Lithium Precursor Research Articles

Lithium Hydroxide Based Performance Improvements for Nickel Rich Ncm Layered Cathode Material

The increased adoption of electric vehicle technologies is driving the demand for higher energy density batteries. Since the lithium ion battery was first commercialized 25 years ago in 1991, significant improvements have been achieved through both battery design and materials innovations. However, even as these past achievements are celebrated, current research and industry targets are focused on higher energy and lower cost batteries. It is necessary to consider advanced materials on both the cathode and anode sides of the battery to achieve these goals. Commercially available electric vehicles have achieved driving ranges in excess of 200 miles (320 km) per charge (1). This has been made possible in part through the use of high nickel cathode materials. Nickel-rich layered cathode materials such as LiNi0.8Co0.15Al0.05O2 (NCA) and nickel-rich LiNi1-2xCoxMnxO2 (NCM) can deliver high specific capacities of over 200 mAh g-1. However, the challenges surrounding synthesis of these materials are well documented (2), (3), (4). It is established that synthesis of NCA requires use of lithium hydroxide as the lithium precursor. Additional research efforts have been focused on nickel-rich NCM materials (Ni ≥ 0.6 moles) in an effort to balance high specific capacity with battery safety. The choice of lithium precursor, LiOH.H2O or Li2CO3, can have a dramatic effect on the performance of these materials. Here we report the advantages of using lithium hydroxide on the performance of nickel-rich cathode materials. Superior physical properties, such as higher tap and packing density, can be achieved at lower synthesis temperatures for nickel-rich NCM materials when using lithium hydroxide as the lithium precursor. We will show that using lithium hydroxide allows for improved material crystallinity as observed by x-ray diffraction and that Rietveld refinement shows greater structural purity and less mixing of Li+ and Ni2+ in the lithium layer for lithium hydroxide versus lithium carbonate. X-ray diffraction results have shown that lithium is incorporated in the structure of the NCM when using lithium hydroxide, while use of lithium carbonate results in excess free lithium (unreacted lithium that could be present as Li2O, LiOH or Li2CO3 depending on handling of the cathode material post synthesis) leading to an increase in material pH that can cause jelling of the cathode slurry and swelling of the cell upon cycling. Furthermore, as x decreases in LiNi1-2xCoxMnxO2 the lithium hydroxide advantage becomes more apparent. We will also show electrochemical performance improvements at optimized synthesis conditions. References Straubel, J. B. "Driving Range for the Model S Family." Tesla Motors, 30 Dec. 2014. www.tesla.com. B. H. Kim, et al., The effect of oxygen pressure on the synthesis of LiNiO2. Solid State Phenomena, Vols. 124-126, (2007), p. 1043-1046 P. Kalyani, N. Kalaiselvi, Various aspects of LiNiO2 chemistry: A Review. Science and Technology of Advanced Materials, 6, (2005), p. 689–703 Kim, M.-H., Shin, H.-S., Shin, D. & Sun, Y.-K., Synthesis and electrochemical properties of Li[Ni0.8Co0.1Mn0.1]O2 and Li[Ni0.8Co0.2]O2 via co-precipitation. Journal of Power Sources, (2006), 159, p. 1328-1333 Figure 1

Plasma-Assisted Atomic Layer Deposition of Thin Film Li2CO3 for All-Solid-State Li-Ion Batteries

