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The Co‐free Ni‐rich layered cathode materials with excellent structural stability and low‐cost in Ni‐rich family are emerging as the promising candidates for the next generation of high‐energy density cathodes. Previously, Mn is generally regarded as the structural stabilizer in Co‐free Ni‐rich cathodes, while the role of inevitable Li/Ni intermixing is underestimated. Herein, the study reveals that the real origin of the lattice oxygen/structure stability of Co‐free Ni‐rich cathodes is dominated more by Li/Ni intermixing than the widely accepted Mn. In the Li/Ni intermixing configuration, the intermixed Ni ions can suppress the oxidation of lattice oxygen by increasing the formation energy of oxygen vacancy and reducing charge compensation. Besides, the Li vacancy formed via the delithiation of intermixed Li in transition metal layer can serve as O2 capture sites. This dual stabilization mechanism is proposed and proved to be effectively in enhancing the reversibility of lattice oxygen and the stability of material structural. This work sheds light on the mechanism of stabilizing lattice oxygen through Li/Ni intermixing, which provides new insights for designing better batteries. [ABSTRACT FROM AUTHOR]

The rationally structural engineering is an efficient strategy to improve the comprehensive performance of potassium‐ion storage anode materials. In this paper, a hybrid with hollow FeS2 nanoparticles anchored into the 3D carbon skeleton (labeled as H‐FeS2@3DCS) is successfully constructed through two critical steps of in situ chemical deposition and anion‐exchange reaction strategies. In the former, the water‐soluble Na2CO3 crystals are used as hard templates for the preparation of 3DCS, while Fe3+‐containing aqueous solutions are utilized to remove the Na2CO3 templates. Interestingly, the intense collision between Fe3+ and CO32‐ in aqueous solution produces nanoscale Fe(OH)3 colloidal particles, which are firmly anchored into the pores of the carbon skeleton to form a "lotus‐seed"‐like nanostructure. In the latter case, a central void space is created inside the FeS2 nanoparticles due to the different diffusion rates of S‐anions and Fe‐cations during the subsequent sulfidation process. Thanks to this unique composition model, the H‐FeS2@3DCS hybrid not only alleviates the volume expansion efficiently by rationally hollow structure design, but also provides spacious "roads" (3D carbon skeleton) and "houses" (hollow FeS2 nanoparticles) for fast K‐ion transition and storage. As the anode of PIBs and PIHCs, the resultant H‐FeS2@3DCS electrode delivers an obviously enhanced K‐ions storage performance over state‐of‐the‐art. [ABSTRACT FROM AUTHOR]

Enhancing pseudocapacitance of Ti 3 C 2 T x MXene-based electrode materials induced by sufficient surface terminating groups (such as Ti–O bonding) becomes one promising way for fabricating high energy-density supercapacitors. However, most of terminating group activity cannot be excited well in the multilayer Ti 3 C 2 T x due to the layer stacking feature, which limits its further performance improvement. In this paper, a CQDs@Ti 3 C 2 T x hybrid material is synthesized by modifying few-layer Ti 3 C 2 T x MXene matrix with highly dispersed carbon quantum dots (CQDs). In this unique hybrid model, the Ti 3 C 2 T x MXene matrix with high conductivity and high specific surface area is just like the "paddy field", which not only promotes the charge rapid transfer, but also provides the high double layer capacitance by ion adsorption. More importantly, the CQDs act as "rice seedlings" firmly anchored to the Ti 3 C 2 T x matrix, and greatly stimulate the activity of the termination groups of Ti 3 C 2 T x. As expected, this hybrid achieves a harmonious coexistence of high conductivity and high pseudocapacitance. As a result, the CQDs@Ti 3 C 2 T x electrode delivers high reversible capacitances of 441.3 F g−1 at 1 A g−1 and 310.1 F g−1 at 20 A g−1, and a relatively stable cyclability with almost 100% capacitance retention after 10 000 cycles at 10 A g−1. A CQDs@Ti 3 C 2 T x hybrid is facilely designed, in which the activity of Ti–O bonding is excited well to enhance its pseudocapacitance. Consequently, this resultant CQDs@Ti 3 C 2 T x realizes a comprehensive energy storage ability. This strategy may provide a promising approach to fabricate high-performance MXene based electrode. [Display omitted] [ABSTRACT FROM AUTHOR]

