Search

Ordered mesoporous CuNiCo oxides were prepared via nanocasting with varied Cu/Ni ratio to establish its impact on the electrochemical performance of the catalysts. Physicochemical properties were determined along with the electrocatalytic activities toward oxygen evolution/reduction reactions (OER/ORR). Combining Cu, Ni, and Co allowed creating active and stable bifunctional electrocatalysts. CuNiCo oxide (Cu/Ni≈1 : 4) exhibited the highest current density of 411 mA cm

Developing high specific energy Lithium-ion (Li-ion) batteries is of vital importance to boost the production of efficient electric vehicles able to meet the customers’ expectation related to the electric range of the vehicle. One possible pathway to high specific energy is to increase the operating voltage of the Li-ion cell. Cathode materials enabling operation above 4.2 V are available. The stability of the positive electrode-electrolyte interface is still the main bottleneck to develop high voltage cells. Moreover, important research efforts are devoted to the substitution of graphite anodes with Li metal: this would improve the energy density of the cell dramatically. The use of metallic lithium is prevented by the dendrite growth during charge, with consequent safety problems. To suppress the formation of dendrites solid-state electrolytes are considered the most promising approach. For these reasons the present review summarizes the most recent research efforts in the field of high voltage solid-state electrolytes for high energy density Li-ion cells.

Coating conducting polymers onto active cathode materials has been proven to mitigate issues at high current densities stemming from the limited conducting abilities of the metal-oxides. In the present study, a carbon coating was applied onto nickel-rich NMC622 via polymerisation of furfuryl alcohol, followed by calcination, for the first time. The formation of a uniform amorphous carbon layer was observed with scanning- and transmission-electron microscopy (SEM and TEM) and X-ray photoelectron spectroscopy (XPS). The stability of the coated active material was confirmed and the electrochemical behaviour as well as the cycling stability was evaluated. The impact of the heat treatment on the electrochemical performance was studied systematically and was shown to improve cycling and high current performance alike. In-depth investigations of polymer coated samples show that the improved performance can be correlated with the calcination temperatures. In particular, a heat treatment at 400 °C leads to enhanced reversibility and capacity retention even after 400 cycles. At 10C, the discharge capacity for carbon coated NMC increases by nearly 50% compared to uncoated samples. This study clearly shows for the first time the synergetic effects of a furfuryl polymer coating and subsequent calcination leading to improved electrochemical performance of nickel-rich NMC622.

The chemical diffusion coefficient in LiNi1/3Mn1/3Co1/3O2 was determined via the galvanostatic intermittent titration technique in the voltage range 3 to 4.2 V. Calculated diffusion coefficients in these layered oxide cathodes during charging and discharging reach a minimum at the open-circuit voltage of 3.8 V and 3.7 V vs. Li/Li+, respectively. The observed minima of the chemical diffusion coefficients indicate a phase transition in this voltage range. The unit cell parameters of LiNi1/3Mn1/3Co1/3O2 cathodes were determined at different lithiation states using ex situ crystallographic analysis. It was shown that the unit cell parameter variation correlates well with the observed values for chemical diffusion in NMC cathodes; with a notable change in absolute values in the same voltage range. We relate the observed variation in unit cell parameters to the nickel conversion into the trivalent state, which is Jahn-Teller active, and to the re-arrangement of lithium ions and vacancies., Graphical Abstract

