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Vanadate materials are promising for sodium‐ion batteries (SIBs) due to their low cost, high capacity, and high power characteristics enabled by vanadium's multiple oxidation states. However, their development is hindered by poor conductivity, suboptimal high‐rate performance, and limited cycle life. In this work, a layered structure modification strategy involving Ca/F co‐doping in sodium vanadate Na2CaV2O6F (CVF) is proposed to address these issues. Through a combination of experiments and density functional theory calculations, it is demonstrated that Ca/F synergies enhance the Na layer spacing in CVF, resulting in reduced crystal water content and volume shrinkage compared to Na2V2O6 (NVO). Additionally, Ca/F incorporation significantly mitigates the diffusion potential of Na+ within the material framework. The unmodified CVF sample exhibits a high reversible capacity of 220 mAh g−1 at 10 mA g−1 and an excellent rate capacity of 65.78 mAh g−1 at 400 mA g−1. Furthermore, the cathode material maintains a capacity of up to 138 mAh g−1 at 200 mA g−1 and retains 104.88 mAh g−1 after 100 cycles within the voltage range of 1.5−4.0 V. These findings enhance the understanding of the crystal structure of NVO cathode materials and pave the way for the rational design of high‐quality vanadate cathodes for SIBs. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO)‐based solid‐state batteries hold great promise as the next‐generation batteries with high energy density and high safety. However, PEO‐based electrolytes encounter certain limitations, including inferior ionic conductivity, low Li+ transference number, and poor mechanical strength. Herein, we aim to simultaneously address these issues by utilizing one‐dimensional zwitterionic cellulose nanofiber (ZCNF) as fillers for PEO‐based electrolytes using a simple aqueous solution casting method. Multiple characterizations and theoretical calculations demonstrate that the unique zwitterionic structure imparts ZCNF with various functions, such as disrupting PEO crystallization, dissociating lithium salts, anchoring anions through cationic groups, accelerating Li+ migration by anionic groups, as well as its inherent reinforcement effect. As a result, the prepared PL‐ZCNF electrolyte exhibits remarkable ionic conductivity (5.37×10−4 S cm−1) and Li+ transference number (0.62) at 60 °C without sacrificing mechanical strength (9.2 MPa), together with high critical current density of 1.1 mA cm−2. Attributed to these merits of PL‐ZCNF, the LiFePO4|PL‐ZCNF|Li solid‐state full‐cell delivers exceptional rate capability and cycling performance (900 cycles at 5 C). Notably, the assembled pouch‐cell can maintain steady operation over 1000 cycles with an impressive 93.7 % capacity retention at 0.5 C and 60 °C, highlighting the great potential of PL‐ZCNF for practical applications. [ABSTRACT FROM AUTHOR]

Micro‐sized bismuth (Bi) is recognized for its high volumetric capacity and suitable working potential, making it a promising anode candidate for sodium‐ion batteries (SIBs). However, its substantial volume changes and slow reaction kinetics during cycling detrimentally affects the SIB performance. Theoretical prediction uncovers a previously unexplored favorable attribute that bonding between nitrogen within a carbon coating and Bi atoms facilitates Na+ ingress into the Bi bulk, significantly enhancing Bi‐Na alloying reactions, mitigating volume expansion, and preventing Na‐dendrite formation. Experimentally, the study innovatively engineers a flower‐like micro‐sized Bi encapsulated within an elastic, nitrogen‐doped carbon framework (FBi@NC) working as an efficient anode for SIBs. This design enables FBi@NC anode achieving a high tap density of 2.86 g cm−3 and delivering a remarkable volumetric capacity of 1100 mAh cm−3 at 1 mA cm−2. It also exhibits exceptional rate capability (368.2 mA h g−1 at 30 A g−1) and super durable cyclability (10 000 cycles with 318.8 mA h g−1 at 5 A g−1, retaining 82% capacity). Full cells with Na3V2(PO4)3 cathodes demonstrate superior rate and cycling performances. Crucially, this study elucidates the underlying Na+‐storage mechanisms and the contributory factors to performance enhancement, providing vital insights for the development of high‐energy and stable SIBs. [ABSTRACT FROM AUTHOR]

