Holey graphene-based nanocomposites for efficient electrochemical energy storage

Graphene, versatile building blocks for functional composite materials, shows multiple fascinating properties and draws great interest, especially in the field of electrochemical energy storage. However, several common drawbacks still persist, including (i) it tends to aggregate and restack to loss the surface area, (ii) it is difficult to composite with other materials due to the limited processibility (e.g, limited functional groups or defect sites), (iii) it lacks efficient molecules/ions transport channels. Thus, it presents a great challenge to prepare graphenebased nanocomposites for various applications, including energy storage. However, the recent availability of holey graphene (HG) has led to numerous HG-based functional composites of practicle significance. This review presents a comprehensive overview of the synthesis of HG and its nanocomposites, and their applications for electrochemical energy storage, including supercapacitors, lithium ion/sulfur/O-2/CO2 batteries, sodium ion batteries, potassium ion batteries, Zn-air batteries, fuel cells and solar cells. The structure-property relationships of various HG-based nanocomposites will be thoroughly discussed, along with the pros and cons. The current challenges and future perspectives of HG-based nanocomposites are also outlined. This review should promote the fundamental understanding and further development of HG-based nanocomposites for electrochemical energy storage and even beyond.