A potassium-ion battery cathode material and its preparation method

Abstract

This invention proposes a potassium-ion battery cathode material and its preparation method, wherein the molecular formula of the potassium-ion battery cathode material is Na. x Co y A z O2, x, y, z are all atomic numbers, and A is a transition metal element; where 0.5≤x≤1, 0.6≤y≤0.9, and 0.1≤z≤0.4. A method for preparing a potassium-ion battery cathode material includes: (1) placing cobalt salt, manganese salt or nickel salt, sodium salt, and solvent in a ball mill jar for ball milling to obtain a viscous powder; (2) drying the viscous powder to obtain a mixed metal powder; and (3) sintering the material to obtain the cathode material. The potassium-ion battery cathode material provided by this invention can suppress multiple phase transitions during charging and discharging, reduce structural changes, and maintain electrochemical structural stability.

Description

Technical Field

[0001] This invention relates to the field of potassium-ion battery technology, and in particular to a potassium-ion battery cathode material and its preparation method. Background Technology

[0002] Among various potassium-ion battery cathode materials, layered metal oxides have attracted widespread attention due to their small molar mass and large interlayer spacing, which can provide two-dimensional alkali metal ion diffusion channels.

[0003] In related technologies, layered cobalt-based oxides provide capacity variations through the insertion / extraction of alkali metal ions between the layers during charge and discharge. However, the multiple phase transitions in cobalt-based materials during charge and discharge can lead to structural instability, and the interlayer spacing changes caused by the insertion and extraction of alkali metal ions can exacerbate structural changes.

[0004] Therefore, in order to address the above shortcomings, there is an urgent need for a potassium-ion battery cathode material that can maintain structural stability during electrochemical behavior. Summary of the Invention

[0005] In view of this, the present invention proposes a potassium-ion battery cathode material and its preparation method, which can provide a potassium-ion battery cathode material that maintains structural stability during electrochemical behavior.

[0006] The technical solution of this invention is achieved as follows: This invention provides a potassium-ion battery cathode material, wherein the molecular formula of the potassium-ion battery cathode material is Na. x Co y A z In O2, x, y, and z represent the number of atoms, and A represents a transition metal element.

[0007] Where 0.5≤x≤1, 0.6≤y≤0.9, and 0.1≤z≤0.4;

[0008] The transition metal element is selected from Mn and / or Ni.

[0009] Based on the above technical solutions, preferably, the molecular formula of the potassium-ion battery cathode material includes Na. 0.7 Co 0.75 Mn 0.25 O2, Na 0.7 Co 0.6 Mn 0.4 O2, Na 0.7 Co 0.75 Ni 0.25 O2, NaCo 0.75 Mn 0.25 O2, Na 0.5 Co 0.75 Mn 0.25 O2, Na0.7 Co 0.8 Mn 0.1 Ni 0.1 One of the components of O2.

[0010] According to another aspect of this application, this application provides a method for preparing the potassium-ion battery cathode material described above, the method comprising:

[0011] According to the required amount of raw materials in the molecular formula of potassium-ion battery cathode material, a mixture containing cobalt oxide, transition metal oxide, sodium salt, and solvent is ball-milled, dried, and sintered to obtain the potassium-ion battery cathode material.

[0012] Based on the above technical solutions, preferably, the cobalt oxide is cobalt tetroxide.

[0013] Based on the above technical solutions, preferably, the transition metal oxide includes manganese oxide and / or nickel oxide.

[0014] Based on the above technical solutions, preferably, the manganese oxide is selected from at least one of manganese trioxide and manganese dioxide.

[0015] Based on the above technical solutions, preferably, the nickel oxide is nickel oxide.

[0016] Based on the above technical solutions, preferably, the sodium salt is selected from at least one of sodium carbonate and sodium acetate.

[0017] Based on the above technical solutions, preferably, the solvent is selected from ethanol and / or acetone.

[0018] Based on the above technical solutions, preferably, the molar volume ratio of the sodium salt to the solvent is 0.05~0.15:1mmol / mL.