Maximizing the electrode thickness is an inevitable target to reach when improving the energy density of Li-ion batteries [1,2]. Unfortunately, the fabrication of electrodes of several hundreds of micrometer thickness is often accompanied by detrimental side-effects. A critical process step in thick electrode production is the drying of the coated layer. During the evaporation of the solvent, light components of the slurry such as binder and carbon black can be dragged to the top of the coating [3,4]. The lack of liquid linkage throughout the layer leads to binder particles being evenly spread across the coating after the drying process is concluded. Inhomogeneous distribution of binder can not only cause delamination, but also negatively influences the Li-ion transport pathways through the electrode. To ensure ideal mechanical stability and satisfactory electrochemical performance, binder migration needs to be suppressed effectively. Multi-layering has proven itself as a technique within aqueous processing to overcome the limitations arising for thick electrodes. Subsequent coating of layers offers opportunities to establish selective material compositions at specific regions within the electrode (Figure 1a). This novel coating method can be considered a steppingstone to further optimize high loading electrodes. We have previously demonstrated that by multi-layering an increase of 40% in adhesion can be achieved compared to single-layer electrodes. Moreover, the assembled cells show superior performances at rate capability tests. Especially for low current densities (0.2C) an increase of up to 20% in specific discharge capacity was reached through multi-layering (Figure 1b) [5]. Within aqueous electrode fabrication, the use of sodium carboxy-methyl cellulose (CMC) as binder material is common, due to its role as a thickening agent of the slurry and solubility in water. However, due to its brittleness, the usage of CMC requires additional binders to maintain flexibility of the coating. The ratio of active and inactive materials within the cell is strongly correlated to its capacity and the addition of these binders ultimately results in a decreased energy density of the cell. Besides keeping the particles together, the main purpose of the binder is to guarantee good adhesion to the substrate. Therefore, a high concentration is not necessarily needed at the top of the coating and the overall amount of binder material should be kept at a minimum. Bi-layered cathodes consisting of Ni-rich lithium nickel manganese cobalt oxides (NMC811) as active material were fabricated. The concentration of poly(methyl)acrylate (PMA) binder was changed in the top layer and its effect on structural properties and electrochemical performance was investigated. Water-based processed cathodes with high loadings of more than 8 mAhcm-2 were tested in full cell configurations. Reduction of the binder content leads to an increase in specific discharge capacity of up to 40% compared to single-layered and 25% to unmodified multi-layered electrodes at a C-rate of 1C (Figure 1b). Acknowledgements This work was financially supported by the Austrian Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (bmk). [1] Z. Du, D.L.W. Iii, C.D.S. Kalnaus, J. Li, Understanding limiting factors in thick electrode performance as applied to high energy density Li-ion batteries, J. Appl. Electrochem. 47 (2017) 405–415. https://doi.org/10.1007/s10800-017-1047-4. [2] Y. Kuang, C. Chen, D. Kirsch, L. Hu, Thick Electrode Batteries: Principles, Opportunities, and Challenges, Adv. Energy Mater. 9 (2019). https://doi.org/10.1002/aenm.201901457. [3] F. Font, B. Protas, G. Richardson, J.M. Foster, Binder migration during drying of lithium-ion battery electrodes: Modelling and comparison to experiment, J. Power Sources. 393 (2018) 177–185. https://doi.org/10.1016/j.jpowsour.2018.04.097. [4] M. Müller, L. Pfaffmann, S. Jaiser, M. Baunach, V. Trouillet, F. Scheiba, P. Scharfer, W. Schabel, W. Bauer, Investigation of binder distribution in graphite anodes for lithium-ion batteries, J. Power Sources. 340 (2017) 1–5. https://doi.org/10.1016/j.jpowsour.2016.11.051. [5] L. Neidhart, K. Fröhlich, N. Eshraghi, D. Cupid, F. Winter, M. Jahn, Aqueous Manufacturing of Defect-Free Thick Multi-Layer NMC811 Electrodes, Nanomaterials. 12 (2022) 1–15. https://doi.org/10.3390/nano12030317. Figure 1

Magnesium-ion batteries (MIBs) represent a promising chemistry to potentially substitute lithium-ion technologies in the e-mobility and stationary energy storage applications. This is due to the favourable properties of metallic Mg, such as: abundancy, non-toxic nature, high recycling rate1, low redox potential (-2.37 vs SHE), safety (smooth Mg2+ electrodeposition), as well as divalent character of Mg2+ cations which leads to higher theoretical volumetric capacity (3833 mAh/cm3) than Li (2046 mAh/cm3) and commercial graphite (760 mAh/cm3).2 However, the major obstacle in the further development of MIBs is the incompatibility of Mg metal anode with conventional electrolyte solutions, which are formed by mixing simple Mg-based salts (e.g Mg(TFSI)2, Mg(ClO4)2, etc.) and polar aprotic solvents (e.g. acetonitrile, carbonates, etc.). These solutions decompose at the surface of metallic Mg forming an electronic and ionic insulating layer, leading to the passivation of the Mg anode and poor performance of the overall cell. Conversely, organoborate (Mg-tetrakis(hexafluorosisopropyloxy)borate in monoglyme, MgBOR)3 or organoaluminate (1:2 AlCl3:PhMgCl in THF, APC)4 ethereal solutions are known to prevent the passivation of the Mg metal anode, allowing the reversible electrochemical Mg2+ electrodeposition onto its surface. Despite a great effort has been done in the development of MIB,5 very little is known about the formation, evolution and degradation of the solid electrolyte interphase (SEI) formed at the interface between metallic Mg and electrolyte. This work, therefore, aims to investigate the interactions between Mg metal and passivating (Mg(TFSI)2 in monoglyme:diglyme) and non-passivating (MgBOR and APC) electrolytes combining ex-situ and in-situ spectroscopic and microscopic techniques with electrochemical testing. The properties of the SEIs will be evaluated at different states of charge (ex-situ) and during cell cycling (in-situ). Raman, Fourier transformed infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies are used to identify the composition of the electrolyte interphases, as well as monitor their changes upon cell discharge-charge cycles. Scanning electron microscopy (SEM) is performed to analyse the interphase morphologies, whereas scanning microwave microscopy (SMM)6,7 locally probes the impedance of the SEI layer. Atomic force microscopy (AFM) is also employed to evaluate the roughness of the Mg metal electrodes. Cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) are carried out in order to determine the electrochemical performance of bare Mg metal or covered with SEI layers. Furthermore, electrochemical impedance spectroscopy (EIS) is employed to probe the Mg2+ diffusion coefficients through the SEI layers at different state of charge (e.g. open circuit voltage, etc.) and determine charge transfer evolution with cycling time of the Mg metal anode. As the first step, a successful polishing method was developed to remove the native oxide layer form the surface of Mg discs allowing to expose a bare Mg metal to the electrolyte solutions and to evaluate their interactions. The polishing method also enabled to perform SMM imaging of the Mg metal since a roughness between 1-2.5 µm was achieved. The Mg discs were then immersed in the electrolyte solutions and an initial deposition of interfacial species (few nanometre thickness) was observed by SEM when Mg(TFSI)2 in monoglyme:diglyme was used, whereas a smooth surface was detected with MgBOR and APC electrolytes. This resulted in different electrochemical behaviours. In fact, symmetric cells (Mg||Mg) with MgBOR electrolyte showed a significantly higher cycling stability (> 250 h) than those with Mg(TFSI)2 in monoglyme:diglyme solution. In addition, when the latter electrolyte was used, fluorinated by-products were identified by XPS. In order to study the SEI formation and growth further, in-situ spectroscopic techniques (e.g. Raman and SMM) were employed to establish a correlation between the chemical composition of the electrolyte, the voltage range of the electrochemical tests and cycling time. In particular, the SMM method was applied to MIB technologies for the first time in this work. References I. R. P. United Nations Environment Programme, (available at https://wedocs.unep.org/20.500.11822/8702); J. Niu, Z. Zhang, D. Aurbach, Adv. Energy Mater., 2020, 10, 2000697; Z. Zhao-Karger, M. E. Gil Bardaji, O. Fuhr, M. Fichtner, J. Mater. Chem. A, 2017, 5, 10815–10820; D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407, 724; R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot, V. Di Noto, J. Power Sources, 2020, 478, 229027; A. Buchter, J. Hoffmann, A. Delvallée, E. Brinciotti, D. Hapiuk, C. Licitra, K. Louarn, A. Arnoult, G. Almuneau, F. Piquemal, M. Zeier, F. Kienberger, Rev. Sci. Instrum., 2018, 89, 23704; J. Hoffmann, M. Wollensack, M. Zeier, J. Niegemann, H. Huber, F. Kienberger, in 2012 12th IEEE International Conference on Nanotechnology (IEEE-NANO), pp. 1–4.

