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

Abstract

This application discloses a method for producing a modified cobalt-free, lithium-rich, manganese-based precursor, and the modified cobalt-free, lithium-rich, manganese-based precursor produced thereby effectively reduces the amount of manganese series oxides attached to the interior and surface of the primary particles, making the primary particles uniform and dense, and at the same time, increasing the specific surface area to 40m 2 / g~80m 2 / g, and the tap density is 1.3g / cm 3 The precursor produced by this method, in which the oxidant solution and the reductant solution are mixed and introduced into the reaction system, is low-cost, environmentally friendly, and pollution-free. Furthermore, it replaces conventional protection methods such as the introduction of inert gases such as nitrogen, effectively reducing the safety risks associated with high reaction pressure. In summary, the cobalt-free, lithium-rich, manganese-based precursor produced by this method not only ensures excellent indexes and morphology, but also reduces production costs, thereby conforming to the concept of green and sustainable development.

Description

[Technical Field]

[0001] This application claims priority from Chinese Patent Application No. 202311455129.7, filed on November 3, 2023. The entire text of the above Chinese patent application is incorporated herein by reference.

[0002] This application is in the field of lithium-ion battery cathode materials, and more particularly relates to a modified cobalt-free, lithium-rich, manganese-based precursor and a method for preparing the same. [Background technology]

[0003] In recent years, the demand for rechargeable batteries has been increasing in areas such as electronic digital devices (such as mobile phones and laptops), power tools (such as battery cars and drones), and electric vehicles (such as EVs and HEVs). In the current market, lithium-ion batteries have a very wide range of demand prospects and application fields. In this case, the cathode materials that affect the electrical performance of lithium-ion batteries are also attracting increasing attention.

[0004] Currently, nickel-cobalt-manganese ternary positive electrode materials have been extensively researched and applied due to their relatively high energy density, relatively stable cycle performance and cycle life, and relatively high multiplication performance. However, due to the continuous rise in the price of cobalt in recent years, the production costs have increased, and more and more precursor positive electrode materials are being converted from nickel-cobalt-manganese ternary materials to nickel-manganese binary materials. At the same time, nickel-manganese binary precursor positive electrode materials are considered to be one of the most competitively advantageous positive electrode materials in the future market.

[0005] However, the process of preparing nickel-manganese binary precursors by coprecipitation has many unresolved problems. The most obvious problem is that the manganese coprecipitation is uneven in all the prepared precursors, regardless of whether they are large or small particles. A large amount of manganese series oxides adhere to the interior and surface of the primary particles, and their specific surface area is at most 10 m2 / g~30m 2 / g, and therefore the parameters and morphology of such precursors are affected, as well as the multiplier performance of such precursor cathode materials. Summary of the Invention

[0006] In view of the above problems, the present application aims to propose a method that can effectively solve the problem of non-uniform co-precipitation of manganese in the production of nickel-manganese binary precursors, by using an oxidizing agent solution and a reducing agent solution instead of an inert gas such as nitrogen gas as protection, to improve the specific surface area of ​​the manganese-rich precursor, and to make the primary particles finer and more uniform.

[0007] To achieve the above-mentioned objectives, the present application provides the following technical means: a method for producing a modified cobalt-free, lithium-rich, manganese-based precursor, comprising the following steps:

