Doped manganese-based prussian white positive electrode material, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a doped manganese-based Prussian white positive electrode material, and a preparation method therefor and the use thereof. The chemical general formula of the doped manganese-based Prussian white positive electrode material of the present invention is Nan-dAdMn1-xMx[Fe(CN)6]y·zH2O, wherein A is one or more of Li+, K+, Rb+, Cs+, NH4 +, Cu+ or Ag+; M is one or more of Ni2+, Fe2+, Co2+, Zn2+ or Cu2+; and 1.7≤n≤2, 0.02≤d≤0.2, 0.2≤x≤0.4, 0.9≤y<1 and 0＜z<0.8. The doped manganese-based Prussian white positive electrode material in the present invention is co-doped at the Mn site and the Na site, and using the synergistic effect of M and A doping ions can not only effectively inhibit the Jahn-Teller effect of Mn3+, but can also greatly reduce the content of crystal water in the positive electrode material, and can also have the effects of reducing lattice defects and improving lattice stability and sodium ion transmission kinetics, such that the doped manganese-based Prussian white positive electrode material has a high capacity, good rate capability and good cycling stability.

Description

A doped manganese-based Prussian white positive electrode material and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of methods or devices for directly converting chemical energy into electrical energy, and more specifically, to a doped manganese-based Prussian white positive electrode material and a preparation method and application thereof. Background Art

[0002] Although current energy storage batteries are primarily lithium-ion batteries, represented by lithium iron phosphate, limited lithium resources cannot meet the rapid development of the electric vehicle sector. Compared to lithium resources, sodium resources are more abundant and widely distributed, meaning that sodium-ion batteries are more suitable for large-scale energy storage and industrial applications. The positive electrode material is a key factor influencing the performance of sodium-ion batteries. Currently, materials suitable for sodium-ion battery positive electrode materials mainly include layered oxides, Prussian materials, and polyanion materials. Among them, Prussian white positive electrode materials, due to their rigid lattice framework and large ion channels, are more easily embedded and extracted by sodium ions. With a theoretical specific capacity of up to 170 mAh / g, they are one of the most promising sodium-ion positive electrode materials.

[0003] However, existing Prussian White cathode materials are primarily synthesized via coprecipitation or hydrothermal methods, both of which involve rapid reactions in aqueous solutions. This often results in numerous lattice defects and the presence of large amounts of crystalline water during crystal formation. These lattice defects are detrimental to the stable cycling of sodium-ion batteries. Excessive crystalline water not only reduces the sodium ion content in the cathode material but also, during charge and discharge, can easily escape from the lattice, generating side reactions with sodium salts, leading to poor cycling stability.

[0004] The existing technology mainly solves this problem through means such as element doping and regulation of the properties of crystalline water. For example, the existing technology discloses a method for preparing a manganese-based Prussian white material. By element doping and using heavy water as a synthesis medium in the synthesis process, the synergistic effect of the two is utilized to stabilize the crystalline water in the lattice, thereby improving the cycle performance; at the same time, during the synthesis process, the complexing agent sodium citrate and the surfactant sodium sulfate are introduced to improve the integrity and sodium content of the product lattice through interaction with metal ions. However, the capacity of the manganese-based Prussian white positive electrode material is relatively low (up to 124.5 mAhg), and its cycle stability and rate performance also need to be improved.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects and shortcomings of existing manganese-based Prussian white materials, such as the large number of crystal defects and high crystalline water content, which lead to low capacity, poor cycle stability and rate performance, and to provide a doped manganese-based Prussian white positive electrode material.

[0007] Another object of the present invention is to provide a method for preparing a doped manganese-based Prussian white positive electrode material.

[0008] Another object of the present invention is to provide an application of a doped manganese-based Prussian white positive electrode material in a sodium ion battery.

[0009] Another object of the present invention is to provide a positive electrode sheet comprising the above-mentioned doped manganese-based Prussian white positive electrode material.

[0010] Another object of the present invention is to provide a sodium ion battery comprising the above-mentioned doped manganese-based Prussian white positive electrode material.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention protects a doped manganese-based Prussian white positive electrode material, the chemical formula of the doped manganese-based Prussian white positive electrode material is Na n-d A d Mn 1-x M x [Fe(CN)6] y zH2O;

[0013] Where A is Li + , K + , Rb + 、Cs + NH4 + 、Cu + or Ag + One or more of; M is Ni 2+ 、Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ One or more of the following; 1.7≤n≤2, 0.02≤d≤0.2, 0.2≤x≤0.4, 0.9≤y<1, 0<z<0.8.

