battery 18650 rechargeable

　　Research and progress analysis of battery 18650 rechargeablemanganese battery materials

　　Lithium-ion batteries are the second generation of rechargeable green batteries after nickel-cadmium batteries and metal hydride nickel batteries. They are widely used in modern electronic equipment such as notebook computers, mobile phones, laser pointers, and handheld cameras. Since the capacity of the positive electrode material of this battery is lower than that of the negative electrode material, further improvement in the capacity of lithium-ion batteries is limited. battery 18650 rechargeablecobalt, battery 18650 rechargeablenickel and battery 18650 rechargeablemanganese oxide materials are the three main cathode materials for lithium-ion batteries. Among them, battery 18650 rechargeablemanganese oxide materials have a wide range of applications due to their low preparation cost, no environmental pollution, and high effective utilization rate of electrochemical specific capacity. Development and application prospects, battery 18650 rechargeablemanganese batteries have become the focus of widespread attention. In recent years, some achievements have been made in the development and research of battery 18650 rechargeablemanganese oxide cathode materials at home and abroad. This article is a brief review of these achievements.

　　1Structure and properties of battery 18650 rechargeablemanganese oxide materials

　　The main materials that can be used as cathode materials include spinel structure LiMn2O4, Li2Mn4O9 and Li4Mn5O12, and layered structure LiMnO2. Some structural characteristics and theoretical capacity of spinel structure battery 18650 rechargeablemanganese oxide are shown in Table 1.

　　Table 1 Structural characteristics and capacities of some spinel-type battery 18650 rechargeablemanganese oxide compounds (where □ is an empty lattice point)

　　In the spinel structure of battery 18650 rechargeablemanganese oxide, battery 18650 rechargeableions are located at position 8a and oxygen atoms are located at position 32e. During the charging and discharging process, there are generally two platforms, about 4V and 3V. During the charge and discharge process, due to the large change in the valence state of manganese, from +3 valence to +4 valence, there is a strong Jahn2Teller effect, causing the crystal to change from cubic spinel type to tetragonal spinel type. During this phase change process, the volume of the unit cell unit increased by 6.5%, causing the spinel structure to deform, causing damage and attenuating the capacity.

　　Among spinel-structured battery 18650 rechargeablemanganese oxides, LiMn2O4 is currently the most studied and has the best performance as an electrode material. In LiMn2O4, the Mn2O4 skeleton is a three-dimensional structure in which tetrahedrons and octahedrons are coplanarly connected, which is beneficial to Li+ diffusion, as shown in Figure 2.

　　Figure 2 LiMn2O4 crystal structure with spinel structure

　　Oxygen atoms are cubically closely packed, 75% of the Mn atoms are alternately located between the cubically tightly packed oxygen layers, and the remaining 25% are located in adjacent layers of Mn atoms. Therefore, in the delithiated state, there are enough Mn cations present in each layer to maintain the ideal cubic close-packed state of oxygen atoms. In LixMn2O4 formed during the process of charging and inserting battery 18650 rechargeableions, when 0

　　In addition to the above spinel-type battery 18650 rechargeablemanganese compounds, layered LiMnO2 compounds are now also found. One of them has a different structure from layered LiCoO2 and belongs to the orthorhombic crystal system. It charges and discharges at 2.5~4.3V and has reversible capacity. It is about 200mAh/g. After the first charge and discharge, the orthorhombic LiMnO2 transforms into spinel LixMn2O4. There is also a structure similar to the layered LiCoO2, which charges and discharges at low current between 4.3 and 3.4V, and has a reversible capacity of up to 270mAh/g. It will not transform into spinel LixMn2O4 at about 3V, and has good structural stability during charge and discharge.

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