In the field of secondary batteries, the lithium-ion battery (LIB) is one of the most promising candidates for future electric vehicle (EV) applications, due to its high specific energy and good specific power [1]. However, to meet the demands in large scale storage, not only higher energy and power density and lower cost are needed, but environmentally friendly processing of LiBs is getting more in the focus of research. To meet the desirable requirements, one necessity is to tune the cathode in terms of sustainable production and materials. Ni-rich layered LiNi x Mn y Co1−x−y O2 (NMCs, x ≥ 0.8) cathodes are poised to be the dominating cathode materials for lithium-ion batteries for the foreseeable future due to its high energy density [2]. The state-of-the-art NMC based cathode production in both industrial and lab scale is with polyvinylidene fluoride (PVDF) in organic solvent N-methyl-2-pyrrolidone (NMP). NMP is a toxic, expensive, and highly flammable organic solvent [3]. Replacing NMP with water in the production of LiB cathodes is critical in terms of process cost savings and environmental concerns. Aqueous processes of NMC based cathodes are highly favorable as well as challenging due to the high reactivity of NMC particles. During the slurry preparation, the surface of Ni-rich particles undergoes Li leaching via exchange between H+ from water and Li+ from the active material which leads to increase in pH of the slurry. Li leaching leads to capacity fade and reduces the specific capacity of the cathode. The high pH of the slurry causes corrosion on the aluminum current collector. Surface treatment of NMC particles is a way to prevent Li leaching as well as using carbon coated Al current collector to resist the corrosion, but in terms of production cost these methods are not favorable. In this study, our fundamental aim is to demonstrate the manufacturing of large scale water based NMC811-PAA cathodes. We therefore employ a well-known binder material, polyacrylic acid (PAA), which is water soluble and an anionic polymer. During the mixing processes of the slurry, H+ from PAA can drive Li+ leaching, the leached Li+ reacts with carboxylic groups of PAA and binds to the PAA backbone. Thus, the reaction of H+ and OH- neutralizes the pH of the slurry. Bonded Li+ on PAA creates an active binder in which these Li ions can participate as an additional Li source to aid to prevent capacity decrease. This method has been successfully implemented in the lab scale [4]. Our main target is to investigate the slurry behavior and scalability of the cathodes with a PAA binder. Herein, we report high solid content of slurry behavior of NMC with PAA and the comparison to the conventionally produced slurry for the first time. Also, we show how the slurry behavior is affected by the mixing techniques from lab scale to pilot scale, which is an important parameter for later transfer to industrial production. The electrodes and successfully formed LiPAA as binder are shown by Fourier transformed infrared (FTIR) and Raman spectroscopy. The electrochemical tests are performed both in half and full cell configuration for NMC811-PAA and NMC811-PVDF cathodes. References [1] Tao, Yanqiu, et al. "Second life and recycling: Energy and environmental sustainability perspectives for high-performance lithium-ion batteries." Science advances 7.45 (2021): eabi7633. https://doi.org10.1126/sciadv.abi7633. [2] Lu, Yanying, et al. "Single‐crystal LiNixMnyCo1− x− yO2 cathodes for extreme fast charging." Small 18.12 (2022): 2105833. https://doi.org/10.1002/smll.202105833. [3] Zou, Feng, and Arumugam Manthiram. "A review of the design of advanced binders for high‐performance batteries." Advanced Energy Materials 10.45 (2020): 2002508. https://doi.org/10.1002/aenm.202002508. [4] Hawley, W. Blake, Harry M. Meyer III, and Jianlin Li. "Enabling aqueous processing for LiNi0. 80Co0. 15Al0. 05O2 (NCA)-based lithium-ion battery cathodes using polyacrylic acid." Electrochimica Acta 380 (2021): 138203. https://doi.org/10.1016/j.electacta.2021.138203.

