Ruthenium-based chloride positive electrode active material and preparation method and application thereof

Abstract

The invention discloses a ruthenium-based chloride positive electrode active material as well as a preparation method and application thereof, and relates to the technical field of all-solid-state batteries. The chemical formula of the ruthenium-based chloride positive electrode active material is Li < 1 + x > RuOCl < 3 + x >, x is greater than or equal to 0 and less than or equal to 3, and the ruthenium-based chloride positive electrode active material has the initial specific discharge capacity of 70mAh / g at 0.1 C, and meanwhile, compared with a traditional oxide positive electrode active material, Li < 1 + x > RuOCl < 3 + x > has relatively high ionic conductivity. The ruthenium-based chloride positive electrode active material provided by the invention can avoid the use of a solid electrolyte without electrochemical activity, improves the energy density and rate capability of a solid-state lithium ion battery, and has a relatively good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of all-solid-state batteries, in particular to a ruthenium-based chloride positive electrode active material and a preparation method and application thereof. BACKGROUND

[0002] All-solid-state lithium ion batteries are one of the important technical routes of the next generation of batteries, with the characteristics of high safety and high energy density, and are considered to be the most promising power source.

[0003] The positive electrode material, as one of the core components of the all-solid-state battery, plays a key role in the electrochemical performance of the all-solid-state battery to a certain extent. Although the traditional oxide positive electrode active materials such as ternary and lithium cobaltate have high energy density, the ion conductivity is poor, which makes it necessary to add 30wt.% of solid-state electrolyte in the positive electrode. Since the inactive solid-state electrolyte cannot provide capacity, the overall energy density of the positive electrode material is reduced. In addition, poor ion conductivity will limit the performance of the positive electrode at higher power. At higher power, the positive electrode particles of the oxide positive electrode material with poor ion conductivity cannot absorb or supplement lithium ions in time, which will cause the formation of adverse potential difference, resulting in additional energy loss. The positive electrode material with high ion conductivity can effectively weaken or inhibit the formation of this potential difference and reduce energy loss.

[0004] Therefore, the research and development of new positive electrode materials with high ion conductivity can improve the energy utilization rate of the positive electrode material in the all-solid-state battery at higher power. In the alternative, it can also replace the inactive solid-state electrolyte in the positive electrode to improve the overall energy density of the positive electrode material. SUMMARY In view of the problems in the prior art, the present application provides a ruthenium-based chloride positive electrode active material and a preparation method and application thereof, aiming to solve the problems of poor ion conductivity of the existing positive electrode active material, the need to use inactive solid-state electrolyte, and the resulting reduction in the overall energy density of the positive electrode material; and the problem of low energy utilization rate of the positive electrode active material with poor ion conductivity at higher power.

[0005] The technical scheme of the present application is as follows: In a first aspect of the present application, a ruthenium-based chloride positive electrode active material is provided, wherein the ruthenium-based chloride positive electrode active material has a chemical formula of Li 1+x RuOCl 3+x , wherein 0≤x≤3.

[0006] Further, the ruthenium-based chloride positive electrode active material is at least one of LiRuOCl3 and Li3RuOCl5.

[0007] In a second aspect, the present application provides a method for preparing a ruthenium-based chloride positive electrode active material, comprising the following steps: mixing ruthenium oxychloride with lithium chloride or lithium chloride hydrate to obtain a mixture; ball-milling the mixture to obtain the ruthenium-based chloride positive electrode active material.

[0008] Further, when lithium chloride hydrate is used, the method further comprises a step of dehydrating the lithium chloride hydrate before ball-milling.

[0009] Further, the lithium chloride hydrate is dehydrated under vacuum at 100-200℃.

[0010] Further, the ruthenium oxychloride is mixed with lithium chloride or dehydrated lithium chloride hydrate under inert atmosphere at a molar ratio of Li:Ru of (1-4):1.

[0011] Further, the ball-milling is performed under inert atmosphere at a rotation speed of 400-600 rpm for 20-30 hours.

