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A correlation between band alignment at an electron transport layer/perovskite interface and the locus of hysteresis in perovskite solar cells is proposed.

Achieving aggregation-free nanocomposites is a challenge for the conventional casting process in Li-ion battery electrode fabrication, which leads to inhomogeneous dispersion of active and conductive components – a property which further accelerates, or triggers, battery degradation. This becomes even more challenging when using 2D nanomaterials. In this paper, electrophoretic deposition (EPD) is used to fabricate nanolayered composite anodes composed of spinel lithium titanate (LTO) and reduced graphene oxide (rGO). First, the electrode material precursors, 2D-lithium titanate hydrate (LTH) and graphene oxide nanosheets, are formulated into a stable colloidal suspension and electrophoretically co-deposited (EPD) onto copper substrate. Subsequently, the binder-free deposits are annealed at 600 ​°C in a 5% hydrogen environment for 6 ​h to induce in-situ topotactic transformation of the precursors into LTO/rGO nanolayered composites. Comparing to their PVDF-built electrodes, the EPD nanolayered composites exhibit robust electrochemical performance in terms of power capability, cyclability and impedance control. This performance enhancement is due to a well-established graphene oxide-based percolation network for both electronic and ionic conduction engineered with the help of EPD. Therefore, the local deep discharge to lower state-of-charges is avoided, hence avoiding the serious capacity fade from which nano-LTO suffers. Through this research, EPD casting technology presents itself as superior mesoscale construction strategy for nanostructured LIB electrodes.

Direct photo-to-chemical energy conversion realized through photocatalysis could provide the ultimate solution to the intermittency problem of solar energy. Among different designs of photocatalytic solar energy storage systems, the two-electrode system offers the simplest configuration for enabling highly integrated solar energy conversion and storage in one electrode and on-demand electrocatalytic discharge in the other. In this study, a novel type of visible light chargeable two-electrode Na-ion energy storage system has been developed, to the best of our knowledge, for the first time. It consists of a WO3–(TiO2)–CdS photo absorbing, energy storing bi-functional electrode, a Pt foil counter electrode, and a sacrificial hole scavenging electrolyte. This device delivered a discharge capacity of 12.3 μA h cm−2 (or 18.1 mA h g−1) after 10 min light charging without exhibiting signs of photo/chemical corrosion on the chalcogenide sensitizer. Further by controlling the working voltage window, structure distortion due to overcharging was avoided, thereby leading to an improvement of cyclability (discharge capacity retention after 5 working cycles) from 36% to 64%, and this was eventually elevated to ∼90% upon optimizing the discharging rate. A stable overall solar-to-electrical energy efficiency of ∼0.3% has been achieved for the system. Moreover, a modified photo-rechargeable two-electrode system was developed by replacing the sacrificial hole scavenger and Pt with polysulfide aqueous electrolyte and Cu2S electrocatalytic electrode, respectively. In this way the issue of non-regenerable hole scavenger consumption and instability of Pt in sulfide electrolyte was resolved, establishing a new design, highly promising towards the development of an all-sustainable photo-rechargeable system.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate (TiNb2O7, TNO)/rGO anodes upon reductive annealing. Control tests revealed that EPD is superior to conventional PVDF-based casting in maximizing the performance benefits from using reduced GO in Li-ion electrode fabrication as is the case of TNO that is plagued with conductivity and capacity fading problems. In this particular study, we show that there is a synergy developed between GO and EPD with the former (1) stabilizing the EPD suspension, (2) acting as a flexible binder net that affords mechanical integrity during the volume expansion of TNO, (3) serving as a conductive filler, and (4) contributing to Li-ion storage via pseudocapacitance. As a consequence, a superior percolation network is developed. Thus while both EPD- and PVDF- built TNO/rGO composite anodes exhibited high initial capacities (∼350 and 318 mA h g−1) at 0.5 C cycling, respectively, their cycling behaviour was quite different with the latter experiencing high internal polarization and extended degradation. Post-mortem PEEM-XANES analysis clearly demonstrated a highly homogeneous mesostructure in the case of the EPD-built TNO/rGO anode vs. a highly segregated and dis-jointed rGO and TNO component clustering in the PVDF-built electrode.

To describe the clinical characteristics, perioperative protocols, and outcomes in dogs diagnosed with ventricular fibrillation (VF) while undergoing pericardiectomy.Retrospective, multi-institutional study.Sixteen client-owned dogs.Cases were accrued through a listserve request posted to 3 subspecialty veterinary societies. Dogs were included if they developed VF during a pericardiectomy performed through an open or thoracoscopic approach. Data collected included signalment, history and physical examination, surgical approach, histopathology, treatment, and outcome.Indications for pericardiectomy included idiopathic chylothorax (n = 7), neoplasia (4), idiopathic pericardial effusion (4), and foreign body granuloma (1). Surgical approaches included thoracoscopy (12), intercostal thoracotomy (3) and median sternotomy (1). Electrosurgical devices were used to complete at least part of the pericardiectomy in 15 of 16 dogs. Ventricular fibrillation appeared to be initiated during electrosurgical use in 8/15 dogs. However, in 5/15 dogs it was not obviously associated with electrosurgical use. In 3/16 dogs the timing of initiation of VF was unclear. In 7/16 dogs, cardiac arrhythmias were noted prior to the development of VF. Fourteen of 16 dogs died from intraoperative VF.In most dogs ventricular fibrillation was a fatal complication of pericardiectomy. Ventricular fibrillation might be associated with the use of electrosurgical devices and cardiac manipulation during pericardiectomy although a causal link could not be established from the data in this study.Surgeons must be aware of the risk of VF during pericardial surgery. Electrosurgery might need to be used judiciously during pericardiectomy, particularly in dogs exhibiting cardiac arrythmias.