A NS-C@b-MoS 2 hybrid is readily fabricated with bilayer MoS 2 molecules grafted onto 3D N/S doped carbon capsule skeleton in one tailored spatial-chemical doubly confined mode. The MoS 2 bilayer can expose more S-Mo-S bonds to adsorb K-ions. Together with the support effect of carbon skeleton, consequently, this NS-C@b-MoS 2 hybrid electrode achieves an ultra-fast and ultra-stable potassium-ion storage capability. [Display omitted] • A tailored induced vapour-deposition strategy to construct a MoS 2 /C hybrid. • MoS 2 with bilayer structure can expose more S-Mo-S bonds to adsorb K-ions. • One spatial-chemical doubly confined mode to enhance the MoS 2 bilayer stability. • The assembled PIC deliver an ultra-stable performance up to 65,000 cycles. Few-layers MoS 2 -based materials have a comprehensive advantage in accommodating potassium-ions due to the rich active S-Mo-S sites and rapid ionic dynamics. Unfortunately, the serious self-stacking of MoS 2 molecular layer resulted in insufficient space to buffer the stress/strain caused by K-ions intercalation, which makes MoS 2 -based electrode exhibits low capacitance and poor cyclic stability in practical studies. To solve this, an in situ induced deposition strategy is proposed to construct a MoS 2 /C hybrid (labelled as NS-C@b-MoS 2). In this NS-C@b-MoS 2 hybrid, the MoS 2 molecular with bilayer structure is grafted onto a 3D N/S dual-doping carbon skeleton in one spatial-chemical doubly confined mode. This unique hybrid mode not only expose more S-Mo-S bonds to adsorb K-ions, but also avoid the structural collapse of electrode by spatial-chemical doubly confinement effect of carbon skeleton. Consequently, the resultant NS-C@b-MoS 2 anode delivers a high specific capacity of 451.2 mAh g−1 at 0.1 A g−1 and an ultra-long cycle stability up to 20,000 cycles with only 0.0013 % fading per cycle. Moreover, the assembled NS-C@b-MoS 2 //NSAC potassium-ion capacitor delivers a high energy density of 126.5 Wh kg−1 and retains 55.2 Wh kg−1 after 65,000 cycles at 3800 W kg−1, which over the state-of-the-art reported performance. [ABSTRACT FROM AUTHOR]

Self‐direction has become an important skill in the 21st century. To cultivate learners with a high level of self‐direction, it is necessary to diagnose their self‐directed learning (SDL) ability. This study diagnosed and predicted learners' SDL ability based on their actual SDL behaviours. The study was performed in a self‐directed 3D design class lasting 90 minutes. A total of 193 middle school students participated in the study. The results of the Pearson correlation analysis (p < 0.001) showed that the reported perception of SDL ability was significantly correlated with SDL behaviours. The results of the hierarchical multiple linear regression analysis showed that the SDL behaviours explained 84.9% of the variance in SDL ability (adjusted R2 = 0.849, p < 0.001). Therefore, SDL behaviours had significant predictive effects on the reported perception of SDL ability. Moreover, based on the random forest algorithm, the study built an SDL ability prediction model with high performance (accuracy = 0.83, precision = 0.82, recall = 0.84) using SDL behaviours as features. The study provides evidence for the design of effective strategies to enhance SDL ability and promote SDL behaviours.Practitioner notesWhat is already known about this topicTo cultivate learners with a high level of self‐direction, it is necessary to diagnose their self‐directed learning (SDL) ability.SDL is a combination of internal personal attributes and external autonomous behaviours.Few studies have focused on diagnosing SDL ability based on learners' external SDL behaviours occurring during the learning process.What this paper addsThe reported perception of SDL ability was significantly correlated with SDL behaviours.SDL behaviours had significant predictive effects on the reported perception of SDL ability.Based on the random forest algorithm, the study built an SDL ability prediction model with high performance using SDL behaviours as features.Implications for practice and/or policyThe findings indicate that instructors could design effective strategies to promote SDL behaviours for the purpose of enhancing learners' SDL ability.The method and process of building an SDL ability prediction model might provide a reference for related research on ability prediction with behaviours. [ABSTRACT FROM AUTHOR]

