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All-solid-state Li-ion batteries (ASSBs) are considered as ideal next-generation energy storage devices owing to their safe operation and high energy densities. Recently, halide-based solid electrolytes (SEs) have come under the spotlight because of their wide electrochemical stability windows and high ionic conductivities. However, their usage as coating materials for cathodes is limited. To examine the wide electrochemical stability window of SEs for lithium-metal anodes and their interfacial stability with high-voltage cathodes, a systematic first-principles investigation of A-site cation and anion exchange in Li3MX6 (M: Lu, Sc, Bi, In, Y, Tm, Dy, Ho, Er, Tm, Sm, Tb; X: Br, Cl, and I) was conducted. The systematic analysis showed that the electrochemical behavior of chloride SEs can be modulated by mixing M3+ cations. Furthermore, the replacement of M3+ by Zr4+ and the anionic blending of Br with Cl, which exhibits a relatively high ionic conductivity, was also computed for comparison with the A-site cation-mixed halide electrolyte. Our computational work provides an overview of the evolution of lithium halide SEs in high-voltage ASSBs. [ABSTRACT FROM AUTHOR]

Computer-aided retrosynthetic planning for organic molecules, which is based on a large synthetic database, is a significant part of the recent development of autonomous robotic chemists. As in other AI fields, however, the class imbalance problem in the dataset affects the prediction performance of retrosynthetic paths. Here, we demonstrate that applying undersampling models to the imbalanced reaction dataset can improve the prediction of retrosynthetic templates for target molecules. We report improvements in the top-1 and top-10 prediction accuracies by 13.8% (13.1, 5.4%) and 8.8% (6.9, 2.4%) for undersampling based on the similarity (random, dissimilarity) clustering of molecular structures of products, respectively. These results demonstrate the importance of deep understanding of the statistical distribution, internal structure, and sampling for the training dataset. For practical applications, the target-oriented undersampling model is proposed and confirmed by the improved prediction performance of 9.3 and 4.2% for the top-1 and top-10 accuracies, respectively. [ABSTRACT FROM AUTHOR]

All-solid-state batteries (ASSBs) with inorganic solid electrolytes (SEs) have received much attention as future energy storage systems owing to their high energy densities and excellent safety. Sulfide-based SEs are considered promising because they exhibit greater ionic conductivities and mechanical softness than oxide-based SEs. In particular, argyrodite-type Li6PS5Cl with a high ionic conductivity of 3.0 × 10−3 S cm−1 offers new possibilities for realizing high-performance ASSBs. However, contact with moisture results in the evolution of H2S from Li6PS5Cl, which has hindered the scalable fabrication and practical application of Li6PS5Cl. To avoid this issue, we propose incorporating a zeolite, which can act as a scavenger for both toxic H2S gas and moisture, as a functional additive in Li6PS5Cl. We demonstrate that zeolite-embedded Li6PS5Cl exhibits greatly improved chemical stability and reduced H2S evolution upon storage in humid air (RH 50%), leading to a noticeable improvement in the cycle performance of ASSBs. This approach could resolve the technical issues associated with sulfide-based SEs toward commercial-scale implementation. [ABSTRACT FROM AUTHOR]

In this study, we propose a versatile design for metal–organic framework cathodes with the aim of improving the reversibility of Li–O2 and Li–O2/CO2 batteries. The porous nanoarchitecture of Co3O4-incorporated carbon wrapped with carbon nanotubes is beneficial for facilitating the reversible electrochemical reactions with O2 and CO2, ensuring long-term cycling performance. [ABSTRACT FROM AUTHOR]

Silicon oxides (SiOx) have been widely explored as high-capacity lithium storage materials for lithium ion batteries (LIBs) due to the enhanced stability of their cycling performance compared to other Si-based materials. However, these materials suffer from insufficient electrochemical performance and reliability for commercial use in LIBs. Since the electrochemical performance of SiOx relies on microstructures and chemical compositions, we propose a material layout design of a biphasic SiOx composite that can achieve synergy between two different types of SiOx materials to improve electrochemical performance. Taking advantage of the properties of each component, a biphasic SiOx composite composed of silicon monoxide (SiO) and Si nanocrystals embedded in SiOx (Si/SiOx) exhibits notably improved electrochemical performance and suppressed volume expansion during cycling. The proposed biphasic material exhibits a high reversible capacity of 966 mA h g−1 with excellent long-term cycle performance for up to 350 cycles. With a core–shell structure, the biphasic Si/SiOx–SiO composite also has excellent dimensional stability. This approach presents a promising way to produce highly reliable high-capacity anode materials with a low production cost for mass production. [ABSTRACT FROM AUTHOR]

