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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 electro...

All-inorganic solid-state batteries (SSBs) currently attract much attention as next-generation high-density energy-storage technology. However, to make SSBs competitive with conventional Li-ion batteries, several obstacles and challenges must be overcome, many of which are related to interface stability issues. Protective coatings can be applied to the electrode materials to mitigate side reactions with the solid electrolyte, with lithium transition metal oxides, such as LiNbO3 or Li2ZrO3, being well established in research. In addition, it has been recognized lately that carbonates incorporated into the coating may also positively affect the interface stability. In this work, we studied the effect that surface carbonates in case of Li2ZrO3-coated Li1+x(Ni0.6Co0.2Mn0.2)1-xO2 (NCM622) cathode material have on the cyclability of pellet stack SSB cells with Li6PS5Cl and Li4Ti5O12 as a solid electrolyte and an anode, respectively. Both carbonate-rich and carbonate-poor hybrid coatings were produced by altering the synthesis conditions. The best cycling performance was achieved for carbonate-deficient Li2ZrO3-coated NCM622 due to decreased degradation of the argyrodite solid electrolyte at the interfaces, as determined by ex situ X-ray photoelectron spectroscopy and in situ differential electrochemical mass spectrometry. The results emphasize the importance of tailoring the composition and nature of protective coatings to improve the cyclability of bulk SSBs.

Gas evolution in conventional lithium-ion batteries using Ni-rich layered oxide cathode materials presents a serious issue that is responsible for performance decay and safety concerns, among others. Recent findings revealed that gas evolution also occurred in bulk-type solid-state batteries. To further clarify the effect that the electrolyte has on gassing, we report in this work-to the best of our knowledge-the first study comparing gas evolution in lithium-ion batteries with NCM622 cathode material and different electrolyte types, specifically solid (β-Li3PS4 and Li6PS5Cl) versus liquid (LP57). Using isotopic labeling, acid titration, and in situ gas analysis, we show the presence of O2 and CO2 evolution in both systems, albeit with different cumulative amounts, and possible SO2 evolution for the lithium thiophosphate-based cells. Our results demonstrate the importance of considering gas evolution in solid-state batteries, especially the formation and release of highly corrosive SO2, due to side reactions with the electrolyte.

Lithium–silicon compounds are used as active material in the negative electrodes of Li-ion batteries. The knowledge of Li diffusion in these materials is of importance for the optimization of charg...

Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes (SEs) of different crystallinity, namely glassy 1.5Li2S-0.5P2S5-LiI and argyrodite Li6PS5Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a SE with a low Young’s modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy SE employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.

Lithium‐ion batteries (LIBs), which utilize a liquid electrolyte, have established prominence among energy storage devices by offering unparalleled energy and power densities coupled with reliable electrochemical behavior. The development of solid‐state batteries (SSBs), utilizing a solid electrolyte layer for ionic conduction between the electrodes, could potentially offer further performance improvements in key areas such as energy density and safety. However, to date, SSBs remain unable to match the performance of their liquid counterparts. In light of renewed interest in accelerating the development of alternative energy storage devices, herein, a current overview of operando characterization techniques applied to solid‐state cells and related experimental setups is presented. Operando techniques, which allow materials to be studied as part of a dynamic system, have significantly advanced understanding of LIBs, and they offer the same potential for SSBs. To address this, a selection of analytical tools for probing interfacial/bulk electrochemical processes is highlighted and their advantages and challenges for studying various aspects of SSB chemistry are described. Finally, a perspective on how different techniques could support the future development of advanced SSBs is provided.

Bulk-type all-solid-state batteries (SSBs) are receiving much attention as next-generation energy storage technology with potentially improved safety and higher power and energy densities (over a w...

A room temperature, atomic-layer-deposition-like coating strategy for NCM811 (80% Ni) is reported. Trimethylaluminum is shown to readily react with adsorbed moisture, leading both to Al2O3 surface layer formation on NCM811 and to trace H2O removal in a single treatment step. Even more importantly, the cycling performance of pouch cells at 45 8C is greatly improved.

