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All-solid-state Li-metal batteries (ASLMBs) have the potential to outperform conventional Li-ion batteries in terms of high energy density and safety; however, their applications are challenged by the dendrite-related short circuit. Therefore, it is imperative to understand the mechano-electro-chemo behavior of Li. For the first time, we nondestructively visualize the Li behavior in ASLMBs through operando neutron imaging and X-ray computed tomography (XCT). The 2D neutron radiography tracks the real-time Li evolutions before and after the "soft short". The 3D neutron tomography evidences the Li-metal deformation, and XCT provides 3D views of the battery after the "soft short". Despite "soft short", our observation indicates that Faradaic processes persist. Meanwhile, the coupling of stacking pressure and plating-induced stress triggers the Li-metal deformation toward the current collector and the SE, which results in the "soft short". This work inspires future research on stabilizing the Li metal in ASLMBs from the mechano-electro-chemo aspect.

Photonic curing was explored as a rapid method for producing glassy carbon coatings, reducing processing time from ~ 20 h for conventional thermal processing down to ~ 1 min. A resole-type thermoset polymer resin coated on steel foil was used as a precursor, placed in a nitrogen purged container and exposed to high energy light (~ 27 J/cm2 per pulse for up to 20 pulses). Comparison samples were produced at 800 °C using a conventional nitrogen purged thermal route. For both photonic and conventionally produced coatings, Raman spectroscopy and primary peak XPS data showed sp2 bonded carbon, indicative of bulk glassy carbon. This transformation evolved with increasing number of pulses, and therefore amount of energy transferred to the coating. The produced coatings were resilient, highly smooth, with no evidence of surface defects. XPS analysis indicated greater sp3 content at the immediate surface (5–10 nm) for photonic cured carbon compared with thermally cured carbon, likely due to the local environment (temperature, atmosphere) around the surface during conversion. The ability to rapidly manufacture glassy carbon coatings provides new opportunities to expand the window of applications of glassy carbons in coatings towards large-scale high volume applications.

Conventional ion-selective membranes, that is ion-exchange and porous membranes, are unable to perform high conductivity and selectivity simultaneously due to the contradictions between their ion selecting and conducting mechanisms. In this work, a bifunctional ion-selective layer is developed via the combination of nanoporous boron nitride (PBN) and ion exchange groups from Nafion to achieve high ion conductivity through dual ion conducting mechanisms as well as high ion selectivity. A template-free method is adopted to synthesize flake-like PBN, which is further enmeshed with Nafion resin to form the bifunctional layer coated onto a porous polyetherimide membrane. The double-layer membrane exhibits excellent ion selectivity (1.49 × 10

The present study describes a template-free single step carbonization route to prepare hierarchically structured nitrogen-doped carbon materials (NCMs) by using an organic ionic dye (OID), ammonium purpurate (murexide). These NCMs exhibited moderate specific surface area (307 m2 g−1 for NCM(MDE)-900) and hierarchical macro/meso/microporous structures with abundant nitrogenous functionalities that contributed towards the high specific capacitance displayed by pseudocapacitive contribution. In particular, the NCM(MDE)-800 displayed superior specific capacitance (222 F g−1 at 3 A g−1) and excellent cyclic stability of ∼10 000 cycles at 10 A g−1 in 1 M 1.0 M H2SO4(aq). The material prepared at higher temperature, viz. NCM(MDE)-900, exhibited high rate capability at 50 A g−1, which is 92% of their specific capacitances at 10 A g−1. Further systematic investigations of NCM(MDE)-800 in three different electrolytes, viz. 1.0 M H2SO4(aq), 6 M KOH(aq) and 0.5 M Na2SO4(aq), revealed that 1.0 M H2SO4(aq) is a promising electrolyte for achieving good specific capacitance, high capacitive retention and long term cyclic stability, which might have its origins in the formation of ionic interactions between the active protons in 1.0 M H2SO4(aq) and the alpha carbon atoms with Lewis basic character next to the nitrogen in these NCMs.

Lithium-substituted 0.95[0.94(Bi0.5Na(0.5–x)Lix)TiO3–0.06BaTiO3]–0.05CaTiO3 materials include the polar rhombohedral R3c and the weakly polar tetragonal P4bm phases. On increasing lithium content, the (R3c/P4bm) phase ratio decreased, while the rhombohedral and tetragonal lattice distortions remained the same. The temperature corresponding to the shoulder in the dielectric permittivity shows no clear shift with respect to lithium substitution because of the rhombohedral distortion remaining constant. Electrical poling produced an increase of the rhombohedral phase fraction together with a rise of the rhombohedral and tetragonal distortion. This confirmed the occurrence of a phase transition from the weakly polar to the polar phase during electrical poling. Four peaks found in the current–electric field (I–E) loops are related to reversible electric field induced transitions. By studying the temperature dependence of the current peaks in the I–E loops, it was found that the minimum temperature where these electric field induced transitions take place decreases with increasing lithium substitution.

