Lithium ion battery positive electrode and preparation method and application thereof

Abstract

The invention provides a lithium ion battery positive electrode and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. Specifically, through an atomic layer deposition method, lithium hydroxide is obtained through deposition on the surface of a positive electrode, and then zirconium oxide is obtained through continuous deposition; and then, repeating the steps for 10-60 times to obtain the positive electrode coated with the lithium zirconium oxide on the surface. The lithium zirconium oxide coated electrode is obtained by directly depositing the coating on the surface of the positive electrode of the lithium ion battery through the atomic layer precipitation method; the prepared coating layer is compact and uniform, interface side reaction between the positive electrode material and electrolyte can be prevented, the lithium ion intercalation and deintercalation efficiency can be improved, the effect of improving the rate capability and cycle performance of the lithium ion battery can be realized, and the application prospect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium ion battery positive electrode and a preparation method and application thereof. Background Art

[0002] The interface of lithium-ion batteries (LIBs) plays a key role in battery safety, cyclability and coulombic efficiency. The interface is located between the positive or negative electrode and the electrolyte. During the first charge and discharge process of the battery, the electrode material and the electrolyte react chemically at the solid-liquid interface. This reaction leads to the formation of a layer of covering material, the SEI film, on the surface of the electrode material. During the subsequent charge and discharge of the battery, the SEI film will continue to form: on the one hand, the electrolyte solvent and salt will continue to decompose and produce new decomposition products, which will further react with the components in the SEI film, causing the composition and structure of the SEI film to change; on the other hand, during the charge and discharge process of the battery, lithium ions will continue to embed from the positive electrode into the negative electrode and then escape from the negative electrode back to the positive electrode. In this process, the embedding and extraction of lithium ions will cause certain damage to the SEI film and promote the formation of new SEI films; in some other aspects, environmental conditions such as temperature, humidity and oxygen concentration will also have a certain impact on the SEI.

[0003] Although the SEI film plays an important role in the cycle stability and service life of the battery, it is unstable and will continue to decompose and form easily depleted electrolytes, causing the battery to gradually fail, which also triggers a series of negative effects. Electrode surface coating is an effective process to solve the negative effects of the SEI film; in order to improve the stability and performance of the electrode, scholars have begun to seek more methods for electrode surface coating.

[0004] Common coating methods include co-precipitation, sol-gel, hydrothermal method, chemical vapor deposition, etc. Among them, the co-precipitation method requires the control of complex chemical reaction processes and precise control of reaction conditions. It is difficult to control the uniformity of the coating layer with the hydrothermal method, and there may be defects such as local coating being too thin or too thick; the hydrothermal method may also damage the material during the coating process. The sol-gel method can produce a nanoscale and uniform coating layer with good film-forming and adhesion properties; however, the preparation process is complicated, requires a long reaction time and high temperature conditions, and is difficult to mass produce. The coating layer produced by the chemical vapor deposition method is of high quality and purity, but the equipment and raw material costs are high, and the production efficiency is low.

[0005] Atomic layer deposition (ALD) has become a new surface modification technology, with atomic-level growth accuracy at room temperature, and can precisely control the thickness and uniformity of the coating layer at the nanoscale; at the same time, the interface between the coating layer and the electrode material is clear and has strong bonding, which helps to improve the stability and cycle life of the battery. So far, it is the only technology that can deposit coatings directly on prefabricated electrodes, and the coating has many advantages, such as acting as a physical barrier between the electrode and the electrolyte, reducing irreversible side reactions, protecting the electrode from corrosion, and enhancing the mechanical integrity of the electrode.

[0006] Furthermore, for coated materials, lithium-containing coatings generally exhibit better ionic conductivity than binary oxides (such as Al2O3, TiO2, and ZrO2), which is beneficial for the transport of lithium ions through the interface. If lithium-containing coatings are combined with atomic layer deposition technology, it is expected to solve the negative effects of SEI.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first purpose of the present invention is to provide a method for preparing a positive electrode of a lithium-ion battery, which is mainly used to solve the technical defects of the interface side reaction between the positive electrode material and the electrolyte, and the conventional coating method that affects the lithium ion deintercalation and uneven coating thickness.

[0009] A second object of the present invention is to provide a positive electrode for a lithium ion battery.

[0010] A third object of the present invention is to provide a lithium ion battery.

[0011] A fourth object of the present invention is to provide an electrical device.

