In organic solar cells with very small energetic-offset (ΔELE − CT), the charge-transfer (CT) and local-exciton (LE) states strongly interact via electronic hybridization and thermal population effects, suppressing the non-radiative recombination. Here, we investigated the impact of these effects on charge generation and recombination. In the blends of PTO2:C8IC and PTO2:Y6 with very small, ultra-fast CT state formation was observed, and assigned to direct photoexcitation resulting from strong hybridization of the LE and CT states (i.e., LE-CT intermixed states). These states in turn accelerate the recombination of both CT and charge separated (CS) states. Moreover, they can be significantly weakened by an external-electric field, which enhanced the yield of CT and CS states but attenuated the emission of the device. This study highlights that excessive LE-CT hybridization due to very low , whilst enabling direct and ultrafast charge transfer and increasing the proportion of radiative versus non-radiative recombination rates, comes at the expense of accelerating recombination losses competing with exciton-to-charge conversion process, resulting in a loss of photocurrent generation.

Exceeding the energy density of lithium−carbon monofluoride (Li−CFx), today's leading Li primary battery, requires an increase in fluorine content (x) that determines the theoretical capacity available from C−F bond reduction. However, high F-content carbon materials face challenges such as poor electronic conductivity, low reduction potentials (<1.3 V versus Li/Li+), and/or low C−F bond utilization. This study investigates molecular structural design principles for a new class of high F-content fluoroalkyl-aromatic catholytes that address these challenges. A polarizable conjugated system—an aromatic ring with an alkene linker—functions as electron acceptor and redox initiator, enabling a cascade defluorination of an adjacent perfluoroalkyl chain (RF = −CnF2n+1). The synthesized molecules successfully overcome premature deactivation observed in previously studied catholytes and achieve close-to-full defluorination (up to 15/17 available F), yielding high gravimetric capacities of 748 mAh g−1fluoroalkyl-aromatic and energies of 1785 Wh kg−1fluoroalkyl-aromatic. The voltage compatibility between fluoroalkyl-aromatics and CFx enables design of hybrid cells containing C−F redox activity in both solid and liquid phases, with a projected enhancement of Li–CFx gravimetric energy by 35% based on weight of electrodes+electrolyte. With further improvement of cathode architecture, these “liquid CFx” analogues are strong candidates for exceeding the energy limitations of today's primary chemistries.

The solar-only response nature limits the luminescent solar concentrators (LSCs) to solar harvesting rather than responding to other stimuli, which restricts the role of LSCs to energy supply in self-powered internet of things (IoT) systems, and the application potential of LSCs in self-powered devices has been seriously overlooked. In this work, LSCs with photovoltaic and piezoelectric features are proposed for the first time, extending the application scenario of LSCs to self-powered sensors with pressure responsiveness. The luminescent layer of perovskite-polymer composite film is prepared via in situ blade coating with the piezoelectric polymer matrix of poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)). P(VDF-TrFE) possesses stronger DMF adsorption capacity and higher electroactive phase content than a conventional piezoelectric matrix of poly(vinylidene fluoride) (PVDF), which not only reduces the residual-solvent-induced defects in perovskite luminophores, but also brings a sensitive pressure response to LSCs. The dual-functional LSCs achieve a power conversion efficiency of 1.01% and a output piezoelectric voltage of 0.95 V can be obtained even at a low pressure of 0.16 kPa. A self-powered speed measurement system is demonstrated, and the actual speed measurement is carried out. Such dual-functional LSCs show great potential in self-powered electrical devices, which can be applied to low-energy-consumption IoT systems and other commercial smart home products.

Solid polymer electrolytes (SPEs) are expected to possess high ionic conductivity and conformal interfacial contact with all cell components for all-solid-state lithium-ion batteries. However, the commonly used in situ separator-assisted approach reduces the ionic conductivity because of the use of inert and non-ion-conducting separators. Here, a facile separator-free dual-curing strategy combining UV-curing outside the cell and subsequent thermal-curing inside the cell is reported, in which the second thermal polymerization process provides improved interfacial properties without sacrificing ionic conductivity. The resulting DC-SPEs possess high ionic conductivity (0.3 mS cm−1 at 25 °C), a wide electrochemical stability window (4.64 V vs Li/Li+), and improved interfacial properties. The in situ-formed DC-SPE can effectively suppress the growth of Li dendrites and achieve stable Li symmetric cell cycling performance at high current density (over 700 h at 0.2 mA cm−2 and 0.2 mAh cm−2). The all-solid-state lithium metal batteries (LMBs) with LiFePO4 demonstrate high coulombic efficiency (>99.93%) and ultrastable cycling stability (900 cycles) at 1C rate under 40 °C. The dual-curing strategy provides a brand new in situ processing method to avoid the use of expensive and inert separators, which can be widely applied to the development of all-solid-state LMBs.

