The sustainable electrochemical behavior of Li-metal/ion batteries heavily relies on the modulation of solid-electrolyte interphases (SEI) formed on their electrodes. In this study, we introduced trimesic acid (TMA) and terephthalic acid (TPA) into a conventional liquid electrolyte solution (LP57) comprised of 1.0 M LiPF6 in EC/EMC (3:7) to create suspension electrolyte systems. These solutions were tested in high-voltage Li and Li-ion cells comprising Li metal or graphite anodes (respectively) and LiNi0.5Mn1.5O4 (LNMO spinel) cathodes. The electrolyte solutions' modifications tested herein resulted in forming a LiF-rich interphase on the negative electrodes, which improved the Li-plating and stripping process, lowered voltage hysteresis, and reduced electrolyte solutions decomposition during prolonged electrochemical processes. We tested the suspension electrolyte systems in comparison to LP57 in Li & boxv;LNMO and Gr & boxv;LNMO cells at 30 degrees C and established significant improvements in the electrochemical performance, including long-term cycling, rate capability and capacity retention, average voltage, hysteresis, and evolution of the direct current internal resistance (DCIR) of cells containing the modified suspension solutions compared to the reference cells. The LNMO cathodes in Li-cells comprising the suspension electrolyte systems displayed remarkable structural, morphological, and thermal stability during prolonged cycling, delivering 98 % and 92 % capacity retention after 400 cycles in LP57 + TMA and LP57 + TPA, respectively, compared to only 38 % in the cells containing the conventional LP57 solution.

Fast and reliable evaluation of degradation and performance of cathode active materials (CAMs) for solid-state batteries (SSBs) is crucial to help better understand these systems and enable the synthesis of well-performing CAMs. However, there is a lack of well-thought-out procedures to reliably evaluate CAMs in SSBs. Current approaches often rely on X-ray photoelectron spectroscopy (XPS) for the evaluation of degradation. Unfortunately, XPS sensitivity is not very high, and minor but relevant degradation products may not be detected and distinguished. Furthermore, degradation caused by the current collector (CC) itself is usually not distinguished from CAM-induced degradation. This study uses a modified CC, which allows us to separate electrochemical degradation caused by the CC from degradation at the CAM itself. Using this CC, we present an approach using time-of-flight secondary ions mass spectrometry (ToF-SIMS) that offers high sensitivity and reliability. Principal component analysis (PCA) is applied to differentiate secondary ions as well as identify those mass fragments that correlate with degradation products. This approach also enables distinguishing between different pathways of degradation. To evaluate the kinetic performance of the samples, three-electrode rate tests are performed. Electrochemical characterization evaluates the kinetic performance of the samples under investigation. The samples are finally rated with a score that allows a reliable comparison between the different materials and offers a complete picture of the materials' characteristics in terms of electrochemical performance and degradation.

The work reported herein discusses the improved electrochemical and thermal behavior of LiNi0.5Mn1.5O4 (LNMO) spinel cathodes via surface engineering using a series of zeolites. The limiting issues of these high voltage electrodes are phase transition during Li-ions intercalation/de-intercalation processes, weakening the active material's structure. Besides, it initiates harmful interfacial side reactions, including solution species oxidation and Ni & Mn dissolution, affecting their long-term cycling stability severely and detrimentally. Therefore, we propose a zeolite-based surface modification of LNMO involving a simple surface coating strategy that includes liquid-phase (ethanol) mixing followed by heat treatment at 200 degrees C under nitrogen gas flow. The cathodes comprising LNMO coated with 2 wt% zeolites exhibited significantly improved cycling stability than the reference cathodes with the uncoated material. Furthermore, we discovered that the zeolite species adsorbed to the LNMO surface act as buffer interphase that enhance the electrodes' redox kinetics, trapping dissolved-TMs ions and serving as local Li+-ions reservoirs. Pouch cells containing graphite anodes and zeolite-coated LNMO cathodes demonstrated impressively improved electrochemical behavior in capacity retention during prolonged cycling, enhanced rate capability, lower voltage hysteresis, and direct current internal resistance (DCIR) evo-lution. The zeolite-based surface coating participates in (i) lowering HF formation in battery solutions by absorbing trace water, (ii) HF scavenging, and (iii) lowering TMs cations dissolution. Furthermore, Si and Al constituents of the zeolites can deposit on Li-anodes and possibly increase their stability, later established by additional electrochemical studies of full-pouch cells comprising uncoated LNMO cathodes vs. zeolite-coated graphite anodes. Other pivotal findings of this work are the coherent structural, morphological, and thermal stabilization of zeolite-coated LNMO cathodes during prolonged cycling experiments.

