Preparation method of equivalent water seepage washing liquid and application of cobalt-free high-nickel layered positive electrode material in residual alkali removal

Abstract

The invention discloses a preparation method of an equivalent water seepage washing solution and application of a cobalt-free high-nickel layered positive electrode material in residual alkali removal. The method comprises the following steps: synthesizing a cobalt-free high-nickel layered positive electrode material; determining the dissolution amount of transition metal ions in the cobalt-free high-nickel layered positive electrode material in the deionized water; under the stirring condition, according to the measured dissolution amount of the transition metal ions in the deionized water, a certain amount of transition metal salt is added into the deionized water, and the isotonic washing liquid is prepared. Under the stirring condition, the cobalt-free high-nickel layered positive electrode material is placed in an equal seepage water washing solution to be stirred for a certain time, and the cobalt-free high-nickel layered positive electrode material subjected to alkali removal treatment by the equal seepage water washing solution is obtained after suction filtration dehydration and drying under a certain condition. According to the washing method disclosed by the invention, the segregation dissolution of transition metal elements in the positive electrode material in the washing process can be reduced while the residual alkali is removed. In addition, the method has the characteristics of low cost, simplicity in implementation and suitability for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-ion battery materials and relates to a method for preparing an isotonic water washing solution and an application of a cobalt-free high-nickel layered positive electrode material in removing residual alkali. Background Art

[0002] The rapid development of new energy vehicles has put forward high requirements on the performance of power batteries, especially in terms of driving range, charging speed, service life and safety. x Mn 1-x O2, x ≥ 0.8) has become the preferred cathode material for lithium-ion batteries (LIBs) due to its high energy density and low cost. However, as the Ni content increases, the reactivity of the material decreases, and the amount of residual alkali on the surface of the material after solid-phase sintering is high. The presence of a large amount of residual alkali will significantly change the pH value, causing the active material slurry to gel during the homogenization process, which will have an adverse effect on the subsequent electrode preparation and processing. In order to reduce the residual alkali content on the surface of the material and alleviate the impact on the physical and chemical properties of the material, a washing step is usually introduced in the industrial preparation process of such materials to remove the residual alkali on the surface of the material.

[0003] Patent publication CN118572088A discloses a modified high-nickel ternary positive electrode material and its preparation method. The lithium-rich high-nickel positive electrode material is washed with water using a ligand formed by cyclodextrin and sodium metasilicate. Subsequently, an organic carbon sodium metasilicate composite layer is formed on the surface of the lithium-rich high-nickel positive electrode material through high-temperature calcination, which increases the lattice stability of the high-nickel material and improves the capacity and cycle performance of the material. Patent publication CN114226340A discloses a method for removing residual alkali from high-nickel positive electrode materials by water washing. By adding modified carboxymethyl cellulose CMCX (X=H or Li) to water, while removing the residual alkali on the surface of the high-nickel positive electrode material, the damage to the surface lattice of the material caused by water washing is weakened by lithium carboxymethyl cellulose. Although the above method can effectively remove the residual alkali on the surface and improve the surface quality of the material, it does not take into account the problem that the cobalt-free high-nickel positive electrode material is easily hydrolyzed and the dissolution rate of transition metal elements in the washing solution is inconsistent. This causes the surface chemical composition of the material to deviate from the design after water washing, and the crystal and phase structure of the surface material are damaged, which reduces the capacity and electrochemical performance to a certain extent. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a method for preparing an isotonic water washing solution and its application in removing residual alkali from cobalt-free, high-nickel layered positive electrode materials. First, the amount of transition metal elements contained in the cobalt-free, high-nickel layered positive electrode material that can be dissolved in deionized water is determined, and then a specific type and a certain amount of transition metal salts are selected to prepare an isotonic solution for the water washing treatment of the cobalt-free, high-nickel layered positive electrode material. This washing method can reduce the segregation and dissolution of transition metal elements in the positive electrode material during the water washing process while removing residual alkali. In addition, the method is low in cost, simple to implement, and suitable for industrial large-scale production.

