New Spinel Structure Of Lithium-ion Battery Materials Research And Application

As the cathode material of lithium ion batteries, cubic spinel LiNi_0.5Mn_1.5O₄ shows excellent electrochemical performance, such as high discharge plateau at 4.7V and high energy density, and it is emerging as an active research topic. In this paper, the spinel LiNi_0.5Mn_1.5O₄ with high energy density and excellent cycle performance were synthesized by coprecipitation composite carbonate process methods. The effects of synthesizing conditions on the physical properties and electrochemical performances of LiNi_0.5Mn_1.5O₄ were investigated. Spinel Li₄Ti₅O₁₂, an attractive negative electrode regarded as a "zero strain" material with better safety and excellent structure stability, has been studied extensively . Its theoretical specific capacity is 175mAh·g^-1. The sample also exhibit excellent cycle performance and plateau voltage.In this paper, the spinel Li₄Ti₅O₁₂ was synthesized by Sol-Gel method. The effects of synthesizing conditions on the physical properties and electrochemical performances of Li₄Ti₅O₁₂ were investigated.The LiNi_0.5Mn_1.5O₄ spinel has been prepared by a composite carbonate process, and the effects of calcination temperature on the physical properties and electrochemical performance of the samples have been investigated. The results of XRD and scanning electron microscopy (SEM) showed that as calcination temperature increases , the grain sizes of the samples is obviously increase. It was found that the samples calcined at 800℃present good electrochemical performance. Between 3.5-4.9V versus Li, it delivered 130.24mAh·g^-1, 129.47mAh·g^-1, 115.5 mAh·g^-1, 108.05mAh·g^-1 at 0.1C, 1C, 2C, 4C rates respectively. And it showed good cycle performance under high current density .The effect of doping elements and doping amount into LiMxNi_0.5-xMn_1.5O₄(x: Mg, Fe, Al) on its electrochemical properites was studied. The SEM analysis indicates that the particles Surface Morphology have great affected by the doping elements. Further more, XRD characterization of the products revealed that the when the doping element reaching certain content the crystal structure of the compound was changed. Electrochemical measurements showed that the doping Of Mg and Al can not improve the electrochemical. But Al doping can improve the electrochemical. In addition, high-rate test indicated that the LiAl_0.05Ni_0.45Mn_1.5O₄ powers has excellent electrochemical performance when charged and discharge at 1C and 10C, respectively.A novel technique was developed to prepare Li₄Ti₅O₁₂ anode material for lithium secondary batteries in this paper. The precursor was prepared by sol-gel method using terbutyl titanate, lithium acetate and isopropanol as starting materials. Then the precursor was calcined for 24 hours in air to obtain Li₄Ti₅O₁₂. The influence of temperature on performance of product was studied. The investigation of XRD, SEM and the determination of the eldctromical properties show that the Li₄Ti₅O₁₂ powers prepared by this method are narrowly distributed, well crystallized. The Li₄Ti₅O₁₂ powers also have excellent electrochemical performance.Between 1.0-2.5V versus Li, it delivered 158.5mAh·g^-1, 137.8mAh·g^-1 and 124.3mAh·g^-1 at 0.1C, 1.0Cand 2.0C respectively. And it showed good cycle performance under high current density. Study shows that this method is appropriate for preparing Li₄Ti₅O₁₂ with high electrochemical performance. The LiAl_0.05Ni_0.45Mn_1.5O₄/Li₄Ti₅O₁₂ full cell system was investigated also. The LiAl_0.05Ni_0.45Mn_1.5O₄/Li₄Ti₅O₁₂ cell system charge and discharge between 2.0V to 3.5V. And it show a voltage plateau at 3.1V.