrolyte system to reduce the overall cell self-heating rate. This is a tunable, drop-in solution to addressing the need for improving battery safety. The incorporation of NOHMs novel safe solvents into the electrolyte formulation is shown to impact the abuse tolerance of cells on both the material level, i.e. the electrolyte-electrode interaction and on the cell level. The presented electrolyte systems demonstrate reduced overall energy and peak heat flow in the exotherm profiles of high-nickel cathode materials as well as lithiated graphite via differential scanning calorimetry (DSC). With this approach, we demonstrate significantly lower self-heating rates in an accelerating rate calorimeter (ARC) heat-wait-seek test on 30 Ah and above high-nickel cathode lithium ion cells. Combined with good rate capability and cycle life NOHMs’ novel safe solvents present an improvement in battery safety without compromising battery performance. This approach carries significance in not just safer individual cells but also in safer overall battery packs.

The Impact of Radiation Exposure upon Lithium-Ion Batteries for Future Planned NASA Missions to Europa

NASA is planning to launch a mission entitled the Europa Clipper which is intended to provide a detailed reconnaissance of the Jovian icy moon Europa. With one major objective being to determine the habitability of life on the moon, the mission will involve multiple flybys and will utilize a number of instruments, including an ice-penetrating radar that is intended to measure the thickness of the icy shell and possibly detect a subsurface ocean. As one would expect due to distances involved, the destination of Europa presents a number of technical challenges for the spacecraft, including being exposed to high levels of radiation and extreme temperature environments. Furthermore, NASA has stringent planetary protection protocols that must be followed that involves sterilizing the spacecraft to to avoid any potential contamination. As described previously1,2, the current power subsystem architecture for the Europa Clipper mission involves the use of solar arrays, power management electronics, and a rechargeable lithium-ion battery.3 With respect to the Li-ion battery, we are planning to utilize a “small cell” approach, which will consist of multiple high specific energy small 18650-size Li-ion cells that are assembled into large capacity multi-string batteries. Due to the excellent cell-to-cell reproducibility and proper cell matching, individual cell monitoring and balancing circuitry is not required with this approach. NASA has previously utilized this approach on a number of past missions, including Kepler, Aquarius, and SMAP. To meet the challenging mission requirements, we identified leading candidate cell chemistries that are projected to meet the mission requirements. However, in contrast to these previous missions which have utilized heritage Sony HCM 18650 cells, we are planning on using much higher specific energy cells to reduce the overall spacecraft mass. Given that we would like to use a new cell chemistry, it necessitates performing a cell qualification activity. Furthermore, the candidate cell chemistry must be demonstrated to have good cycle and storage life characteristics, especially since the cruise period to Europa is extremely long and could potentially be over 6.5 years in duration, depending upon the launch vehicle selected. To reduce the bio-burden of spacecraft components, dry heat microbial reduction (DHMR) is typically employed, which involves subjecting the samples to exposure at high temperatures (in excess of 150oC). However, since Li-ion cell technology will rapidly degrade at high temperatures, this methodology is not acceptable and alternative methods of achieving sterility must be adopted. The preferred method with respect to the Li-ion batteries is to subject them to high levels of gamma-irradiation, which has previously been demonstrated to have a minimal to low impact upon the performance characteristics.4,5 To assess the impact that would be sustained by exposure to γ-rays prior to launch to comply with planetary protection protocols, as well as to address the radiation exposure during the course of the mission, we have exposed a number of Li-ion cells and a large capacity battery module to gamma-irradiation (60Co source) at very high levels (up to 20 Mrad) to evaluate the potential impact. In order to demonstrate the impact of irradiation, a number of performance characterization tests were implemented on samples subjected to varying levels of γ-rays (either 12 Mrad or 20 Mrad), including: (i) 100% DOD cycling under various conditions, (ii) charge and discharge rate characterization over a range of temperatures, (iii) module level testing and, (vi) verification of proper functionality of internal safety protection devices. As will be discussed, good performance has been obtained with candidate high specific energy Li-ion cells, and minimal capacity loss was observed after being subjected to high levels of radiation. 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) and supported by the Europa Clipper Mission. A. Ulloa-Severino, G. A. Carr, D. J. Clark, S. M. Orellana, R. Arellano, M.C. Smart, B.V. Ratnakumar, A. Boca, and S. F. Dawson. October 5, 2016. F. C. Krause, A. Lawrence, M. C. Smart, S. F. Dawson, A. Ulloa-Severino, and B. V. Ratnakumar, 227th ECS Meeting, May 28, 2015. M. C. Smart, F. C. Krause, A. Lawrence, B. V. Ratnakumar, A. Ulloa-Severino, and R. C. Ewell, 232th ECS Meeting, October 5, 2017. B. V. Ratnakumar, M. C. Smart, L. D. Whitcanack, E. D. Davies, and K. B. Chin, J. Electrochem. Soc., 151 (4), A652- A659 (2004). B. V. Ratnakumar, M. C. Smart, L. D. Whitcanack, E. D. Davies, K. B. Chin, F. Deligiannis, and S. Surampudi, J. Electrochem. Soc., 152 (2), A357- A363 (2005).

