Recycling-oriented cathode materials design for lithium-ion batteries: Elegant structures versus complicated compositions

Intense and large-scale applications of lithium-ion batteries have brought significant convenience to our daily life; however, when these batteries enter recycling, they cause major challenges such as environmental pollution and wastage of resources. For the sustainable point of view, it is preferable to establish a full-cycle value chain from designing and manufacturing of electrodes to recycling of spent lithium-ion batteries. It is important to perform materials and product design as the first and most important step in the cycling process, particularly for the cathode materials. This critical review focuses on the issues in element recycling of the spent cathode materials, and discusses the criteria for cathode materials design that can simplify the recycling process and avoid a build-up of hazardous materials. Using Li transition metal oxides (LiCoO2, LiNi(1-x-y)Co(x)MnyO(2), x + y < 1) as an example, it is shown that the crystal structure, morphology, and microstructure also play vital roles in enhancing the electrochemical performance of the cathode materials. Compared to complicated composition in the cathode materials, the structure-regulated design has a unique potential to build a circular economy model featuring the lowest energy consumption and the least environmental disruption. It not only highlights the green and sustainable aspects of the recovery of metal resources, but also prospects them with recycling-oriented materials design. The circular economy can be built with both high efficiency and stable battery performance.