A prototype rechargeable sodium-ion battery using an O3-Na0.90[Cu0.22 Fe0.30 Mn0.48]O2 cathode and a hard carbon anode is demonstrated to show an energy density of 210 W h kg(-1) , a round-trip energy efficiency of 90%, a high rate capability (up to 6C rate), and excellent cycling stability.

An air‐stable copper‐based P2‐Na7/9Cu2/9Fe1/9Mn2/3O2 is designed and synthesized by a simple solid‐state method and investigated as a positive electrode material for sodium‐ion batteries. The attractive long cycling stability is demonstrated by the capacity retention of 85% after 150 cycles at 1 C rate without phase transformation. The reversible Cu2+/Cu3+ redox couple in P2 phase oxides is proved for the first time.

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. We observe that the mechanical breakdown of charged LiNiMnCoO materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformations from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles, i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to the formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.

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The microstructure of a composite electrode determines how individual battery particles are charged and discharged in a lithium-ion battery. It is a frontier challenge to experimentally visualize and, subsequently, to understand the electrochemical consequences of battery particles' evolving (de)attachment with the conductive matrix. Herein, we tackle this issue with a unique combination of multiscale experimental approaches, machine-learning-assisted statistical analysis, and experiment-informed mathematical modeling. Our results suggest that the degree of particle detachment is positively correlated with the charging rate and that smaller particles exhibit a higher degree of uncertainty in their detachment from the carbon/ binder matrix. We further explore the feasibility and limitation of utilizing the reconstructed electron density as a proxy for the state-of-charge. Our findings highlight the importance of precisely quantifying the evolving nature of the battery electrode's microstructure with statistical confidence, which is a key to maximize the utility of active particles towards higher battery capacity.

rechargeable batteries. Efforts have been devoted to studying different battery components (e.g., cathode, anode, electrolyte, and binder), aiming to improve energy and power densities, enhance safety, prolong lifetime, and reduce cost. An important aspect of the battery research is to identify the fading pathways of battery particles and electrodes at multiple length/time scales under practical operating conditions. [1] Redox reactions in batteries commonly involve phase transformation, lattice volume change, stress buildup, grain boundary weakening, and particle fracturing. These processes intertwine at multiple length and time scales, are termed as the chemomechanical interplay, and contribute to the complex fading mechanisms of composite battery electrodes. Mapping the chemomechanical transformation of battery particles and particle ensembles represents a promising methodology to establish the relationship among all these processes. Such a study will potentially provide insights into designing materials and electrodes whereThe multiscale chemomechanical interplay in lithium-ion batteries builds up mechanical stress, provokes morphological breakdown, and leads to state of charge heterogeneity. Quantifying the interplay in complex composite electrodes with multiscale resolution constitutes a frontier challenge in precisely diagnosing the fading mechanism of batteries. In this study, hard X-ray phase contrast tomography, capable of nanoprobing thousands of active particles at once, enables an unprecedented statistical analysis of the chemomechanical transformation of composite electrodes under fast charging conditions. The damage heterogeneity is demonstrated to prevail at all length scales, which stems from the unbalanced electron conduction and ionic diffusion, and collectively leads to the nonuniform utilization of active particles spatially and temporally. This study highlights that the statistical mapping of the chemomechanical transformation offers a diagnostic method for the particles utilization and fading, hence could improve electrode formulation for fast-charging batteries.

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The practical implementation of Co-free, LiNiO 2 -derived cathodes has been prohibited by their poor cycle life and thermal stability, resulting from the structural instability, phase transformations, reactive surfaces, and chemomechanical breakdown. With the hierarchical distribution of Mg/Ti dual dopants in LiNiO 2 , we report a Co-free layered oxide that exhibits enhanced bulk and surface stability. Ti shows a gradient distribution and is enriched at the surface, whereas Mg distributes homogeneously throughout the primary particles. The resulting Mg/Ti codoped LiNiO 2 delivers a material-level specific energy of ∼780 W h/kg at C/10 with 96% retention after 50 cycles. The specific energy reaches ∼680 W h/kg at 1C with 77% retention after 300 cycles. Furthermore, the Mg/Ti dual dopants improve the rate capability, thermal stability, and self-discharge resistance of LiNiO 2 . Our synchrotron X-ray, electron, and electrochemical diagnostics reveal that the Mg/Ti dual dopants mitigate phase transformations, reduce nickel dissolution, and stabilize the cathode−electrolyte interface, thus leading to the favorable battery performance in lithium metal and graphite cells. The present study suggests that engineering the dopant distribution in cathodes may provide an effective path toward lower cost, safer, and higher energy density Co-free lithium batteries.