The ideal of lithium battery cathode material should have what characteristics?

Source: 2020 - 04 - The consumption of 14 hits went on: first lithium is formed by battery cathode material surface of solid liquid interface membrane ( SEI) . Therefore, the ideal of the anode materials should have the following features: high voltage, high volume, high density ( Including compaction density and density of vibration) , good security, multiplier good performance, long service life. At present, which can meet all the requirements of materials according to its structural characteristics are divided into three types, namely layered structure materials LiMO2 ( M=Co, Ni, Mn) 。 With spinel structure of lithium manganese acid ( LiMn2O4) ; LiMPO4 of olivine structure ( M=Fe, Mn, Co, Ni) 。 In recent years, some new structural material, such as silicate, borate and olivine structure derivatives - Plagioclase compounds have also been more and more attention. The anode material, the layered structure at present, LiCoO2 has become the dominant material of the lithium ion battery industry anode material. LiCoO2 is naf_nafeo2 type 2 d layer structure, very suitable for lithium ion nesting. With high voltage, stable discharge, than can is high, the cycle performance is good, the advantages of simple preparation technology, able to adapt to high current charge and discharge. Its theoretical capacity of 274 mAh/g, in order to keep good cycle stability, control capacity is 140 mAh/g. But as the anode material of LiCoO2 battery capacity attenuation, resistance to overcharge ability is poor, and poor thermal stability problems. In order to overcome the LiCoO2 material these defects, often adopt the method of doping modification and coating to improve its stability. Laminar LiMnO2 high theoretical capacity, 285 mah/g, high energy density, non-toxic, low cost. But in the process of charging and discharging, jahn - Teller effect, the structure will change, leading to a material pulverization, reversible capacity drops rapidly. For the preparation of layered structure and stable LiMnO2, can lead other transition metal element Mn - O layer and Mn form composite metal oxides, to improve the stability of the layered structure. Has been reported literature, to join in the laminar LiMnO2 Al, Cr, Co, Ni elements can be stable material layer structure, significantly improve the electrochemical performance of materials. 2. The positive materials of the spinel LiMn2O4 spinel structure has good resistance to overcharge resistance, high thermal stability, rich resources, environmental advantages, is considered to be the most promising lithium ion battery cathode material. But there are also disadvantages about the worse performance of high temperature cycle. Therefore, the spinel LiMn2O4 modification have been the focus of this materials. Mn3O4 as precursor, reaction under 800 ℃, and got excellent electrochemical properties of pure phase spinel LiMn2O4 micro ball. There are some research on pure LiMn compared with 2 m1, coated YPO4 LiMn2O4 has better cycle performance. This is because the YPO4 isolates the positive active material and electrolyte, to prevent the dissolution of Mn3 + inhibits the growth of the cell impedance, thus further improving the thermal stability of the electrode. Three, olivine LiFePO4 cathode material of the structure has good cycle stability, high security, and the advantages of green environmental protection, has been a dynamic research hotspot in the field of lithium ion batteries. With regular oligonucleotides LiFePO4 nuclear structure, belongs to the orthogonal anisotropic crystal system Pmnb clearance group, cell parameters, a = 0. 469海里,b = 1。 033nm, c=0. 601nm。 At present, the synthesis methods of LiFePO4 is solid phase method, coprecipitation method, sol-gel Gel method, water/solvent hot method, microwave method and the carbon thermal reduction process. Due to the low electrical conductivity and ionic conductivity of LiFePO4, the overall electrochemical properties of the material is bad, serious limits its application in actual. Now can be material coated, or doping nano to improve. Fan adopts carbon thermal reduction preparation of LiFePO4 / C ( LFPC) And life1 - 2xtixpo4 /C( LFTPC) 。 Package LFTPC electrical conductivity of carbon doped titanium can reach 10 - 4 s/cm. By the rate will be different than LiFePO4 ( 联赛 Mixed with TiO2, LFTPC crystal structure is very stable, particle size is smaller than the LFP. In different rate of Ti doped LFTPC, doping at a rate of 2% of LFTPC multiplier performance and cycle performance is the best.