[0019] Based on the above technical solutions, preferably, the ball mill rotation speed is 300~600 rpm and the ball milling time is 8~12 hours.

[0020] Based on the above technical solutions, preferably, the rotational speed of the ball mill is independently selected from any value among 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, and 600rpm, or a range between any two of the above.

[0021] Based on the above technical solutions, preferably, the ball milling time is independently selected from any value of 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h or a range between any two of the above.

[0022] Based on the above technical solutions, preferably, during ball milling, the mass ratio of raw material to milling beads is 0.15~0.25.

[0023] Based on the above technical solutions, preferably, the diameter of the grinding balls is 0.3~10mm during ball milling.

[0024] Based on the above technical solutions, preferably, the drying temperature is 60~90℃ and the drying time is 8~16h.

[0025] Based on the above technical solutions, preferably, the drying temperature is independently selected from any value of 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or a range between any two of the above.

[0026] Based on the above technical solutions, preferably, the drying time is independently selected from any value of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h or a range between any two of the above.

[0027] Based on the above technical solutions, preferably, the sintering temperature is 700~900℃ and the sintering time is 10~15h.

[0028] Based on the above technical solutions, preferably, the sintering temperature is independently selected from any value of 700℃, 750℃, 800℃, 850℃, 900℃ or a range between any two of the above.

[0029] Based on the above technical solutions, preferably, the sintering time is independently selected from any value of 10h, 11h, 12h, 13h, 14h, 15h or a range between any two of the above.

[0030] As an optional implementation, this application is achieved through the following technical solution:

[0031] The method for preparing the potassium-ion battery cathode material of the present invention includes:

[0032] (1) Cobalt oxide, transition metal (manganese and / or nickel) oxide, sodium salt and solvent are placed in a ball mill jar and ball milled to obtain a viscous powder;

[0033] (2) The viscous powder is dried to obtain a mixed metal powder;

[0034] (3) The material is sintered to obtain a positive electrode material.

[0035] In the potassium-ion battery cathode material, the molar ratio of cobalt, transition metals (manganese and / or nickel) and sodium is (0.6~0.9):(0.1~0.4):(0.5~1).

[0036] The potassium-ion battery cathode material of the present invention has the following advantages over the prior art:

[0037] The potassium-ion battery cathode material prepared by this invention utilizes transition metal (manganese and / or nickel) doping of layered cobalt-based oxide cathode material. After the transition metal (manganese and / or nickel) replaces the cobalt sites, the doping of manganese and / or nickel can break the original ordered structure of interlayer alkali metal ions, resulting in a disordered structure of interlayer alkali metal ion vacancies. This structure can increase the diffusion path of potassium ions, suppress multiple phase transitions during the charging and discharging of potassium-ion batteries, reduce structural changes, thereby stabilizing the transition metal layer structure of the material, and further making the structure of the potassium-ion battery cathode material more stable. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The X-ray diffraction patterns of the products provided in Embodiment 1 and Comparative Example 1 of the present invention;

[0040] Figure 2 This is a SEM image of the product provided in Comparative Example 1 of this invention;

[0041] Figure 3 This is a SEM image of the product provided in Embodiment 1 of the present invention;

[0042] Figure 4 This is a TEM image of the product provided in Embodiment 1 of the present invention;

[0043] Figure 5 This is the X-ray photoelectron spectrum of the product provided in Comparative Example 1 of this invention;

[0044] Figure 6 This is the X-ray photoelectron spectrum of Co element in the product provided in Embodiment 1 of the present invention;

[0045] Figure 7 This is the Mn element X-ray photoelectron spectrum of the product provided in Embodiment 1 of the present invention;

[0046] Figure 8This is a cyclic comparison diagram of the products provided in Embodiments 1-5 and Comparative Example 1 of the present invention. Detailed Implementation

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0049] This invention provides a method for preparing a potassium-ion battery cathode material, comprising:

[0050] (1) Cobalt oxide, transition metal (manganese and / or nickel) oxide, sodium salt and solvent are placed in a ball mill jar and ball milled to obtain a viscous powder;

[0051] (2) The viscous powder is dried to obtain a mixed metal powder;

[0052] (3) The material is sintered to obtain a positive electrode material.