[0014] The doped manganese-based Prussian white positive electrode material of the present invention is co-doped at the Mn position and the Na position, and the synergistic effect of the two doping ions M and A can not only effectively inhibit the Mn 3+ The Jahn-Teller effect can also significantly reduce the crystalline water content in the positive electrode material, while also reducing lattice defects, improving lattice stability and sodium ion transport kinetics, thereby making the doped manganese-based Prussian white positive electrode material have high capacity, good rate performance and excellent cycle stability.

[0015] It should also be noted that the above Na n-d A d Mn 1-x M x[Fe(CN)6] y A in zH2O is derived from an iodide of A, and the doping position of A is the Na position; the doping position of M is the Mn position. Specifically, x may be 0.2-0.25, 0.25-0.3, 0.3-0.35, 0.35-0.40, 0.31, 0.38, 0.39, 0.30, or 0.40; d may be 0.02-0.05, 0.05-0.1, 0.15-0.2, 0.02, 0.03, 0.05, 0.06, or 0.08; preferably, z is ≤ 0.6, and specifically may be 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, or 0.6.

[0016] Preferably, the A is Li + , K + , Rb + 、Cs + NH4 + 、Cu + or Ag + At least two of which one is Li + .

[0017] Through research, it was found that when A is Li + , K + , Rb + 、Cs + NH4 + 、Cu + or Ag + At least two of which one is Li + When Li + and Na + Located at the 8c lattice interstitial point, Li + and Na + The deintercalation potential is lower than 3.6 V, that is, Li + The deintercalation of Na + The deintercalation of other monovalent positive ions (K + , Rb + 、Cs + NH4 + 、Cu + or Ag + At least one of them is located at the 24d lattice interstitial point, and the deintercalation potential is higher than 3.6V. Controlling the deintercalation potential below 3.6V can fix other monovalent positive ions in the lattice, thereby stabilizing the lattice. + , Rb + 、Cs + NH4 + 、Cu + or Ag +The presence of can not only reduce the content of lattice water, but also fix the residual lattice water in the lattice, inhibiting its escape from the lattice and side reaction with sodium salt during the charge and discharge process, thereby improving the cycle stability.

[0018] Preferably, the M is Ni 2+ 、Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ At least two of which one is Fe 2+ The study found that when M contains at least Fe 2+ When it is doped at the Mn position, it can inhibit the 3+ While the Jahn-Teller effect is taking effect, the crystal water content is further reduced.

[0019] Specifically, the doped manganese-based Prussian white positive electrode material has a monoclinic phase structure.

[0020] Specifically, the crystalline water content of the doped manganese-based Prussian white positive electrode material of the present invention is ≤4wt%; preferably, the crystalline water content of the doped manganese-based Prussian white positive electrode material is ≤3.5wt%, for example, it can be 3.0wt%, 3.1wt%, 3.2wt%, 3.3wt%, or 3.4wt%.

[0021] The present invention also protects a method for preparing the above-mentioned doped manganese-based Prussian white positive electrode material, comprising the following steps:

[0022] S1. Solution I and solution II were mixed uniformly, followed by coprecipitation reaction, an aging reaction, to obtain a suspension;

[0023] S2. The iodide of A is added to the suspension of S1, and a secondary aging reaction is performed to obtain a doped manganese-based Prussian white cathode material;

[0024] Wherein, the solution I in S1 is composed of sodium ferrocyanide and water, and the solution II is composed of a soluble divalent manganese salt, a soluble divalent M salt, sodium citrate and water;

[0025] The M in the soluble divalent M salt is Ni 2+ 、Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ One or more of; A in S2 is Li + , K + , Rb + 、Cs + NH4 + 、Cu + or Ag +One or more of the .

[0026] Optionally, the molar ratio of the sodium citrate to the mixture of the soluble divalent manganese salt and the soluble divalent M salt is (3-6):1.

[0027] Specifically, in step S1, the temperature of the coprecipitation reaction is 40-80° C.; the temperature of the primary aging reaction is 40-80° C., and the time is 2-24 hours. Carrying out the coprecipitation reaction and aging reaction under these reaction conditions is more conducive to improving the crystallinity of the product and reducing lattice defects.

