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“Thick electrode using high voltage cathode” can be considered, since this research focuses on high voltage cathode materials.

All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries. In this work, we demonstrate the importance of careful solid electrolyte selection for use against an alloy anode in Na all-solid-state batteries. Three emerging solid electrolyte material classes were chosen for this study: the chloride Na

Manufacturing sustainable sodium ion batteries with high energy density and cyclability requires a uniquely tailored technology and a close attention to the economical and environmental factors. In this work, we summarized the most important design metrics in sodium ion batteries with the emphasis on cathode materials and outlined a transparent data reporting approach based on common metrics for performance evaluation of future technologies.Sodium-ion batteries are considered as one of the most promising alternatives to lithium-based battery technologies. Despite the growing research in this field, the implementation of this technology has been practically hindered due to a lack of high energy density cathode materials with a long cycle-life. In this perspective, we first provide an overview of the milestones in the development of Na-ion battery (NIB) systems over time. Next, we discuss critical metrics in extraction of key elements used in NIB cathode materials which may impact the supply chain in near future. Finally, in the quest of most promising cathode materials for the next generation of NIBs, we overlay an extensive perspective on the main findings in design and test of more than 295 reports in the past 10 years, exhibiting that layered oxides, Prussian blue analogs (PBAs) and polyanions are leading candidates for cathode materials. An in-depth comparison of energy density and capacity retention of all the currently available cathode materials is also provided. In this perspective, we also highlight the importance of large data analysis for sustainable material design based on available datasets. The insights provided in this perspective, along with a more transparent data reporting approach and an implementation of common metrics for performance evaluation of NIBs can help accelerate future cathode materials design in the NIB field. Graphical abstract

A non-flammable ionic liquid-ether based hybrid electrolyte shows a robust Li deposition morphology and a very stable cycling of NMC|Li metal cell facilitated by a beneficial interphase formation at the anode surface.

When exposed to moisture, Li6PS5Cl undergoes both hydrolysis and hydration reactions. It can be partially recovered by heat treatment, but hydrolysis causes the formation of LiCl, Li2S, Li3PO4, and oxysulfides due to the irreversible sulfur loss.

Transitioning toward more sustainable materials and manufacturing methods will be critical to continue supporting the rapidly expanding market for lithium-ion batteries. Meanwhile, energy storage applications are demanding higher power and energy densities than ever before, with aggressive performance targets like fast charging and greatly extended operating ranges and durations. Due to its high operating voltage and cobalt-free chemistry, the spinel-type LiNi0.5Mn1.5O4 (LNMO) cathode material has attracted great interest as one of the few next-generation candidates capable of addressing this combination of challenges. However, severe capacity degradation and poor interphase stability have thus far impeded the practical application of LNMO. In this study, by leveraging a dry electrode coating process, we demonstrate LNMO electrodes with stable full cell operation (up to 68% after 1000 cycles) and ultra-high loading (up to 9.5 mAh/cm2 in half cells). This excellent cycling stability is ascribed to a stable cathode-electrolyte interphase, a highly distributed and interconnected electronic percolation network, and robust mechanical properties. High-quality images collected using plasma focused ion beam scanning electron microscopy (PFIB-SEM) provide additional insight into this behavior, with a complementary 2-D model illustrating how the electronic percolation network in the dry-coated electrodes more efficiently supports homogeneous electrochemical reaction pathways. These results strongly motivate that LNMO as a high voltage cobalt-free cathode chemistry combined with an energy-efficient dry electrode coating process opens the possibility for sustainable electrode manufacturing of cost-effective and high-energy-density cathode materials.

Solid-state batteries are a promising energy storage technology that can potentially offer both improved safety and energy density. The solid electrolyte is the defining feature and plays a significant role in the electrochemical performance of a solid-state cell, especially at room temperature. Herein, we report a series of glass-ceramic, sodium-deficient chloride solid electrolytes, NaxY0.25Zr0.75Cl3.75+x (0.25  x  0.875), possessing significantly improved ionic conductivities when compared to their stoichiometric counterpart, Na2.25Y0.25Zr0.75Cl6 (x = 2.25). By tuning both the sodium molar content and the sample’s crystallinity, the composition Na0.625Y0.25Zr0.75Cl4.375 (x = 0.625) was found to exhibit the highest Na+ conductivity of 0.4 mS cm−1 at room temperature. Furthermore, the relationship between composition, structure, and conductivity for these compositions in the NaCl−YCl3−ZrCl4 system was evaluated using a combination of X-ray diffraction (XRD), solid-state nuclear magnetic resonance spectroscopy (ss-NMR), and electrochemical impedance spectroscopy (EIS) techniques. Materials characterization reveals that sodium-deficiency (i.e., lower molar % of NaCl) results in reduced crystallinity and preferred occupancy of prismatic Na local environments. These combined factors contribute to a lower activation energy for Na+ hopping, an increased ionic conductivity, and improved electrochemical performance at both higher cycling rates and at room temperature.

