Doping Modification Of Lithium Manganate For Thermal Batteries Cathode

Low temperature thermal batteries can be activated and operated by heat in geothermal environment,which can greatly simplify the complex battery structure based on traditional military thermal batteries,improve specific capacity and reduce the cost of battery production and manufacturing.The cathode material is one of the key materials to improve the voltage,specific capacity and specific power of thermal batteries.Among cathode materials,spinel lithium manganate attracts much attention because of its positive electrode potential,high theoretical capacity and environmental friendliness.However,the structural stability of lithium manganate in the discharge process needs to be improved.Therefore,spinel lithium manganate is doped to improve its stability and electrochemical performance in thermal batteries.We test the compatibility of electrode materials,and test the discharge of single batteries under specific temperature and current,so as to promote the application of thermal batteries in the development of geothermal resources and the exploitation of underground resources such as Petroleum-Natural gas.The main research contents and results are as follows:1.The LiCr_xMn_2-xO₄?0?x?0.5?materials were successfully synthesized by a simple solid-state method and applied to Li-Mg-B/LiNO₃-KNO₃-Ca?NO₃?₂/LiCr_xMn_2-xO₄ thermal battery system.The DSC results show that LiCr_xMn_2-xO₄ and nitrate have good compatibility in the temperature range from room temperature to 400°C.The chromium doping content,temperature and current density have great influence on the discharge performance of Li-Mg-B/LiNO₃-KNO₃-Ca?NO₃?₂/LiCr_xMn_2-xO₄ battery.The LiCr_0.1Mn_1.9O₄ cathode material reaches the highest specific capacity of 998 mAh?g^-1 at 10 mA·cm^-2 at 200°C.Chromium doped spinel lithium manganese oxide has a more stable structure,so that lithium manganese spinel oxides have better electrochemical properties.2.Cr³⁺and F^-ions were successfully doped into spinel lithium manganate oxides by high-temperature solid-state method and verified by XRD and XPS.Fluoride-doped spinel has a significant improvement in battery performance at a current density of 10 mA·cm^-2 under the temperature of 250°C.Particularly,LiCr_0.1Mn_1.9O_3.6F_0.4 sample has a discharge capacity of820.78 mAh·g^-1 at the condition,which is higher than that of F-free sample 35.6%,this is due to the enhancement of the stability of spinel by fluoride ions.In addition,we find that both the temperature and the current density have a significant effect on the performance of the LiCr_0.1Mn_1.9O_4-x-x F_x/LiNO₃-KNO₃-Ca?NO₃?₂/Li-Mg-B battery.The suitable operating temperature of this battery system is 200 to 250°C,and the current density is around 10 mA·cm^-2.The discharge mechanism of spinel lithium manganate oxides in nitrate electrolyte system is discussed and verified by XRD.3.Cr and Ni doped spinel LiCr_xNi_yMn_2-x-yO₄?0?x?0.3,0?y?0.3?cathode materials have been successfully synthesized through solid-state method and maintained the Fd3m spatial structure of the spinel which has been confirmed by XRD results.Partial substitution of Cr³⁺and Ni²⁺for Mn in spinel improves battery voltage and capacity at current densities from 10 to30 mA?cm^-2 over a temperature range of 200 to 300°C.The LiCr_xNi_yMn_2-x-yO₄/Li-Mg-B battery system has the most outstanding discharge performance at a constant current density of 10mA?cm^-2 at 300°C,and the LiCr_0.1Ni_0.3Mn_1.6O₄ has the maximal specific capacity of 713.29mAh·g^-1.The dramatic improvement in discharge performance of the battery system is mainly due to the doping of chromium and nickel enhanced the structural stability of spinel lithium manganate oxides.Based on the stable structure of the material,the battery has a more significant improvement in discharge performance at higher current densities.