All-solid-state Li-ion batteries offer the advantage of a higher power density, a wider temperature window and an improved safety with respect to batteries containing liquid electrolytes. However, the lack of solid electrolytes with sufficient ion conductivity and wide electrochemical window is currently inhibiting the implementation of solid state batteries. Although the limited ionic conductivity can be overcome by employing very thin solid-state electrolyte films which shorten the ionic diffusion distance, the capacity will still be insufficient. This makes the use of non-planar devices of particular high interest as the application of 3D-(nano)structured materials will increase the total effective battery area. Moreover, the area enhancement will result in an ever higher energy density, faster (dis)charging, better stability, etc. Conventional deposition techniques, such as PVD and PE-CVD, do not generally result in conformal thin layers on 3D structures. Therefore, novel deposition techniques leading to enhanced control in thin film properties and conformality are being introduced in the field of battery research. Atomic layer deposition (ALD), which is based on sequential and self-limiting reactions, has emerged as a powerful tool since it offers exceptional conformality on high-aspect ratio structures, thickness control at sub-nm level, and tunable film properties. In this work, thin film lithium carbonate (Li₂CO₃) is being deposited by ALD. Li₂CO₃ is widely used as a building block for the fabrication of Li-ion battery active materials, such as lithium cobalt oxide (LiCoO₂), which is used for most lithium-ion battery cathodes [1]. It has also been reported that Li₂CO₃, without combining it with other materials, has a pure ion conductive behavior and a good electrochemical stability [2]. The high electrochemical stability of Li₂CO₃ makes it useful as an artificial solid-electrolyte interface (SEI) or buffer layer [3]. The SEI and buffer layer need to be conformal and very thin, for which the use of ALD would be beneficial. In addition, ultra-thin Li₂CO₃ can also improve the stability of known solid electrolyte layers, such as lithium lanthanum titanate or lithium phosphate. More specifically, we focus on the optimization of the plasma-assisted Li₂CO₃ ALD process by (in situ) growth studies and we investigate the influence of the process parameters on the electrical and electrochemical properties. Using plasmas in combination with ALD opens up the possibility to tune the properties of the layer by varying the plasma exposure time and also to deposit at lower temperatures. Although the plasma-assisted ALD process for Li₂CO₃ has been reported in literature before [4], to our knowledge, the optimization of the process was not reported, and also an electrochemical analysis of Li₂CO₃ layers fabricated with this method is still lacking. The ALD process employed, consists of a combination of LiOtBu as lithium precursor and an O₂ plasma as oxidant source, alternated by Ar purges. A growth rate of ± 0.8 Å/cycle was obtained at a process table temperature of 150 °C on TiN substrates in the linear growth regime (figure). TiN substrates are used as an electrical contact for electrical and electrochemical testing of the layers. The film stoichiometry was investigated with Elastic Recoil Detection (ERD) and X-ray Photoelectron Spectroscopy (XPS). The results are in good agreement with the stoichiometry and density of Li₂CO₃. Excellent electronic insulation properties were confirmed by current-voltage and DC-polarization measurements. This observation is in agreement with impedance measurements at open circuit potential (figure), which showed no apparent electronic conductivity of the film. The dependence of ALD process parameters such as temperature and O₂ plasma exposure time on the electrochemical properties is investigated. Moreover, half cells employing Li₂CO₃ with TiO₂, LiMn₂O₄ and Si electrodes were studied for cyclability and rate performance. These and other results will be presented in this contribution. Acknowledgements: This project is financially supported by the Dutch program “A green Deal in Energy Materials” ADEM Innovation Lab. M. E. Donders et al., Journal of The Electrochemical Society, 160 (5), 2013J. Mizusaki et al., Solid State Ionics, 53-56, 1992P. Verma et al., Electrochimica Acta, 55, 2010A. C. Kozen et al., The Journal of Physical Chemistry C, 118, 2014 Figure caption: On the left: growth curve for the plasma-assited ALD process of Li₂CO₃ measured by in-situ spectroscopic ellipsometry on TiN at 150 °C and the corresponding process steps (insert). On the right: Electrochemical impedance spectroscopy measured at room temperature showing the presence of ionic conductivity. Figure 1

Li-Rich Layered Oxides As Concentration-Gradients for High Energy Density Lithium-Ion Batteries

The Li and Mn-rich layered oxides are currently attracting a strong interest from the scientific community, as being one of the most attractive class of positive electrode materials for Lithium-ion batteries. Indeed, the Li and Mn-rich layered oxides Li1+xM1-xO2 (M = Mn, Co, Ni) exhibit very high reversible capacity at an affordable cost [1-3]. A common feature for all the Li and Mn-rich layered oxides is their long voltage “plateau” (i.e. high capacity), observed only at the end of the first charge. This behavior has been explained by the reversible participation of oxygen anions in the redox processes [4-7]. This reaction is reversible within the bulk, occurring without any major structural modifications, while at the material surface oxidized oxygen ions are destabilized and lost, causing transition metal migration and thus structural reorganization [4-5, 8-9]. While it is clear that the largest advantage of the Li-rich layered oxides lies in their outstanding capacities, they suffer from a continuous voltage decay upon cycling, which is the main handicap to their practical implementation [10-11]. It is induced by irreversible structural modifications occurring at the outer part of the particles (that determines the potential measured) and inducing densification of the metal-oxygen framework. One of the tracks we are following to modify the surface chemistry of the Li and Mn-rich layered oxides, and to stabilize reversible anion participation to the redox processes is the achievement of concentration gradients within the particles (aggregates). The goal is to promote the formation of the Li and Mn-rich layered oxides in the bulk and, moving to the surface, to enrich the layered oxides composition with Ni and Co: the target is to combine high energy density and chemical stability as it was reported for Ni-rich layered oxides [12]. The synthesis of carbonate precursors Mn0.52Ni0.29Co0.19CO3 showing a concentration gradient is achieved via a coprecipitation method and requests to adjust several synthesis parameters including the temperature, the pH, the feeding rate and the stirring speed. As shown in Figure 1, a thermal treatment is then performed with optimized Li/M ratios, lithium carbonate being the lithium precursor, and at different temperatures in order to promote lithium diffusion within the particles but also to maintain the concentration gradient after calcination. The average composition of the final lithiated oxide is Li1.1Mn0.47Ni0.26Co0.17O2. In-depth characterization of the composition and structure, from the surface to the core, was achieved combining X-ray diffraction, elemental chemical analyses by ICP, and different techniques of microscopy (EPMA, EDS and FIB-STEM). Electrochemical performances and the thermal stability in the charged state of the battery will be also discussed for this series of materials. Acknowledgements: Région Aquitaine is acknowledged for the financial support of this project. The microscopy analyses were performed with the technical and scientific support of M. Lahaye and P. Garreta at PLACAMAT (Bordeaux), and of A. Montani at MINATEC (Grenoble).