[0008] Step 1): Prepare a nickel-manganese mixed salt solution, an oxidizing agent solution, and a reducing agent solution. The nickel-manganese mixed salt solution has a concentration of 1.0 mol / L to 3.0 mol / L and is prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate. The oxidizing agent solution has a concentration of 0.02 g / L to 0.1 g / L and is prepared at a temperature of 30°C to 50°C 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 concentration of 0.02 g / L to 0.2 g / L and is prepared at a temperature of 30°C to 50°C from one or more of sodium thiosulfate, vitamin C, sodium D-isoascorbate, oxalic acid, potassium borohydride, sodium borohydride, and ethanol. Step 2): A mixture of an alkaline solution, a complexing agent solution, and water in a volume ratio of (0.2-0.4):(0.1-0.25):(40-70) was charged into the reactor as the reaction bottom liquid; Step 3): The nickel-manganese mixed salt solution, oxidizing agent solution, reducing agent solution, alkali solution, and complexing agent solution were mixed in a reactor in a volume ratio of (30-100):(0.1-3):(0.2-5):(15-55):(2-10), and the pH was controlled to 10-13 and the temperature to 30-80°C to form a reaction slurry; Step 4): After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain the cobalt-free, lithium-rich, manganese-based precursor.

[0009] Preferably, in step 1), the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (20-50):(50-80), and more preferably, the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (35-45):(65-65).

[0010] Preferably, in step 1), the concentration of the nickel-manganese mixed salt solution is 2.5 mol / L to 2.7 mol / L, the concentration of the oxidizing agent solution is 0.02 g / L to 0.05 g / L, and the concentration of the reducing agent solution is 0.1 g / L to 0.2 g / L.

[0011] Preferably, in step 2), a mixed solution prepared by mixing 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 charged into the reaction vessel as the reaction bottom solution, and preferably, the concentration of the alkaline solution is 0.3 g / L to 0.7 g / L, and the concentration of the complexing agent solution is 1 g / L to 1.5 g / L.

[0012] Preferably, in step 3), the nickel-manganese mixed salt solution, the oxidizing agent solution, the reducing agent solution, the alkali solution, and the complexing agent solution are allowed to join in the reaction vessel at a volume ratio of (80-100):(2-3):(4.5-5):(45-55):(6-9).

[0013] Preferably, in step 3), the pH is controlled to 10.9 to 11.9 and the temperature is controlled to 50°C to 60°C to form a reaction slurry.

[0014] Preferably, in step 3), the rotation speed of the reaction vessel is 200 r / min to 1000 r / min, and more preferably, the rotation speed of the reaction vessel is 600 r / min to 1000 r / min.

[0015] Preferably, the alkaline solution is one or more of a solution of sodium hydroxide and potassium hydroxide, and the complexing agent solution is one or more of a solution of ammonia water, urea, EDTA, ethylenediamine, and citric acid; the concentration of the alkaline solution is 0.2 g / L to 5 g / L, and the concentration of the complexing agent solution is 0.2 g / L to 20 g / L.

[0016] The modified cobalt-free, lithium-rich, manganese-based precursor produced in this application has a D50 of 5 μm to 20 μm, thin, strip-shaped primary particles that are uniformly distributed, and a tap density of 1.3 g / cm. 3 The specific surface area is 40m 2 / g~80m 2 It is located at / g.

[0017] Preferably, the modified cobalt-free, lithium-rich, manganese-based precursor has a tap density of 1.95 g / cm 3 The specific surface area must not be less than 65m 2 / g~80m 2 / g; more preferably, the modified cobalt-free lithium-rich manganese-based precursor has a tap density of 1.95 g / cm 3 ~2.1g / cm 3 and the specific surface area is 65m 2 / g~75m 2 / g.

[0018] Preferably, the modified cobalt-free lithium-rich manganese-based precursor is in the form of thin strips with an aspect ratio of (5-13):1.

[0019] In conventional manganese-rich precursors, the co-precipitation of manganese may be uneven, and a large amount of manganese series oxides may adhere to the interior and surface of the primary particles. This will seriously affect the indexes and morphology of the precursor. In addition, the electrical performance of the precursor positive electrode material will also be significantly affected, which may even pose a hidden safety hazard.