In recent years, investigations into improving the performance of bulk-type solid-state batteries (SSBs) have attracted much attention. This is due, in part, to the fact that they offer an opportunity to outperform the present Li-ion battery technology in terms of energy density. Ni-rich Li$_{1+x}$(Ni$_{1-y-z}$Co$_{y}$Mn$_{z}$)$_{1-x}$O$_{2}$ (NCM) and lithium-thiophosphate-based solid electrolytes appear to be a promising material combination for application at the cathode side. Here, we report about exploratory investigations into the 1.5Li$_{2}$S/0.5P$_{2}$S$_{5}$/LiI phase system and demonstrate that a glassy solid electrolyte has more than an order of magnitude higher room-temperature ionic conductivity than the crystalline counterpart, tetragonal Li$_{4}$PS$_{4}$I with the P4/nmm space group (∼1.3 versus ∼0.2 mS cm$^{-1}$). In addition, preliminary results show that usage of the glassy 1.5Li$_{2}$S–0.5P$_{2}$S$_{5}$–LiI in pellet stack SSB cells with an NCM622 (60% Ni content) cathode and a Li$_{4}$Ti$_{5}$O$_{12}$ anode leads to enhanced capacity retention when compared to the frequently employed argyrodite Li$_{6}$PS$_{5}$Cl solid electrolyte. This indicates that, apart from interfacial instabilities, the stiffness (modulus) of the solid electrolyte and associated mechanical effects may also impact significantly the long-term performance. Moreover, SSB cells with the glassy 1.5Li$_{2}$S–0.5P$_{2}$S$_{5}$–LiI and high-loading cathode (∼22 mg$_{NCM622}$ cm$^{-2}$) manufactured using a slurry-casting process are found to cycle stably for 200 cycles at C/5 rate and 45 °C, with areal capacities in excess of 3 mA h cm$^{-2}$.

Measures to improve the cycling performance and stability of bulk-type all-solid-state batteries (SSBs) are currently being developed with the goal of substituting conventional lithium-ion battery ...

The formation of gaseous side products in liquid electrolyte-based lithium-ion batteries has been intensively studied in recent years and identified as being one of the sources of degradation (an indication of electrolyte and electrode instabilities). Herein, we demonstrate, to our knowledge for the first time, that gassing can also arise in all-solid-state battery cells made of Ni-rich layered oxide cathode materials and thiophosphate-based solid electrolytes. Combining isotopic labeling, titration for quantitative carbonate determination, and operando gas analysis, our findings reveal the evolution of CO2 stemming from carbonate species on the cathode surface as well as O2 from the bulk of the oxide cathode at potentials above 4.5 V with respect to Li+/Li, among others.

The implementation of all-solid-state batteries (ASSBs) is regarded as an important step toward next-generation energy storage systems, in particular for electric vehicles and portable electronics. This may be achieved through application of layered Ni-rich oxide cathode materials such as Li1+x(Ni1–y–zCoyMnz)1–xO2 (NCM) with high specific capacity and thiophosphate-based solid electrolytes. Here, the profound effect that the secondary particle size of the cathode active material has on the capacity of ASSB cells comprising NCM622 (60% Ni), β-Li3PS4, and In anode is demonstrated. We show the benefits of using small particles (d ≪ 10 μm), allowing virtually full charge capacity. This finding is rationalized through galvanostatic charge–discharge tests and complementary ex situ and operando X-ray diffraction experiments combined with Rietveld refinement analysis. Our results indicate the importance of considering and avoiding electrochemically inactive electrode material in bulk-type ASSBs, which we show usi...

Li tracer self-diffusion was studied in amorphous lithium–silicon compounds which are important as negative electrodes in Li-ion batteries. Experiments were done on LixSi/6LixSi (LixSi, x ∼ 0.02 and x ∼ 0.06) thin-film heterostructures using secondary ion mass spectrometry. The diffusivities follow the Arrhenius law in the temperature range between 140 and 325 °C, both with an activation energy of (1.42 ± 0.03) eV, while the Li-richer samples show 1 order of magnitude higher diffusivities. A trap-limited diffusion mechanism is suggested, explaining this result with a lower concentration of unsaturated traps. A discussion against the literature suggests a strong lithium concentration dependence of diffusivities also for higher x.

