LiNi0.5Mn1.5O4 Research Articles

Analysis of Vinylene Carbonate (VC) as Additive in Graphite/LiNi0.5Mn1.5O4 Cells

Vinylene Carbonate (VC) is an effective electrolyte additive to produce a stable solid electrolyte interphase (SEI) on graphite anodes, increasing the capacity retention of lithium-ion cells. However, in combination with LiNi0.5Mn1.5O4 (LNMO) cathodes, VC drastically decreases cell performance. In this study we use on-line electrochemical mass spectrometry (OEMS) and electrochemical impedance spectroscopy (EIS) with a micro-reference electrode to understand the oxidative (in-)stability of VC and its effect on the interfacial resistances of both anode and cathode. We herein compare different VC concentrations corresponding to VC to graphite surface area ratios typically used in commercial-scale cells. At low VC concentrations (0.09 wt%, corresponding to 1 wt% in commercial-scale cells), an impedance increase exclusively on the anode and an improved capacity retention is observed, whereas higher VC concentrations (0.17 wt – 2 wt%, corresponding to 2 wt - 23 wt% in commercial-scale cells) show an increase in both cathode and anode impedance as well as worse cycling performance and overcharge capacity during the first cycle. By considering the onset potentials for VC reduction and oxidation in graphite/LNMO cells, we demonstrate that low amounts of VC can be reduced before VC oxidation occurs, which is sufficient to effectively passivate the graphite anode.

Power characteristics of spinel cathodes correlated with elastic softness and phase transformation for high-power lithium-ion batteries

We present the phase transformation kinetics associated with mechanical deformations and electrochemical properties of LiNi0.5Mn1.5O4 (LNMO) and LiNi0.5Mn1.5−xTixO4 (LNMTO) that elucidate the correlation between power characteristics, mechanical deformations, and phase transformations.

An Analysis Protocol for Three-Electrode Li-Ion Battery Impedance Spectra: Part I. Analysis of a High-Voltage Positive Electrode

A key for the interpretation of porous lithium ion battery electrode impedance spectra is a meaningful and physically motivated equivalent-circuit model. In this work we present a novel approach, utilizing a general transmission line equivalent-circuit model to exemplarily analyze the impedance of a porous high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode. It is based on a LNMO/graphite full-cell setup equipped with a gold wire micro-reference electrode (GWRE) to obtain impedance spectra in both, non-blocking conditions at a potential of 4.4 V cell voltage and in blocking configuration achieved at 4.9 V cell voltage. A simultaneous fitting of both spectra enables the deconvolution of physical effects to quantify over the course of 85 cycles at 40°C: a) the true charge transfer resistance (RCT), b) the pore resistance (RPore), and c) the contact resistance (RCont.). We demonstrate that the charge transfer resistance would be overestimated significantly, if the spectra are fitted with a conventionally used simplified R/Q equivalent-circuit compared to our full transmission line analysis.

The Effect of the Fluoroethylene Carbonate Additive in LiNi0.5Mn1.5O4 - Li4Ti5O12 Lithium-Ion Cells

The effect of the electrolyte additive fluoroethylene carbonate (FEC) for Li-ion batteries has been widely discussed in literature in recent years. Here, the additive is studied for the high-voltage cathode LiNi0.5Mn1.5O4 (LNMO) coupled to Li4Ti5O12 (LTO) to specifically study its effect on the cathode side. Electrochemical performance of full cells prepared by using a standard electrolyte (LP40) with different concentrations of FEC (0, 1 and 5 wt%) were compared and the surface of cycled positive electrodes were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results show that addition of FEC is generally of limited use for this battery system. Addition of 5 wt% FEC results in relatively poor cycling performance, while the cells with 1 wt% FEC showed similar behavior compared to reference cells prepared without FEC. SEM and XPS analysis did not indicate the formation of thick surface layers on the LNMO cathode, however, an increase in layer thickness with increased FEC content in the electrolyte could be observed. XPS analysis on LTO electrodes showed that the electrode interactions between positive and negative electrodes occurred as Mn and Ni were detected on the surface of LTO already after 1 cycle.

