CN108172821A - A method for eliminating residual lithium and preparing lithium-ion conductor-coated high-nickel ternary cathode material - Google Patents

Abstract

The invention belongs to lithium ion battery material technical fields, specially a kind of to eliminate residual lithium and prepare the method that lithium ion conductor coats the positive electrode of nickelic ternary.The method of the present invention is：By nickelic tertiary cathode material and lithium ion conductor precursor with certain proportion ball milling in the ball mill；The mixed material that above-mentioned processing is obtained is calcined to obtain the nickelic tertiary cathode modified material of lithium ion battery in air.The method of the present invention is simple for process, easy to operate, using dry ball milling mode, the adverse effect that the introducing of moisture is avoided to generate nickelic ternary material.Meanwhile this method has been formed in situ lithium ion conductor clad using the residual lithium in surface, accelerates lithium ion diffusion rate, improves interface stability, obtain excellent chemical property.

Description

A method for eliminating residual lithium and preparing lithium-ion conductor-coated high-nickel ternary positive electrode materials method

technical field

The invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a method for preparing a high-nickel ternary cathode material coated with a lithium-ion conductor.

Background technique

In today's world where resources are increasingly depleted, it is particularly important to develop green and clean energy. Lithium-ion batteries have attracted the attention of scientific research and commercial development due to their outstanding advantages such as high energy density, high working voltage, good cycle performance, small self-discharge, small size, and no memory effect. Its application field has rapidly expanded from the initial mobile communication to various aspects of entertainment, military, aerospace, medical treatment, etc., including various portable electronic products, and is developing into large and medium-sized energy storage equipment and power supply. This is of great significance to reducing dependence on petroleum energy and reducing pollutant emissions. The electrochemical performance of lithium-ion batteries mainly depends on the electrode materials used. Compared with the negative electrode, the capacity and rate performance of the positive electrode materials are generally poor, so the positive electrode materials have been widely studied.

Compared with the traditional lithium cobalt oxide, the high-nickel ternary cathode material is considered to be one of the best cathode materials for the development of low-cost and high specific energy density lithium-ion batteries due to its relatively low cost and high discharge specific capacity. However, the residual lithium on the surface of the high-nickel ternary material is relatively high, which affects the processing performance of the pole piece. In addition, the residual lithium on the surface accelerates the decomposition of the electrolyte, reduces the stability of the interface, and leads to poor electrochemical performance. Under high temperature and high pressure conditions, batteries are prone to unsafe problems such as flatulence and explosion, which greatly limit the practical application of high-nickel ternary cathode materials. At present, the improvement method widely adopted by people is surface coating, that is, depositing a coating film on the surface of high-nickel ternary particles to reduce the contact area between the active material and the electrolyte and improve the interface stability. However, high-nickel ternary materials are sensitive to moisture and carbon dioxide, and lithium carbonate or lithium hydroxide by-products will be generated during storage. Therefore, the choice of coating species and coating method is particularly important for the performance of high-nickel ternary materials.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a lithium ion conductor-coated high-nickel ternary positive electrode material that can accelerate the diffusion rate of lithium ions and improve interface stability.

The method for preparing a lithium ion conductor coated high-nickel ternary positive electrode material provided by the present invention is to use the residual lithium on the surface of the high-nickel ternary positive electrode material to form a lithium ion conductor coating layer in situ, eliminate the residual lithium, and obtain a lithium ion conductor Coated high-nickel ternary positive electrode materials; the coating method adopts dry ball milling to avoid the adverse effects of the introduction of moisture on high-nickel ternary materials. At the same time, the lithium ion conductor coating layer is formed in situ by using the residual lithium on the surface, which accelerates the diffusion rate of lithium ions, improves the interface stability, and obtains excellent electrochemical performance.

The method for preparing a lithium-ion conductor-coated high-nickel ternary positive electrode material provided by the present invention has specific steps as follows:

(1) Mill the high-nickel ternary cathode material and lithium ion conductor precursor in a ball mill to obtain a uniform mixture;

(2) Calcining the mixed material obtained in step (1) in air to obtain a high-nickel ternary positive electrode material coated with a lithium ion conductor.

As a preferred technical solution, in step (1), the nickel-rich ternary material is selected from LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _{0.2 Mn} 0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , One or more of LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

Preferably, in step (1), the lithium ion conductor precursor is selected from one or more of ammonium metavanadate, titanium dioxide, molybdenum trioxide, and silicon dioxide.