Enabling simple three-electrode (3E) setups for solid-state battery cells is important allowing investigation of individual electrodes to shed more light on interface charge transfer and reactions occurring in solid-state battery cells. Two different 3E setups are compared, and their practical value is evaluated. A miniaturized reference electrode ( μ -RE) is developed from lithium-plated gold wires with a tungsten core providing a stable potential. Cells with Li 6 PS 5 Cl as solid electrolyte, Li 1-x Ni 0.85 Co 0.10 Mn 0.05 O 2 (NCM851005) as cathode active material and Li 4 Ti 5 O 12 /Li 7 Ti 5 O 12 (LTO) or In/InLi as anode are investigated. The reference electrode provides a stable potential of 0 V vs Li + /Li, hence allowing the precise measurement of single electrode potentials. The setup leaves the usual cell geometry essentially unchanged and causes only minor additional work during cell assembly, allowing widespread application. Evidence is provided that 3E setups are needed to evaluate the rate capability of active materials correctly and that two-electrode (2E) setups can massively underestimate the rate capability of electrodes. The impedance of full cells is systematically analyzed based on separate anode and cathode impedances.

Here, three types of surface coatings based on adsorption of organic aromatic acids or their Li salts are applied as functional coating substrates to engineer the surface properties of high voltage LiNi0.5 Mn1.5 O4 (LNMO) spinel cathodes. The materials used as coating include 1,3,5-benzene-tricarboxylic acid (trimesic acid [TMA]), its Li-salt, and 1,4-benzene-dicarboxylic acid (terephthalic acid). The surface coating involves simple ethanol liquid-phase mixing and low-temperature heat treatment under nitrogen flow. In typical comparative studies, TMA-coated (3-5%) LNMO cathodes deliver >90% capacity retention after 400 cycles with significantly improved rate performance in Li-coin cells at 30 °C compared to uncoated material with capacity retention of ≈40%. The cathode coating also prevents the rapid drop in the electrochemical activity of high voltage Li cells at 55 °C. Studies of high voltage full cells containing TMA coated cathodes versus graphite anodes also demonstrate improved electrochemical behavior, including improved cycling performance and capacity retention, increased rate capabilities, lower voltage hysteresis, and very minor direct current internal resistance evolution. In line with the highly positive effects on the electrochemical performance, it is found that these coatings reduce detrimental transition metal cations dissolution and ensure structural stability during prolonged cycling and thermal stability at elevated temperatures.

Herein, a systematic surface modification approach via double gas (SO2 and NH3) treatment at elevated temperatures is described, aimed to achieve a stable electrochemical performance of Li and Mn-rich NCM cathode materials of a typical composition 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 (HE-NCM). Partial surface reduction of Mn4+ and the formation of a modified interface comprising Li-ions conductive nano-sized Li2SO4/Li2SO3 phases are established. Li-coin cells' prolonged cycling performance demonstrated significantly improved capacity retention (∼2.2 times higher than untreated cathode materials) for the double-gas-treated cathodes after 400 cycles at a 1.0 C rate. Stable discharge potential and lower voltage hysteresis during cycling were also achieved through the double gas treatment. Comparative electrochemical studies in full-pouch cells [vs. Graphite anodes] also demonstrated considerably stabilized electrochemical behavior for the double-gas-treated HE-NCM cathode materials. Lower gasses (O2, CO2, and H2) evolution in the first charge-discharge cycle and improved thermal stability are indeed crucial achievements of this treatment. Electrodes' post-cycling investigation revealed morphological integrity of the gas-treated cathode materials and lower transition metals (TMs) dissolution from the active cathodes. The positive effects of the double gas treatment are clearly related to the modified surfaces and lessening undesirable side reactions at the electrode-electrolyte solution interface.