Electrochemical Cross-Talk Leading to Gas Evolution and Capacity Fade in LiNi0.5Mn1.5O4/Graphite Full-Cells

Continuous destruction of the solid electrolyte interphase (SEI) on the graphite-based negative electrode during cycling operation is a significant degradation mechanism that raises safety concerns and limits the cycle life of LiNi0.5Mn1.5O4 (LNMO)/graphite full-cells. Herein, we report on gassing phenomena which are typically concomitant with SEI destruction processes. Abrupt H2 evolution is observed by differential electrochemical mass spectrometry and pressure measurements at the end of discharge. Using a lithium reference electrode reveals that the gassing, which intensifies with cycling, is caused by an increase in the anode potential. Lithium is irreversibly consumed upon SEI formation, but this loss is not compensated for by the intrinsic degradation of LNMO in the first cycle. When the potential of the anode on discharge increases above approximately 0.9 V, the SEI is instantly damaged, causing gas generation, and eventually capacity fade. We show that this (“mediator-free”) cross-talk phenomenon ...

Graphite//LiNi0.5 Mn1.5 O4 Cells Based on Environmentally Friendly Made-in-Water Electrodes.

The performance of graphite//LiNi0.5 Mn1.5 O4 (LNMO) cells, both electrodes of which are made using water-soluble sodium carboxymethyl cellulose (CMC) binder, is reported for the first time. The full cell performed outstandingly over 400 cycles in the conventional electrolyte ethylene carbonate/dimethyl carbonate-1 m LiPF6 , and the delivered specific energy at the 100th, 200th, 300th, and 400th cycle corresponded to 82, 78, 73, and 66 %, respectively, of the initial energy value of 259 Wh kg-1 (referring to the sum of the two electrode-composite weights). The good stability of high-voltage, LNMO-CMC-based electrodes upon long-term cycling is discussed and the results are compared to those of LNMO-composite electrodes with polyvinylidene fluoride (PVdF). LNMO-CMC electrodes outperformed those with PVdF binder, displaying a capacity retention of 83 % compared to 62 % for the PVdF-based electrodes after 400 cycles at 1 C. CMC promotes a more compact and stable electrode surface than PVdF; undesired interfacial reactions at high operating voltages are mitigated, and the thickness of the passivation layer on the LNMO surface is reduced, thereby enhancing its cycling stability.

Amorphous Lithium Lanthanum Titanate for Solid-State Microbatteries

Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10−4 S/cm and electronic conductivity to 5 × 10−11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gas is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi0.5Mn1.5O4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. These results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

Binders are electrochemically inactive electrode components. However, their chemical and physical nature greatly affects battery performance and plays a key role in electrode integrity and interface reactivity. The binders thus have a strong impact on battery capacity retention and cycle life. Water-processable binders would make the electrode preparation process cheap and environmentally friendly and provide a viable alternative to polyvinylidene difluoride (PVdF). Here we report the use of sodium alginate (SA) as binder for LiNi0.5Mn1.5O4 (LNMO), one of the most promising cathode materials for high-voltage and high-energy LIBs. We demonstrate that electrodes with high mass loading containing SA have excellent specific discharge capacity (120 mAh g−1 at C/3 and 100 mAh g−1 at 5C) with negligible overpotentials in conventional electrolyte based on ethylene carbonate (EC): dimethyl carbonate (DMC) and 1 M LiPF6, where the reactivity of LNMO is known to negatively affect stability. The electrodes with SA also show a good stability over subsequent cycles of charge and discharge at 1C with capacity retention of 95% and 86% with respect to the initial cycles at the 100th and 200th cycle.

Rapid hydrothermal and post-calcination synthesis of well-shaped LiNi0.5Mn1.5O4 cathode materials for lithium ion batteries