The end-of-life event of the battery system of an electric vehicle is defined by a fixed end-of-life threshold value. However, this kind of end-of-life threshold does not capture the application and battery characteristics and, consequently, it has a low accuracy in describing the real end-of-life event. This paper proposes a systematic methodology to determine the end-of-life threshold that describes accurately the end-of-life event. The proposed methodology can be divided into three phases. In the first phase, the health indicators that represent the aging behavior of the battery are defined. In the second phase, the application specifications and battery characteristics are evaluated to generate the end-of-life criteria. Finally, in the third phase, the simulation environment used to calculate the end-of-life threshold is designed. In this third phase, the electric-thermal behavior of the battery at different aging conditions is simulated using an electro-thermal equivalent circuit model. The proposed methodology is applied to a high-energy electric vehicle application and to a high-power electric vehicle application. The stated hypotheses and the calculated end-of-life threshold of the high-energy application are empirically validated. The study shows that commonly assumed 80 or 70% EOL thresholds could lead to mayor under or over lifespan estimations. The iModBatt project has received funding from the European Union’s Horizon 2020 Programme for research and innovation under Grant Agreement No. 770054.

Thanks to its exceptional performance in terms of high energy and power density as well as long lifespan, the lithium-ion secondary battery is the most relevant electrochemical energy storage technology to meet the requirements for partial or full electrification of vehicles (plug-in hybrids or pure electric vehicles), and thanks to decreasing cost and ongoing technical improvements, it will maintain this role in the near to mid-term future. This study benchmarks eight different (five 21700 and three 18650 format) high-energy cylindrical cells concerning their suitability for automotive applications and aims to give a holistic overview and comparison between them. Therefore, an ante-mortem material analysis, a benchmark of electrical and thermal values as well as a cycle life study were carried out. The results show that even when applying similar concepts like Nickel-rich cathodes with graphite-based anodes, the cells show wide variations in their performance under the same test conditions.

The paper reports the investigations performed in the course of the ESA TRP activity (Contract No. 4000123997/18/NL/HK) on the use of solid polymer electrolytes for safe lithium ion batteries for clean space. The objective is to develop 1Ah prototype pouch cells without using any volatile liquid component. The exchange of conventional, highly flammable electrolytes with solid Li+-conducting polymers significantly improves the electrochemical and thermal stability range of the battery cells. Thereby fragmentation events, and thus propagation of space debris, caused by battery malfunction can be mitigated. In the presented work, filled polymer electrolytes were investigated for potential use in all-solid-state lithium-ion batteries. The polyethylene oxide-based polymer phase was either mixed with a lithium-ion conducting glass-ceramic (active) or BaTiO 3 (passive) filler resulting in self-sustaining solid electrolyte membranes. Furthermore, carbon anodes and NMC622 cathodes were optimized to enable the assembly of full cells with enhanced safety properties.

Lithium-sulfur (Li–S) batteries are considered promising candidates for next-generation energy storage devices due to their ultrahigh theoretical gravimetric energy density, cost-effectiveness, and environmental friendliness. However, the application of Li–S batteries remains challenging; mainly due to a lack of understanding of the complex chemical reactions and associated equilibria that occur in a working Li–S system. A new approach preparing graphene-based active cathode materials of Li-S battery with spatially confined lithium sulfides is reported. The starting graphene-embedded 2D-MoS2 was synthesized by a solvothermal method in organic solvents followed by the calcination of trapped organic solvent molecules at 800 °C to give graphene single sheets inside the 2D-MoS2 layers with 7 A distance (MoS2-Gr-32.51). Then, it was electrochemically reduced/lithiated at potential 0.01 V vs Li+/Li generating metallic molybdenum and lithium sulfides. As a result, the structure of MoS2 multi-layers collapsed. The graphene multi-layer (ML-Graphene) was left behind and shut the lithium sulfides between the layers. The sizes of Li2Sn (n = 4–6) are bigger than the inter-layer distance of ML-Graphene, and the escape of sulfur/sulfides from the cathode into the electrolyte is physically blocked alleviating shuttle effects. The specific capacity of ML-Graphene/lithium sulfides cathode was high of 1209 mAh/gMoS2-Gr at 0.1 C (1 C = 670 mA/g). The ML-Graphene exhibited the remarkable lithium intercalation capability, and the theoretical calculation has been carried out to give 2231.4 mAh/g. Such high capacity was hybridized with the theoretical capacity of sulfur (1675 mAh/g), and the ML-Graphene composite with dichalcogenides (2D-MoS2) became a promising platform for the cathode of Li-S batteries.

