Sodium-ion battery positive electrode material precursor, preparation method and application

Abstract

The invention discloses a sodium-ion battery positive electrode material precursor, a preparation method and application, the sodium-ion battery positive electrode material precursor comprises phosphoric acid and / or pyrophosphate radical, the sodium-ion battery positive electrode material precursor comprises secondary particles composed of primary particles, the primary particles on the surfaces of the secondary particles are sheet-shaped, and the primary particles on the surfaces of the secondary particles are sheet-shaped. The positive electrode material prepared by using the material as a raw material can inherit the morphology of a sodium ion battery positive electrode material precursor, and compared with spherical primary particles and a sheet structure, the material specific surface area can be increased, more active sites are provided for sodium ion storage, permeation of an electrolyte is facilitated, an ion diffusion path is shortened, and the migration rate is increased; furthermore, the sheet-shaped primary particle structure on the surface is better in structural stability in the charging and discharging process, the structural damage caused by volume change is reduced, and the smoothness of an ion transmission channel is maintained, so that the electrochemical reaction activity of the material is improved, and the release of the battery capacity and the improvement of the cycle performance are facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a sodium ion battery positive electrode material precursor, a preparation method and application thereof. BACKGROUND

[0002] A sodium ion battery is an electrochemical energy storage technology based on sodium ions intercalating and deintercalating between positive and negative electrodes to realize energy storage and release. It is similar to lithium ion batteries in working principle, but sodium is abundant in the earth's crust, low in cost, and widely distributed, and there is no problem of lithium resource scarcity and regional concentration, showing great application potential in large-scale energy storage, low-speed electric vehicles and other fields.

[0003] In a sodium ion battery, the positive electrode material plays a key role in storing sodium ions, and its structural stability, sodium ion deintercalation ability and specific capacity have a decisive influence on the energy density, cycle life and working voltage of the battery. The positive electrode materials currently studied more include layered oxides, prussian blue analogues and polyanion compounds.

[0004] While the polyanion positive electrode material has the advantages of structural stability and good thermal safety, it has a significant defect of low chemical reaction activity. This is because the presence of strong covalent bonds in the polyanion group inhibits the deintercalation kinetics of sodium ions to some extent, resulting in slow ion migration rate during charging and discharging, and thus affecting the performance of the battery. This is also a key problem that needs to be solved in the practical application of this type of material.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a sodium ion battery positive electrode material precursor, a preparation method and application thereof, which is beneficial to improve the electrochemical reaction activity of the polyanion type sodium ion battery positive electrode material.

[0007] The present application is realized as follows:

[0008] In a first aspect, the present application provides a sodium ion battery positive electrode material precursor, which comprises phosphoric acid and / or pyrophosphate, and the sodium ion battery positive electrode material precursor comprises secondary particles composed of primary particles, and the primary particles on the surface of the secondary particles are in sheet shape.

[0009] In an optional embodiment, the secondary particles are spheroidal; optionally, the sphericity of the secondary particles is ≥0.85;

[0010] And / or, the chemical formula of the sodium ion battery positive electrode material precursor is Na q M m+n Mˋw P x O y ; zH2O; wherein, M is one or more of Fe, Ni, Co, Mn; M' is one or more of transition metal elements other than M, Mg, Ca, Sr, Al; m represents the content of M 2+ ; n represents the content of M 3+ ; and q, m, n, w, x, y are values that can make the chemical formula maintain charge balance;

[0011] And / or, the chemical formula of the sodium ion battery cathode material precursor is Na q Fe m+n M' M w (P x-2 O y-7 )P2O7·zH2O.

[0012] In an optional embodiment, the values of q, m, n, w, x, y in the chemical formula satisfy the following requirements: 0≤m / (m+n)≤0.35, 0≤w / (m+n)≤0.1, 0.32≤q / (m+n+w)≤0.70, 0.70≤(m+n+w) / x≤0.82, 0≤z / (m+n+w)≤10.

[0013] In an optional embodiment, the average width of the primary particles is 80-160nm;

[0014] And / or, the primary particles on the surface of the secondary particles are intercalated growth;

[0015] And / or, the D50 of the secondary particles is 5μm-50μm;

[0016] And / or, the Span value of the sodium ion battery cathode material precursor is 0.8-1.4.

[0017] In an optional embodiment, the specific surface area of the sodium ion battery cathode material precursor is 5m 2 / g-18m 2 / g;

[0018] And / or, the tap density of the sodium ion battery cathode material precursor is 1g / cm 3 -1.5g / cm 3 .