Hollow NiCoSe2 microspheres@N-doped carbon as high-performance pseudocapacitive anode materials for sodium ion batteries

Transition metal selenides (TMSs) have been considering as a kind of promising alternative anode materials for the application of sodium ion batteries due to their high electrical conductivity and high capacity. Here, hollow NiCoSe2 microspheres was prepared via an easy hydrothermal method, followed by the dopamine derived N-doped carbon coated which formed the hollow NiCoSe2@C composite. As-prepared hollow NiCoSe2@C composite has been first used as a new anode material for sodium ion batteries (SIBs). Our selenides displays a quite good electrochemical sodium storage performance. For example, the reversible capacity of as-prepared hollow NiCoSe2@C composite electrode can be maintained at 464.7 mAh g−1 at a current density of 100 mA g−1 after 200 cycles. Moreover, the rate performance of the hollow NiCoSe2@C composite is outstanding. The reversible capacities of 425.3, 420.8, 403.2, 394.7, 378.7, 367.8 and 337.5 mAh g−1 can be achieved at the current densities of 100, 200, 500, 1000, 2000, 3000 and 5000 mA g−1, respectively. Meanwhile, hollow NiCoSe2@C composite electrode exhibits a high discharge capacity of 338 mAh g−1 at a relatively high current density of 0.5 A g−1 after 250 cycles. In addition, the kinetic analysis of electrochemical Na + storage properties of the hollow NiCoSe2@C composite demonstrates that the extrinsic pseudo capacitive behaviour contributes significantly to excellent rate performance and good long-term cycling life. This method can be used to modify the morphologies and structures of the other TMSs for the development of new anode materials as anode materials in the application of sodium ion batteries.

Facile electrodeposition of MFe2O4 (M=Co, Fe) on carbon cloth as air cathodes for Li-O2 batteries

To develop high energy Li-O 2 batteries (LOBs), it is important to optimize the air cathode structure. Therefore, MFe 2 O 4 @carbon cloth (M = Co, Fe) has been prepared by electrodeposition to be an effective cathode for LOBs. This cathode can effectively avoid the disturbance of a polymer binder during the discharge-charge process. Electrocatalytic and electrochemical measurements show that MFe 2 O 4 @carbon cloth can enhance the ORR/OER kinetics. In particular, CoFe 2 O 4 @carbon cloth exhibits a good initial discharge specific capacity (7259 mA h/g at 170 mA/g) and long cycle life (over 100 cycles at the upper limit specific capacity of 500 mA h/g at 170 mA/g). The favorable electrocatalytic properties of CoFe 2 O 4 @CC are ascribed to the presence of Co 2+ .

Black phosphorus nanosheets promoted 2D-TiO2-2D heterostructured anode for high-performance lithium storage

A novel 2D-TiO2-2D van der Waals (vdW) heterostructured (BPNs@TiO2@G) hydrogel is developed as a high-performance anode material for lithium ion batteries by coating black phosphorus nanosheets (BPNs) onto porous graphene/TiO2 composite hydrogel (TiO2@G). This unique 2D-TiO2-2D vdW heterostructure not only prevents close restack between 2D nanosheets, but also provides rapid interlayer transfer paths and enhanced interfacial storage, together with some inherited advantages from 2D BPNs and graphene, such as shortened diffusion pathways, improved conductivity, supressed volume changes and lithium dendrite growth over cycling. As a result, BPNs@TiO2@G anode delivers an attractive initial discharge capacity as high as 1336.1 mAh g−1 (at 0.2 A g−1), a superior rate capability (271.1 mAh g−1 at 5.0 A g−1), and a good cycling life (502 mAh g−1 for 180 cycles) under a potential window close to 3.0 V. This study thus opens a new window for designing novel high-performance electrodes for electrochemical energy storage devices.