[0005] In a first aspect, the present invention provides a method for preparing an isotonic water lotion, the method comprising: Synthesis of cobalt-free, high-nickel layered cathode materials; determination of the dissolution amount of transition metal ions in cobalt-free, high-nickel layered cathode materials in deionized water; Under stirring conditions, a certain amount of transition metal salt is added to deionized water according to the measured dissolution amount of transition metal ions in deionized water to prepare an isotonic water washing solution.

[0006] Preferably, the synthesis of the cobalt-free high-nickel layered cathode material is specifically: uniformly mixing a cobalt-free high-nickel layered cathode precursor with a lithium source, then fully grinding the mixture, and sintering to obtain the cobalt-free high-nickel layered cathode material.

[0007] Preferably, the chemical composition of the cobalt-free high-nickel layered cathode precursor is Ni x Mn 1-x (OH) 2; the chemical composition of the cobalt-free high-nickel layered positive electrode material is LiNi x Mn 1-x O2; where 0.8≤x<1.0.

[0008] Preferably, the lithium source includes one or more of LiOH·H2O, Li2CO3, and LiNO3; and the molar ratio of the cobalt-free high-nickel layered positive electrode precursor to the lithium source is 1:1.01 to 1:1.10.

[0009] Preferably, the sintering conditions are: pre-sintering for a period of time in an oxygen-containing atmosphere, then heating to the target temperature at a certain heating rate, and keeping the temperature for a period of time.

[0010] More preferably, the oxygen-containing atmosphere is pure oxygen or air; the pre-sintering temperature is 450-550°C, and the time is 1-3 hours; the heating rate is 1-5°C / min; the sintering temperature is 700-800°C, and the holding time is 8-16 hours.

[0011] Preferably, the molar ratio of the amount of transition metal ions dissolved in deionized water to the amount of transition metal salt added in the cobalt-free high-nickel layered positive electrode material is 1:5~1:10; the solid-liquid mass ratio of the transition metal salt to deionized water is 1:2~1:10.

[0012] In a second aspect, the present invention provides the use of the above-mentioned isotonic water washing solution in the process of removing residual alkali from cobalt-free high-nickel layered positive electrode materials.

[0013] The specific application process is as follows: under stirring conditions, the cobalt-free high-nickel layered positive electrode material is placed in the isotonic water washing solution prepared by the method described in any one of claims 1 to 7 and stirred for a certain period of time, dehydrated by suction filtration, and dried under certain conditions to obtain the cobalt-free high-nickel layered positive electrode material after the isotonic water washing solution is dealkali treated. The chemical composition of the cobalt-free high-nickel layered positive electrode material is LiNi x Mn 1-x O2; where 0.8≤x<1.0.

[0014] Preferably, the solid-liquid mass ratio of the cobalt-free high-nickel layered positive electrode to the isotonic water washing solution is 1:2~1:5; the stirring rate of the cobalt-free high-nickel layered positive electrode material in the isotonic water washing solution is 500~1500 rpm; the stirring time is 60~120s; the drying conditions are a drying temperature of 80~150°C, a drying time of 5~14 h, and a drying environment of vacuum or normal pressure.

[0015] The beneficial effects of the present invention are: The present invention measures the amount of transition metal elements dissolved in deionized water in a cobalt-free, high-nickel layered cathode material. It then selects a specific type and amount of transition metal salt to prepare an isotonic solution for washing the cobalt-free, high-nickel layered cathode material. This washing method not only removes residual alkali but also reduces the segregation and dissolution of transition metal elements in the cathode material during the washing process. Furthermore, the method is low-cost, simple to implement, and suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 LiNi after treatment with isotonic water 0.8 Mn 0.2 SEM image of O2 cathode material.