Functional surface coatings were applied on high voltagespinel (LiNi0.5Mn1.5O4; LNMO) and Ni-rich (LiNi0.85Co0.1Mn0.05O2;NCM851005) NCM cathode materials using few-layered 2H tungstendiselenide (WSe2). Simple liquid-phase mixing with WSe2in 2-propanoland low-temperature (130 degrees C) heat treatment in nitrogenflow dramaticallyimproved electrochemical performance, including stable cycling, high-rateperformance, and lower voltage hysteresis in Li coin cells at 30 and 55 degrees C.Significantly improved capacity retention at 30 degrees C[Q401/Q9of 99% vs 38%for LNMO andQ322/Q23of 64% vs 46% for NCM851005] indicated efficientfunctionality. TEM and XPS clarified the coating distribution andcoordination with the cathode surface, while postcycling studies revealedits sustainability, enabling lower transition metal dissolution and minormorphological deformation/microcrack formation. A modified and stableSEI was apparently formed owing to W and Se deposition on the Li anodeduring cycling. The synergistic functionalization provided a significant dual benefit of cathodic and anodic stability.

All-solid-state Li-ion batteries that utilize nonflammable solid electrolytes are considered potential candidates for sustainable energy storage systems. Although sulfide solid electrolytes have been widely explored, their lack of electrochemical stability above 2.7 V requires the application of protective coating layer on 4 V-class cathode materials, whereas the superior oxidative stability of chloride solid electrolytes enables their direct use with such high voltage cathodes. Here, we report a metastable trigonal phase of Li3YbCl6 with an ionic conductivity of 1.0 X 10(-4) S.cm(-1) and mixed-metal halide solid electrolytes, Li3-xYb1-xZrxCl6, with conductivities up to 1.1 mS.cm(-1) at room temperature. Combined neutron, single-crystal, and powder X-ray diffraction methods reveal that Zr-substitution for Yb in Li3YbCl6 triggers a trigonal-to-orthorhombic phase transition and forms new, lower energy pathways for Li-ion migration. All-solid-state cell cycling with uncoated >4 V-class cathodes is enabled by the high electrochemical oxidation stability of the mixed-metal halide solid electrolyte.

Large-scale industrial application of all-solid-state-batteries (ASSBs) is currently hindered by numerous problems. Regarding thiophosphate-based ASSBs, interfacial reactions with the solid electrolyte are considered a major reason for capacity fading. On the positive electrode side, cathode active material coating addresses these issues and improves the ASSB performance. Yet, the working principle of the coating often remains unclear, and protection concepts on the way to long-term stable ASSBs remain empirical. In this work, we characterize the influence of a Li2CO3/LiNbO3 cathode active material coating on the battery performance and cathode degradation reactions of a Li4Ti5O12/Li6PS5Cl/Super C65 vertical bar Li6PS5Cl vertical bar LiNi0.6Co0.2Mn0.2O2/Li6PS5Cl/Super C65 cell. The coating microstructure is characterized comprehensively using a combination of focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Based on this knowledge, we demonstrate and discuss the positive effect of the coating on the ASSB performance. Finally, we present an in-depth post-mortem analysis of composite cathodes by combining XPS depth profiling with ToF-SIMS. The Li2CO3/LiNbO3 coating suppresses the interfacial reaction at the cathode active material/solid electrolyte interface, in particular, the formation of oxygenated phosphorous and sulfur compounds such as phosphates and sulfates/sulfites, leading to a significantly enhanced ASSB performance.