Preferably, in step (1), the molar ratio of the nickel-rich ternary positive electrode material to the lithium ion conductor precursor is 1: (0.1-1.0).

Preferably, in step (1), the ball mill is a planetary ball mill.

Preferably, in step (1), no milling aids and milling beads are added during the ball milling process.

Preferably, in step (1), the ball milling speed is 100-400 rpm.

Preferably, in step (1), the ball milling time is 3-6 hours.

Preferably, in step (2), the calcination temperature is 300-500°C.

Preferably, in step (2), the calcination time is 4-6 hours.

Preferably, in step (2), the lithium ion conductor coating layer is one or more of Li ₃ VO ₄ , Li ₂ TiO ₃ , Li ₂ MoO ₄ , and Li ₂ SiO ₃ .

The method for preparing a lithium ion conductor-coated high-nickel ternary positive electrode material in the present invention does not add any ball milling aids and ball milling beads, ball mills the high-nickel ternary material and the lithium ion conductor precursor at a certain ratio, controls the ball milling speed and time and After calcining, the lithium ion conductor coating layer is obtained, the process is simple, and the operation is convenient. This method avoids the introduction of moisture and significantly reduces surface alkalinity. At the same time, the lithium ion conductor coating layer is formed in situ by using the residual lithium on the surface, which accelerates the diffusion rate of lithium ions, reduces the surface impedance, improves the interface stability, and obtains excellent electrochemical performance.

Description of drawings

In order to more clearly illustrate the technical solutions in this embodiment of the invention, the drawings that need to be used in the embodiments are briefly introduced below. These drawings are only some embodiments of the present invention and do not constitute an improper limitation of the present invention. .

Fig. 1 is the X-ray diffractogram of uncoated and embodiment 1, embodiment 2, the product obtained in embodiment 3.

Fig. 2 is a scanning electron micrograph of Li ₃ VO ₄ coated LiNi _0.6 Co _0.2 Mn _0.2 obtained in Example 1.

Fig. 3 is a scanning electron micrograph of Li ₃ VO ₄ coated LiNi _0.6 Co _0.2 Mn _0.2 obtained in Example 2.

Fig. 4 is a scanning electron micrograph of Li ₃ VO ₄ coated LiNi _0.6 Co _0.2 Mn _0.2 obtained in Example 3.

Fig. 5 is uncoated and the cycle performance curve of the product obtained in Example 1, Example 2, and Example 3.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Embodiments of the present invention will be specifically explained below in conjunction with the accompanying drawings.

Example 1

A method for preparing lithium ion conductor Li ₃ VO ₄ coated high-nickel ternary positive electrode material LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , comprising the following steps;

(1) Weigh 5 g of LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and 1.21g of NH ₄ VO ₃ and add them to the planetary ball mill, and ball mill at 100-400rmp for 3-6 hours to obtain a uniform mixture;

(2) Calcining the mixed material obtained in step (1) in a muffle furnace at a temperature of 300-500°C for 4-6 hours to obtain a high-nickel ternary cathode material LiNi _0.6 coated with a lithium ion conductor Li ₃ VO ₄ Co _0.2 Mn _0.2 O ₂ , where the molar ratio of Li ₃ VO ₄ and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is 1:0.2.

Example 2

Same as Example 1, the difference is:

The molar ratio of Li ₃ VO ₄ and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is 1:0.4.

Example 3

Same as Example 1, the difference is:

The molar ratio of Li ₃ VO ₄ and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is 1:0.8.

Example 4

A method for preparing lithium ion conductor Li ₂ TiO ₃ coated high-nickel ternary positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , comprising the following steps;

(1) Weigh 5 g of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and 0.82 g of TiO ₂ and add them to the planetary ball mill, and ball mill at 100-400rmp for 3-6 hours to obtain a uniform mixture;

(2) Calcining the mixed material obtained in step (1) in a muffle furnace at a temperature of 300-500°C for 4-6 hours to obtain a high-nickel ternary cathode material LiNi _0.8 coated with a lithium ion conductor Li ₂ TiO ₃ Co _0.1 Mn _0.1 O ₂ .

