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Solid-state lithium metal batteries offer superior energy density, longer lifespan, and enhanced safety compared to traditional liquid-electrolyte batteries. Their development has the potential to revolutionize battery technology, including the creation of electric vehicles with extended ranges and smaller more efficient portable devices. The employment of metallic lithium as the negative electrode allows the use of Li-free positive electrode materials, expanding the range of cathode choices and increasing the diversity of solid-state battery design options. In this review, we present recent developments in the configuration of solid-state lithium batteries with conversion-type cathodes, which cannot be paired with conventional graphite or advanced silicon anodes due to the lack of active lithium. Recent advancements in electrode and cell configuration have resulted in significant improvements in solid-state batteries with chalcogen, chalcogenide, and halide cathodes, including improved energy density, better rate capability, longer cycle life, and other notable benefits. To fully leverage the benefits of lithium metal anodes in solid-state batteries, high-capacity conversion-type cathodes are necessary. While challenges remain in optimizing the interface between solid-state electrolytes and conversion-type cathodes, this area of research presents significant opportunities for the development of improved battery systems and will require continued efforts to overcome these challenges.

High‐voltage nickel‐rich layered cathodes possess the requisite, such as excellent discharge capacity and high energy density, to realize lithium batteries with higher energy density. However, such materials suffer from structural and interfacial instability at high voltages (>4.3 V). To reinforce the stability of these cathode materials at elevated voltages, lithium borate salts are investigated as electrolyte additives to generate a superior cathode‐electrolyte interphase. Specifically, the use of lithium bis(oxalato)borate (LiBOB) leads to an enhanced cycling stability with a capacity retention of 81.7%. Importantly, almost no voltage hysteresis is detected after 200 cycles at 1C. This outstanding electrochemical performance is attributed to an enhanced structural and interfacial stability, which is attained by suppressing the generation of micro‐cracks and the superficial structural degradation upon cycling. The improved stability stems from the formation of a fortified borate‐containing interphase which protects the highly reactive cathode from parasitic reactions with the electrolyte. Finally, the decomposition process of LiBOB and the possible adsorption routes to the cathode surface are deduced and elucidated. A boron‐containing electrolyte additive is proposed and investigated for high voltage nickel‐rich cathode (≥4.6 V), enabling an enhanced cycling stability and significantly suppressed voltage hysteresis due to the formation of a superior robust borate‐containing interphase layer, which highlights the possibility to break through the capacity bottleneck of nickel‐rich cathodes and achieve high‐energy‐density lithium‐metal battery.

Emerging energy storage systems have received significant attention along with the development of renewable energy, thereby creating a green energy platform for humans. Lithium-ion batteries (LIBs) are commonly used, such as in smartphones, tablets, earphones, and electric vehicles. However, lithium has certain limitations including safety, cost-effectiveness, and environmental issues. Sodium is believed to be an ideal replacement for lithium owing to its infinite abundance, safety, low cost, environmental friendliness, and energy storage behavior similar to that of lithium. Inhered in the achievement in the development of LIBs, sodium-ion batteries (SIBs) have rapidly evolved to be commercialized. Among the cathode, anode, and electrolyte, the cathode remains a significant challenge for achieving a stable, high-rate, and high-capacity device. In this review, recent advances in the development and optimization of cathode materials, including inorganic, organometallic, and organic materials, are discussed for SIBs. In addition, the challenges and strategies for enhancing the stability and performance of SIBs are highlighted.