Tin (IV) sulfide is a promising anode active material for lithium ion batteries due to its relatively high reversible capacity of 644 mAh/g, which is more than one and a half times that of graphite. During lithiation of tin (IV) sulfide, an inert Li2S matrix is formed in the first discharge cycle, which serves to accommodate the mechanical stresses associated with the volume expansion of tin during the successive LixSn alloying and de-alloying reactions. In order to improve the electrochemical performance of tin (IV) sulfide further, fundamental understanding and insights into the thermodynamics, phase formation, and driving forces for the lithiation reactions are still required. Therefore, in this work, a computational thermodynamics approach was combined with ex-situ XRD investigations of electrodes during the discharge reaction as well as galvanostatic intermittent titration technique (GITT) experiments in order to clarify the lithiation thermodynamics of tin (IV) sulfide. Based on the experimental data, a one-phase mechanism was suggested for the intercalation of lithium into SnS2, a thermodynamic model was developed to describe the intercalation reaction and the expected open circuit voltages were calculated.

Lithium-Ion batteries are the key technology to power mobile devices, all types of electric vehicles, and for use in stationary energy storage. Much attention has been paid in research to improve the performance of active materials for Lithium-Ion batteries, however, for optimal, long and safe operation, detailed knowledge of -among others- the state-of-charge and the state-of-health of the battery is paramount both in laboratory use, as well as during application by the battery management system. Today’s systems often derive their estimators from data of the voltage, current and temperature measurements, which can lead to inaccurate estimations of values during operation. Mechanical based measurements became very popular recently to fill the gap in data by complementing conventional measurements and thus provide more accurate information about the internal state of Lithium-Ion batteries. This review aims to present the current state of this promising topic for both laboratory use and applications on non-destructive in-situ and in-operando methods for measurement of mechanical battery parameters like expansion, strain and force, experimental modal analysis, ultrasonic probing and acoustic emission technologies. The intention of this summary is to provide insights in this emerging topic by showing benefits, drawbacks, possibilities and applications of each technique and compare those to each other, thus providing the readers with a deep insight into the topic.

Lithium Ion Batteries (LIB) find not only wide use in portable devices and consumer electronics, but also attract increasing attention in stationary energy storage and the automotive sector. In this regard, LIBs play a significant role as intermediate energy storage due to their high volumetric and gravimetric energy, high power density, and long cycle life. To achieve the required performance, the interaction of novel anode and cathode materials is of paramount interest. Particularly, the safety of cell operation must be assessed with respect to the formation of volatile and reactive species during cycling which can negatively alter cell components. Gas chromatography mass spectroscopy (GCMS) has proven to be a reliable tool for species detection. Unfortunately, conventional GC systems lack time resolution for in-situ gas analysis regarding fast processes, for example battery failure. Therefore, developing operando testing methods with improved time resolution is key to giving insight into electrolyte alterations during battery operation. Here one of them, a novel multiplex injection method is presented as a monitoring technique for gas species arising from the decomposition of conventional LIB electrolytes. The combination of the multiplexing technique and GCMS allows the analysis of fast decomposition processes by 15 fold increase of time resolution compared to conventional gas chromatography. In addition, FTIR allows online monitoring of selected vibration bands. Commercially produced pouch cells were monitored with respect to evolving gas species during battery operation under overcharge conditions. For the decomposition of LiPF6 / organic carbonate- based electrolytes alkanes, alcohols, ethers, esters, aldehydes and also derivatives that appear in the presence of hydrofluoric acid such as fluorinated alkane species, have been evaluated. The author gratefully acknowledges the FFG (Austrian Research Promotion Agency) for funding this research within project No. 858298.