High voltage spinel LiNi0.5Mn1.5O4 (LNMO) cathode materials with well-developed polyhedral-shape structure have been successfully synthesized via a rapid hydrothermal process followed by high-temperature calcination with Li source. The as-synthesized samples were characterized by powder X-ray diffraction, Raman spectroscopy, Scanning electron microscopy and electrochemical test. All samples show polyhedral-shape morphologies as well as cubic spinel structure with Fd3m space group. Electrochemical analysis verifies that the spinel LNMO cathode prepared with sulfate at hydrothermal temperature of 200 °C exhibits the better electrochemical properties in terms of discharge capacity, cycling stability and rate performance. This sample delivers an initial discharge capacity of 131.1 mAh g−1 at 0.5 C rate at 25 °C, with the capacity retention of 85.2% after 100 charge-discharge cycles. Additionally, it still shows high rate performance with a discharge capacity of 110.9 mAh g−1 even at 20 C rate. The excellent electrochemical properties are mainly attributed to its high crystallinity, appropriate particle size and uniform particle size distribution. These results suggest that the rapid hydrothermal and post-calcination method is an effective way for preparing high voltage LNMO cathode materials which can be applied to lithium ion batteries.

Suppression of Aluminum Current Collector Dissolution by Protective Ceramic Coatings for Better High-Voltage Battery Performance.

Batteries based on cathode materials that operate at high cathode potentials, such as LiNi0.5 Mn1.5 O4 (LNMO), in lithium-ion batteries or graphitic carbons in dual-ion batteries suffer from anodic dissolution of the aluminum (Al) current collector in organic solvent-based electrolytes based on imide salts, such as lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). In this work, we developed a protective surface modification for the Al current collector by applying ceramic coatings of chromium nitride (Crx N) and studied the anodic Al dissolution behavior. By magnetron sputter deposition, two different coating types, which differ in their composition according to the CrN and Cr2 N phases, were prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and their electronic conductivity. Furthermore, the anodic dissolution behavior was studied by cyclic voltammetry and chronocoulometry measurements in two different electrolyte mixtures, that is, LiTFSI in ethyl methyl sulfone and LiTFSI in ethylene carbonate/dimethyl carbonate 1:1 (by weight). These measurements showed a remarkably reduced current density or cumulative charge during the charge process, indicating an improved anodic stability of the protected Al current collector. The coating surfaces after electrochemical treatment were characterized by means of SEM and XPS, and the presence or lack of pit formation, as well as electrolyte degradation products could be well correlated to the electrochemical results.

Designed seamless outer surface: Application for high voltage LiNi0.5Mn1.5O4 cathode with excellent cycling stability

Suppressing side reactions at the cathode-electrolyte interface (CEI) is critical for alleviating capacity fading of the high-voltage (>5 V) spinel cathode material LiNi0.5Mn1.5O4 (LNMO). The primary bottleneck in conventional nanoengineering of LNMO involves an antagonistic relationship between the positive effects of the nanometer particle size and negative effects stemming from the larger CEI area. Inspired by Buckminster Fuller's geodesic domes, we have designed a seamless LNMO hollow sphere (S-LNMO) that comprises average 120 nm-sized triangles and truncated triangle subunits by means of grain growth orientation. The “tensegrity” structure has efficiently hindered the interfacial side reaction, which occurs only within a depth of 5 nm from the surface, thereby improving its electrochemical stability. The embedded layered Li2TiO3 (LTO) in bulk S-LNMO (LTO:S-LNMO) region further improved the high-rate performance, demonstrating an ∼110 mAh/g capacity with 80.9% retention after 400 cycles at 5 C and remaining stable after 900 cycles at 5 C even after being stored at 50 °C for one week.

LiNi0.5Mn1.5O4 hollow nano-micro hierarchical microspheres as advanced cathode for lithium ion batteries

The high-voltage spinel-type LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material for next-generation lithium ion batteries. In this study, hollow LNMO microspheres have been synthesized via co-precipitation method accompanied with high-temperature calcinations. The physical and electrochemical properties of the materials are characterized by x-ray diffraction (XRD), TGA, RAMAN, CV, scanning electron microscope (SEM), transmission electon microscopy (TEM), electrochemical impendence spectroscopy (EIS), and charge-discharge tests. The results prove that the microspheres combine hollow structures inward and own a cubic spinel structure with space group of Fd-3m, high crystallinity, and excellent electrochemical performances. With the short Li+ diffusion length and hollow structure, the hierarchical LNMO microspheres exhibit 138.2 and 108.5 mAh g−1 at 0.5 and 10 C, respectively. Excellent cycle stability is also demonstrated with more than 98.8 and 88.2 % capacity retention after 100 cycles at 1 and 10 C, respectively.

