Surfactant-assisted sol gel preparation of high-surface area mesoporous TiO2 nanocrystalline Li-ion battery anodes

We here investigate the physico-chemical/morphological characteristics and cycling behaviour of several kinds of nanocrystalline TiO2 Li-ion battery anodes selectively prepared through a simple sol-gel strategy based on a low-cost titanium oxysulfate precursor, by mediation of different cationic surfactants having different features (e.g., chain lengths, counter ion, etc.): i.e., cetyl-trimethylammonium bromide (CTAB), cetyl-trimethylammonium chloride (CTAC), benzalkonium chloride (BC) or octadecyl-trimethyl ammonium bromide (C18TAB). X-ray diffraction profiles reveal single phase anatase having good correspondence with the reference pattern when using short chain CTAB, while in the other cases the presence of chloride and/or an increased chain length affect the purity of the samples. FESEM analysis reveal nanosized particles forming cauliflower-like aggregates. TiO2 materials demonstrate mesoporous characteristics and large specific surface area ranging from 250 to 30 m2 g−1. Remarkably stable electrode performance are achieved by appropriately selecting the cationic surfactant and the surfactant/precursor ratio. Detailed analysis is provided on the effect of the reaction conditions upon the formation of mesoporous crystalline titania enlightening new directions for the development of high performing lithium storage electrodes by a simple and low cost sol-gel strateg

Quantification of aging mechanisms of carbon-coated and uncoated silicon thin film anodes in lithium metal and lithium ion cells

In this work, a comprehensive investigation of the effect of carbon-coating on the aging mechanism of silicon thin films in lithium metal and lithium ion cells is presented. In Li||Si cells with sufficient lithium excess, 92% of the total capacity loss of the silicon film was attributed to a loss of active material and 8% was attributed to an increased cell resistance. Carbon-coating reduces the loss of active material by improving the mechanical integrity of the silicon thin film, leading to a 67% reduction of capacity loss per cycle. In Si||LiFePO4 lithium ion cells, 86% of the total capacity loss was attributed to a loss of lithium inventory and 14% attributed to an increase in cell resistance. Furthermore, a loss of 69% of silicon active material was observed. Carbon-coating reduces the capacity loss per cycle by 28%. After aging of the lithium ion cells, the negative electrode of the carbon-coated silicon retained double the capacity compared to the uncoated silicon electrode. Hence, carbon-coating is an effective measure to improve mechanical stability of silicon thin film electrodes, but it must be coupled with additional strategies to reduce lithium consumption in order to increase the overall effectiveness of the coating in lithium ion cells

α-Fe2O3 lithium battery anodes by nanocasting strategy from ordered 2D and 3D templates

Nanocasting strategy is here proposed as effective approach to tune structure and size of α-Fe2O3 active nanoparticles as a promising anode material for Li-ion cells. MCM-41 and MCM-48 silicas, presenting hexagonal 2D and cubic 3D symmetry, respectively, and regular pore diameter of about 4 nm are selected as moulds. The structural–morphological and electrochemical characteristics are assessed by X-ray diffraction, transmission electron microscopy, N2 physisorption at 77 K, cyclic voltammetry and galvanostatic discharge/charge cycling. It is here demonstrated that structural–morphological features change accordingly to the template used and careful control of the texture/particle characteristics is likely a fundamental variable noticeably affecting the cycling behaviour

Intraoperative evaluation of total knee replacement: Kinematic assessment with a navigation system

Abstract Interest in the kinematics of reconstructed knees has increased since it was shown that the alteration of knee motion could lead to abnormal wear and damage to soft tissues. We performed intraoperative kinematic measurements using a navigation system to study knee kinematics before and after posterior substituting rotating platform total knee arthroplasty (TKA). We verified intraoperatively (1) if varus/valgus (VV) laxity and anterior/ posterior (AP) laxity were restored after TKA; (2) if TKA induced abnormal femoral rollback; and (3) how tibial axial rotation was influenced by TKA throughout the range of flexion. We found that TKA improved alignment in preoperative osteoarthritic varus knees which became neutral after surgery and maintained a neutral alignment in neutral knees. The VV stability at 0 was restored while AP laxity at 90 significantly increased after TKA. Following TKA, the femur had an abnormal anterior translation up to 60 of flexion, followed by a small rollback of 12 ± 5 mm. TKA influenced the tibia rotation pattern during flexion, but not the total amount of internal/external rotation throughout whole range of flexion, which was preserved after TKA (6 ± 5). This study showed that the protocol proposed might be useful to adjust knee stability at time zero and that knee kinematic outcome during total knee replacement can be monitored by a navigation system

Anodic Materials for Lithium-ion Batteries: TiO2-rGO Composites for High Power Applications

