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Electrode microstructure is one of the primary factors determining the electrochemical properties of all‐solid‐state batteries (ASSBs). However, the key principles of electrode design to realize fast ionic/electronic transport pathways are not well elucidated. Herein, the correlation between electrode microstructure and electrochemical behaviors is studied through different electrode design in terms of energy‐density‐related electrode composition and Ni‐rich layered oxides particle size distribution. A positive relation between particle size and mass fraction in electrode design is revealed, that is, as the particle size increases, more cathode materials are required to enable the fast reaction kinetics. The well interconnected active particles and solid electrolytes construct the highly percolated ionic/electronic transfer networks, which determines the overall electrochemical properties. The findings in this work give a new insight into electrode design to promote the development of high‐energy and high‐power ASSBs. [ABSTRACT FROM AUTHOR]

• A scalable microstructure engineering strategy for developing mechanically reinforced Ni-rich cathodes. • A well-designed polycrystalline Ni-rich cathode consisting of densely packed large-size primary particles. • Superior rate performance (31.7 mAh g−1 at 4C) and cyclic stability (84.1% after 100 cycles at 0.2C). Mechanical integrity is crucial for the intra-particle ionic/electronic transfer in all-solid-state batteries. However, electrode particles suffer severe electrochemo-mechanical degradations during electrode compaction and high-voltage operation, which is extremely true in the popular high-energy cathodes of fragile polycrystalline Ni-rich oxides composed of loosely stacked nanoparticles. Herein, we develop mechanically reinforced polycrystalline Ni-rich cathodes consisting of densely packed large-size primary particles based on a scalable microstructure engineering strategy. The structural characterization and finite element simulation results demonstrate that this well-designed microstructure of cathodes can suppress the stress/strain accumulation and formation of cracks, and thus maintain the original microstructure and highly percolated ionic/electronic networks. All-solid-state batteries based on mechanically reinforced Ni-rich cathodes achieve significantly improved specific capacity, rate capability, and cyclic stability. This work provides a new sight for designing advanced cathodes to boost the development of high-power and long-life all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Traditional heterogeneous polycrystalline layered oxides suffer from serious chemo-mechanical degradations, which is extremely true in nickel-rich cathodes under high-voltage operation. Although single-crystalline structure is proved to be able to withstand anisotropic lattice strain and prevent cracks formation, the long cycle stability at high-voltage in all-solid-state batteries (ASSBs) with nickel-rich layered oxides as the cathode are still far from commercial applications. Herein, we synthesize a micro-sized single-crystalline nickel-rich oxides LiNi 0.83 Co 0.11 Mn 0.06 O 2 (SC–N83) to eliminate the chemo-mechanical failures. The well-dispersed SC-N83 in the ASSBs delivers an excellent cyclic stability under high-voltage (4.4 V vs Li/Li+) operation, which shows a capacity retention of 85.1% after 500 cycles at 0.5C. Even at high active areal loading of 22.6 cm−2 (corresponding to an initial areal capacity of 4.19 mAh cm−2) and high temperature of 50 °C, the SC-N83 cathodes can still maintain 75.5% discharge capacity after 200 cycles at 0.5C. The high cycling stability is further proved to be attributed to dramatically suppressed mechanical failure caused by the build-up of strain and stress. This proposed strategy with highly dispersed single-crystalline nickel-rich oxides paves the way to develop advanced high-capacity and high-voltage operating ASSBs. [Display omitted] • Single-crystalline Ni-rich oxides against chemo-mechanical failure at high voltage. • Long life cathodes (85.1% after 500 cycles at 0.5C) at high voltage operation. • A practical cathode with the areal capacity of 4.19 mAh cm−2 is fabricated. • Excellent fast charge capability (142.9 mAh g−1 at 5 C and 50 °C). [ABSTRACT FROM AUTHOR]