Lithium-silicate sol\u2013gel bioactive glass and the effect of lithium precursor on structure\u2013property relationships

This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li_2O by the sol–gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol–gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, ^{29}Si and ^7Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation.Graphical

Preparation of Novel Li4 SiO4 Sorbents with Superior Performance at Low CO2 Concentration.

This work produced Li4 SiO4 sorbents through an impregnated-suspension method to overcome its typical poor performance at low CO2 concentrations. A SiO2 colloidal solution and two different organic lithium precursors were selected. A bulgy surface morphology (and thus, the significantly enlarged reacting surface area) was obtained for Li4 SiO4 , which contributed to the high absorption capacity. As a result, the capacity in cyclic tests at 15 vol % CO2 was approximately 8 times higher than conventional Li4 SiO4 prepared through a solid-state reaction. The phenomenon of a progressively increasing capacity (i.e., sustainable usage) was observed over the 40 cycles investigated, and this increasing trend continued to the last cycle. Correspondingly, over the course of the multicycle absorption/ desorption processes, the sorbents evolve from lacking porosity to having a high number of micron-sized pores.

Technologies and Materials to Enable Advanced Anode and Cathode Materials

The increased adoption of electric vehicle technologies is driving the demand for higher energy density batteries. Since the lithium ion battery was first commercialized 25 years ago in 1991, significant improvements have been achieved through both battery design and material innovations. However, even as these past achievements are celebrated, current research and industry targets are focused on higher energy and lower cost batteries. It is necessary to consider advanced materials on both the cathode and anode sides of the battery to achieve these goals. Commercially available electric vehicles have achieved driving ranges in excess of 200 miles (320 km) per charge (1). This has been made possible in part through the use of high nickel cathode materials. Nickel-rich layered cathode materials such as LiNi0.8Co0.15Al0.05O2 (NCA) and nickel-rich LiNixCo(1-x)/2Mn(1-x)/2O2 (NCM) can deliver high specific capacities of over 200 mAh g-1. However, the issues surrounding synthesis of these materials are well documented (2), (3), (4). It is established that synthesis of NCA requires use of lithium hydroxide as the lithium precursor. Additional research efforts have been focused on nickel-rich NCM materials (Ni ≥ 0.6 moles) in an effort to balance high specific capacity with battery safety. The choice of lithium precursor, LiOH.H2O or Li2CO3, can have a dramatic effect on the performance of these materials. We will discuss the advantages of using lithium hydroxide on the performance of nickel-rich cathode materials. On the anode side, silicon-based materials offer the potential for very high energy density (5). However, fundamental properties of silicon materials are hindering their commercialization (6). Extensive efforts are being undertaken to overcome issues such as loss of electrical contact and conductivity caused by material disintegration due to volume expansion and contraction during cycling, and a lot of progress has been reported (7). Nevertheless, it is generally accepted that successful commercialization of silicon-based anode materials will require pre-lithiation to overcome the issue of inherent large first cycle irreversible capacity loss. FMC’s innovative technology and material, Lectro® Max Powder (SLMP®), enables a new high energy density generation of lithium ion batteries by providing an independent source for lithium (8), (9) . Significant research has been directed toward developing stable, deployable SLMP pre-lithiation systems and processes (10), (11). In our presentation, we will show energy density improvements with SLMP in LIB as well as discuss its use for beyond lithium ion applications (12). References Straubel, J. B. "Driving Range for the Model S Family." Tesla Motors, 30 Dec. 2014. Web. B. H. Kim, et al., The effect of oxygen pressure on the synthesis of LiNiO2. Solid State Phenomena, Vols. 124-126, (2007), p. 1043-1046 P. Kalyani, N. Kalaiselvi, Various aspects of LiNiO2 chemistry: A Review. Science and Technology of Advanced Materials, 6, (2005), p. 689–703 Kim, M.