[0019] In a second aspect, the present application provides a preparation method of the sodium ion battery cathode material precursor according to any one of the preceding embodiments, comprising:

[0020] adding a phosphorus source and a metal source to the reactor A containing the first bottom solution at a preset speed to perform a first co-precipitation, collecting the overflow to obtain slurry A when the reactor A starts to overflow, the phosphorus source comprising pyrophosphate and / or phosphate, the metal source comprising Na + , the metal element of the metal source being selected from one or more of transition metal elements, Mg, Ca, Sr, Al;

[0021] collecting part of the slurry A and placing it in the reactor B as a second bottom solution;

[0022] adding the slurry A, an oxidizing agent and a pH adjuster to the reactor B containing the second bottom solution to perform a second co-precipitation to obtain slurry B;

[0023] performing solid-liquid separation, washing and drying on the slurry B to obtain the sodium ion battery positive electrode material precursor.

[0024] In optional embodiments, at least one of the following features is satisfied:

[0025] a. the temperature of the first co-precipitation is 50-60°C;

[0026] b. the first co-precipitation is performed under stirring at a speed of 300-600 rpm;

[0027] c. the temperature of the second co-precipitation is 50-60°C

[0028] d. the pH of the second co-precipitation is 3-4;

[0029] e. the second co-precipitation is performed under stirring at a speed of 300-600 rpm;

[0030] f. the concentration of phosphorus element in the phosphorus source is 1-1.5 mol / L;

[0031] g. the concentration of metal ion in the metal source is 1.5-2 mol / L;

[0032] h. the oxidizing agent comprises hydrogen peroxide solution, and optionally, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 7-9 mol / L;

[0033] i. the at least one selected from hydrochloric acid, acetic acid and sulfuric acid, and optionally, the concentration of the pH adjuster is 0.5-1.5 mol / L;

[0034] j. in the second co-precipitation, the flow rate of the slurry A is the sum of the flow rates of the first phosphorus source and the metal source in the first co-precipitation step.

[0035] In an optional embodiment, the preparation method satisfies at least one of the following characteristics:

[0036] A. The flow rate of the metal source is (3%-5%) / h of the volume of the first co-precipitation reactor;

[0037] B. The flow rate of the phosphorus source is (7%-8%) / h of the volume of the first co-precipitation reactor;

[0038] C. The flow rate of the oxidizing agent is (0.5%-2%) / h of the volume of the second co-precipitation reactor;

[0039] D. The metal element is selected from one or more of Fe, Ni, Co, Mn, Mg, Ca, Sr, and Al.

[0040] In a third aspect, the present application provides a sodium-ion battery positive electrode material, wherein the raw material of the sodium-ion battery positive electrode material comprises the sodium-ion battery positive electrode material precursor or the sodium-ion battery positive electrode material precursor prepared by the preparation method of the sodium-ion battery positive electrode material precursor according to any one of the preceding embodiments.

[0041] In a fourth aspect, the present application provides a sodium-ion battery comprising the sodium-ion battery positive electrode material according to the preceding embodiments.

[0042] The present application has the following beneficial effects:

[0043] The primary particles of the sodium-ion battery positive electrode material precursor in the present application are in a sheet shape. The positive electrode material prepared by using the sodium-ion battery positive electrode material precursor in the present application as a raw material can inherit the morphology of the sodium-ion battery positive electrode material precursor. Compared with spherical primary particles, the sheet structure can increase the specific surface area of the material, provide more active sites for sodium-ion storage, facilitate the penetration of electrolyte, shorten the ion diffusion path, and accelerate the migration rate. Further, the sheet-shaped primary particle structure has better structural stability during the charging and discharging process, reduces the structural damage caused by volume change, maintains the unobstructed ion transmission channel, thereby being conducive to improving the electrochemical reaction activity of the material, and being conducive to the release of battery capacity and the improvement of cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0045] Figure 1SEM image (left) of the sodium-ion battery cathode material precursor prepared in Example 1 at 1K magnification and a local magnified image (right) at 50K magnification;

[0046] Figure 2 SEM image of the sodium-ion battery cathode material precursor prepared in Example 2 at 1K magnification;

[0047] Figure 3 Local magnified image of the sodium-ion battery cathode material precursor prepared in Example 3 at 50K magnification;

[0048] Figure 4 SEM image of the sodium-ion battery cathode material precursor prepared in Comparative Example 1 at 1K magnification. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or manufacturer recommended conditions are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0050] In the present application, the morphology of the sodium-ion battery cathode material precursor is characterized by a scanning electron microscope (SEM).

[0051] In the present application, the average width of the primary particles on the surface of the precursor is obtained by taking N (N≥5) primary particles in the SEM image and calculating the average width of the N primary particles.

[0052] In the present application, D50 refers to the particle size corresponding to the cumulative particle size distribution percentage of the precursor reaching 50%.

[0053] In the present application, the sphericity is calculated by the ratio of the quasi-circle radius to the minimum circumscribed circle radius, wherein the quasi-circle radius is the ratio of the area of the secondary particle detected in the SEM image to pi, and the minimum circumscribed circle radius is the radius of the smallest circle that can surround the secondary particle.