High Voltage LiNi0.5Mn1.5O4/Li4Ti5O12 Lithium Ion Cells at Elevated Temperatures: Carbonate- versus Ionic Liquid-Based Electrolytes.

Thanks to its high operating voltage, the LiNi0.5Mn1.5O4 (LNMO) spinel represents a promising next-generation cathode material candidate for Lithium ion batteries. However, LNMO-based full-cells with organic carbonate solvent electrolytes suffer from severe capacity fading issues, associated with electrolyte decomposition and concurrent degradative reactions at the electrode/electrolyte interface, especially at elevated temperatures. As promising alternatives, two selected LiTFSI/pyrrolidinium bis(trifluoromethane-sulfonyl)imide room temperature ionic liquid (RTIL) based electrolytes with inherent thermal stability were investigated in this work. Linear sweep voltammetry (LSV) profiles of the investigated LiTFSI/RTIL electrolytes display much higher oxidative stability compared to the state-of-the-art LiPF6/organic carbonate based electrolyte at elevated temperatures. Cycling performance of the LNMO/Li4Ti5O12 (LTO) full-cells with LiTFSI/RTIL electrolytes reveals remarkable improvements with respect to capacity retention and Coulombic efficiency. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns indicate maintained pristine morphology and structure of LNMO particles after 50 cycles at 0.5C. The investigated LiTFSI/RTIL based electrolytes outperform the LiPF6/organic carbonate-based electrolyte in terms of cycling performance in LNMO/LTO full-cells at elevated temperatures.

Density functional theory analysis of surface structures of spinel LiNi0.5Mn1.5O4 cathode materials

First-principle calculation was employed to investigate the surface stability for (100), (110), and (111) low-index facets of LiNi0.5Mn1.5O4 (LNMO) crystallographic structures with a P4332 space group and phase transitions at the surface regions of Ni0.5Mn1.5O4. The calculated surface energies of (100) and (111) facets with Li-terminations are 1.39 and 1.40 eV, respectively, indicating that both these facets of the LNMO are stable according to the calculation results. Defect formation energies and diffusion barriers of Ni and Mn in surface facets of the Ni0.5Mn1.5O4 are much lower than those in the bulk. This suggests that the Ni and Mn ions in the surface regions of the LNMO easily occupy the tetrahedral Li-positions during delithiation process, which supports the experimental results and explains the surface structure changes of the LNMO upon delithiation.

Electrochemical Performance of Spinel-Type LiNi0.5Mn1.5O4 Thin-Film in Aqueous Electrolytes