The booming development of electric vehicles (EVs) raised concerns about sustainability of Li-ion batteries (LIBs). Some of their constituents, such as Li and Co, are of scarce and highly localised resources. Furthermore, LIB’s building materials are difficult to recycle raising questions on the sustainability of the technology. These issues inspired research on chemistries based on more abundant elements, i.e. Na, Mg or Ca. Among them the most promising are sodium-ion batteries (SIBs), which are currently heavily researched as a viable and sustainable alternative to LIBs for medium to large scale energy storage applications. The mostly researched electrode materials for SIBs are hard carbons for anode and intercalation compounds for cathodes. The latter contain transition metals (including cobalt) and share the same concerns as cathode materials for LIBs. Additionally, having in mind recyclability problems of LIBs, it is necessary to take the circular economy approach when designing new technologies such as Na-ion batteries. Therefore, more sustainable and greener materials are needed. A promising solution is the use of carbon as an active electrode material. Carbonaceous materials are inexpensive, environmentally friendly and highly conductive. So called ‘dual carbon’ batteries utilise carbon for both electrodes – in case of LIBs it’s usually graphite for cathode and anode.1 Literature on this field regarding SIBs is sparse, particularly when it comes to electrochemical mechanisms and full cells performance. For instance Fan et al. reported on soft carbon-graphite Na-ion full cell with remarkable long cycle life.2 However, graphite cathode works via anion intercalation mechanism, which delivered small capacity of around 40 mAh g-1 in a full cell. Recently Ali et al. reported on electrochemical performance of reduced graphene oxide (rGO) as a suitable cathode for SIBs3. The cathode showed high specific capacity of 235 mAh g-1 and stable behaviour over 1000 cycles. Nevertheless, the exact electrochemical energy storage mechanism in rGO is unclear and its performance in a full cell wasn’t yet verified. In this work we investigated electrochemical behaviour of reduced graphene oxide based cathode for SIBs. Techniques such as in situ Raman spectroscopy and X-ray Pair Distribution Function (PDF) provided insightful look into electrochemical reactions of rGO cathodes for SIBs. It has been concluded that processes responsible for high gravimetric capacity are surface Faradaic reactions between the sodium ions and the functional groups, as well as the bipolar behaviour of rGO resulting in capacitive storage of anions from electrolyte salt (Figure 1a). Furthermore, as a proof-of-concept a full cell with the rGO cathode and hard carbon (HC) as anode was tested. It showed high energy density of 80 Wh kg-1 and outstanding stability over 1000 cycles (Figure 1b), proving that rGO is a viable SIBs cathode material candidate. Replacing expensive transition metal based oxides with carbonaceous cathodes would solve sustainability and environmental impact concerns and lead to significant reduction of overall SIBs manufacturing costs. Placke, A. Heckmann, R. Schmuch, P. Meister, K. Beltrop and M. Winter, Joule, 2018, 1–23. Fan, Q. Liu, S. Chen, Z. Xu and B. Lu, Adv. Energy Mater., 2017, 7, 1602778. G. Ali, A. Mehmood, H. Y. Ha, J. Kim and K. Y. Chung, Sci. Rep., 2017, 7, 40910. Figure 1

In 0.95[0.94Bi0.5Na0.5TiO3-0.06BaTiO3]-0.05CaTiO3 ceramics, the temperature TS (dielectric permittivity shoulder at about 125 °C) represents a transition between two different thermally activated dielectric relaxation processes. Below TS, the approximately linear decrease of the permittivity with the logarithm of frequency was attributed to the presence of a dominant ferroelectric phase. Above TS, the permittivity shows a more complicated dependence of the frequency and Raman modes indicate a sudden increase in the spatial disorder of the material, which is ascribed to the presence of a nonpolar phase and to a loss of interaction between polar regions. From 30 to 150 °C, an increase in the maximum polarization with increasing temperature was related to three possible mechanisms: polarization extension favoured by the simultaneous presence of polar and non-polar phases; the occurrence of electric field-induced transitions from weakly polar relaxor to ferroelectric polar phase; and the enhanced polarizability of the crystal structure induced by the weakening of the Bi-O bond with increasing temperature. The occurrence of different electric field induced polarization processes with increasing temperature is supported by the presence of additional current peaks in the current-electric field loops.