The Li21Si5 alloy is a promising pre-lithiation material for lithium-ion batteries (LIBs). However, its instability in atmospheric environments and polar solutions limits its applications, particularly in the field of water-based anodes. Herein, a PEO-Li21Si5 coating strategy was proposed to efficiently replenish lithium and stabilize the electrode structure for LIBs. Polyethylene oxide (PEO) was added to Li21Si5 to create a PEO-Li21Si5 pre-lithiation layer, which was coated on the surface of the Si@C anode. HRTEM and XPS tests indicated that the PEO (weakly polar) would react with the interface of the Li21Si5 to build a stable passivation layer, allowing lithium ions inside the Li21Si5 to be released during the first cycle, which in turn improved the ICE of the LIBs. Moreover, PEO-Li21Si5 was able to coat the Si@C particles due to the wettability of the electrolyte to PEO. And it would suppress the displacement caused by the cyclic expansion of the Si, achieving the stability of the electrode structure. This strategy achieved an initial coulombic efficiency (ICE) of over 100% with stable and long-lasting cycles. [ABSTRACT FROM AUTHOR]

Alloying‐type antimony (Sb) with high theoretical capacity is a promising anode candidate for both lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). Given the larger radius of Na+ (1.02 Å) than Li+ (0.76 Å), it was generally believed that the Sb anode would experience even worse capacity degradation in SIBs due to more substantial volumetric variations during cycling when compared to LIBs. However, the Sb anode in SIBs unexpectedly exhibited both better electrochemical and structural stability than in LIBs, and the mechanistic reasons that underlie this performance discrepancy remain undiscovered. Here, using substantial in situ transmission electron microscopy, X‐ray diffraction, and Raman techniques complemented by theoretical simulations, we explicitly reveal that compared to the lithiation/delithiation process, sodiation/desodiation process of Sb anode displays a previously unexplored two‐stage alloying/dealloying mechanism with polycrystalline and amorphous phases as the intermediates featuring improved resilience to mechanical damage, contributing to superior cycling stability in SIBs. Additionally, the better mechanical properties and weaker atomic interaction of Na−Sb alloys than Li−Sb alloys favor enabling mitigated mechanical stress, accounting for enhanced structural stability as unveiled by theoretical simulations. Our finding delineates the mechanistic origins of enhanced cycling stability of Sb anode in SIBs with potential implications for other large‐volume‐change electrode materials. [ABSTRACT FROM AUTHOR]

Compensating the irreversible loss of limited active lithium (Li) is essentially important for improving the energy‐density and cycle‐life of practical Li‐ion battery full‐cell, especially after employing high‐capacity but low initial coulombic efficiency anode candidates. Introducing prelithiation agent can provide additional Li source for such compensation. Herein, we precisely implant trace Co (extracted from transition metal oxide) into the Li site of Li2O, obtaining (Li0.66Co0.11□0.23)2O (CLO) cathode prelithiation agent. The synergistic formation of Li vacancies and Co‐derived catalysis efficiently enhance the inherent conductivity and weaken the Li−O interaction of Li2O, which facilitates its anionic oxidation to peroxo/superoxo species and gaseous O2, achieving 1642.7 mAh/g~Li2O prelithiation capacity (≈980 mAh/g for prelithiation agent). Coupled 6.5 wt % CLO‐based prelithiation agent with LiCoO2 cathode, substantial additional Li source stored within CLO is efficiently released to compensate the Li consumption on the SiO/C anode, achieving 270 Wh/kg pouch‐type full‐cell with 92 % capacity retention after 1000 cycles. [ABSTRACT FROM AUTHOR]

Developing high‐capacity conversion‐type anodes with superior durability substituting conventional graphite anodes is urgently desired to improve the energy density of lithium‐ion batteries (LIBs). However, fatal capacity decay during cycling of the conversion‐type anodes, which is primarily due to their inevitable structural degradation and continuous solid‐electrolyte interphase reformation induced by drastic volume change, has highly restricted their commercialization. And, the interrelated effects of phase transformation, structural evolution, and electrochemical characteristics of the conversion‐type anodes during cycling remain poorly understood. Herein, the findings on the fabrication and understanding of a previously unexplored entropy‐stabilized spinel oxide, (Co0.2Mn0.2V0.2Fe0.2Zn0.2)3O4 as a promising conversion anode for LIBs, exhibiting not only moderate volume change character but also highly reversible capacities of ≈900 mAh g−1 for 500 cycles at 0.2 A g−1 and ≈500 mAh g−1 for 2000 cycles at 3 A g−1, respectively, are reported. Evidenced by in situ transmission electron microscopy coupled with theoretical calculations, its underlying mechanism underpinning highly reversible Li storage is explicitly revealed, which originates from reversible phase transformation and domain reconstruction during cycling. Moreover, the origin of small volume change is also clearly clarified. This work provides renewed mechanistic insights into designing high‐capacity and durable conversion‐type electrode materials for high‐performance LIBs. [ABSTRACT FROM AUTHOR]

