Modified cobalt-free lithium-rich manganese-based precursor and preparation method therefor

Abstract

Disclosed in the present application is a preparation method for a modified cobalt-free lithium-rich manganese-based precursor. The prepared modified cobalt-free lithium-rich manganese-based precursor can effectively reduce a large number of manganese-series oxides, which are attached to the middle and surface of primary particles, such that the primary particles are uniform and compact; in addition, the specific surface area of the precursor reaches 40-80 m2 / g, and the tap density is greater than 1.3 g / cm3. The precursor prepared by selecting the method of the present application, which involves flowing an oxidant solution and a reducing agent solution into a reaction system in parallel, has the characteristics of being low cost and being environmentally friendly and pollution-free; in addition, a conventional protection method of introducing an inert gas, such as nitrogen, is replaced, thereby effectively reducing the safety risk of the reaction system due to a high pressure. In conclusion, the cobalt-free lithium-rich manganese-based precursor prepared by using the method can not only ensure various indexes and good morphology, but can also reduce the manufacturing cost and is consistent with the green sustainable development concept.

Description

A modified cobalt-free lithium-rich manganese-based precursor and its preparation method

[0001] This application claims priority to Chinese patent application No. 202311455129.7, filed on November 3, 2023. This application incorporates the entire text of the aforementioned Chinese patent application. Technical Field

[0002] The present application belongs to the field of lithium-ion battery positive electrode materials, and specifically relates to a modified cobalt-free lithium-rich manganese-based precursor and a preparation method thereof. Background Art

[0003] In recent years, the demand for rechargeable batteries in the fields of electronic digital devices (mobile phones, laptops, etc.), power tools (electric vehicles, drones, etc.), electric vehicles (EV, HEV, etc.) has been increasing. Lithium-ion batteries have very broad demand prospects and application areas in today's market, and the positive electrode materials that affect the electrical properties of lithium-ion batteries are also attracting more and more attention.

[0004] Currently, nickel-cobalt-manganese ternary cathode materials are being extensively researched and applied due to their high energy density, relatively stable cycle performance and cycle life, and high rate capability. However, due to the continuous rise in cobalt prices in recent years, resulting in increased production costs, more and more precursor cathode materials are being switched from nickel-cobalt-manganese ternary to nickel-manganese ternary. At the same time, nickel-manganese ternary precursor cathode materials are considered to be one of the most competitive cathode materials in the future market.

[0005] However, in the process of using the co-precipitation method to prepare nickel-manganese binary precursors, a large number of difficult-to-solve problems have also emerged. The most obvious problem is that the precursors produced, whether large or small particles, have uneven manganese co-precipitation. A large amount of manganese oxides will adhere to the middle and surface of the primary particles, and the maximum specific surface area is only 10-30m 2 / g, which affects the various indicators and morphology of the precursor, and also affects the rate performance of the precursor positive electrode material.

[0006] Summary of the Invention

[0007] Based on the above problems, this application focuses on providing a method to effectively solve the problem of uneven manganese co-precipitation in the production of nickel-manganese binary precursors, and uses oxidant solution and reducing agent solution to replace inert gases such as nitrogen to act as protection, while increasing the specific surface area of ​​the manganese-rich precursor, making the primary particles refined and uniform.

[0008] To achieve the above objectives, the technical solution adopted in this application is a method for preparing a modified cobalt-free lithium-rich manganese-based precursor, comprising the following steps:

[0009] 1) preparing a nickel-manganese mixed salt solution, an oxidant solution, and a reducing agent solution; the nickel-manganese mixed salt solution has a concentration of 1.0-3.0 mol / L and is prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate; the oxidant solution has a temperature of 30-50° C. and a concentration of 0.02-0.1 g / L and is prepared from one or more of potassium permanganate, perchloric acid, hypochlorous acid, hydrogen peroxide, sodium hypochlorite, potassium persulfate, sodium persulfate, and ammonium persulfate; the reducing agent solution has a temperature of 30-50° C. and a concentration of 0.02-0.2 g / L and is prepared from one or more of sodium thiosulfate, vitamin C, sodium D-isoascorbate, oxalic acid, potassium borohydride, sodium borohydride, and ethanol;

