Li ion Batteries

High energy and high power electrochemical energy storage devices rely on different fundamental working principles - bulk vs. surface ion diffusion and electron conduction. Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. Here, we provide a solution to this longstanding issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4). The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. Moreover, PTMA is part of the active material in the electrode contributing as well to the stored charge. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO4 by an internal charge transfer process. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. As a result of hybrid’s components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents.

ZnSb nanotubes were grown through a template free electrodeposition method under over-potential conditions. The growth of the nanotubes was attributed to the template effect from H2 bubbles. Due to their hollow structure, the ZnSb nanotubes depicted better Li ion storage performance compared to that of ZnSb nanoparticles deposited under different conditions.

Fluoride shuttle batteries (FSBs) are superior to lithium-ion batteries (LIBs) in terms of high energy density, safety, etc. An electrolyte consisting of tetraglyme (G4) as a solvent molecule and triphenylboroxine (TPhBX) as an anion acceptor to improve the solubility of cesium fluoride (CsF) salt is a candidate of the electrolytes for FSBs. The low concentration of CsF in the electrolyte makes it difficult to study. Electrical X-Ray total scattering and anomalous X-Ray scattering (AXS) are powerful techniques for studying the local structures of electrolytes. This study shows that AXS measurement with a Cs K-edge can clarify the local structure around very low atomic concentration (0.27 at%) Cs. The first-neighbor distance and the coordination number suggest that Csþ ions exist in the major
Cs(G4)2 þ complex together with the minor Cs(G4)þ. The low-Q peak observed in the scattering patterns can be attributed to the structure of alternating [TPhBX]F and [Cs(G4)]þ (or [Cs(G4)2]þ). The large sizes of cations ([Cs(G4)]þ and [Cs(G4)2] þ) and anion [TPhBX]F lead to a long correlation distance. This work presents the picture that the F ions hop from TPhBX to [Cs(G4)]þ or [Cs(G4)2]þ toward the cathode and anode during charge and discharge, respectively.

We performed first-principle calculations based on density functional theory (DFT) to investigate adsorption of lithium (Li) on graphene with divacancy and Stone–Wales defects. Our results confirm that lithiation is not possible in pristine graphene. However, enhanced Li adsorption is observed on defective graphene because of the increased charge transfer between adatom and underlying defective sheet. Because of increased adsorption, the specific capacity is also increased with the increase in defect densities. For the maximum possible divacancy defect density, Li storage capacities of up to ∼1675 mAh/g can be achieved. While for Stone–Wales defects, we find that a maximum capacity of up to ∼1100 mAh/g is possible. Our results provide deeper understanding of Li-defect interactions and will help to create better high-capacity anode materials for Li-ion batteries.

Surface passivation of silicon anodes is an appealing design strategy for the development of reliable, high capacity lithium-ion batteries. However, the structural stability of the coating layer and its influence on the lithiation process remain largely unclear. Herein, we show that surface coating mediates the swelling dynamics and the fracture pattern during initial lithiation of crystalline silicon nanopillars. We choose conformally nickel coated silicon architectures as a model system. Experimental findings are interpreted based on a chemo-mechanical model. Markedly different swelling and fracture regimes have been identified, depending on the coating thickness and silicon nanopillar diameter. Nanopillars with relatively thin coating display anisotropic swelling similar to pristine nanopillars, but with different preferred fracture sites. As the coating thickness increases, the mechanisms become isotropic, with one randomly oriented longitudinal crack that unzips the core-shell structure. The morphology of cracked pillars resembles that of thin-film electrode on a substrate, which is more amenable to cyclic lithiation without fracture. The knowledge provided here helps understanding the cycling results in coated nano-silicon electrodes and further suggests design rules for better performance electrodes through proper control of the lithiation and fracture.

Graphene-decorated single crystalline V2O5 nanowires (G–VONs) have been synthesized by mixing graphene oxide (GO) and V2O5 suspensions at room temperature. In this process, V2O5 nanowires (VONs) are formed spontaneously from commercial V2O5 particles with the aid of GO. The as-formed one dimensional G–VONs were characterized by using a X-ray diffractometer, a X-ray photoelectron spectrometer, a scanning electron microscope, and a transmission electron microscope. GO plays a vital role in the VON formation with the simultaneous reduction of GO. A single G–VON showed superior electrical conductivity compared with that of the pure VONs obtained from the sol–gel method. This could be ascribed to the insertion of rGO sheets into the V2O5 layered structure, which was further confirmed by electron energy loss spectroscopy.