[0028] Specifically, the temperature of the secondary aging reaction in step S2 is 40-80°C and the time is 2-24 hours; when the iodide of A is used as an additive for the second aging, I - Mn 3+ and M ions are oxidized to I2 (iodine), I2 and I - The reaction forms soluble I 3- , while Mn 3+ and M ions are reduced to divalent ions, A + The water molecules are squeezed out of the Prussian white lattice, which reduces the water content of the crystals. This also increases the crystallinity of the product and reduces lattice defects. After the second aging reaction, the product needs to be cooled, washed, separated, and vacuum dried.

[0029] Optionally, the concentration of sodium ferrocyanide in solution I is 0.1 to 1 mol / L. A sodium ferrocyanide solution in this concentration range can increase product crystallinity, reduce lattice defects, and improve lattice stability. Furthermore, the total concentration of the soluble divalent manganese salt and the soluble divalent M salt in solution II is 0.1 to 1 mol / L, wherein the soluble divalent manganese salt is one or more of manganese sulfate, manganese nitrate, manganese chloride, or manganese acetate; and the soluble divalent M salt is selected from at least one of its sulfate, nitrate, chloride, or acetate.

[0030] The application of the above-mentioned doped manganese-based Prussian white positive electrode material in sodium ion batteries is also within the scope of protection of the present invention.

[0031] The present invention also protects a positive electrode plate, comprising a current collector and a positive electrode active material layer disposed on at least one side of the current collector, wherein the positive electrode active material layer comprises the above-mentioned doped manganese-based Prussian white positive electrode material.

[0032] The present invention also protects a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte (which may be a solid electrolyte or a liquid electrolyte + a separator) located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises the above-mentioned doped manganese-based Prussian white positive electrode material.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] The doped manganese-based Prussian white positive electrode material of the present invention is co-doped at the Mn position and the Na position, and the synergistic effect of the two doping ions M and A can not only effectively inhibit the Mn 3+ The Jahn-Teller effect can also significantly reduce the crystalline water content in the positive electrode material, while also reducing lattice defects, improving lattice stability and sodium ion transport kinetics, thereby making the doped manganese-based Prussian white positive electrode material have high capacity, good rate performance and excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is an X-ray diffraction pattern (XRD) of the doped manganese-based Prussian white positive electrode material in Example 1.

[0036] FIG2 is a charge and discharge curve diagram of the doped manganese-based Prussian white positive electrode material in Example 1. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0038] Example 1

[0039] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0040] Na 1.72 K 0.03 Li 0.02 Mn 0.62 Fe 0.38 [Fe(CN)6] 0.94 0.51H2O.

[0041] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0042] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0043] S2. KI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0044] The above-mentioned doped manganese-based Prussian white cathode material was tested, and the obtained XRD pattern is shown in Figure 1. It can be seen that the doped manganese-based Prussian white cathode material has a monoclinic phase structure, and the XRD pattern analysis confirms that K and Li are doped in the Na position, and Li + and Na + Located at the 8c lattice interstitial point, K + Located at the 24d lattice interstitial point.

[0045] Example 2

[0046] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0047] Na 1.73 K 0.03 Li 0.02 Mn 0.69 Fe 0.31 [Fe(CN)6] 0.95 0.55H2O.

[0048] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0049] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.07 mol / L, the concentration of ferrous sulfate is 0.03 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0050] S2. KI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0051] Example 3

[0052] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0053] Na 1.71 K0.05 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.94 0.58H2O.

[0054] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0055] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0056] S2. KI (added in an amount of 35% of the total molar amount of manganese sulfate and ferrous sulfate) was added to the suspension described in S1, and a secondary aging reaction was carried out at 60° C. for 6 h to obtain a doped manganese-based Prussian white positive electrode material.

[0057] Example 4

[0058] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0059] Na 1.70 Li 0.06 Mn 0.60 Fe 0.40 [Fe(CN)6] 0.92 0.58H2O.

[0060] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0061] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0062] S2. LiI (added in an amount of 35% of the total molar amount of manganese sulfate and ferrous sulfate) was added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0063] Example 5

[0064] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0065] Na 1.75 K 0.06 Mn 0.61 Fe 0.30 Ni 0.09 [Fe(CN)6] 0.95 0.53H2O.