Batteries based on the magnesium-ion chemistry are considered as promising alternatives to lithium ion technologies due to the di-valent character of the Mg2+ cations, the high theoretical volumetric capacity of magnesium (3833 mA h cm-3 for the Mg-anode), as well as its low toxicity and natural abundance. Furthermore, since magnesium deposition takes place without dendrite formation on the Mg-metal anode surface, the Mg-cell is expected to be considerably safer than comparable cells based on lithium metal.1 Despite these positive attributes, the development of magnesium secondary batteries is hindered by the high charge density and the slow solid-state diffusion of Mg2+ ions into the cathode lattice, which lead to relatively low practical capacities, irreversible capacity losses and poor cyclic stability. In order to improve the slow kinetics of Mg2+ insertion-extraction during the electrochemical reaction, new electrode materials should be developed.2 Since phosphate-based compounds with NASICON and olivine-related structures exhibit open three-dimensional frameworks, structural stability and safety under oxidizing conditions, they are considered as suitable candidate electrode materials for multi-valent ion batteries.3,4 Therefore, in this work the NASICON-structured Mg0.5Ti2(PO4)3 and the novel olivine-related (Mg0.5Ni0.5)3(PO4)2 compounds were synthesised by the solid-state method and investigated as potential electrode materials. Mg0.5Ti2(PO4)3 and (Mg0.5Ni0.5)3(PO4)2 were subjected to a comprehensive physico-chemical characterization (XRD, SEM, BET and DLS techniques) in order to optimize the synthesis conditions, determine the phase purities and assess the particle morphologies. Furthermore, the reaction mechanisms and electrochemical behaviour of the orthophosphate-based materials with monovalent Li+ and divalent Mg2+ ions were investigated using post-mortem analysis (XRD and IR) in order to establish the nature of the charge storage reaction mechanisms (i.e. intercalation or conversion). In addition to the challenges associated with the development of novel electrode materials, it is well known that electrolytes, formed by ionic salts (i.e. Mg(ClO4)2) and aprotic organic solvents (i.e. acetonitrile), form cationic insulating layers on the surface of the Mg metal anode, leading to poor performance of the overall cell. In order to address this problem, two different approaches were adopted during the electrochemical testing. Firstly, sulfone and glyme-based solutions were tested as candidate electrolytes in order to investigate their suitability with the Mg anode by analysing the passivation of the metal surface via infrared spectroscopy measurements. In a second approach, activated carbon (AC) was used as the counter electrode to replace the metallic magnesium when using Mg(ClO4)2 in acetonitrile as the electrolyte, since AC does not participate in parasitic reactions.5 Moreover, due to its high surface area, AC stores charge in a double layer on its external surface. Therefore, the systems formed by coupling AC and a conventional working electrode exhibit hybrid capacitive behaviour. Despite this, the use of AC as a counter electrode allows the investigation of the insertion of Mg2+ cations from the electrolyte into the working electrode. This set up enables the assessment of the electrochemical behaviour of the candidate working material without passivation reactions which could occur at the electrode/electrolyte interface. In particular, promising results are achieved using Mg0.5Ti2(PO4)3 as working electrode material, even though only surface sites were occupied with Mg2+ cations due to the sluggish intercalation kinetics. References 1. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci., 2013, 6, 2265–2279; 2. Z. Ma, D. R. MacFarlane, M. Kar, Batter. Supercaps, 2019, 2, 115–127; 3. P. Canepa, G. Sai Gautam, D. C. Hannah, R. Malik, M. Liu, K. G. Gallagher, K. A. Persson, G. Ceder, Chem. Rev., 2017, 117, 4287–4341; 4. B. Kang, G. Ceder, Nature, 2009, 458, 190; 5. G. Gershinsky, H. D. Yoo, Y. Gofer, D. Aurbach, Langmuir, 2013, 29, 10964–10972.

Due to its theoretical capacity of 960 mAh/g, which is approximately two and a half times that of graphite (372 mAh/g), as well as its natural abundance, Sn is as an interesting anode active material to replace the currently used graphite in lithium ion batteries. However, Sn-based anodes have not been commercialized because they suffer from prohibitively large volume expansions due to the formation of brittle LixSn alloys during lithiation (>185 % for full lithiation to Li17Sn4). These volume changes lead to extensive crack formation, loss of electrical contact between particles, pulverization of the electrode during cycling, lithium trapping, and the growth of an unstable SEI. One way to take advantage of the high capacity of Sn and simultaneously overcome its degradation mechanisms is to use Sn-based chalcogenide compounds such as SnS2 and SnS as anode active materials. During lithiation of these compounds, a composite electrode structure consisting of active Sn particles embedded in an inactive Li2S buffer matrix is formed, which is expected to accommodate the mechanical stress of the alloying and de-alloying reactions during cycling. Although several authors have studied the lithiation of SnS2 via in-situ electron microscopy techniques, there are still many open questions regarding 1) the amount of lithium which can be intercalated into the layered structure of SnS2, 2) the structural changes of SnS2 during lithiation, and 3) if the reaction occurs via a one-phase or a two-phase process. Additionally, there are no published phase diagrams of the Li–Sn–S system at room temperature, which could be used to explore the changes in the electrode constitution during lithiation and de-lithiation. In fact, only Hwang et al. [1] modelled the phase equilibria in the Li–Sn–S at 0 K using density functional theory (DFT) calculations, but their data are incomplete since they omitted the Sn2S3, Li7Sn3 and Li5Sn2 phases and did not take into account the electrochemically and chemically observed solubility of lithium in SnS2. Therefore, in this work, the CALPHAD (CALculation of PHAse Diagrams) and computational thermodynamics methods were combined with key experiments to 1) understand the electrochemical lithiation of SnS2, 2) model the phase development during the equilibrium and non-equilibrium lithiation of the SnxSy tin sulfide compounds, and 3) evaluate the energetics of the competing lithiation reactions for the first time. Firstly, a thermodynamic description for the ternary Li–Sn–S system was developed by combining the descriptions of the Li–Sn system from Reichmann et al. [2] with that for the Sn–S system from Lindwall et al. [3] and the Gibbs free energy function for Li2S from the Scientific Group Thermodata Europe (SGTE) [4]. The ternary database was used to calculate the Li–Sn–S phase diagram at room temperature and simulate the titration curves for the equilibrium lithiation of the tin sulfide compounds. At the same time, homogeneous and heterogeneous Sn–S powder samples were processed as slurries, coated onto copper-foil substrates and subjected to electrochemical testing vs Li+/Li. The galvanostatic intermittent titration technique was used to characterize the quasi-equilibrium open circuit potentials of the electrodes during full and partial de-/lithiation in the potential range of 0.01-2.5 V. Additionally, a full profile, Rietveld refinement of the ex-situ XRD patterns of selected electrodes was performed in order to assess the phase development and structural changes of the electrode active materials during titration. These data were used to suggest a one-phase mechanism for the equilibrium lithiation of SnS2 after voltage relaxation. Finally, the electrochemical and crystallographic data were used to develop a new thermodynamic model to describe the intercalation of lithium ions into the layered SnS2 structure and calculate the measured open circuit voltage values. Using this description, it could be shown that lithiated SnS2 is indeed a metastable phase, which forms due to the energetic feasibility of the intercalation mechanism compared to the equilibrium conversion reaction. References [1] S. Hwang, et al., ACS Nano, 12, (2018), 3638-3645. [2] T.L Reichmann, D.J. Li, D.M. Cupid, Phys. Chem. Chem. Phys. 20 (2018), 22856-22866 [3] G. Lindwall, S.L. Shang, N.R. Kelly, T. Anderson, Z.K. Liu, Solar Energy (2016) 314-323 [4] SGTE Substance Database SGSUB, Version 4, 2008

