CN116190624A - A preparation method of lithium titanate composite material and lithium titanate battery - Google Patents

Abstract

This application relates to the technical field of battery preparation, in particular, to a method for preparing a lithium titanate composite material, a lithium titanate composite material, and a lithium titanate battery. The specific steps of the preparation method for the lithium titanate composite material are as follows: prepare titanate Lithium powder; fully mix the lithium titanate powder with 2%wt carbon coating agent; heat the mixed powder to 1100°C-1300°C at a speed of 15°C/min under the protection of an inert gas and sintered for 6 hours, and finally lowered to below 60°C with the furnace; the sintered powder was transferred to a jet mill for grinding and shaping to remove the bond; after screening and demagnetization, a soft carbon-coated lithium titanate composite was obtained. materials, thereby effectively reducing the resistivity of the negative electrode material, thereby increasing the conductivity of the negative electrode sheet, and finally reducing the interface impedance of the lithium titanate battery and improving the voltage platform.

Description

A preparation method of lithium titanate composite material and lithium titanate battery

technical field

The present application relates to the technical field of battery preparation, in particular, to a preparation method of a lithium titanate composite material, a lithium titanate composite material and a lithium titanate battery.

Background technique

In recent years, lithium-ion batteries have become a research hotspot due to a series of advantages such as high energy density, long cycle life, good thermal stability, environmental protection and pollution-free. Lithium-ion batteries are mainly composed of positive electrode materials, negative electrode materials, separators and electrolytes. The negative electrode material directly affects the electrochemical performance of the battery, mainly including carbon materials, silicon-based materials and titanium oxides.

At present, the most widely used graphite material in the market has high electrical conductivity and theoretical specific capacity (372mAh/g), and the lithium intercalation potential is about 0.2V (vs Li ⁺ /Li). And in the process of charging at low temperature, the problem of lithium precipitation is prone to occur. In order to solve the above problems, titanium oxide can be used as the negative electrode material, and its main component is spinel Li ₄ Ti ₅ O ₁₂ , which has superior cycle performance, stable charge and discharge platform and reliable safety compared with other negative electrode materials. In addition, as a "zero strain" material, Li ₄ Ti ₅ O ₁₂ has great advantages over traditional graphite anode materials in terms of cycle, rate, and safety.

However, the existing Li ₄ Ti ₅ O ₁₂ material is a typical insulating material, which has poor electronic conductivity and severe polarization during charging and discharging, which is not good for battery performance.

Contents of the invention

The purpose of the present application is to provide a preparation method of a lithium titanate composite material, a lithium titanate composite material and a lithium titanate battery, so as to solve the technical problem of low electrical conductivity of the existing lithium titanate composite material.

Technical solutions

In order to achieve the above purpose, according to the first aspect of the present application, a method for preparing a lithium titanate composite material is provided, the method includes the following steps:

a, preparing lithium titanate powder;

b. Fully mix the lithium titanate powder with 2%wt carbon coating agent;

c. Raise the mixed powder to 1100°C-1300°C at a rate of 15°C/min under the protection of an inert gas and sinter for 6 hours, and finally cool down to below 60°C with the furnace;

d. Transfer the sintered powder to a jet mill for grinding and shaping to remove the bond;

e. Obtain soft carbon-coated lithium titanate composite material after screening and demagnetization.

As one of the optional solutions of this technical solution, the carbon coating agent can be a pitch carbon coating agent or a phenolic resin carbon coating agent.

As one of the optional solutions of this technical solution, the step of fully mixing the lithium titanate powder with 2%wt carbon coating agent, specifically includes: mixing the lithium titanate powder with 2%wt carbon coating agent The coating agent is added to the ball mill and mixed for 0.5h-1h.

As one of the optional solutions of this technical solution, the inert gas is nitrogen.

In order to achieve the above purpose, according to the second aspect of the present application, a lithium titanate composite material is provided, which is prepared by any one of the methods described above.

