A Composite of Carbon‐Wrapped Mo2C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O2 Batteries

Cathode design is indispensable for building Li‐O₂ batteries with long cycle life. A composite of carbon‐wrapped Mo₂C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo₂C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo₂C nanoparticles. The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O₂ batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g^?1 and a low average charge voltage of ≈4.0 V at 200 mA g^?1. With a cutoff capacity of 1000 mAh g^?1, the Li‐O₂ batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo₂C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O₂ batteries.     

Elastic Carbon Nanotube Aerogel Meets Tellurium Nanowires: A Binder‐ and Collector‐Free Electrode for Li‐Te Batteries

Rechargeable Li batteries based on group VIA element cathodes, such as tellurium, are emerging due to their capability to provide equivalent theoretical volumetric capacity density to O and S, as well as an improved activity to react with Li. Herein, bifunctional and elastic carbon nanotube (CNT) aerogel is fabricated to combine with Te nanowires, yielding two types of binder/collector‐free Te cathodes to assemble Li‐Te batteries. The CNTs with high electronic conductivity and hollow porous structure enable stable electric contact and fast transportation of Li⁺, while trapping Te and Li₂Te in its network, triggering fast and stable Li‐Te electrochemistry. Both cathodes are also provided with fine compressibility, helping to buffer their volume changes during lithiation/delithiation and improving electrode integrity. Both cathodes deliver high specific capacity, fine cycling stability, and favorable high‐rate capability, proving their competence in building high‐energy rechargeable Li‐ion batteries.     

A Moisture‐ and Oxygen‐Impermeable Separator for Aprotic Li‐O2 Batteries

Despite the unparalleled theoretical gravimetric energy, Li‐O₂ batteries are still under a research stage because of their insufficient cycle lives. While the reversibility in air‐cathodes has been lately improved significantly by the deepened understanding on the electrode–electrolyte reaction and the integration of diverse catalysts, the stability of the Li metal interface has received relatively much less attention. The destabilization of the Li metal interface by crossover of water and oxygen from the air‐cathode side can indeed cause as fatal degradation for the cycle life as the irreversibility of the air‐cathodes. Here, it is reported that cheap poreless polyurethane separator can effectively suppress this crossover while allowing Li ions to diffuse through selectively. The polyurethane separator also protects Li metal anodes from redox mediators used for enhancing the reversibility of the air‐cathode reaction. Based on the Li metal protection, a persistent capacity of 600 mAh g^?1 is preserved for more than 200 cycles. The current approach can be readily applicable to many other rechargeable batteries that suffer from similar interfacial degradation by side products from the other electrode.     

Hierarchical Carbon–Nitrogen Architectures with Both Mesopores and Macrochannels as Excellent Cathodes for Rechargeable Li–O2 Batteries

Lithium–oxygen batteries are attracting more and more interest; however, their poor rechargeability and low efficiency remain critical barriers to practical applications. Herein, hierarchical carbon–nitrogen architectures with both macrochannels and mesopores are prepared through an economical and environmentally benign sol–gel route, which show high electrocatalytic activity and stable cyclability over 160 cycles as cathodes for Li–O₂ batteries. Such good performance owes to the coexistence of macrochannels and mesopores in C–N hierarchical architectures, which greatly facilitate the Li⁺ diffusion and electrolyte immersion, as well as provide an effective space for O₂ diffusion and O₂/Li₂O₂ conversion. Additionally, the mechanism of oxygen reduction reactions is discussed with the N‐rich carbon materials through first‐principles computations. The lithiated pyridinic N provides excellent O₂ adsorption and activation sites, and thus catalyzes the electrode processes. Therefore, hierarchical carbon–nitrogen architectures with both macrochannels and mesopores are promising cathodes for Li–O₂ batteries.     

Enhanced Cycling Stability of Rechargeable Li–O2 Batteries Using High‐Concentration Electrolytes

The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li–O₂ batteries. In this work, the effect of lithium salt concentration in 1,2‐dimethoxyethane (DME)‐based electrolytes on the cycling stability of Li–O₂ batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0–4.5 V vs Li/Li⁺) and the capacity‐limited (at 1000 mAh g^?1) conditions. These cells also exhibit much less reaction residue on the charged air‐electrode surface and much less corrosion of the Li‐metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li⁺–(DME) _n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C–H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li‐metal anodes exhibit much better reversibility, resulting in improved cyclability of Li–O₂ batteries.     