[0053] In this embodiment, the layered cobalt-based oxide cathode material is doped with transition metal (manganese or nickel) elements. After manganese replaces the cobalt active sites, it can suppress multiple phase transitions during the charging and discharging of potassium-ion battery cathode materials, reduce structural changes, and thus stabilize the transition metal layer structure of the material.

[0054] In this embodiment, manganese and / or nickel doping can break the original ordered structure of interlayer alkali metal ions and obtain an interlayer alkali metal ion vacancy disordered structure, which can increase the diffusion path of potassium ions.

[0055] In some embodiments of the present invention, the molar ratio of cobalt, transition metals (manganese and / or nickel) and sodium in the cathode material is (0.6~0.9):(0.1~0.4):(0.5~1).

[0056] In this embodiment, only when the molar ratio of cobalt, manganese, and sodium in the raw materials is (0.6~0.9):(0.1~0.4):(0.525~1.05) can a cathode material with a molar ratio of cobalt, manganese, and sodium of (0.6~0.9):(0.1~0.4):(0.5~1) be obtained; only when the molar ratio of cobalt, nickel, and sodium in the raw materials is (0.6~0.9):(0.1~0.4):(0.525~1.05) can a cobalt and nickel cathode material be obtained. A cathode material with a molar ratio of cobalt, manganese, nickel, and sodium of (0.6~0.9):(0.1~0.4):(0.5~1) can only be obtained when the molar ratio of cobalt, manganese, nickel, and sodium in the raw materials is (0.6~0.9):(0.1~0.4):(0.1~0.4):(0.525~1.05).

[0057] Within the above-mentioned range, the elemental molar ratio of the cathode material significantly improves the structural stability of the cathode material and increases the diffusion path of potassium ions.

[0058] In some embodiments of the present invention, the chemical formula of the positive electrode material includes Na. 0.7 Co 0.75 Mn 0.25 O2, Na 0.7 Co 0.6 Mn 0.4 O2, Na 0.7 Co 0.75 Ni 0.25 O2, NaCo 0.75 Mn 0.25 O2, Na 0.5 Co 0.75 Mn 0.25 O2, Na 0.7 Co 0.8 Mn 0.1 Ni 0.1 O2.

[0059] In this embodiment, the chemical formula of the positive electrode material includes Na. 0.7 Co 0.75 Mn 0.25 O2 enhances the structural stability of the cathode material and its effect on K. + The diffusion rate increases most significantly.

[0060] In some embodiments of the present invention, the cobalt oxide includes cobalt tetroxide, and the sodium salt includes sodium carbonate.

[0061] In this embodiment, the cobalt oxide includes cobalt tetroxide, the transition metal (manganese and / or nickel) oxide includes manganese trioxide or manganese dioxide or nickel oxide, and the sodium salt includes sodium carbonate or sodium acetate.

[0062] In some embodiments of the present invention, the solvent includes anhydrous ethanol.

[0063] In this embodiment, ethanol is chosen as the solvent. Of course, other solvents, such as acetone, can also be chosen, as long as they can provide lubrication and cooling and are easily volatile afterward.

[0064] In some embodiments of the present invention, in step (1), the ball milling time includes 8-12 hours (e.g., 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours).

[0065] In this embodiment, ball milling enables various oxides to be mixed evenly, while also resulting in smaller particle sizes.

[0066] In some embodiments of the present invention, in step (1), the ball milling speed includes 300-600 rpm. (For example, it may be 300 rpm, 400 rpm, 500 rpm or 600 rpm).

[0067] In this embodiment, the preferred rotational speed is 600 rpm.

[0068] In some embodiments of the present invention, in step (2), the drying time includes 8-16 hours. (For example, it can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or 16 hours).

[0069] In this embodiment, drying allows the solvent (such as anhydrous ethanol) in the material to evaporate, resulting in a dry oxide powder.

[0070] In some embodiments of the present invention, in step (3), the sintering temperature includes 700~900℃ and the holding time includes 10~15h.