OBJECTIVE To evaluate the feasibility of CT lymphangiography via intrametatarsal pad injection in cats with chylothorax. ANIMALS 7 client-owned cats. PROCEDURES This was a multicenter, retrospective, descriptive study. Medical records and imaging data from 4 veterinary hospitals were reviewed to identify cats with chylothorax that had undergone intrametatarsal pad injection via CT lymphangiography. In total, 7 client-owned cats were included in the study. Signalment, history, image findings, and follow-up data were recorded. Descriptive statistics were used to analyze the success rate of thoracic duct (TD) enhancement and describe relevant clinical findings. RESULTS Enhancement of TDs was successful in 6 of the 7 cats within 5 to 15 minutes after initiating intrametatarsal pad injection under general anesthesia. Successful migration of contrast medium into the lymphatic vessels cranial to the popliteal lymph nodes was observed in all cats within 5 minutes after injection. The recommended dose of contrast medium to achieve TD enhancement was 1 mL/kg (0.5 mL/kg/pad; concentration, 350 mg of iodine/kg). Only 1 cat had mild swelling of the paws after the procedure, and it recovered quickly without pain medication; no cats experienced lameness. Similar to dogs and unlike in previously published reports, 72% of TD branches were located in the right hemithorax. CLINICAL RELEVANCE CT lymphangiography via intrametatarsal pad injection is a feasible and safe procedure for cats with chylothorax. This technique provides detailed information regarding the unique TD anatomy and cisterna chyli location. It also contributes to surgical planning.

Integration of solar-energy harvesting and storage functions has attracted significant research attention, as it holds promise for ultimate development of light-chargeable devices. In this context, a functional nanocomposite anode that not only permits electrochemical energy storage through Li-ion photo-intercalation, but also exhibits potential for photoelectrochromic applications, was investigated. The nanocomposite is made of the Li-ion intercalation compound WO3 , thinly coated with TiO2 and sensitized by the photoactive semiconductor CdS. During light exposure, the photoelectrons from CdS are transported to the WO3 /electrolyte interface, where Li-ion intercalation takes place. Photoelectron transport is facilitated by the interfacial TiO2 layer. The WO3 was shown to be functional in multiple photocharge-discharge cycles, but the CdS suffers from degradation and photocorrosion. Hence, the selection of compatible semiconductors and protective coating strategies should be pursued to overcome these issues.

Lithium transition metal orthosilicates such as Li2FeSiO4 (LFS) have been recognized as promising cathode materials for application in Li-ion batteries because of their high theoretical energy density, safety, and benign/abundant element composition. Their development, however, has been hampered by the challenge of obtaining phase-pure and defect-free Li2FeSiO4 nanoparticles as non-optimized crystal properties have an adverse effect on structural stability and electrochemical performance. Considering the sustainable potential of hydrothermal synthesis in producing electrode materials, here we employ this process to systematically study critical synthesis parameters for optimal control of particle size, morphology, phase purity, and defects of Li2FeSiO4 crystallized in the orthorhombic crystal system with space group Pmn21. It is shown that via a combination of elevated FeSO4 concentration regime and use of EDTA as a complexing agent, phase-pure Pmn21 particle formation can be controlled. Synchrotron-based XRD Rietveld refinement and 57Fe Mossbauer spectroscopy reveal a significant reduction in Li-Fe antisite defects and presence of Fe3+. Additionally, the use of EDTA promotes the formation of unique peanut-shell looking hollow mesocrystals that are advantageous in maximizing electrode/electrolyte contact resulting in higher Li-ion storage capacity than dense LFS particles. On the basis of detailed XRD, SEM, and TEM characterizations, a four-step crystallization mechanism is proposed to explain the formation of the hollow mesocrystals. These findings bring new insight into our pursuit of optimization of Li2FeSiO4 as a cathode material for Li-ion batteries.

In this work, a relatively inactive cathode material, βII orthorhombic Li2FeSiO4 with the Pmn21 space group, is shown to undergo crystal structural changes when subjected to nanosizing by high-energy milling that have a pronounced activation impact on Li-ion intercalation electrochemistry. In particular, we present evidence of mechanically induced structural annealing including lattice expansion, reduction of anti-site defects and preferred crystal orientation, opposite of what expected typically from nanosizing. As a result of this type of unreported structural activation for orthosilicates, a threefold increase of the accessible discharge (=intercalation) capacity of the high-energy milled Pmn21 material is attained, much higher than what would be expected solely from surface area increase due to nanosizing and surface area increase. Such mechanochemically induced structural annealing activates Li-ion diffusion (one order of magnitude enhancement in DLi) into less accessible sites via the combined effects of anti-site defect removal and modulation of the Fe–O coordination adjustment. Structural activation of intercalation materials via controlled mechanochemistry opens new possibilities in nanoengineering high energy density Li-ion storage electrodes.

Li2FeSiO4 (LFS) is a sustainable Li-ion cathode material composed of earth-abundant elements with potentially high energy density but suffers from limited reversible storage capacity (less than one Li), low intrinsic conductivities, and cycling instability. In search of deeper understanding of the structural chemistry of LFS towards overcoming some of these challenges, the viability of Fe-site doping by Co and other dopants in Pmn21 LFS is investigated using both first-principles calculations and experimental testing. Computational results suggest that the formation of Li2Fe1−xCoxSiO4 is energetically favorable, predictions confirmed by successful hydrothermal synthesis. Substitution of Co in LFS is revealed to have a dual effect; firstly catalyzing faster electrochemically induced phase transformation to the stable inverse-Pmn21 phase; and secondly enabling the formation of a low-resistant, uniform and stable fluorine-rich cathode-electrolyte interphase (CEI) layer that inhibits detrimental reactions between the cathode and electrolyte. As a result, Co-substituted LFS displays enhanced reversibility with 95% capacity retention after 50 cycles as compared to 80% of the undoped LFS.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate (TiNb2O7, TNO)/rGO anodes upon reductive annealing. Control tests revealed that EPD is superior to conventional PVDF-based casting in maximizing the performance benefits from using reduced GO in Li-ion electrode fabrication as is the case of TNO that is plagued with conductivity and capacity fading problems. In this particular study, we show that there is a synergy developed between GO and EPD with the former (1) stabilizing the EPD suspension, (2) acting as a flexible binder net that affords mechanical integrity during the volume expansion of TNO, (3) serving as a conductive filler, and (4) contributing to Li-ion storage via pseudocapacitance. As a consequence, a superior percolation network is developed. Thus while both EPD- and PVDF- built TNO/rGO composite anodes exhibited high initial capacities (∼350 and 318 mA h g-1) at 0.5 C cycling, respectively, their cycling behaviour was quite different with the latter experiencing high internal polarization and extended degradation. Post-mortem PEEM-XANES analysis clearly demonstrated a highly homogeneous mesostructure in the case of the EPD-built TNO/rGO anode vs. a highly segregated and dis-jointed rGO and TNO component clustering in the PVDF-built electrode.