Homogeneous CoO on Graphene for Binder‐Free and Ultralong‐Life Lithium Ion Batteries

Ultralong cycle life, high energy, and power density rechargeable lithium‐ion batteries are crucial to the ever‐increasing large‐scale electric energy storage for renewable energy and sustainable road transport. However, the commercial graphite anode cannot perform this challenging task due to its low theoretical capacity and poor rate‐capability performance. Metal oxides hold much higher capacity but still are plagued by low rate capability and serious capacity degradation. Here, a novel strategy is developed to prepare binder‐free and mechanically robust CoO/graphene electrodes, wherein homogenous and full coating of β‐Co(OH)₂ nanosheets on graphene, through a novel electrostatic induced spread growth method, plays a key role. The combined advantages of large 2D surface and moderate inflexibility of the as‐obtained β‐Co(OH)₂/graphene hybrid enables its easy coating on Cu foil by a simple layer‐by‐layer stacking process. Devices made with these electrodes exhibit high rate capability over a temperature range from 0 to 55 °C and, most importantly, maintain excellent cycle stability up to 5000 cycles even at a high current density.     

A Li–Al–O Solid‐State Electrolyte with High Ionic Conductivity and Good Capability to Protect Li Anode

Using a solid‐state electrolyte (SSE) to stabilize the Li metal anode is widely considered a promising route to develop next‐generation high energy density lithium batteries. Here, a new polycrystalline aluminate‐based SSE (named Li–Al–O SSE) with good capability is introduced to protect Li metal. The SSE is formed on the Li metal surface via a chemical reaction between LiOH and triethylaluminum (TEAL) with the existence of LiTFSI‐based electrolyte. It is a continuous film that consists of polycrystalline LiAlO₂, Li₃AlO₃, Al₂O₃, Li₂CO₃, LiF, and some organic compounds. Such Li–Al–O SSE possesses a room‐temperature ionic conductivity as high as 1.42 × 10^?4 S cm^?1. Meanwhile, it effectively protects the Li anode from the corrosion of H₂O, O₂, and organic solvent, and suppresses the growth of Li dendrite. With the protection of the Li–Al–O SSE, the cycle life of Li|Li symmetric cell and Li|O₂ cell is substantially elongated, indicating that the SSE exhibits an excellent protective effect under both inert and oxidizing circumstances.     

Graphene Oxide Gel‐Derived,Free‐Standing,Hierarchically Porous Carbon for High‐Capacity and High‐Rate Rechargeable Li‐O2 Batteries

Lithium‐oxygen (Li‐O₂) batteries are one of the most promising candidates for high‐energy‐density storage systems. However, the low utilization of porous carbon and the inefficient transport of reactants in the cathode limit terribly the practical capacity and, in particular, the rate capability of state‐of‐the‐art Li‐O₂ batteries. Here, free‐standing, hierarchically porous carbon (FHPC) derived from graphene oxide (GO) gel in nickel foam without any additional binder is synthesized by a facile and effective in situ sol‐gel method, wherein the GO not only acts as a special carbon source, but also provides the framework of a 3D gel; more importantly, the proper acidity via its intrinsic COOH groups guarantees the formation of the whole structure. Interestingly, when employed as a cathode for Li‐O₂ batteries, the capacity reaches 11 060 mA h g^?1 at a current density of 0.2 mA cm^?2 (280 mA g^?1); and, unexpectedly, a high capacity of 2020 mA h g^?1 can be obtained even the current density increases ten times, up to 2 mA cm^?2 (2.8 A g^?1), which is the best rate performance for Li‐O₂ batteries reported to date. This excellent performance is attributed to the synergistic effect of the loose packing of the carbon, the hierarchical porous structure, and the high electronic conductivity of the Ni foam.     

Au‐Decorated Cracked Carbon Tube Arrays as Binder‐Free Catalytic Cathode Enabling Guided Li2O2 Inner Growth for High‐Performance Li‐O2 Batteries

Owing to their extremely high energy density, Li‐O₂ batteries have attained increasing attention in recent studies. However, deposition of the discharge product, insulating Li₂O₂, is known to seriously limit the electrochemical performance of Li‐O₂ batteries. While extensive studies have focused on relieving electrode deactivation by controlling Li₂O₂ growth, no permanent or effective mechanism is delivered. Here, a unique design comprising a catalytic cathode constructed by cracked carbon submicron tube (CST) arrays decorated with Au nanoparticles on inner walls is proposed. The introduction of Au nanoparticles not only improves electrode conductivity but also provides catalytic sites, guiding conformal growth of thin‐layered Li₂O₂ inside the cracked CST. Density functional theory calculations support that Au decoration on CST favors the conformal growth of Li₂O₂ on inner tubular walls. This growth behavior of Li₂O₂ renders easy decomposition of Li₂O₂, prevents carbon tube electrode from full, rapid deactivation, and preserves the free space for reactants transport. Li‐O₂ cells with Au@CST exhibit good rate capability (1208 mAh g^–1 at a high current density of 1000 mA g^–1) and long cycle life (112 cycles at a current density of 400 mA g^–1 with a limited capacity of 500 mAh g^–1).     