Example 5

A method for preparing lithium ion conductor Li ₂ MoO ₄ coated high-nickel ternary positive electrode material LiNi _0.8 Co _0.15 Al _0.05 O ₂ , comprising the following steps;

(1) Weigh 5 g of LiNi _0.8 Co _0.15 Al _0.05 O ₂ and 1.49 g of MoO ₃ into a planetary ball mill, and ball mill at 100-400rmp for 3-6 hours to obtain a uniform mixture;

(2) Calcining the mixed material obtained in step (1) in a muffle furnace at a temperature of 300-500°C for 4-6 hours to obtain a high-nickel ternary cathode material LiNi _0.8 coated with a lithium ion conductor Li ₂ TiO ₃ Co _0.1 Mn _0.1 O ₂ .

The effects of the embodiments of the present invention will be described below by taking the obtained lithium-ion conductor Li ₂ MoO ₄ coated with high-nickel ternary cathode material LiNi _0.8 Co _0.15 Al _0.05 O ₂ as an example.

X-ray diffraction (XRD) test

The XRD test was carried out on the uncoated sample, the Li ₃ VO ₄ coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ cathode material obtained in Example 1, Example 2, and Example 3, and the results are shown in FIG. 1 . Due to the small amount of coating, the crystal results of materials coated with different amounts of Li ₃ VO ₄ are still pure phases without any impurity peaks.

Scanning electron microscope (SEM) test

The Li ₃ VO ₄ coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ cathode materials obtained in Example 1, Example 2, and Example 3 were subjected to SEM testing, and the results are shown in Figures 2, 3, and 4. It can be seen that nanoparticles are evenly attached to the surface of the spherical positive electrode material, forming a Li ₃ VO ₄ coating layer, and the more coating amount, the more nanoparticles on the surface, and the denser the distribution.

Electrochemical Performance Evaluation

The uncoated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and the Li ₃ VO ₄ obtained in Example 1, Example 2, and Example 3 were coated with LiNi _0.6 Co _0.2 Mn _0.2 O ₂ positive electrode materials to form a CR2016 button battery , for electrochemical performance evaluation. The positive electrode material, conductive agent and binder are mixed according to the ratio of 8:1:1, and then coated on the aluminum foil current collector with a certain thickness. With 1.0mol/L LiPF ₆ /EC+DEC (volume ratio 1:1) as the electrolyte, Li sheet as the negative electrode, and Cellgard-2400 polypropylene membrane made in the United States as the diaphragm, it is assembled into a button-type in a glove box filled with argon. Battery. Then, the cycle life test of the prepared materials was carried out on the LandCT2001A battery test system produced by Wuhan Jinnuo Electronics Co., Ltd. The voltage range is 3.0-4.3V. The first five charge and discharge cycles of the battery are pre-activated with a current density of 36mA/g, and the subsequent cycles are charged and discharged with a current density of 90mA/g.

From the results of the electrochemical performance test, it can be seen that the cycle performance of the products obtained in Example 1, Example 2, and Example 3 shows different degrees of improvement. Compared with the capacity retention rate of 92.8% of the uncoated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , the capacity retention rates of the titania-coated lithium manganate obtained in Example 1, Example 2, and Example 3 were 95.1%, 96.1%, respectively. %, 95.6% (see Figure 5 for details).

The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to this practice are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (5)

1. a kind of eliminate residual lithium and prepare the method that lithium ion conductor coats the positive electrode of nickelic ternary, which is characterized in that tool Body step is：

（1）By nickelic tertiary cathode material and lithium ion conductor presoma ball milling in the ball mill, uniform mixed material is obtained； Wherein, the molar ratio of nickelic tertiary cathode material and lithium ion conductor presoma is 1：（0.1-1.0）；

（2）By step（1）Obtained mixed material is calcined in air, and calcination temperature is 300-500 DEG C, calcination time 4-6 Hour is to get the nickelic tertiary cathode material coated to lithium ion conductor.

2. the method as described in claim 1, which is characterized in that step（1）Described in nickelic ternary material be selected from LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂、LiNi_0.8Co_0.1Mn_0.1O₂、LiNi_0.8Co_0.15Al_0.05O₂In one kind or It is a variety of.

3. method as claimed in claim 2, which is characterized in that step（1）Described in lithium ion conductor presoma be selected from NH₄VO₃、TiO₂、MoO₃、SiO₂In it is one or more.

4. the method as described in claim 1,2 or 3, which is characterized in that step（1）Described in ball mill be planetary type ball-milling Machine；Ball milling speed is 100-400rmp；Ball-milling Time is 3-6 hours.

5. method as claimed in claim 4, which is characterized in that the step（2）Middle lithium ion conductor clad is Li₃VO₄、 Li₂TiO₃、Li₂MoO₄、Li₂SiO₃In it is one or more.