[0071] In this embodiment, the preferred processing temperature is 801~900℃ (for example, it can be 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, or 900℃).

[0072] In this embodiment, sodium carbonate or sodium acetate can be decomposed at high temperature, allowing sodium ions to combine with oxides to form a positive electrode material, while the decomposed anions form water and carbon dioxide and are discharged.

[0073] To more clearly illustrate the technical solution and advantages of the present invention, the cathode material is described in detail below through embodiments.

[0074] Example 1

[0075] (1) 2.5 mmol cobalt tetroxide, 1.25 mmol manganese trioxide, 3.675 mmol sodium carbonate and 30 ml anhydrous ethanol were placed in a ball mill jar and ball milled at 600 rpm for 12 h. The diameter of the ball milling beads was 0.3-10 mm and the mass ratio of raw materials to ball milling beads was 0.2. After ball milling, a mixed viscous powder was obtained.

[0076] (2) The obtained viscous powder was dried in a forced-air drying oven for 12 hours at a temperature of 70°C to obtain a dried mixed powder;

[0077] (3) The material obtained in step (2) is placed in a tube furnace and calcined at 850°C for 12 hours with a heating rate of 5°C / min. -1 Thus, Na oxide is obtained. 0.7 Co 0.75 Mn 0.25 O2.

[0078] Comparative Example 1

[0079] Comparative Example 1 is basically the same as Example 1, except that in step (1), manganese trioxide was not added, and the resulting cathode material is Na. 0.7 CoO2.

[0080] Example 2

[0081] (1) Place 2 mmol of cobalt tetroxide, 2 mmol of manganese trioxide, 3.675 mmol of sodium carbonate and 30 ml of anhydrous ethanol in a ball mill jar and ball mill at 300 rpm for 8 hours. The diameter of the ball milling beads is 0.3-10 mm and the mass ratio of raw materials to ball milling beads is 0.25. After ball milling, a mixed viscous powder is obtained.

[0082] (2) The obtained viscous powder was dried in a forced-air drying oven for 16 hours at a temperature of 60°C to obtain a dried mixed powder;

[0083] (3) The material obtained in step (2) is placed in a tube furnace and calcined at 700℃ for 15 hours with a heating rate of 5℃ / min. -1 The resulting cathode material is Na. 0.7 Co 0.6 Mn 0.4 O2.

[0084] Example 3

[0085] (1) 2.5 mmol cobalt tetroxide, 2.5 mmol nickel oxide, 3.675 mmol sodium carbonate and 30 ml anhydrous ethanol were placed in a ball mill jar and ball milled at 600 rpm for 12 h. The diameter of the ball milling beads was 0.3-10 mm and the mass ratio of raw material to ball milling beads was 0.15. After ball milling, a mixed viscous powder was obtained.

[0086] (2) The obtained viscous powder was dried in a forced-air drying oven for 8 hours at a temperature of 90°C to obtain a dried mixed powder;

[0087] (3) Place the material obtained in step (2) into a tube furnace for calcination at 900℃ for 10 hours, with a heating rate of 5℃ / min. -1 The resulting cathode material is Na. 0.7 Co 0.75 Ni 0.25 O2.

[0088] Example 4

[0089] Example 4 is basically the same as Example 1, except that in step (1), 5.05 mmol of sodium carbonate is added, and the resulting positive electrode material is NaCo. 0.75 Mn 0.25 O2.

[0090] Example 5

[0091] Example 5 is basically the same as Example 1, except that in step (1), 2.625 mmol of sodium carbonate is added, and the resulting positive electrode material is Na. 0.5 Co 0.75 Mn 0.25 O2.

[0092] Example 6

[0093] Example 6 is basically the same as Example 1, except that in step (1), 2.67 mmol of cobalt tetroxide, 0.5 mmol of manganese trioxide, and 0.5 mmol of nickel oxide are added, and the resulting cathode material is Na. 0.7 Co 0.8 Mn 0.1 Ni 0.1 O2.