Li‐CO2 Batteries Efficiently Working at Ultra‐Low Temperatures

Lithium‐carbon dioxide (Li‐CO₂) batteries are considered promising energy‐storage systems in extreme environments with ultra‐high CO₂ concentrations, such as Mars with 96% CO₂ in the atmosphere, due to their potentially high specific energy densities. However, besides having ultra‐high CO₂ concentration, another vital but seemingly overlooked fact lies in that Mars is an extremely cold planet with an average temperature of approximately ?60 °C. The existing Li‐CO₂ batteries could work at room temperature or higher, but they will face severe performance degradation or even a complete failure once the ambient temperature falls below 0 °C. Herein, ultra‐low‐temperature Li‐CO₂ batteries are demonstrated by designing 1,3‐dioxolane‐based electrolyte and iridium‐based cathode, which show both a high deep discharge capacity of 8976 mAh g^?1 and a long lifespan of 150 cycles (1500 h) with a fixed 500 mAh g^?1 capacity per cycle at ?60 °C. The easy‐to‐decompose discharge products in small size on the cathode and the suppressed parasitic reactions both in the electrolyte and on the Li anode at low temperatures together contribute to the above high electrochemical performances.     

A High‐Performance Li–B–H Electrolyte for All‐Solid‐State Li Batteries

Highly Li‐ion conductive Li₄(BH₄)₃I@SBA‐15 is synthesized by confining the LiI doped LiBH₄ into mesoporous silica SBA‐15. Uniform nanoconfinement of P6₃ mc phase Li₄(BH₄)₃I in SBA‐15 mesopores leads to a significantly enhanced conductivity of 2.5 × 10^?4 S cm^?1 with a Li‐ion transference number of 0.97 at 35 °C. The super Li‐ion mobility in the interface layer with a thickness of 1.2 nm between Li₄(BH₄)₃I and SBA‐15 is believed to be responsible for the fast Li‐ion conduction in Li₄(BH₄)₃I@SBA‐15. Additionally, Li₄(BH₄)₃I@SBA‐15 also exhibits a wide apparent electrochemical stability window (0 to 5 V vs Li/Li⁺) and a superior Li dendrite suppression capability (critical current density 2.6 mA cm^?2 at 55 °C) due to the formation of stable interphases. More importantly, Li₄(BH₄)₃I@SBA‐15‐based Li batteries using either high‐capacity sulfur cathode or high‐voltage oxide cathode show excellent electrochemical performances, making Li₄(BH₄)₃I@SBA‐15 a very attractive electrolyte for next‐generation all‐solid‐state Li batteries.     

Copper‐Stabilized Sulfur‐Microporous Carbon Cathodes for Li–S Batteries

A copper‐stabilized sulfur‐microporous carbon ( MC‐Cu‐S) composite is synthesized by uniformly dispersing 10% highly electronically conductive Cu nanoparticles into microporous carbon (MC), followed by wet‐impregnating S. In the MC‐Cu‐S composite, the MC host that physically confines S/polysulfides provides free space to accommodate volumetric expansion of S during lithiation, while the Cu nanoparticles that are anchored in the MC further chemically interact with S/polysulfides through bonding between Cu and S/polysulfides. The Cu loading allows the S content to increase from 30 to 50% in the carbon‐S cathode material without scarifying the electrochemical performance in a low‐cost carbonate electrolyte. At a current density of 100 mA g^‐1, the MC‐Cu‐S cathode shows that Coulumbic efficiency is close to 100% and capacity maintains more than 600 mAh g^‐1 with progressive cycling up to more than 500 cycles. In addition, the Cu nano‐inclusins also enhance the electronic conductivity of the MC‐Cu‐S composite, remarkably increasing the rate capabilities. Even the current density increases 10.0 A g^‐1, the MC‐Cu‐S cathode can still deliver a capacity of 200 mAh g^‐1. This strategy of stabilization of S with small amount of metal nanoparticles anchored in MC provides an effective approach to improve the cycling stability, Coulumbic efficiency, and S loading for Li–S batteries.     

Self‐Standing Porous LiCoO2 Nanosheet Arrays as 3D Cathodes for Flexible Li‐Ion Batteries

Self‐standing electrodes are the key to realize flexible Li‐ion batteries. However, fabrication of self‐standing cathodes is still a major challenge. In this work, porous LiCoO₂ nanosheet arrays are grown on Au‐coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co₃O₄ nanosheet arrays as the template followed by quick annealing in air. The binder‐free and self‐standing LiCoO₂ nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO₂ nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g^?1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li₄Ti₅O₁₂ nanosheet arrays as anode, an all‐nanosheet array based LiCoO₂//Li₄Ti₅O₁₂ flexible Li‐ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO₂//Li₄Ti₅O₁₂ battery can deliver large specific reversible capacities of 130.7 mA h g^?1 at 0.1 C rate and 85.3 mA h g^?1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li‐ion batteries.     