[0012] In a third aspect, the present application provides an all-solid-state battery, comprising a positive electrode, a negative electrode and a solid-state electrolyte between the positive electrode and the negative electrode, wherein the positive electrode comprises the ruthenium-based chloride positive electrode active material of the present application.

[0013] Further, the positive electrode further comprises a conductive agent, and the mass ratio of the ruthenium-based chloride positive electrode active material to the conductive agent is (10-95):5.

[0014] Further, the conductive agent comprises at least one of Surpe-P (conductive carbon black), acetylene black, KS-6 (graphite conductive agent), CNT (carbon nanotube), graphene and VGCF (vapor-grown carbon fiber). Preferably, the conductive agent is VGCF.

[0015] Further, the negative electrode is one of a lithium metal negative electrode and a lithium alloy negative electrode.

[0016] Further, the solid-state electrolyte comprises one of Li3InCl6, Li2ZrCl6, Li 1.6 ZrO 0.8 Cl4, LiNbOCl4, LiTaOCl4, Li2TaOCl5, Li6PS5Cl, Li 5.4 PS 4.4 Cl 1.6 .

[0017] The present application has the following advantages: (1) The Li1+x RuOCl 3+x The positive electrode active material has high ionic conductivity, which can avoid the addition of inactive solid electrolyte and effectively improve the energy density of all-solid-state batteries.

[0018] (2) The Li of the present invention 1+x RuOCl 3+x The positive electrode active material has a high bulk and interfacial ion transport rate, which is beneficial to improving the rate performance of all-solid-state batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0020] Figure 1 The following are SEM and EDS images of Li3RuOCl5. (a) has a scale bar of 100 μm, (b) has a scale bar of 20 μm, (c) has a scale bar of 100 μm, and (d) is an EDS image.

[0021] Figure 2 The XRD patterns of the raw materials are shown.

[0022] Figure 3 EIS impedance spectra of LiRuOCl3, Li3RuOCl5, and LiCoO2.

[0023] Figure 4 The charge-discharge curves of LiRuOCl3 and Li3RuOCl5 at 0.05C in the voltage range of 2.4~3.7V are shown.

[0024] Figure 5 The charge-discharge curves of Li3RuOCl5 and LiCoO2 at 0.1C in the voltage range of 2.4~3.7V are shown. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the protection scope of this invention. Where there is no conflict, the following embodiments and features can be combined with each other.

[0026] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and the like cited in the present specification are only for the convenience of clear description, and are not intended to limit the scope of the embodiments, and the change or adjustment of the relative relationship is also considered as the scope of the embodiments of the present application without substantial change of the technical content. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the present application belongs.

[0027] The embodiments of the present application provide a ruthenium-based chloride positive electrode active material, wherein the ruthenium-based chloride positive electrode active material has a chemical formula of Li 1+x RuOCl 3+x , wherein 0≤x≤3, such as x being 0, 1, 2, 3, etc.

[0028] As an example, the ruthenium-based chloride positive electrode active material is at least one of LiRuOCl3 and Li3RuOCl5.

[0029] The Li 1+x RuOCl 3+x The positive electrode active material has a high ionic conductivity, which can avoid the addition of inactive solid-state electrolyte, and effectively improve the energy density of the full solid-state battery. The Li 1+x RuOCl 3+x The positive electrode active material has a high bulk and interface ion transport rate, which is beneficial to improve the rate performance of the full solid-state battery.

[0030] The embodiments of the present application provide a preparation method of the ruthenium-based chloride positive electrode active material as described above, wherein the method comprises the following steps: Mixing ruthenium oxychloride and lithium chloride or lithium chloride hydrate to obtain a mixture; Ball milling the mixture to obtain the ruthenium-based chloride positive electrode active material.

[0031] In the embodiments, the ruthenium-based chloride positive electrode active material is synthesized by ball milling of ruthenium oxychloride and lithium chloride or its hydrate. The synthesized material as a whole presents a spherical shape, and has a special morphology on a single particle, has a large specific surface area, and is beneficial to the embedding and extraction of lithium ions.