HighlightsThe flower-like δ-MnO2 nanostructures with controlled oxygen vacancies as an extraordinary ZIBs cathode are innovatively developed.The cathode can present large capacity and high-rate zinc-ion storage.DFT analysis substantially unveils the effects of various vacancy concentrations on their electrochemical performances.In recent years, manganese-based oxides as an advanced class of cathode materials for zinc-ion batteries (ZIBs) have attracted a great deal of attentions from numerous researchers. However, their slow reaction kinetics, limited active sites and poor electrical conductivity inevitably give rise to the severe performance degradation. To solve these problems, herein, we introduce abundant oxygen vacancies into the flower-like δ-MnO2 nanostructure and effectively modulate the vacancy defects to reach the optimal level (δ-MnO2−x−2.0). The smart design intrinsically tunes the electronic structure, guarantees ion chemisorption–desorption equilibrium and increases the electroactive sites, which not only effectively accelerates charge transfer rate during reaction processes, but also endows more redox reactions, as verified by first-principle calculations. These merits can help the fabricated δ-MnO2−x−2.0 cathode to present a large specific capacity of 551.8 mAh g−1 at 0.5 A g−1, high-rate capability of 262.2 mAh g−1 at 10 A g−1 and an excellent cycle lifespan (83% of capacity retention after 1500 cycles), which is far superior to those of the other metal compound cathodes. In addition, the charge/discharge mechanism of the δ-MnO2−x−2.0 cathode has also been elaborated through ex situ techniques. This work opens up a new pathway for constructing the next-generation high-performance ZIBs cathode materials.

Anion-hosting cathodes capable of reversibly storing large-size anions play a leading role in dual-ion batteries (DIBs). The purpose of the present review is to summarize the most promising anion-hosting cathodes for current and late-stage DIBs. This review first summarizes the developments in conventional graphite cathodes, especially the latest advances in the graphite-related research. Next, organic cathodes for the anion storage are discussed, including aromatic amine polymers, heterocyclic polymers, bipolar compounds, and all-carbon-unsaturated compounds. Then, the review focuses on the conversion-type cathodes with high theoretical specific capacities. Finally, the future research directions of the cathodes of DIBs are proposed.

HighlightsA critical assessment of cathode–electrolyte interphase (CEI) for high-voltage cathode electrodes in Li-ion cells.Fundamental understanding of why interfacial interphase is important to electrochemical performance and further elaboration on how to design robust CEI interphase.Emerging theoretical simulations and advanced in situ characterizations helps to unveil the mystery of CEI are summarized.The thermal stability window of current commercial carbonate-based electrolytes is no longer sufficient to meet the ever-increasing cathode working voltage requirements of high energy density lithium-ion batteries. It is crucial to construct a robust cathode–electrolyte interphase (CEI) for high-voltage cathode electrodes to separate the electrolytes from the active cathode materials and thereby suppress the side reactions. Herein, this review presents a brief historic evolution of the mechanism of CEI formation and compositions, the state-of-art characterizations and modeling associated with CEI, and how to construct robust CEI from a practical electrolyte design perspective. The focus on electrolyte design is categorized into three parts: CEI-forming additives, anti-oxidation solvents, and lithium salts. Moreover, practical considerations for electrolyte design applications are proposed. This review will shed light on the future electrolyte design which enables aggressive high-voltage cathodes.

Sodium-ion batteries are being considered as a promising system for stationary energy storage and conversion, owing to the natural abundance of sodium. It is important to develop new cathode and anode materials with high capacities for sodium-ion batteries. Herein, we report the synthesis of beta -MnO sub(2) nanorods with exposed tunnel structures by a hydrothermal method. The as-prepared beta -MnO sub(2) nanorods have exposed {111} crystal planes with a high density of (1 1) tunnels, which leads to facile sodium ion (Na-ion) insertion and extraction. When applied as cathode materials in sodium-ion batteries, beta -MnO sub(2) nanorods exhibited good electrochemical performance with a high initial Na-ion storage capacity of 350 mAh g super(-1). beta -MnO sub(2) nanorods also demonstrated a satisfactory high-rate capability as cathode materials for sodium-ion batteries.