-H., Shin, H.-S., Shin, D. & Sun, Y.-K., Synthesis and electrochemical properties of Li[Ni0.8Co0.1Mn0.1]O2 and Li[Ni0.8Co0.2]O2 via co-precipitation. Journal of Power Sources, (2006), 159, p. 1328-1333 Yushin, G. et al., High-performance Lithium-ion Anodes Using a Hierarchical Bottom-up Approach. Nature Materials, 9, (2010), 353-58. <www.nature.com>. Koratkar, Nikhil et al., Nanostructured Silicon Anodes for Lithium Ion. Small Journal, 20, (2009), p. 2236-242. Hui Zhao, Wei Yang, Ruimin Qiao, Chenhui Zhu, Ziyan Zheng, Min Ling, Zhe Jia, Ying Bai, Yanbao Fu, Jinglei Lei, Xiangyun Song, Vincent Battaglia, Wanli Yang, Phillip Messersmith, and Gao Liu, Conductive polymer binder for high-tap-density nano-silicon material for lithium ion battery negative electrode application. Nano Letters, (2015), 15, p. 7927-7932. C. R. Jarvis, M.J. Lain, Y. Gao, and M. Yakovleva, J. Power Sources, 146, 331 (2005). Y. Li, B. Fitch, Electrochem. Commun., 13, (2011) 664. Guo Ai, Zhihui Wang, Hui Zhao, Wenfeng Mao, Yanbao Fu, Vincent Battaglia, Sergey Lopatin, and Gao Liu, Scalable process for application of stabilized lithium metal powder in Li-ion batteries. Journal of Power Sources, (2016). Zhihui Wang , Yanbao Fu , Zhengcheng Zhang , Shengwen Yuan , Khalil Amine,Vincent Battaglia , Gao Liu, Application of Stabilized Lithium Metal Powder (SLMP) in graphite anode-A high efficient prelithiation method for lithium-ion batteries, Journal of Power Sources, 260, (2014), 57e61 Margret Wohlfahrt-Mehrens, Manuel Weinberger, Novel strategies towards the realization of larger lithium sulfur/silicon pouch cells. Electrochimica Acta, Volume 191, 10, February (2016), p. 124–132. Figure 1

Synthesis of Metal Oxide Precursors for the Generation of Oxides or Similar Nanomaterials for Na-Ion Battery Cathode Production

The current growing need of energy storage is an issue that can be solved at least partially by electrochemical storage, like batteries. Nowadays, most of the Li-ion battery cathodes are made of lithium cobalt oxide, LiCoO2, prepared by highly energy consuming solid state processes, involving solid state method at high temperature and for long reaction times (600-900°C, 36hours [1]). Aurelien Crochet and Jean-Pierre Brog of the Fromm group developed a way of producing the high-temperature phase of LiCoO2 (HT-LiCoO2) [2] at low temperature using heterometallic Li-Co alkoxides complexes as molecular precursors, following the general equation below. [Li2Co(OR)4(L)4] → HT-LiCoO2 + Li2CO3 + CO2 + H2O Despite lower performances, Na-ion batteries are good candidates in an effort to produce cheaper and more environmentally friendly batteries compared to Li-ion batteries. Complexes of [NaxMy(OR)z(L)a], where M is a transition metal, OR an alkyl or aryl oxide group and L a ligand, can be synthesized in analogy to the lithium precursors in order to use them for the generation of sodium metal oxides. Those oxides will be characterized and tested as cathode materials. We will present our first efforts and results on this kind of synthesis.

The cost of lithium is unlikely to upend the price of Li-ion storage systems

As lithium ion batteries become more common in electric vehicles and other storage applications, concerns about the cost of their namesake material, and its impact on the cost of these batteries, will continue. However, examining the constituent materials of these devices shows that lithium is a relatively small contributor to both the battery mass and manufacturing cost. The use of more expensive lithium precursor materials results in less than 1% increases in the cost of lithium ion cells considered. Similarly, larger fluctuations in the global lithium price (from $0 to $25/kg from a baseline of $7.50 per kg of Li2CO3) do not change the cost of lithium ion cells by more than 10%. While this small cost increase will not have a substantial impact on consumers, it could affect the manufacturers of these lithium ion cells, who already operate with small profit margins.