[0010] 2) preparing a mixed solution of alkali solution, complexing agent solution and water in a volume ratio of (0.2-0.4): (0.1-0.25): (40-70) and placing the mixed solution in a reaction kettle as a reaction base liquid;

[0011] 3) adding a nickel-manganese mixed salt solution, an oxidant solution, a reducing agent solution, an alkaline solution, and a complexing agent solution in a volume ratio of (30-100): (0.1-3): (0.2-5): (15-55): (2-10) to a reaction kettle, controlling the pH at 10-13 and the temperature at 30-80° C. to form a reaction slurry;

[0012] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor.

[0013] Preferably, the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution in step 1) is (20-50):(50-80); preferably, the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (35-45):(65-65).

[0014] Preferably, in step 1), the concentration of the nickel-manganese mixed salt solution is 2.5-2.7 mol / L, the concentration of the oxidant solution is 0.02-0.05 g / L, and the concentration of the reducing agent solution is 0.1-0.2 g / L.

[0015] Preferably, in step 2), a mixed solution of alkaline solution, complexing agent solution and water in a volume ratio of (0.35-0.4): (0.15-0.25): (50-70) is prepared and placed in a reaction kettle as a reaction base liquid; preferably, the concentration of the alkaline solution is 0.3-0.7 g / L, and the concentration of the complexing agent solution is 1-1.5 g / L.

[0016] Preferably, in step 3), the nickel-manganese mixed salt solution, the oxidant solution, the reducing agent solution, the alkaline solution, and the complexing agent solution are simultaneously flowed into the reactor in a volume ratio of (80-100): (2-3): (4.5-5): (45-55): (6-9).

[0017] Preferably, in step 3), the pH is controlled at 10.9-11.9 and the temperature is controlled at 50-60° C. to form a reaction slurry.

[0018] Preferably, the rotation speed of the reactor in step 3) is 200-1000 r / min; preferably, the rotation speed of the reactor is 600-1000 r / min.

[0019] Preferably, the alkaline solution is one or more of sodium hydroxide and potassium hydroxide solutions, and the complexing agent solution is one or more of ammonia, urea, EDTA, ethylenediamine, and citric acid solutions; the concentration of the alkaline solution is 0.2-5 g / L, and the concentration of the complexing agent solution is 0.2-20 g / L;

[0020] The modified cobalt-free lithium-rich manganese-based precursor prepared in this application has a D50 of 5-20 μm, and the primary particles are short and thin strips and evenly distributed, and its tap density is greater than 1.3 g / cm 3 , with a specific surface area of ​​40-80m 2 / g.

[0021] Preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is not less than 1.95 g / cm 3 , with a specific surface area of ​​65-80m 2 / g; More preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is 1.95-2.1g / cm 3 , with a specific surface area of ​​65-75m 2 / g.

[0022] Preferably, the modified cobalt-free lithium-rich manganese-based precursor is in the shape of short thin strips with an aspect ratio of (5 to 13):1.

[0023] Traditional manganese-rich precursors have uneven manganese co-precipitation. A large amount of manganese oxides will adhere to the middle and surface of the primary particles, which seriously affects the various indicators and morphology of the precursor. At the same time, it also has a great impact on the various electrical properties of the precursor's positive electrode material, and may even pose a safety hazard.