Introduction Due to the increase of the demand for use of sustainable energy, lithium-ion batteries attract more attention as one of the leading candidates of application in large-scale energy facilities. While the safety of lithium-ion batteries are gradually improved, the flammable organic solvents used in the electrolytes have fatal drawbacks. In addition, the cost of preparing and handling ultra-dry organic solvents is also a serious concern, and therefore alternative electrolytes have been studied. Aqueous electrolytes could resolve these concerns, but their narrow electrochemical window (1.23 V) raises another problem. The electrodes reactions in aqueous electrolytes are accompanied by the decomposition of H2O on the surface of electrodes. Therefore the voltages of aqueous lithium-ion batteries are limited (less than 1.5 V), and it diminishes the advantages that plentiful active materials can be used for lithium-ion batteries [1]. Considerable effort has been made to overcome the limitation of the electrochemical window. The most common method is the modification of the electrode surface. The coated electrodes retard the access of water molecules [2]. Another method to obtain aqueous electrolytes with wide electrochemical windows is to increase the concentration of salts in aqueous electrolyte since the activity of water can be decreased. In this work, we enhanced the resistance to oxidative decomposition of aqueous electrolytes by adding organosulfate to aqueous electrolytes and show the electrochemical properties of spinel-type LiNi0.5Mn1.5O4(LNMO) electrode in the electrolytes. Experimental The electrochemical potential windows of aqueous electrolytes were measured by using a rotating-disk electrode (RDE) of Pt with a rotation speed of 400 rpm. Linear sweep voltammetry was carried out in aqueous electrolytes of 0.5 M LiNO3 and 0.25 M Li-PO4 buffer with saturated PDSS. Buffer solution consisted of LiOH and H3PO4with a molar rate of 3:2 (pH 7). LNMO thin-films were prepared by sol-gel method. Prepared LNMO thin-films were characterized by X-ray diffraction (XRD) measurement.A three-electrode cell was used for electrochemical measurements. LNMO thin-film was used as a working electrode and Pt mesh as a counter electrode and Ag/AgCl electrode was used as a reference electrode. Cyclic voltammetry was carried out between 0.6 and 1.6 V at a scan rate of 1.0 mV s−1. Results and discussion XRD patterns of synthesized LiNi­0.5Mn1.5O4 thin-films had good agreements with ICDD diffraction patterns of spinel-type LNMO. Fig. 1 shows linear sweep voltammograms of Pt disk electrode. While the oxidation current was observed at 1.0 V (vs. Ag/AgCl) in the electrolyte of 0.5 M LiNO3, the onset potential of water oxidation shifted positively to 1.6 V (vs. Ag/AgCl) in the PDSS buffer solution [3]. The electrochemical behaviors of the LNMO thin films in 0.25 M Li-PO4 buffer with saturated PDSS are shown in Fig. 2. When we conducted cyclic voltammetry in solutions of 0.5 M LiNO3, oxidation currents began to increase at a potential of 1.3 V (vs. Ag/AgCl), but there were no clear redox pairs that corresponded to Li+ insertion/extraction of LNMO. On the other hand, in the PDSS buffer solution the oxidation current for oxygen evolution was suppressed, and two redox pairs appeared at around 1.5 V (vs. Ag/AgCl) which appeared to Li+ insertion/extraction of LNMO. This implies that the Li+insertion/extraction at LNMO thin film occurred even in aqueous solution by suppressing oxygen evolution and relieving the decrease in local pH corresponding oxidation of water. Reference W. Li et al., Science, 264, 1115-1118 (1994).I. B. Stojkovic et al., Electrochem. Commun., 12, 371-373 (2010).K. Miyazaki et al., Chem. Commun., 52, 4979-4982 (2016). Figure 1

Very-Low Solid-Electrolyte/Electrode Interface Resistance in Li(Ni0.5Mn1.5)O4-Based Thin-Film Lithium Battery

All-solid-state lithium batteries with improved safety and larger capacity have been anticipated as a next-generation rechargeable battery. In particular, 5 V-class cathode material, LiNi0.5Mn1.5O4 (LNMO), has received considerable attention for the expected high power density. In all-solid-state LBs using LNMO, however, high interface resistance between an electrode and electrolyte hinders high power density. Thus, the reduction of the interface resistance and the investigation of the origins are of important issues. Recent progress in thin-film deposition techniques of electrodes and electrolytes has made it possible to fabricate all-solid-state thin film batteries with atomically controlled interfaces, and quantitative studies of the interface resistance values have been reported. In this study, we fabricated all-solid-state thin-film lithium batteries using LNMO epitaxial thin films and Li3PO4 solid electrolyte, and demonstrated a very low Li3PO4/LNMO interface resistance. Figure 1 shows a structure of all-solid-state thin films battery (inset), and its charge and discharge curves. The fabricated thin film batteries consisted of an epitaxial cathode LNMO(100) film, an amorphous solid-electrolyte Li3PO4 film, a metallic anode Li film, a current collector LaNiO3(100) film, and Nb-doped SrTiO3(100) substrate. To ensure a clean Li3PO4/LNMO interface in the thin films batteries, the ultrahigh vacuum chambers used for the film depositions and characterizations were all directly connected each other. The LNMO thin-film battery exhibits good battery performance. The charge and discharge curves show redox reactions of LNMO (Ni2+/Ni4+ and Mn3+/Mn4+), and the capacity did not degrade even up to the 100th cycle. We also evaluated the interface resistance using impedance spectroscopy, and found a very low interface resistance of ~5 Ωcm2. A Nyquist plot (Fig. 2) displays one semicircle at a higher frequency region (104~106 Hz), originating from the resistance of Li3PO4 (5×10-7 S/cm). In addition, a smaller semicircle at a lower frequency region (102~104 Hz) is attributed to the interface resistance at the Li3PO4/LNMO interface. The very low interface resistance of ~5 Ωcm2 is one order of magnitude smaller than those reported before, and implies that space charge layer formed at the Li3PO4/LNMO interface hardly results in high interface resistance. This study was supported by NEDO, JST-ALCA, JST-CREST, and Kakenhi. The authors also acknowledge the support of Toyota Motor Corporation. [1] S. Shiraki, H. Oki, Y. Takagi, T. Suzuki, A. Kumatani, R. Shimizu, M. Haruta, T. Ohsawa, Y. Sato, Y. Ikuhara, T. Hitosugi, J. Power Sources 267 (2014) 881-887. [2] M. Haruta, S. Shiraki, T. Suzuki, A. Kumatani, T. Ohsawa, Y. Takagi, R. Shimizu, and T. Hitosugi, Nano Lett. 15 (2015) 1498-1502. Figure 1