[0020] The present invention can bring the following beneficial effects compared to the conventional technology: the modified cobalt-free, lithium-rich, manganese-based precursor produced by the present invention effectively reduces the amount of manganese-series oxides attached to the interior and surface of the primary particles, making the primary particles uniform and dense, and at the same time, increasing the specific surface area to 40m 2 / g~80m 2 / g, and the tap density is 1.3g / cm 3 The precursor produced by this method, in which the oxidant solution and the reductant solution are mixed and introduced into the reaction system, is low-cost, environmentally friendly, and pollution-free. Furthermore, it replaces conventional protection methods such as the introduction of inert gases such as nitrogen, effectively reducing the safety risks associated with high reaction pressure. In summary, the cobalt-free, lithium-rich, manganese-based precursor produced by this method not only ensures excellent indexes and morphology, but also reduces production costs, thereby conforming to the concept of green and sustainable development. [Brief explanation of the drawings]

[0021] The drawings in the specification that form a part of this application are intended to provide a further understanding of the application, and the exemplary embodiments and descriptions thereof are intended to explain the application and are not intended to unduly limit the application. The drawings will now be briefly described. [Figure 1] SEM image of the precursor prepared in Example 1; [Figure 2] SEM image of the precursor prepared in Example 2; [Figure 3]SEM image of the precursor prepared in Example 3; [Figure 4] SEM image of the precursor prepared in Comparative Example 1; DETAILED DESCRIPTION OF THE INVENTION

[0022] It should be noted that the embodiments and features of the embodiments described herein can be combined with each other if no contradiction occurs. The present application will now be described in detail with reference to the accompanying drawings.

[0023] Unless otherwise specified, the materials used in this application may be self-prepared by conventional methods in the art, or may be readily purchased from the market.

[0024] Unless otherwise specified, all "solutions" described in this application are aqueous solutions.

[0025] As mentioned in the background section of this application, the prior art has a problem of non-uniform co-precipitation of manganese in the production of nickel-manganese binary precursors.To solve the above-mentioned problems, an exemplary embodiment of the present application proposes a method for preparing a modified cobalt-free, lithium-rich, manganese-based precursor, which includes the following steps: Step 1): preparing a nickel-manganese mixed salt solution, an oxidizing agent solution, and a reducing agent solution; the nickel-manganese mixed salt solution has a concentration of 1.0 mol / L to 3.0 mol / L and is prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate; the oxidizing agent solution is heated at a temperature of 30°C to 50°C. The reducing agent solution has a concentration of 0.02 g / L to 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°C to 50°C and a concentration of 0.02 g / L to 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. Step 2): A mixed solution prepared by mixing an alkaline solution, a complexing agent solution, and water in a volume ratio of (0.2-0.4):(0.1-0.25):(40-70) was charged into the reactor as the reaction bottom solution; the alkaline solution was one or more of a solution of sodium hydroxide and potassium hydroxide, and the complexing agent solution was one or more of a solution of ammonia water, urea, EDTA, ethylenediamine, and citric acid; the concentration of the alkaline solution was 0.2 g / L-5 g / L, and the concentration of the complexing agent solution was 0.2 g / L-20 g / L; Step 3): Ni The nickel manganese mixed salt solution, oxidant solution, reductant solution, alkali solution, and complexing agent solution were mixed in a reactor in a volume ratio of (30-100):(0.1-3):(0.2-5):(15-55):(2-10), and the pH was controlled at 10-13 and the temperature at 30-80°C to form a reaction slurry; step 4): After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibrated and sieved to obtain the cobalt-free lithium-rich manganese-based precursor.

[0026] In this study, a nickel-manganese mixed salt solution, an oxidizing agent solution, and a reducing agent solution were first prepared. At the same time, an alkaline solution, a complexing agent solution, and water were prepared, and the resulting mixture was added to the reactor as the bottom solution. The nickel-manganese mixed salt solution, the oxidizing agent solution, the reducing agent solution, the alkaline solution, and the complexing agent solution were then mixed in a specific volume ratio and reacted under pH and temperature control. During this process, complexation, precipitation, and oxidation-reduction reactions occurred, forming a reaction slurry. Finally, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibrated and sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor.