All-solid-state batteries (ASSBs) are one of the most promising systems to enable long-lasting and thermally resilient next-generation energy storage. Ideally, these systems should utilize low-cost resources with reduced reliance on critical materials. Pursuing cobalt- and nickel-free chemistries, like LiFePO4 (LFP), is a promising strategy. Morphological features of LFP essential for improved electrochemical performance, are highlighted to elucidate the interfacial challenges when implemented in ASSBs, since adoption in inorganic ASSBs have yet to be reported. In this work, the compatibility of LFP with two types of solid-state electrolytes, Li6PS5Cl (LPSCl) and Li2ZrCl6 (LZC), are investigated. The potential existence of oxidative decomposition products is probed using a combination of structural, electrochemical, and spectroscopic analyses. Bulk and interfacial characterization reveal that the sulfide-based electrolyte, LPSCl decomposes into insulative products, and electrochemical impedance spectroscopy is used to quantify the resulting impedance growth. However, through utilization of the chloride-based electrolyte, LZC, high-rate and stable electrochemical performance is achieved at room temperature.

Hard carbon (HC) is an attractive anode material for grid-level sodium-ion batteries (NIBs) due to the widespread availability of carbon, its high specific capacity, and low electrochemical working potential. However, the issues of low first cycle Coulombic efficiency and poor rate performance of HC need to be addressed for it to become a practical long-life solution for NIBs. These drawbacks appear to be electrolyte dependent, since ether-based electrolytes can largely improve the performance compared with carbonate electrolytes. An explanation for the mechanism behind these performance differences is critical for the rational design of highly reversible sodium storage. Combining gas chromatography, Raman spectroscopy, cryogenic transmission electron microscopy, and X-ray photoelectron spectroscopy, this work demonstrates that the solid electrolyte interphase (SEI) is the key difference between ether- and carbonated-based electrolyte, which determines the charge transfer kinetics and the extent of parasitic reactions. Although both electrolytes show no residual sodium stored in the HC bulk structure, the uniform and conformal SEI formed by the ether-based electrolyte enables improved cycle efficiency and rate performance. These findings highlight a pathway to achieve long-life grid-level NIBs using HC anodes through interfacial engineering.

The development of silicon anodes for lithium-ion batteries has been largely impeded by poor interfacial stability against liquid electrolytes. Here, we enabled the stable operation of a 99.9 weight % microsilicon anode by using the interface passivating properties of sulfide solid electrolytes. Bulk and surface characterization, and quantification of interfacial components, showed that such an approach eliminates continuous interfacial growth and irreversible lithium losses. Microsilicon full cells were assembled and found to achieve high areal current density, wide operating temperature range, and high areal loadings for the different cells. The promising performance can be attributed to both the desirable interfacial property between microsilicon and sulfide electrolytes and the distinctive chemomechanical behavior of the lithium-silicon alloy.

Fluorinated graphite (CF x ) is a class of cathode materials with the high theoretical capacity (865 mAh g-1 in case of x=1) for primary (non-rechargeable) batteries. When using Li metal as the anode material, the system possesses a very low self-discharge rate (< 0.5% per year at 25 °C) compared to other current alternative chemistries. This system, with the proposed general governing reaction of CF x +Li→LiF+C, is one of the best candidates for a wide range of applications, such as implantable medical devices and equipment for extreme environment. Although the lithium fluorinated graphite system has been under investigation for a few decades, there is still a lack of fundamental understanding of the reaction mechanism in this system. Here, a multiscale investigation on the CFx discharge mechanism was performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography (TGC), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cross-sectional focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) were utilized to investigate this system. The results demonstrated that: (i) There is no lithium deposition or intercalation through the entire discharge. (ii) The CFx structure transforms to a hard-carbon like structure with less sp2 content by increasing depth of discharge. (iii) The crystalline LiF particles uniformly covered the layers of CFx structure with a size range of < 10 nm. A three-step discharge reaction mechanism is proposed in agreement with our electrochemical performances. This work deepens the understanding of CFx as a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance. Figure 1

Future rechargeable Li metal batteries (LMBs) require a rational electrolyte design to stabilizethe interfaces between the electrolyte and both the lithium metal anode and the high voltagecathode. This remains the greatest challenge in achieving high cycling performance inLMBs. We report an ether-aided ionic liquid electrolyte which offers superior Li metaldeposition, high voltage (5 V) stability and non-flammability. High performance cycling ofLiNi0.8Mn0.1Co0.1O2 (4.4 V) and LiNi0.6Mn0.2Co0.2O2 (4.3 V) cells is demonstrated with highcoulombic efficiency (>99.5%) at room temperature and elevated temperatures, even at highpractical areal capacity for the latter of 3.8 mAh/cm2 and with a capacity retention of 91% after100 cycles. The ether-ionic liquid chemistry enables desirable plated Li microstructures withhigh packing density, minimal ‘dead’ or inactive lithium formation and dendrite-free long-termcycling. Along with XPS studies of cycled electrode surfaces, we use molecular dynamicssimulations to demonstrate that changes to the electrolyte interfacial chemistry upon additionof DME plays a decisive role in the formation of a compact stable SEI.