• A brand-new two-step reaction mechanism of ONA electrode is proposed in AIB. • The π-π stacking structures of π-COCs can contribute capacity directly. • The ONA show the co-existence of high capacity and excellent cycle stability in AIB. Π-conjugated organic compounds (π-COCs), as a potential electrode material, mainly emphasized the effects of functional groups and intramolecular π-conjugated system on charge storage in the past studies. In this work, we discovered a brand-new two step energy storage mechanism for π-COCs using oligomeric naphthalene (ONA) with intermolecular π-π stacking structure as electrode material in Al ion battery system. The electrochemical reaction of ONA is identified as the synergistic work of the chemical-adsorption of AlCl 4 - anions at low potential and the π···[AlCl 4 ]···π interaction at high potential. Based on this, the Al-ONA battery exhibits an excellent electrochemical performance (high specific capacity of 450 mAh/g at 0.1 A/g, long cycle life without attenuation for 4000 cycles at 1 A/g). This discovery of the energy storage mechanism, especially for the π···anion···π interaction, for π-COCs materials opens the door to exploring high performance organic electrode materials in energy storage field. [ABSTRACT FROM AUTHOR]

LiFePO4 is one of the most widely used cathode materials for lithium‐ion batteries, and the low‐temperature performance of LiFePO4‐based batteries has been widely studied in recent years. Herein, a 3.5 Ah pouch‐type full battery was assembled using LiFePO4 as the cathode and artificial graphite as the anode. For the LiFePO4‐based cathode, carbon‐coated aluminum foil was selected as the current collector, and a 0D–1D–2D multi‐scale conductive network was introduced into the electrode. Notably, both the carbon‐coated current collector and novel conductive network could significantly reduce the internal resistance of the LiFePO4‐based battery, thus improving its electrochemical dynamics and low‐temperature performance. This paper provides a theoretical basis for the development of low‐temperature LiFePO4‐based batteries. [ABSTRACT FROM AUTHOR]

• Electrolyte is optimized for low-temperature LiFePO 4 -graphite battery. • Multi-component solvent system improves the ionic conductivity at low temperature. • Film-forming additives promote the formation of solid electrolyte interface film. • The optimized battery exhibits excellent performance at low temperatures. The design of electrolyte is crucial to improve the low temperature electrochemical performance of the LiFePO 4 -graphite battery. In this paper, by optimizing the solvent composition and introducing film-forming additives in the electrolyte, the low temperature performance of the battery is significantly improved. In detail, the EP (ethyl propionate) solvent with low melting point and low viscosity is added to the original EC (ethylene carbonate)-EMC (ethyl methyl carbonate)-DMC (dimethyl carbonate) solvent systems, which improved the ionic conductivity of the electrolyte, especially at low temperature (−40 °C). On the other hand, the introduction of FEC (fluoroethylene carbonate)/DTD (ethylene sulfate) film-forming agents promotes the formation of SEI (solid electrolyte interface) film, and the SEI is thin and uniform. As a result, the LiFePO 4 -graphite battery exhibits high capacity and long cycle life under low temperature conditions. [ABSTRACT FROM AUTHOR]

As an emerging post‐lithium battery technology, aluminum ion batteries (AIBs) have the advantages of large Al reserves and high safety, and have great potential to be applied to power grid energy storage. But current graphite cathode materials are limited in charge storage capacity due to the formation of stage‐4 graphite‐intercalated compounds (GICs) in the fully charged state. Herein, we propose a new type of cathode materials for AIBs, namely polycyclic aromatic hydrocarbons (PAHs), which resemble graphite in terms of the large conjugated π bond, but do not form GICs in the charge process. Quantum chemistry calculations show that PAHs can bind AlCl4− through the interaction between the conjugated π bond in the PAHs and AlCl4−, forming on‐plane interactions. The theoretical specific capacity of PAHs is negatively correlated with the number of benzene rings in the PAHs. Then, under the guidance of theoretical calculations, anthracene, a three‐ring PAH, was evaluated as a cathode material for AIBs. Electrochemical measurements show that anthracene has a high specific capacity of 157 mAh g−1 (at 100 mA g−1) and still maintains a specific capacity of 130 mAh g−1 after 800 cycles. This work provides a feasible "theory guides practice" research model for the development of energy storage materials, and also provides a new class of promising cathode materials for AIBs. [ABSTRACT FROM AUTHOR]