[0012] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0013] A method for preparing a positive electrode of a lithium ion battery comprises the following steps:

[0014] (1) By atomic layer deposition, lithium hydroxide is first deposited on the surface of the positive electrode, and then zirconium oxide is further deposited;

[0015] (2) Repeat step (1) 10 to 60 times to obtain a surface-modified positive electrode coated with lithium zirconium oxide.

[0016] A lithium ion battery positive electrode is prepared by adopting the preparation method of the lithium ion battery positive electrode.

[0017] A lithium ion battery comprises the lithium ion battery positive electrode.

[0018] An electrical device comprises the lithium-ion battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses atomic layer deposition (ALD) to modify the surface of the positive electrode, and uses the atomic layer deposition method to sequentially and cyclically coat LiOH and ZrO2 with atomic-level growth accuracy on the electrode, and finally generates lithium zirconium oxide (LZOs) on the electrode surface; the prepared lithium zirconium oxide coating is dense and uniform, which can effectively prevent the interface side reaction between the positive electrode material and the electrolyte, accelerate the efficiency of lithium ion insertion and extraction, and finally obtain the effect of improving the rate performance and cycle performance of the lithium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A rate performance test diagram of Example 1 of the present invention is provided. DETAILED DESCRIPTION

[0022] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but those skilled in the art will appreciate that the embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] A first aspect of the present invention is to provide a method for preparing a positive electrode of a lithium ion battery.

[0024] The preparation method in the first aspect of the present invention mainly comprises the following two steps: (1) firstly depositing lithium hydroxide on the surface of the positive electrode by atomic layer deposition, and then continuing to deposit zirconium oxide; (2) repeating step (1) 10 to 60 times to obtain a surface-modified positive electrode coated with lithium zirconium oxide.

[0025] As a preferred embodiment, the positive electrode of the present invention (referring to the positive electrode raw material that has not been processed by the preparation method of the present invention) can adopt any existing commercial positive electrode or any self-made unconventional positive electrode. It can be understood that any electrode with a lithium-ion secondary battery and a positive electrode function can be used as the positive electrode of the present invention.

[0026] As a more preferred embodiment, the positive electrode is made of NMC622. In a further preferred embodiment, the active material of the positive electrode is made of LiNi 0.6 Mn 0.2 Co 0.2 O2, also known as NMC622.

[0027] As a preferred embodiment, in step (1), the environmental conditions of the atomic layer deposition method include: a temperature of 175°C to 225°C and a vacuum condition. In some more preferred embodiments, the temperature of the atomic layer deposition method is any one of 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225 (°C) or a numerical range consisting of any two of them.

[0028] As a preferred embodiment, the atomic layer deposition system and the glove box used in the atomic layer deposition method in step (1) are integrated together to ensure that the thin film obtained during the deposition process is not exposed to the air.

[0029] As a preferred embodiment, in step (1), lithium hydroxide is prepared by the atomic layer deposition method, wherein the lithium source used includes lithium tert-butoxide (LTB), and the purity of the lithium source is ≥98%.

[0030] As a preferred embodiment, in step (1), zirconium oxide is prepared by the atomic layer deposition method, wherein the zirconium source used includes tetrakis(dimethylamino)zirconium(IV) (TDMA-Zr).

[0031] As a preferred embodiment, before the atomic layer deposition method is performed, the lithium source is preheated to 140°C to 160°C, and the zirconium source is preheated to 65°C to 85°C. In some more preferred embodiments, the preheating temperature of the lithium source is any one of 140, 145, 150, 155, 160 (°C) or a numerical range consisting of any two thereof, and the preheating temperature of the zirconium source is any one of 65, 70, 75, 80, 85 (°C) or a numerical range consisting of any two thereof.

[0032] As a preferred embodiment, the lithium hydroxide deposition method comprises: introducing a lithium source and deionized water into an atomic layer deposition chamber for 1 second to 6 seconds.

[0033] As a more preferred embodiment, the flow rate of the lithium source is 150 sccm to 200 sccm.

[0034] When the lithium hydroxide is deposited, the flow rate of the deionized water is 150 sccm to 250 sccm.

[0035] As a more preferred embodiment, the continuous introduction time of the lithium source and deionized water is 2s to 4s. In some optional embodiments, the continuous introduction time of the lithium source and deionized water includes but is not limited to any one of 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2, 3.4, 3.5, 3.6, 3.8, 4 (s) or a numerical interval consisting of any two of them.

[0036] As a preferred embodiment, the zirconium oxide deposition method comprises: introducing a zirconium source and deionized water into an atomic layer deposition chamber for 1 second to 6 seconds.