Lithium Metal Anodes

Introducing additional elements into Ni-rich cathodes is an essential strategy for addressing the instability of the cathode material. Conventionally, this doping strategy considers only the incorporation of additional elements into the bulk structure of the cathode in terms of fortifying the crystal structure. However, high-valence elements such as Nb5+, Ta5+, and Mo6+ are likely to be insoluble in the crystal structure, resulting in accumulation along the interparticle boundaries. Herein, a new mechanism for doping high-valence elements into Ni-rich cathodes and their effects on the morphology and crystal structure are investigated by calcining LiNiO2 (LNO) and X-doped LNO cathodes (X = Al, Nb, Ta, and Mo) at various temperatures. Operando X-ray diffraction analysis reveals that the temperature at which the content of Li-X-O compounds declines is higher for the dopants with high oxidation states, reinforcing segregation at the grain boundary and widening the calcination temperature range. Thus, the highly aligned microstructure and high crystallinity of the LNO cathode are maintained over a wide calcination temperature range after doping with high-valence elements, enhancing the electrochemical performance. As next-generation dopants, high-valence elements can fortify not only the crystal structure, but also the microstructure, to maximize the electrochemical performance of Ni-rich cathodes.

Rechargeable Magnesium Batteries

Adv. Energy Mater. 2020, 10, 1903696 DOI: 10.1002/aenm.201903696 In the originally published manuscript, on Page 4, a number of errors related to binding energies were made. The corrected text is below, Figure S4a (Supporting Information) shows the peaks corresponding to S-2p3/2 and S-2p1/2 with binding energies at 164.13 and 165.29 eV, respectively.[17] The Pb2+-4f7/2 and Pb2+-4f5/2 peaks derived from the first scan is determined to be 138.63 and 143.51 eV, respectively (Figure 3a). In the supporting information file of the same manuscript, on Page 2, in the “Device fabrication” an error related to the protocol for ligand modification was made. The corrected text is below, For ligand modification, 0.5 mg pentaerythritol tetrakis(3-mercaptopropionate) (ML) is dissolved in 1 mL CB and spun on top of perovskite, These errors do not affect the conclusions of the report. The authors apologize for any inconvenience caused.

Ion and electron transport is of paramount importance for solid-state technology and its limitation presently prevents the access to liquid cells performance. Herein, this work tackles this issue by proposing an easily implementable cell design enabling to follow the cathode composite's electronic conductivity evolution, in situ and during cycling. For proof of concept, distinct active material (AM) based composites are studied, namely LiCoO2 (LCO), LiNiO2, LiNi0.9Co0.1O2 (NC 9010), NMC 811, NMC 622, NMC 111 (NMC family: LiNi1-yMnyCoyO2), and Li4Ti5O12 (LTO) mixed with Li6PS5Cl solid electrolyte (SE). This work shows the feasibility to track AM's phase transitions associated with changes in the material's electronic transport properties. Moreover, this work demonstrates the impact of the Ni content in the various layered oxides, on the interparticle loss of contact at high state-of-charge affecting electronic transport. Lastly, by tuning LTO particle size and morphology, this work shows the effect of primary and secondary particle size on the specific metal–insulator transition pertaining to this material. Altogether, this new testing cell opens-up a broad spectrum of experimental possibilities aiming to access in situ mode key metrics to benefit the optimization of solid-state batteries research.

