How to Improve the Performance of Lithium Battery Positive Material

It is a new idea to raise the energy density of lithium-ion battery in recent years to increase the voltage of the cathode material. Gaodianya materials include two kinds of positive materials: crystal structure and olivine crystal structure. LiMPO4(M = Co, Ni) is a typical Gaodianya olivine crystal structure material. Among them, LiCoPO4 has a 4.8 V discharge potential, LiNIPO4 has a 5.2 V discharge potential, and the theoretical capacity is close to 170 mAh/g.

5.2 V is currently the highest charging and discharging voltage, because the electrolyte that can be matched has not yet been developed, so there have been no reports on the performance of lithium batteries for LiNiPO4 positive materials, and there are many reports on LiCoPO4 materials. However, the circulating charge and discharge performance of LiCoPO4 materials obtained under the existing electrolytic fluid system is very poor.

The side effects of olivine crystal structure under Gaodianya's condition are three: 1. The positive polar material reacts with the electrolyte to form a solid liquid interface layer; 2, the electrolyte will partially dissolve Co ions, greatly deteriorating the lithium battery cycle charging and discharging performance; 3, poor conductivity, low conductivity. Therefore, the Gaodianya crystal structure must be applied with the necessary means to improve its performance. There are three methods.

1, nanotechnology. The small particles of nanoscale are used as active substances and have shorter transmission and diffusion pathways of lithium ions and electrons than the large particles of micron.

2, doping. Unlike the crystal structure of actinite, which can be doped cations or doped anions, olivine crystal structure only doped cations to increase the conductivity of positive materials.

3, coating. Non-crystalline carbon coatings can form interconnected electron high-speed transmission channels, thereby improving performance, especially the first discharge capacity and the charging and discharging cycle performance.

In general, the LiMPO4(M = Co, Ni) of olivine crystal structure has more theoretical capacity than the spinel crystal structure, but due to low conductivity and poor cyclic performance, This makes the research and development of the lithium ion battery of this cathode material has many achievements in the development of lithium ion batteries without crystal crystal structure, while entering the industrialization stage requires more advanced performance improvement technology, which mainly refers to the power lithium battery for electric vehicles.

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