Influence of Ni/Mn Ordering and Oxygen Deficiency on Structure, Magnetic and Electrochemical Properties of LiNi0.5Mn1.5O4

LiNi0.5Mn1.5O4 (LNMO) is known as a 5 V class of cathode material for lithium-ion secondary batteries. LNMO adopts the spinel structure with two different space groups (Fd3-m and P4332) depending on the arrangement of Ni and Mn cations, and the difference of Ni/Mn arrangement influences their electrochemical properties. The Ni/Mn disordered phase exhibits a small step at 4.0 V attributable to Mn3+/4+ redox couple and two distinguishable plateaus around 4.7 V attributable to Ni2+/3+ and Ni3+/4+ redox couples in charge/discharge curves. Conversely, Ni/Mn ordered phase shows a single plateau around 4.7 V attributed to Ni2+/4+ redox couple and the low voltage plateau around 4.0 V is hardly observed. However, disordered phase (Fd3-m) has oxygen deficiencies and contains an impurity phase. Thus, the predominant factors of their electrochemical properties are not clear. Moreover, there are a few reports on magnetic properties of this system, in which the samples included an impurity of a rock salt phase. In this study, we synthesized Ni/Mn disordered phase of LNMO without oxygen deficiency and investigated the magnetic properties and the electrochemical properties. LNMO sample was synthesized from precursor of Ni and Mn oxalate prepared by coprecipitation method to obtain single-phase LNMO at low temperature. Mn/Ni ratio of the obtained precursor was confirmed to be the target composition by ICP analysis. Synthesis conditions of LNMO samples are summarized in Table 1. LNMO samples were characterized by powder X-ray diffraction measurements, Raman spectroscopy, iodometry, magnetic measurements and charge/discharge measurements. Powder X-ray diffraction measurements indicated that sample B, C and D were single-phase, while sample A slightly contained the rock salt phase. Raman spectroscopy revealed that Ni/Mn arrangement in sample A and B is disordered and that in sample C and D is ordered, indicating that annealing at 600 ˚C is necessary to obtain Ni/Mn ordered phases. Iodometry indicated that only sample A has the oxygen deficiencies. Conversely, sample B does not have oxygen deficiencies, thus we succeeded in synthesis of Ni/Mn disordered phase of LNMO without oxygen deficiency. The lattice constant of sample A is greater than other samples due to reduction from Mn4+ to Mn3+ with introducing the oxygen deficiencies. The saturated magnetization of sample A is lower than those of other samples due to the antiferromagnetic superexchange interaction between Mn4+ and Mn3+ via oxygen. The saturated magnetization is also influenced by Ni/Mn ordering. Moreover, Sample A and B exhibited different electrochemical properties. The sample A showed a small step at 4.1 V attributable to Mn3+/4+ redox couple, while sample B did not show any steps around 4.1 V. The discharge capacity of sample B decreases largely compared to sample A. We will discuss the influences of Ni/Mn ordering and oxygen deficiencies on structure, and magnetic and electrochemical properties of LNMO. Figure 1

Enhanced Electrochemical Performance of Porous Electrodes for All-Solid-State Li-Ion Microbatteries