Li-rich layered oxides based on the anionic redox chemistry provide the highest practical capacity among all transition metal (TM) oxide cathodes but still struggle with poor cycling stability. Here, a certain amount of oxygen vacancies (OVs) are introduced into the ≈10 nm-thick surface region of Li1.2Ni0.13Co0.13Mn0.54O2 through a long-time medium-temperature post-annealing. These surficial enriched OVs significantly suppress the generation of O-O dimers (O2n−, 0 < n < 4) and the associated side reactions, thus facilitating the construction of a uniform and compact cathode/electrolyte interphase (CEI) layer on the surface. The CEI layer then decreases the further side reactions and TM dissolution and protects the bulk structure upon cycling, eventually leading to enhanced cycling stability, demonstrated in both half cells and full cells. An in-depth understanding of OVs is expected to benefit the design of stable cathode materials based on anionic redox chemistry.

Microcavity resonance is an effective technique for making promising semitransparent organic photovoltaics (ST-OPVs) even more aesthetically attractive with high color saturation, by tailoring the visible transmittance spectrum to narrow the transmission peak. In this study, a distinctive microcavity resonance color filter (CF) structure of silver/ bismuth(III) fluoride /silver (Ag/BiF3/Ag) is integrated upon the rear transparent electrode, which simultaneously achieves high color purity and high power conversion efficiency (PCE) for colorful OPVs. By precisely regulating the thickness of the BiF3 layer, colorful OPVs with a wide color gamut and high color purity are achieved, including the colors of indigo, blue, bluish-green, green, orange, and red, as well as compound color devices with dual or multiple transmission peaks in the visible region. A recorded PCE of 16.27% is obtained for the indigo OPV, with the Commission Internationale de l´Eclairage 1931 coordinates of (0.164 and 0.087) and a maximum transmittance of 18.7% at the transmission peak wavelength of 393 nm. Furthermore, colorful OPVs as color reflectors are systematically investigated under different light incident surfaces. The improved stability of colorful OPVs is attributed to the excellent moisture resistance of BiF3. The colorful OPVs with desired transmitted/reflected colors, and wide color gamut show great potential for future energy harvesting solutions.

The fast development of wearable electronic systems requires a sustainable energy source that can harvest energy from the ambient environment and does not require frequent charging. Piezoelectric polymer films are a perfect candidate for fabricating piezoelectric nanogenerators (PENGs) to harvest mechanical energy from the environment due to their flexibility, good piezoelectricity, and environmental-independent stable performance because of their inherent polarization. However, most of their applications are limited to the pressing mode energy harvesting that is based on the 3-3-direction piezoelectric effect due to the molecular polarization and nonstretchability. In this work, by 3D printing an auxetic structure on a polymer film-based PENG, the bending deformation of the PENG can be transformed into the well-controlled in-plane stretching deformation, enabling the 3-1-direction piezoelectric effect. The synclastic effect of the auxetic structure is applied in flexible energy harvesting device for the first time, which makes the previously untapped bending deformation on a film a valuable device for energy harvesting and increases the bending output voltage of the PENG by 8.3 times. The auxetic structure-assisted PENG is also demonstrated as a sensor to sense the bending angle and monitor the motion by mounting on different joints of the human body and soft robotic finger.

Lithium-Ion Batteries

Potassium-Ion Batteries

Heat generated from various sources is inevitably wasted. Thermoelectric generators (TEGs) are suitable for recovering such waste heat because of their simple structure and operating principle. Herein, a zwitterionic (ZI) polymer-based fully self-healable ionic TEG is presented. By adjusting the position of the positive and negative moieties of the ZI side chain, the movement of free ions contained in the ionogel can be controlled effectively, thus improving the power factor of TEGs. ZI side chains inside the ionogel provide multiple ionic interaction sites and enable fast self-healing characteristics at room temperature. Furthermore, a self-healing electrode composed of liquid metal (LM), waterborne polyurethane (WPU), and polyvinyl alcohol (PVA) is developed for the fully healable TEGs. The overall areal output voltage is effectively improved by connecting 10 legs of p and n thermoelectric gels in series via a self-healing process. The selectively ion-boosted, fully self-healable TEGs developed in this study will open a new horizon for high-performance ionic TEGs.