[0032] In one embodiment, when lithium chloride hydrate is used, the method further comprises a step of dehydrating the lithium chloride hydrate before ball milling.

[0033] In one embodiment, the lithium chloride hydrate is dehydrated under vacuum conditions at 100-200°C (such as 150°C).

[0034] That is, when lithium chloride hydrate is used, it is subjected to a dehydration treatment under vacuum at 100-200°C; when lithium chloride is used, it is used directly.

[0035] In one embodiment, under an inert atmosphere, the ruthenium oxychloride is mixed with lithium chloride or the lithium chloride hydrate subjected to a dehydration treatment at a molar ratio of Li:Ru = (1-4):1.

[0036] In one embodiment, the conditions of the ball milling treatment include: under an inert atmosphere, the ball milling speed is 400-600 rpm (such as 500 rpm), and the ball milling time is 20-30 h (such as 24 h).

[0037] Specifically, under an inert atmosphere, the mixture is added to a ball milling tank, and ball milling is performed at a speed of 500 rpm for 20-30 h to obtain the ruthenium-based chloride positive electrode active material.

[0038] The embodiments of the present application provide a full solid-state battery, which comprises a positive electrode, a negative electrode, and a solid-state electrolyte between the positive electrode and the negative electrode, wherein the positive electrode comprises the ruthenium-based chloride positive electrode active material according to the embodiments of the present application.

[0039] In one embodiment, the positive electrode further comprises a conductive agent, and the mass ratio of the ruthenium-based chloride positive electrode active material to the conductive agent is (10-95):5, such as 10:5, 20:5, 50:5, 80:5, 95:5, etc.

[0040] In one embodiment, the conductive agent comprises at least one of Surpe-P (conductive carbon black), acetylene black, KS-6 (graphite conductive agent), CNT (carbon nanotube), graphene, and VGCF (vapor phase growth carbon fiber). Preferably, the conductive agent is VGCF.

[0041] In one embodiment, the negative electrode is one of a lithium metal negative electrode and a lithium alloy negative electrode.

[0042] In one embodiment, the solid-state electrolyte comprises one of Li3InCl6, Li2ZrCl6, Li 1.6 ZrO 0.8 Cl4, LiNbOCl4, LiTaOCl4, Li2TaOCl5, Li6PS5Cl, Li 5.4 PS 4.4 Cl 1.6 .

[0043] The application will be described in detail below with reference to the embodiments, but the embodiments of the application are not limited thereto. It is obvious that the embodiments described below are only some of the embodiments of the application, and other similar embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0044] Example 1 The following specific operation steps are used to prepare the LiRuOCl3 positive electrode active material, and assemble a full solid-state battery to test its performance.

[0045] Preparation of LiRuOCl3 positive electrode active material: S1: Under an argon atmosphere, LiCl and RuOCl2 are weighed according to a molar ratio of Li:Ru = 1:1.

[0046] S2: Under an argon atmosphere, the weighed raw materials are poured into a ball mill tank and sealed with adhesive tape. Ball milling is performed at a speed of 500 rpm for 24 h to obtain the LiRuOCl3 positive electrode active material.

[0047] Preparation of full solid-state battery positive electrode: S1: Under an argon atmosphere, the positive electrode active material LiRuOCl3 and the conductive agent VGCF are weighed according to a mass ratio of positive electrode active material: conductive agent = 95:5.

[0048] S2: The weighed materials are poured into a mortar and ground for 10 min to obtain the full solid-state battery positive electrode.

[0049] Full solid-state battery assembly: S1: 100 mg of Li2TaOCl5 solid-state electrolyte (in powder form) is weighed and poured into a tablet press mold. The powder solid-state electrolyte is pressed into an electrolyte sheet under a pressure of 400 MPa for 2 min.