The electro-reduction of battery electrolytes plays a critical role in the formation of solid–electrolyte interphase (SEI) layers on the surfaces of negative electrodes. These layers have a significant influence on the performance of rechargeable battery cells. Using ab initio molecular dynamics, we demonstrate the electro-reduction of mixture electrolytes computationally by adding a certain number of excess Li+ first to form the solvation structure and the same number of electrons later for reductive reactions. Our method enables direct observations of the ring opening of one cyclic carbonate followed by merging with another solvent molecule as well as gas generation. When we examined FEC- and EC-based electrolytes, we were able to observe the differences in terms of reaction products. In particular, the two gaseous products that are generated the most are in accordance with recent in situ gas measurements in the literature. The different reaction products of each electrolyte also match well with the SEI constituents reported experimentally. By tracing reaction pathways, we found that Li+ ions facilitate many otherwise difficult electrochemical reactions, presumably by lowering energy barriers. We also found that the excess Li+ forms cationic clusters of Li2PF6+, which enable the reductive decomposition of salt anions and which do not occur easily simply by increasing the electronic occupation. Based on the reaction products of FEC-based electrolytes, here we propose a possible mechanism of polymerization through aldehyde intermediates that are known to bond with surrounding radical anions. [ABSTRACT FROM AUTHOR]

A new nanoarchitecture approach based on metal–organic frameworks (MOF) is reported that can achieve high electrochemical energy storage via utilizing both electric double-layer supercapacitive and pseudocapacitive properties within a single nanoporous composite particle. Herein, a predesigned Co2+-excess bimetallic hybrid Co/Zn zeolitic imidazole framework was used to fabricate a composite containing N-doped nanoporous carbon with a rich carbon nanotube (CNT) content on particle surfaces without H2, with the carbon coexisting with Co nanoparticles (NPs) and Co3O4, through controlled carbonization at 800 °C and subsequent oxidation at 250–300 °C. Optimized nanoporous carbon composites were obtained by tracking the formation of Co3O4 and destruction of N-doped nanoporous carbon (NPC) via detailed X-ray diffraction and X-ray photoelectron spectroscopy analysis. The resulting material showed a high surface area of ∼202 m2 g−1 and included coexisting micro- and mesoporous N-doped carbon, CNTs, Co NPs, and Co3O4 (15 nm in size) after a thermal oxidation process in air at 250 °C for 5 h. Surprisingly, the as-prepared MOF-derived nanoarchitecture exhibited superior electrochemical storage performance, with a capacitance of 545 F g−1 within a wide potential window, achieving up to 320% enhanced capacitance compared to that of pristine nanoporous carbon, which is higher than those of most MOF-derived carbons reported so far. Our strategic nanoarchitecture design for MOFs offers a new opportunity for future applications in high performance energy storage systems. [ABSTRACT FROM AUTHOR]

A fundamental understanding of anomalous redox mechanisms in hexacyanometallate compounds, compared with conventional NaMO2 systems (M: transition metals), is presented based on first-principles calculations and experimental validations. From theoretical calculations, we identified low-spin and high-spin states of Fe ions coordinated by the cyanide group (–CN) with the same oxidation state (Fe2+) in Na2Fe2(CN)6. Considering the site dependency of d electronic spin configurations based on the crystal field theory (CFT) of transition metals (TMs), we calculated the thermodynamic mixing energy using Na2Fe2(CN)6 and Na2Mn2(CN)6 for obtaining a thermodynamically stable phase of Na2FeMn(CN)6. The phase stabilities of Na2Fe2−xMnx(CN)6 among many atomic configurations and lattice parameters originating from octahedral structures (i.e., Fe(CN)6 and Mn(NC)6) are highly dependent on the electronic structures of TMs with spin states. From partial density of states (PDOS) and spatial electron distributions, it was observed that Fe2+ in the low-spin state (t62g) and Mn2+ in the high-spin states (t32g and e2g) in the stable phase lead to higher redox potentials (∼3.55 V vs. Na/Na+) with the removal of Na+ as compared to that of Na2Fe2(CN)6. In addition, lattice parameters from x = 0 to x = 1 in Na2Fe2−xMnx(CN)6 are increased due to the larger ionic radius of Mn2+ in the high-spin states. On the other hand, Fe2+ in the high-spin states (t42g and e2g) and Mn2+ in the low-spin state (t52g) in the most unstable phase of Na2FeMn(CN)6 would have lower redox potentials. Based on the fundamental correlation between redox potentials and CFT with spin configurations of TMs, we suggest a material design concept for intercalation compounds with higher energy densities for rechargeable battery systems. [ABSTRACT FROM AUTHOR]

