Study On The Performance Of LiMn₂O₄Using Spent Zn-Mn Batteries As Manganese Source

In recent years, Zinc-manganese battery has been widely used in variouselectronic products such as radios, watches, calculators, controls and many otherobjects where small quantities of power are required as the power sources of electricappliances. After their lifespan, the same amount of spent Zn-Mn batteries is usuallydiscarded to the nature. The vast amount of untapped mineral resources in wastebatteries such as manganese, zinc, iron and other heavy metals like mercury, cadmium,lead that were abandoned to the nature would wastes the resources, even worse, theyare detrimental to the environment. There are many deficiencies in the recycling ofzinc-manganese batteries such as high recovery processing requirements, lowvaue-added products and high cost. Spinel LiMn2O4has been extensively investigatedas one of the most promising cathode materials to replace LiCoO2because of its lowcost, non-toxicity, environmental friendliness and large capacity. Apart from that,spinel LiMn2O4as a cathode material for high power lithium batteries has the uniquethree-dimensional lithium ion diffusion channels which may potentially contribute tothe intercalation and prolapse of lithium ion. However, capacity fade, especially atelevated temperatures and large current, restricts its commercial application. Therecycling of zinc-manganese batteries was linked with the synthesis of spinel LiMn2O4in this paper. Specifically, spent Zn-Mn batteries was recovered by hydrometallurgyrecycling technology, and used as manganese source for lithium-ion battery cathodematerial. In this paper, optimizing the recovery process of MnO2, optimizing thesynthetic method of LiMn2O4, doping with Co, doping with F and doping with F-Cowere used to improve the electrochemical performance.The structural andmorphological properties of the sample were characterized by X-ray powderdiffraction (XRD) and Scanning electron microscopy (SEM). The electrochemicalproperties of the sample were also investigated with charge and discharge test.The manganese, iron and ammonium chloride were recovered by hydrometallurgyrecycling technology. The influences of calcining temperature, calcining time, acid concentration and acid marinating time on the purity of MnO2were studied. The resultshowed that the optimal condition of calcining temperature was850℃, the calciningtime was5h, the acid concentration was1:1and the best acid marinating time was24h.Spinel LiMn2O4was prepared by solid-state method and sol-gel method usingthe manganese source that recovered form spent Zn-Mn batteries by hydrometallurgyrecycling technology. The results showed that the LiMn2O4prepared by sol-gel methodoffers several advantages such as good uniformity, high purity, narrow particle-sizedistribution and the initial discharge capacity was80.7mAh·g-1, the capacity loss is3.1%after50cycles.Spinel LiMn2O4was prepared by sol-gel method. The influences of naturalchelating agent, calcining temperature and lithium source on the performance ofLiMn2O4were studied. The result showed that the optimal condition of chelating agentwas malic acid, the calcining temperature was700℃and the lithium source wasLiNO3. The initial discharge capacity was118.9mAh·g-1, the capacity loss is20.8%after50cycles under this condition.Co-doping material, F-doping material and F-Co-doping spinels were synthesizedby sol-gel method. The structural and morphological properties of the sample werecharacterized by X-ray powder diffraction (XRD) and Scanning electron microscopy(SEM). The electrochemical properties of the sample were also investigated withcharge and discharge test. The results show that the single Co-substitution deterioratedthe initial discharge/discharge capacities but improved the cyclability. The initialdischarge capacity of LiCo0.1Mn1.9O4is104.5mAh·g-1, the capacity loss is5.1%after50cycles. On the contrary, the single F-substitution deteriorated the cyclability butimproved the initial discharge/discharge capacities. The initial discharge capacity ofLiMn2O3.9F0.1is124.5mAh·g-1, the capacity loss is23.9%after50cycles. The F-Cocompound substitution overcame the defects of single anion substitution and cationsubstitution.The initial discharge capacity of LiCo0.1Mn1.9O3.9F0.1is120.7mAh·g-1, the capacity loss is8.4%after50cycles.