Battery special graphiteEffect of anode on fast charging performance of lithium-ion power battery

Since its inception, lithium-ion batteries have been widely used in many fields. At present, lithium-ion batteries are not only widely used in electronic products such as mobile phones, digital cameras, and tablet computers, but also in the application of vehicle power supplies. Some breakthroughs have been made; from the analysis of the future development of lithium-ion batteries, market economy demand: fast-charging lithium-ion batteries will become an important research direction of lithium-ion batteries.

In order to improve the fast charging performance of graphite anode materials for batteries, a series of graphite anode materials made of different coke materials were prepared through experiments. And the particle size, polarization and XRD tests were carried out, and the lithium ion battery rate charging and rate charging were made. cycle test and analysis of the test results.

Analysis of the fast charging mechanism of lithium-ion power batteries and the effect of battery-specific graphite on the fast charging of lithium-ion batteries through batteries

Taking the positive lithium cobalt oxide and the negative graphite as an example, the positive and negative reactions during the charging process of the lithium-ion battery are as follows:

Positive reaction condition equation: LiCoO2 → Li1-xCoO2 xLi xe-

Negative reaction equation: xLi Xe -- 6C → LixC6

When the lithium-ion power battery is charged, part of Li of lithium cobalt oxide leaves the crystal lattice and can enter different electrolytes, and then migrates to the crystal lattice (intercalation) of the active research substance carbon of the negative electrode material to generate LixC compound.

In this process, lithium ions migrate and diffuse from the positive electrode to the negative electrode under the action of the electric field and concentration gradient, the liquid phase diffusion occurs in the solution, the electrochemical reaction occurs on the surface of the graphite, and the solid phase diffusion occurs in the solution.

The solid-phase diffusion coefficient of lithium in graphite is relatively small (usually only about 10-10 cm2.s-1), which makes the solid-phase diffusion of lithium in graphite easy to develop into a control research step for our entire working electrode reaction. Therefore, improving the graphite material and improving the solid-state diffusion of lithium in graphite can effectively reduce the risk of polarization and lithium precipitation, and improve the fast charging performance of lithium ion batteries.

Generally speaking, the rapid development of charging will lead to the increase of the internal resistance of lithium-ion batteries and the continuous decline of capacity. We now need to understand its mechanism. At present, the main anode material for commercial lithium-ion batteries is graphite material. The use of graphite materials solves the problem of dendrite precipitation in the negative electrode to a large extent, greatly improves the safety of lithium-ion batteries, and makes the commercialization of lithium-ion batteries possible.

At present, the common graphite anode materials are natural graphite, artificial graphite and so on. During the charging management of the lithium-ion power battery, Li migrates from the positive electrode to the negative electrode and is embedded in the layered structure of the graphite material to form a LiC6 compound, which makes the negative electrode appear a golden yellow color. The main contents of the research on the process of lithium intercalation of the negative electrode include the diffusion of Li in the electrolyte and SEI film, the charge exchange technology on the surface of the negative electrode material, and the diffusion of Li in the solid phase. These processes will directly affect the charging rate of lithium-ion batteries. During the charging management of lithium ion power batteries, the negative electrode will produce concentration polarization and electrochemical polarization, resulting in the negative electrode potential lower than its actual steady-state potential. With the increase of charging rate in China, the polarization will further develop and increase. On the one hand, it will continuously aggravate the occurrence of side reactions, on the other hand, it will affect the formation of a coating and lithium dendrites on the surface of the negative electrode material, resulting in safety problems and capacity reduction.