Solid electrolytes are key to the evolution of all-solid-state lithium batteries as next-generation energy storage systems. High ionic conductivity and stability of solid electrolytes are critical requirements for designing reliable all-solid-state lithium batteries. Perovskite-type lithium lanthanum titanates Li3xLa(2/3)−x□(1/3)−2xTiO3 (LLTOs) have received much attention as a potential inorganic solid electrolyte to replace current organic liquid electrolytes; however, the practical use of LLTOs is limited by their low total conductivity. With the aim of improving the ionic conductivity, we investigated a correlation between the microstructures and Li+ conducting properties of LLTO perovskites. We show that the total conductivity of LLTOs is dominated by the domain boundary resistance, and the synthesis condition of the electrolyte (sintering temperature and Li concentration) has a crucial role in modifying the microstructure and composition of the domain boundaries to significantly reduce the boundary resistance. By controlling the sintering temperature and Li content, in particular, a total Li+ conductivity as high as 4.8 × 10−4 S cm−1 can be achieved at room temperature. The findings of this study would be essential in understanding Li+ conducting behaviors and in developing highly conductive perovskite-type LLTO solid electrolytes. [ABSTRACT FROM AUTHOR]

The power characteristics of lithium-ion batteries (LIBs) are crucial for the advent of commercialized, high-power applications, such as electric vehicles. Through both first-principles multiscale simulations and experiments, here, we present fundamental understanding on the power characteristics of the high-voltage spinel cathode correlated with its elastic softness and phase transformation in nanodomains for high-power LIBs. Atomic models of LiNi0.5Mn1.5O4 and LiNi0.5Mn1.5−xTixO4 are developed for multiscale phase field modeling based on structural information for the as-prepared nanopowders. The combined computational and experimental investigations suggest that the thermodynamic phase stability of LiNi0.5Mn1.5O4 can be effectively enhanced by the incorporation of Ti into the structure without any change to the redox mechanism. Ti incorporation provides a faster ionic mobility and the improved phase stability because of the reinforced Ti4+–O bonds. Based on the multiscale phase transformation kinetics, LiNi0.5Mn1.5−xTixO4 exhibits an enhanced elastic softness and slower phase separation than LiNi0.5Mn1.5O4 in the nanodomain during Li+ insertion and extraction. Such characteristics are mainly responsible for the improved electrochemical performance at higher current rates, as confirmed by electrochemical experiments. This fundamental understanding of the power characteristics with respect to the correlations with elastic softness and phase transformation will provide a guideline to develop and design advanced materials for high-power LIBs. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNT) grown on nanoporous carbon (NPC), which yields coexisting amorphous and graphitic nanoarchitectures, have been prepared on a large scale from zeolitic imidazolate framework (ZIF) by introducing bimetallic ions (Co2+ and Zn2+). Interestingly, the hybrid Co/Zn-ZIF-derived NPC showed rich graphitic CNTs on the surface. This NPC was utilized for a coin-type supercapacitor cell with an aqueous electrolyte, which showed enhanced retention at high current density and good stability over 10 000 cycles. [ABSTRACT FROM AUTHOR]

Chemical databases store information such as molecular formulas, chemical structures, and the physical and chemical properties of compounds. Although the massive databases of organic compounds exist, the search of target materials is constrained by a lack of physical and chemical properties necessary for specific applications. With increasing interest in the development of energy storage systems such as high-voltage rechargeable batteries, it is critical to find new electrolytes efficiently. Here we build a search map to screen organic additives and solvents with novel core and functional groups, and thus establish a database of electrolytes to identify the most promising electrolyte for high-voltage rechargeable batteries. This search map is generated from MAssive Molecular Map BUilder (MAMMBU) by combining a high-throughput quantum chemical simulation with an artificial neural network algorithm. MAMMBU is designed for predicting the oxidation and reduction potentials of organic compounds existing in the massive organic compound database, PubChem. We develop a search map composed of ∼1 000 000 redox potentials and elucidate the quantitative relationship between the redox potentials and functional groups. Finally, we screen a quinoxaline compound for an anode additive and apply it to electrolytes and improve the capacity retention from 64.3% to 80.8% near 200 cycles for a lithium ion battery in experiments. [ABSTRACT FROM AUTHOR]