[0050] S2: 50 mg of Li 5.4 PS 4.4 Cl 1.6 solid-state electrolyte (in powder form) is poured into a tablet press mold and pressed into a sheet under a pressure of 500 MPa for 2 min.

[0051] S3: The full solid-state battery positive electrode is uniformly sprinkled on the other side of the Li2TaOCl5 electrolyte sheet, and is pressed under a pressure of 600 MPa for 2 min.

[0052] S4: A piece of lithium-indium alloy sheet is added to one side of the Li 5.4 PS 4.4 Cl 1.6 solid-state electrolyte sheet.

[0053] A full solid-state battery was assembled in a glove box according to the above procedure. The voltage window for the charge-discharge cycle was selected to be 2.4-3.7 V.

[0054] Example 2 This example provides the preparation of Li3RuOCl5 cathode active material and the assembly of a full solid-state battery. The difference between this example 2 and example 1 is that LiCl and RuOCl2 were weighed according to the molar ratio of Li:Ru = 3:1. Other raw materials, materials and preparation process are the same as example 1.

[0055] Comparative Example 1 The difference between this example and the above example 1 is that the finished LiCoO2 is used as the cathode active material. That is, there is no need to prepare the cathode active material, but the cathode active material is completely replaced by LiCoO2, and other raw materials, materials and preparation process are the same as the above example 1. Material characterization and performance test: (1) Material characterization test The SEM and EDS images of Li3RuOCl5 of example 2 are shown in Figure 1 . The overall presents a spherical shape, while the individual particles are covered with ravines, with a large specific surface area, which is beneficial to the insertion and extraction of lithium ions.

[0056] The XRD spectra of LiRuOCl3 of example 1 and Li3RuOCl5 of example 2 are shown in Figure 2 . Compared with the spectrum of the raw material RuOCl2, it can be seen that example 1 and example 2 do not contain the residue of the raw material RuOCl2, which indicates the successful synthesis of the material. Although the XRD spectra of example 1 and example 2 indicate that the material has a more obvious LiCl spectrum, referring to the EDS spectrum in Figure 1 , the elements of Ru and Cl in the material are uniformly distributed, which can indicate that there is no LiCl precipitation.

[0057] (2) Ion conductivity test 100 mg of the ruthenium-based chloride obtained in examples 1 and 2 were respectively placed in a tablet press mold and pressed for 1 min under a pressure of 240 MPa to obtain LiRuOCl3 tablets and Li3RuOCl5 tablets, respectively. The above obtained LiRuOCl3 tablets and Li3RuOCl5 tablets were respectively assembled into a pressure cell (both the positive electrode and the negative electrode were carbon-coated aluminum foil, and the electrolyte was the tablet material), then the assembled pressure cell was loaded into a pressure cell test mold, and the assembled pressure cell was subjected to EIS test, the test temperature was 25℃, and the test pressure was 240 MPa.

[0058] Take 200 mg of LiCoO2 in Comparative Example 1, place it in a tablet press mold, press for 1 min under a pressure of 240 MPa, and evenly sprinkle 100 mg of Li 1.6 ZrO 0.8 Cl4 solid electrolyte powder. Press for 1 min under a pressure of 240 MPa again, and assemble the pressed material into a pressure battery (both the positive electrode and the negative electrode are carbon-coated aluminum foil, and the electrolyte is the tablet material), then place the assembled pressure battery into a pressure battery test mold, and perform EIS testing on the assembled pressure battery, with a test temperature of 25°C and a test pressure of 240 MPa.

[0059] The impedance diagrams of Example 1 (LiRuOCl3), Example 2 (Li3RuOCl5), and Comparative Example 1 (LiCoO2) are shown in FIG. 1, and the test results of ionic conductivity are shown in Table 1. Figure 3

[0060] Table 1

[0061] From Table 1 and Figure 3 it can be seen that LiRuOCl3 and Li3RuOCl5 both have higher ionic conductivity than LiCoO2, and Li3RuOCl5 has higher ionic conductivity than LiRuOCl3.