Nowadays, lithium-ion batteries (LIBs) are widely used to power portable devices, microelectronics, vehicles, etc. With many advantages such as high surface area and improved charge transport, self-supported 3-D nanostructured metal oxides are promising electrode materials for LIBs and their impact is particularly significant when considering the miniaturization of energy storage systems and the development of 3D microbatteries [1-3]. During this talk, it will be presented the fabrication and use of porous electrodes based on titania nanotubes (TiO2nts) as anode [4–8] and LiNi0.5Mn1.5O4 (LNMO) as cathode. This kind of 3D nanostructured electrodes is particularly interesting due to better electrochemical performance in terms of kinetics and stability during cycling. Then, the fabrication of an all-solid-state Rocking-chair battery composed of vertical arrays of TiO2nts as anode, a polymer thin film as electrolyte, and a LiNi0.5Mn1.5O4 (LNMO) layer as cathode will be shown [9]. According to the electrochemical tests, this 2D full-solid microbattery exhibits high performance such as good discharge capacity and good capacity retention. Finally, the current approaches developed to achieve the fabrication of a full 3D microcell will be highlighted. Particularly, the conformal electrodeposition of polymer electrolytes onto the electrodes will be discussed [10-12].

Thin Film Processing of Amorphous Lithium Lanthanum Titanate Based Solid-State Microbatteries

Next generation batteries will require a broad range of energies to meet the challenges of portable electronic storage from electric vehicles to microelectromechanical systems (MEMS). Solid state electrolytes are researched heavily because they have the potential to improve capacity loss, cycle lifetime, operation temperature, and safety [1]. Lithium lanthanum titanate (LLTO), with the perovskite structure (ABO3), has gained interest due to its high bulk conductivity (10-3 S cm-1) at room temperature [2]. LLTO has many advantages including negligible electronic conductivity, high voltage stability (> 8 V), atmospheric stability, and temperature stability [3]. Furthermore, LLTO is transferable to thin film structures for fabricating microbatteries for powering portable electronics on-chip [4]. However, crystalline LLTO has a relatively low grain boundary conductivity (<10-5 S cm-1), lowering the overall material conductivity [3]. Therefore, in this work, we investigate amorphous LLTO thin films grown by pulsed laser deposition (PLD). By controlling the laser fluence, background pressure, and temperature we are able to grow dense films with an ionic conductivity of 8x10-4 S/cm and electronic conductivity of 5x10-11 S/cm. Secondly, we explore LiNi0.5Mn1.5O4 (LNMO) spinel thin films deposited via PLD as a potential high voltage cathode for our battery. We report on LNMO/LLTO half cells and novel full LLTO based thin film microbatteries. [1] A. Hayashi et. al.“ Superionic glass-ceramic electrolytes for room-temperature rechargeable sodium batteries,” Nature Communications. 3 (2012) 856–860. [2] O. Bohnke. “The fast lithium-ion conducting oxides Li3xLa2/3 − xTiO3from fundamentals to application,” Solid State Ionics. 179 (2008) 9-15. [3] C. Cao et. al.“Recent advances in inorganic solid electrolytes for lithium batteries,” Frontiers in Energy Research. 2 (2014) 1-10. [4] A. Furusawa et. al. “Ionic conductivity of amorphous lithium lanthanum titanate thin film,” Solid State Ionics. 176 (2005) 553-558.

Synthesis and characterization of nanocomposites based on poly(3-hexylthiophene)-graft-carbon nanotubes with LiNi0.5Mn1.5O4 and its application as potential cathode materials for lithium-ion batteries

The P3HT grafted on CNTs to form the P3HT-g-CNTs nanocomposites was synthesized and their morphologies, structure have been characterized via the sedimentation test, scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the P3HT- g-CNTs has a better thermal stability than that of the P3HT/CNTs blend. The nanocomposite based on P3HT- g-CNTs and doped spinel LiNi0.5Mn1.5O4 (LNMO) have been fabricated via mixing process. The structure and morphologies of LNMO/P3HT- g-CNTs nanocomposites have also been performed by SEM, XRD and TEM. The electrochemical performance of LNMO/P3HT- g-CNTs nanocomposites as cathode materials of lithium-ion batteries were investigated by cyclic voltammetry and electrochemical impedance spectroscopy and exhibited the high diffusion of lithium ions in the charge–discharge process.