Lithium–air battery (LAB) technology is currently being considered as a future technology for resolving energy and environmental issues. During the last decade, much effort has been devoted to realizing state-of-the-art LABs, and remarkable scientific advances have been made in this research field. Although LABs possess great potential for efficient energy storage applications, there are still various technical limitations to be overcome before the full transition. It has been well recognized that the battery performance of LABs is mainly governed by the electrochemical reactions that occur on the surface of the cathode. Thus, the rational design of highly reliable cathodes is essential for building high-performance LABs. In this respect, we introduce recent advances in the development of LABs, particularly focusing on the cathodes based on a fundamental understanding of Li–O2 electrochemistry. Furthermore, we review the remaining technical challenges in order to formulate a strategy for future research and consolidate Li–O2 electrochemistry for successful implementation of LABs in the near future. [ABSTRACT FROM AUTHOR]

For large-scale energy storage applications requiring high energy density, the development of Li-rich oxides with enhanced cyclic stabilities during high-voltage operations and large specific capacities is required. In this regard, high-Mn, Li-rich oxides (HMLOs; xLi2MnO3 (1 −x)LiNi1/3Co1/3Mn1/3O2 at x ＞ 0.5) warrant an in-depth study because of their good cyclic performance at high operating voltages and potentially large specific capacities. Here, to understand the synergistic effects and enhanced cyclic stability of HMLOs, mechanically blended HMLO (m-HMLO) and chemically bonded HMLO (c-HMLO) were prepared and investigated. c-HMLO exhibits relatively high reaction voltages, large specific capacities, and enhanced cyclic stabilities (∼99%) at a high operating voltage (∼4.8 V vs. Li/Li+) compared with m-HMLO. First-principles calculations with electronic structure analysis were performed using an atomic model developed by Rietveld refinement using as-synthesised c-HMLO. The redox mechanisms of Ni, Co, and Mn ions were determined via the partial density of states of the ground states predicted using the cluster expansion method, which elucidates that LiNi1/3Co1/3Mn1/3O2 stabilises the transition metal (TM) layer of Li2MnO3 and separates Li delithiation potentials in Li2MnO3 in the HMLO. Kinetic analyses including electronic structures revealed that the interlayer migration of TMs from the TM layer to the Li layer depends on the crystal field stabilisation. Thus, TMs with reduced character in the tetrahedral sites than the octahedral sites owing to the effects of crystal field stabilisation, such as Ni ions, in HMLOs would face a higher interlayer migration barrier, impeding phase transformation into spinel phases. Furthermore, Cu ions could constitute a doping source for HMLOs to improve the material’s cyclic stability through this mechanism. These characteristics may be widely applied to explain experimental phenomena and improve the properties of cathode materials for Li-ion batteries. [ABSTRACT FROM AUTHOR]

Transition metal oxides possessing two kinds of metals (denoted as AxB3−xO4, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe, etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs). The spinel-type transition metal oxides exhibit outstanding electrochemical activity and stability, and thus, they can play a key role in realising cost-effective and environmentally friendly ESSs. Moreover, porous nanoarchitectures can offer a large number of electrochemically active sites and, at the same time, facilitate transport of charge carriers (electrons and ions) during energy storage reactions. In the design of spinel-type transition metal oxides for energy storage applications, therefore, nanostructural engineering is one of the most essential approaches to achieving high electrochemical performance in ESSs. In this perspective, we introduce spinel-type transition metal oxides with various transition metals and present recent research advances in material design of spinel-type transition metal oxides with tunable architectures (shape, porosity, and size) and compositions on the micro- and nano-scale. Furthermore, their technological applications as electrode materials for next-generation ESSs, including metal–air batteries, lithium-ion batteries, and supercapacitors, are discussed. [ABSTRACT FROM AUTHOR]