Surface degradation of Ni-enriched layered cathode material Li[Ni0.6Mn0.2Co0.2]O2 (NMC622) is the main reason that leads to large capacity decay during long-term cycling. In the frame of this research, an amorphous SiO2 coating was applied onto the surface of the commercially available NMC622 powder by a wet coating process, through the condensation reaction of tetraethyl orthosilicate. The chemical composition of the coating layer was analyzed by inductively-coupled plasma. The morphology was studied by scanning electron microscopy and transmission electron microscopy. Electrochemical properties, including cyclic voltammetry, galvanostatic cycling, and rate capability measurements in a half-cell configuration, were tested to compare the electrochemical behavior of the non-coated and coated NMC622 materials. It is shown that the rate performance of the NMC622 materials is not affected by the coating layer. After 700 cycles in the range of 3.0&ndash, 4.3 V at 2 C discharge, the cells with SiO2-coated NMC622 materials retained 80% of their initial capacity, which is higher than the uncoated ones (74%). Physicochemical characterizations, e.g., XRD and SEM, were performed post-mortem to reveal the stabilizing mechanism of the SiO2-coated NMC622 electrodes after long-term cycling. Based on these results, this is due to the shielding effect of the coating between the NMC622 particle surface and the liquid electrolyte, along with its scavenging effect on HF. SiO2 coating is therefore a facile surface modification method that results in potentially significant enhancement of the cyclic stability of Ni-rich NMC materials.

Recent advances in micro- and nano-electromechanical systems (MEMS/NEMS) technology have led to a niche industry of diverse small-scale devices that include microsensors, micromachines and drug-delivery systems. For these devices, there is an urgent need to develop Micro Lithium Ion Batteries (MLIBs) with dimensions on the scale 1–10 mm3 enabling on-board power delivery.\ud \ud Unfortunately, power limitations are inherent in planar 2D cells and only the advent of 3D designs and microarchitectures will lead to a real breakthrough in the microbattery technology. During the last few years, many efforts to optimise MLIBs were discussed in literature, both in the planar and 3D configurations.\ud This review highlights the importance of 3D microarchitectured electrodes to fabricate batteries that can be device-integrated with exceptionally high specific power density coupled with exquisite miniaturisation. A wide literature overview is provided and recent advances in manufacturing routes to 3D-MLIBs comprising materials synthesis, device formulation, device testing are herein discussed. The advent of simple, economic and easily scalable fabrication processes such as 3D printing will have a decisive role in the growing field of micropower sources and microdevices.