Energy storage and conversion in Li-ion batteries involve dynamic Li storage and transport through a series of electrochemical metastable states (or quasi-equilibrium configuration). Therefore, an investigation of these metastable states is helpful to fully understand the lithium storage mechanism. An accurate understanding of the storage mechanism is a key factor in the design and optimization of the next-generation high-performance batteries. Here, we report the results obtained from electron irradiation-induced phase transitions in Li2FeSiO4 and LiFePO4 by electron microscopy. During prolonged irradiation, the crystalline Li2FeSiO4 particles experienced a transition from a monocrystalline structure to an amorphous phase, with a subsequent recrystallization process (monoclinic to orthorhombic phase). The fine structure of the electron energy loss (ELNES) spectra showed the electron beam-sensitive characteristic of Li2FeSiO4 that included the electron beam-induced mass loss (composition changes), formati...

Engineering of nanostructured lithium iron silicate (LFS) particles is pursued via a novel benign synthesis approach seeking to understand the crystalline particle formation process and its impact on energy storage capacity. Specifically, mesoporous Li2FeSiO4 nanostructured particles are synthesized via a novel dual-step process involving organic-assisted hydrothermal precipitation from concentrated Fe(III) (1 mol/L) aqueous solution followed by reductive (5 vol % H2) thermal transformation of the precipitate at 400 °C (LFS400) and 700 °C (LFS700). Scanning and transmission electron microscopy revealed the formation of secondary sub-micron-sized porous agglomerates of unitary primary nanocrystals (∼50 nm for LFS400 and ∼200 nm for LFS700). Both ethylene glycol and ethylenediamine are used as crystallization control additives. It is demonstrated that formation of LFS from Fe(III) precursor is made possible only by the action of ethylenediamine. The obtained LFS particles are found to be predominantly monoc...

Nanoscale Li 4 Ti 5 O 12 (LTO) is considered a promising anode material for Li-ion batteries because of its outstanding safety. However, cointercalation-induced structural relaxation adversely affects its Li-ion storage properties. Therefore, there is a need to elucidate the connection between electrochemistry and LTO structural relaxation of nano-LTO. Herein, various LTO nanosheet crystals with designated degrees of residual strain were prepared by varying the annealing temperature. The cyclability and rate capability of the prepared 2D LTO nanocrystals were evaluated. During annealing, dehydration of layered lithium titanate hydrate precursors (LTH, (Li 2−x H x )Ti 2 O 5 ·yH 2 O), leads to topotactic transformation from a C -centered orthorhombic to a body-centered orthorhombic system. Dehydrated LTH is then converted into spinel LTO nanosheets. Residual strain induced during transformation causes LTO structure distortion rendering Li-O bonding more covalent. Strongly covalent Li-O bonds screen the Li-Li Coulomb repulsion when 8 a −16 c cointercalation occurs, leading to large irreversible capacity loss and deteriorated cyclability. Meanwhile, rich irreversible Li intercalation degrade the power capability of LTO nanocrystals despite their high surface area. In addition to mechanism elucidation, conditions are identified to eliminate residual strain-induced structural relaxation giving rise to nanosheet anodes with superior power and highly reversible cycling performance.

Lymphangiography can be useful for preoperative planning in chylothorax. Conventional ultrasound-guided intranodal injection can be difficult in some cases and is dependent upon operator skill. Alternative methods have been proposed to simplify the procedure, but their feasibility has not been sufficiently evaluated in clinical cases. The primary purpose of this multicenter, retrospective, descriptive study was to assess the feasibility and describe the clinical findings of CT lymphangiography by intrametatarsal pad injection in dogs with naturally occurring chylothorax. Twenty dogs were analyzed, and enhancement of thoracic ducts (TDs) was successful in 18 (90%) dogs within 5-14 min after initiating the injection, while successful enhancement of the lymphatic vessels cranial to the popliteal lymph nodes was seen in all dogs within 5 min after injection. The dose with good success to achieve TD enhancement was 1 mL/kg (concentration 350 mg I/kg). Only two dogs had mild discomfort after recovery from general anesthesia. Computed tomography lymphangiography by intrametatarsal pad injection is a feasible, easy, and safe procedure, which could provide adequate TD and cisterna chyli enhancement, identify TD number and cisterna chyli location and structure, and contribute to surgical planning.

