[en] Utilizing hyper-lithiated materials can offer a variety of options for designing high-energy lithium-ion batteries. As sacrificial cathodes, they compensate for the initial loss of Li${}^{+}$ at the anode. During the first delithiation process, a Fe-substituted Li${}_6$CoO${}_4$ (Li${}_{5.7}$Co${}_{0.7}$Fe${}_{0.3}$O${}_4$) supplies a large amount of Li${}^{+}$. Especially, the peroxide species formation and oxygen evolution are suppressed even though the charge compensation of oxygen is facilitated in Li${}_{5.7}$Co${}_{0.7}$Fe${}_{0.3}$O${}_4$. From a structural viewpoint, the anti-fluorite structure changes to defective disordered phases during the Li${}^{+}$ extraction, and the proportion of the electrochemical-inactive phase is more dominant in the case of Li${}_{5.7}$Co${}_{0.7}$Fe${}_{0.3}$O${}_4$ at the end of the charge. Consequently, the delithiated Li${}_x$Co${}_{0.7}$Fe${}_{0.3}$O${}_4$ is deactivated in subsequent cycles, reducing unexpected electrochemical reactions after the Li${}^{+}$ provision as sacrificial cathodes. These findings provide a comprehensive understanding of the reaction mechanism of hyper-lithiated materials and represent a significant step forward in developing high-performance sacrificial cathodes. (© 2023 Wiley‐VCH GmbH)

[en] The graphite/silicon-based diffusion-dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all-solid-state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon-based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful-cell configuration. Herein, a new concept is presented for DDEs, dry pre-lithiated DDEs (PL-DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL-DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL-DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high-energy-density ASSBs. (© 2023 The Authors. Advanced Energy Materials published by Wiley‐VCH GmbH)

[en] Crack propagation has been extensively spotlighted as a main reason for the degradation of secondary-particle-type active materials, including LiNi${}_x$Mn${}_y$Co${}_{1-<!--\; ???\; -->x-<!--\; ???\; -->y}$O${}_2$ (NMC). Numerous experimental analyses and 3D-modeling-based investigations have been conducted to unravel this complicated phenomenon, especially for nickel-rich NMCs, which experience substantial crack propagation during high-voltage, high-temperature, or high-depth-of-discharge operations. To fundamentally clarify this unavoidable degradation factor and permit its suppression, a digital-twin-guided electro-chemo-mechanical (ECM) model of a single few-micrometer-sized LiNi${}_{0.7}$Mn${}_{0.15}$Co${}_{0.15}$O${}_2$ (NMC711) particle is developed in this study using a 3D reconstruction technique. Because the digital twin technique replicates a real pore-containing NMC711 secondary particle, this digital-twin electrochemical model simulates voltage profiles even at 8C-rate within an error of 0.48% by fitting two key parameters: diffusion coefficient and exchange current density. The digital-twin-based ECM model is developed based on the verified electrochemical parameters and mechanical properties such as lithium-induced strain from axis lattice parameters and stress-strain curve measured by nanoindentation. Using this model, the electrochemical-reaction-induced mechanical properties including strain, stress, and strain energy density are also visualized in operando in a single NMC711 particle. Finally, the advanced operando ECM analysis allows for the diagnosis of crack formation, highlighting the effectiveness of this platform in elucidating crack formation in active materials. (© 2023 Wiley‐VCH GmbH)