Ni-rich layered oxides LiNi 1- x - y Co x Mn y O 2 (1− x − y >0.5) are promising cathode materials for the new generation of Li-ion batteries suitable for electro-mobility due to their high energy density, good rate capability, and relatively low cost. However, their main drawback is poor cycling performance, particularly at elevated temperatures. In this research, it is demonstrated how doping with Al and Ti, using straightforward solid-state mixing synthesis, can dramatically enhance the structural, electrochemical, and thermal properties of LiNi 0.85 Co 0.1 Mn 0.05 O 2 (NCM85). The capacity retention of Al-doped and Ti-doped cathodes after 100 cycles at 100 % DOD at 1 C and 45 °C using standard electrolyte solutions could reach nearly 99 % and 78 %, respectively, while the capacity retention of the undoped material was less than 74 % in similar experiments. Doping with Al and Ti facilitates the Li intercalation processes and reduces voltage hysteresis. Structural study of the cycled cathodes shows that doping with Al, and to a smaller extent with Ti, reduces the formation of cracks in the particles of the cathode materials upon cycling, consequently reducing degradation. Thermal studies show that doping with Al or Ti improves the thermal stability of these cathode materials. Highly interesting is the correlation between the morphology and thermal stability, impedance properties and the electrochemical characteristics as a function of doping.

Described are a solid material which has ionic conductivity for lithium ions, a process for preparing said solid material, a use of said solid material as a solid electrolyte for an electrochemical cell, a solid structure selected from the group consisting of a cathode, an anode and a separator for an electrochemical cell comprising the solid material, and an electrochemical cell comprising such solid structure.

This work is part of ongoing and systematic investigations by our groups on the synthesis, electrochemical behavior, structural investigations, and computational modeling of the Ni-rich materials Li[NixCoyMnz]O2 (x+y+z=1; x≥0.8) for advanced lithium-ion batteries. This study focuses on the LiNi0.85Co0.10Mn0.05O2 (NCM85) material and its improvement upon doping with B3+ cations. The data demonstrate the substantial improvement of the doped electrodes in terms of cycling performance, lower voltage hysteresis and reduced self-discharge upon high temperature storage. The electronic structure of the undoped and B-doped material was modelled using density functional theory (DFT), which identified interstitial positions as the preferential location of the dopant. DFT models were also used to shed light on the influence of boron on surface segregation, surface stability, and oxygen binding energy in NCM85 material. Experimental evidence supports the suggestion that the boron segregates at the surface, effectively reducing the surface energy and increasing the oxygen binding energy, and possibly, as a result, inhibiting oxygen release. Additionally, the presence of borate species near the surface can reduce the nucleophilicity of surface oxygens. Cycling of the Li-cells did not cause noticeable changes in the microstructure of the B-doped materials, whereas significant microstructural changes, like a propagating network of cracks, was observed across all grains in the cycled undoped NCM85 cathodes. Analysis by high-resolution microscopy and 6Li and 11B solid-state nuclear magnetic resonance (ss NMR) allowed for the correlation of capacity fade and degradation of the different NCM85 materials with their structural characteristics.

We experimentally determine the redox reactions during (de-)lithiation of the SnO2 working electrode cycled in (Li2S)3-P2S5 solid electrolyte by combining operando X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy. Specifically, we have accurately determined the composition changes in the SnO2 working electrode upon cycling and identified the onset voltage formation of the various phases. Starting from the open-circuit potential, we find that, on lithiation, the Sn M-edge absorption spectra reveal unequivocally the formation of SnOx (x ≤ 1) and Li2SnO3 already at a potential of 1.6 V vs Li+/Li, while Sn 3d/Sn 4d, O 1s, and Li 1s core-level spectra show the formation of Sn0 and Li2O along the first potential plateau at 0.8 V vs Li+/Li and of Li8SnO6 at lower potentials. Below 0.6 V vs Li+/Li, an alloying reaction takes place until the end of the lithiation process at 0.05 V vs Li+/Li, as shown by the formation of LixSn. During delithiation, both the conversion and alloying reactions are found to be partially reversible, starting by the re-formation of Sn0 at 0.3 V vs Li+/Li and followed by the re-formation of Li8SnO6 and SnOx above 0.5 V vs Li+/Li. The conversion and alloying reactions are found to overlap during both lithiation and delithiation. Finally, we validate the theoretical prediction for the SnO2 conversion and alloy (de-)lithiation reactions and clarify the open questions about their reaction mechanism.