[0024] Compared with the prior art, the beneficial effect of the present invention is that the modified cobalt-free lithium-rich manganese-based precursor prepared by the present invention can effectively reduce a large amount of manganese oxides attached to the middle and surface of the primary particles, making the primary particles uniform and dense. At the same time, the specific surface area of ​​the precursor reaches 40-80m 2 / g, tap density greater than 1.3g / cm3 . The precursor prepared by the method of introducing the oxidant solution and the reducing agent solution into the reaction system in parallel in this application has the characteristics of low cost, environmental protection and no pollution. At the same time, it replaces the conventional protection method of introducing inert gas such as nitrogen, and effectively reduces the safety risk of the reaction system due to high pressure. In summary, the cobalt-free lithium-rich manganese-based precursor prepared by this method can not only ensure excellent various indicators and morphology, but also reduce the production cost, which is in line with the concept of green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0026] FIG1 is a SEM image of the precursor prepared in Example 1;

[0027] FIG2 is a SEM image of the precursor obtained in Example 2;

[0028] FIG3 is a SEM image of the precursor obtained in Example 3;

[0029] FIG4 is a SEM image of the precursor prepared in Comparative Example 1. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] Unless otherwise specified, the materials involved in this application can be prepared by conventional methods in the art or purchased conveniently from the market.

[0032] Unless otherwise specified, the "solution" mentioned in this application refers to an aqueous solution.

[0033] As described in the background technology of this application, there is a problem of uneven manganese co-precipitation in the production of nickel-manganese binary precursors in the prior art. In order to solve the above problems, in a typical embodiment of the present application, a method for preparing a modified cobalt-free lithium-rich manganese-based precursor is provided, comprising the following steps: 1) preparing a nickel-manganese mixed salt solution, an oxidant solution, and a reducing agent solution; the concentration of the nickel-manganese mixed salt solution is 1.0-3.0 mol / L, and it is prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate; the temperature of the oxidant solution is 30-50°C, the concentration is 0.02-0.1 g / L, and it is prepared from one or more of potassium permanganate, perchloric acid, hypochlorous acid, hydrogen peroxide, sodium hypochlorite, potassium persulfate, sodium persulfate, and ammonium persulfate; the temperature of the reducing agent solution is 30-50°C, the concentration is 0.02-0.1 g / L, and it is prepared from one or more of potassium permanganate, perchloric acid, hypochlorous acid, hydrogen peroxide, sodium hypochlorite, potassium persulfate, sodium persulfate, and ammonium persulfate; the temperature of the reducing agent solution is 30-50°C. ℃, with a concentration of 0.02-0.2 g / L, prepared from one or more of sodium thiosulfate, vitamin C, sodium D-isoascorbate, oxalic acid, potassium borohydride, sodium borohydride, and ethanol; 2) preparing a mixed solution of an alkali solution, a complexing agent solution, and water in a volume ratio of (0.2-0.4):(0.1-0.25):(40-70) and placing it in a reaction kettle as a reaction base liquid; the alkali solution is one or more of sodium hydroxide and potassium hydroxide solutions, and the complexing agent solution is one or more of ammonia water, urea, EDTA, ethylenediamine, and citric acid solutions; the concentration of the alkali solution is 0.2-5 g / L, and the concentration of the complexing agent solution is 0.2-20 g / L; 3) A nickel-manganese mixed salt solution, an oxidant solution, a reducing agent solution, an alkaline solution, and a complexing agent solution are added to a reaction kettle in a volume ratio of (30-100): (0.1-3): (0.2-5): (15-55): (2-10), and the pH is controlled at 10-13 and the temperature is 30-80° C. to form a reaction slurry; 4) after the reaction is completed, the reaction slurry is aged, and then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor.

[0034] The present application first prepares a nickel-manganese mixed salt solution, an oxidant solution, and a reducing agent solution, and at the same time, prepares an alkaline solution, a complexing agent solution, and water into a mixed solution and places it in a reactor as a reaction bottom liquid. Then, the nickel-manganese mixed salt solution, the oxidant solution, the reducing agent solution, the alkaline solution, and the complexing agent solution are added to the reactor in a specific volume ratio and flowed into the reactor, and the pH and temperature are controlled to react. In this process, a reaction slurry is formed through a complexation reaction, a precipitation reaction, and an oxidation-reduction reaction. Finally, the reaction slurry is aged, centrifuged, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor.