[0054] In the present application, Span and particle size are tested by a Malvern 3000 laser particle size analyzer, and the reference standard is GB / T 19077-2016.

[0055] In the present application, the test of TD refers to the standard GB / T 5162-2021 Metal Powder Vibration Density Determination.

[0056] In this invention, the specific surface area is determined according to GB / T 19587-2017 Gas Adsorption BET Method for Solid Substances.

[0057] In a first aspect, the present invention provides a precursor for a sodium-ion battery cathode material, the precursor comprising phosphoric acid and / or pyrophosphate, the sodium-ion battery cathode material comprising secondary particles composed of primary particles, wherein the primary particles on the surface of the secondary particles are in the form of flakes.

[0058] The primary particles of the sodium-ion battery cathode material precursor in this invention are plate-shaped. The cathode material prepared using the sodium-ion battery cathode material precursor in this application as raw material can inherit the morphology of the sodium-ion battery cathode material precursor. Compared with spherical primary particles, the plate-shaped structure can increase the specific surface area of ​​the material, provide more active sites for sodium ion storage, facilitate electrolyte penetration, shorten the ion diffusion path, and accelerate the migration rate. Furthermore, the surface plate-shaped primary particle structure has better structural stability during charge and discharge, reduces structural damage caused by volume changes, maintains unobstructed ion transport channels, thereby improving the electrochemical reaction activity of the material and facilitating the release of battery capacity and the improvement of cycle performance.

[0059] In an optional embodiment, the secondary particles are spherical; optionally, the sphericity of the secondary particles is ≥0.85, for example, it can be any value greater than 0.85, such as 0.85, 0.87, 0.89, 0.91, 0.93, 0.95, 0.97, 0.99, 1.0. The spherical shape of the secondary particles results in uniform stress distribution during charging and discharging, reducing cracks and breakage, and improving the structural stability of the material. Higher sphericity of the secondary particles is beneficial for increasing the tap density of the material and enhancing cycle stability.

[0060] In an optional embodiment, the general chemical formula of the polyanionic sodium-ion battery cathode material precursor is Na. q M m+n Mˋ w P x O y ·zH₂O; where M is one or more of Fe, Ni, Co, and Mn; Mˋ is one or more of transition metal elements other than M, Mg, Ca, Sr, and Al; m represents M 2+ The content of M, n represents M 3+ The content of , and the values ​​of q, m, n, w, x, y are such that the chemical formula can maintain charge balance;

[0061] And / or, the general chemical formula of the sodium-ion battery cathode material precursor is Na. q Fe m+n Mˋ w (P x-2 Oy-7 )P2O7·zH2O.

[0062] In an optional embodiment, the values of q, m, n, w, x, y in the chemical formula satisfy the following requirements: 0≤m / (m+n)≤0.35, 0≤w / (m+n)≤0.1, 0.32≤q / (m+n+w)≤0.70, 0.70≤(m+n+w) / x≤0.82, 0≤z / (m+n+w)≤10.

[0063] In an optional embodiment, the average width of the primary particles is 80-160 nm, for example, can be 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, or any value between 80-160 nm. The average width of the flaky primary particles within the appropriate range further facilitates the full and rapid infiltration of the electrolyte into the sodium-ion battery anode material prepared therefrom, improves the electrochemical reactivity, and is conducive to the capacity.

[0064] In an optional embodiment, the primary particles on the surface of the secondary particles are intercalated growth; the flaky primary particles grow along the surface of the secondary particles and form a continuous conductive network, which reduces the electron transport resistance and improves the conductivity of the material.

[0065] In an optional embodiment, the D50 of the secondary particles is 5 μm-50 μm, for example, can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value between 5 μm-50 μm. Optionally, the D50 of the secondary particles is 15 μm-45 μm. The D50 of the secondary particles within the appropriate range is conducive to balancing the capacity and cycle performance of the prepared anode material.

[0066] In an optional embodiment, the Span value of the sodium-ion battery anode material precursor is 0.8-1.4, for example, can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or any value between 0.8-1.4. Under this condition, the sodium-ion battery anode material precursor particles are packed more closely, the tap density is higher, which is conducive to the preparation of a sodium-ion battery anode material with a higher tap density, thereby improving the energy density of the battery.

[0067] In an optional embodiment, the specific surface area of the sodium-ion battery anode material precursor is 5 m 2 / g-18 m 2 / g, for example, can be 5 m2 / g, 7 m2 / g, 9 m2 / g, 11 m2 / g, 13 m2 / g, 15 m2 / g, 17 m2 / g, 18 m2 / g, or any value between 5 m 2 / g-18 m2 The tap density of the sodium-ion battery cathode material precursor is any value between 0.8 g / cm3and 1.5 g / cm3; the sodium-ion battery cathode material precursor has a suitable specific surface area, and the sheet-like primary particles are intercalated to grow into more open pores, which is beneficial to full contact with electrolyte, improves the transmission rate, is beneficial to capacity exertion, and can provide more Na+adsorption sites.

