Construction of Bimetallic Selenides Encapsulated in Nitrogen/Sulfur Co‐Doped Hollow Carbon Nanospheres for High‐Performance Sodium/Potassium‐Ion Half/Full Batteries

Metallic selenides have been widely investigated as promising electrode materials for metal‐ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger‐sized Na⁺/K⁺ greatly hamper their application. Herein, a bimetallic selenide (MoSe₂/CoSe₂) encapsulated in nitrogen, sulfur‐codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K‐ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g^?1 at 10 A g^?1 in NIBs and 310 mAh g^?1 at 5 A g^?1 in KIBs. A combination of ex situ X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na⁺/K⁺ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K⁺ diffusion kinetics than that of Na⁺. More significantly, it shows excellent energy storage properties in Na/K‐ion full cells when coupled with Na₃V₂(PO₄)₂O₂F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high‐performance energy storage devices.     

Polyimide@Ketjenblack Composite: A Porous Organic Cathode for Fast Rechargeable Potassium‐Ion Batteries

Potassium‐ion batteries (PIBs) configurated by organic electrodes have been identified as a promising alternative to lithium‐ion batteries. Here, a porous organic Polyimide@Ketjenblack is demonstrated in PIBs as a cathode, which exhibits excellent performance with a large reversible capacity (143 mAh g^?1 at 100 mA g^?1), high rate capability (125 and 105 mAh g^?1 at 1000 and 5000 mA g^?1), and long cycling stability (76% capacity retention at 2000 mA g^?1 over 1000 cycles). The domination of fast capacitive‐like reaction kinetics is verified, which benefits from the porous structure synthesized using in situ polymerization. Moreover, a renewable and low‐cost full cell is demonstrated with superior rate behavior (106 mAh g^?1 at 3200 mA g^?1). This work proposes a strategy to design polymer electrodes for high‐performance organic PIBs.     

Sulfur‐Grafted Hollow Carbon Spheres for Potassium‐Ion Battery Anodes

Sulfur‐rich carbons are minimally explored for potassium‐ion batteries (KIBs). Here, a large amount of S (38 wt%) is chemically incorporated into a carbon host, creating sulfur‐grafted hollow carbon spheres (SHCS) for KIB anodes. The SHCS architecture provides a combination of nanoscale (≈40 nm) diffusion distances and C? S chemical bonding to minimize cycling capacity decay and Coulombic efficiency (CE) loss. The SHCS exhibit a reversible capacity of 581 mAh g^?1 (at 0.025 A g^?1), which is the highest reversible capacity reported for any carbon‐based KIB anode. Electrochemical analysis of S‐free carbon spheres baseline demonstrates that both the carbon matrix and the sulfur species are highly electrochemically active. SHCS also show excellent rate capability, achieving 202, 160, and 110 mAh g^?1 at 1.5, 3, and 5 A g^?1, respectively. The electrode maintains 93% of the capacity from the 5th to 1000th cycle at 3 A g^?1, with steady‐state CE being near 100%. Raman analysis indicates reversible breakage of C? S and S? S bonds upon potassiation to 0.01 V versus K/K⁺. The galvanostatic intermittent titration technique (GITT) analysis provides voltage‐dependent K⁺ diffusion coefficients that range from 10^?10 to 10^?12 cm² s^?1 upon potassiation and depotassiation, with approximately five times higher coefficient for the former.     

ZIF‐8@ZIF‐67‐Derived Nitrogen‐Doped Porous Carbon Confined CoP Polyhedron Targeting Superior Potassium‐Ion Storage

Potassium ion batteries (KIB) have become a compelling energy‐storage system owing to their cost effectiveness and the high abundance of potassium in comparison with lithium. However, its practical applications have been thwarted by a series of challenges, including marked volume expansion and sluggish reaction kinetics caused by the large radius of potassium ions. In line with this, the exploration of reliable anode materials affording high electrical conductivity, sufficient active sites, and structural robustness is the key. The synthesis of ZIF‐8@ZIF‐67 derived nitrogen‐doped porous carbon confined CoP polyhedron architectures (NC@CoP/NC) to function as innovative KIB anode materials is reported. Such composites enable an outstanding rate performance to harvest a capacity of ≈200 mAh g^?1 at 2000 mA g^?1. Additionally, a high cycling stability can be gained by maintaining a high capacity retention of 93% after 100 cycles at 100 mA g^?1. Furthermore, the potassium ion storage mechanism of the NC@CoP/NC anode is systematically probed through theoretical simulations and experimental characterization. This contribution may offer an innovative and feasible route of emerging anode design toward high performance KIBs.     