In order to achieve the above object, according to the third aspect of the present application, a lithium titanate battery is provided, including: a matched positive pole piece, a negative pole piece, a separator and an electrolyte, and the material layer on the negative pole piece is as mentioned above Lithium titanate composite material.

As one of the optional solutions of this technical solution, the positive electrode sheet includes: a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, and the negative electrode sheet includes: a negative electrode current collector and a coating In the negative electrode active material layer of the negative electrode current collector, the negative electrode active material layer is the aforementioned lithium titanate composite material.

As one of the optional solutions of the technical solution, the positive electrode active material layer is one of nickel-cobalt lithium manganese oxide, lithium cobalt oxide and lithium manganese oxide.

As one of the optional solutions of this technical solution, the molecular formula of the lithium nickel cobalt manganese oxide is: LiNi _x Co _y Me _z O ₂ , wherein, x+y+z=1; 0.33≤x≤0.8; y>0 ; z>0.

As one of the options of this technical solution, Me in the molecular formula is Mn or Al.

Beneficial effect

Compared with the prior art, the present invention has the following beneficial effects:

The invention provides a lithium titanate composite material preparation method, lithium titanate composite material and lithium titanate battery. The specific steps of the lithium titanate composite material preparation method are as follows: prepare lithium titanate powder; Lithium powder and 2%wt carbon coating agent are thoroughly mixed and uniform; the mixed powder is heated up to 1100°C at a rate of 15°C/min under the protection of an inert gas and sintered for 6 hours, and finally cooled to below 60°C with the furnace ; The sintered powder is transferred to a jet mill for grinding and shaping to remove the bond; after sieving and demagnetization, a soft carbon-coated lithium titanate composite material is obtained; in summary, the application uses no The shaped carbon material is used as the wrapping layer of the composite material, thereby effectively reducing the resistivity of the negative electrode material, thereby increasing the conductivity of the negative electrode sheet, and finally reducing the interface impedance of the lithium titanate battery and improving the voltage platform.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, on the premise of no creative labor, other drawings can also be obtained from these drawings, in which:

Fig. 1 is the scanning electron micrograph of the lithium titanate composite material prepared by the preparation method of the present invention;

Fig. 2 is a schematic diagram of charge and discharge curves of the lithium titanate composite material in the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiment of the application will be clearly and completely described below in conjunction with the embodiment of the application. Obviously, the described embodiment is only a part of the application Examples, but not all examples. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

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

At present, titanium oxide is mostly used as the negative electrode material, and its main component is spinel Li ₄ Ti ₅ O ₁₂ . Compared with other negative electrode materials, it has superior cycle performance, stable charge and discharge platform and reliable safety; in addition, As a "zero strain" material, Li ₄ Ti ₅ O ₁₂ has great advantages over traditional graphite anode materials in terms of cycle, rate, and safety; however, the existing Li ₄ Ti ₅ O ₁₂ materials are typical insulating materials, and electronic The conductivity is poor, and the polarization is serious during the charging and discharging process, which is not good for the performance of the battery.

In order to solve the above technical problems, the first aspect of the present application provides a method for preparing a lithium titanate composite material, the method comprising the following steps:

a, preparing lithium titanate powder;

Specifically, the lithium titanate powder can be purchased directly or the lithium titanate material prepared by a traditional process. Since the preparation process of this process is an existing technology, the detailed steps will not be repeated here.

Specific steps are as follows:

b. Fully mix the lithium titanate powder with 2%wt carbon coating agent;

Specifically, the lithium titanate powder and 2%wt carbon coating agent are added to a ball mill and ball milled for 0.5h-1h, wherein the carbon coating agent can be pitch carbon coating agent or phenolic resin carbon coating Covering agent.

c. Raise the mixed powder to 1100°C-1300°C at a rate of 15°C/min under the protection of an inert gas and sinter for 6 hours, and finally cool down to below 60°C with the furnace;

Wherein, the role of the inert gas in the sintering process is to isolate oxygen. Preferably, nitrogen gas with low cost is used. Of course, other inert gases can also be used, which are not specifically limited in this embodiment.

d. Transfer the sintered powder to a jet mill for grinding and shaping to remove the bond;

e. Obtain soft carbon-coated lithium titanate composite material after screening and demagnetization.