[0068] In an optional embodiment, the tap density of the sodium-ion battery cathode material precursor is 1 g / cm3. 3 -1.5 g / cm3 3 , for example, can be 1.0 g / cm3, 1.1 g / cm3, 1.2 g / cm3, 1.3 g / cm3, 1.4 g / cm3, 1.5 g / cm3or 1 g / cm3 3 -1.5 g / cm3 3 , and the increase in tap density is beneficial to the increase in battery energy density.

[0069] In a second aspect, the present application provides a preparation method of the sodium-ion battery cathode material precursor according to any one of the preceding embodiments, comprising:

[0070] The phosphorus source and the metal source are added to the reaction kettle A containing the first bottom liquid at a preset speed to perform primary co-precipitation, and when the reaction kettle A starts to overflow, the overflow material is collected to obtain slurry A, the phosphorus source includes pyrophosphate and / or phosphate, and the phosphorus source includes Na + , and the metal element of the metal source is selected from one or more of transition metal elements, Mg, Ca, Sr and Al;

[0071] Part of the slurry A is collected and placed in the reaction kettle B as a second bottom liquid;

[0072] The slurry A, the oxidizing agent and the pH adjusting agent are added to the reaction kettle B containing the second bottom liquid to perform secondary co-precipitation, and slurry B is obtained;

[0073] The slurry B is subjected to solid-liquid separation, washing and drying to obtain the sodium-ion battery cathode material precursor.

[0074] In the present application, the sodium-ion battery cathode material precursor is prepared by the method of two-kettle series co-precipitation, and the sodium-ion battery cathode material precursor described above can be obtained, which comprises secondary particles composed of sheet-like primary particles.

[0075] In an optional embodiment, the phosphorus source is selected from at least one of sodium pyrophosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate and trisodium phosphate.

[0076] In an optional embodiment, at least one of the following characteristics is met:

[0077] a. the temperature of the primary co-precipitation is 50-60 °C, such as 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, or any value in between 50-60 °C;

[0078] b. the primary co-precipitation is performed under stirring at a speed of 300-600 rpm, such as 300 rpm, 330 rpm, 360 rpm, 390 rpm, 420 rpm, 450 rpm, 480 rpm, 510 rpm, 540 rpm, 570 rpm, 600 rpm, or any value in between 300-600 rpm;

[0079] c. the temperature of the secondary co-precipitation is 50-60 °C, such as 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, or any value in between 50-60 °C;

[0080] d. the pH of the secondary co-precipitation is 3-4, such as 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, or any value in between 3-4;

[0081] e. the secondary co-precipitation is performed under stirring at a speed of 300-600 rpm, such as 300 rpm, 330 rpm, 360 rpm, 390 rpm, 420 rpm, 450 rpm, 480 rpm, 510 rpm, 540 rpm, 570 rpm, 600 rpm, or any value in between 300-600 rpm;

[0082] f. the concentration of phosphorous in the phosphorous source is 1-1.5 mol / L, such as 1.0 mol / L, 1.05 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.25 mol / L, 1.3 mol / L, 1.35 mol / L, 1.4 mol / L, 1.45 mol / L, 1.5 mol / L, or any value in between 1-1.5 mol / L;

[0083] g. the concentration of metal ions in the metal source is 1.5-2 mol / L, such as 1.5 mol / L, 1.55 mol / L, 1.6 mol / L, 1.65 mol / L, 1.7 mol / L, 1.75 mol / L, 1.8 mol / L, 1.85 mol / L, 1.9 mol / L, 1.95 mol / L, 2.0 mol / L, or any value in between 1.5-2 mol / L;

[0084] h. the oxidizing agent comprises a hydrogen peroxide solution, optionally, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 7 mol / L-9 mol / L, for example 7.0 mol / L, 7.2 mol / L, 7.4 mol / L, 7.6 mol / L, 7.8 mol / L, 8.0 mol / L, 8.2 mol / L, 8.4 mol / L, 8.6 mol / L, 8.8 mol / L, 9.0 mol / L, or any value between 7 mol / L-9 mol / L;

[0085] i. the pH adjusting agent is selected from at least one of hydrochloric acid, acetic acid, sulfuric acid, optionally, the concentration of the pH adjusting agent is 0.5 mol / L-1.5 mol / L, for example 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or any value between 0.5 mol / L-1.5 mol / L;

[0086] j. in the secondary co-precipitation, the flow rate of slurry A is the sum of the flow rates of the phosphorus source and the metal source in the primary co-precipitation step.