[0066] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0067] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, nickel sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.03 mol / L, the concentration of nickel sulfate is 0.01 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate, ferrous sulfate and nickel sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0068] S2. KI (added in an amount of 35% of the total molar amount of manganese sulfate and ferrous sulfate) was added to the suspension described in S1, and a secondary aging reaction was carried out at 60° C. for 6 h to obtain a doped manganese-based Prussian white positive electrode material.

[0069] Example 6

[0070] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0071] Na 1.72 Cu 0.04 Li 0.02 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.93 0.56H2O.

[0072] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0073] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0074] S2. CuI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0075] Example 7

[0076] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0077] Na 1.70 Cu 0.03 Mn 0.62 Fe 0.38 [Fe(CN)6] 0.92 0.57H2O.

[0078] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0079] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0080] S2. CuI (added in an amount of 20% of the total molar amount of manganese sulfate and ferrous sulfate) was added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6h to obtain a doped manganese-based Prussian white positive electrode material.

[0081] Example 8

[0082] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0083] Na 1.73 Cs 0.04 Li0.04 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.95 0.55H2O.

[0084] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0085] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0086] S2. CsI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0087] Comparative Example 1

[0088] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0089] Na 1.70 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.94 1.44H2O.

[0090] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0091] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0092] S2. The suspension described in S1 was subjected to a secondary aging reaction at 60° C. for 6 h to obtain a doped manganese-based Prussian white positive electrode material.

[0093] Comparative Example 2

[0094] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0095] Na 1.70 K 0.005 Li 0.01 Mn 0.60 Fe 0.40 [Fe(CN)6] 0.94 1.38H2O.

[0096] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0097] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0098] S2. KI (added in a molar amount of 8% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 5% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0099] Comparative Example 3

[0100] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0101] Na 1.71 K 0.03 Li 0.02 Mn[Fe(CN)6] 0.93 0.91H2O.

[0102] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0103] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.1 mol / L, and the molar amount of sodium citrate added is 4 times the molar number of manganese sulfate) were mixed uniformly, and a coprecipitation reaction was first performed at 60°C. After the reaction was completed, the suspension was aged at 60°C for 6 h to obtain a suspension;

[0104] S2. KI (added in a molar amount of 20% of the molar number of manganese sulfate) and LiI (added in a molar amount of 15% of the molar number of manganese sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60° C. for 6 h to obtain a doped manganese-based Prussian white positive electrode material.

[0105] Comparative Example 4

[0106] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0107] Na 1.70 Mn[Fe(CN)6] 0.92 ·1.61H2O.

[0108] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0109] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 1 mol / L, and the molar amount of sodium citrate added is 4 times the molar number of manganese sulfate) were mixed uniformly, and a coprecipitation reaction was first performed at 60°C. After the reaction was completed, the suspension was aged at 60°C for 6 h to obtain a suspension;

[0110] S2. The suspension described in S1 was subjected to a secondary aging reaction at 60° C. for 6 h to obtain a doped manganese-based Prussian white positive electrode material.

[0111] Comparative Example 5

[0112] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0113] Na 1.70 K 0.03 Li 0.03 Mn 0.89 Fe 0.11 [Fe(CN)6] 0.93 1.06H2O.

[0114] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0115] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.09 mol / L, the concentration of ferrous sulfate is 0.01 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0116] S2. KI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0117] Comparative Example 6

[0118] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0119] Na 1.71 Ca 0.03 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.93 ·1.281H2O.

[0120] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0121] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0122] S2. CaI2 (added in an amount of 35% of the total molar number of manganese sulfate and ferrous sulfate) was added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6h to obtain a doped manganese-based Prussian white positive electrode material.

[0123] Comparative Example 7

[0124] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0125] Na 1.71 Li 0.02 Mn0.63 Fe 0.37 [Fe(CN)6] 0.94 1.19H2O.

[0126] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0127] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0128] S2. KF (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiI (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0129] Comparative Example 8

[0130] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0131] Na 1.73 K 0.03 Mn 0.60 Fe 0.40 [Fe(CN)6] 0.94 0.83H2O.

[0132] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0133] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0134] S2. KI (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiF (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0135] Comparative Example 9

[0136] A doped manganese-based Prussian white cathode material, the chemical formula of which is as follows:

[0137] Na 1.70 Mn 0.61 Fe 0.39 [Fe(CN)6] 0.93 1.33H2O.