[0035] The present application introduces an oxidant solution and a reducing agent solution into the reaction system in parallel. The oxidant refines and uniformly oxidizes the primary particles of the precursor, and the reducing agent causes the over-refined primary particles to be affected by reduction and become excellent and uniform primary particles again. The prepared modified cobalt-free lithium-rich manganese-based precursor can effectively reduce a large amount of manganese oxides attached to the middle and surface of the primary particles, making the primary particles uniform and dense, and increasing the specific surface area and tap density. The use of oxidant and reducing agent in parallel replaces conventional protection methods such as the introduction of inert gases such as nitrogen, effectively reducing the safety risks of the reaction system due to high pressure, and is low in cost and has little environmental pollution.

[0036] In a preferred embodiment, in step 1), the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (20-50):(50-80); preferably, the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (35-45):(65-65). The above conditions can further improve the particle morphology and performance.

[0037] In order to further balance costs and product indicators, in a preferred embodiment, in step 1), the concentration of the nickel-manganese mixed salt solution is 2.5-2.7 mol / L, the concentration of the oxidant solution is 0.02-0.05 g / L, and the concentration of the reducing agent solution is 0.1-0.2 g / L.

[0038] In a preferred embodiment, in step 2), a mixture of an alkaline solution, a complexing agent solution, and water in a volume ratio of (0.35-0.4):(0.15-0.25):(50-70) is placed in a reaction vessel as the reaction base solution. Preferably, the concentration of the alkaline solution is 0.3-0.7 g / L, and the concentration of the complexing agent solution is 1-1.5 g / L. Under these conditions, the primary particles are more uniform and the aspect ratio is easier to control.

[0039] In order to more fully eliminate manganese oxides on the surface of primary particles, control the aspect ratio, and further achieve high tap density and specific surface area, in a preferred embodiment, in step 3), the nickel-manganese mixed salt solution, oxidant solution, reducing agent solution, alkaline solution, and complexing agent solution are added to the reactor in a volume ratio of (80-100): (2-3): (4.5-5): (45-55): (6-9).

[0040] In a preferred embodiment, in step 3), the pH is controlled at 10.9-11.9 and the temperature is controlled at 50-60° C. to form a reaction slurry. Under these conditions, the reaction conditions are easier to control, and it is easier to simultaneously achieve a high tap density and specific surface area, and the manganese oxide on the surface of the primary particles is further reduced.

[0041] Based on similar reasons, in a preferred embodiment, in step 3), the rotation speed of the reactor is 200-1000 r / min; preferably, the rotation speed of the reactor is 600-1000 r / min.

[0042] In another typical embodiment of the present application, a modified cobalt-free lithium-rich manganese-based precursor is also provided, which is prepared using the above-mentioned preparation method of the present application. Due to the use of the preparation method of the present application, the manganese series oxides attached to the middle and surface of the primary particles are reduced, and it has a significantly increased specific surface area and tap density, and has low safety risks, low costs, and little environmental pollution.

[0043] Specifically, in a preferred embodiment, the D50 of the modified cobalt-free lithium-rich manganese-based precursor is 5-20 μm, and the tap density is greater than 1.3 g / cm 3 , with a specific surface area of ​​40-80m 2 / g; preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is not less than 1.95g / cm 3 , with a specific surface area of ​​65-80m 2 / g; More preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is 1.95-2.1g / cm 3 , with a specific surface area of ​​65-75m 2 / g.

[0044] In addition, due to the simultaneous introduction of the oxidant and the reducing agent, in a preferred embodiment, the modified cobalt-free lithium-rich manganese-based precursor is in the form of short and thin strips with an aspect ratio of (5 to 13):1.