[0087] In optional embodiments, the preparation method satisfies at least one of the following characteristics:

[0088] A. the flow rate of the metal source is (3%-5%) / h of the volume of the primary co-precipitation reactor, for example 3% / h, 3.2% / h, 3.4% / h, 3.6% / h, 3.8% / h, 4.0% / h, 4.2% / h, 4.4% / h, 4.6% / h, 4.8% / h, 5% / h, or any value between 3%-5% / h;

[0089] B. the flow rate of the phosphorus source is (7%-8%) / h of the volume of the primary co-precipitation reactor, for example 7% / h, 7.1% / h, 7.2% / h, 7.3% / h, 7.4% / h, 7.5% / h, 7.6% / h, 7.7% / h, 7.8% / h, 7.9% / h, 8% / h, or any value between 7%-8% / h;

[0090] C. the flow rate of the oxidizing agent is (0.5%-2%) / h of the volume of the secondary co-precipitation reactor, for example 0.5% / h, 0.6% / h, 0.7% / h, 0.8% / h, 0.9% / h, 1.0% / h, 1.1% / h, 1.2% / h, 1.3% / h, 1.4% / h, 1.5% / h, 1.6% / h, 1.7% / h, 1.8% / h, 1.9% / h, 2% / h, or any value between 0.5%-2% / h;

[0091] D. the metal element is selected from one or more of Fe, Ni, Co, Mn, Mg, Ca, Sr, Al.

[0092] The present application controls the reaction conditions to control the supersaturation coefficient in the system, thereby affecting the growth interface and growth rate of the primary particles, and finally forming flaky surface primary particles.

[0093] In a third aspect, the present application provides a sodium-ion battery cathode material, raw materials of the sodium-ion battery cathode material comprising the sodium-ion battery cathode material precursor or the sodium-ion battery cathode material precursor prepared by the preparation method of the sodium-ion battery cathode material precursor according to any one of the preceding embodiments.

[0094] In a fourth aspect, the present application provides a sodium-ion battery comprising the sodium-ion battery cathode material according to the preceding embodiments.

[0095] The features and performances of the present application are further described in detail below in combination with embodiments.

[0096] Example 1

[0097] The present embodiment provides a preparation method of a sodium-ion battery cathode material precursor, comprising the following steps:

[0098] A ferrous sulfate solution with a ferrous ion concentration of 1.67 mol / L, a sodium pyrophosphate solution with a phosphorus concentration of 1.19 mol / L, a hydrogen peroxide solution with a concentration of 8.1 mol / L, and a dilute sulfuric acid solution with a concentration of 1.14 mol / L are prepared.

[0099] In the reaction kettle A, 50 L of water is added, the reaction temperature is set to 55℃, the stirring speed is set to 500 r / min, ferrous sulfate and sodium pyrophosphate are introduced, and nitrogen gas is introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution are introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content is formed. When the slurry in the reaction kettle reaches the upper limit of the volume, it starts to overflow into the reaction kettle B, and part of the slurry A is collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the liquid pH to 3.5, and the flow rate of the hydrogen peroxide solution is 1.2% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to drying, crushing and packaging processes to obtain a sodium-ion battery cathode material precursor with an iron-phosphorus ratio of 0.726. The SEM image is shown in Figure 1 As can be seen from the figure, the primary particles on the surface of the secondary particles are flaky and intercalated along the surface of the secondary particles, and the secondary particles of the precursor are spherical.

[0100] Example 2:

[0101] The embodiment provides a preparation method of a sodium ion battery positive electrode material precursor, and comprises the following steps:

[0102] A ferrous sulfate solution with a ferrous ion concentration of 1.67 mol / L, a sodium pyrophosphate solution with a phosphorus concentration of 1.19 mol / L, a hydrogen peroxide solution with a concentration of 8.1 mol / L and a dilute sulfuric acid solution with a concentration of 1.14 mol / L are prepared.

[0103] 50 L of clean water is added into the reaction kettle A, the reaction temperature is set to 60 DEG C, the stirring speed is set to 500 r / min, the ferrous sulfate and the sodium pyrophosphate are fed in, and nitrogen is fed in as a protective gas; the ferrous sulfate solution and the sodium pyrophosphate solution are fed in at a rate of 4 % / h and 7.6 % / h of the volume of the reaction kettle A respectively, and a slurry A with a certain solid content is generated after a co-precipitation reaction; when the slurry in the reaction kettle reaches the upper limit of the volume, the slurry A is overflowed into the reaction kettle B, and part of the slurry A is collected and placed in the reaction kettle B as a bottom liquid; in the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the pH of the liquid to 4.0, and the flow rate of the hydrogen peroxide solution is 1 % / h of the volume of the reaction kettle B; when the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to a drying, crushing and packaging process to obtain a sodium ion battery positive electrode material precursor with an iron-phosphorus ratio of 0.726, and a SEM image is as shown in FIG. 1. Figure 2 As shown in the figure, the primary particles on the surface of the secondary particles are flaky and intercalated along the surface of the secondary particles, and the secondary particles of the precursor are spherical.