Different hydrolytic stabilities of some C,N-chelated germanium alkoxides

C,N-intramolecularly coordinated germanium(IV) methoxides Ar3GeOMe (1) and (Ar′)2Ge(OMe)2 (2) [where Ar=[2-(Me2NCH2)C6H4]−, Ar′=[2-(DipN=CH)C6H4]−, Dip=2,6-(i-Pr)2C6H3] were prepared by the reaction of the lithium precursors ArLi and Ar′Li with Ge(OMe)4 in appropriate molar ratio. While the diorganogermanium(IV) compound 2 is air-stable specie, triorganogermanium(IV) compound is surprisingly smoothly hydrolyzed by air-moisture to corresponding triorganogermanol Ar3GeOH (3). Studied compounds were characterized by the help of multinuclear NMR spectroscopy and in the case of 2 and 3 using single-crystal X-ray diffraction analysis.

Atomic Layer Deposition of Lithium Phosphorus Oxynitride

An atomic layer deposition (ALD) process is successfully developed for fabricating high-quality lithium phosphorus oxynitride (LiPON) thin films for a potential use as a conformal solid-state electrolyte coating in 3D Li-ion microbattery technology. In our ALD process the challenge of simultaneously incorporating phosphorus and nitrogen in the films is overcome by using a novel nitrogen-containing phosphorus precursor, diethyl phosphoramidate, together with lithium hexamethyldisilazide as the lithium precursor. A temperature window is found around 270–310 °C, where homogeneous films are realized and the film growth is controlled in a digital manner by the number of ALD cycles at a rate of ∼0.7 Å/cycle. The process allows for a high N-to-P ratio in the films, which is beneficial for achieving the required high ionic conductivity. For a film deposited at 330 °C with a composition of Li0.95PO3.00N0.60 according to RBS/NRA analysis, an ionic conductivity value as high as 6.6 × 10–7 S cm–1 is measured at 25 °C.

Facile synthesis of macroporous Li4SiO4 with remarkably enhanced CO2 adsorption kinetics

Lithium orthosilicate (Li4SiO4) has attracted extensive scientific attention due to its large CO2 adsorption capacity at high temperature (650–700°C) and low material cost. However, the conventional nonporous Li4SiO4 ceramic shows very poor CO2 adsorption performance below 600°C, which is a relevant condition for possible applications such as sorption-enhanced steam methane reforming. In the present work, in order to increase the CO2 adsorption kinetics below 600°C, Li4SiO4 was synthesized in the form of a macroporous structure by a simple solid-state transformation method using LiOH and fumed silica as a precursor for Li and SiO2, respectively. The use of LiOH substantially decreased the synthesis temperature of Li4SiO4 down to 600°C, compared with the conventional syntheses using other lithium precursors such as Li2CO3 and LiNO3 that require very high synthesis temperature (>700°C). The decrease of the material synthesis temperature circumvents undesirable sintering of initially formed small Li4SiO4 crystallites and leads to the formation of a highly macroporous (macropore volume >0.6mLg−1) Li4SiO4 framework that has a significantly higher BET surface area (15m2g−1) than conventional nonporous Li4SiO4 (<1.0m2g−1). The macroporous Li4SiO4 exhibited dramatically enhanced CO2 adsorption capacity (29.8wt%) and rate (56.1mgg−1min−1), compared with the CO2 adsorption capacities (1.40–7.79wt%) and rates (0.420–2.95mgg−1min−1) of nonporous Li4SiO4 materials. Adsorption–desorption cycles at 550°C could be repeated 10 times without a significant decrease in the adsorption capacity or the rate capability.

Influence of Lithium Precursors and Calcination Atmospheres on Graphene Sheets-Modified Nano-Li4Ti5O12 Anode Material