The increasing demands from micro-power applications call for the development of the electrode materials for Li-ion microbatteries using thin-film technology. Porous Olivine-type LiFePO4 (LFP) and NASICON-type Li3Fe2(PO4)3 have been successfully fabricated by radio frequency (RF) sputtering and post-annealing treatments of LFP thin films. The microstructures of the LFP films were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performances of the LFP films were evaluated by cyclic voltammetry and galvanostatic charge-discharge measurements. The deposited and annealed thin film electrodes were tested as cathodes for Li-ion microbatteries. It was found that the electrochemical performance of the deposited films depends strongly on the annealing temperature. The films annealed at 500 °C showed an operating voltage of the porous LFP film about 3.45 V vs. Li/Li+ with an areal capacity of 17.9 µAh cm−2 µm−1 at C/5 rate after 100 cycles. Porous NASICON-type Li3Fe2(PO4)3 obtained after annealing at 700 °C delivers the most stable capacity of 22.1 µAh cm−2 µm−1 over 100 cycles at C/5 rate, with an operating voltage of 2.8 V vs. Li/Li+. The post-annealing treatment of sputtered LFP at 700 °C showed a drastic increase in the electrochemical reactivity of the thin film cathodes vs. Li+, leading to areal capacity ~9 times higher than as-deposited film (~27 vs. ~3 µAh cm−2 µm−1) at C/10 rate.

Surface passivation of silicon anodes is an appealing design strategy for the development of reliable, high-capacity lithium-ion batteries. However, the structural stability of the coating layer and its influence on the lithiation process remain largely unclear. Herein, we show that surface coating mediates the swelling dynamics and the fracture pattern during initial lithiation of crystalline silicon nanopillars. We choose conformally nickel coated silicon architectures as a model system. Experimental findings are interpreted based on a chemomechanical model. Markedly different swelling and fracture regimes have been identified, depending on the coating thickness and silicon nanopillar diameter. Nanopillars with relatively thin coating display anisotropic swelling similar to pristine nanopillars, but with different preferred fracture sites. As the coating thickness increases, the mechanisms become isotropic, with one randomly oriented longitudinal crack that unzips the core-shell s...

Abstract This paper describes a set of experimental tests carried out to better understand the thermal behavior of Lithium-ion batteries under load and the capability of various cooling fluids in maintaining the working conditions within a safe range for the cells. Despite several theoretical models are available in the literature, very few experimental data are reported. Different types of cells have been analyzed. The generation of hot spots has sometimes been registered, their occurrence being independent of cell geometry and size; instead, the battery's history and age, appeared the main factors in determining the onset of hot spots on the surface of the cell. Two experimental rigs have been set up to test the capability of different cooling fluids in removing the surplus heat generated in a Li-ion battery module, where the cells of interest have been replaced with electrically heated elements with the same thermal characteristics of the cells. It was thus possible to safely investigate “extreme” operating conditions, where the occurrence of a thermal runaway is possible. Among the tested fluids, air was unable to adequately limit the surface temperature increase, while a perfluorinated polyether, allowed to work within the optimal temperature range, even under severe operating conditions.

Carbon nanotubes (CNT) are used as anodes for flexible Li-ion micro-batteries. However, one of the major challenges in the growth of flexible micro-batteries with CNT as the anode is their immense capacity loss and a very low initial coulombic efficiency. In this study, we report the use of a facile direct pre-lithiation to suppress high irreversible capacity of the CNT electrodes in the first cycles. Pre-lithiated polymer-coated CNT anodes displayed good rate capabilities, studied up to 30 C and delivered high capacities of 850 mAh g−1 (313 μAh cm−2) at 1 C rate over 50 charge-discharge cycles.

"""The paper investigates the potential of using lumped stationary battery energy storage systems (BESS) in the public low-voltage distribution grid in order to defer upgrades needed in case of large penetration of electric vehicle (EV), electrified heat pump (HP) in presence of photovoltaic (PV) panel on the view of techno economic optimal sizing taking the consideration of season-based diurnal dynamics. The BESS is primarily dimensioned for the peak shaving operation targeted for the counterbalance of overloading of transformer; BESS also participates in arbitrage (buy low, sell high) application. The paper assesses the effects of a PV-BESS combination and the control of such a system with the help of a newly devised season specific BESS control protocol that ensures the availability of energy for peak-shaving purpose (namely peak period in winter) and it participates in arbitrage. The objective of this paper is to develop and detail the method of optimum sizing energy storage for grid connected distribution systems using newly devised BESS control protocol and investigate its sensitivity to factors which are known to influence energy system performance and hence storage requirements. The results provide insight into the dimensioning and the required specification and configuration of BESS.
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