[0104] Embodiment 3:

[0105] The embodiment provides a preparation method of a sodium ion battery positive electrode material precursor, and comprises the following steps:

[0106] A ferrous sulfate solution with a ferrous ion concentration of 1.67 mol / L (the concentration of magnesium in the solution is 0.04 mol / L), a sodium pyrophosphate solution with a phosphorus concentration of 1.19 mol / L, a hydrogen peroxide solution with a concentration of 8.1 mol / L and a dilute sulfuric acid solution with a concentration of 1.14 mol / L are prepared.

[0107] In the reaction kettle A, 50L of clean water is added, the reaction temperature is set to 50℃, the stirring speed is 500r / min, ferrous sulfate and sodium pyrophosphate are introduced, and nitrogen is introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution are introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content is formed. When the slurry in the reaction kettle reaches the upper limit of the volume, it begins to overflow into the reaction kettle B, and part of the slurry A is collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the liquid pH to 3.0. The flow rate of the hydrogen peroxide solution is 1.5% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to drying, crushing and packaging processes to obtain a sodium-ion battery positive electrode material precursor with an iron-phosphorus ratio of 0.726. The SEM image is shown in Figure 3

[0108] Example 4:

[0109] The present embodiment provides a method for preparing a sodium-ion battery positive electrode material precursor, comprising the following steps:

[0110] A ferrous sulfate solution with a concentration of 1.67mol / L, a sodium pyrophosphate solution with a concentration of 1.19mol / L, a hydrogen peroxide solution with a concentration of 8.1mol / L, and a dilute sulfuric acid solution with a concentration of 1.14mol / L are prepared.

[0111] In the reaction kettle A, 50L of clean water is added, the reaction temperature is set to 50℃, the stirring speed is 500r / min, ferrous sulfate and sodium pyrophosphate are introduced, and nitrogen is introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution are introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content is formed. When the slurry in the reaction kettle reaches the upper limit of the volume, it begins to overflow into the reaction kettle B, and part of the slurry A is collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the liquid pH to 3.0. The flow rate of the hydrogen peroxide solution is 1.5% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to drying, crushing and packaging processes to obtain a sodium-ion battery positive electrode material precursor with an iron-phosphorus ratio of 0.726. The SEM image is shown in

[0112] Example 5:

[0113] The present embodiment provides a method for preparing a sodium-ion battery positive electrode material precursor, comprising the following steps:

[0114] ​A ferrous sulfate solution with a concentration of 1.67 mol / L, a sodium pyrophosphate solution with a concentration of 1.19 mol / L, an 8.1 mol / L hydrogen peroxide solution, and a 1.14 mol / L dilute sulfuric acid solution are prepared.

[0115] 50 L of clean water is added to the reaction kettle A, the reaction temperature is set to 55℃, the stirring speed is set to 300 r / min, ferrous sulfate and sodium pyrophosphate are introduced, and nitrogen gas is introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution are introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content is formed. When the slurry in the reaction kettle reaches the upper limit of the volume, it begins to overflow into the reaction kettle B. Part of the slurry A is collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the liquid pH to 3.5. The flow rate of the hydrogen peroxide solution is 1.2% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to drying, crushing, and packaging processes to obtain a sodium-ion battery positive electrode material precursor.

[0116] Example 6:

[0117] The present embodiment provides a method for preparing a sodium-ion battery positive electrode material precursor, comprising the following steps:

[0118] A ferrous sulfate solution with a concentration of 1.67 mol / L, a sodium pyrophosphate solution with a concentration of 1.19 mol / L, an 8.1 mol / L hydrogen peroxide solution, and a 1.14 mol / L dilute sulfuric acid solution are prepared.

[0119] 50 L of clean water is added to the reaction kettle A, the reaction temperature is set to 55℃, the stirring speed is set to 300 r / min, ferrous sulfate and sodium pyrophosphate are introduced, and nitrogen gas is introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution are introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content is formed. When the slurry in the reaction kettle reaches the upper limit of the volume, it begins to overflow into the reaction kettle B. Part of the slurry A is collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution are added to adjust the liquid pH to 3.5. The flow rate of the hydrogen peroxide solution is 1.2% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B is measured to be 0.726, the slurry B is filtered and washed, and then subjected to drying, crushing, and packaging processes to obtain a sodium-ion battery positive electrode material precursor.

[0120] Comparative Example 1:

[0121] The present embodiment provides a method for preparing a sodium-ion battery positive electrode material precursor, comprising the following steps:

[0122] FeSO4 solution with iron concentration of 1.67 mol / L, Na4P2O7 solution with phosphorus concentration of 1.19 mol / L, H2O2 solution with concentration of 8.1 mol / L, and dilute H2SO4 solution with concentration of 1.14 mol / L.