[0027] In this application, an oxidizing agent solution and a reducing agent solution are introduced into the reaction system together, and the oxidizing agent refines and uniformly oxidizes the primary particles of the precursor, while the reducing agent reduces the excessively refined primary particles, transforming them back into highly uniform primary particles. The resulting modified cobalt-free lithium-rich manganese-based precursor effectively reduces the amount of manganese oxides adhering to the interior and surface of the primary particles, resulting in uniform and dense primary particles with improved specific surface area and tap density. Furthermore, the use of a combined oxidizing agent and reducing agent instead of conventional protective methods such as introducing inert gases such as nitrogen gas effectively reduces safety risks associated with high pressure in the reaction system, while also reducing costs and environmental pollution.

[0028] According to 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), and preferably the molar ratio of nickel to manganese in the nickel-manganese mixed salt solution is (35-45):(65-65). Under the above conditions, the morphology and performance of the particles can be further improved.

[0029] To further balance the cost and product index, according to a preferred embodiment, in step 1), the concentration of the nickel-manganese mixed salt solution is 2.5 mol / L to 2.7 mol / L, the concentration of the oxidizing agent solution is 0.02 g / L to 0.05 g / L, and the concentration of the reducing agent solution is 0.1 g / L to 0.2 g / L.

[0030] According to 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 charged into the reactor as the reaction bottom liquid, and preferably the concentration of the alkaline solution is 0.3 g / L-0.7 g / L, and the concentration of the complexing agent solution is 1 g / L-1.5 g / L. Under the above conditions, the primary particles become more uniform, making it easier to control their aspect ratio.

[0031] For the purposes of more thoroughly removing manganese oxide from the surfaces of primary particles, controlling the aspect ratio, and achieving a higher tap density and specific surface area, in a preferred embodiment, in step 3), the nickel-manganese mixed salt solution, oxidizing agent solution, reducing agent solution, alkali solution, and complexing agent solution were combined in a reaction vessel at a volume ratio of (80-100):(2-3):(4.5-5):(45-55):(6-9).

[0032] According to a preferred embodiment, in step 3), the reaction slurry was formed by controlling the pH to 10.9 to 11.9 and the temperature to 50 to 60° C. Under the above conditions, it became easier to control the reaction conditions, it became easier to simultaneously achieve a high tap density and a high specific surface area, and the amount of manganese oxide on the surfaces of the primary particles was further reduced.

[0033] For similar reasons as above, according to a preferred embodiment, in step 3), the rotation speed of the reaction vessel is 200 r / min to 1000 r / min, preferably 600 r / min to 1000 r / min.

[0034] Another exemplary embodiment of the present application provides a modified cobalt-free, lithium-rich, manganese-based precursor, which is produced by the above-described production method of the present application. By using the production method of the present application, the amount of manganese-series oxides attached to the interior and surface of the primary particles is reduced, and the specific surface area and tap density are significantly increased, with low safety risks, low cost, and minimal environmental pollution.

[0035] Specifically, according to one preferred embodiment, the modified cobalt-free lithium-rich manganese-based precursor has a D50 of 5 μm to 20 μm and a tap density of 1.3 g / cm 3 The specific surface area is 40m 2 / g~80m 2 / g; preferably, the modified cobalt-free lithium-rich manganese-based precursor has a tap density of 1.95 g / cm 3 and the specific surface area is not less than 65m 2 / g~80m 2 / g; more preferably, the modified cobalt-free lithium-rich manganese-based precursor has a tap density of 1.95 g / cm 3 ~2.1g / cm 3 The specific surface area is 65m 2 / g~75m 2 / g.

[0036] Furthermore, since the oxidizing agent and reducing agent were introduced simultaneously, in a preferred embodiment, the modified cobalt-free lithium-rich manganese-based precursor has a thin strip shape with an aspect ratio of (5-13):1.