The vanadium redox flow battery, which was first suggested by Skyllas-Kazacos and co-workers in 1985, is an electrochemical storage system which allows energy to be stored in two solutions containing different redox couples. Unlike commercially available batteries, all vanadium redox flow batteries have unique configurations, determined by the size of the electrolyte tanks. This technology has been proven to be an economically attractive and low-maintenance solution, with significant benefits over the other types of batteries. Moreover, the soaring demand for large-scale energy storage has, in turn, increased demands for unlimited capacity, design flexibility, and good safety systems. This work reviews and discusses the progress on electrodes and their reaction mechanisms as key components of the vanadium redox flow battery over the past 30 years. In terms of future outlook, we also provide practical guidelines for the further development of self-sustaining electrodes for vanadium redox flow batteries as an attractive energy storage system. [ABSTRACT FROM AUTHOR]

As a promising hybrid energy storage system, lithium ion capacitors (LICs) have been intensively investigated regarding their practical use in various applications, ranging from portable electronics to grid support. The asymmetric LIC offers high-energy and high-power densities compared with conventional energy storage systems such as electrochemical double-layer capacitors (EDLCs) and lithium ion batteries (LIBs). To enable suitable operation of the LIC, the negative electrode should be pre-lithiated prior to cell operation, which is regarded as a key technology for developing self-sustainable LICs. In this work, we have demonstrated the potential use of Li6CoO4 as an alternative lithium source to metallic lithium. A large amount of Li+ can be electrochemically extracted from the structure incorporated into the positive electrode via a highly irreversible process. Most of the extracted Li+ is available for pre-lithiation of the negative electrode during the first charge. This intriguing electrochemical behaviour of Li6CoO4 is suitable for providing sufficient Li+ to the negative electrode. To obtain a fundamental understanding of this system, the electrochemical behaviour and structural stability of Li6CoO4 is thoroughly investigated by means of electrochemical experiments and theoretical validation based on first principles calculations. [ABSTRACT FROM AUTHOR]

For the over-lithiated-oxides (OLOs), a composite of layered Li2MnO3 and LiMO2 (M = Mn, Co, Ni), the Li2MnO3 part is not stable after the 1st charge–discharge cycle and partly transforms into layered LiMnO2, which in practice indicates that the phase used is actually a mixture of both Li2MnO3 and LiMnO2. In the present work, the influence of 10 cationic (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, and Al) and 2 anionic (N and F) dopants on the phase stability, redox potential, ionic and electronic conductivity of both Li2MnO3 and LiMnO2 is investigated in detail using density functional theory. The calculations show that all the cationic dopants and F can be thermodynamically stable in the layered structures. The redox potential of both oxides is quite sensitive to some of the dopants, like V, Nb, and Ru, due to the appearance of gap states introduced by those dopants. The Jahn–Teller effect has a strong influence on the Li vacancy diffusion behavior in both LiMnO2 and its doped phases. Li vacancy diffusion behavior in Li2MnO3, including both interlayer and intralayer pathways, is relatively more complex and some dopants like Mg, Ti, Nb, and Ru can decrease the barriers of the diffusion paths. The calculations also show the evidence of hole polaron formation in LiMnO2 and electron polaron formation in Li2MnO3 which should be the reason why these phases have low electronic conductivities. Based on these findings, possible ways to improve the electronic conductivity through the doping process are discussed. [ABSTRACT FROM AUTHOR]

Lithium-rich oxide materials are promising candidates for high-energy lithium ion batteries, but currently have critical challenges of poor cycle performance and voltage drop induced by undesirable phase transformation. To resolve these problems, it is necessary to identify the origins and mechanism of phase transformation in Li2MnO3, a key component of Li-rich oxides. In this work, the phase transformation of bulk Li2MnO3 is investigated by thermodynamic and kinetic approaches based on first-principles calculations and validated by experiments. Using the calculated thermodynamic energies, the most stable structure is determined as a function of Li extraction for Li2−xMnO3: monoclinic (x = 0.0–0.75), layered-like (x = 1.0–1.25), and spinel-like (x = 1.5–2.0) structures. The phase transformation becomes kinetically possible for Li2−xMnO3 (x ＞ 1.0). Atomic scale origins and the mechanism of phase transformation are elucidated by the thermodynamically stable and kinetically movable tetrahedral coordination of Mn4+ in the transition state. These theoretical observations are validated by ex situ X-ray photoelectron spectroscopy combined with electrochemical experiments for Li2−xMnO3 with various Li contents upon cycling. The mechanistic understanding from theoretical calculations and experimental observations is expected to provide a fundamental solution and guidelines for improving the electrochemical performance of Li-rich oxides and, by extension, the battery performance. [ABSTRACT FROM AUTHOR]