With the advantageous features include suitable lithium insertion position and "zero strain" structure, Li4Ti5O12 has become one of the ideal anode materials for lithium-ion battery and battery-capacitor system. However, the obstacle of its poor electronic and Li+ conductivity restrict its rate capacity. Many researches proved that the one-pot preparation process, which is mixing the carbon precursor with lithium and titanium precursor and then thermal treating in an inert or reducing atmosphere together, not only can form a carbon coating layer to improve the electronic property of the materials easily, but also inhibits the particle size growth of LTO by a barrier effect of carbon. Among kinds of carbon source, graphene presents excellent unique properties, which has been considered as an ideal carbon source to improve the electrochemical performance of LTO and many other active materials. However, the intersheet π-π attractions of GS easily resulted in its restacking and agglomeration. Therefore, an oxygenated graphene (GO) with a special amphiphilic molecular structure is adopted as GS precursor to prepare GS modified composites. Due to the amphiphilic characteristic of GO, the choice of an appropriate Li precursor is extremely important to obtain a high quality product. In this study, we systematically investigated the influence of lithium precursor and calcination atmosphere on the reaction mechanisms, phase formation, particulate morphology, surface properties and electrochemical performance of graphene sheets-modified nano-Li4Ti5O12 composite. The results shown that the lithium precursor containing carboxyl anion such as LiAc and Li2CO3 would connect with oxygen groups of GO by strong hydrogen bonds to restrict the morphology of composites and the phase formation of pure spinel Li4Ti5O12. Furthermore, the oxygen ratio in the molecular structure of lithium compound is proportional to the consumption of graphene. In addition, the reducing atmosphere facilitates the partial reduction of Ti4+ to promote the interfacial charge transfer kinetics of the product. Through optimization the conditions of the reaction, the sample adopting LiOH precursor with adjustment GS ratio calcined under Ar/H2 (5 %) atmosphere delivers 172.8 mAh g-1 at 1 C and maintained a discharge capacity of 98.0 mAh g-1 at a high rate of 40 C. This sample also showed fairly stable cycling performance. After 800 deep cycles at a high charge/discharge rate of 40 C, the capacity can hold 97.7 % of its second discharge value. This study not only provides an optimization of Li precursor and calcination condition for GS modified LTO material, but also has significant reference value for any combination reaction with GO participation.

Highly substituted zirconium and hafnium cyclopentadienyl bifunctional β-diketiminate complexes – Synthesis, structure, and catalytic activity towards ethylene polymerization

A series of tetramethyl-(Cp′) and pentamethylcyclopentadienyl (Cp*) metal complexes (η5-C5Me4R)ZrCl2LCO (R = H(1), Me(2)) and (η5-C5Me4R)HfCl2LCO (R = H(3), Me(4)) where LCO is a bifunctional β-diketiminate ligand [2-(MeO)–C6H4)]NC(Me)CHC(Me)N[2-(MeO)–C6H4)] (LCO) were prepared from corresponding tetramethyl- and (pentamethylcyclopentadienyl)metal trichlorides and the lithium precursor LiLCO. All complexes were characterized by their melting point, elemental analysis, 1H and 13C NMR spectroscopy, IR spectroscopy. In addition their solid-state structures were determined by X-ray diffraction techniques. In all cases, a pseudo-tetragonal pyramidal coordination environment of the metal centre with cyclopentadienyl ligand on the top and nearly isobidentately bonded nitrogen atoms of the chelating LCO ligand in an open η5-fashion was observed. The oxygen atoms positioned at the diketiminate periphery remained uncoordinated to transition metal in the solid phase as well as in solution.Besides the desired compounds, two hafnium complexes bearing either 2-methoxyaniline or 2-methoxyanilide ligands were isolated and structurally characterized as minor decomposition and dismutation products of 3 and 4, respectively.Complexes containing the β-diketiminate ligand as well as its precursors were tested for catalytic activity in the polymerization of ethylene using different activators (MAO, MMAO and AliBu3/(Ph3C)+ [B(C6F5)4]−). Among the new complexes, the best activity as high as 340 kgPE (molMhbar)−1 was achieved with 1/AliBu3/(Ph3C)+ [B(C6F5)4]− system.In attempts to clarify the activation process of group 4 metal-based precatalysts, the synthesis and NMR studies of the aluminium β-diketiminate complex Al(iBu)2LCO were also carried out.

Influence of lithium precursors and calcination atmospheres on graphene sheets-modified nano-Li4Ti5O12 anode material

The influence of Li precursors and calcination atmospheres on the reaction mechanisms, physical properties and electrochemical performance of graphene sheets (GS)-modified nano-Li4Ti5O12 (LTO/GS) has been systematically investigated. Field emission scanning electron microscopy (FE-SEM) and mass spectrometry (MS) results demonstrate the lithium precursor containing carboxyl anion such as lithium acetate (LiAc) and Li2CO3 interact with oxygen groups of graphene oxide (GO) by strong hydrogen bonds to restrict the morphology and the phase formation of products. We also notice from the thermogravimetry (TG) and MS results that the consumption of GS is proportional to oxygen content of lithium precursor. Cyclic voltammetry (CV) and X-ray photoelectric spectroscopy (XPS) results indicate that the product calcined in reducing atmosphere possess smaller electrochemical polarization due to more reduced Ti3+ on the surface of the product. The LTO/GS sample with LiOH as Li precursor calcined in diluted hydrogen atmosphere show the best electrochemical performance with a capacity of 134.4 mAh g−1 at 10C discharge rate and very stable cycling life with a 98.6% capacity retention after 800 cycles at 40C rate. This study not only provides an optimization of Li precursor and calcination condition for LTO/GS anode material, but also guides any future one-step syntheses of lithium composite materials with GO participation.