[0037] As a more preferred embodiment, the flow rate of the zirconium source is 150 sccm to 200 sccm.

[0038] When the zirconium oxide is deposited, the flow rate of the deionized water is 150 sccm to 250 sccm.

[0039] As a more preferred embodiment, the continuous introduction time of the zirconium source and deionized water is 2s to 4s. In some optional embodiments, the continuous introduction time of the zirconium source and deionized water includes but is not limited to any one of 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2, 3.4, 3.5, 3.6, 3.8, 4 (s) or a numerical interval consisting of any two of them.

[0040] As a preferred embodiment, step (1) includes the following steps: introducing a lithium source and deionized water into an atomic layer deposition chamber to deposit lithium hydroxide; introducing a carrier gas into the atomic layer deposition chamber for 5s to 10s; introducing a zirconium source and deionized water into the atomic layer deposition chamber to deposit zirconium oxide; and then introducing a carrier gas into the atomic layer deposition chamber for 5s to 10s.

[0041] As a more preferred embodiment, the carrier gas includes but is not limited to helium, neon, argon, etc. In a further preferred embodiment, the carrier gas is argon (Ar), and the purity of the carrier gas is ≥99.999%.

[0042] As a preferred embodiment, in step (2), the number of times step (1) is repeated includes but is not limited to any one of 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 (times) or a numerical range consisting of any two of them.

[0043] The second aspect of the present invention is to provide a lithium ion battery positive electrode, which is prepared by the preparation method of the lithium ion battery positive electrode. It is understandable that other positive electrode modification treatment methods can also be used under the premise of following the preparation method described in the first aspect.

[0044] The third aspect of the present invention is to provide a lithium-ion battery, including the lithium-ion battery positive electrode. It is understood that, in addition to the lithium-ion battery positive electrode, the lithium-ion battery should include a negative electrode, an electrolyte, a separator, and other necessary or unnecessary functional elements or packaging components, etc., and those skilled in the art can make any selection and combination thereof; when the lithium-ion battery includes the lithium-ion battery positive electrode of the present invention, whether or not other positive electrode functional structures are used in the lithium-ion battery, it can be regarded as an embodiment of the present invention.

[0045] The fourth aspect of the present invention is to provide an electrical device, including the lithium-ion battery. It is understood that the electrical device can be any device or apparatus that relies on electric energy to work or operate, including but not limited to new energy vehicles, building electrical equipment, industrial electrical appliances, household and agricultural electrical appliances, etc.; when including the lithium-ion battery, any electrical device equipped with the lithium-ion battery can belong to an embodiment of the present invention.

[0046] Example 1

[0047] Step 1: Place the finished NMC622 electrode in an atomic layer deposition chamber. Adjust the chamber temperature to 225°C and evacuate the chamber.

[0048] Step 2: Heat the lithium tert-butoxide precursor to 160°C and heat the tetrakis(dimethylamino)zirconium(IV) precursor to 75°C.

[0049] Step 3: The preheated lithium tert-butoxide and deionized water are introduced into the atomic layer deposition chamber at a flow rate of 200 sccm to generate LiOH for 3 seconds; then argon gas is introduced for 500 ms to clean the chamber.

[0050] Step 4: The preheated tetrakis(dimethylamino)zirconium(IV) and deionized water are introduced into the atomic layer deposition chamber at a flow rate of 200 sccm to generate ZrO2 for 3 seconds; then argon gas is introduced for 500 ms to clean the chamber.

[0051] Step 5: Repeat steps 3 to 4 for a total of 20 cycles to obtain the modified NMC622 electrode uniformly coated with the LZOs film in this embodiment.

[0052] Example 2

[0053] The process is basically the same as Example 1, except that a total of 10 cycles are performed in step 5.

[0054] Example 3

[0055] The process is basically the same as Example 1, except that a total of 30 cycles are performed in step 5.

[0056] Example 4

[0057] The process is basically the same as Example 1, except that a total of 40 cycles are performed in step 5.

[0058] Test example

[0059] A battery was prepared using the modified positive electrodes prepared in each embodiment and comparative example: wherein the negative electrode of the battery was lithium metal, and the electrolyte was: 1.2M LiPF6 dissolved in ethyl carbonate (EC) and methyl carbonate (EMC) (mass ratio was 3:7).