N-functionalized graphene quantum dots: Charge transporting layer for high-rate and durable Li4Ti5O12-based Li-ion battery

Spinel Li4Ti5O12 can replace carbon in Li-ion battery anodes due to its high voltage, preventing decomposition of the electrolyte and formation of Li metal dendrites. However, Li4Ti5O12 has a low electronic conductivity and Li-ion diffusion coefficient, limiting its charge/discharge properties at high rate capacities, and also suffers from gassing during cycling. Here, we used N-functionalized graphene quantum dots interfacial layer, which (1) protects Li4Ti5O12 from ambient degradation, (2) forms a thin and smooth solid-electrolyte interphase layer on the Li4Ti5O12 surface, (3) acts as a charge transfer layer, (4) protects the Li4Ti5O12 electrode from reactions with the electrolyte, and (5) suppresses gassing during cycling. Consequently, the Li-ion diffusion coefficient increased by ∼19%. The effectiveness of the N-functionalized graphene quantum dots is manifested in the specific capacity of 161 mAh/g at 50C, which is improved by ∼23% compared to pure Li4Ti5O12 electrode and maintained for over 500 cycles. Unlike graphene, N-functionalized graphene quantum dots themselves work as a stable charge transporting and protecting layer. Our strategy successfully obtained a good cycling performance and long cycling life of Li4Ti5O12 at high C-rates.

Three dimensional CoMoO4 nanosheets on Nickel foam for high performance supercapacitors

Here we proposed novel CoMoO4 nanosheets on nickel foam that used as a superior electrode for supercapacitors, with an excellent pseudocapacitive performance. The CoMoO4 nanosheets based electrode provide high values of specific capacitance of 1.12 F/cm2 corresponding to the current densities of 4 mA/cm2. It exhibited good cycling life that the specific capacitance maintained with no decrease during 3000 cycles. Our work can be applied in mass applications of high-capacitance energy-storage supercapacitors.

Porous polyaniline/carbon nanotube composite electrode for supercapacitors with outstanding rate capability and cyclic stability

Polyaniline (PANI) is one of the most widely used organic electrode materials for supercapacitors. It has advantages such as good environmental stability and low cost, whereas it is difficult to achieve high capacitance, good rate capability and long cycle life simultaneously. In this work, a series of porous polyaniline/carbon nanotube (PANI/CNT) composite materials are prepared by chemically grafting PANI on CNTs and creating interpenetrating pores via templating using CaCO3 nanoparticles, and then studied as electrode materials for supercapacitors. As PANI is covalently grafted on CNT networks formed in the electrode, the delocalization of electrons improves electron transport in the electrode and the stability of PANI in redox cycling process. The porous morphology created provides sufficient channels for the transport of ions. As a result, the optimized PANI/CNT composite exhibits a high capacitance of 1266 F g−1 at a specific current of 1 A g−1, and even at a specific current of 128 A g−1 the specific capacitance could reach 864 F g−1. Moreover, after cycling tests of 10,000 cycles, it remains 83% of its capacitance at the first cycle. The excellent rate performance and cycle stability of the porous PANI/CNT composite makes it a promising high-performance electrode material for supercapacitors.

(Invited) Advanced Lithium Ion Batteries with Cobalt Free Cathode Materials

Lithium ion batteries are widely used in many applications and are the most promising energy storage systems for future mobility. The development of cobalt free cathode materials with high capacity and high voltage can contribute significantly to further cost reduction and better safety compared to lithium ion batteries with Nickel rich layered oxides like NMC622 or NMC811 as cathode material. We report the synthesis and characterization of a series of Co-free, Li-rich Li1+xNi0.5Mn1.5O4 (0<x<1) cathode materials obtained via a low-temperature synthesis method. These materials give high reversible capacities up to 250 mAh/g cycled between 2.4 and 4.9 V vs. Li/Li+, high rate capability and good cycling life. Th cycling stability can be further improved by optimizing morphology, particle size distribution and additional surface coating and proper selection of electrolyte. Full cell data of these cathode materials in combination with graphite or silicon/carbon composites as anodes demonstrate 15 to 20% higher specific energy compared to reference cells using NCM622 as cathode material, excellent rate capability, better safety and good cycling life.