CuO Nanoplates for High‐Performance Potassium‐Ion Batteries

Potassium‐ion batteries (KIBs) are promising alternatives to lithium‐ion batteries because of the abundance and low cost of K. However, an important challenge faced by KIBs is the search for high‐capacity materials that can hold large‐diameter K ions. Herein, copper oxide (CuO) nanoplates are synthesized as high‐performance anode materials for KIBs. CuO nanoplates with a thickness of ≈20 nm afford a large electrode–electrolyte contact interface and short K⁺ ion diffusion distance. As a consequence, a reversible capacity of 342.5 mAh g^?1 is delivered by the as‐prepared CuO nanoplate electrode at 0.2 A g^?1. Even after 100 cycles at a high current density of 1.0 A g^?1, the capacity of the electrode remains over 206 mAh g^?1, which is among the best values for KIB anodes reported in the literature. Moreover, a conversion reaction occurs at the CuO anode. Cu nanoparticles form during the first potassiation process and reoxidize to Cu₂O during the depotassiation process. Thereafter, the conversion reaction proceeds between the as‐formed Cu₂O and Cu, yielding a reversible theoretical capacity of 374 mAh g^?1. Considering their low cost, easy preparation, and environmental benignity, CuO nanoplates are promising KIB anode materials.     

Porous Carbon Nanofibers Encapsulated with Peapod‐Like Hematite Nanoparticles for High‐Rate and Long‐Life Battery Anodes

Fe₂O₃ is regarded as a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe₂O₃ anodes, leading to rapid fading of the capacity. Herein, a novel peapod‐like nanostructured material, consisting of Fe₂O₃ nanoparticles homogeneously encapsulated in the hollow interior of N‐doped porous carbon nanofibers, as a high‐performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea‐like Fe₂O₃ nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na‐ions. As a consequence, this peapod‐like structure exhibits a stable discharge capacity of 1434 mAh g^?1 (at 100 mA g^?1) and 806 mAh g^?1 (at 200 mA g^?1) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g^?1 after 1000 cycles and 396 mAh g^?1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g^?1. This study provides a promising strategy for developing long‐cycle‐life LIBs and SIBs.     

Pyrolytic Carbon Nanosheets for Ultrafast and Ultrastable Sodium‐Ion Storage

Na‐ion cointercalation in the graphite host structure in a glyme‐based electrolyte represents a new possibility for using carbon‐based materials (CMs) as anodes for Na‐ion storage. However, local microstructures and nanoscale morphological features in CMs affect their electrochemical performances; they require intensive studies to achieve high levels of Na‐ion storage performances. Here, pyrolytic carbon nanosheets (PCNs) composed of multitudinous graphitic nanocrystals are prepared from renewable bioresources by heating. In particular, PCN‐2800 prepared by heating at 2800 °C has a distinctive sp² carbon bonding nature, crystalline domain size of ≈44.2 Å, and high electrical conductivity of ≈320 S cm^?1, presenting significantly high rate capability at 600 C (60 A g^?1) and stable cycling behaviors over 40 000 cycles as an anode for Na‐ion storage. The results of this study show the unusual graphitization behaviors of a char‐type carbon precursor and exceptionally high rate and cycling performances of the resulting graphitic material, PCN‐2800, even surpassing those of supercapacitors.     

Multidimensional Integrated Chalcogenides Nanoarchitecture Achieves Highly Stable and Ultrafast Potassium‐Ion Storage