[0123] In the reaction kettle A, 50L of clean water was added, the reaction temperature was set to 55℃, the stirring speed was set to 500r / min, ferrous sulfate and sodium pyrophosphate were introduced, and nitrogen was introduced as a protective gas. The ferrous sulfate solution and the sodium pyrophosphate solution were introduced at a rate of 4% / h and 7.6% / h of the volume of the reaction kettle A, respectively. After the co-precipitation reaction, a slurry A with a certain solid content was formed. When the slurry in the reaction kettle reached the upper limit of the volume, it began to overflow into the reaction kettle B, and part of the slurry A was collected and placed in the reaction kettle B as the bottom liquid. In the reaction kettle B, the prepared hydrogen peroxide solution and dilute sulfuric acid solution were added to adjust the liquid pH to 5.5. The flow rate of the hydrogen peroxide solution was 0.6% / h of the volume of the reaction kettle B. When the iron-phosphorus ratio in the slurry B was measured to be 0.726, the slurry B was filtered and washed, and then subjected to drying, crushing and packaging processes to obtain a sodium-ion battery positive electrode material precursor. The SEM image of the precursor is shown in FIG. 1. As can be seen from the figure, the primary particles on the surface of the precursor are non-flaky. Figure 4

[0124] Comparative Example 2

[0125] The present comparative example provides a method for preparing a sodium-ion battery positive electrode material precursor, comprising the following steps:

[0126] FeSO4 solution with iron concentration of 1.67 mol / L, Na4P2O7 solution with phosphorus concentration of 1.19 mol / L, H2O2 solution with concentration of 8.1 mol / L, and dilute H2SO4 solution with concentration of 1.14 mol / L.

[0127] In the reaction kettle A with a volume of 100L, 50L of clean water was added. The prepared ferrous sulfate, sodium pyrophosphate solution, hydrogen peroxide solution, and dilute sulfuric acid solution were pumped into the reaction kettle at a rate of 10% / h: 19% / h: 3% / h: 0.08% / h of the volume of the reaction kettle A, respectively. At the same time, the liquid was aerated, the reaction temperature was maintained at 55℃, the stirring speed was set to 500r / min, and the solution pH was maintained at about 2.5. A slurry with a certain solid content was formed. When the slurry level reached the maximum volume of the reaction kettle, it overflowed into the material bucket. The overflowed material was filtered and washed, and then subjected to drying, crushing and packaging processes to obtain a sodium-ion battery positive electrode material precursor. The primary particles on the surface of the precursor were spherical particles.

[0128] Test Example

[0129] ​The positive electrode material precursors prepared in the above examples and comparative examples were tested, and the results are shown in Table 1. The positive electrode materials were prepared using the precursors as raw materials, and the batteries were assembled and the performance of the batteries was tested, including the following steps:

[0130] Preparation of the positive electrode material: all examples and comparative examples were mixed with a sodium source and a carbon source in a ratio of n(Na) / n(precursor) = 1.01 and m(carbon source) / m(precursor) = 0.1, and then sintered at 500℃ for 10h under a nitrogen atmosphere at a temperature rising rate of 2℃ / min, so that sodium was embedded into the original crystal nucleus to form a sodium iron pyrophosphate phosphate positive electrode material.

[0131] The positive electrode material was mixed with polyvinylidene fluoride and acetylene black in a mass ratio of 9:0.5:0.5, N-methyl-pyrrolidone was added, and then uniformly coated on the current collector aluminum foil as the positive electrode. After drying, in the glove box, the metal sodium sheet was used as the negative electrode, 1mol / L NaClO4 solution was used as the electrolyte, and glass fiber was used as the separator to assemble CR2032 button batteries. First, the batteries were activated by charging and discharging at a current density of 0.1C (1C = 150mAh / g) for 3 weeks, and finally charged and discharged at a current density of 1C for 50 weeks, with a charge cut-off voltage of 4.2V and a discharge cut-off voltage of 2.0V. The test results are shown in Table 2.

[0132] Table 1 Index parameters of the positive electrode material precursors of sodium ion batteries prepared in the examples and comparative examples

[0133]

[0134] Table 2 Electrochemical performance of the positive electrode material precursors of sodium ion batteries prepared in the examples and comparative examples

[0135]

[0136]

[0137] According to Tables 1 and 2, it can be seen that the comparison between Examples 1-6, Comparative Example 2 and Comparative Example 1 shows that the primary particles in the form of flakes are beneficial to the improvement of capacity and cycle performance; on the basis of the primary particles in the form of flakes, the secondary particles have a high degree of sphericity, which is beneficial to the further improvement of capacity and cycle performance.