[0062] (3) Positive electrode performance test The full solid-state batteries of Examples 1 and 2 were subjected to charge-discharge testing at a rate of 0.05C, and the test results are shown in FIG. 2. The full solid-state batteries of Example 2 and Comparative Example 1 were subjected to charge-discharge testing at a rate of 0.1C, and the test results are shown in FIG. 3. Figure 4 Figure 5

[0063] From Figure 4 it can be seen that Li3RuOCl5 has higher ionic conductivity and higher specific capacity at the same charge-discharge rate.

[0064] Figure 5 The charge-discharge curves of Li3RuOCl5 and LiCoO2 at a rate of 0.1C are shown in FIG. 4, and a comparison of the two shows that the discharge specific capacity of Li3RuOCl5 is much higher than that of LiCoO2. This can indicate that when only a conductive agent is added to the positive electrode active material, the ruthenium-based chloride positive electrode active material benefits from its high ionic conductivity and can perform better at a higher rate than LiCoO2 (a traditional positive electrode active material).

[0065] ​​​In summary, the ruthenium-based chloride positive electrode active material of the present application can avoid the addition of inactive solid-state electrolyte, improve the energy density of the battery, and at the same time has a higher ionic conductivity, so that the material has better rate performance.

[0066] Finally, it should be understood that the application of the present application is not limited to the above examples, and those of ordinary skill in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A ruthenium-based chloride cathode active material, characterized in that, The ruthenium-based chloride positive electrode active material has the chemical formula Li. 1+x RuOCl 3+x , where 0≤x≤3.

2. The ruthenium-based chloride positive electrode active material according to claim 1, characterized in that, The ruthenium chloride positive electrode active material is at least one of LiRuOCl3 and Li3RuOCl5.

3. A method for preparing the ruthenium-based chloride positive electrode active material according to any one of claims 1-2, characterized in that, Includes the following steps: Ruthenium dichloride was mixed with lithium chloride or lithium chloride hydrate to obtain a mixture; The mixture was ball-milled to obtain the ruthenium chloride positive electrode active material.

4. The method for preparing the ruthenium-based chloride positive electrode active material according to claim 3, characterized in that, When lithium chloride hydrate is used, the process further includes a step of dehydrating the lithium chloride hydrate before ball milling.

5. The method for preparing the ruthenium-based chloride positive electrode active material according to claim 4, characterized in that, The lithium chloride hydrate was dehydrated under vacuum conditions at 100~200°C.

6. The method for preparing the ruthenium-based chloride positive electrode active material according to claim 3, characterized in that, Ruthenium dichloride was mixed with lithium chloride or dehydrated lithium chloride hydrate in an inert atmosphere at a molar ratio of Li:Ru = (1~4):

1.

7. The method for preparing the ruthenium-based chloride positive electrode active material according to claim 3, characterized in that, The conditions for ball milling include: under an inert atmosphere, a ball milling speed of 400-600 rpm, and a ball milling time of 20-30 h.

8. An all-solid-state battery, comprising a positive electrode, a negative electrode, and a solid electrolyte between the positive and negative electrodes, characterized in that, The positive electrode comprises the ruthenium chloride positive electrode active material according to any one of claims 1-2.

9. The all-solid-state battery according to claim 8, characterized in that, The positive electrode also includes a conductive agent, and the mass ratio of the ruthenium chloride positive electrode active material to the conductive agent is (10~95):5; The conductive agent includes at least one of conductive carbon black, acetylene black, graphite conductive agent, carbon nanotubes, graphene, and vapor-grown carbon fibers.

10. The all-solid-state battery according to claim 8, characterized in that, The negative electrode is one of lithium metal negative electrode and lithium alloy negative electrode, and the solid electrolyte includes Li3InCl6, Li2ZrCl6, and Li 1.6 ZrO 0.8 Cl4, LiNbOCl4, LiTaOCl4, Li2TaOCl5, Li6PS5Cl, Li 5.4 PS 4.4 Cl 1.6 One of them.

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