[0018] Figure 2LiNi before and after treatment with isotonic water solution 0.8 Mn 0.2 XRD pattern of O2 positive electrode material. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] The present invention provides a method for preparing an isotonic water lotion, comprising the following steps: Step (1), cobalt-free high nickel layered positive electrode (LiNi x Mn 1-x O2, x ≥ 0.8).

[0021] The cobalt-free high-nickel layered positive electrode precursor is evenly mixed with a lithium source, and then the mixture is fully ground and sintered to obtain a high-nickel ternary positive electrode material.

[0022] As a preference, the chemical composition of the cobalt-free high-nickel layered cathode precursor in step (1) is Ni x Mn 1-x (OH)2; where 0.8≤x<1.0; Preferably, the lithium source in step (1) comprises one or more of LiOH·H2O, Li2CO3, and LiNO3; As a preference, the chemical composition of the cobalt-free high-nickel layered cathode material in step (1) is LiNi x Mn 1-x O2; where 0.8≤x<1.0; Preferably, the molar ratio of the cobalt-free high-nickel layered cathode precursor to the lithium source in step (1) is 1:1.01 to 1:1.10; Preferably, the sintering conditions in step (1) are to pre-sinter for a period of time in an oxygen-containing atmosphere, then heat to the target temperature at a certain heating rate, and keep the temperature for a period of time; More preferably, the oxygen-containing atmosphere is pure oxygen or air; the pre-sintering temperature is 450-550°C, the time is 1-3 hours; the heating rate is 1-5°C / min; the sintering temperature is 700-800°C, and the holding time is 8-16 hours; Step (2), determination of cobalt-free high nickel layered cathode material (LiNi x Mn 1-x The dissolution amount of transition metal ions in deionized water (O2, x≥0.8).

[0023] Preferably, the method for determining the amount of transition metal ions dissolved is as follows: the cobalt-free high-nickel layered positive electrode material is placed in deionized water at a solid-liquid mass ratio of 1:3 to 1:5, and the stirring rate is maintained at 1000 rpm and stirred uniformly for 90 seconds; the ion concentration is determined by one of the ICP method, the conductivity method, and the chemical titration method.

[0024] Step (3): Under certain stirring conditions, according to the ion dissolution amount measured in step (2), a certain amount of transition metal salt is added to deionized water to prepare an isotonic water washing solution.

[0025] Preferably, the transition metal salt includes one or more of NiSO4·6H2O, MnSO4·H2O, Ni(NO3)2·6H2O, Mn(NO3)2·4H2O, NiCl·6H2O, and MnCl·4H2O; Preferably, the molar ratio of the measured ion dissolution amount to the amount of transition metal salt added is 1:5 to 1:10; Preferably, the solid-liquid mass ratio of the transition metal salt to deionized water is 1:2 to 1:10; Preferably, the stirring rate is 100-1000 rpm.

[0026] The present invention also provides the use of the isotonic water washing solution in the process of removing residual alkali from cobalt-free high-nickel layered positive electrode materials.

[0027] The specific application process is as follows: under stirring conditions, the cobalt-free high-nickel layered positive electrode material synthesized in step (1) is placed in the isotonic water washing solution prepared in step (3) and stirred for a certain period of time, dehydrated by suction filtration, and dried under certain conditions to obtain the cobalt-free high-nickel layered positive electrode material after the isotonic water washing solution is dealkali treated.

[0028] Preferably, the solid-to-liquid mass ratio of the cobalt-free high-nickel layered positive electrode to the isotonic water washing solution is 1:2 to 1:5; Preferably, the stirring rate of the cobalt-free high-nickel layered positive electrode in the isotonic water washing solution is 500-1500 rpm; the stirring time is 60-120 s; Preferably, the drying conditions are a drying temperature of 80-150° C., a drying time of 5-14 h, and a drying environment of vacuum or normal pressure.

[0029] The present invention is described in detail below.