We have screened 142 cyclic organic compounds in search of novel functional additives and nonaqueous solvents for use in lithium-ion batteries through the use of ab initio calculations, and have determined redox potentials for all molecules. We have estimated the range of variation in oxidation potentials through heteroatom replacement and structure modification. By analyzing the oxidative properties of these compounds, we have shown that substituted heteroatoms and isomers in cyclic organic molecules can induce large variations of oxidation potentials more than 2.3 V. Calculations of reduction potentials show that the substituted heteroatoms, isomers, and the number of double bonds in cyclic organic molecules can change reduction potentials more than 1.7 V. Additionally, we have identified seventeen and twelve compounds that could serve as additives in eliciting film formation on cathodes and anodes, respectively. We have also identified five compounds that could function in the overcharge protection of over-lithiated layered oxide cathodes. Finally, we have identified five compounds that could serve as electrochemically stable solvents for high-voltage (＞6 V vs. Li/Li+) applications. These inductive screenings and their analyses and findings extend our empirical knowledge into quantitative estimation in the design of materials. [ABSTRACT FROM AUTHOR]

5-Hydroxy-1H-indazole (HI) is investigated as an effective film-forming additive for an over-lithiated layered oxide (OLO) positive electrode. The protective film that is generated by oxidative decomposition of the additive (HI) prior to the carbonate electrolyte is thin and less resistive. As a result, a full cell comprised of OLO/graphite in the HI-added electrolyte gives a better cycling performance. [ABSTRACT FROM AUTHOR]

We have studied native point defects in the layered oxides of LiNi1/3Co1/3Mn1/3O2 and Li2MnO3, the promising cathode materials for rechargeable Li-ion batteries for the application of high lithium capacity, by performing first-principles calculations. Through the calculations of formation energies for native point defects in LiNi1/3Co1/3Mn1/3O2, it was found that the Ni vacancy and the LiNi antisite are the most dominant defects, which shows a good agreement with previous experiments. Contrary to the previous experimental analysis, however, the NiLi antisite defect is not dominant, even though both Ni and Li ions have a similar ionic radius. In Li2MnO3, the LiMn antisite defect is dominant under the O-rich and Mn-poor condition. In contrast, the MnLi antisite, the Li vacancy in the Li layer, and the oxygen vacancy are dominant at the chemical potential of the boundary in equilibrium with Li2O. To enhance the migration of Li ions for achieving high power, the experimental syntheses of LiNi1/3Co1/3Mn1/3O2 under the Ni-rich condition and Li2MnO3 under O-rich and Mn-poor condition were suggested. For Li2MnO3 suffering from poor electronic conductivity, it was found that the electronic conductivity can be increased by p- and n-type extrinsic doping under the O-rich and Mn-poor condition and the chemical potential of the boundary coexisting with Li2O, respectively, without losing the Li ion conductivity. [ABSTRACT FROM AUTHOR]

We introduce a ceramic composite separator prepared by coating moisturized ZrO2 nanoparticles with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-12wt%HFP) copolymer on a polyethylene separator. The effect of moisturized ZrO2 nanoparticles on the morphology and the microstructure of the polymeric coating layer is investigated. A large number of micropores formed around the embedded ZrO2 nanoparticles in the coating layer as a result of the phase inversion caused by the adsorbed moisture. The formation of micropores highly affects the ionic conductivity and electrolyte uptake of the ceramic composite separator and, by extension, the rate discharge properties of lithium ion batteries. In particular, thermal stability of the ceramic composite separators coated with the highly moisturized ZrO2 nanoparticles (a moisture content of 16 000 ppm) is dramatically improved without any degradation in electrochemical performance compared to the performance of pristine polyethylene separators. [ABSTRACT FROM AUTHOR]

A structured SnO2–reduced graphene oxide (RGO) nanocomposite has been synthesized with SnO2 nanoparticles (∼5 nm) anchored on a RGO framework. It has been successfully applied as an anode material in sodium-ion batteries. The electrode delivers a reversible Na-storage capacity of 330 mA h g−1 with an outstanding capacity retention of 81.3% over 150 cycles. Moreover, it possesses a relatively good rate capability, exhibiting a capacity retention of 25.8% at high rate (1000 mA h g−1). With its combined advantages of low cost and environmental benignity, the SnO2–RGO nanocomposite would be a promising anode for Na-ion batteries. [ABSTRACT FROM AUTHOR]