Potassium‐ion batteries (KIBs) have come into the spotlight in large‐scale energy storage systems because of cost‐effective and abundant potassium resources. However, the poor rate performance and problematic cycle life of existing electrode materials are the main bottlenecks to future potential applications. Here, the first example of preparing 3D hierarchical nanoboxes multidimensionally assembled from interlayer‐expanded nano‐2D MoS₂@dot‐like Co₉S₈ embedded into a nitrogen and sulfur codoped porous carbon matrix (Co₉S₈/NSC@MoS₂@NSC) for greatly boosting the electrochemical properties of KIBs in terms of reversible capacity, rate capability, and cycling lifespan, is reported. Benefiting from the synergistic effects, Co₉S₈/NSC@MoS₂@NSC manifest a very high reversible capacity of 403 mAh g^?1 at 100 mA g^?1 after 100 cycles, an unprecedented rate capability of 141 mAh g^?1 at 3000 mA g^?1 over 800 cycles, and a negligible capacity decay of 0.02% cycle^?1, boosting promising applications in high‐performance KIBs. Density functional theory calculations demonstrate that Co₉S₈/NSC@MoS₂@NSC nanoboxes have large adsorption energy and low diffusion barriers during K‐ion storage reactions, implying fast K‐ion diffusion capability. This work may enlighten the design and construction of advanced electrode materials combined with strong chemical bonding and integrated functional advantages for future large‐scale stationary energy storage.     

A Novel Potassium‐Ion‐Based Dual‐Ion Battery

In this work, combining both advantages of potassium‐ion batteries and dual‐ion batteries, a novel potassium‐ion‐based dual‐ion battery (named as K‐DIB) system is developed based on a potassium‐ion electrolyte, using metal foil (Sn, Pb, K, or Na) as anode and expanded graphite as cathode. When using Sn foil as the anode, the K‐DIB presents a high reversible capacity of 66 mAh g^?1 at a current density of 50 mA g^?1 over the voltage window of 3.0–5.0 V, and exhibits excellent long‐term cycling performance with 93% capacity retention for 300 cycles. Moreover, as the Sn foil simultaneously acts as the anode material and the current collector, dead load and dead volume of the battery can be greatly reduced, thus the energy density of the K‐DIB is further improved. It delivers a high energy density of 155 Wh kg^?1 at a power density of 116 W kg^?1, which is comparable with commercial lithium‐ion batteries. Thus, with the advantages of environmentally friendly, cost effective, and high energy density, this K‐DIB shows attractive potential for future energy storage application.     

Surface‐Engineered Black Niobium Oxide@Graphene Nanosheets for High‐Performance Sodium‐/Potassium‐Ion Full Batteries

Nanoscale surface‐engineering plays an important role in improving the performance of battery electrodes. Nb₂O₅ is one typical model anode material with promising high‐rate lithium storage. However, its modest reaction kinetics and low electrical conductivity obstruct the efficient storage of larger ions of sodium or potassium. In this work, partially surface‐amorphized and defect‐rich black niobium oxide@graphene (black Nb₂O_5?x@rGO) nanosheets are designed to overcome the above Na/K storage problems. The black Nb₂O_5?x@rGO nanosheets electrodes deliver a high‐rate Na and K storage capacity (123 and 73 mAh g^?1, respectively at 3 A g^?1) with long‐term cycling stability. Besides, both Na‐ion and K‐ion full batteries based on black Nb₂O_5?x@rGO nanosheets anodes and vanadate‐based cathodes (Na_0.33V₂O₅ and K_0.5V₂O₅ for Na‐ion and K‐ion full batteries, respectively) demonstrate promising rate and cycling performance. Notably, the K‐ion full battery delivers higher energy and power densities (172 Wh Kg^?1 and 430 W Kg^?1), comparable to those reported in state‐of‐the‐art K‐ion full batteries, accompanying with a capacity retention of ≈81.3% over 270 cycles. This result on Na‐/K‐ion batteries may pave the way to next‐generation post‐lithium batteries.     

Boosting Zn‐Ion Energy Storage Capability of Hierarchically Porous Carbon by Promoting Chemical Adsorption

The construction of advanced Zn‐ion hybrid supercapacitors (ZHSCs) with high energy density is promising but still challenging, especially at high current densities. In this work, a high‐energy and ultrastable aqueous ZHSC is demonstrated by introducing N dopants into a hierarchically porous carbon cathode for the purpose of enhancing its chemical adsorption of Zn ions. Experimental results and theoretical simulations reveal that N doping not only significantly facilitates the chemical adsorption process of Zn ions, but also greatly increases its conductivity, surface wettability, and active sites. Consequently, the as‐fabricated aqueous ZHSC based on this N‐doped porous carbon cathode displays an exceptionally high energy density of 107.3 Wh kg^?1 at a high current density of 4.2 A g^?1, a superb power density of 24.9 kW kg^?1, and an ultralong‐term lifespan (99.7% retention after 20 000 cycles), substantially superior to state‐of‐the‐art ZHSCs. Particularly, such a cathode also leads to a quasi‐solid‐state device with satisfactory energy storage performance, delivering a remarkable energy density of 91.8 Wh kg^?1. The boosted energy storage strategy by tuning the chemical adsorption capability is also applicable to other carbon materials.     

