RESUMO
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.
RESUMO
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.
RESUMO
The abundance of the available sodium sources has led to rapid progress in sodium-ion batteries (SIBs), making them potential candidates for immediate replacement of lithium-ion batteries (LIBs). However, commercialization of SIBs has been hampered by their fading efficiency due to the sodium consumed in the formation of solid-electrolyte interphase (SEI) when using hard carbon (HC) anodes. Herein, Na2C3O5 sodium salt is introduced as a highly efficient, cost-effective, and safe cathode sodiation additive. This sustainable sodium salt has an oxidation potential of â¼4.0 V vs Na+/Na°, so it could be practically implemented into SIBs. Moreover, for the first time, we have also revealed by X-ray photoelectron spectroscopy (XPS) that in addition to the compensating Na+ ions spent in the SEI layer, the high specific capacity and capacity retention observed from electrochemical measurements are due to the formation of a thinner and more stable cathode-electrolyte interphase (CEI) on the P2-Na2/3Mn0.8Fe0.1Ti0.1O2 while using such a cathode sodiation additive. Half-cell studies with P2-Na2/3Mn0.8Fe0.1Ti0.1O2 cathodes show a 27% increase in the specific capacity (164 mAh gP2-1) with cathode sodiation additives. Full-cell studies with the HC anode show a 4 times increase in the specific capacity of P2-Na2/3Mn0.8Fe0.1Ti0.1O2. This work provides notable insights into and avenues toward the development of SIBs.
RESUMO
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.