In order to achieve the above purpose, according to the second aspect of the present application, a lithium titanate composite material is provided, which is prepared by any one of the methods described above.

In order to achieve the above purpose, according to the third aspect of the present application, a lithium titanate battery is provided, including: a matched positive pole piece, a negative pole piece, a separator and an electrolyte, and the positive and negative pole materials are the core of the lithium titanate battery Specifically, the positive electrode sheet includes: a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, specifically, the positive electrode active material layer is nickel cobalt lithium manganese oxide, lithium cobalt oxide and One of lithium manganate; preferably, the positive electrode active material layer is set as lithium nickel cobalt manganese oxide, and the molecular formula of this nickel cobalt lithium manganese oxide is: LiNi _x Co _y Me _z O ₂ , wherein, x+y+z= 1; 0.33≤x≤0.8; y>0;z>0, wherein Me in the molecular formula is Mn or Al; in addition, the positive electrode current collector adopts aluminum foil with a thickness of 10-20 μm; the negative electrode sheet includes: negative electrode current collector And the negative electrode active material layer coated on the negative electrode current collector, the negative electrode active material layer is the aforementioned lithium titanate composite material, in addition, the negative electrode current collector adopts 10-20 μm aluminum foil, and the diaphragm is a kind of polymer A composite membrane that separates the positive and negative materials to prevent short circuits while allowing ions to pass freely.

For the convenience of understanding, the specific analysis is carried out by taking the pitch carbon coating agent and the phenolic resin carbon coating agent as examples.

First prepare comparative example, concrete preparation steps are as follows:

Use 10-20μm aluminum foil as the positive current collector;

A positive electrode active material is coated on the surface of the positive electrode current collector to prepare a negative electrode sheet, wherein the positive electrode active material is lithium nickel cobalt manganese oxide LiNi _x Co _y Mn _z O ₂ , where x+y+z=1, 0.33 ≤x≤0.8, y>0, z>0;

Use 10-20μm aluminum foil as the negative electrode collector;

The surface of the negative electrode current collector is coated with a negative electrode active material, wherein the negative electrode active material can be a commercial lithium titanate material or a lithium titanate material prepared by a traditional process. The detailed steps are not repeated here;

providing a polyolefin diaphragm substrate, one side of the polyolefin diaphragm substrate is coated with a ceramic coating to prepare the diaphragm;

Finally, the lithium titanate battery as a comparative example can be produced by assembling the positive pole piece, diaphragm, and negative pole piece prepared above according to the traditional process, and then injecting the electrolyte solution.

Example 1

Commercial lithium titanate powder is selected as the raw material, and the lithium titanate powder and 2%wt pitch carbon coating agent are added to a ball mill and ball milled for 0.5h-1h until the mixture is uniform.

Put the mixed powder into a crucible and move it into a carbonization furnace. Under the protection of a nitrogen atmosphere, the temperature is raised to 1100°C at a rate of 15°C/min and sintered for 6 hours, and finally the temperature is lowered to below 60°C with the furnace;

Transfer the sintered powder to a jet mill for milling and shaping to remove the bond;

After screening and demagnetization, a soft carbon-coated lithium titanate composite material was obtained.

The morphology of the prepared lithium titanate composite material is shown in Figure 1. After characterization, it was determined that the specific capacity of the material was 167mAh/g, the particle size D50 was 9μm, the specific surface area was 10m ² /g, and the tap density was 1.0g/cm ^3. The compacted density is 1.95g/cm ³ .