[0037] Hereinafter, the present application will be described in more detail with reference to specific examples, which, however, cannot be construed as limiting the scope of protection of the present application.

[0038] Example 1 1) A 2.5 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 35:65; a 0.03 g / L potassium persulfate solution at 40°C and a 0.10 g / L sodium thiosulfate solution at 40°C were prepared; 2) A mixture 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 was charged into the reactor as the reaction bottom liquid; 3) A 2.5 mol / L nickel-manganese mixed salt solution, a 0.03 g / L potassium persulfate solution, a 0.10 g / L sodium thiosulfate solution, a 0.3 g / L sodium hydroxide solution, and a 1 g / L urea solution were mixed together in a volume ratio of 80:3:4.5:45:6 and introduced into a reactor. The pH was controlled to 11.0±0.1, the temperature to 50°C, and the rotation speed to 600 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a nickel to manganese molar ratio of 35:65, a D50 of 10 μm, thin, rectangular primary particles with an aspect ratio of 6.66:1 and uniform distribution, and a tap density of 1.95 g / cm. 3 and the specific surface area is 65m 2 / g.

[0039] Example 2 1) A 2.5 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 40:60; a 0.02 g / L sodium persulfate solution at 40°C and a 0.10 g / L vitamin C solution at 40°C were prepared; 2) A mixture of 0.5 g / L sodium hydroxide, 1.2 g / L aqueous ammonia, and pure water in a volume ratio of 0.4:0.2:60 was charged into the reactor as the reaction bottom liquid; 3) A 2.5 mol / L nickel-manganese mixed salt solution, a 0.02 g / L sodium persulfate solution, a 0.10 g / L vitamin C solution, a 0.5 g / L sodium hydroxide solution, and a 1.2 g / L aqueous ammonia solution were mixed together in a volume ratio of 90:2.5:5:50:7 and introduced into a reactor. The pH was controlled to 11.5±0.1, the temperature to 55°C, and the rotation speed to 800 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was subjected to aging treatment, followed by centrifugation, washing, high-speed spin drying, vacuum oven drying, and vibration sieving to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a nickel to manganese molar ratio of 40:60, a D50 of 9 μm, thin, rectangular primary particles with an aspect ratio of 10.51:1 and uniform distribution, and a tap density of 2.0 g / cm. 3 and the specific surface area is 68m 2 / g.

[0040] Example 3 1) A 2.7 mol / L nickel-manganese mixed salt solution was prepared using nickel acetate and manganese acetate, with the molar ratio of nickel to manganese being 45:55; a 0.05 g / L hydrogen peroxide solution at 40°C and a 0.20 g / L oxalic acid solution at 40°C were prepared; 2) A mixture of 0.7 g / L sodium hydroxide solution, 1.5 g / L urea solution, and pure water in a volume ratio of 0.4:0.25:70 was charged into the reactor as the reaction bottom liquid; 3) A 2.7 mol / L nickel-manganese mixed salt solution, a 0.05 g / L hydrogen peroxide solution, a 0.20 g / L oxalic acid solution, a 0.7 g / L sodium hydroxide solution, and a 1.5 g / L urea solution were mixed together in a volume ratio of 100:2:5:55:9 and introduced into a reactor. The pH was controlled to 11.8±0.1, the temperature to 60°C, and the rotation speed to 1000 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was subjected to aging treatment, followed by centrifugation, washing, high-speed spin drying, vacuum oven drying, and vibration sieving to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a nickel to manganese molar ratio of 45:55, a D50 of 8 μm, thin, rectangular primary particles with an aspect ratio of 11.09:1 and uniform distribution, and a tap density of 2.1 g / cm. 3 and the specific surface area is 75m 2 / g.