[0138] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A sodium-ion battery cathode material precursor, characterized in that, The sodium-ion battery cathode material precursor comprises phosphoric acid and / or pyrophosphate, the sodium-ion battery cathode material precursor comprises secondary particles composed of primary particles, and the primary particles on the surface of the secondary particles are in sheet form.

2. The sodium-ion battery cathode material precursor of claim 1, wherein, The secondary particles are spherical; optionally, the sphericity of the secondary particles is ≥0.

85. And / or, the chemical formula of the sodium ion battery cathode material precursor is Na q M m+n Mˋ w P x O y ·zH2O; wherein, M is one or more of Fe, Ni, Co, Mn; Mˋ is one or more of transition metal elements other than M, Mg, Ca, Sr, Al; m represents the content of M 2+ , n represents the content of M 3+ , and the values of q, m, n, w, x, y can make the chemical formula charge balance; And / or, the chemical formula of the sodium ion battery cathode material precursor is Na q Fe m+n Mˋ w (P x-2 O y-7 )P2O7·zH2O.

3. The sodium-ion battery cathode material precursor of claim 2, wherein, In the chemical formula, the values of q, m, n, w, x, and y satisfy the following requirements: 0≤m / (m+n)≤0.35, 0≤w / (m+n)≤0.1, 0.32≤q / (m+n+w)≤0.70, 0.70≤(m+n+w) / x≤0.82, and 0≤z / (m+n+w)≤10. 4.The sodium-ion battery cathode material precursor of claim 1, wherein, The average width of the primary particles is 80-160 nm; And / or, the primary particles on the surface of the secondary particles are intercalation growth; And / or, the D50 of the secondary particles is 5 μm-50 μm; And / or, the Span value of the sodium-ion battery cathode material precursor is 0.8-1.

4.

5. The sodium-ion battery cathode material precursor of claim 1, wherein, The specific surface area of the sodium ion battery positive electrode material precursor is 5 m 2 / g-18 m 2 / g; And / or, the tap density of the sodium-ion battery cathode material precursor is 1 g / cm 3 -1.5 g / cm 3 . 6.A method for preparing a precursor of a sodium-ion battery cathode material, characterized in that, Comprise: A first bottom liquid is added to a reactor A, and a phosphorus source and a metal source are added to the reactor A at a preset speed to perform a first coprecipitation, wherein the phosphorus source comprises pyrophosphate and / or phosphate, and the metal source comprises Na + , and the metal element of the metal source is selected from one or more of transition metal elements, Mg, Ca, Sr, and Al. The collected part of the slurry A is placed in a reaction kettle B as a second bottom liquid; The slurry A, an oxidizing agent, and a pH adjuster are added to the reaction kettle B containing the second bottom liquid to perform secondary co-precipitation, and a slurry B is obtained; The slurry B is subjected to solid-liquid separation, washing, and drying to obtain the sodium-ion battery cathode material precursor.

7. The sodium-ion battery cathode material precursor of claim 6, wherein, At least one of the following characteristics is satisfied: a. The temperature of the primary co-precipitation is 50-60°C; b. The primary co-precipitation is performed under stirring at a speed of 300-600 rpm; c. The temperature of the secondary co-precipitation is 50-60°C; d. The pH of the secondary co-precipitation is 3-4; e. The secondary co-precipitation is performed under stirring at a speed of 300-600 rpm; f. The concentration of phosphorus in the phosphorus source is 1-1.5 mol / L; g. The concentration of metal ions in the metal source is 1.5-2 mol / L; h. The oxidizing agent comprises a hydrogen peroxide solution, and optionally, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 7-9 mol / L; i. The pH adjuster is selected from at least one of hydrochloric acid, acetic acid, and sulfuric acid, and optionally, the concentration of the pH adjuster is 0.5-1.5 mol / L; j. In the secondary co-precipitation, the flow rate of the slurry A is the sum of the flow rates of the phosphorus source and the metal source in the primary co-precipitation step.

8. The sodium-ion battery cathode material precursor of claim 6, wherein, At least one of the following characteristics is satisfied: A. The flow rate of the metal source is (3-5)% / h of the volume of the primary co-precipitation reaction kettle; B. The flow rate of the phosphorus source is (7-8)% / h of the volume of the primary co-precipitation reaction kettle; C. The flow rate of the oxidizing agent is (0.5-2)% / h of the volume of the secondary co-precipitation reaction kettle; D. The metal element is selected from one or more of Fe, Ni, Co, Mn, Mg, Ca, Sr, and Al.

9. A sodium-ion battery cathode material, characterized in that, The raw material of the sodium ion battery cathode material comprises the sodium ion battery cathode material precursor according to any one of claims 1-5 or the sodium ion battery cathode material precursor prepared by the preparation method of the sodium ion battery cathode material precursor according to any one of claims 6-8.

10. A sodium-ion battery, characterized in that, The sodium ion battery cathode material comprises the sodium ion battery cathode material according to claim 9.

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