Three technologies improve the performance of lithium battery cathode materials

Three technologies improve the performance
of lithium battery cathode materials.
In recent years, increasing the voltage of the cathode material of lithium-ion batteries is a new idea
to improve the energy density of lithium-ion batteries.
High-voltage materials include spinel-like crystal structure and olivine-like crystal structure, two cathode materials
.
LiMPO4 (M=Co,Ni) is a typical high-voltage olivine-like crystal structure material
.
Among them, LiCoPO4 has a discharge potential of 4.
8V, and LiNiPO4 has a discharge potential of 5.
2V, and the theoretical capacity is close to 170mAh/g
.

5.
2V is the highest charge and discharge voltage at present, because no electrolyte has been developed that can match it, so there have been no reports on the performance of LiNiPO4 cathode material lithium battery, more reports on LiCoPO4 material, but the LiCoPO4 material cyclic charge and discharge performance obtained under the existing electrolyte system is very poor
.

The olivine crystal structure exhibits three side effects under high voltage conditions: 1.
The cathode material will react with the electrolyte to form a solid-liquid interface layer; 2.
The electrolyte will partially dissolve Co ions, which will greatly deteriorate the cyclic charge and discharge performance of lithium batteries; 3.
Poor conductivity and low
conductivity.
Therefore, the use of high-voltage olivine crystal structures must be used by the necessary means to improve its performance, which are three
.

1.
Nano Nano.

The active material uses small nanoscale particles and has a shorter lithium ion and electron transport diffusion path
than micron-sized large particles.

2.
Doping
.
Unlike spinel-like crystal structures, which can be doped with both cations and anions, olivine-like crystal structures are doped only with cations to improve the conductivity
of the cathode material.

3.
Coating
.
Amorphous carbon coatings can form interconnected electronic high-speed transmission channels, which improve performance, especially first discharge capacity and charge-discharge cycle performance
.

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