Cell reports 2(6), 100465 (2021). doi:10.1016/j.xcrp.2021.100465, Laboratory research into bulk-type solid-state batteries (SSBs) has been focused predominantly on powder-based, pelletized cells and has been sufficient to evaluate fundamental limitations and tailor the constituents to some degree. However, to improve experimental reliability and for commercial implementation of this technology, competitive slurry-cast electrodes are required. Here, we report on the application of an approach guided by design of experiments (DoE) to evaluate the influence of the type/content of polymer binder and conductive carbon additive on the cyclability and processability of Li$_{1+x}$(Ni$_{0.6}$Co$_{0.2}$Mn$_{0.2}$)$_{1−x}$O$_2$ (NCM622) cathodes in SSB cells using lithium thiophosphate solid electrolytes. The predictions are verified by charge-discharge and impedance spectroscopy measurements. Furthermore, structural changes and gas evolution are monitored via X-ray diffraction and differential electrochemical mass spectrometry, respectively, in an attempt to rationalize and support the DoE results. In summary, the optimized combination of polymer binder and conductive carbon additive leads to high electrochemical performance and good processability., Published by Elsevier, [New York, NY]

Chemical communications 55(75), 11223 - 11226 (2019). doi:10.1039/C9CC04453A, Determining the state-of-charge of all-solid-state batteries via bothex situ and operando X-ray diffraction, rather than by electrochemicaltesting (may be strongly affected by electrically isolated/inactivematerial, irreversible side reactions, etc.), is reported. Specifically,we focus on bulk-type cells and use X-ray diffraction data obtainedon a liquid electrolyte-based Li-ion cell as the reference standardfor changes in lattice parameters with (de)lithiation., Published by Soc., Cambridge

In the ongoing search for new negative electrode materials for lithium-ion batteries, amorphous silicon with a theoretical specific capacity of almost 4000 mA h g−1 is still one of the most promising candidates. In order to optimize cycling behavior, prelithiation of silicon is discussed as possible solution. Yet, little is known about kinetics in the Li-Si system, especially with a low lithium content. Using neutron reflectometry as a tool, lithium permeation through amorphous LixSi layers was probed during annealing. From the results a lithium permeability (diffusivity×solubility) of P=(3.3±0.9)×10−21 m2 s−1 is derived for LixSi (x≈0.1), which is identical to that of pure amorphous silicon.

All-solid-state batteries (SSBs) are considered as next-generation energy storage technology with the possibility of higher energy and power densities as well as safety compared to conventional lithium-ion batteries [1]. SSBs with sulfidic solid electrolytes (SEs) as a component are thought to be the closest towards practical implementation [2] despite widely reported side reactions at the cathode active material (CAM)/SE interface. Advances in coating technology have helped suppress these detrimental reactions to a certain extent [3]. We demonstrate the use of differential electrochemical mass spectrometry (DEMS) on evaluating the stability of a protective surface coating [4]. Analysis of the gas evolved provides insights into possible reaction mechanisms at the CAM/SE interface. DEMS was also used to investigate the practical safety performance of sulfide-based SSBs with respect to possible harmful gas evolution such as H2S and SO2 [5]. Key Words: All-solid-state battery, differential electrochemical mass spectrometry, electrochemical energy storage References Janek, W. Zeier, Nat. Energy, 1 (2016) 16141. J. Nam, D. Y. Oh, S. H. Jung, Y. S. Jung, J. Power Sources, 375 (2018) 93–101. -Y. Kim, F. Strauss, T. Bartsch, J. H. Teo, T. Hatsukade, A. Mazilkin, J. Janek, P. Hartmann, T. Brezesinski, Chem. Mater., 31 (2019) 9664 – 9672. Bartsch, F. Strauss, T. Hatsukade, A. Schiele, A-Y. Kim, P. Hartmann, J. Janek, T. Brezesinski, ACS Energy Lett., 3 (2018) 2539–2543. Strauss, J. H. Teo, A. Schiele, T. Bartsch, T. Hatsukade, P. Hartmann, J. Janek, T. Brezesinski, ACS Appl. Mater. Interfaces, 12 (2020), 20462–20468.