[0045] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0046] Example 1

[0047] 1) Prepare a 2.5 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a molar ratio of nickel to manganese of 35:65; prepare a 0.03 g / L potassium persulfate solution at 40°C and a 0.10 g / L sodium thiosulfate solution at 40°C;

[0048] 2) A mixture of 0.3 g / L sodium hydroxide solution, 1 g / L urea solution, and pure water at a volume ratio of 0.35:0.15:50 was prepared and placed in a reactor as a reaction base liquid;

[0049] 3) 2.5 mol / L nickel-manganese mixed salt solution, 0.03 g / L potassium persulfate solution, 0.10 g / L sodium thiosulfate solution, 0.3 g / L sodium hydroxide solution, and 1 g / L urea solution were introduced into the reactor in a volume ratio of 80:3:4.5:45:6, and the pH was controlled at 11.0±0.1, the temperature was 50°C, and the rotation speed was 600 r / min to form a reaction slurry;

[0050] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a nickel-manganese molar ratio of 35:65, a D50 of 10 μm, and primary particles are short and thin strips with an aspect ratio of 6.66:1 and are evenly distributed. The tap density is 1.95 g / cm 3 , the specific surface area is 65m 2 / g.

[0051] Example 2

[0052] 1) Prepare a 2.5 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a molar ratio of nickel to manganese of 40:60; prepare a 0.02 g / L sodium persulfate solution at 40°C and a 0.10 g / L vitamin C solution at 40°C;

[0053] 2) A mixture of 0.5 g / L sodium hydroxide, 1.2 g / L ammonia water, and pure water at a volume ratio of 0.4:0.2:60 was prepared and placed in a reaction kettle as a reaction base liquid;

[0054] 3) 2.5 mol / L nickel-manganese mixed salt solution, 0.02 g / L sodium persulfate solution, 0.10 g / L vitamin C solution, 0.5 g / L sodium hydroxide solution, and 1.2 g / L ammonia solution were concurrently introduced into a reactor at a volume ratio of 90:2.5:5:50:7, with the pH controlled at 11.5±0.1, the temperature at 55°C, and the rotation speed at 800 r / min to form a reaction slurry;

[0055] 4) After the reaction is completed, the reaction slurry is aged, centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a nickel-manganese molar ratio of 40:60, a D50 of 9 μm, and primary particles are short and thin strips with an aspect ratio of 10.51:1 and are evenly distributed. The tap density is 2.0 g / cm 3 , with a specific surface area of ​​68m 2 / g.

[0056] Example 3

[0057] 1) Prepare a 2.7 mol / L nickel-manganese mixed salt solution with nickel acetate and manganese acetate, with a nickel to manganese molar ratio of 45:55; prepare a 0.05 g / L hydrogen peroxide solution at 40°C and a 0.20 g / L oxalic acid solution at 40°C;

[0058] 2) A mixture of 0.7 g / L sodium hydroxide solution, 1.5 g / L urea solution, and pure water at a volume ratio of 0.4:0.25:70 was prepared and placed in a reactor as a reaction base liquid;

[0059] 3) 2.7 mol / L nickel-manganese mixed salt solution, 0.05 g / L hydrogen peroxide solution, 0.20 g / L oxalic acid solution, 0.7 g / L sodium hydroxide solution, and 1.5 g / L urea solution were introduced into the reactor in a volume ratio of 100:2:5:55:9, and the pH was controlled at 11.8±0.1, the temperature was 60°C, and the rotation speed was 1000 r / min to form a reaction slurry;

[0060] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a nickel-manganese molar ratio of 45:55, a D50 of 8 μm, and primary particles that are short and thin strips with an aspect ratio of 11.09:1 and are uniformly distributed. The tap density is 2.1 g / cm 3 , the specific surface area is 75m 2 / g.

[0061] Example 4

[0062] 1) Prepare a 1.0 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a molar ratio of nickel to manganese of 20:80; prepare a 0.02 g / L potassium persulfate solution at 30°C and a 0.02 g / L sodium thiosulfate solution at 30°C;

[0063] 2) A mixture of 0.2 g / L sodium hydroxide solution, 0.2 g / L urea solution, and pure water at a volume ratio of 0.2:0.1:70 was prepared and placed in a reaction kettle as a reaction base liquid;

[0064] 3) nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were introduced into the reactor in a volume ratio of 30:3:5:55:10, and the pH was controlled at 10.1±0.1, the temperature was 30° C., and the rotation speed was 1000 r / min to form a reaction slurry;

[0065] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a D50 of 8 μm, primary particles are short and thin strips, have an aspect ratio of 9.98:1, and are evenly distributed, and have a tap density of 1.88 g / cm 3 , the specific surface area is 54m 2 / g.