Structural Studies of (rac)-BIPHEN Organomagnesiates and Intermediates in the Halogen–Metal Exchange of 2-Bromopyridine

Four lithium magnesiate complexes (2–5) containing the dianionic (rac)-BIPHEN ligand have been prepared and characterized using X-ray crystallography and NMR spectroscopy. (THF)3·Li2Mg{(rac)-BIPHEN}nBu2, 2, (THF)3·Li2Mg{(rac)-BIPHEN}(CH2SiMe3)2, 3, and (THF)2·Li2Mg{(rac)-BIPHEN}neoPe2, 4, have been prepared by complexation of the appropriate dialkylmagnesium compound with in situ prepared Li(rac)-BIPHEN in a mixture of hydrocarbon/THF. For all structures, the Mg centers are four-coordinate (and retain the alkyl groups); however, in 2 and 3 the two Li centers have different coordination spheres (one binding to one THF molecule, the other to two). The solid-state structures of 2 and 3 are essentially isostructural with that of 4 except that both Li atoms in this molecule have equivalent coordination spheres. The solution behaviors of these three molecules have been studied by 1H, 13C, and DOSY NMR spectroscopy. During the synthesis of 2, it was discovered that a (rac)-BIPHEN-rich (or n-butyl-free) lithium magnesiate, (THF)4Li2Mg{(rac)-BIPHEN}fo2, 2b, could be isolated. The lithium precursor to 2–5, (THF)4·Li4{(rac)-BIPHEN)}2, 1, has also been isolated. Within the molecular structure of this tetranuclear complex, there are three different Li coordination environments. Finally, 2 has already shown promise as a reagent in a halogen–metal exchange reaction with 2-bromopyridine. The structural chemistry at play in this reaction was probed by X-ray crystallography and NMR spectroscopy. The organometallic intermediate pyridyl-magnesiated 5, (THF)2·Li2Mg{(rac)-BIPHEN}(2-pyridyl)2, was isolated in high yield.

Reactivity of N,C,N-Chelated Antimony(III) and Bismuth(III) Chlorides with Lithium Reagents: Addition vs Substitution

N,C,N-chelated antimony(III) and bismuth(III) chlorides L1,2MCl2 (1–4: for L1, M = Sb (1), Bi (3); for L2, M = Sb (2), Bi (4)) containing ligands L1,2 (where L1 = C6H3-2,6-(CH═N-t-Bu)2, L2 = C6H3-2,6-(CH═N-2′,6′-Me2C6H3)2) were prepared by reactions of lithium precursors with SbCl3 or BiCl3. The identities of 1–4 were established both in solution (1H and 13C NMR spectroscopy) and, in the case of 1–3, in the solid state using single-crystal X-ray diffraction analysis. Treatment of antimony derivatives 1 and 2 with 2 molar equiv of R′Li (R = Me, n-Bu, Ph) yielded the set of substituted 1,3-(R′)2-2-R-7-(CH═NR)-1H-2,1-benzazastiboles 5–10 (where R = t-Bu, 2,6-Me2C6H3 and R′ = Me, n-Bu, Ph) as a result of a nucleophilic attack of one of the lithium compounds across the imino C═N functionality. In contrast, analogous reactions between bismuth congeners 2 and 4 and R′Li (2 equiv, R′ = Me, Ph) gave L1,2BiR′2 (11–13: for L1, R′ = Me (11), Ph (12); for L2, R′ = Me (13)) as products of substitution of chlorine atoms. Compounds 5–13 were characterized by the help of 1H and 13C NMR spectroscopy. The molecular structures of 8, 9, and 13 were unambiguously established using single-crystal X-ray diffraction analysis.

Electrochemical Properties of Li1+xCoO2 Synthesized for All-Solid-State Lithium Ion Batteries with Li2S-P2S5 Glass-Ceramics Electrolyte

The over-stoichiometric Li1+xCoO2 (x = 0.1, 0.2, and 0.3) cathode materials were synthesized from an aqueous solution of lithium nitrate (LiNO3) as an excess lithium precursor and their effects on the electrochemical properties of all-solid-state lithium batteries employing Li2S-P2S5 glass-ceramics solid electrolytes are investigated. A combination of X-ray diffraction, Fourier transform infrared spectroscopy, and inductively coupled plasma atomic emission spectroscopy reveals that the excess lithium forms a residual Li2CO3 layer on the surface of as-prepared Li1+xCoO2 particles during the synthesis process. While regarded as an impurity phase in lithium battery systems using liquid electrolytes due to its detrimental effects on electrochemical performance, the Li2CO3 formed on the surface of the over-stoichiometric Li1+xCoO2 powders is identified in all-solid-state lithium battery systems using sulfide solid electrolytes to act as an effective coating material to suppress the interfacial side reactions despite its low ionic and electronic conductivity.

