Electrochemical Lithium Storage Performance Of Expired Zinc Gluconate-derived ZnO/C And ZnFe₂O₄/C Anodes

With the continuous development of society,disproportionate production and consumption patterns will also cause a large number of foods and medicines to expire.Usually these expired foods and medicines will be landfilled or burned together with the domestic wastes,causing environmental pollution.Environmental problems such as biodiversity loss,water,air,and soil pollution,resource depletion,and excessive land use are increasingly jeopardising the earth’s life-support systems.The successful shift of the waste resources into the treasures by the circular economy mode was a very necessary strategy to deal with the environmental pollution and resource shortages.Therefore,in order to reduce the environmental pollution and the waste resources,it was very urgent to carry out the recycling investigation of expired foods and medicines.Based on this,two common nutrients expired zinc gluconate and ferrous gluconate were selected as the precursors.Zinc oxide/carbon microspheres and dumbbell-shaped zinc ferrite-carbon composite were obtained.The main research contents are as follows:（1）ZnO/C microspheres were recovered and extracted from expired food nutritionzinc zinc gluconate by hydrothermal reaction and the subsequent pyrolysis carbonization.Furthermore,the effect of hydrothermal time on the morphology,chemical composition content,crystal structure and electrochemical lithium storage peroformances of Zn O/C composite were investigated.The results showed that the combination mode and carbon content of Zn O with carbon microspheres were controlled by tailoring the hydrothermal reaction time.The carbon content within Zn O/C-5h composite was 53 wt%,slightly lower than 55 wt%of Zn O/C-9h composite.For example,the reversible discharge capacity of Zn O/C-5h anode remained 270m Ah?g^-1 even at 1000m A?g^-1for 500 cycles,higher than 183 m Ah?g^-1 of Zn O/C-9h anode.Suitable combination mode and the synergistic effect of two phases may contribute to higher electrochemical performances.These results would provide a cycling paradigm of waste expired zinc gluconate,thereby delaying the stream of fresh raw materials into the waste resources.（2）ZnFe₂O₄/C were recovered and extracted from expired zinc gluconate and expired food nutritionzinc ferrous gluconate by solvothermal in ethylene glycol and heat treatment.Further,the effect of the calcination time on the micromorphology,chemical composition,crystal structure and electrochemical lithium storage perfornamces of Zn Fe₂O₄/C anode were investigated.The results showed that three Zn Fe₂O₄/C composites manifested a uniform dumbbell-like morphology with about300-400 nm in diameter and 1-2μm in length.With the elongation of the calcination time from 1 h to 2 h and to 3 h,the carbon content within Zn Fe₂O₄/C composite decreased from 10.4%to 6.5%and to 3.6%,while the crystallinity gradually increased.The dumbbell-like Zn Fe₂O₄/C-2h composite anode exhibited the reversible specific capacity of 909 m Ah?g^-1 at 0.5 A?g^-1 for 50 cycles,higher than those of Zn Fe₂O₄/C-1h(779 m Ah?g^-1)and Zn Fe₂O₄/C-3h(860 m Ah?g^-1)possibly attributed to the optimal carbon content and crystallinity.These results will undoubtedly promote the development of circular economy of waste expired zinc gluconate and ferrous gluconate,and reduce the environmental emission.