Future rechargeable Li metal batteries (LMBs) require a rational electrolyte design to stabilizethe interfaces between the electrolyte and both the lithium metal anode and the high voltagecathode. This remains the greatest challenge in achieving high cycling performance inLMBs. We report an ether-aided ionic liquid electrolyte which offers superior Li metaldeposition, high voltage (5 V) stability and non-flammability. High performance cycling ofLiNi0.8Mn0.1Co0.1O2 (4.4 V) and LiNi0.6Mn0.2Co0.2O2 (4.3 V) cells is demonstrated with highcoulombic efficiency (>99.5%) at room temperature and elevated temperatures, even at highpractical areal capacity for the latter of 3.8 mAh/cm2 and with a capacity retention of 91% after100 cycles. The ether-ionic liquid chemistry enables desirable plated Li microstructures withhigh packing density, minimal ‘dead’ or inactive lithium formation and dendrite-free long-termcycling. Along with XPS studies of cycled electrode surfaces, we use molecular dynamicssimulations to demonstrate that changes to the electrolyte interfacial chemistry upon additionof DME plays a decisive role in the formation of a compact stable SEI.

Cation-disordered rock salt materials have attracted much interest as high energy density cathode materials due to their anionic electrochemical activity, providing them extra capacity, along with their lower cost. They are, however, still the subject of numerous studies as they suffer from poor cyclability and relatively slow kinetics compared to traditional intercalation materials. In this work, several important experimental considerations, that must be taken into account when studying Li-excess cation disordered rock salt cathode materials, are introduced. First, the key synthesis parameters were identified to enable a lower-temperature, morphology-controlled synthesis of the Li3NbO4-based disordered rock salt cathodes Li1.3TM0.4Nb0.3O2 (TM = Fe, Mn), using nano-sized precursors. After evaluating the influence of the morphology on the cyclability of the electrode, two key challenges that hinder the practical implementation of these systems are revealed – ambient air-induced surface contamination and electrolyte compatibility. Thermal gravimetric analysis and X-ray diffraction on the nano-sized cathodes confirmed that prolonged air exposure generates a large amount of surface species, responsible for the large decrease in the first discharge capacity. Moreover, the influence of the electrolyte on the evolution of the cathode–electrolyte interphase was investigated using X-ray photoelectron spectroscopy. The results show that cation-disordered rock salt cathodes go through significant Li-salt degradation and develop thick cathode–electrolyte interphase with the electrolytes compatible with Li-excess layered cathode materials Li[Li0.144Ni0.136Co0.136Mn0.544]O2, highlighting the importance of evaluating and finding compatible battery chemistries.

Lithium-air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium-oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium-oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium-air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium-oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

Electrocatalytic conversion of carbon dioxide (CO2) into energy-rich fuels is considered to be the most efficient approach to achieve a carbon neutral cycle. Transition-metal dichalcogenides (TMDCs) have recently shown a very promising catalytic performance for CO2 reduction reaction in an ionic liquid electrolyte. Here, we report that the catalytic performance of molybdenum disulfide (MoS2), a member of TMDCs, can be significantly improved by using an appropriate dopant. Our electrochemical results indicate that 5% niobium (Nb)-doped vertically aligned MoS2 in ionic liquid exhibits 1 order of magnitude higher CO formation turnover frequency (TOF) than pristine MoS2 at an overpotential range of 50–150 mV. The TOF of this catalyst is also 2 orders of magnitude higher than that of Ag nanoparticles over the entire range of studied overpotentials (100–650 mV). Moreover, the in situ differential electrochemical mass spectrometry experiment shows the onset overpotential of 31 mV for this catalyst, which is the ...