Integration of solar-energy harvesting and storage functions has attracted significant research attention, as it holds promise for ultimate development of light-chargeable devices. In this context, a functional nanocomposite anode that not only permits electrochemical energy storage through Li-ion photo-intercalation, but also exhibits potential for photoelectrochromic applications, was investigated. The nanocomposite is made of the Li-ion intercalation compound WO

Li2FeSiO4 (LFS) has drawn much attention as cathode for high capacity Li-ion batteries. Even though significant volume of study has been devoted to its crystal chemistry and electrochemistry, many questions relating to its Li-ion storage dynamics remain yet to be fully elucidated. In this context, synchrotron-based X-ray diffraction and absorption spectroscopies are employed to characterize the phase stability and charge compensation mechanism in a metastable Li2FeSiO4 nanostructured cathode as a function of state-of-charge (Li2−xFeSiO4, x = 0, 0.25, 0.50, 0.75, 1.0) and cycling at very low current. The results demonstrate (i) no detectable phase transition from monoclinic to orthorhombic phase during the first charge-discharge cycle but rather formation of antisite defects that progressively induce phase transformation after several electrochemical cycles; (ii) characteristics of solid solution Li-ion storage (Li2−xFeSiO4, x = 0–1); and (iii) the charge compensation for the first Li extraction does not come solely from the ferrous to ferric conversion, but interestingly from prominent participation of lattice oxygen as well that appears to destabilize the cycled LFS structure with significant performance implications.

Orthorhombic lepidocrocite-type lithium titanate hydrates (LTH), as one important member among two-dimensional (2D) materials, have drawn much attention due to their potential applications in nanoelectronics, energy conversion, and energy storage devices. However, only a few efforts have focused on an anisotropic growth mechanism that determines the formation kinetics of LTH and/or even their derivatives. In this context, in situ Raman observation was employed to the isothermal crystallization of LTH nanosheet crystals from amorphous precursor precipitates. During isothermal crystallization, the formation of monolayered LTH nuclei is controlled by oxygen diffusion with an activation energy of 0.72 eV; anisotropic growth along (010) planes induces an interblocking effect among LTH nanosheet crystals, which limits their size up to 50 nm. The nucleation–growth crystallization kinetics of LTH nanosheets were accurately interpreted by the modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, which considered t...

Lithium iron orthosilicate (Li 2 FeSiO 4 ) is an important alternative cathode for next generation Li-ion batteries due to its high theoretical capacity (330 mA h/g). However, its development has faced great challenges arising from significant structural complexity, including the disordered arrangement/orientation of Fe/Si tetrahedra, polytypes and its poorly understood Li storage and transport properties. In this context, ab-initio calculations are employed to investigate the phase stability and Li diffusion profiles of both monoclinic ( P 2 1 ) and orthorhombic ( Pmn 2 1 ) Li 2 FeSiO 4 orthosilicates. The calculations demonstrate that formation of Li Fe antisites can induce a metastability competition between both phases, with neither dominating across nearly the entire discharging profile from Li 2 FeSiO 4 through to LiFeSiO 4 . Furthermore, structural instability is shown to be a serious concern at discharge concentrations below LiFeSiO 4 (1 Li extraction) due to the shared occupation of Li donated electrons with oxygen 2p orbitals – rather than the hypothesized transition to a tetravalent Fe 4+ state. This finding is further supported by diffusion calculations that have determined a high activation energy barrier towards fast charging and rapid phase transitions. In summary, these theoretical results provide critical and timely insight into the structural dynamics of lithium iron orthosilicate, in pursuit of high energy density cathodes.

The reaction between an uncharged Li2FeSiO4 (LFS) cathode and a LiPF6-EC/DMC electrolyte is revealed by in situ XANES in coin cells. This study shows clear evidence of delithiation and iron oxidation in LFS prior to cycling. Subsequent cycling appears to partially restore the original lithiation level, an observation that needs to be taken into consideration in future LFS development work.

Lithium iron silicate has attracted a lot of attention due to its 330 mAh g-1 theoretical capacity (2 Li+ per formula unit). However, inherently it exhibits relatively poor Li-ion intercalation kinetics, interfacial reactivity and complex phase transitions resulting in lower than one Li+ storage and poor capacity retention. In this work, we report a core-shell strategy to overcome these obstacles making use of mechanochemical processing and polymer coating. Mechanochemical annealing has been sown recently [1] to lead to activation of Li-ion diffusion (DLi) by one order of magnitude enhancement. Subsequently, in situ conductive polymer coating was employed on the surface of nanocrystals via an ambient temperature chemical process. As a result of this integrated nanocrystal engineering approach the core-shell LFS@P (βII ) cathode material delivered >1.3 Li and substantially enhanced cycling stability. [1] Rasool, M.; Chiu, H. C.; Lu, X.; Voisard, F.; Gauvin, R.; Jiang, D.; Paolella, A.; Zaghib, K.; Demopoulos, G. P., Mechanochemically-tuned structural annealing: a new pathway to enhancing Li-ion intercalation activity in nanosized βII Li2FeSiO4. J. Mater. Chem. A 2019, 7, 13705-13713