[0030] Example 1: Preparation method of an isotonic water washing solution and its application in removing residual alkali from cobalt-free high-nickel layered positive electrode materials Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.8 Mn 0.2O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.8 Mn 0.2 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0031] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.8 Mn 0.2 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a stirring rate of 1000 rpm for 90 seconds, and the filtrate was obtained by suction filtration. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0032] Step (3), preparation of an isotonic water wash solution. Under a stirring rate of 500 rpm, the transition metal salt MnSO4·H2O was added to deionized water at a solid-liquid mass ratio of 1:5, based on a molar ratio of the measured ion dissolution amount to the amount of transition metal salt added of 1:6, to form an isotonic water wash solution.

[0033] Step (4), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in the isotonic water washing solution prepared in step (3) at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 1000 rpm and stirring at a constant speed for 90s, dehydrating by suction filtration, and drying in a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after dealkali treatment of the isotonic water washing solution.

[0034] Figure 1 The LiNi after treatment with isotonic water solution in Example 1 0.8 Mn 0.2 SEM image of the O2 cathode material. The SEM image shows no significant difference from that of conventional cobalt-free, high-nickel layered cathode materials, indicating that the isotonic water treatment does not damage the surface structure of the cobalt-free, high-nickel layered cathode material.

[0035] Figure 2 The LiNi before and after treatment with the isotonic water solution in Example 1 0.8 Mn 0.2 XRD pattern of the O2 cathode material. The XRD pattern shows no significant difference from that of conventional cobalt-free, high-nickel layered cathode materials, indicating that the isotonic water washing solution treatment does not destroy the crystal structure of the cobalt-free, high-nickel layered cathode material.

[0036] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. -and CO3 2- Content, OH before washing - The content is 0.36 wt%, CO3 2- The content is 0.25 wt%, and the OH after treatment with isotonic water solution - The content is 0.19 wt%, CO3 2- The content is 0.11 wt%, and the dealkali effect is significant compared with that before washing.

[0037] Example 2: Preparation method of an isotonic water washing solution and its application in removing residual alkali from cobalt-free high-nickel layered positive electrode materials Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.9 Mn 0.1 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.9 Mn 0.1 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0038] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.9 Mn 0.1 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a stirring rate of 1000 rpm for 90 seconds, and the filtrate was obtained by suction filtration. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0039] Step (3), preparation of an isotonic water wash solution. Under a stirring rate of 500 rpm, according to the molar ratio of the measured ion dissolution amount to the amount of transition metal salt added being 1:8, the transition metal salts NiSO4·6H2O and MnSO4·H2O were added to deionized water at a solid-liquid mass ratio of 1:5 to form an isotonic water wash solution.

[0040] Step (4), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in the isotonic water washing solution prepared in step (3) at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 1000 rpm and stirring at a constant speed for 90s, dehydrating by suction filtration, and drying in a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after dealkali treatment of the isotonic water washing solution.

[0041] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - and CO32- Content, OH before washing - The content is 0.37 wt%, CO3 2- The content is 0.27 wt%, and the OH after treatment with isotonic water solution - The content is 0.21 wt%, CO3 2- The content is 0.12 wt%, and the dealkali effect is significant compared with that before washing.

[0042] Example 3: Preparation method of an isotonic water washing solution and its application in removing residual alkali from cobalt-free high-nickel layered positive electrode materials Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.8 Mn 0.2 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.8 Mn 0.2 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0043] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.8 Mn 0.2 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a constant stirring rate of 900 rpm for 110 seconds, and filtered to obtain a filtrate. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0044] Step (3), preparation of an isotonic water wash solution. Under a stirring rate of 500 rpm, the transition metal salt MnSO4·H2O was added to deionized water at a solid-liquid mass ratio of 1:5, based on a molar ratio of the measured ion dissolution amount to the amount of transition metal salt added of 1:6, to form an isotonic water wash solution.

