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Compared with commercial lithium batteries with liquid electrolytes, all-solidstate lithium batteries (ASSLBs) possess the advantages of higher safety, better electrochemical stability, higher energy density, and longer cycle life; therefore, ASSLBs have been identified as promising candidates for next-generation safe and stable high-energy-storage devices. The design and fabrication of solid-state electrolytes (SSEs) are vital for the future commercialization of ASSLBs. Among various SSEs, solid polymer composite electrolytes (SPCEs) consisting of inorganic nanofillers and polymer matrix have shown great application prospects in the practice of ASSLBs. The incorporation of inorganic nanofillers into the polymer matrix has been considered as a crucial method to achieve high ionic conductivity for SPCE. In this review, the mechanisms of Li + transport variation caused by incorporating inorganic nanofillers into the polymer matrix are discussed in detail. On the basis of the recent progress, the respective contributions of polymer chains, passive ceramic nanofillers, and active ceramic nanofillers in affecting the Li + transport process of SPCE are reviewed systematically. The inherent relationship between the morphological characteristics of inorganic nanofillers and the ionic conductivity of the resultant SPCE is discussed. Finally, the challenges and future perspectives for developing high-performance SPCE are put forward. This review aims to provide possible strategies for the further improvement of ionic conductivity in inorganic nanoscale filler-reinforced SPCE and highlight their inspiration for future research directions. K E Y W O R D Sall-solid-state lithium batteries, inorganic nanofillers, Li + transportation, solid polymer composite electrolyteThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A facile two step process was developed for the synthesis of porous Co3O4 nanorods-reduced graphene oxide (PCNG) hybrid materials based on the hydrothermal treatment cobalt acetate tetrahydrate and graphene oxide in a glycerol-water mixed solvent, followed by annealing the intermediate of reduced graphene oxide-supported Co(CO3)0.5(OH)·0.11H2O nanorods in a N2 atmosphere. The morphology and microstructure of the composites were examined by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. It is shown that the obtained PCNG have intrinsic peroxidase-like activity. The PCNG are utilized for the catalytic degradation of methylene blue. The good catalytic performance of the composites could be attributed to the synergy between the functions of porous Co3O4 nanorods and reduced graphene oxide.

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Rechargeable lithium metal anodes (LMAs) with long cycling life have been regarded as the "Holy Grail" for high-energy-density lithium metal secondary batteries. The skeleton plays an important role in determining the performance of LMAs. Commercially available copper foam (CF) is not normally regarded as a suitable skeleton for stable lithium storage owing to its relatively inappropriate large pore size and relatively low specific surface area. Herein, for the first time, we revisit CF and address these issues by rationally designing a highly porous copper (HPC) architecture grown on CF substrates (HPC/CF) as a three-dimensional (3D) hierarchically bicontinuous porous skeleton through a novel approach combining the self-assembly of polystyrene microspheres, electrodeposition of copper, and a thermal annealing treatment. Compared to the CF skeleton, the HPC/CF skeleton exhibits a significantly improved Li plating/stripping behavior with high Coulombic efficiency (CE) and superior Li dendrite growth suppression. The 3D HPC/CF-based LMAs can run for 620 h without short-circuiting in a symmetric Li/Li@Cu cell at 0.5 mA cm, and the Li@Cu/LiFePO full cell exhibits a high reversible capacity of 115 mAh g with a high CE of 99.7% at 2 C for 500 cycles. These results demonstrate the effectiveness of the design strategy of 3D hierarchically bicontinuous porous skeletons for developing stable and safe LMAs.

Lithium metal anodes (LMAs) are critical for high-energy-density batteries such as Li–S and Li–O2 batteries. The spontaneously formed solid electrolyte interface on LMAs is fragile, which may not accommodate the cyclic Li plating/stripping. This usually will result in a low coulombic efficiency (CE), short cycle life, and potential safety hazards induced by the uncontrollable growth of lithium dendrites. In this study, we fabricate a Li alginate-based artificial SEI (ASEI) layer that is chemically stable and allows easy Li ion transport on the surface of LMAs, thus enabling the stable operation of lithium metal anodes. Compared to bare LMAs, the ASEI layer-protected LMAs exhibit a more stable Li plating/stripping behavior and present effective dendrite suppression. The symmetric Li∥Li cells with the ASEI layer-protected LMAs can stably run for 850 and 350 h at current densities of 0.5 and 1 mA cm–2, respectively. Additionally, the LiFePO4∥Li full cell with the ASEI layer-protected LMA exhibits a capacity retention of about 94.0% coupled with a CE of 99.6% after 1000 cycles at 4 C. We believe that this study of engineering an ASEI brings a new and promising approach to the stabilization of LMAs for high-performance lithium metal batteries.

Mn-based layered oxides are very attractive as cathodes for potassium-ion batteries (PIBs) due to their low-cost and environmentally friendly precursors. Their transfer to practical application, however, is inhibited by some issues including consecutive phase transitions, sluggish K+ deintercalation/intercalation, and serious capacity loss. Herein, Mg–Ni co-substituted K1/2Mn5/6Mg1/12Ni1/12O2 is designed as a promising cathode material for PIBs, with suppressed phase transitions that occurred in K1/2MnO2 and improved K+ storage performance. Part of Mg2+ and Ni2+ occupies the K+ layer, playing the role of a “nailed pillar”, which restrains metal oxide layer gliding during the K+ (de)­intercalation. The “Mg–Ni pinning effect” not only suppresses the phase transitions but also reduces the cell volume variation, leading to the improved cycle performance. Moreover, K1/2Mn5/6Mg1/12Ni1/12O2 has low activation barrier energy for K+ diffusion and high electron conductivity as demonstrated by first-principles calculations, resulting in better rate capability. In addition, K1/2Mn5/6Mg1/12Ni1/12O2 also delivers a higher reversible capacity owing to the participation of the Ni element in electrochemical reactions and the pseudocapacitive contribution. This study provides a basic understanding of structural evolution in layered Mn-based oxides and broadens the strategic design of cathode materials for PIBs.