Anomalous Enhancement of Li‐O2 Battery Performance with Li2O2 Films Assisted by NiFeOx Nanofiber Catalysts: Insights into Morphology Control

It is generally understood that particle‐shaped Li₂O₂ is preferred in Li‐O₂ batteries (LOBs) because the dominance of Li₂O₂ films may lead to poor electrochemical performance. The influence of Li₂O₂ morphology and its nucleation mechanism are probed by experiments along with the first‐principle calculations. It is revealed that the LOBs with Li₂O₂ films deliver unexpectedly improved capacities, longer cycles, and significantly reduced overpotentials assisted by NiFeO_x nanofiber catalysts. The energetically favored Li 2a vacancies under LiO₂‐rich conditions, small crystallites, and large contact areas with the electrode/electrolyte explain the anomalous performance enhancement. Li₂O₂ films are formed by a heterogeneous nucleation mechanism and the voltage applied, electrolyte, electrode surface, and use of catalysts are identified as the parameters controlling the mechanisms. The mapped correlations among these parameters shed light on the control of Li₂O₂ morphology for developing high‐performance LOBs.     

A Targeted Functional Design for Highly Efficient and Stable Cathodes for Rechargeable Li‐Ion Batteries

Despite the great success of Li‐ion batteries (LIBs) up to now, higher demand has been raised with the emergence of the new generation electrics, such as portable devices and electrical vehicles. Even with the improvement on anodes, the cathodes with high capacity and long‐lastingness still remain a challenge. New 3D NiCo₂O₄@V₂O₅ core–shell arrays (CSAs) on carbon cloth as cathodes in LIBs have been reported in this work. The nanodesigned materials realize the theoretical specific capacity of V₂O₅ with high power rate based on the total mass of the framework and amount of active materials. The electrodes achieve superb cycling stability, among the most stable cathodes for LIBs ever reported. From both in situ transmission electron microscopy and quantum level calculations, the 3D NiCo₂O₄ nanosheet frameworks provide high electron conductivity and the skeleton of the robust CSAs without participating in the lithiation/delithiation; the thickness of the layered V₂O₅ plays a key role for Li diffusivity and the capacity contribution of electrodes. The structures herein point to new design concepts for high‐performance nanoarchitectures for LIB cathodes.     

3D Porous N‐Doped Graphene Frameworks Made of Interconnected Nanocages for Ultrahigh‐Rate and Long‐Life Li–O2 Batteries

The inferior rate capability and poor cycle stability of the present Li–O₂ batteries are still critical obstacles for practice applications. Configuring novel and integrated air electrode materials with unique structure and tunable chemical compositions is one of the efficient strategies to solve these bottleneck problems. Herein, a novel strategy for synthesis of 3D porous N‐doped graphene aerogels (NPGAs) with frameworks constructed by interconnected nanocages with the aid of polystyrene sphere@polydopamine is reported. The interconnected nanocages as the basic building unit of graphene sheets are assembled inside the skeletons of 3D graphene aerogels, leading to the 3D NPGA with well‐developed interconnected channels and the full exposure of electrochemically active sites. Benefiting from such an unique structure, the as‐made NPGA delivers a high specific capacity, an excellent rate capacity of 5978 mA h g^?1 at 3.2 A g^?1, and long cycle stability, especially at a large current density (54 cycles at 1 A g^?1), indicative of boosted rate capability and cycle life as air electrodes for Li–O₂ batteries. More importantly, based on the total mass of C+Li₂O₂, a gravimetric energy density of 2400 W h kg^?1 for the NPGA–O₂//Li cell is delivered at a power density of 1300 W kg^?1.     

Low‐Overpotential Li–O2 Batteries Based on TFSI Intercalated Co–Ti Layered Double Oxides

Lithium–oxygen batteries with an exceptionally high theoretical energy density have triggered worldwide interest in energy storage system. The research focus of lithium–oxygen batteries lies in the development of catalytic materials with excellent cycling stability and high bifunctional catalytic activity in oxygen reduction and oxygen evolution reactions. Here, a hierarchically porous flower‐like cobalt–titanium layered double oxide on nickel foam with intercalated anions of bistrifluoromethane sulfonamide (TFSI) is designed and prepared. When used as a binder‐free cathode for lithium–oxygen batteries, this material exhibits low polarization (initial polarization of 0.45 V) and superior cycling stability (80 cycles at a current density of 100 mA g^?1 at full discharge/charge). The high electrochemical performance of the cathode material is attributed to the good dispersion of binary elements in its host layer and good compatibility with lithium bistrifluoromethane sulfonamide electrolyte induced by intercalated guest anions of TFSI within its interlayer. This work provides a novel strategy for the fabrication of binder‐free cathodes based on layered double oxides for high‐performance lithium–oxygen batteries.