A new chemical approach for obtaining excellent cycleability of natural graphite is designed and introduced for use as an anode in lithium ion batteries. Here, we evaluate the electrochemical properties of natural graphite after surface modification with ammonium hexafluorophosphate (NH4PF6) to elucidate a correlation between surface structure and its electrochemical performance. The outstanding cyclic retention of 94.9% was obtained by NH4PF6at the fiftieth cycle, even without the functional additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Such improvement could be attributed to the introduction of phosphorus into the surface of natural graphite. The electrochemical measurements combined with structural analyses indicate that the phosphorus incorporation could make the surface more stable and reinforce the SEI during cycles. Our findings indicate that surface modification by phosphorus incorporation is effective to modify the physicochemical properties of the SEI and improve the electrochemical properties of natural graphite. [ABSTRACT FROM AUTHOR]

A layered oxide solid solution of LiMeO2and Li2MnO3(Me = Ni, Co, Fe, etc.), represented by the general formula Li[Li1−x−yMexMny]O2, is being considered a promising cathode for advanced lithium-ion batteries owing to its high capacity. Here, the surface of high-voltage oxide cathode, specifically Li[Li0.167Ni0.233Co0.100Mn0.467Mo0.033]O2, is modified with Al2O3and AlPO4to address critical issues relating to safety and stability during cycling. Using in situmeasurement of internal cell pressure, we demonstrate that the oxygen gas evolution upon high voltage charging is serious enough to raise a safety issue in practical batteries, but the problem can be greatly mitigated by surface modification. Furthermore, surface modification effectively prevents transition metal ions from leaching out of the electrode during cycling at elevated temperatures. The in-depth structural and electrochemical analyses indicate that in addition to the coated Al2O3and AlPO4species, Al3+ions incorporated into the transition metal layers modify the surface structure and play a crucial role in improving safety and stability. Our experimental findings provide a direction to future developments of high capacity electrodes and batteries that are tolerant to high-voltage charging and high-temperature environments. [ABSTRACT FROM AUTHOR]

A VOx-impregnated oxide cathode for lithium ion batteries exhibits a substantial drop in oxygen evolution during high voltage operation. An electrolyte was found to catalyze the gas evolution, and the VOxlayer could protect the cathode oxide surface from the electrolyte and stabilize the surface oxide ions during their electrochemical oxidation. [ABSTRACT FROM AUTHOR]

Correction for ‘CNTs grown on nanoporous carbon from zeolitic imidazolate frameworks for supercapacitors’ by Jeonghun Kim et al., Chem. Commun., 2016, 52, 13016–13019. [ABSTRACT FROM AUTHOR]

In this study, we propose a versatile design for metal-organic framework cathodes with the aim of improving the reversibility of Li-O 2 and Li-O 2 /CO 2 batteries. The porous nanoarchitecture of Co 3 O 4 -incorporated carbon wrapped with carbon nanotubes is beneficial for facilitating the reversible electrochemical reactions with O 2 and CO 2 , ensuring long-term cycling performance.

For large-scale energy storage applications requiring high energy density, the development of Li-rich oxides with enhanced cyclic stabilities during high-voltage operations and large specific capacities is required. In this regard, high-Mn, Li-rich oxides (HMLOs; xLi2MnO3 (1 - x)LiNi1/3Co1/3Mn1/3O2 at x > 0.5) warrant an in-depth study because of their good cyclic performance at high operating voltages and potentially large specific capacities. Here, to understand the synergistic effects and enhanced cyclic stability of HMLOs, mechanically blended HMLO (m-HMLO) and chemically bonded HMLO (c-HMLO) were prepared and investigated. c-HMLO exhibits relatively high reaction voltages, large specific capacities, and enhanced cyclic stabilities (∼99%) at a high operating voltage (∼4.8 V vs. Li/Li(+)) compared with m-HMLO. First-principles calculations with electronic structure analysis were performed using an atomic model developed by Rietveld refinement using as-synthesised c-HMLO. The redox mechanisms of Ni, Co, and Mn ions were determined via the partial density of states of the ground states predicted using the cluster expansion method, which elucidates that LiNi1/3Co1/3Mn1/3O2 stabilises the transition metal (TM) layer of Li2MnO3 and separates Li delithiation potentials in Li2MnO3 in the HMLO. Kinetic analyses including electronic structures revealed that the interlayer migration of TMs from the TM layer to the Li layer depends on the crystal field stabilisation. Thus, TMs with reduced character in the tetrahedral sites than the octahedral sites owing to the effects of crystal field stabilisation, such as Ni ions, in HMLOs would face a higher interlayer migration barrier, impeding phase transformation into spinel phases. Furthermore, Cu ions could constitute a doping source for HMLOs to improve the material's cyclic stability through this mechanism. These characteristics may be widely applied to explain experimental phenomena and improve the properties of cathode materials for Li-ion batteries.