[0094] The embodiments and comparative examples were observed and tested to obtain... Figures 1 to 8 .according to Figure 1 It can be seen that Na without manganese doping 0.7 CoO2 has a P2-type structure, and after doping with manganese, Na... 0.7 Co 0.75 Mn 0.25 O2 materials transform into a P2 / P3 dual-phase structure. Figure 2 , Figure 3 The Na in Comparative Example 1 are shown respectively. 0.7 CoO2 and Na in Example 1 0.7 Co 0.75 Mn 0.25 SEM images of O2 show both materials as blocky, stacked layers, while Na... 0.7 The lamellar structure of CoO2 is more pronounced. Figure 4 Na in Example 1 is shown 0.7 Co 0.75 Mn 0.25 The TEM image of O2 shows that the interlayer spacing between two adjacent layers is 0.553 nm, which corresponds to the characteristic peak of the (002) crystal plane in the XRD card. Figure 5 This demonstrates Na in Comparative Example 1 0.7 The XPS plot of CoO2 shows that the Co valence state in the material is a mixture of +2 and +3 valence states. Figure 6 , 7 Na in Example 1 is shown 0.7 Co 0.75 Mn 0.25 The XPS plot of O2 shows that after doping, the proportion of +3 valence Co increases, the average valence state of Co increases, and the valence states of Mn are +3 and +4. Figure 8 The electrochemical performance of the examples and various comparative examples is shown, demonstrating that Na 0.7 Co 0.75 Mn 0.25 O2 has the highest capacity, which is due to its higher capacity compared to Na. 0.7 CoO2, the doping of manganese, widens the interlayer spacing of the material and increases the ion diffusion channels. However, when excessive manganese is doped, due to the influence of Mn... 3+ The Jahn-Teller effect it possesses, in Example 2, Na 0.7 Co 0.6 Mn 0.4 The electrochemical cycling diagram of O2 shows significant fluctuations, indicating insufficient stability. Nickel doping improves material stability, but the capacity remains low. This situation improves with manganese-nickel co-doping, resulting in increased capacity while maintaining relatively stable retention. This suggests that nickel contributes little to the capacity, and the improved stability after nickel or manganese-nickel doping stems from the increased structural stability due to entropy increase. When the sodium ion content changes, NaCo... 0.75 Mn 0.25 O2 and Na 0.5 Co 0.75 Mn 0.25 O2 retention is similar, but capacity is lower than Na. 0.7 Co 0.75 Mn 0.25 O2 is slightly low.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a potassium-ion battery cathode material, characterized in that, The preparation method includes: according to the required amount of raw materials in the molecular formula of potassium-ion battery cathode material, a mixture containing cobalt oxide, transition metal oxide, sodium salt and solvent is ball-milled, dried and sintered to obtain the potassium-ion battery cathode material; The cobalt oxide is cobalt tetroxide, the transition metal oxide is selected from at least one of manganese trioxide and manganese dioxide, the sodium salt is selected from at least one of sodium carbonate and sodium acetate, and the solvent is selected from ethanol and / or acetone. The molar volume ratio of the sodium salt to the solvent is 0.05~0.15:1 mmol / mL; The ball mill operates at a speed of 300-600 rpm for 8-12 hours. During ball milling, the mass ratio of raw material to milling beads is 0.15-0.25, and the diameter of the milling beads is 0.3-10 mm. The drying temperature is 60~90℃ and the time is 8~16h; The sintering process is carried out at a temperature of 700-900℃ for 10-15 hours. The molecular formula of the potassium-ion battery cathode material is Na. 0.7 Co 0.75 Mn 0.25 O2, the Na 0.7 Co 0.75 Mn 0.25 O2 has a P2 / P3 dual-phase structure, and the interlayer spacing between adjacent layers is measured to be 0.553 nm.

2. A potassium-ion battery cathode material, characterized in that, The potassium-ion battery cathode material prepared by the method of claim 1 has the molecular formula Na. 0.7 Co 0.75 Mn 0.25 O2, the Na 0.7 Co 0.75 Mn 0.25 O2 has a P2 / P3 dual-phase structure, and the interlayer spacing between adjacent layers is measured to be 0.553 nm.

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