The depletion of fossil fuel reserves as well as climate change motivate the development of new environmentally-friendly technologies for energy generation, storage, and consumption. Robust energy storage devices must be developed to meet the growing demand for portable electronics (i.e. laptops and mobile phones), electric vehicles and energy storage systems. Although lithium-ion batteries have mostly driven the revolution in modern electronics for the last three decades, new chemistries for “next-generation” batteries are currently under research and development. These new technologies are tasked with delivering better performance (capacity and current capability) at low cost while being environmentally friendly. In order to fill the gap between the current state of the art and future energy storage needs, magnesium is considered to be a possible alternative to lithium due to its natural abundancy and low toxicity. Furthermore, due to the divalent nature of the Mg2+ cations, a high theoretical volumetric capacity of 3833 mA h cm-3 can be attained if pure magnesium is used as the anode material.1 Additionally, since magnesium deposition takes place without dendrite formation on the Mg-metal anode surface, the Mg-cell is expected to be considerably safer than comparable cells based on lithium. Despite these positive attributes, the development of magnesium secondary batteries is hindered by the slow solid-state diffusion of Mg2+ ions into the cathode lattice. In this work, this issue is explored by synthesising and characterising two different phosphate-based systems to investigate their suitability as cathode materials for Mg-ion batteries, with phosphates chosen due to their structural stability and safety.2,3 The NASICON and olivine phosphates are known for their high conductivity in lithium-based systems and were selected here as potential hosts for Mg2+intercalation. NASICON compounds are usually reported as cathode or solid electrolyte materials for Li and Na-ion batteries, but there is a lack of reproducible data for Mg ion technologies. Therefore, the NASICON-structured Mg0.5Ti2(PO4)3 compound was selected for synthesis and further electrochemical characterisation. Additionally, the olivine-related (Mg0.5Ni0.5)3(PO4)2 was investigated as a novel cathode active material for the first time. This compound was chosen because of its open crystal structure, which is potentially favourable for magnesium ion diffusion. In parallel, V2O5 was used as a reference cathode active material in order to validate the electrochemical set-up, which is non-trivial for Mg chemistry. Mg0.5Ti2(PO4)3 and (Mg0.5Ni0.5)3(PO4)2 were obtained by the solid-state method and their crystal structures and phase purities were determined by Rietveld analysis of X-ray powder diffraction data. Scanning electron microscopy (SEM) was performed to analyse the particle morphologies, with particle sizes and porosities characterised by dynamic light scattering (DLS) and nitrogen adsorption (BET) techniques, respectively. Both cyclic voltammetry and galvanostatic cycling with potential limitation were carried out in order to investigate the insertion-extraction mechanism of Mg2+ ions. Ex-situ powder X-ray diffraction and SEM confirmed the crystal structures and particle morphologies, respectively, of the cathode active materials after cycling, while X-ray photon electron spectroscopy (XPS) was used to monitor changes in the oxidation state of the transition metal cation. Our results show that cells based on Mg metal anodes utilising Mg(ClO4)2 in acetonitrile as electrolyte suffer from the creation of a passivation layer leading to poor performance. In order to address this problem, activated carbon was used to replace metallic magnesium as the anode material, with the electrolyte acting as the main source for magnesium ions. The use of a carbon-based anode is seen to eliminate the passivation layer problem and improve capacity and cell cyclability. References H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci., 2013, 6, 2265–2279; P. Canepa, G. Sai Gautam, D. C. Hannah, R. Malik, M. Liu, K. G. Gallagher, K. A. Persson, G. Ceder, Chem. Rev., 2017,117, 4287–4341; B. Kang, G. Ceder, Nature, 2009,458, 190.

The use of high energy materials for Lithium ion batteries has given rise to the use of Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2, NCA) as viable cathode alternative to the traditionally used LiCoO2 (LCO). The expected usable specific gravimetric capacity of ~170mAh/g and a good cycle life with potential cost saving and less environmental impact compared to LCO make it interesting for commercial applications such as the automotive industry. Especially the use of NCA in electric vehicles is discussed by various major industrial players, with Panasonic and Tesla being on the forefront of this development. In conventional laboratory developments, small scale mixing and coin cell level testing is used to highlight novel material performance. However, this disguises the difficulties that some chemistries and electrode coating experience when scaled to levels that are closer to production. At the heart of academic electrode development is a small scale mixing of few grams of active material and standardised recipes of maximum 80% active material content in the mix. Whilst this is valuable for initial assessment, the manufacturing parameters do not translate well to large scale, industrially used electrode slurries, which would aim at active material contents of well above 90%. In addition, large scale development of slurries that have to be coated on several hundreds of meters has to consider coating adhesion properties and slurry viscosity for optimum coating. Furthermore, an optimised coating and calendering regime needs to be established in order to make the process viable for production. The presented work shows the correlation between several real world mixing recipes and procedures and their corresponding coating behaviour and electrochemical performance. Mixing has been done using a combination of small and large scale high torque, shear and energy mixers to process slurry volumes of up to 10L. This gives a processing procedures closer to production level when compared to conventional lab scale experiments. Coating parameters have been varied in terms of coating speed and drying conditions. Rheological properties of the mixes have been measured and the corresponding coating quality has been assessed using optical methods as well as adhesion tests. The coat weight uniformity is confirmed in situ during the coating process using ultrasonic absorption technology. The electrochemical performance of several electrode coatings has been determined using both a small scale conventional coin cell testing and a larger scale A5 sized pouch cell test for verification of coating quality and performance consistency. This work illustrates how this type of research is needed for any new electrode chemistry to be verified on production scale, before industrial entities can take up said material for implementation. In conclusion, this work highlights the challenges of scaling up electrode chemistries from lab scale to pre-production scale. NCA coatings have been prepared using several litres of slurry mix and A5 sized pouch cells have been manufactured in order to confirm electrochemical performance variation depending on coating and mixing parameters as well as overall coating consistency.

Development of future battery generations and quality control of current lithium-ion battery (LIB) systems require reliable techniques for the characterization of the complex dynamic processes in batteries. Electrochemical impedance spectroscopy (EIS) is an established tool for the electrochemical characterization of LIBs and the related ageing processes. Nevertheless, ensuring a reliable interpretation and validation of the impedance data remains challenging. Here we show how EIS complemented by microscopy data can be successfully used to follow battery ageing. We connect data from both methods in an electrochemical finite element model (FEM) to extract changes of intrinsic battery parameters, such as double layer capacitance, film resistance, exchange current density, and particle radii. Ageing mechanisms induced by cycling and temperature are investigated by EIS on commercial cells. Postmortem analysis of the anode and cathode electrodes is carried out to determine their initial micrometric and nanometric structure and to independently investigate morphological and electrical changes induced by ageing. While the obtained initial structural dimensions reduce drastically the number of adjustable parameters in the FEM model, which enables us to follow battery ageing processes noninvasively through the EIS spectra, the microscopy results of the aged cells prove independently the validity of the here presented approach.