All-solid-state lithium batteries are a promising alternative for next-generation safe energy storage devices, provided that parasitic side reactions and the resulting hindrances in ionic transport at the electrolyte-electrode interface can be overcome. Motivated by the need for a fundamental understanding of such an interface, we present here real-time measurements of the (electro-)chemical reactivity and local surface potential at the electrified interface (Li2S)3-P2S5 (LPS) and LiCoO2 (LCO) using operando X-ray photoelectron spectroscopy (XPS) supplemented by X-ray photoemission electron microscopy (XPEEM). We identify three main degradation mechanisms: (i) reactivity at open circuit potential leading to the formation of reduced Co in the +2 oxidation state at the LCO surface, detected in the Co L-edge, which is further increased upon cycling, (ii) onset of electrochemical oxidation of the LPS at 2.3 V vs InLix detected in the S 2p and P 2p core levels, and (iii) Co-ion diffusion into the LPS forming CoSx species at 3.3 V observed in both S 2p and Co 2p core levels. Concurrently, a local surface overpotential of 0.9 V caused by a negative localized charge layer is detected at the LPS-LCO interface. Furthermore, in agreement with previous theoretical results, the presence of a sharp potential drop at the interface between active materials and solid electrolyte is demonstrated in all-solid-state batteries.

All-solid-state Li-ion batteries (ASSBs), considered to be potential next-generation energy storage devices, require solid electrolytes (SEs). Thiophosphate-based materials are popular, but these sulfides exhibit poor anodic stability and require specialty coatings on lithium metal oxide cathodes. Moreover, electrode designs aimed at high energy density are limited by their narrow electrochemical stability window. Here, we report new mixed-metal halide Li3-xM1-xZrxCl6(M = Y, Er) SEs with high ionic conductivity-up to 1.4 mS cm(-1) at 25 degrees C that are stable to high voltage. Substitution of M = Y, Er) by Zr is accompanied by a trigonalto-orthorhombic phase transition, and structure solution using combined neutron and single-crystal X-ray diffraction methods reveal a new framework. The employment of >4 V-class cathode materials without any protective coating is enabled by the high electrochemical oxidation stability of these halides. An ASSB showcasing their electrolyte properties exhibits very promising cycling stability up to 4.5 V at room temperature.

As potential next‐generation energy storage devices, solid‐state lithium batteries require highly functional solid state electrolytes. Recent research is primarily focused on crystalline materials, while amorphous materials offer advantages by eliminating problematic grain boundaries that can limit ion transport and trigger dendritic growth at the Li anode. However, simultaneously achieving high conductivity and stability in glasses is a challenge. New quaternary superionic lithium oxythioborate glasses are reported that exhibit high ion conductivity up to 2 mS cm−1 despite relatively high oxygen: sulfur ratios of more than 1:2, that exhibit greatly reduced H2S evolution upon exposure to air compared to Li7P3S11. These monolithic glasses are prepared from vitreous melts without ball‐milling and exhibit no discernable XRD pattern. Solid‐state NMR studies elucidate the structural entities that comprise the local glass structure which dictates fast ion conduction. Stripping/plating onto lithium metal results in very low polarization at a current density of 0.1 mA cm−2 over repeated cycling. Evaluation of the optimal glass composition as an electrolyte in an all‐solid‐state battery shows it exhibits excellent cycling stability and maintains near theoretical capacity for over 130 cycles at room temperature with Coulombic efficiency close to 99.9%, opening up new avenues of exploration for these quaternary compositions.