Flexible Graphene‐Wrapped Carbon Nanotube/Graphene@MnO2 3D Multilevel Porous Film for High‐Performance Lithium‐Ion Batteries

The ingenious design of a freestanding flexible electrode brings the possibility for power sources in emerging wearable electronic devices. Here, reduced graphene oxide (rGO) wraps carbon nanotubes (CNTs) and rGO tightly surrounded by MnO₂ nanosheets, forming a 3D multilevel porous conductive structure via vacuum freeze‐drying. The sandwich‐like architecture possesses multiple functions as a flexible anode for lithium‐ion batteries. Micrometer‐sized pores among the continuously waved rGO layers could extraordinarily improve ion diffusion. Nano‐sized pores among the MnO₂ nanosheets and CNT/rGO@MnO₂ particles could provide vast accessible active sites and alleviate volume change. The tight connection between MnO₂ and carbon skeleton could facilitate electron transportation and enhance structural stability. Due to the special structure, the rGO‐wrapped CNT/rGO@MnO₂ porous film as an anode shows a high capacity, excellent rate performance, and superior cycling stability (1344.2 mAh g⁻¹ over 630 cycles at 2 A g⁻¹, 608.5 mAh g⁻¹ over 1000 cycles at 7.5 A g⁻¹). Furthermore, the evolutions of microstructure and chemical valence occurring inside the electrode after cycling are investigated to illuminate the structural superiority for energy storage. The excellent electrochemical performance of this freestanding flexible electrode makes it an attractive candidate for practical application in flexible energy storage.     

Red Phosphorus Nanoparticle@3D Interconnected Carbon Nanosheet Framework Composite for Potassium‐Ion Battery Anodes

Red phosphorus (P) has been recognized as a promising storage material for Li and Na. However, it has not been reported for K storage and the reaction mechanism remains unknown. Herein, a novel nanocomposite anode material is designed and synthesized by anchoring red P nanoparticles on a 3D carbon nanosheet framework for K‐ion batteries (KIBs). The red P@CN composite demonstrates a superior electrochemical performance with a high reversible capacity of 655 mA h g^?1 at 100 mA g^?1 and a good rate capability remaining 323.7 mA h g^?1 at 2000 mA g^?1, which outperform reported anode materials for KIBs. The transmission electron microscopy and theoretical calculation results suggest a one‐electron reaction mechanism ofP + K⁺ + e^?→ KP, corresponding to a theoretical capacity of 843 mA h g^?1,which is the highest value for anode materials investigated for KIBs. The study not only sheds light on the rational design of high performance red P anodes for KIBs but also offers a fundamental understanding of the potassium storage mechanism of red P.     

Electrolyte‐Dependent Sodium Ion Transport Behaviors in Hard Carbon Anode

A comprehensive study is conducted on hard carbon (HC) series samples by tuning the graphitic local microstructures systematically as an anode for SIBs in both carbonate‐ (CBE) and glyme‐based electrolytes (GBE). The results reveal more detailed charge storage characters of HCs on the LVP section. 1) The LVP capacity is closely related to the prismatic surface area to the basal plane as well as the bulk density, regardless of electrolyte systems. 2) The glyme‐sodium ion complex can facilitate sodium ion delivery into the internal closed pores of the HCs along with not well‐ordered graphitic structures. 3) The glyme‐mediated sodium ion‐storage behavior causes significant decreases in both surface film resistance and charge transfer resistance, leading to enhanced rate capability. 4) The LVP originates from the formation of pseudo‐metallic sodium nanoclusters, which are the same in a CBE and GBE. These results provide insight into the sodium ion‐storage behaviors of HCs, particularly on the interrelationship between graphitic local microstructures and electrolyte systems. In addition, a high‐performance HC anode with a plateau capacity of ≈300 mA h g^?1 is designed based on the information, and its workability is demonstrated in a full‐cell SIB device.