[0066] Example 5

[0067] 1) Prepare a 3.0 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a molar ratio of nickel to manganese of 50:50; prepare a 0.1 g / L potassium persulfate solution at 50°C and a 0.2 g / L sodium thiosulfate solution at 50°C;

[0068] 2) A mixture of 5 g / L sodium hydroxide solution, 20 g / L urea solution, and pure water at a volume ratio of 0.4:0.25:40 was prepared and placed in a reactor as a reaction base liquid;

[0069] 3) nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were introduced into the reactor in a volume ratio of 100:0.1:0.2:15:2, and the pH was controlled at 12.9±0.1, the temperature was 80°C, and the rotation speed was 200 r / min to form a reaction slurry;

[0070] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a D50 of 9 μm, primary particles are short and thin strips, have an aspect ratio of 12.02:1, and are evenly distributed, and have a tap density of 1.79 g / cm 3 , the specific surface area is 70m 2 / g.

[0071] Comparative Example 1

[0072] A mixed solution of 0.3 g / L sodium hydroxide solution, 1 g / L urea solution, and pure water in a volume ratio of 0.35:0.15:50 is prepared and placed in a reactor as a reaction base liquid; then a nickel-manganese mixed sulfate solution (the molar ratio of nickel to manganese is 35:65, and its concentration is 2.5 mol / L), 0.3 g / L sodium hydroxide solution, and 1 g / L urea solution in a volume ratio of 80:45:6 are added to the reactor for reaction, the reactor speed is 600 r / min, and an inert gas such as nitrogen is used as a protective gas and is introduced into the reaction system at a flow rate of 10 L / min for protection throughout the process; the temperature of the reaction system is controlled at 50°C and the pH is between 11.0±0.1, and the feeding is stopped until the D50 is 10 μm to terminate the reaction; aging treatment, centrifugal washing, high-speed drying, vacuum drying, and vibration screening are performed to obtain the manganese-rich precursor.

[0073] Comparative Example 2

[0074] 1) Prepare a 0.5 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a molar ratio of nickel to manganese of 15:85; prepare a 20°C, 0.01 g / L potassium persulfate solution and a 20°C, 0.01 g / L sodium thiosulfate solution;

[0075] 2) A mixture of 0.1 g / L sodium hydroxide solution, 0.1 g / L urea solution, and pure water at a volume ratio of 0.15:0.05:75 was prepared and placed in a reaction kettle as a reaction base liquid;

[0076] 3) Adding nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution in a volume ratio of 25:3.5:5.5:60:12 to the reactor in parallel, controlling the pH at 9.5±0.1, the temperature at 20°C, and the rotation speed at 1100 r / min to form a reaction slurry;

[0077] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a D50 of 10 μm, primary particles are short and thin strips, have an aspect ratio of 3.54:1, and are evenly distributed, and have a tap density of 1.19 g / cm 3 , the specific surface area is 35m 2 / g.

[0078] Comparative Example 3

[0079] 1) Prepare a 3.5 mol / L nickel-manganese mixed salt solution with nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 55:45; prepare a 0.12 g / L potassium persulfate solution at 60°C and a 0.22 g / L sodium thiosulfate solution at 60°C;

[0080] 2) A mixture of 5.5 g / L sodium hydroxide solution, 21 g / L urea solution, and pure water at a volume ratio of 0.45:0.3:35 was prepared and placed in a reactor as a reaction base liquid;

[0081] 3) introducing the nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution into the reactor in a volume ratio of 110:0.05:0.1:10:1, controlling the pH at 13.5±0.1, the temperature at 90°C, and the rotation speed at 150 r / min to form a reaction slurry;

[0082] 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor; the obtained modified cobalt-free lithium-rich manganese-based precursor has a D50 of 10 μm, primary particles are short and thin strips, have an aspect ratio of 2.99:1, and are evenly distributed, and have a tap density of 1.25 g / cm 3 , the specific surface area is 30m 2 / g.