The lithium titanate battery of this embodiment is prepared by the following steps:

Use 10-20μm aluminum foil as the positive current collector;

A positive electrode active material is coated on the surface of the positive electrode current collector to prepare a negative electrode sheet, wherein the positive electrode active material is lithium nickel cobalt manganese oxide LiNi _x Co _y Mn _z O ₂ , where x+y+z=1, 0.33 ≤x≤0.8, y>0, z>0;

Use 10-20μm aluminum foil as the negative electrode collector;

A negative electrode active material is coated on the surface of the negative electrode current collector, wherein the negative electrode active material is the lithium titanate composite material prepared above;

providing a polyolefin diaphragm substrate, one side of the polyolefin diaphragm substrate is coated with a ceramic coating to prepare the diaphragm;

Finally, it is only necessary to assemble the positive pole piece, separator, and negative pole piece prepared above according to the traditional process, and then inject the electrolyte solution to produce a lithium titanate battery.

Example 2

The lithium titanate composite material of this embodiment is prepared by the following steps:

Commercial lithium titanate powder is selected as the raw material, and the lithium titanate powder and 2%wt phenolic resin carbon coating agent are added to a ball mill and ball milled for 0.5h-1h until the mixture is uniform.

Put the mixed powder into a crucible and move it into a carbonization furnace. Under the protection of a nitrogen atmosphere, the temperature is raised to 1300°C at a rate of 15°C/min and sintered for 6 hours, and finally the temperature is lowered to below 60°C with the furnace;

Transfer the sintered powder to a jet mill for milling and shaping to remove the bond;

After screening and demagnetization, a soft carbon-coated lithium titanate composite material was obtained.

The morphology of the prepared lithium titanate composite material is shown in Figure 1. After characterization, its particle size D50 was determined to be 9.2 μm, the specific surface area was 9.5 m ² /g, the tap density was 0.98 g/cm ³ , and the compacted density was 1.95 g/cm ³ , the specific capacity of the material is 168mAh/g.

The lithium titanate battery of this embodiment is prepared by the following steps:

The positive current collector is prepared by using 10-20 μm aluminum foil;

A positive electrode active material is coated on the surface of the positive electrode current collector to prepare a negative electrode sheet, wherein the positive electrode active material is lithium nickel cobalt manganese oxide LiNi _x Co _y Mn _z O ₂ , where x+y+z=1, 0.33 ≤x≤0.8, y>0, z>0;

The negative electrode current collector is prepared by using 10-20 μm aluminum foil;

A negative electrode active material is coated on the surface of the negative electrode current collector, wherein the negative electrode active material is the lithium titanate composite material prepared above;

providing a polyolefin diaphragm substrate, one side of the polyolefin diaphragm substrate is coated with a ceramic coating to prepare the diaphragm;

Finally, it is only necessary to assemble the positive pole piece, separator, and negative pole piece prepared above according to the traditional process, and then inject the electrolyte solution to produce a lithium titanate battery.

comparative example

The performance tests of the negative electrode materials in different examples and comparative examples, the comparative results are shown in the following table.

The electrical conductivity of the negative electrode sheets prepared in different examples and comparative examples was tested, and the specific test results are shown in the following table.

group Conductivity (s/cm) Example 1 0.0292 Example 2 0.0275 comparative example 0.0165

The platform voltage of the pouch battery prepared in different examples and comparative examples was tested, and the specific test results are shown in the table below.

group Platform voltage (V) Example 1 2.217 Example 2 2.215 comparative example 2.172

To sum up, the application adopts amorphous carbon material as the cladding layer of the composite material, thereby improving the conductivity of the negative electrode sheet, finally reducing the interface impedance of the lithium titanate battery, and improving the voltage platform.