As an emerging post‐lithium battery technology, aluminum ion batteries (AIBs) have the advantages of large Al reserves and high safety, and have great potential to be applied to power grid energy storage. But current graphite cathode materials are limited in charge storage capacity due to the formation of stage‐4 graphite‐intercalated compounds (GICs) in the fully charged state. Herein, we propose a new type of cathode materials for AIBs, namely polycyclic aromatic hydrocarbons (PAHs), which resemble graphite in terms of the large conjugated π bond, but do not form GICs in the charge process. Quantum chemistry calculations show that PAHs can bind AlCl4− through the interaction between the conjugated π bond in the PAHs and AlCl4−, forming on‐plane interactions. The theoretical specific capacity of PAHs is negatively correlated with the number of benzene rings in the PAHs. Then, under the guidance of theoretical calculations, anthracene, a three‐ring PAH, was evaluated as a cathode material for AIBs. Electrochemical measurements show that anthracene has a high specific capacity of 157 mAh g−1 (at 100 mA g−1) and still maintains a specific capacity of 130 mAh g−1 after 800 cycles. This work provides a feasible "theory guides practice" research model for the development of energy storage materials, and also provides a new class of promising cathode materials for AIBs. [ABSTRACT FROM AUTHOR]

N-doping can endow carbon materials with high electrochemical activity. Besides the widely validated sp 2 -hybridized nitrogen doping, sp -hybridized nitrogen (sp - N) atoms are also expected to be new active sites. However, both sp - N atoms and cyano (CN) groups containing sp - N are rarely produced in carbon materials presently. In this work, the first cyano groups-modified carbon materials are synthesized firstly via an interesting struggle between the chemical etching of KOH and the catalytic graphitization of Co nanoparticles in carbon frameworks. The theoretical calculations and experimental results manifest that the stronger electronegativity of CN groups renders carbon materials a higher electrochemical activity. As K+ storage anodes, the CN−modified carbon materials exhibit an obvious boost in potassium storage performance in both ester- and ether-based electrolytes. Therefore, as a new N doping form, the successful introduction of CN groups into carbon materials opens a door for exploring sp -N doped carbon materials for applications in energy storage and other fields. [Display omitted] • The first cyano-modified carbon materials are prepared. • As K+ storage anodes, the CN-modified carbon exhibits the impressive performance. • The storage mechanism of CN was explored by theoretical calculation and test. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonic induced rGO self-encapsulation of S, N dual-doped carbon spheres. • The rGO acts as a protective shield and a filter. • Pseudocapacitance contribution of high S, N co-doped carbon spheres. • Up to 60% Initial Coulomb Efficiency. Pseudocapacitance points out a new direction for the recent research and development of potassium ion anode materials because of its fast energy storage kinetics, which has yielded lots of successful pseudocapacitance-rich examples by introducing more active sites such as doped heteroatoms. However, the negative reactions with the electrolyte in electrochemical process often cause the serious inactivation of active sites, giving a hit for seeking higher pseudocapacitance. In this work we proposed a new strategy to wrap the protective shield for the pseudocapacitance-rich materials to alleviate this matter. By the ultrasonic-induced rGO self-encapsulation of S, N dual-doped carbon spheres, the directional contact between active sites and the electrolyte is blocked, while the rGO films with enlarged interlayer spacing and lots of defects also like filter membrane, accelerate the K+ desolvation and fast diffusion into carbon matrix. Benefiting from the synergistic effect of rGO shielding and filtrating, the pseudocapacitance of S, N dual-doping carbon spheres is fully activated. As the potassium-ion battery anode, the obtained S, N dual-doping carbon sphere@rGO delivers a state-of-the-art capacity of 596 mAh g−1, which achieves a 52.5 % capacity enhancement in contrast to that without rGO shield. As a proof of application, the resultant high-pseudocapacitance carbon anode is incorporated into a potassium ion hybrid capacitor, showing the most favorable capacity-cyclability combinations