[0041] Example 4 1) A 1.0 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 20:80; a 0.02 g / L potassium persulfate solution at 30°C and a 0.02 g / L sodium thiosulfate solution at 30°C were prepared; 2) A mixture of 0.2 g / L sodium hydroxide solution, 0.2 g / L urea solution, and pure water in a volume ratio of 0.2:0.1:70 was charged into the reactor as the reaction bottom liquid; 3) The nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were mixed in a volume ratio of 30:3:5:55:10 and introduced into the reactor. The pH was controlled to 10.1±0.1, the temperature to 30°C, and the rotation speed to 1000 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a D50 of 8 μm, thin, rectangular primary particles with an aspect ratio of 9.98:1 and uniform distribution, and a tap density of 1.88 g / cm. 3 and the specific surface area is 54m 2 / g.

[0042] Example 5 1) A 3.0 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 50:50; a 0.1 g / L potassium persulfate solution at 50°C and a 0.2 g / L sodium thiosulfate solution at 50°C were prepared; 2) A mixture of 5 g / L sodium hydroxide solution, 20 g / L urea solution, and pure water in a volume ratio of 0.4:0.25:40 was charged into the reactor as the reaction bottom liquid; 3) The nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were mixed together in a volume ratio of 100:0.1:0.2:15:2 and introduced into the reactor. The pH was controlled to 12.9±0.1, the temperature to 80°C, and the rotation speed to 200 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a D50 of 9 μm, thin, rectangular primary particles with an aspect ratio of 12.02:1, and was uniformly distributed. Its tap density was 1.79 g / cm. 3 and the specific surface area is 70m 2 / g.

[0043] Comparative Example 1 A mixture 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 was introduced into the reactor as the bottom reaction solution; then, a nickel-manganese mixed sulfate solution (nickel and manganese molar ratio is 35:65, and its concentration is 2.5 mol / L), 0.3 g / L sodium hydroxide solution, and 1 g / L urea solution were mixed in a volume ratio of 80:45:6 and reacted in the reactor. The rotation speed was set to 600 r / min, and at the same time, an inert gas such as nitrogen gas was introduced into the reaction system at a flow rate of 10 L / min as a protective gas to protect the reaction system throughout the entire process; the temperature of the reaction system was controlled at 50°C, and the pH was controlled within the range of 11.0±0.1. When the D50 reached 10 μm, the material supply was stopped to terminate the reaction; after aging treatment, centrifugation, washing, high-speed spin drying, vacuum oven drying, and vibration screening, the manganese-rich precursor was obtained.

[0044] Comparative Example 2 1) A 0.5 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 15:85; a 0.01 g / L potassium persulfate solution at 20°C and a 0.01 g / L sodium thiosulfate solution at 20°C were prepared; 2) A mixture of 0.1 g / L sodium hydroxide solution, 0.1 g / L urea solution, and pure water in a volume ratio of 0.15:0.05:75 was charged into the reactor as the reaction bottom liquid; 3) The nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were mixed together in a volume ratio of 25:3.5:5.5:60:12 and introduced into the reactor. The pH was controlled to 9.5±0.1, the temperature to 20°C, and the rotation speed to 1100 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a D50 of 10 μm, thin, rectangular primary particles with an aspect ratio of 3.54:1 and uniform distribution, and a tap density of 1.19 g / cm. 3 and the specific surface area is 35m 2 / g.

[0045] Comparative Example 3 1) A 3.5 mol / L nickel-manganese mixed salt solution was prepared using nickel sulfate and manganese sulfate, with a nickel to manganese molar ratio of 55:45; a 0.12 g / L potassium persulfate solution at 60°C and a 0.22 g / L sodium thiosulfate solution at 60°C were prepared; 2) A mixture of 5.5 g / L sodium hydroxide solution, 21 g / L urea solution, and pure water in a volume ratio of 0.45:0.3:35 was charged into the reactor as the reaction bottom liquid; 3) The nickel-manganese mixed salt solution, potassium persulfate solution, sodium thiosulfate solution, sodium hydroxide solution, and urea solution were mixed together in a volume ratio of 110:0.05:0.1:10:1 and introduced into the reactor. The pH was controlled to 13.5±0.1, the temperature to 90°C, and the rotation speed to 150 r / min to form a reaction slurry; 4) After the reaction was completed, the reaction slurry was aged, then centrifuged, washed, high-speed spin-dried, vacuum oven-dried, and vibro-sieved to obtain a cobalt-free, lithium-rich, manganese-based precursor. The obtained modified cobalt-free, lithium-rich, manganese-based precursor had a D50 of 10 μm, thin, rectangular primary particles with an aspect ratio of 2.99:1 and uniform distribution, and a tap density of 1.25 g / cm. 3 and the specific surface area is 30m 2 / g.