We have studied native point defects in the layered oxides of LiNi1/3Co1/3Mn1/3O2 and Li2MnO3, the promising cathode materials for rechargeable Li-ion batteries for the application of high lithium capacity, by performing first-principles calculations. Through the calculations of formation energies for native point defects in LiNi1/3Co1/3Mn1/3O2, it was found that the Ni vacancy and the LiNi antisite are the most dominant defects, which shows a good agreement with previous experiments. Contrary to the previous experimental analysis, however, the NiLi antisite defect is not dominant, even though both Ni and Li ions have a similar ionic radius. In Li2MnO3, the LiMn antisite defect is dominant under the O-rich and Mn-poor condition. In contrast, the MnLi antisite, the Li vacancy in the Li layer, and the oxygen vacancy are dominant at the chemical potential of the boundary in equilibrium with Li2O. To enhance the migration of Li ions for achieving high power, the experimental syntheses of LiNi1/3Co1/3Mn1/3O2 under the Ni-rich condition and Li2MnO3 under O-rich and Mn-poor condition were suggested. For Li2MnO3 suffering from poor electronic conductivity, it was found that the electronic conductivity can be increased by p- and n-type extrinsic doping under the O-rich and Mn-poor condition and the chemical potential of the boundary coexisting with Li2O, respectively, without losing the Li ion conductivity.

We introduce a ceramic composite separator prepared by coating moisturized ZrO2 nanoparticles with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-12wt%HFP) copolymer on a polyethylene separator. The effect of moisturized ZrO2 nanoparticles on the morphology and the microstructure of the polymeric coating layer is investigated. A large number of micropores formed around the embedded ZrO2 nanoparticles in the coating layer as a result of the phase inversion caused by the adsorbed moisture. The formation of micropores highly affects the ionic conductivity and electrolyte uptake of the ceramic composite separator and, by extension, the rate discharge properties of lithium ion batteries. In particular, thermal stability of the ceramic composite separators coated with the highly moisturized ZrO2 nanoparticles (a moisture content of 16 000 ppm) is dramatically improved without any degradation in electrochemical performance compared to the performance of pristine polyethylene separators.

A new approach for enhancing the electrochemical performance of carbon felt electrodes by employing non-precious metal oxides is designed. The outstanding electro-catalytic activity and mechanical stability of Mn(3)O(4) are advantageous in facilitating the redox reaction of vanadium ions, leading to efficient operation of a vanadium redox flow battery.

A practical route is introduced for synthesizing a sulfur-impregnated graphene composite as a promising cathode material for lithium-sulfur batteries. Sulfur particles with a size of a few microns are successfully grown in the interior spaces between randomly dispersed graphene sheets through a heterogeneous crystal growth mechanism. The proposed route not only enables the control of the particle size of active sulfur but also affords quantitative yields of composite powder in large quantities. We investigate the potential use of the sulfur-impregnated graphene composite as a cathode material owing to its advantages of confining active sulfur, preventing the dissolution of soluble polysulfides, and providing sufficient electrical conduction. A high discharge capacity of 1237 mA h g(-1) during the first cycle and a good cyclic retention of 67% after 50 cycles are attained in a voltage range of 1.8-2.6 V vs. Li/Li(+). These results emphasize the importance of tailoring cathode materials for improving the electrochemical properties of lithium-sulfur batteries. Our results provide a basis for further investigations on advanced lithium batteries.

A VO(x)-impregnated oxide cathode for lithium ion batteries exhibits a substantial drop in oxygen evolution during high voltage operation. An electrolyte was found to catalyze the gas evolution, and the VO(x) layer could protect the cathode oxide surface from the electrolyte and stabilize the surface oxide ions during their electrochemical oxidation.

When the electrode is specifically designed by impregnation with an electronic and ionic mixed-conductor, improvement in the electrochemical properties was observed. The presence of an active redox center may contribute to the enhancement of the surface electronic/ionic transport properties by enhancing electrical connection and isotropic Li(+) ion transport.