[0045] Step (4), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in the isotonic water washing solution prepared in step (3) at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 900 rpm and stirring uniformly for 110 seconds, dehydrating by suction filtration, and drying in a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after dealkali treatment of the isotonic water washing solution.

[0046] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - and CO3 2-Content, OH before washing - The content is 0.34 wt%, CO3 2- The content is 0.23 wt%, and the OH after treatment with isotonic water solution - The content is 0.17 wt%, CO3 2- The content is 0.09 wt%, and the dealkali effect is significant compared with that before washing.

[0047] Example 4: Preparation method of an isotonic water washing solution and its application in removing residual alkali from cobalt-free high-nickel layered positive electrode materials Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.9 Mn 0.1 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.9 Mn 0.1 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0048] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.9 Mn 0.1 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:2, stirred at a constant stirring rate of 800 rpm for 120 seconds, and filtered to obtain a filtrate. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by the ICP method.

[0049] Step (3), preparation of an isotonic water wash solution. Under a stirring rate of 500 rpm, according to the molar ratio of the measured ion dissolution amount to the amount of transition metal salt added being 1:8, the transition metal salts NiSO4·6H2O and MnSO4·H2O were added to deionized water at a solid-liquid mass ratio of 1:5 to form an isotonic water wash solution.

[0050] Step (4), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in the isotonic water washing solution prepared in step (3) at a solid-liquid mass ratio of 1:2, maintaining a stirring rate of 800 rpm and stirring uniformly for 120s, dehydrating by suction filtration, and drying in a vacuum environment at 150°C for 12 hours to obtain a cobalt-free high-nickel layered positive electrode material after dealkali treatment of the isotonic water washing solution.

[0051] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - and CO3 2-Content, OH before washing - Content is 0.35 wt%, CO3 2- The content is 0.24 wt%, and the OH after treatment with isotonic water solution - Content is 0.18 wt%, CO3 2- The content is 0.10 wt%, and the dealkali effect is significant compared with that before washing.

[0052] Comparative Example 1: Deionized water washing of cobalt-free high-nickel layered positive electrode material to remove residual alkali Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.8 Mn 0.2 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.8 Mn 0.2 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0053] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.8 Mn 0.2 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a stirring rate of 1000 rpm for 90 seconds, and the filtrate was obtained by suction filtration. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0054] Step (3), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in deionized water at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 1000 rpm and stirring uniformly for 90 seconds, dehydrating by suction filtration, and drying under a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after water washing and dealkali treatment.

[0055] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - 、CO3 2- , Ni, Mn content, OH before washing - The content is 0.34 wt%, CO3 2- The content is 0.26 wt%, and the OH content after washing is 0.26 wt%. - The content is 0.17 wt%, CO3 2-The content of Mn was 0.12 wt %, which is consistent with the alkali removal effect after treatment with an isotonic water wash. In the comparative example, the Mn content decreased significantly after water washing (e.g., Mn decreased from 11.70 wt % to 8.28 wt % in Comparative Example 1), while the Mn content changed little after using an isotonic water wash in the example (e.g., Mn decreased from 11.70 wt % to 11.65 wt % in Example 1), indicating that treatment with an isotonic water wash can effectively reduce Mn dissolution.

[0056] Comparative Example 2: Deionized water washing of cobalt-free high-nickel layered positive electrode material to remove residual alkali Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.9 Mn 0.1 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.9 Mn 0.1 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0057] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.9 Mn 0.1 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a stirring rate of 1000 rpm for 90 seconds, and the filtrate was obtained by suction filtration. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0058] Step (3), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in deionized water at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 1000 rpm and stirring uniformly for 90 seconds, dehydrating by suction filtration, and drying under a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after water washing and dealkali treatment.