Described are a solid material which has ionic conductivity for lithium ions, a process for preparing said solid material, a use of said solid material as a solid electrolyte for an electrochemical cell, a solid structure selected from the group consisting of a cathode, an anode and a separator for an electrochemical cell, and an electrochemical cell comprising such solid structure.

A new disordered chlorospinel superionic conductor, Li2Sc2/3Cl4, enables high-voltage all solid state batteries up to 4.6 V vs. Li+/Li.

Operando XPS enables monitoring the chemical and electronic properties of the interface SE/active materials in ASSB.

For the successful employment of Li-ion batteries at large scale, e.g. for electrical vehicles or stationary energy storage, a crucial point to be solved is the development of safer, non-flammable batteries. For that purpose, the currently used carbonate-based liquid electrolyte has to be substituted with a non-flammable material such as solid-state electrolytes. In particular, (Li2S)3-P2S5 (LPS) is among the promising solid electrolyte (SE) materials showing a good ion conductivity at room temperature (~ 0.4 mS/cm)1. Another improvement that is also needed in the near future concerns the energy density of the battery. In order to increase this parameter, anode conversion-alloy materials, such as SnO2, are a serious choice, with a specific capacity of ~ 1500 mAh/g. Despite the theoretical predictions of the different SnO2 conversion and alloy reactions during (de-)lithiation, the experimental identification of those electrochemical reactions and the formation of intermediate species (e.g. LiaSnOb, LixSn and Li2O) is not fully understood2, mainly due to their possible relaxation and conversion to other byproducts during disassembling of the cycled cell in post mortem analysis3. Li2O, in particular, converts into the more stable Li2CO3 phase in presence of traces of CO2. In this contribution, we will show how we recently developed operando X-ray photoelectron spectroscopy (o-XPS) method, offering an unprecedented manner of monitoring in real time the evolution of the electrolyte-electrode interface and the (de-)lithiation processes of the active materials during solid state Li-ion battery operation4. In this study, o-XPS is employed to investigate the (de-)lithiation of the SnO2 particles in a working electrode composed of SnO2 nanoparticles, LPS SE and Super P as conductive carbon cycled versus InLix counter electrode (Figure 1a). The analysis of the Sn 3d (Figure 1b), Sn 4d, O 1s (Figure 1c) and Li 1s spectra reveals the progressive conversion of the SnO2 particles to form Sn0 and the simultaneous formation of the LixSn alloy. When the potential is below 0.4 V (vs. Li+/Li), the Li2O phase is formed and grows until the full lithiation at 0.01 V (vs. Li+/Li), where the only species observed are Li2O and LixSn. By avoiding the conversion of Li2O to Li2CO3, we are also able to follow the de-lithiation process, confirming the reversibility of the conversion-alloy reactions where LixSn is converted to SnOx at 2.3 V (vs. Li+/Li). The S 2p and P 2p core levels reveal the presence of reduced Li2S byproduct species below 1.6 V (vs. Li+/Li), in accordance with previous studies1. The knowledge gained with o-XPS on the (de-)lithiation processes of SnO2 and the stability of the SnO2-LPS interface is crucial to understand the mechanism leading to capacity loss during cycling and help to design a better cycling protocols for the SnO2 electrodes in solid-state batteries. References: Wu, M. El Kazzi, C. Villevieille, J. Electroceram., 2017, 38, 207-214 Cheng, A. Nie, L.-Y. Gan, Q. Zhang, U. Schwingenschlögi, J. Mater. Chem. A, 2015, 3, 19483 Ferraresi, C. Villevieille, I. Czekaj, M. Horisberger, P. Novák, M. El Kazzi, ACS Appl. Mater. Interfaces, 2018, 10, 8712-8720 X. Wu, C. Villevieille, P. Novák, M. El Kazzi, Phys. Chem. Chem. Phys., 2018, 20, 11123 Figure 1