One of the critical issues in Li-ion battery systems is overcoming the inherent poor electronic conductivity of the electrodes and the associated slow electrode/electrolyte interfacial electrochemical kinetics because of the formation of solid electrolyte interphase (SEI). This issue is particularly challenging when high-safety electrode materials like lithium iron phosphate (LiFePO4-LFP) and lithium titanate (Li4Ti5O12-LTO) are employed. Also inevitable material degradation occurs at such interfaces that, for example, was recently discussed in connection to 2D LTO nanocrystals (1) and the spontaneous reaction between Li2FeSiO4 (LFS) and LiPF6-based electrolyte (2). Michel Armand’s pioneering work (3) on carbon coating provides an elegant and economic strategy to overcome aforementioned issues, leading to their successful commercialization by Hydro-Québec. With the advent of different nanocrystals as active electrode materials for high energy or power applications new opportunities arise for innovative engineering the electrode/electrolyte interfaces at the nanoscale. Herein two modification processes are tailored to fabrication of 2D nano-Li4Ti5O12 as anodes and to mechanochemically-nanosized orthorhombic Li2FeSiO4 (Pmn21 LFS) as cathodes. With the goal on one hand replacing the expensive NMP-PVDF coating process and on the other hand tackling the low nominal capacity issue of LTO electrodes, we are working on an alternative sustainable fabrication method involving in situ coating of reduced graphene oxide (redGO) onto 2D nano-LTO. This process involves electrophoretic co-deposition of hydrated lithium titanate (Li2−xHx)Ti2O5·yH2O) and GO that is followed by controlled thermal conversion into redGO-LTO composite anodes. Meanwhile, the exploration of Pmn21 Li2FeSiO4 as high-capacity cathode has been impeded because of lacking suitable surface modification techniques. Traditional carbon coating at elevated temperature is not suitable here as it would induce a phase transformation of LFS from orthorhombic Pmn21 into monoclinic P21/n. Therefore, in another development we have successfully coated Pmn21 LFS with a conductive polymer via in situ polymerization at room temperature. In developing this method we discovered significant differences between LFP and LFS as substrates reflecting differences in surface redox reactivity between the orthophosphate and orthosilicate polyanionic frameworks. Thanks to this low-T non-C coating method the nanometric Pmn21 LFS cathode reveals itself as very promising high-energy density and stable cathode material. H. C. Chiu, X. Lu, J. Zhou, L. Gu, J. Reid, R. Gauvin, K. Zaghib and G. P. Demopoulos, Adv. Energy Mater., 7, 1601825 (2017). Z. Arthur, H. C. Chiu, X. Lu, N. Chen, V. Emond, K. Zaghib, D. T. Jiang and G. P. Demopoulos, ChemCommun, 52, 190 (2016). M. Armand et al., Method for synthesis of carbon-coated redox materials with controlled size, US Patent No. 2004/0033360A1, Feb. 19, 2004.

It is well known that the structural modification of carbon nanotubes (CNT) with heteroatoms, could modify their physical and chemical properties. These modifications open the possibilities to improve the electrochemical performance of CNT thus enhancing their application in batteries for storage of lithium ions. However, to achieve such characteristics it is important to control its structure, morphology and chemical composition during synthesis. In this work, the CNT were modified in situ by the intercalation of silicon (CNT-Si) in the graphitic carbon network to be used as an anode electrode in lithium ion battery. CNT-Si were synthesized by a modified chemical vapor deposition; toluene, ferrocene and triphenylsilane were used as carbon source, metal catalyst and silicon precursor, respectively. The effect of doping and temperature was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X ray photoelectron spectroscopy (XPS). The microscopy results showed that the CNT-Si were structurally modified with various forms of roughness, distortions and defects not only in the inner walls but also on outer walls. The elevated synthesis temperature had the most significant effect in the graphitic carbon network. According to the Raman scattering, the CNT-Si presented greater structural disorder due to the integration of silicon atoms in the carbon, which increased the disorder in hexagonal network. Elemental analysis composition by XPS indicated that the silicon was intercalated preferably at a higher temperature with a concentration of 0.76±10 at. %, clearly showing that silicon was successfully linked in the carbon network as Si-C. In order to examine the electrochemical properties of the materials, CNT-Si were used as an anode electrode for galvanostatic charge and discharge tests, as well as for cyclic votammetry curves. The results highlighted that temperature played a very important role on the electrocatalytic characteristics of materials and the insertion of the silicon in the carbon structure provided more sites for the diffusion and storage of lithium. The processes of alloying and de-alloying lithium in the CNT-Si matrix, charge and discharge capacity, as well as its cyclic performance will be discussed.

Nanostructured lithium metal orthosilicate materials hold a lot of promise as next generation cathodes but their full potential realization is hampered by complex crystal and electrochemical behavior. In this work Li2FeSiO4 crystals are synthesized using organic-assisted precipitation method. By varying the annealing temperature different structures are obtained, namely the monoclinic phase at 400°C, the orthorhombic phase at 900°C and a mixed phase at 700°C. The three Li2FeSiO4 crystal phases exhibit totally different charge/discharge profiles upon delithiation/lithiation. Thus the 400°C monoclinic nanocrystals exhibit initially one Li extraction via typical solid solution reaction, while the 900°C orthorhombic crystals are characterized by unacceptably high cell polarization. In the meantime the mixed phase Li2FeSiO4 crystals reveal a mixed cycling profile. We have found that the monoclinic nanocrystals undergo phase transition to orthorhombic structure resulting in significant progressive deterioration of the material's Li storage capability. By contrast, we discovered when the monoclinic nanocrystals are cycled initially at higher rate (C/20) and subsequently subjected to low rate (C/50) cycling the material's intercalation performance is stabilized. The discovered rate-dependent electrochemically-induced phase transition and stabilization of lithium metal silicate structure provides a novel and potentially rewarding avenue towards the development of high capacity Li-ion cathodes.

Identifying the structure of electrodes at atomic-scale remains a key challenge but is a fertile realm for groundbreaking fundamental research in the advanced Li-ion battery material field. In this context, the subtle structure evolution taking place during lithiation/delithiation in the bulk/surface of Li(4)Ti(5)O(12) spinel (LTO) was probed using scanning transmission electron microscopy and found to undergo significant structure torque, namely Ti-O bond stretching/shrinking at different state-of-charge (SOC), which is not identified previously. This kind of nanostructure change plays an important role in facilitating the formation of capturing centers for the electron/hole pairs in a 3.80 eV insulating material as is LTO. Furthermore, with the aid of electron energy loss spectroscopy, the spontaneous charge transfer process, Ti(3+) ↔ e(-) + Ti(4+), was confirmed in the fully lithiated Li(7)Ti(5)O(12) surface as an essential step of the gas-releasing phenomenon. This new insight paves the way toward deeper comprehension and ultimately control of the electrochemical process for this and other important Li-ion battery materials.