[0083] The SEM picture of the precursor prepared in Example 1 is shown in FIG1 ; the SEM picture of the precursor prepared in Example 2 is shown in FIG2 ; the SEM picture of the precursor prepared in Example 3 is shown in FIG3 ; the SEM picture of the precursor prepared in Comparative Example 1 is shown in FIG4 .

[0084] Test method:

[0085] D50: Laser particle size distribution analyzer;

[0086] Primary particle aspect ratio: scanning electron microscopy;

[0087] Tap density: tap density meter;

[0088] Specific surface area: specific surface area meter.

[0089] In Comparative Example 1, it is worth emphasizing that in the process of preparing the manganese-rich precursor by this method, since an inert gas such as nitrogen is selected as a protective gas and is introduced into the reaction system throughout the process, the pressure of the reaction system reaches 5000-15000 Pa, which poses a certain degree of safety hazard. In addition, a large amount of manganese oxides will be attached to the middle and surface of the primary particles of the obtained precursor, which is difficult to remove in the subsequent treatment, resulting in serious problems of uneven and insufficient manganese co-precipitation. At the same time, the various indicators of the precursor do not meet the target requirements. Even if the tap density reaches 2.0 g / cm 3 The above problems will also face the problem of primary particle crushing and small specific surface area, with the highest specific surface area only reaching 10-30m 2 / g, which seriously affects the electrical properties of the manganese-rich precursor positive electrode materials.

[0090] In summary, it can be seen that in the preparation of the manganese-rich precursor of the present application, the role of the oxidant is to refine the primary particles of the precursor and oxidize them uniformly; the role of the reducing agent is to reduce the over-refined primary particles and transform them into excellent and uniform primary particles again, so that the morphology reaches the ideal expectation. The most significant improvement is that a large amount of manganese oxides are attached to the middle and surface of the primary particles of the precursor, which is difficult to remove in subsequent treatments, resulting in serious uneven and insufficient manganese co-precipitation problems. The specific surface area is increased to 40-80m 2 / g, thereby improving the various indicators and excellent morphology of the manganese-rich precursor and improving the electrical properties of the manganese-rich precursor positive electrode material. In addition, it can be seen that when all process parameters are within the preferred range of this application, the comprehensive performance of the material is better.

[0091] Obviously, it should be emphasized at the end that professional and technical personnel engaged in the field of precursor production can produce precursors that are better than those of this application according to the implementation cases listed in this application. However, from the perspective of the inventor's invention patent, any technical scope belonging to this application, if replaced or replaced by professional and technical personnel in the same field, shall fall within the protection scope and disclosure scope of this application, and shall not cause the essence of the corresponding technical solutions of others to deviate from the scope of the embodiment technical solutions of this application.