(Keynote) A Path Forward to Low-Cobalt or Cobalt-Free Cathodes for Lithium-Ion Batteries

Lithium-ion batteries have become the choice of power source for portable electronics as they offer much higher energy density than other rechargeable systems. They are also in the process of transforming the transportation sector and beginning to penetrate the utility industry for grid storage of electricity produced from renewable sources like solar and wind. The lithium-ion battery industry is now based on layered LiMO2 cathodes with fractions of M = Mn, Co, and Ni as each of them has its own advantages and disadvantages. For example, Mn offers good chemical stability without oxygen release, while Co suffers from oxygen release on charging LiCoO2 beyond ~ 50% as the Co3+4+: t2g band overlaps with the top of the O2-:2p band. In contrast, Co offers good structural stability without migrating from the transition-metal layer to the lithium layer via the neighboring tetrahedral sites due to the high octahedral-site stabilization energy, while Mn migrates readily to the lithium layer resulting in a layered to spinel-like phase transition due to the low octahedral-site stabilization energy. Also, Mn is abundant, environmentally benign, and less conductive, while Co has limited abundance, is relatively toxic, and becomes metallic on charging. Ni is in between Co and Mn in all these criteria. To make use of the best out of each of these three ions, the industry is now based on LiNi1-y-zMnyCozO2 with (1-y-z) < 0.6 and a significant fraction of Co (z > 0.2). There is a significant drive to reduce the fraction of Co or eliminate it altogether and increase the fraction of Ni. However, LiMO2 cathodes with a high fraction of Ni suffer from a few serious issues: capacity fade, thermal instability, and air-reactivity due to (i) a series of phase transitions causing internal stress, (ii) high surface reactivity with the electrolyte resulting in the formation of thick solid-electrolyte interphase, and (iii) high surface reactivity with ambient air resulting in a significant amount of LiOH and LiHCO3 on the surface. This presentation will first focus on a fundamental understanding of the bulk and surface instability of layered LiMO2 cathodes, employing advanced characterization tools, such as time-of-flight secondary ion mass spectrometry, x-ray photoelectron spectroscopy, and aberration-corrected transmission electron microscopy, to probe both the layered oxide cathode and graphite anode subjected in full lithium-ion cells to extended cycling (up to 1,500 cycles). The presentation will then focus on developing LiMO2 cathodes with a cobalt content of as low as 6% with appropriate cationic doping and surface stabilization. Finally, it will also present a path forward to develop cobalt-free LiMO2 cathodes. Based on the strategies, cathodes with capacities of as high as 220 mAh/g with good cycle life and air stability will be presented.

CoS2 hollow nanocubes derived from Co-Co Prussian blue analogue: High-performance electrode materials for supercapacitors

In this paper, we demonstrate a two-step method to transform Co-Co Prussian blue analogue (PBA) nanocubes into porous and hollow CoS2 nanocubes. The morphology and microstructures of the synthesized CoS2 hollow nanocubes were investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, X-ray diffraction, and automatic micropore physisorption analyzer. Electrochemical capacitive properties of the synthesized CoS2 hollow nanocubes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests in alkaline aqueous solution (2M KOH). Results show that the porous CoS2 nanocubes have hollow and mesoporous structure with high specific surface area (113.9m2g−1), and show a high specific capacitance of 936Fg−1 at the current density of 1Ag−1. Also, the CoS2 hollow nanocubes possess good power characteristics (the capacitance retention is 73.3% from 1Ag−1 to 20Ag−1) and good long-term cycling life with 83% specific capacitance retention after 5000cycles at 5Ag−1. Additionally, an asymmetric supercapacitor (ACS) was assembled by using CoS2 on carbon cloth and activated carbon (AC) on carbon cloth as the positive and negative electrodes, respectively. The prepared ACS shows a high energy density of 34.68Whkg−1 at the power density of 356.9Wkg−1, 25.74Whkg−1 remained at a power density of 7336.8Wkg−1, and excellent rate performance (the capacitance retention is 74.2% from 0.5 to 10Ag−1). These indicate that the CoS2 hollow nanocubes are good candidates for the next-generation high performance supercapacitor electrode materials.