RESUMEN
The substitution of an organic liquid electrolyte with lithium-conducting solid materials is a promising approach to overcome the limitations associated with conventional lithium-ion batteries. These constraints include a reduced electrochemical stability window, high toxicity, flammability, and the formation of lithium dendrites. In this way, all-solid-state batteries present themselves as ideal candidates for improving energy density, environmental friendliness, and safety. In particular, all-solid-state configurations allow the introduction of compact, lightweight, high-energy-density batteries, suitable for low-power applications, known as thin-film batteries. Moreover, solid electrolytes typically offer wide electrochemical stability windows, enabling the integration of high-voltage cathodes and permitting the fabrication of higher-energy-density batteries. A high-voltage, all-solid-state lithium-ion thin-film battery composed of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a lithium metal anode has been deposited layer by layer on low-cost stainless-steel current collector substrates. The structural and electrochemical properties of each electroactive component of the battery had been analyzed separately prior to the full cell implementation. In addition to a study of the internal solid-solid interface, comparing them was done with two similar cells assembled using conventional lithium foil, one with thin-film solid electrolyte and another one with thin-film solid electrolyte plus a droplet of LP30 liquid electrolyte. The thin-film all-solid state cell developed in this work delivered 80.5 mAh g-1 in the first cycle at C/20 and after a C-rate test of 25 cycles at C/10, C/5, C/2, and 1C and stabilized its capacity at around 70 mAh g-1 for another 12 cycles prior to the start of its degradation. This cell reached gravimetric and volumetric energy densities of 333 Wh kg-1 and 1,212 Wh l-1, respectively. Overall, this cell showed a better performance than its counterparts assembled with Li foil, highlighting the importance of the battery interface control.
RESUMEN
Cobalt-free spinel LiNi0.5Mn1.5O4 is one of the most promising and environmentally friendly cathodes, based on its high specific theoretical capacity (147 mAh·g-1) and high electrochemical potential (4.7 V vs Li+/Li), as well as good electronic and Li-ion conductivities. In this work, we present the fabrication of LiNi0.5Mn1.5O4 thin-film cathodes deposited by the industrially scalable AC magnetron sputtering technique on functional and cost-effective stainless steel current collectors. This is the first step toward battery downscaling, envisioning the fabrication of compact microbatteries for low-power energy supply. The thin-film strategy is crucial also for solid electrolyte fabrication that will allow the integration of high-energy-density batteries while overcoming most of the current battery challenges. In this work, the effect of film thickness on the material's electrochemical performance is discussed, correlating the observed structural and morphological evolution with the final electrochemical response. Moreover, the effect of iron diffusion from the current collector substrate into the cathode film is analyzed. The addition of a stable CrN barrier layer in between the substrate and the film is proposed to prevent Fe diffusion, with a direct positive influence on the electrochemical behavior. All in all, the obtained results will facilitate the practical implementation of LiNi0.5Mn1.5O4 thin films as high-voltage cathodes in functional cost-effective microbatteries.
RESUMEN
Introducing a small dose of an electrolyte additive into solid polymer electrolytes (SPEs) is an appealing strategy for improving the quality of the solid-electrolyte-interphase (SEI) layer formed on the lithium metal (Li°) anode, thereby extending the cycling life of solid-state lithium metal batteries (SSLMBs). In this work, we report a new type of SPEs comprising a low-cost, fluorine-free salt, lithium tricyanomethanide, as the main conducting salt and a fluorinated salt, lithium bis(fluorosulfonyl)imide (LiFSI), as the electrolyte additive for enhancing the performance of SPE-based SSLMBs. Our results demonstrate that a homogeneous and stable SEI layer is readily formed on the surface of the Li° electrode through the preferential reductive decomposition of LiFSI, and consequently, the cycle stabilities of Li°||Li° and Li°||LiFePO4 cells are significantly improved after the incorporation of LiFSI as an additive. The intriguing chemistry of the salt anion revealed in this work may expedite the large-scale implementation of SSLMBs in the near future.
RESUMEN
Interface-dominated materials such as nanocrystalline thin films have emerged as an enthralling class of materials able to engineer functional properties of transition metal oxides widely used in energy and information technologies. In particular, it has been proven that strain-induced defects in grain boundaries of manganites deeply impact their functional properties by boosting their oxygen mass transport while abating their electronic and magnetic order. In this work, the origin of these dramatic changes is correlated for the first time with strong modifications of the anionic and cationic composition in the vicinity of strained grain boundary regions. We are also able to alter the grain boundary composition by tuning the overall cationic content in the films, which represents a new and powerful tool, beyond the classical space charge layer effect, for engineering electronic and mass transport properties of metal oxide thin films useful for a collection of relevant solid-state devices.