[0046] The SEM image of the precursor prepared in Example 1 is shown in FIG. 1; the SEM image of the precursor prepared in Example 2 is shown in FIG. 2; the SEM image of the precursor prepared in Example 3 is shown in FIG. 3; and the SEM image of the precursor prepared in Comparative Example 1 is shown in FIG. 4.

[0047] Measurement method D50: Laser particle size distribution analyzer; Aspect ratio of primary particles: scanning electron microscopy; Tapped density: Tapped density meter; Specific surface area: Specific surface area meter.

[0048] It is particularly emphasized that in Comparative Example 1, in the process of preparing the manganese-rich precursor by this method, an inert gas such as nitrogen gas was used as a protective gas and introduced into the reaction system throughout the entire process, so that the pressure strength of the reaction system reached 5000 Pa to 15000 Pa, which posed some hidden safety hazards; and a large amount of manganese series oxides adhered to the interior and surface of the primary particles of the prepared precursor, which were difficult to remove in the subsequent treatment, resulting in serious uneven and insufficient co-precipitation of manganese; at the same time, the indexes of the precursor did not meet the target requirements, for example, the tap density was 2.0 g / cm 3 Even if it reaches above 10m, problems such as primary particle crushing and a decrease in specific surface area must be faced. 2 / g~30m 2 / g, and therefore the electrical performance of the manganese-rich precursor cathode material was seriously affected.

[0049] To summarize the above, it has been found that in the preparation of the manganese-rich precursor according to the present invention, the function of the oxidizing agent is to refine and uniformly oxidize the primary particles of the precursor; the function of the reducing agent is to reduce the excessively refined primary particles and transform them into fine and uniform primary particles again, with the shape reaching the ideal expected state. Most importantly, the problem of a large amount of manganese series oxides adhering to the interior and surface of the primary particles of the precursor, which are difficult to remove in the subsequent treatment, and the severely uneven and insufficient co-precipitation of manganese, has been significantly improved. Furthermore, the specific surface area of ​​the precursor can be increased to 40 m 2 / g~80m 2 / g, the manganese-rich precursor had improved morphology and other indices, resulting in improved electrical performance. Furthermore, it was found that when the process parameters were within the preferred ranges of the present invention, the overall performance of the material was improved.