Zero-strain and long-term stability of nanoscale lithium titanate (LTO) anode materials make possible the fabrication of exceptionally stable lithium ion batteries. But one issue must be considered that of nanostructure-induced relaxation in 2D LTO nanosheets which profoundly modifies their Li storage properties and structural stability. Excessively intercalated Li ions at both 8a and 16c sites trigger nucleation of the relaxed LTO structure in the near-surface region, which impedes Li-ion diffusion and causes the increasing polarization of LTO nanosheet electrodes. Nuclei of relaxed LTO then undergo isotropic growth along the 3D Li-ion pathways in LTO to completely convert near-surface regions into relaxed LTO. With increasing population of trapped Li ions, the enhanced conductivity due to Ti4+/Ti3+ reduction gradually eliminates the raised polarization. In the meantime, spontaneous electrolyte/LTO reduction to form the solid electrolyte interphase starts playing a major role in capacity loss once the transformation of near-surface region into relaxed LTO becomes saturated. Elucidation of these fundamental intercalation-induced surface structure transformations contribute greatly into the design of highly performing 2D nanoscaled LTO and other electrode materials.

Lithium metal orthosilicate cathode materials (Li2(Fe,Mn)SiO4 denoted as LMS) have been the subject of significant research interest for the past 10 years because of the high theoretical capacity nearly two times higher than that of the analogous polyanion cathode LiFePO4 (165 mAh/g), if the two lithium ions could be fully extracted and re-inserted in multiple charge/discharge cycles. Despite significant progress, a series of critical issues-questions relating to this strategically important family of cathode materials remain open hampering their full development. One such critical issue is the mechanism of Li ion storage namely, solid-solution behavior (single-phase) vs. two-phase reaction. In analogy with the well understood two-phase separation Li storage mechanism of LiFePO4 cathode the dominant view among those investigating the orthosilicate system is that we have also a two-phase mechanism between monoclinic (P21/n) Li2FeIISiO4 and orthorhombic (Pmn21) one-Li delithiated LiFeIIISiO4. However, in many of these studies the generated discharge curves are not flat but are slanted. Such behavior has been attributed to polarization effects without further characterization leaving an important gap in our understanding. With the view of clarifying this issue we have conducted first principle calculations (1) and in situ (unpublished) and ex situ (submitted) synchrotron XRD and XANES (Fe K-edge and L-edge; Si K-edge and Oxygen K-edge) characterizations of nanostructured LFS cathode in terms of structure evolution and charge compensation at different states of charge (Li(2-x)FeSiO4, x=0, 0.25, 0.50, 0.75, 1.0). This is done by charging/discharging LFS at low current (C/50) to allow for structure relaxation hence unequivocal (quasi-equilibrium condition) probing of the Li storage mechanism: solid solution vs. two-phase reaction. Furthermore, cycling is not limited to the first cycle but is extended to several cycles. For the study we employ a mixed phase (monoclinic/orthorhombic) nanograined Li2FeSiO4 material synthesized via organic-assisted hydrothermal precipitation and annealing at 400 °C (2,3). The data clearly point out towards solid solution mechanism- a finding that should bring new perspective in our pursuit of unlocking the full capacity advantage of the orthosilicate Li-ion host structure. Acknowledgments This work is supported through a Hydro-Québec/Natural Sciences & Engineering Research Council of Canada (NSERC) Collaborative R&D research grant. DTJ acknowledges NSERC support for the work done at the University of Guelph. Synchrotron radiation measurements were performed at the Canadian Light Source, which is supported by CFI, NSERC, University of Saskatchewan, Province of Saskatchewan, Western Economic Diversification Canada, NRC Canada, and CIHR. References 1. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G., Density functional theory insights into the structural stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes, Journal of Power Sources, 2016, 318, 136-145. 2. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Scientific Reports, 2015, 5, 8599. 3. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte, ChemComm, 52 (2015) 190-193.

Orthosilicates, Li2 M SiO4, where M = Fe, Mn, Co, Ni, are characterized by a theoretical specific capacity that is twice that of LiFePO4, namely 340 vs. 170 mAh/g. In this presentation, we have probed the structural evolution and charge compensation of Li2FeSiO4 cathode using both in-situ/postmortem synchrotron XRD/XANES and first-principle calculations1-3. The results demonstrate that the formation of Li-Fe antisite defects play a key role in destabilizing the Li2FeSiO4 structure and “catalyzing” the monoclinic-to-orthorhombic transition. Then the charge compensation for the first Li extraction does not come solely from the ferrous to ferric conversion due to the strong electron correlation of Fe 3d orbitals, but interestingly from prominent participation of lattice oxygen as well that appears to destabilize the cycled structure. Using scanning transmission X-ray microscopy, it is revealed that the electrochemical lithiation/delithiation of Li2FeSiO4 electrode does not proceed uniformly but it exhibits an unusual solid solution pattern4 with the stored Li content varying locally possibly arising from a combination of inherent LFS material and electrode properties like poor conductivities, variable particle size/distribution and extent of electrolyte penetration. All these findings should have a thought-provoking influence on the study of the material itself and the broader Li-ion battery research community as well. References 1. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals. Sci Rep-Uk 2015, 5, 8599. 2. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte Chem Commun 2015, accpeted, DOI: 10.1039/C5CC07197F. 3. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G. Density functional theory insight into the structure stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes. J Power Sources 2015, In revision. 4. Lu, X.; Chiu, H.-C.; Arthur, Z.; Zhou, J. G.; Wang, J.; Chen, N.; Jiang, D.-T.; Zaghib, K.; Demopoulos, G. P. Quasi-equilibrium Li storage in metastable Li2FeSiO4 cathode. 2015, Under review.