In summary, by analyzing the data in the aforementioned comparison table, it can be seen that the design of this scheme can effectively solve the problem of low conductivity of conventional lithium titanate materials, thereby effectively reducing the resistivity of the negative electrode sheet and the interface impedance of lithium titanate batteries , improving the voltage platform of the lithium titanate battery; in addition, the carbon layer coating in the preparation method of the present application is uniform and stable, thereby ensuring the high rate and long cycle performance of the lithium titanate battery. In addition, the amorphous carbon material (soft carbon, hard carbon) as the coating layer of the composite material can additionally increase the lithium storage capacity of the electrode material; at the same time, the conductivity of the pole piece is improved, which can reduce the amount of conductive agent in the negative electrode formulation. In turn, the proportion of active materials is increased, and the design capacity of the battery is increased.

Each embodiment in this specification is described in a progressive manner, and several embodiments focus on the differences from other embodiments, and the same and similar parts in each embodiment can be referred to each other.

It should be noted that in the specification and claims of this application and the above drawings, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation without necessarily requiring or implying any such actual relationship or particular order or sequence between these entities or operations. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein, for example, can be practiced in sequences other than those illustrated or described herein.

Moreover, the terms "comprising", "comprising" and "having" and any variations thereof or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also other elements not expressly listed, or elements inherent in the process, method, article, or apparatus. For example, a process, method, system, product, or device comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include steps or units not explicitly listed or for these processes, methods, products, or Other steps or units inherent to equipment. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above descriptions are only specific implementation manners of the present application, so that those skilled in the art can understand or implement the present application. Various modifications and variations to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Any modifications, equivalent replacements and improvements made within the spirit and principles of this application shall be included within the protection scope of this application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims (10)

1. a lithium titanate composite material preparation method, is characterized in that, described method comprises the steps: a, preparing lithium titanate powder; b. Fully mix the lithium titanate powder with 2%wt carbon coating agent; c. Raise the mixed powder to 1100°C-1300°C at a rate of 15°C/min under the protection of an inert gas and sinter for 6 hours, and finally cool down to below 60°C with the furnace; d. Transfer the sintered powder to a jet mill for grinding and shaping to remove the bond; e. Obtain soft carbon-coated lithium titanate composite material after screening and demagnetization. 2. The preparation method of lithium titanate composite material according to claim 1, characterized in that, the carbon coating agent can be a pitch carbon coating agent or a phenolic resin carbon coating agent. 3. The preparation method of lithium titanate composite material according to claim 1, characterized in that, the step of fully mixing the lithium titanate powder with 2%wt carbon coating agent, specifically comprises: mixing the lithium titanate powder The lithium titanate powder and 2%wt carbon coating agent are added to a ball mill and ball milled for 0.5h-1h. 4. The preparation method of lithium titanate composite material according to claim 1, wherein the inert gas is nitrogen. 5. A lithium titanate composite material, characterized in that it is prepared by the method according to any one of claims 1-4. 6. A lithium titanate battery, characterized in that it comprises: a positive pole piece, a negative pole piece, a diaphragm and an electrolyte that match, and the material layer on the negative pole piece is lithium titanate as claimed in claim 5 composite material. 7. The lithium titanate battery according to claim 6, wherein the positive pole piece comprises: a positive current collector and a positive active material layer coated on the positive current collector, and the negative pole piece comprises : negative electrode current collector and the negative electrode active material layer coated on the negative electrode current collector, the negative electrode active material layer is lithium titanate composite material as claimed in claim 5. 8 . The lithium titanate battery according to claim 7 , wherein the positive electrode active material layer is one of lithium nickel cobalt manganese oxide, lithium cobalt oxide and lithium manganese oxide. 9. The lithium titanate battery according to claim 8, wherein the molecular formula of the lithium nickel cobalt manganate is: LiNi _x Co _y Me _z O ₂ , wherein x+y+z=1; 0.33≤ x≤0.8; y>0;z>0. 10. The lithium titanate battery according to claim 9, wherein Me in the molecular formula is Mn or Al.

Images