[0138] The above-mentioned doped manganese-based Prussian white positive electrode material can be prepared by the following preparation method:

[0139] S1. Solution I (a mixture of sodium ferrocyanide and deionized water, the concentration of sodium ferrocyanide is 0.1 mol / L) and solution II (a mixture of manganese sulfate, ferrous sulfate, sodium citrate and deionized water, the concentration of manganese sulfate is 0.06 mol / L, the concentration of ferrous sulfate is 0.04 mol / L, the molar amount of sodium citrate added is 4 times the total molar number of manganese sulfate and ferrous sulfate) were mixed uniformly, first coprecipitated at 60 ° C, and after the reaction was completed; the suspension was aged at 60 ° C for 6 h to obtain a suspension;

[0140] S2. KF (added in a molar amount of 20% of the total molar number of manganese sulfate and ferrous sulfate) and LiF (added in a molar amount of 15% of the total molar number of manganese sulfate and ferrous sulfate) were added to the suspension described in S1, and a secondary aging reaction was carried out at 60°C for 6 hours to obtain a doped manganese-based Prussian white positive electrode material.

[0141] Performance Testing

[0142] (1) Crystallization water content test: The doped manganese-based Prussian white positive electrode materials in Examples 1 to 8 and Comparative Examples 1 to 9 were subjected to thermogravimetric analysis under argon to obtain the weight of crystallization water. The crystallization water content (wt%) = (crystallization water weight / total sample weight) * 100%.

[0143] (2) Electrochemical Performance Test: The doped manganese-based Prussian white positive electrode materials in Examples 1 to 8 and Comparative Examples 1 to 9 were respectively made into positive electrode sheets, and metallic sodium was used as the negative electrode sheet, glass fiber was used as the separator, 1M NaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution was used as the electrolyte, and 4% by weight of the above electrolyte was added with fluorinated ethylene carbonate (FEC). Button cells were assembled and charge and discharge tests were performed at a current density of 15 mA / g (0.1C), a voltage range of 2.0 to 4.0 V, and 200 charge and discharge cycles under 1C conditions. The cycle stability of the doped manganese-based Prussian white positive electrode material was evaluated by the capacity retention rate after 200 charge and discharge cycles. The rate performance of the doped manganese-based Prussian white positive electrode material was evaluated by the discharge capacity retention rate under 10C conditions and 1C conditions. The test results are shown in Table 1 and Figure 2:

[0144] Capacity retention after 200 charge and discharge cycles at 1C (%) = (200th discharge capacity / 1st discharge capacity) * 100%;

[0145] 10C / 1C discharge capacity retention rate (%) = (discharge capacity at 10C / discharge capacity at 1C)*100%.

[0146] Table 1 Performance of doped manganese-based Prussian white positive electrode materials in various examples and comparative examples

[0147] It can be seen from the test results in Table 1 that the sodium ion batteries assembled with the positive electrode sheets prepared using the doped manganese-based Prussian white positive electrode materials in Examples 1 to 8 as the positive electrode materials have a capacity of 126 to 134 mAh / g at a voltage of 2.0 to 4.0 V and 0.1C; and the capacity retention rate after 200 charge and discharge cycles at 1C reaches 90% to 95%, and the 10C / 1C discharge capacity retention rate reaches 80% to 86%, indicating that the doped manganese-based Prussian white positive electrode material of the present invention has high capacity, excellent cycle stability and good rate performance.

[0148] From Comparative Example 1, it can be found that the Mn site is doped with divalent positive ions, but the Na site is not doped with monovalent positive ions (Li + and K + ), will lead to a sharp increase in the crystal water content in the manganese-based Prussian white positive electrode material, and is also not conducive to the improvement of cycle stability and rate performance; According to Comparative Example 2, even if divalent positive ions are doped at the Mn position and monovalent positive ions (Li + and K + ), but if the doping amount of monovalent positive ions is too low, it is difficult to effectively reduce the crystalline water content in the manganese-based Prussian white positive electrode material and improve the cycle stability and good rate performance.

[0149] Comparative Example 3 shows that while doping with monovalent positive ions at the Na position without divalent positive ions at the Mn position can reduce the crystal water content in the manganese-based Prussian White cathode material to a certain extent, it also causes a decrease in the capacity, cycle stability, and rate performance of the manganese-based Prussian White cathode material. Comparative Example 4 shows that when neither the Mn nor the Na position is doped, the crystal water content of the manganese-based Prussian White cathode material is as high as 9.1 wt%. At the same time, the discharge capacity at 0.1C is only 118 mAh / g, the capacity retention rate after 200 charge and discharge cycles at 1C is 65%, and the 10C / 1C discharge capacity retention rate is 70%. In other words, the capacity, cycle stability, and rate performance are all poor.

