Lithium-ion batteries have dominated the high performance and mobile market for last decade. Despite their dominance in many areas, the development of current commercial lithium-ion batteries is experiencing bottlenecks, limited by safety risks such as: leakage, burning, and even explosions due to the low-boiling point organic liquid electrolytes. Solid electrolyte is a promising option to solve or mitigate those issues. Among all solid electrolytes, polymer based solid electrolytes have the advantages of low flammability, good flexibility, excellent thermal stability, and high safety. Numerous researchers have focused on implementing solid polymer based Li-ion batteries with high performance. Nevertheless, low Li-ion conductivity and poor mechanical properties are still the main challenges in its commercial development. In order to tackle the issues and improve the overall performance, composites with external particles are widely investigated to form a polymer-based composite electrolyte. In light of their work, this review discusses the progress of polymer-based composite lithium ion's solid electrolytes. In particular, the structures, ionic conductivities, electrochemical/chemical stabilities, and fabrications of solid polymer electrolytes are introduced in the text and summarized at the end. On the basis of previous work, the perspectives of solid polymer electrolytes are provided especially toward the future of lithium ion batteries.

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cathode of LIBs. Recently, Li-rich cathode materials (LMNCO), x Li 2 MnO 3 ·(1 − x) LiTMO 2 (0 < x < 1, TM = Mn, Ni, Co, etc.), have received extensive attentions due to their promising reversible capacity (>250 mAh g −1 ), environmental benignity, and low cost. [3] Nevertheless, the sluggish diffusion of electrons and lithium ions within LMNCO results in electrode polarization and inferior rate capability. [4] It has been verified that the electrochemical performance of LMNCO is closely connected with the morphology and structure, thereby rational design and control of the formation process for LMNCO is considered to be an effective route to enhance the capacity retention and rate capability. [5][6][7][8][9] On the basis of this, extensive efforts have been devoted to develop nanometersized materials and great progresses have been achieved over the past several years, such as construction of nanoplates, [5] nanowires, [10] nanoparticles, [11] and nanorods, [12] which possess a short Li + diffusion pathway thanks to their diminished dimensions. However, severely undesired side reactions between nanoscale electrode/electrolyte are detrimental to structural stability. [13] In order to address these challenges of nanometer-sized materials, hierarchical micro/nano-materials have been developed recently. [14][15][16] Hierarchical LMNCO possessed stable framework of micro-materials can achieve the prolonged cycle life through reducing interfacial reaction with electrolytes. [16] However, individual hierarchical structure strategy may be not enough, as the rate capability and cycling stability of the hierarchical LMNCO still need to be further improved. [17,18] Recent reports have evidenced two-dimensional (2D) nanostructure owns the advantages of open electrons and ions transport path, high active surface area, and excellent structure stability by accommodating the drastic volume evolution, which makes it applicable for ultrahigh-rate and cycling-stable lithium storage. [19][20][21] In addition, 2D nanosheets often have large exposed surface areas and specific facets. [22,23] It has been reported that in LMNCO cathodes, if the surfaces are parallel to {010} facets (e.g., (010), (100), and (110) planes), perpendicular to (001) plane, the Li + diffusion kinetics will be substantially strengthened. [15,16,24,25] Consequently, the synergistic effect of the 2D nanosheets, hierarchical structure, and Li-rich oxide is a promising candidate for the cathodes of next-generation lithium-ion batteries. However, its utilization is restricted by cycling instability and inferior rate capability. To tackle these issues, three-dimensional (3D), hierarchical, cube-maze-like Li-rich cathodes assembled from two-dimensional (2D), thin nanosheets with exposed {010} active planes, are developed by a facile hydrothermal approach. Benefiting from their unique architecture, 3D cube-maze-like cathodes demonstrate a superior reversible capacity (285.3 mAh g −1 at 0.1 C, 133.4 mAh g −1 at 20.0 C) and a great cycle stability (capacity retention of ...

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