[0059] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - 、CO3 2- , Ni, Mn content, OH before washing - The content is 0.36 wt%, CO3 2- The content is 0.25 wt%, and the OH content after washing is 0.25 wt%. - The content is 0.19 wt%, CO3 2-The content of Mn was 0.11 wt %, which is consistent with the alkali removal effect after treatment with an isotonic water wash. In the comparative example, the Mn content decreased significantly after water washing (e.g., Mn decreased from 5.85 wt % to 4.79 wt % in Comparative Example 1), while the Mn content changed little after using an isotonic water wash in the example (e.g., Mn decreased from 5.85 wt % to 5.77 wt % in Example 1), indicating that treatment with an isotonic water wash can effectively reduce Mn dissolution.

[0060] Comparative Example 3: Deionized water washing of cobalt-free high-nickel layered positive electrode material to remove residual alkali Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.8 Mn 0.2 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.8 Mn 0.2 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0061] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.8 Mn 0.2 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:3, stirred at a constant stirring rate of 900 rpm for 110 seconds, and filtered to obtain a filtrate. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by ICP method.

[0062] Step (3), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in deionized water at a solid-liquid mass ratio of 1:3, maintaining a stirring rate of 900 rpm and stirring uniformly for 110 seconds, dehydrating by suction filtration, and drying under a vacuum environment at 120°C for 10 hours to obtain a cobalt-free high-nickel layered positive electrode material after water washing and dealkali treatment.

[0063] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - 、CO3 2- , Ni, Mn content, OH before washing - The content is 0.38 wt%, CO3 2- The content is 0.22 wt%, and the OH content after washing is 0.22 wt%. - Content is 0.20 wt%, CO3 2-The content of Mn was 0.08 wt %, which is consistent with the alkali removal effect after treatment with an isotonic water wash. In the comparative example, the Mn content decreased significantly after water washing (e.g., Mn decreased from 11.70 wt % to 7.37 wt % in Comparative Example 1), while the Mn content changed little after using an isotonic water wash in the example (e.g., Mn decreased from 11.70 wt % to 11.34 wt % in Example 1), indicating that treatment with an isotonic water wash can effectively reduce Mn dissolution.

[0064] Comparative Example 4: Deionized water washing of cobalt-free high-nickel layered positive electrode material to remove residual alkali Step (1) using a solid phase synthesis method to prepare a cobalt-free high nickel layered cathode material (chemical composition is LiNi 0.9 Mn 0.1 O2). Cobalt-free high nickel layered cathode precursor (chemical composition is Ni 0.9 Mn 0.1 (OH)2) was mixed with a lithium source (LiOH·H2O) at a molar ratio of 1:1.05. The mixture was thoroughly ground in a mortar and then pre-sintered at 480°C for 2 hours in a pure oxygen atmosphere. The temperature was then increased to 750°C at a rate of 2°C / min and sintered for 10 hours.

[0065] Step (2), determination of cobalt-free high nickel layered cathode material (LiNi 0.9 Mn 0.1 The amount of transition metal ions dissolved in deionized water was determined by measuring the amount of transition metal ions dissolved in deionized water. The cobalt-free, high-nickel layered cathode material synthesized in step (1) was placed in deionized water at a solid-liquid mass ratio of 1:2, stirred at a constant stirring rate of 800 rpm for 120 seconds, and filtered to obtain a filtrate. The amount of transition metal ions dissolved in the cobalt-free, high-nickel layered cathode material was determined by the ICP method.

[0066] Step (3), placing the cobalt-free high-nickel layered positive electrode material synthesized in step (1) in deionized water at a solid-liquid mass ratio of 1:2, maintaining a stirring rate of 800 rpm and stirring uniformly for 120s, dehydrating by suction filtration, and drying under a vacuum environment of 150°C for 12 hours to obtain a cobalt-free high-nickel layered positive electrode material after water washing and dealkali treatment.