International audience; Conversion type materials, in particular metal fluorides, have emerged as attractive candidates for positive electrodes in next generation Li-ion batteries (LIBs). However, their practical use is being hindered by issues related to reversibility and large polarization. To minimize these issues, a few approaches enlisting the anionic network have been considered. We herein report the electrochemical properties of bismuth oxyborate Bi4B2O9 and show that this compound reacts with lithium via a conversion reaction leading to a sustained capacity of 140 mA h g−1 when cycled between 1.7 and 3.5 V vs. Li+/Li0 while having a surprisingly small polarization (∼300 mV) in the presence of solely 5% in weight of a carbon additive. These observations are rationalized in terms of charge transfer kinetics via complementary XRD, HRTEM and NMR measurements. This finding demonstrates that borate based conversion type materials display rapid charge transfer with limited carbon additives, hence offering a new strategy to improve their overall cycling efficiency.

We present experiments based on neutron reflectometry in combination with 29Si/natSi isotope multilayers in order to investigate the self-diffusion in amorphous silicon. Such experiments allow the detection of diffusion processes in the amorphous state on length scales below 10 nm. First results at 650 °C show a continuous decrease of the artificial Bragg peak produced by the multilayer, corresponding to a diffusivity of (1.1 ± 0.4) x 10-20 m2/s on a length scale of 2 - 7 nm. The diffusivity is not time-dependent for annealing times between 3 min and 1 h. Compared to recent measurements in silicon single crystals by the same method, the diffusivity is higher by a factor of about 105.

Self-diffusion in thin nanocrystalline Pt films was investigated using secondary ion mass spectrometry. Our experiments are motivated by recent investigations on stress relaxation where self-diffusion of Pt is supposed to play an important role, especially at temperatures below 250 °C and annealing times of a few hours. For the diffusion experiments, double layers of natPt/194Pt were deposited on oxidized silicon wafers using ion beam sputtering. At 180 °C no significant diffusion induced broadening of the profiles could be observed even after an annealing time of 64 h. However, the concentration of 195Pt in the top layer decreases slightly after an annealing time of 16 h and remains constant for higher annealing times. At 600 °C a broadening of the profiles was observed after an annealing time of 5 minutes. From our results we conclude that at 180 °C only atoms in the grain boundaries are mobile. After about 16 h the isotopes in the grain boundaries are completely interdiffused. From the change of the 195Pt concentration in the top layer we estimate the amount of grain boundary phase in the Pt films to be about 5 %. The broadening of the profile after annealing at 600 °C is attributed to bulk diffusion.

Amorphous lithium–silicon compounds are promising materials in order to improve pure silicon as a high-capacity anode material in lithium-ion batteries. We demonstrated that it is possible to produce amorphous LixSi (x ≈ 0.4) thin films by reactive ion-beam co-sputtering of a segmented solid state target composed of metallic lithium and elemental silicon. At the surface a graded LixSiOy layer of some nanometer thickness is formed by contact with air which seems to prevent decomposition of the LixSi.

Experiments on self-diffusion in amorphous silicon between 400 and 500 °C are presented, which were carried out by neutron reflectometry in combination with 29Si/natSi isotope multilayers. Short range diffusion is detected on a length scale of about 2 nm, while long range diffusion is absent. Diffusivities are in the order of 10−19–10−20 m2/s and decrease with increasing annealing time, reaching an undetectable low value for long annealing times. This behavior is strongly correlated to structural relaxation and can be explained as a result of point defect annihilation. Diffusivities for short annealing times of 60 s follow the Arrhenius law with an activation enthalpy of (0.74 ± 0.21) eV, which is interpreted as the activation enthalpy of Si migration.