Rechargeable batteries that make renewable energy resources feasible for electrification technologies have been extensively investigated. Their corresponding performance is strongly dependent on the structural characteristics and chemical dynamics of internal electrode and electrolyte materials under operating conditions. To enhance battery performance and lifetime, a comprehensive understanding of the structure‐dynamics‐performance correlation of such materials under different working conditions is of great significance. Fortunately, in situ transmission electron microscopy (TEM) encompassing high‐resolution imaging, diffraction, and spectroscopic analysis, offers unprecedented insights into the nano/atomic scale structural changes and degradation pathways of rechargeable battery materials under operational conditions. Such insights are pivotal for a deep‐rooted understanding of reaction mechanisms and the structure‐activity interplay within battery materials. This work, therefore, highlights the advances in in situ TEM's utility in unveiling dynamic chemical and physical changes in real‐time within battery materials of rechargeable batteries. Electrochemical processes and degradation mechanisms are systematically explored and summarized. Moreover, the technical progress, challenges, and valuable insights provided by in situ TEM techniques for addressing critical issues in battery materials are underscored. The work concludes with a discussion of emerging research directions that hold the potential to revolutionize the renewable energy field in the near future. [ABSTRACT FROM AUTHOR]

Bismuth (Bi)‐based materials merit high theoretical volumetric specific capacity (3800 mAh mL⁻1) but suffer from huge volume variations and sluggish reaction kinetics during cycling. Herein, the optimal framework of Bi/Bi2O3 nanodots enriched in suitable outer amorphous carbon sheets (Bi/Bi2O3 NDs@CSs) is first proposed to alleviate volume variations and accelerate stable charge transport to boost K+ storage performance. The introduction of proper Bi2O3 not only provides an efficient K+ adsorption path, but also effectively buffers volume changes via conversion reaction. Accordingly, the as‐prepared anode exhibits a remarkable rate capability (149.3 mAh g−1 at 60 A g−1, 42% capacity retention with a 120‐fold current‐density increase) and extraordinary durability (1800 cycles at 5.0 A g−1, 95% capacity retention), among the best rate and cycling performance to date in potassium ion batteries (PIBs) anodes. Theoretical calculations reveal the feasible structures of Bi/Bi2O3 NDs@CSs with double protection of carbon sheets and Bi2O3 are conducive to enhance charge transfer and efficiency of electrochemical reaction. Substantial in situ/ex situ characterizations and finite element simulation further unveil high reversibility and robust mechanical behavior of Bi/Bi2O3 NDs@CSs, favorable for the reinforcement of structural stability. This study provides new insights into developing high‐performance and durable Bi‐based anodes for PIBs. [ABSTRACT FROM AUTHOR]

N‐doped carbons, as promising anode materials for energy storage, are generally modified by the additional heteroatoms (B, P, and S) doping to further promote the electrochemical performance. However, the promotion mechanism by such additional doping, especially its interplay with N‐containing species, remains unclear. Herein, by adopting N/S co‐doped carbon as a model system, it is found that S‐doping can significantly improve the content of pyridinic‐N, i.e., the most energetically favorable N type for K+ storage. Theoretical calculations reveal that such S‐induced pyridinic‐N improvement possibly originates from its catalytic effect that can facilitate the transition from edge quaternary‐N to pyridinic‐N. The resultant high content of pyridinic‐N, together with the additional S species, ensures abundant active sites for K+ storage. Accordingly, the N/S co‐doped carbon anode delivers both a high reversible capacity (422.9 mA h g−1 at 0.05 A g−1) and an impressive cyclic stability (249.6 mA h g−1 at 1 A g−1 over 4000 cycles). Moreover, in/ex situ characterizations further verify the merits of N/S co‐doped carbon from the perspective of compositional evolution and structural stability. This study unravels the origin of enhanced K+ storage by N/S co‐doping, which also helps to understand the synergistic effects of other heteroatoms co‐doping systems. [ABSTRACT FROM AUTHOR]