Claims

1. A method for preparing a modified cobalt-free lithium-rich manganese-based precursor, characterized in that: The following steps are involved: 1) preparing a nickel-manganese mixed salt solution, an oxidant solution, and a reducing agent solution; the nickel-manganese mixed salt solution has a concentration of 1.0-3.0 mol / L and is prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate; the oxidant solution has a temperature of 30-50° C. and a concentration of 0.02-0.1 g / L and is prepared from one or more of potassium permanganate, perchloric acid, hypochlorous acid, hydrogen peroxide, sodium hypochlorite, potassium persulfate, sodium persulfate, and ammonium persulfate; the reducing agent solution has a temperature of 30-50° C. and a concentration of 0.02-0.2 g / L and is prepared from one or more of sodium thiosulfate, vitamin C, sodium D-isoascorbate, oxalic acid, potassium borohydride, sodium borohydride, and ethanol; 2) preparing a mixed solution of an alkali solution, a complexing agent solution and water in a volume ratio of (0.2-0.4): (0.1-0.25): (40-70) and placing the mixed solution in a reaction kettle as a reaction bottom solution; the alkali solution is one or more of sodium hydroxide and potassium hydroxide solutions, and the complexing agent solution is one or more of ammonia water, urea, EDTA, ethylenediamine and citric acid solutions; the concentration of the alkali solution is 0.2-5 g / L, and the concentration of the complexing agent solution is 0.2-20 g / L; 3) the nickel-manganese mixed salt solution, the oxidant solution, the reductant solution, the alkali solution, and the complexing agent solution are added to a reaction kettle in a volume ratio of (30-100): (0.1-3): (0.2-5): (15-55): (2-10), and the pH is controlled at 10-13 and the temperature is controlled at 30-80° C. to form a reaction slurry; 4) After the reaction is completed, the reaction slurry is aged, then centrifuged, washed, dried at high speed, vacuum dried, and vibrated to obtain a cobalt-free lithium-rich manganese-based precursor.

2. The method for preparing the modified cobalt-free lithium-rich manganese-based precursor according to claim 1, characterized in that: In step 1), the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (20-50): (50-80); preferably, the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (35-45): (65-65).

3. The method for preparing the modified cobalt-free lithium-rich manganese-based precursor according to claim 1 or 2, characterized in that: In step 1), the concentration of the nickel-manganese mixed salt solution is 2.5-2.7 mol / L, the concentration of the oxidant solution is 0.02-0.05 g / L, and the concentration of the reductant solution is 0.1-0.2 g / L.

4. The method for preparing the modified cobalt-free lithium-rich manganese-based precursor according to any one of claims 1 to 3, characterized in that: In step 2), the alkaline solution, the complexing agent solution and water are prepared into a mixed solution in a volume ratio of (0.35-0.4): (0.15-0.25): (50-70) and placed in a reaction kettle as the reaction base liquid; preferably, the concentration of the alkaline solution is 0.3-0.7 g / L, and the concentration of the complexing agent solution is 1-1.5 g / L.

5. The method for preparing the modified cobalt-free lithium-rich manganese-based precursor according to any one of claims 1 to 4, characterized in that: In step 3), the nickel-manganese mixed salt solution, the oxidant solution, the reductant solution, the alkali solution, and the complexing agent solution are simultaneously flowed into a reaction kettle in a volume ratio of (80-100): (2-3): (4.5-5): (45-55): (6-9).

6. The method for preparing the modified cobalt-free lithium-rich manganese-based precursor according to any one of claims 1 to 5, characterized in that: In step 3), the pH is controlled at 10.9-11.9 and the temperature is controlled at 50-60° C. to form the reaction slurry.

7. The method for preparing a modified cobalt-free lithium-rich manganese-based precursor according to any one of claims 1 to 6, characterized in that: In step 3), the rotation speed of the reactor is 200-1000 r / min; preferably, the rotation speed of the reactor is 600-1000 r / min.

8. A modified cobalt-free lithium-rich manganese-based precursor, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. The modified cobalt-free lithium-rich manganese-based precursor according to claim 8, characterized in that: The modified cobalt-free lithium-rich manganese-based precursor has a D50 of 5-20 μm and a tap density of more than 1.3 g / cm 3 , with a specific surface area of ​​40-80m 2 / g; Preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is not less than 1.95g / cm 3 , with a specific surface area of ​​65-80m 2 / g; More preferably, the tap density of the modified cobalt-free lithium-rich manganese-based precursor is 1.95-2.1g / cm 3 , with a specific surface area of ​​65-75m 2 / g.

10. The modified cobalt-free lithium-rich manganese-based precursor according to claim 8 or 9, characterized in that: The modified cobalt-free lithium-rich manganese-based precursor is in the shape of short thin strips, and the aspect ratio is (5-13):1.

Images