[0150] From Comparative Example 6, it can be seen that compared with doping monovalent positive ions at the Na position, doping divalent positive ions (Ca 2+ ) Although it can reduce the crystal water content to a certain extent, it is difficult to effectively improve the cycle stability and rate performance. According to Comparative Examples 7 to 9, when the fluoride of A or the mixture of iodide of A and fluoride is used for secondary aging reaction doping, due to F - Cannot participate in redox reaction, the corresponding Li + or K + Cannot enter Na + It is difficult to simultaneously improve the capacity, cycle stability and rate performance of the doped manganese-based Prussian white positive electrode material.

[0151] In summary, Li doping at the Na site improves rate performance but has little effect on capacity. Doping with other monovalent elements at the Na site improves cycle life. Doping with other monovalent elements at the Na site reduces the water content, while Li doping further reduces the water content and helps stabilize the crystal structure and fix residual water, thereby increasing the cycle life of the material. Doping at the Na and Mn sites can produce a synergistic effect, further reducing the water content and improving the lattice stability of the product, thereby improving rate performance and cycle life.

[0152] In addition, it can be seen from the charge and discharge curves of Figure 2 that the discharge specific capacity of the doped polyanion material in Example 1 reaches 130 mAh / g under the conditions of a voltage range of 2.0 to 4.0 V and a current density of 15 mA / g (0.1C), and the charge and discharge curve is smooth, indicating that it not only has a high capacity but also has excellent cycle stability.

[0153] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A doped manganese-based Prussian white positive electrode material, characterized in that: The chemical formula of the doped manganese-based Prussian white positive electrode material is Na n-d A d Mn 1-x M x [Fe(CN)6] y · zH2O; Among them, A is Li + , K + , Rb + , Cs + NH4 + , Cu + or Ag + One or more of; M is Ni 2+ , Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ One or more of the following; 1.7≤n≤2, 0.02≤d≤0.2, 0.2≤x≤0.4, 0.9≤y<1, 0<z<0.

8.

2. The doped manganese-based Prussian white positive electrode material according to claim 1, characterized in that: A is Li + , K + , Rb + , Cs + NH4 + , Cu + or Ag + At least two of which one is Li + .

3. The doped manganese-based Prussian white positive electrode material according to claim 1, characterized in that: The M is Ni 2+ , Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ At least two of which one is Fe 2+ .

4. The doped manganese-based Prussian white positive electrode material according to any one of claims 1 to 3, characterized in that: The doped manganese-based Prussian white positive electrode material has a monoclinic phase structure.

5. The doped manganese-based Prussian white positive electrode material according to claim 1, characterized in that: The crystal water content of the doped manganese-based Prussian white positive electrode material is ≤3.5wt%.

6. A method for preparing the doped manganese-based Prussian white positive electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. The solution I and the solution II are mixed uniformly, and then subjected to a coprecipitation reaction and an aging reaction to obtain a suspension; S2. The iodide of A is added to the suspension of S1 to perform a secondary aging reaction to obtain a doped manganese-based Prussian white cathode material; Wherein, the solution I in S1 is composed of sodium ferrocyanide and water, and the solution II is composed of soluble divalent manganese salt, soluble divalent M salt, sodium citrate and water; The M in the soluble divalent M salt is Ni 2+ , Fe 2+ 、Co 2+ 、Zn 2+ or Cu 2+ One or more of; A in S2 is Li + , K + , Rb + , Cs + NH4 + , Cu + or Ag + One or more of the .

7. The preparation method according to claim 6, characterized in that: The molar ratio of the sodium citrate to the soluble divalent manganese salt and the soluble divalent M salt mixture is (3-6):

1.

8. Use of the doped manganese-based Prussian white positive electrode material according to any one of claims 1 to 5 in a sodium ion battery.

9. A positive electrode sheet, comprising a current collector and a positive electrode active material layer disposed on at least one side of the current collector, characterized in that: The positive electrode active material layer comprises the doped manganese-based Prussian white positive electrode material according to any one of claims 1 to 5.

10. A sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte located between the positive electrode sheet and the negative electrode sheet, characterized in that: The positive electrode plate comprises the doped manganese-based Prussian white positive electrode material according to any one of claims 1 to 5.

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