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[Display omitted] The Li-rich layered oxide is considered as one of the most promising cathode materials for high energy density batteries, due to its ultrahigh capacity derived from oxygen redox. Although incorporating over-stoichiometric Li into layered structure can generate Li 2 MnO 3 -like domain and enhance the oxygen redox activity thermodynamically, the fast and complete activation of the Li 2 MnO 3 -like domain remains challenging. Herein, we performed a systematic study on structural characteristics of Li-rich cathode materials to decipher the factors accounting for activation of oxygen redox. We reveal that the activation of Li-rich cathode materials is susceptible to local Co coordination environments. The Co ions can intrude into Li 2 MnO 3 -like domain and modulate the electronic structure, thereby facilitating the activation of Li-rich layered cathode materials upon first charging, leading to higher reversible capacity. In contrast, Li 2 MnO 3 -like domain hardly contains any Ni ions which contribute little to the activation process. The optimum composition design of this class of materials is discussed and we demonstrate a small amount of Co/Mn exchange in Li 2 MnO 3 -like domain can significantly promote the oxygen redox activation. Our findings highlight the vital role of Co ions in the activation of oxygen redox Li-rich layered cathode materials and provide new insights into the pathway toward achieving high-capacity Li-rich layered cathode materials. [ABSTRACT FROM AUTHOR]

Despite their safe and cost‐effective merits, the cycling durability of aqueous zinc–organic batteries is hindered by cathode dissolution and low coulombic efficiency of Zn metal anodes. Herein, a Zn metal‐free all‐organic zinc‐ion battery (ZIB) is proposed by using quinoxalino[2,3‐i]diquinoxalino[2′,3′:6,7]quinoxalino[2,3‐a:2,3‐c] phenazine (QDPA) cathode coupled with a 1,4,5,8‐Naphthalenetetracarboxylic diimide (NPI) anode, rendering excellent electrochemical reversibility with high utilization. Based on the molecular architecture strategy, a QDPA cathode with an enlarged aromatic ring system is designed and synthesized, which not only effectively inhibits structural collapse during cycling but also enhances the working voltage without lowering the active group ratio. Moreover, theoretical calculations and experimental results confirm the rapid H+ storage mechanism in the CN active sites of QDPA, affording ultra‐fast electrochemical kinetics. Thus, it delivers a negligible capacity decay of 0.002% up to 13 000 cycles at 20 A g−1. Moreover, the QDPA//NPI all‐organic aqueous ZIB with a high energy density of 43.1 Wh kg−1 is demonstrated to be easily disassembled and recycled by the incineration treatment after battery failure, ensuring outstanding environmental sustainability. [ABSTRACT FROM AUTHOR]

Spinel‐type LiNi0.5Mn1.5O4 (LNMO) is one of the most promising 5 V‐class cathode materials for Li‐ion batteries that can achieve high energy density and low production costs. However, in liquid electrolyte cells, the high voltage causes continuous cell degradation through the oxidative decomposition of carbonate‐based liquid electrolytes. In contrast, some solid‐state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this work, a thin‐film battery consisting of an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte is tested and their interface before and after cycling is characterized. With Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency >99%. Neutron depth profiling indicates a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Cryogenic electron microscopy further reveals intimate contact between LNMO and LiPON without noticeable structure and chemical composition evolution after extended cycling, demonstrating the superior stability of LiPON against a high voltage cathode. Consequently, design guidelines are proposed for interface engineering that can accelerate the commercialization of a high voltage cell with solid or liquid electrolytes. [ABSTRACT FROM AUTHOR]

