Study On LiNi_0.5Mn_1.5O₄and LiNi_1/3Co_1/3Mn_1/3O₂as Cathode Materials Of Primary Lithium Batteries

Primary lithium batteries are widely used because of long shelf lives, low self-dischargeand light weight, especially in the military field. However, the energy density and powerdensity of primary lithium batteries need to be further improved, which depends on researcheson new positive electrode materials. In this paper, new positive materials of primary lithiumbatteries with high energy density was prepared by delithiation of the positive electrodematerials of secondary Li-ion battery.The effects of delithiation condition of LiNi_0.5Mn_1.5O₄and LiNi_1/3Co_1/3Mn_1/3O₂on therestructure and discharge performance were investigated. The delithiation was carried out usinga chemical method, and the delithiation conditions, such as different acid systems,delithiation temperatures and delithiation time were investigated. The structure andmorphology of the delithiated materials were characterized by XRD and SEM, and thereelectrochemical properties were tested in primary lithium batteries by EIS and constantcurrent discharge tests.LiNi_0.5Mn_1.5O₄was delithiatied in1.0mo·L-1HCl+0.1mol·L-1NaClO,1.0mol·L-1H2SO4and1.0mol·L-1HNO3three acid systems, at different temperatures of60℃,80℃and100℃and different time of12h,24h and48h. XRD and SEM results show thatsLiNi_0.5Mn_1.5O₄delithiatied in1.0mol·L-1HCl+0.1mol·L-1NaClO solution at80℃for24h, has uniform and small partical size, the diameter of particle is1⁵μm. Constantcurrent discharge tests shows that this material has the highest specific capacity and powerdensity among all the samples. At0.1C discharge rate, the specific capacity is380mAh·g-1,the power density is1043Wh·kg-1and the discharge platform voltage is2.77V. EIS showsthat the electrochemical impedance of the battery is122.LiNi_1/3Co_1/3Mn_1/3O₂was delithiatied in the above-mentioned three acid systems, threetreatment temperatures and three times. XRD analysis show that LiNi_1/3Co_1/3Mn_1/3O₂delithiatied in1.0mol·L-1HCl+0.1mol·L-1NaClO solution at80℃for24h have asignificant structure changes. It was found that not only Li+was take off, some of Ni2+andCo3+were also removed, and a trace amount of MnO2was formed. SEM results show thatdelithiation sample presents a uniform spherical particles with a diameter is2³μm. Constant current discharge tests shows that LiNi_1/3Co_1/3Mn_1/3O₂delithiatied under this condition has thehighest working voltage, and at0.1C discharge rate, the specific capacity is199mAh·g-1,the power density is568Wh·kg-1and the discharge platform voltage is2.91V. EIS shows thatthe electrochemical impedance of the battery is only47.