with the high energy–density of 83 Wh kg−1 after 6500 cycles at 5A g−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trace nitrogen atoms are successfully inserted into the surface of Ni metal. • Trace nitrogen-incorporation can greatly activate monometallic Ni catalysts. • Apparent charge redistribution of Ni occurs at micro-heterogeneous interfaces. • It shifts the d-band center of Ni atoms for favorable adsorption kinetics. • The synergistic dual-active sites enhance HOR performance. The insufficient activity of Ni-based catalysts toward hydrogen oxidation reaction (HOR) severely hinders their deployment in alkaline polymer electrolyte fuel cells. Here, we demonstrate that trace nitrogen-incorporation can greatly activate monometallic Ni catalysts by constructing synergetic dual active sites across micro-heterogeneous interfaces, resulting in impressive HOR electrocatalytic performance that rivals that of state-of-the-art Pt/C catalysts in alkaline media. The obtained catalyst achieves a high specific activity of 0.074 mA cm−2, a high mass activity of 60.9 A g−1, and outperforms both Ni 3 N and Ni analogues, uncovering an unexpected nitrogen-incorporation criterion for Ni electrocatalysts. Moreover, it also exhibits a remarkable CO tolerance capacity that Pt/C lacks. Mechanistic studies reveal that self-regulated d-band centers of Ni (downshift) in Ni-N bonding and Ni (upshift) in Ni-Ni bonding derived from apparent charge redistribution can weaken hydrogen binding energy and increase hydroxyl binding energy simultaneously, resulting in the HOR enhancement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni 3 N/Ni/N-doped graphite nanoflakes was designed for hydrogen oxidation reaction. • Customized N-doped graphite nanoflakes significantly enhance corrosion resistance. • Ni 3 N/Ni heterostructure optimizes the binding energy of intermediates. • The synergy between Ni species and support delivers superior mass activity. Designing electrocatalysts for hydrogen oxidation reaction (HOR) in alkaline media is crucial but challenging. Among all available electrocatalysts, Ni-based materials are recognized as the most potential precious-metal-free electrocatalysts for HOR. However, they still suffer from serious problems including low activity and poor stability. In this work, a synergistic chemical anchoring and electronic structure regulation strategy is proposed to gain both high electrocatalytic activity and stability for Ni-based HOR catalyst. N-doped graphite nanoflakes (N-GFs) support with abundant N anchoring sites can stabilize the loading of Ni-based active species, giving rise to an excellent stability of the catalyst. Meanwhile, the rationally designed heterostructure in the active Ni 3 N/Ni can trigger the electron transfer across the heterointerface, which optimizes the binding energy of the reaction intermediates, resulting in an accelerated the Volmer reaction. Benefited from the rational design, Ni 3 N/Ni/N-GFs exhibits excellent mass activity (42.7 A g Ni -1 at the overpotential of 50 mV) and stability (more than 24 h continuous operation). Moreover, the Ni 3 N/Ni heterostructure performs better in HOR electrocatalysis than individual Ni or Ni 3 N. These experimental results are rationalized by the theoretical simulations, which demonstrate that the heterostructure effectively weakens the hydrogen adsorption, optimizes the hydroxyl adsorption, and decreases the water formation reaction barrier. [ABSTRACT FROM AUTHOR]

Polythiophene (Pth) is a good candidate cathode material for aluminum ion battery (AIB) because of its lightness, safety, plasticity and flexibility. However, it always manifests inferior stability. Herein, a stable Pth-based cathode is realized through the anchoring effect between Pth and carboxyl. Pth with a thin film morphology is in situ synthesized on the surface of carboxylated carbon nanotubes (CNT-COOH). As a support, CNT-COOH not only alleviates the agglomeration of Pth that provides abundant transport channels for ions and electrons simultaneously, but also enhances the stability of Pth through the anchoring effect. As a result, the prepared Pth/CNT-COOH composite exhibits high discharge capacity (113 mAh g−1 at 1 A g−1), outstanding rate performance (95 mAh g−1 at 5 A g−1) and stable cycle stability (10,000 cycles with 0.001% decay per cycle). This work realizes a promising Pth-based AIBs with high capacity and long lifespan, which paves the way to the applications of organic materials in AIBs. [ABSTRACT FROM AUTHOR]