[0067] Table 1 lists the OH values ​​of the samples before washing and after treatment with isotonic water. - 、CO3 2- , Ni, Mn content, OH before washing - The content is 0.36 wt%, CO3 2- The content is 0.23 wt%, and the OH content after washing is 0.23 wt%. - Content is 0.18 wt%, CO3 2-The content of Mn in the samples was 0.09 wt %, which is consistent with the alkali removal effect after treatment with an isotonic water wash solution. In the comparative examples, the Mn content decreased significantly after water washing (e.g., Mn decreased from 5.85 wt % to 4.25 wt % in Comparative Example 1), while the Mn content changed little after using an isotonic water wash solution in the examples (e.g., Mn decreased from 5.85 wt % to 5.21 wt % in Example 1), indicating that treatment with an isotonic water wash solution can effectively reduce Mn dissolution.

[0068] Table 1 OH content in cobalt-free high-nickel layered cathode materials after deionized water washing and isotonic water washing - 、CO3 2- , Ni, Mn content (wt.%)

[0069] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing an isotonic water lotion, characterized in that: The method comprises: Synthesis of cobalt-free, high-nickel layered cathode materials; determination of the dissolution amount of transition metal ions in cobalt-free, high-nickel layered cathode materials in deionized water; Under stirring conditions, a certain amount of transition metal salt is added to deionized water according to the measured dissolution amount of transition metal ions in deionized water to prepare an isotonic water washing solution.

2. The method according to claim 1, characterized in that The synthesis of the cobalt-free high-nickel layered positive electrode material specifically comprises: uniformly mixing a cobalt-free high-nickel layered positive electrode precursor with a lithium source, then fully grinding the mixture, and sintering to obtain the cobalt-free high-nickel layered positive electrode material.

3. The method according to claim 2, characterized in that The chemical composition of the cobalt-free high-nickel layered positive electrode precursor is Ni x Mn 1-x (OH) 2; the chemical composition of the cobalt-free high-nickel layered positive electrode material is LiNi x Mn 1-x O2; where 0.8≤x<1.

0.

4. The method according to claim 2, characterized in that The lithium source includes one or more of LiOH·H2O, Li2CO3, and LiNO3; the molar ratio of the cobalt-free high-nickel layered positive electrode precursor to the lithium source is 1:1.01 to 1:1.

10.

5. The method according to claim 2, characterized in that: The sintering conditions are as follows: pre-sintering for a period of time in an oxygen-containing atmosphere, then heating to a target temperature at a certain heating rate, and keeping the temperature for a period of time.

6. The method according to claim 5, characterized in that The oxygen-containing atmosphere is pure oxygen or air; the pre-sintering temperature is 450-550°C, and the time is 1-3 hours; the heating rate is 1-5°C / min; the sintering temperature is 700-800°C, and the holding time is 8-16 hours.

7. The method according to claim 1, characterized in that: The molar ratio of the dissolution amount of transition metal ions in the cobalt-free high-nickel layered positive electrode material in deionized water to the addition amount of transition metal salt is 1:5-1:10; the solid-liquid mass ratio of the transition metal salt to deionized water is 1:2-1:

10.

8. Use of the isotonic water washing solution prepared by the method according to any one of claims 1 to 7 in the process of removing residual alkali from cobalt-free high-nickel layered positive electrode materials.

9. The application according to claim 8, characterized in that: The specific application process is as follows: under stirring conditions, the cobalt-free high-nickel layered positive electrode material is placed in the isotonic water washing solution prepared by the method described in any one of claims 1 to 7 and stirred for a certain period of time, dehydrated by suction filtration, and dried under certain conditions to obtain the cobalt-free high-nickel layered positive electrode material after the isotonic water washing solution is dealkali treated.

10. The use according to claim 9, characterized in that: The solid-liquid mass ratio of the cobalt-free high-nickel layered positive electrode material to the isotonic water washing solution is 1:2~1:5; the stirring rate of the cobalt-free high-nickel layered positive electrode material in the isotonic water washing solution is 500~1500 rpm; the stirring time is 60~120s; the drying conditions are a drying temperature of 80~150°C, a drying time of 5~14h, and a drying environment of vacuum or normal pressure.

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