Lithium/fluorinated graphite (Li/CFx) primary batteries show great promise for applications in a wide range of energy storage systems due to their high energy density (>2100 Wh kg–1) and low self‐discharge rate (<0.5% per year at 25 °C). While the electrochemical performance of the CFx cathode is indeed promising, the discharge reaction mechanism is not thoroughly understood to date. In this article, a multiscale investigation of the CFx discharge mechanism is performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, cross‐sectional focused ion beam, high‐resolution transmission electron microscopy, and scanning transmission electron microscopy with electron energy loss spectroscopy are utilized to investigate this system. Results show no metallic lithium deposition or intercalation during the discharge reaction. Crystalline lithium fluoride particles uniformly distributed with <10 nm sizes into the CFx layers, and carbon with lower sp2 content similar to the hard‐carbon structure are the products during discharge. 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. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • TOBC nanofibers are used as "spacer" in rGO sheets and mechanical buffer layer in macrofibers. • The highly-winkled TOBC/rGO fibers has high electrical conductivity, which can reach 100.2 S cm−1 with 70% rGO concentration. • PPy@TOBC/rGO electrode delivers high capacitance of 391 F g−1 at 0.5 A g−1. • The FSC exhibits an energy density of 8.8 mWh cm−3 with high cycling and bending stability. Abstract The emerging fiber-based supercapacitors with high energy and power density are highly desirable for they provide strong support for the development of portable and wearable devices. Here, a flexible, binder-free high-performance fiber-based supercapacitors is structured based on hierarchical polypyrrole@TEMPO-oxidized bacterial cellulose/reduced graphene oxide macrofibers by wet spinning and in situ polymerization polypyrrole. For the synergistic effects of three components, the excellent specific capacitance of the electrode with 391 F g−1 (373 F cm−3) at the current density of 0.5 A g−1 (0.48 A cm−3) and the fiber-based supercapacitor made of the electrodes with 259 F g−1 (258 F cm−3) at the current density of 0.2 A g−1 (0.199 A cm−3) are achieved. Moreover, the fiber-based supercapacitor exhibits a high energy density of 8.8 mWh cm−3 at the power density of 49.2 mW cm−3 and a highpower density of 429.3 mW cm−3 at the energy density of 4.1 mWh cm−3, which is better than most previously reported graphene fiber-based supercapacitors. In these devices, we realize a desirable combination of excellent electrochemical performance and good flexibility, which will be significant for satisfying the requirement of the energy and power in various portable, miniaturized, and wearable electronic devices. [ABSTRACT FROM AUTHOR]

Although layered lithium oxides have become the cathode of choice for state-of-the-art Li-ion batteries, substantial gaps remain between the practical and theoretical energy densities. With the aim of supporting efforts to close this gap, this work reviews the fundamental operating mechanisms and challenges of Li intercalation in layered oxides, contrasts how these challenges play out differently for different materials (with emphasis on Ni-Co-Al (NCA) and Ni-Mn-Co (NMC) alloys), and summarizes the extensive corpus of modifications and extensions to the layered lithium oxides. Particular emphasis is given to the fundamental mechanisms behind the operation and degradation of layered intercalation electrode materials as well as novel modifications and extensions, including Na-ion and cation-disordered materials. [ABSTRACT FROM AUTHOR]

Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3 Ni(3/8-3x/8) Co(1/4-x/4) Mn(3/8+7x/24) O2) x = 0.6, HLR) and low Li-rich Li(Lix/3 Ni(1/3-x/3) Co(1/3-x/3) Mn(1/3+x/3) O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presence of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. Once the high voltage plateau is reached, the lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate. [ABSTRACT FROM AUTHOR]

The rapidly growing technological demand for lithium-ion batteries has prompted the development of novel cathode materials with high energy density, low cost, and improved safety. High voltage spinel, LiNi 0.5 Mn 1.5 O 4 (LNMO), is one of the most promising candidates yet to be commercialized. The two primary obstacles for this material are the inferior electronic conductivity and fast capacity degradation in full cells due to the high operating voltage. By systematically addressing these limitations, we successfully develop a thick LNMO electrode with areal capacity loadings up to 3 mAh·cm−2. The optimized thick electrode is paired with a commercial graphite anode at both the coin cell and pouch cell level, achieving a full cell capacity retention as high as 72% and 78%, respectively, after 300 cycles. We attribute this superior cycling stability to careful optimizations of cell components and testing conditions, with a specific focus improving electronic conductivity and high voltage compatibility. These results suggest precise control of materials quality, electrode architecture and electrolyte optimization can soon support the development of a cobalt-free battery system based on a thick LNMO cathode (>4 mAh·cm2), which will eventually meet the needs of next-generation Li-ion batteries with reduced cost, improved safety, and assured sustainability. • Inactive components in LNMO cathode have significant impact on cycling stability. • 3 mAh/cm2 LNMO electrode paired with graphite shows superior cycle stability. • Degradation is triggered by graphite failure through cross-talk with LNMO cathode. [ABSTRACT FROM AUTHOR]