RESUMEN
In the goal of a sustainable energy future, either the energy efficiency of renewable energy sources is increased, day-to-day energy consumption by smart electronic feedback loops is managed in a more efficient way, or contribution to atmospheric CO2 is reduced. By defining a next generation of fast-response electrochemical CO2 sensors and materials, one can contribute to local monitoring of CO2 flows from industrial plants and processes, for energy management and building control or to track climate alterations. Electrochemical Li+ -garnet-based sensors with Li7 La3 Zr2 O12 solid electrolytes can reach notable 1 min response time at lowered operation temperatures to track 400-4000 ppm levels of CO2 when compared with state-of-the-art NASICON-based sensors. By using principles of redefining the electrode electrochemistry, it is demonstrated that Li6.75 La3 Zr1.75 Ta0.25 O12 can be used to alter its classic use as energy-storage function to gain additional functions such as CO2 tracking.
RESUMEN
Ion transport in solid-state devices is of great interest for current and future energy and information technologies. A superior enhancement of several orders of magnitude of the oxygen diffusivity has been recently reported for grain boundaries in lanthanum-strontium manganites. However, the significance and extent of this unique phenomenon are not yet established. Here, we fabricate a thin film continuous composition map of the La0.8Sr0.2(Mn1-x Co x )0.85O3±Î´ family revealing a substantial enhancement of the grain boundary oxygen mass transport properties for the entire range of compositions. Through isotope-exchange depth profiling coupled with secondary ion mass spectroscopy, we show that this excellent performance is not directly linked to the bulk of the material but to the intrinsic nature of the grain boundary. In particular, the great increase of the oxygen diffusion in Mn-rich compositions unveils an unprecedented catalytic performance in the field of mixed ionic-electronic conductors. These results present grain boundaries engineering as a novel strategy for designing highly performing materials for solid-state ionics-based devices.
RESUMEN
Garnet-based Al-doped Li7La3Zr2O12 has the potential to be used as a solid state electrolyte for future lithium microbattery architectures, due to its relatively high Li(+) conductivity and stability against Li. Through this work, a model experiment is presented in which the effect of post-lithiation on phase formation and chemical stability is studied for pulsed laser deposited Al-doped Li7La3Zr2O12 thin films on MgO substrates. We report the implications of the newly suggested post-lithiation route for films with thicknesses between 90 and 380 nm. The phase changes from cubic, to a mix of cubic and tetragonal Li7La3Zr2O12, to a cubic Li7La3Zr2O12 and La2Zr2O7 containing film is accompanied by a reduction in the degree of de-wetting as the thickness increases. This study reveals that the thicker, dense, and continuous films remain predominantly in a mixed phase containing cubic Li7La3Zr2O12 and the lithium free La2Zr2O7 phase whereas the thinner, de-wetted films exhibit improved lithium incorporation resulting in the absence of the lithium free phase. For tuning the electrical conductivity and effective use of these structures in future batteries, understanding this material system is of great importance as the chemical stability of the cubic Li7La3Zr2O12 phase in the thin film system will control its effective use. We report a conductivity of 1.2 × 10(-3) S cm(-1) at 325 °C for a 380 nm thick solid state electrolyte film on MgO for potential operation in future all solid state battery assemblies.
RESUMEN
The present study is devoted to analyze the compatibility of yttria-stabilized zirconia thin films prepared by pulsed laser deposition and metalorganic chemical vapor deposition techniques, with microfabrication processes based on silicon technologies for micro solid oxide fuel cells applications. Deposition of yttria-stabilized zirconia on Si/SiO2/Si3N4 substrates was optimized for both techniques in order to obtain high density and homogeneity, as well as a good crystallinity for film thicknesses ranging from 60 to 240 nm. In addition, stabilized zirconia free-standing membranes were fabricated from the deposited films with surface areas between 50 x 50 microm2 and 820 x 820 microm2. Particular emphasis was made on the analysis of the effect of the nature of the deposition technique and the different design and fabrication parameters (membrane area, thickness and substrate deposition temperature) on the residual stress of the membranes in order to control their thermomechanical stability for application as electrolyte in micro solid oxide fuel cells.