Titanium dioxide/reduced graphene oxide (TiO2-rGO) composites were synthesized at different loadings of carbonaceous phase, characterized and used as anode materials in Lithium-ion cells, focusing not only on the high rate capability but also on the simplicity and low cost of the electrode production. It was therefore chosen to use commercial TiO2, GO was synthesized from graphite, adsorbed onto TiO2 and reduced to rGO following a chemical, a photocatalytic and an in situ photocatalytic procedure. The synthesized materials were in-depth characterized with a multi-technique approach and the electrochemical performances were correlated i) to an effective reduction of the GO oxidized moieties and ii) to the maintenance of the 2D geometry of the final graphenic structure observed. TiO2-rGO obtained with the first two procedures showed good cycle stability, high capacity and impressive rate capability particularly at 10% GO loading. The photocatalytic reduction applied in situ on preassembled electrodes showed similarly good results reaching the goal of a further simplification of the anode production

Al2O3 protective coating on silicon thin film electrodes and its effect on the aging mechanisms of lithium metal and lithium ion cells

In this work, an investigation of the effect of Al2O3-coating on the aging mechanisms of silicon anode thin films in lithium metal and lithium ion cells is presented. Aging mechanisms, namely: loss of lithium inventory, loss of silicon active material and loss of utilizable capacity due to an increase of cell resistance were determined for both, Li||Si and Si||LiFePO4 cells. Al2O3-coating was shown to be an effective strategy to reduce the loss of lithium inventory, while having a marginal effect on decreasing the loss of silicon active material. Indeed, in case of Si||LiFePO4 cells, where fading is governed by loss of lithium inventory, a 5 nm Al2O3-coating leads to a significant reduction (-64%) of the capacity fade per cycle. On the contrary, in case of Li||Si, where the aging mechanism is governed by the loss of active material, Al2O3-coated and uncoated silicon showed comparable tendencies regarding the capacity fade per cycle. It emerges, also, that loss of silicon active material and loss of lithium inventory are independent of each other. This indicates that the main contribution of loss of lithium inventory is not the lithium trapped in electrically insulated silicon, but rather lithium consumed in the ongoing SEI formation. Al2O3-coating could reduce the latter due the insulating nature of the coating. Ex situ investigations of the SEI by means of X-ray photoelectron spectroscopy confirmed a decrease in solvent decomposition in presence of the Al2O3-coating

Polymer electrolytes for safe Lithium ion, electrochromic and photovoltaic applications

Polymer electrolytes represent the ultimate in terms of desirable properties for Li-ion batteries, but also other applications as electrochomic devices, lithium air and photovoltaic cells. They can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low-cost of fabrication, high safety and a higher energy density. The use of the polymer electrolyte with the same basic composition can simplify the production of devices for end users and can get the possibility to produce cointegrated devices when needed. Here, we describe the use and the electrochemical characterization of gel-polymer and all solid state membranes based on methacrylates and polyethene oxides produced both by UV curing technique and by thermopolymerization and their application in Lithium ion cells, flexible electrochromic devices and PV cells. The ionic conductivity of the studied membranes showed good ionic conductivity values in the order of 10-3 Scm-1 at room temperature and the anodic breakdown voltage higher than 4.5 V vs. Li. Due to the production method, an high electrode-electrolyte interface can be obtained leading to high electrochemical performance, e.g long cyclability, high C rates, and simple scalability for industrial applications. By this method we are able to produce flexible, transparent films of varying thickness in less than 5min, and the whole process for production of polymer membranes from minutes to less than 1 h. All processes are very versatile and easily permits to change the polymer compositio

Polymer electrolytes for safe Lithium ion, electrochromic and photovoltaic applications

Polymer electrolytes represent the ultimate in terms of desirable properties for Li-ion batteries, but also other applications as electrochomic devices, lithium air and photovoltaic cells. They can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low-cost of fabrication, high safety and a higher energy density. The use of the polymer electrolyte with the same basic composition can simplify the production of devices for end users and can get the possibility to produce cointegrated devices when needed. Here, we describe the use and the electrochemical characterization of gel-polymer and all solid state membranes based on methacrylates and polyethene oxides produced both by UV curing technique and by thermopolymerization and their application in Lithium ion cells, flexible electrochromic devices and PV cells. The ionic conductivity of the studied membranes showed good ionic conductivity values in the order of 10-3 Scm-1 at room temperature and the anodic breakdown voltage higher than 4.5 V vs. Li. Due to the production method, an high electrode-electrolyte interface can be obtained leading to high electrochemical performance, e.g long cyclability, high C rates, and simple scalability for industrial applications. By this method we are able to produce flexible, transparent films of varying thickness in less than 5min, and the whole process for production of polymer membranes from minutes to less than 1 h. All processes are very versatile and easily permits to change the polymer composition