The success of liquid/solid-state batteries is fundamentally determined by the electrode microstructures, which is particularly true for high-energy-density electrodes with either thick configuration or high-capacity active materials. Unfortunately, high-energy-density electrodes usually suffer from fast performance degradation due to various challenging issues in microstructures. Therefore, a better understanding of electrode microstructures and the strategies toward optimizing them are in urgent need by the research community and battery industries. In this review, the authors attempt to rethink and comprehensively understand the multiscale microstructures for particularly thick electrodes and to summarize the corresponding structuring strategies. Specifically, in analogy to proteins, the multiscale electrode microstructures are classified into the primary structures of rigid building blocks, the secondary structures of active material microenvironment, and the tertiary structures of electrode architectures. Meanwhile, the design principles and structuring strategies at different levels of microstructures are detailed with consideration given to efficiency, energy consumption, eco-friendliness, and scalability. Finally, a concept of a battery manufacturing genome based on structuring strategy profile (similar to amino acid profile) is proposed as the forthcoming opportunity for the future connection of machine learning with battery microstructure optimization, which may promote the development of next-generation on-demand batteries.

Nickel is a promising candidate as an alternative to ruthenium for an ammonia decomposition catalyst. However, the performance of Ni-based catalysts for ammonia decomposition is still not sufficient to achieve a good hydrogen production rate under low-temperature because the weak nitrogen affinity of Ni reduces the frequency of the ammonia decomposition reaction. Here, it is reported that Ni supported on barium titanium oxynitride (Ni/h-BaTiO3−xNy) with a hexagonal structure acts as a highly active and water-durable catalyst for ammonia decomposition. The operation temperature is reduced by over 140 °C when N3− ions are substituted onto the O2− sites of the BaTiO3 lattice, and the Ni/h-BaTiO3−xNy catalyst significantly outperforms conventional oxide-supported Ni catalysts for ammonia decomposition. Furthermore, the activity of Ni/h-BaTiO3−xNy remains unchanged after exposure to water. The 15NH3 decomposition reaction and Fourier transform-infrared spectroscopy (FT-IR) measurements reveal that lattice nitrogen vacancy sites on h-BaTiO3−xNy function as the active sites for ammonia decomposition. The ammonia decomposition activity of Ni/h-BaTiO3−xNy is also higher than that of the Ni/h-BaTiO3−xHy oxyhydride catalyst, making a contrast to the activity trend in ammonia synthesis.

Electrolytes

Solid-state lithium metal batteries have emerged as a promising technology for electric vehicles due to their high specific energy and safety potential. Obtaining intimate contact between Li and electrolyte during cell fabrication, however, remains challenging. Adequate fabrication pressure is required to promote close contact, but this pressure can cause Li deformation and penetration into the electrolyte, resulting in poor battery performance. Here, a strategy for addressing this problem is presented by incorporating 3 at% Mg into Li. Unlike pure Li which obeys the Voce hardening law and allows unconstrained deformation, Li─Mg alloy follows the Swift hardening law and strengthens with strain under compression stress. Because of the constrained deformation of Li─Mg, intimate contact with solid electrolytes is possible even at high fabrication pressure (50–65 MPa), resulting in high critical current densities. These findings underscore the importance of understanding Li metal deformation properties to improve solid-state battery performance.

Popularly-used fluorination can effectively weaken Li+-solvent interaction to facilitate the desolvation process at low temperature; however, high fluorination degree sacrifices salt dissociation and ionic conductivity. Herein, functional fluorinations are well tuned with different amounts of F atoms to balance Li+-solvent binding energy and ion movement, which reveals the fluorination effect on the solvation behavior and low-temperature performance. Noteworthily, the moderately-fluorinated ethyl difluoroacetate (EDFA) successfully favors a lower binding energy than less-fluorinated ethyl fluoroacetateand superior salt dissociation more than highly-fluorinated ethyl trifluoroacetate, realizing the trade-off between weak affinity and sufficient ionic conductivity. The well-formulated EDFA-based electrolyte exhibits a unique solvation sheath and generates inorganic-rich solid electrolyte interphase with low resistance for smooth Li+ diffusion, which enables graphite anodes with excellent fast-charging capability (196 mAh g−1 at 6 C) and impressive low-temperature performance with a reversible capacity of 279 mAh g−1 under −40 °C. Subsequently, the wide electrochemical potential window of EDFA-based electrolyte endows the 1.2 Ah LiNi0.8Co0.1Mn0.1O2 (NCM811)||graphite pouch cells with a high reversible capacity retention of 58.3% at −30 °C and discharge capacity of 790 mAh at −40 °C. Such solvent molecules with a moderately-fluorinated strategy promise advanced electrolyte design for lithium-ion batteries operating under harsh conditions.