[0060] The positive electrode of the battery was prepared as follows: NMC622 electrode slurry was mixed with 86wt% NMC622 active material, 7wt% carbon black and 7wt% polyvinylidene fluoride binder and n-methylpyridone. The obtained slurry was then cast onto aluminum foil and then expanded into a laminate using a blade. The laminate was first naturally dried in a fume hood for one day and then vacuum dried at 100°C for 10 hours. The obtained electrode was punched into a 7 / 16″ disc with a mass loading of 11.8mg cm -2 .

[0061] The electrodes and electrolytes were assembled into cr-2032 coin cells for electrochemical evaluation. The electrochemical performance of the cells prepared in each embodiment was tested.

[0062] (1) Rate performance test: Cyclic voltammetry (CV) tests were performed on a universal single-channel potentiostat (SP-200, BioLogic, USA) with scan rates of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 mV s between 3.0 and 4.5 V (vs. Li / Li + ), respectively. -1 The charge and discharge characteristics at 5C and 7C were recorded using a battery tester (Neware, BTS2300, Shenzhen, China), and the discharge specific capacity was calculated.

[0063] (2) Cycle performance test: The battery of each embodiment was tested for capacity performance retention after 100 cycles at 3.0V to 4.5V and 3C.

[0064] Table 1

[0065]

[0066] like Figure 1 The figure further provides a comparison diagram of the detection rate performance. Figure 1 "ALD-10", "ALD-20", "ALD-30" and "ALD-40" correspond to the batteries prepared in Example 2, Example 1, Example 3 and Example 4, respectively. Figure 1 The "bare" in the figure corresponds to the battery obtained by replacing the NMC622 electrode product without ALD cycle treatment in the embodiment. The discharge capacity of the above battery was tested under 0.1C, 0.3C, 0.5C, 1C, 3C, 5C and 7C conditions, and each battery was tested 5 times independently, and the results were plotted on Figure 1 In. By Figure 1 As can be seen from Table 1, the positive electrode modified by the atomic layer deposition method of the present invention has good cycle performance and rate performance.

[0067] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a positive electrode of a lithium ion battery, characterized in that: The steps include: (1) By atomic layer deposition, lithium hydroxide is first deposited on the surface of the positive electrode, and then zirconium oxide is further deposited; (2) Repeat step (1) 10 to 60 times to obtain a positive electrode with a surface coated with lithium zirconium oxide.

2. The method for preparing a positive electrode of a lithium ion battery according to claim 1, characterized in that: In step (1), the atomic layer deposition method is carried out under vacuum conditions; And / or, in step (1), the processing temperature of the atomic layer deposition method is 175°C to 225°C.

3. The method for preparing a positive electrode of a lithium ion battery according to claim 1, characterized in that: The lithium hydroxide deposition method comprises: introducing a lithium source and deionized water into an atomic layer deposition chamber for 1 second to 6 seconds.

4. The method for preparing a positive electrode of a lithium ion battery according to claim 3, characterized in that: The lithium source includes lithium tert-butoxide; And / or, the flow rate of the lithium source is 150 sccm to 200 sccm, and the flow rate of the deionized water is 150 sccm to 250 sccm.

5. The method for preparing a positive electrode of a lithium ion battery according to claim 1, characterized in that: The zirconium oxide deposition method comprises: introducing a zirconium source and deionized water into an atomic layer deposition chamber for 1 second to 6 seconds.

6. The method for preparing a positive electrode of a lithium ion battery according to claim 5, characterized in that: The zirconium source includes tetrakis(dimethylamino)zirconium; And / or, the flow rate of the zirconium source is 150 sccm to 200 sccm, and the flow rate of the deionized water is 150 sccm to 250 sccm.

7. The method for preparing a positive electrode of a lithium ion battery according to claim 1, characterized in that: Step (1) comprises the following steps: Passing a lithium source and deionized water into an atomic layer deposition chamber to deposit lithium hydroxide; passing a carrier gas into the atomic layer deposition chamber for 5s to 10s; passing a zirconium source and deionized water into the atomic layer deposition chamber to deposit zirconium oxide; and then passing a carrier gas into the atomic layer deposition chamber for 5s to 10s; Preferably, the carrier gas comprises at least one of helium, neon or argon.

8. A positive electrode for a lithium ion battery, characterized in that: The positive electrode of a lithium-ion battery is prepared by the method for preparing the positive electrode of a lithium-ion battery as claimed in any one of claims 1 to 7.

9. A lithium ion battery, characterized in that: Comprising the lithium-ion battery positive electrode as claimed in claim 8.

10. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 9.

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