Lithium transition metal silicates Li2 M SiO4 ( M = Fe, Mn, Co, etc.) have been under intense research due to their double theoretical capacity of 330 mAh/g compared to LiFePO4 (170 mAh/g)1,2,3 . Their development as cathode materials however has been hampered due in part of their rich polymorphism and phase transitions occurring during cycling not allowing full capacity storage and reversible retention. In this work we focus on the electrochemistry of lithium iron silicate (LFS) 5-8. Almost all previous studies have focused solely on the electrochemistry of the high temperature monoclinic phase (m-LFS). According to these studies4,5,8, the monoclinic phase undergoes electrochemically-induced phase transition during cycling to thermodynamically stable low-temperature orthorhombic phase (o-LFS). This prompted us to take a deep look into the structural and electrochemical behavior of the latter phase as it might hold the key in designing high performance lithium iron orthosilicate cathodes. During this investigation we discovered that upon galvanostatic cycling, the specific capacity of an o-LFS/C nanocomposite cathode exhibited gradual increase from 40 to 165 mAh/g and a shift in Li-storage mechanism from solid solution to biphasic type. This intriguing behavior is currently the subject of further characterizations to elucidate the underlying phenomena that can have significant implications to the development of high energy density LIB cathode materials. References Islam, M.S., et al., Silicate cathodes for lithium batteries: alternatives to phosphates? Journal of Materials Chemistry, 2011. 21(27): p. 9811-9818. Zaghib, K., et al., Review and analysis of nanostructured olivine-based lithium recheargeable batteries: Status and trends. Journal of Power Sources, 2013. 232: p. 357-369. Ferrari, S., et al., Electrochemistry of orthosilicate-based lithium battery cathodes: a perspective. Physical Chemistry Chemical Physics, 2014. 16(22): p. 10353-10366. Masese, T., et al., Relationship between Phase Transition Involving Cationic Exchange and Charge–Discharge Rate in Li2FeSiO4. Chemistry of Materials, 2014. 26(3): p. 1380-1384. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals. Sci Rep-UK 2015, 5, 8599. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte Chem Commun 2016, 52, 190-193. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G. Density functional theory insight into the structure stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes. J Power Sources 2016, In revision. Lu, X.; Chiu, H.-C.; Arthur, Z.; Zhou, J. G.; Wang, J.; Chen, N.; Jiang, D.-T.; Zaghib, K.; Demopoulos, G. P. Quasi-equilibrium Li storage in metastable Li2FeSiO4 cathode. 2016, Under review.

Spinel lithium titanate Li4Ti5O12 (LTO) has been one of the most prominent electrode materials that are able to exhibit extremely long-term stability1 because of its negligible volume change (0.2%)2 during Li insertion / extraction. During Li insertion, external Li ions enter into the empty octahedral 16c sites in spinel structure, while in the meantime self-diffusion of originally existing Li+ at 8a sites occurs towards the neighboring 16c sites3 to form the rock-salt structure. As a result of this behavior the two-phase partially lithiated LTO, Li4+x Ti5O12 exhibits a very flat voltage plateau around 1.55 V vs. Li/Li+ over a wide range of Li content (e.g., 0.09 < x < 2.91). Of the two phases3,4, one is insulator Li4Ti5O12 (10-9 S/cm) and the other is conductor Li7Ti5O12 (8 S/cm) 5. Besides these intrinsic physicochemical properties of LTO, its nanosizing to enhance its power capability can influence its Li storage properties; e.g., the orientation-dependent 8a – 16c co-intercalation in the near surface region of LTO nanoparticles results in considerable irreversible capacity loss due the formation of overlithiated phase. Furthermore the high surface area of LTO nanoparticles leads to higher reactivity with the electrolyte aggravating the notorious gas generation issue, which may be accompanied structural relaxation in the near surface region6-11. Thanks to many efforts devoting to the size-effect on LTO for the last decade, the mystery of the size-effect mechanism has been largely revealed even though there are still several unanswered questions. One of these is the formation kinetics of the overlithiated phase near surface region, which is particularly critical from an industrial perspective as it can lead to optimized formation protocols and electrolyte recipes for LTO batteries. In this context, the universal Johnson-Mehl-Avrami-Kolmogorov (JMAK) kinetic model was employed to elucidate the correlation between overlithiated phase growth and the resistivity variation of LTO electrodes during standard galvanostatic charge / discharge cycle tests at room temperature. Based on this theoretical model, 8a-16c co-intercalated overlithated phase isotropically grows along the 3D Li diffusion pathway in the spinel framework, until the transition from 8a / 16c occupancy to 8a – 16c co-occupancy gets saturated in the near surface region. (1) Zaghib, K.; Simoneau, M.; Armand, M.; Gauthier, M. J Power Sources 1999, 81, 300. (2) Sun, Y.; Zhao, L.; Pan, H. L.; Lu, X.; Gu, L.; Hu, Y. S.; Li, H.; Armand, M.; Ikuhara, Y.; Chen, L. Q.; Huang, X. J. Nat Commun 2013, 4, 1870. (3) Wagemaker, M.; Simon, D. R.; Kelder, E. M.; Schoonman, J.; Ringpfeil, C.; Haake, U.; Lützenkirchen-Hecht, D.; Frahm, R.; Mulder, F. M. Advanced Materials 2006, 18, 3169. (4) Colbow, K. M.; Dahn, J. R.; Haering, R. R. J Power Sources 1989, 26, 397. (5) Young, D.; Ransil, A.; Amin, R.; Li, Z.; Chiang, Y.-M. Advanced Energy Materials 2013, 3, 1125. (6) Belharouak, I.; Koenig, G. M.; Tan, T.; Yumoto, H.; Ota, N.; Amine, K. J Electrochem Soc 2012, 159, A1165. (7) He, Y.-B.; Li, B.; Liu, M.; Zhang, C.; Lv, W.; Yang, C.; Li, J.; Du, H.; Zhang, B.; Yang, Q.-H.; Kim, J.-K.; Kang, F. Sci. Rep. 2012, 2. (8) He, Y.-B.; Liu, M.; Huang, Z.-D.; Zhang, B.; Yu, Y.; Li, B.; Kang, F.; Kim, J.-K. J Power Sources 2013, 239, 269. (9) Wu, K.; Yang, J.; Liu, Y.; Zhang, Y.; Wang, C.; Xu, J.; Ning, F.; Wang, D. J Power Sources 2013, 237, 285. (10) Bernhard, R.; Meini, S.; Gasteiger, H. A. J Electrochem Soc 2014, 161, A497. (11) He, M.; Castel, E.; Laumann, A.; Nuspl, G.; Novák, P.; Berg, E. J. J Electrochem Soc 2015, 162, A870.