[0050] Obviously, it should be emphasized at the end that, although a professional technician engaged in the field of precursor production may be able to produce a precursor superior to that of the present application according to the embodiments set forth in this application, from the perspective of the inventor inventing a patent, any substitution or replacement made by a professional technician in this field that falls within the technical scope of the present application shall fall within the scope of protection and disclosure of the present application, and shall not cause the essence of other parties' corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. 1. A method for producing a modified cobalt-free lithium-rich manganese-based precursor, comprising the steps of: Step 1): A nickel-manganese mixed salt solution, an oxidizing agent solution, and a reducing agent solution were prepared; the nickel-manganese mixed salt solution had a concentration of 1.0 mol / L to 3.0 mol / L and was prepared from one or more of nickel-manganese sulfate, acetate, chloride, and nitrate; the oxidizing agent solution had a concentration of 0.02 g / L to 0.1 g / L and was prepared at a temperature of 30°C to 50°C 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 had a concentration of 0.02 g / L to 0.2 g / L and was prepared at a temperature of 30°C to 50°C from one or more of sodium thiosulfate, vitamin C, sodium D-isoascorbate, oxalic acid, potassium borohydride, sodium borohydride, and ethanol; Step 2): A mixture of an alkaline solution, a complexing agent solution, and water in a volume ratio of (0.2-0.4):(0.1-0.25):(40-70) is introduced into the reactor as the reaction bottom liquid; 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 water, urea, EDTA, ethylenediamine, and citric acid solutions; the concentration of the alkaline solution is 0.2 g / L-5 g / L, and the concentration of the complexing agent solution is 0.2 g / L-20 g / L; Step 3): The nickel-manganese mixed salt solution, the oxidizing agent solution, the reducing agent solution, the alkali solution, and the complexing agent solution were mixed together in a reactor in a volume ratio of (30-100):(0.1-3):(0.2-5):(15-55):(2-10), and the pH was controlled to 10-13 and the temperature to 30°C-80°C to form a reaction slurry; Step 4): After the reaction was completed, the reaction slurry was subjected to aging treatment, followed by centrifugation, washing, high-speed spin drying, vacuum oven drying, and vibration screening to obtain a cobalt-free lithium-rich manganese-based precursor.

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

3. 3. The method for producing a modified cobalt-free lithium-rich manganese-based precursor according to claim 1, wherein in step 1), the concentration of the nickel-manganese mixed salt solution is 2.5 mol / L to 2.7 mol / L, the concentration of the oxidizing agent solution is 0.02 g / L to 0.05 g / L, and the concentration of the reducing agent solution is 0.1 g / L to 0.2 g / L.

4. 4. The method for producing a modified cobalt-free lithium-rich manganese-based precursor according to claim 1, wherein in step 2), a mixed solution prepared by mixing the alkaline solution, the complexing agent solution, and water in a volume ratio of (0.35-0.4):(0.15-0.25):(50-70) is charged into the reaction vessel as the reaction bottom solution, and preferably, the concentration of the alkaline solution is 0.3 g / L to 0.7 g / L, and the concentration of the complexing agent solution is 1 g / L to 1.5 g / L.

5. 5. The method for producing a modified cobalt-free lithium-rich manganese-based precursor according to claim 1, wherein in step 3), the nickel-manganese mixed salt solution, the oxidizing agent solution, the reducing agent solution, the alkaline solution, and the complexing agent solution are mixed together in a reaction vessel at a volume ratio of (80-100):(2-3):(4.5-5):(45-55):(6-9).

6. 6. The method for producing a modified cobalt-free lithium-rich manganese-based precursor according to claim 1, wherein in step 3), the reaction slurry is formed by controlling the pH to 10.9 to 11.9 and the temperature to 50°C to 60°C.

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 reaction vessel is 200 r / min to 1000 r / min, preferably 600 r / min to 1000 r / min.

8. A modified cobalt-free lithium-rich manganese-based precursor, characterized in that it is produced by the production method according to any one of claims 1 to 7.

9. The modified cobalt-free lithium-rich manganese-based precursor has a D50 of 5 μm to 20 μm and a tap density of 1.3 g / cm ３ The specific surface area is 40m ２ / g~80m ２ / g, Preferably, the modified cobalt-free lithium-rich manganese-based precursor has a tap density of 1.95 g / cm ３ The specific surface area cannot be less than 65m ２ / g~80m ２ / g, More preferably, the modified cobalt-free lithium-rich manganese-based precursor has a tap density of 1.95 g / cm ３ ~2.1 g / cm ３ The specific surface area is 65m ２ / g~75m ２ 9. The modified cobalt-free lithium-rich manganese-based precursor of claim 8, wherein the cobalt-free lithium-rich manganese-based precursor has a stoichiometric ratio of 0.1 to 0.

25.

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 form of a thin strip and has an aspect ratio of (5-13):1.

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