Lithium-CO

Hard carbon (HC) is an attractive anode material for sodium-ion batteries (NIBs) because it can be made from biomass or plastic, has a high capacity of ~300 mAh/g, and an extremely low average voltage near 0V. When fabricated with cathodes free of Li, Ni, and Co, NIBs using HC anodes are a promising approach for grid storage because they are energy-dense, sustainable, and have a low cost of energy. In order for these batteries to become a practical long-life solution, the issues of low first coulombic efficiency and poor rate performance of HC in conventional carbonate electrolytes need to be addressed. Two mechanisms that potentially cause these issues to occur are changes to the HC structure affecting sodium storage and the formation of the solid electrolyte interface (SEI). The proper selection of electrolyte is critical for controlling these mechanisms. To observe and characterize these mechanisms, we compared HC using a conventional carbonate electrolyte, 1M NaPF6 in propylene carbonate (PC), with a high performing glyme based electrolyte, 1M NaBF4 in tetraethylene glycol dimethyl ether (TEGDME). Compared to the poor rate capability of HC in PC electrolyte, HC in TEGDME electrolyte shows an excellent rate capability of ~265 mAh/g at C/20 and ~260 mAh/g at C/3. Titration gas chromatography and Raman spectroscopy were used to show that the HC with either electrolyte had the same sodium storage mechanism with no “stuck” sodium in the HC structure after the first cycle. These observations suggest that SEI formation is responsible for the irreversible capacity differences. The SEI formation was explored with scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). The PC electrolyte’s SEI is found to be thick, fluffy, irregular and composed of polyesters, alkyl carbonates, NaxPFyOz, and NaF. The TEGDME electrolyte’s SEI is found to be thin, conformal, uniform, and composed of polyethers, sodium alkoxides, NaxBFyOz, and NaF. Additionally, the PC electrolyte’s SEI is rate dependent with more unstable products formed at high rates whereas the TEGDME electrolyte’s SEI is not rate dependent. These findings show that HC anode’s rate capability is controlled by the quality of the SEI formed by the electrolyte rather than the HC material structure. This model of rate and electrolyte dependent SEI indicates that SEI engineering is a pathway to improve HC as an anode for long-life grid-level NIBs. Figure 1

Li-rich disordered rock salt (DRS) oxides are a promising class of cathode materials with the wide chemical space to be explored. The high capacity (>300mAh/g) of this class of material can be explained by the reversible redox chemistry of the oxide anions, which sets it apart from the conventional layered cathode materials that rely only on the transition metal redox. However, these materials suffer from poor ionic and electronic transport properties: Most previous studies report electrochemical performance at low current rate and elevated temperature. Even then, the particle size needs to be reduced to sub-micrometer size, often by high-energy ball milling, to get reasonable capacities. To mitigate this issue, we performed a detailed study of the synthesis of three different Nb-based Li-rich DRS materials - Li3NbO4, Li1.3Fe0.4Nb0.3O2, and Li1.3Mn0.4Nb0.3O2. Systematic evaluation shows that both the synthesis conditions and the reagents used have a large effect on the phase and morphology of the material synthetized, and therefore on its electrochemical performance. Without varying the synthesis method, the extent of cation ordering, the particle morphology, and the degree of elemental segregation can be controlled by a careful choice of the metal oxide precursors. This study helps the community to distinguish important synthesis criteria in order to design Li-rich DRS cathode materials with improved electrochemical performance.

Lithium-CO2 batteries are attractive energy-storage systems for fulfilling the demand of future large-scale applications such as electric vehicles due to their high specific energy density. However, a major challenge with Li-CO2 batteries is to attain reversible formation and decomposition of the Li2 CO3 and carbon discharge products. A fully reversible Li-CO2 battery is developed with overall carbon neutrality using MoS2 nanoflakes as a cathode catalyst combined with an ionic liquid/dimethyl sulfoxide electrolyte. This combination of materials produces a multicomponent composite (Li2 CO3 /C) product. The battery shows a superior long cycle life of 500 for a fixed 500 mAh g-1 capacity per cycle, far exceeding the best cycling stability reported in Li-CO2 batteries. The long cycle life demonstrates that chemical transformations, making and breaking covalent CO bonds can be used in energy-storage systems. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li2 CO3 provides the electronic conduction needed for the oxidation of Li2 CO3 and carbon to generate the CO2 on charge. This achievement paves the way for the use of CO2 in advanced energy-storage systems.

The optimization of traditional electrocatalysts has reached a point where progress is impeded by fundamental physical factors including inherent scaling relations among thermokinetic characteristics of different elementary reaction steps, non-Nernstian behavior, and electronic structure of the catalyst. This indicates that the currently utilized classes of electrocatalysts may not be adequate for future needs. This study reports on synthesis and characterization of a new class of materials based on 2D transition metal dichalcogenides including sulfides, selenides, and tellurides of group V and VI transition metals that exhibit excellent catalytic performance for both oxygen reduction and evolution reactions in an aprotic medium with Li salts. The reaction rates are much higher for these materials than previously reported catalysts for these reactions. The reasons for the high activity are found to be the metal edges with adiabatic electron transfer capability and a cocatalyst effect involving an ionic-liquid electrolyte. These new materials are expected to have high activity for other core electrocatalytic reactions and open the way for advances in energy storage and catalysis.