Synthesis and Characterization of Co Doped Nickel-Manganese Based Spinel-Layered Mixed Structure as Cathode Active Materials

LiCoO2 is a most popular cathode material in lithium battery industries. But the high cost and toxicity of cobalt have drawn attention to find alternative materials. Manganese of various alternative materials has been highly considered as alternative because it is environmentally friendly and inexpensive. For the lithium ion battery applications in medium and largescale energy devices, a new active material with structural stability and high capacity is essential. So, in this study, we have synthesized spinel-layered mixed structured composite oxides based on Mn,Ni, with stable structure and high capacity for Li ion battery cathodes. The materials were synthesized and characterized for its structural and electrochemical properties. We used a batch type reactor equipped with a teflon-type impeller at a stirring speed of 150~400rpm for material synthesis. Initially, we synthesized the transition metal precursor using co-precipitation method. We then synthesized the spinel. layered mixed structure by mixing the synthesized precursor with the lithium precursor by calcination. But on battery cycling, after 50cycle, Co undoped sample exhibited very low stability with capacity maximum of approximately 90mAh/g. We also synthesized Co-doped (Co-composition x=0.05, 0.15, 0.25) transition metal precursor using solid state method. Then again by using previous method we synthesized the spinel-layered mixed structure by mixing the synthesized Co-doped precursor and lithium precursor by calcination. The transition metal precursor showed MnCO3 (rhodochrosite, R-3c, JCPDF 44-1472) structure and the final material showed spinel and layered mixed structure which was confirmed with XRD. Electrochemical properties were tested at a current density of 0.2mA/cm2within a potential range of 2.0V~4.9V using a 2032 coin type lithium cell. All samples showed the spinel-layered mixed characteristic charge-discharge curves and Co doped sample synthesized at Co composition x-0.15 showed highest stability with capacity maximum of 220mAh/g.

Significant influence of insufficient lithium on electrochemical performance of lithium-rich layered oxide cathodes for lithium ion batteries

With an aim to broaden the understanding of the factors that govern electrochemical performance of lithium-rich layered oxide, the influences of insufficient lithium on reversible capacity, cyclic stability and rate capability of the oxide as cathode of lithium ion battery are investigated in this study. Various concentrations of lithium precursor are introduced to synthesize a target composition Li[Li0.13Ni0.30Ni0.57]O2, and the resulting products are characterized with inductively coupled plasma spectrum, scanning electron microscope, X-ray diffraction, Raman spectroscopy, and electrochemical measurements. The results indicate that the lithium content in the resulting oxide decreases with reducing the concentration of lithium precursor from 10wt%-excess lithium to stoichiometric lithium, due to insufficient compensation for lithium volatilization during synthesis process at high temperature. However, all these oxides still exhibit typically structural and electrochemical characteristics of lithium-rich layered oxides. Interestingly, with decreasing the Li content in the oxide, its reversible capacity increases due to relatively higher content of active transition-metal ions, while the cyclic stability degrades severely because of structural instability induced by higher content of Mn3+ ions and deeper lithium extraction.

Synthesis and Characterization of Titanium 7‐Azaindolato Complexes and their Lithium Precursors

AbstractTwo differently 2‐substituted 7‐azaindoles (substituent = H (1‐H), t‐Bu (1‐tBu)) react with n‐butyllithium in tmeda to give different Li complexes. Using the ligand 1‐H, the binuclear complex [(tmeda)Li(azH)]2 (2‐H) is formed. The sterically more demanding ligand 1‐tBu leads to formation of the mononuclear Li complex (tmeda)Li(aztBu) (2‐tBu). The decamethyltitanocene bis(trimethylsilyl)acetylene complex Cp*2Ti(η2‐Me3SiC2SiMe3) (3a) reacts with 7‐azaindole (1‐H) to give the dark red titanocene(III) complex 4. Using the sterically more demanding 1‐tBu ligand upon deprotonation with dialkylmagnesium, followed by subsequent salt metathesis with (Cp2TiCl)2, the dark green titanocene(III) heterometallacyclic complex 5 is obtained. Complexes 2‐H, 2‐tBu and 5 were characterized by X‐ray analyses.