In situ synchrotron radiation XANES and XRD have been carried out on Li2FeSiO4 cathode material in a lithium-ion-battery (LIB) cell. The evolution of the long range lattice structure and the local iron oxidation state has been observed at a charging rate of C/20 for the formation cycle for one Lithium extraction; additional ex situ measurements of the pristine cathode material were taken for comparison. The observed spontaneous interaction between the cathode and the fluorinated electrolyte and the impact of subsequent cycling are discussed.

Li-ion batteries (LIBs) have already made tremendous progress supplying power for multiple devices used in our daily life. Now LIBs are gradually entering the plug-hybrid and fully electric vehicles. Safety and high specific capacity enabling long range driving between charges are among industry’s priorities in this domain. One cathode material group that potentially can provide solutions to these priorities is lithium metal silicates. Orthosilicates, Li2 M SiO4, where M = Fe, Mn, Co, Ni, are characterized by a theoretical specific capacity that is twice that of LiFePO4, namely 340 vs. 170 mAh/g1 ,2. In this presentation, we report on the synthesis and electrochemical/structural evaluation of different phase (monoclinic and orthorhombic) Li2(Fe,Mn)SiO4 materials using a combination of organic-assisted hydrothermal and reducing annealing treatment steps. During the electrochemical process, we find that the Li2FeSiO4 cathode demonstrates rate- and phase- dependent capacity changes upon lithiation/delithiation3. We have probed these changes by conducting both in-situ/postmortem synchrotron XRD/XANES and first-principle calculations of the structure/phase stabilities and Li ion diffusion properties of monoclinic Li2FeSiO4 orthosilicate. It is revealed that formation of Li-Fe antisite defects play a key role in destabilizing the orthosilicate structure and “catalyzing” the monoclinic-to-orthorhombic transition. Furthermore the charge compensation mechanism that is essential in achieving more than one Li extraction is discussed accordingly as well as the Li-ion diffusion properties are analyzed. The rich insight obtained from these Li2FeSiO4 studies is invaluable as we move towards the design and testing of stable orthosilicate structures with fully reversible 2-Li intercalation capacity for high-energy next generation LIB cathodes. References 1. A., Nyten; A., Abouimrane; M., Armand; T., Gustafsson & J. O., Thomas, Electrochemical performance of Li2FeSiO4 as a new Li-battery cathode material. Electrochem. Commun. 7, 156-160, (2005). 2. M. Saiful Islam et al., Silicate cathodes for lithium batteries: alternatives to phosphates? J. Mater. Chem., 2011, 21, 9811. 3. Xia Lu; Huijing Wei; Hsien-Chieh Chiu; Raynald Gauvin; Pierre Hovington; Abdelbast Guerfi; Karim Zaghib and George P. Demopoulos, Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Sci. Rep. 5 (2015) 8599.

Due to the emerging needs of electrical and hybrid electrical vehicle applications, more research effort has been directed towards the next generation Li-ion storage materials, especially on high-capacity cathode materials. In this context, lithium transition metal silicates Li2 M SiO4 ( M = Fe, Mn, Co, etc.) 1-5 are drawing increasingly more attention thanks to their high theoretical capacity due to the two lithium-ion extraction per formula unit. However lack of phase purity control during synthesis and phase transition reactions during delithiation/lithiation have imposed obstacles to their study and further development. Hereby, we investigate a novel dual step organic-assisted hydrothermal-annealing approach to obtain different lithium iron silicate polymorphs (monoclinic, orthorhombic, and mixed) for subsequent electrochemical evaluation and probing of their phase transition behavior. During the hydrothermal synthesis step, organic additives are used to control nanocrystal growth, which upon annealing lead to in-situ coating with nitrogen-doped carbon. The silicates are characterized by various techniques including XRD, FE-SEM, TEM, XPS, Raman spectroscopy, and XANES and demonstrate different structures and morphologies with various synthesis conditions, including annealing temperature, pH etc., which critically impact on their electrochemical properties. References 1. Nyten, A., Abouimrane, A., Armand, M., Gustafsson, T. & Thomas, J. O. Electrochemical performance of Li2FeSiO4 as a new Li-battery cathode material. Electrochem Commun 7, 156-160, (2005). 2. Nishimura, S. I. et al. Structure of Li2FeSiO4. J Am Chem Soc 130, 13212-13213, (2008). 3.Boulineau, A. et al. Polymorphism and structural defects in Li2FeSiO4. Dalton Trans 39, 6310-6316, (2010). 4. Eames, C., Armstrong, A. R., Bruce, P. G. & Islam, M. S. Insights into Changes in Voltage and Structure of Li2FeSiO4 Polymorphs for Lithium-Ion Batteries. Chem Mater 24, 2155-2161, (2012) 5. R.J. Gummow, Y. He / Journal of Power Sources 253 (2014) 315-331, Recent progress in the development of Li2MnSiO4 cathode materials

Mesoporous Li deficient Li4Ti5O12 nanosheets with major [110] preferred orientation were prepared by a novel low T (+ reaches the following over-stoichiometrical composition: Li7.92Ti5O12. As determined by XANES the excess Li-ion storage is the result of preferential crystal orientation along the (110) and (111), facets. During lithiation, it was further determined the charge compensation to occur primarily by oxygen, rather than by titanium. Finally, both the oxygen and titanium in the near surface region exhibit different electronic structure from bulk. Those results point to the importance of surface reconstruction and relaxation in accommodating excess Li storage. As a consequence, the newly prepared Li4Ti5O12 nanosheets exhibit superior Li-ion storage performance exceeding by far most of the alternatively prepared LTO anode materials.

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