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.

Facile synthesis of porous and hollow spinel materials is highly desirable for their extensive applications in energy storage fields. In this work, uniform and decentralized flower-like CoMn₂O₄ microspheres were synthesized and characterized for supercapacitor electrodes in neutral aqueous electrolyte. In this contribution, uniform microsphere precursors were firstly fabricated by a solvothermal method, followed by a low temperature calcination process for crystallization. A detailed study shows that the deionized (DI) water content plays an important role in the solvothermal process to optimize the morphology of the microspheres. In 1 M Na₂SO₄, the spinel electrode material has a working potential window as high as 1.1 V and a specific capacitance of 188 F g⁻¹. Besides, the electrode material exhibits excellent cycling stability by retaining 93% of its original capacitance after 1000 cycles. Therefore, the flower-like microspheres of CoMn₂O₄ spinel are promising candidates for supercapacitor applications.