Although the theoretical specific capacity of LiCoO2 is as high as 274 mAh g−1, the superior electrochemical performances of LiCoO2 can be barely achieved due to the issues of severe structure destruction and LiCoO2/electrolyte interface side reactions when the upper cutoff voltage exceeds 4.5 V. Here, a bifunctional self‐stabilized strategy involving Al+Ti bulk codoping and gradient surface Mg doping is first proposed to synchronously enhance the high‐voltage (4.6 V) performances of LiCoO2. The comodified LiCoO2 (CMLCO) shows an initial discharge capacity of 224.9 mAh g−1 and 78% capacity retention after 200 cycles between 3.0 and 4.6 V. Excitingly, the CMLCO also exhibits a specific capacity of up to 142 mAh g−1 even at 10 C. Moreover, the long‐term cyclability of CMLCO/mesocarbon microbeads full cells is also enhanced significantly even at high temperature of 60 °C. The synergistic effects of this bifunctional self‐stabilized strategy on structural reversibility and interfacial stability are demonstrated by investigating the phase transitions and interface characteristics of cycled LiCoO2. This work will be a milestone breakthrough in the development of high‐voltage LiCoO2. It will also present an instructive contribution for resolving the big structural and interfacial challenges in other high‐energy‐density rechargeable batteries. A bifunctional self‐stabilized strategy involving Al+Ti bulk codoping and gradient surface Mg doping is first proposed to synchronously enhance the high‐voltage (4.6 V) performances of LiCoO2. The comodified LiCoO2 shows excellent long‐term cyclability and high‐rate capability in both half and full cells even at high temperature of 60 °C.

Organic anodes have emerged as a promising energy storage medium in proton ion batteries (PrIBs) due to their ability to reversibly accommodate non‐metallic proton ions. Nevertheless, the currently available organic electrodes often encounter dissolution issues, leading to a decrease in long‐cycle stability. In addition, the inherent potential of the organic anode is generally relatively high, resulting in low cell voltage of assembled PrIBs (<1.0 V). To address these challenges, a novel long‐period stable, low redox potential biphenylzine derivative, [2,2′‐biphenazine]‐7,7′‐tetraol (BPZT) is explored, from the perspective of molecular symmetry and solubility, in conjunction with the effect of the molecular frontier orbital energy levels on its redox potential. Specifically, BPZT exhibited a low potential of 0.29 V (vs SHE) and is virtually insoluble in 2 m H2SO4 electrolyte during cycling. When paired with MnO2@GF or PbO2 cathodes, the resulting PrIBs achieve cell voltages of 1.07 V or 1.44 V, respectively, and maintain a high capacity retention of 90% over 20000 cycles. Additionally, these full batteries can operate stably at a high mass loading of 10 mgBPZT cm−2, highlighting their potential toward long‐term energy storage applications. Two phenazine derivatives are designed to reversibly accommodate protons. Experimental results show that structural symmetric [2,2′‐biphenazine]‐7,7′‐tetraol (BPZT) outperforms 2,3‐dihydrohyphenazine. BPZT exhibits a low potential of 0.29 V (vs SHE) with negligible dissolution during cycling. When paired with MnO2@GF or PbO2 cathodes, full batteries achieve high voltages of 1.07 V or 1.44 V, and maintain a high capacity retention over 20 000 cycles.

Owing to the worldwide abundance and low-cost of Na, room-temperature Na-ion batteries are emerging as attractive energy storage systems for large- scale grids. Increasing the Na content in cathode materials is one of the effective ways to achieve high energy density. Prussian blue and its analogues （PBAs） are promising Na-rich cathode materials since they can theoretically store two Na＋ ions per formula unit. However, increasing the Na content in PBAs cathode materials remains a major challenge. Here we show that sodium iron hexacyanoferrate with high Na content can be obtained by simply controlling the reducing agent and reaction atmosphere during synthesis. The Na content can reach as high as 1.63 per formula, which is the highest value for sodium iron hexacyanoferrate. This Na-rich sodium iron hexacyanoferrate demonstrates a high specific capacity of 150 mAh·g^-1 and remarkable cycling performance with 90% capacity retention after 200 cycles. Furthermore, the Na intercalation/ de-intercalation mechanism has been systematically studied by in situ Raman spectroscopy, X-ray diffraction and X-ray absorption spectroscopy analysis for the first time. The Na-rich sodium iron hexacyanoferrate can function as a plenteous Na reservoir and has great potential as a cathode material for practical Na-ion batteries.