Preparation method and application of high-manganese Prussian white material

Abstract

The invention discloses a high-manganese Prussian white material as well as a preparation method and application thereof. Mn in the high-manganese Prussian white material has + 2 valence and + 1 valence at the same time; the chemical formula of the Na-2x-yAx [By (CN) 6]. ZH2O is as follows: Na6-2x-yAx [By (CN) 6]. A is Mn < 2 + >, and x is the atom number of A in the chemical formula; b is Mn < + >, and y is the atom number of B in the chemical formula; z is the atomic number of H2O in the chemical formula; 0.5 < = x + y < = 3, 0 < x < = 1. The + 2 valence Mn in the Prussian white material is partially replaced by + 1 valence Mn, the manganese content is increased compared with that of conventional Prussian white, the number of active sodium sites of the Prussian white material is increased, and then the specific capacity and energy density of the electrode material are improved; the moderate increase of the manganese content is beneficial to improving the crystallization integrity and keeping the stability of the material structure and the electrochemical performance; the problems that in the prior art, a high-manganese Prussian white material is low in specific capacity and energy density and poor in stability are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a high-manganese Prussian white material, a preparation method thereof, and an application thereof. Background Art

[0002] The crystal structure of Prussian compounds is a unique three-dimensional open framework structure formed by transition metals and Fe elements respectively connecting with N and C in CN-. The crystal structure is face-centered cubic, with transition metal ions forming six-coordination with CN-, and alkali metal ions being in the three-dimensional channel structure and coordination pores. Due to the unique electronic structure of cyanide double coordination, as well as the unique open framework and three-dimensional macroporous structure, it is suitable for the migration and storage of sodium ions, and has the advantages of stable structure, fast insertion / extraction rate, and large specific capacity. The actual energy density of the all-solid-state battery composed of Prussian compounds and hard carbon can reach 130 Wh / kg - 160 Wh / kg, and the theoretical energy density is 500 Wh / kg - 600 Wh / kg, but there is still a certain gap compared with the energy density of lithium ion batteries. Summary of the Invention

[0003] In view of the above analysis, aiming at the deficiencies in the prior art, the present invention aims to provide a preparation method and an application of a high-manganese Prussian white material, and solve at least one of the problems such as low specific capacity, low energy density, and poor stability existing in the high-manganese Prussian white material in the prior art.

[0004] The object of the present invention is mainly achieved through the following technical solutions: A high-manganese Prussian white material, wherein Mn in the high-manganese Prussian white material has both +2 and +1 valences.

[0005] Preferably, the chemical formula of the high-manganese Prussian white material satisfies: Na 6-2x-y A x [B y (CN)6]·zH2O; A is Mn 2 + , x is the atomic number of A in the chemical formula; B is Mn + , y is the atomic number of B in the chemical formula; z is the atomic number of H2O in the chemical formula; 0.5 ≤ x + y ≤ 3, 0 < x ≤ 1.

[0006] Preferably, x and y satisfy: 1 ≤ x + y ≤ 2, 0.5 ≤ x ≤ 1.

[0007] Preferably, the manganese content ratio in the high-manganese Prussian white material is 31 wt% - 34 wt%; preferably, the manganese content ratio is 33 wt% - 34 wt%.

[0008] Preferably, the chemical formula of the high-manganese Prussian white material satisfies: Na3A[B(CN)6]·zH2O; A is Mn 2+ , B is Mn + ; z is the number of H2O atoms in the chemical formula.

[0009] Preferably, z satisfies: 0.2 ≤ z ≤ 0.4.

[0010] A method for preparing a high-manganese Prussian white material for preparing the above-mentioned high-manganese Prussian white material, comprising: using NaH as a reducing agent to reduce Mn 2+ in the raw material to Mn + , and preparing high-manganese Prussian white.

[0011] Preferably, it includes: Using NaH as a reducing agent to reduce Mn 2+ in the first divalent manganese salt to Mn + , and preparing an insoluble manganese-sodium composite salt; Co-precipitating the manganese-sodium composite salt and the second divalent manganese salt to prepare high-manganese Prussian white with a lower solubility than the manganese-sodium composite salt.

[0012] Preferably, the method for preparing the high-manganese Prussian white material further includes: Controlling the reaction temperature and reaction time during the co-precipitation of the manganese-sodium composite salt and the second divalent manganese salt, so that the crystal water in the high-manganese Prussian white material meets the target range.

[0013] An application of a high-manganese Prussian white material, characterized in that it is used to prepare a battery electrode and a rechargeable battery, using the high-manganese Prussian white material described in the above claims or the high-manganese Prussian white material prepared by the above preparation method.

[0014] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) In the Prussian white material of the present invention, part of the +2-valent Mn is replaced by +1-valent Mn, which increases the manganese content compared with the conventional Prussian white, increases the number of active sodium sites in the Prussian white material, and thus increases the specific capacity and energy density of the electrode material; a moderate increase in the manganese content helps to improve the crystallinity integrity and maintain the stability of the material structure and electrochemical performance; it solves the problems of low specific capacity, low energy density, and poor stability existing in the high-manganese Prussian white material in the prior art. The specific capacity of the high-manganese Prussian white is 186.2 mAh / g to 196.4 mAh / g. Preferably, the specific capacity is 192.4 mAh / g to 196.4 mAh / g; the capacity retention rate of the battery after 100 cycles is 90.4% to 94.6%. Preferably, the capacity retention rate of the battery after 100 cycles is 93.8% to 94.6%.

[0015] (2) The present invention uses NaH as a strong reducing agent, which can reduce Mn in the raw materials 2+ to Mn + without introducing new impurities; enabling part of the +2-valent Mn in the Prussian white material to be replaced by +1-valent Mn, improving the long-life cycle ability, the stability of the sodium-ion battery, the specific capacity and energy density of the electrode material.

[0016] (3) By dropping an aqueous solution of divalent manganese salt into a molten NaH / NaOH solution, the present invention realizes the full contact and reduction of NaH with the divalent manganese salt in an anhydrous environment, while avoiding the introduction of impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings are only for the purpose of showing specific embodiments and are not considered as limiting the present invention. Throughout the drawings, the same reference signs denote the same components; Figure 1 It is the cycle performance diagram of the Prussian white material in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clear, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Technical terms: Specific capacity: It refers to the amount of electric charge that can be provided by a unit mass or unit volume of battery material, usually expressed in mAh / g (mass specific capacity) or mAh / cm³ (volume specific capacity).

[0020] Energy density: It refers to the energy stored in a unit mass or unit volume of battery, usually expressed in Wh / kg (mass energy density) or Wh / L (volume energy density).

[0021] Energy density is the common result of specific capacity and voltage: Energy density not only depends on specific capacity, but also is related to the discharge platform voltage of the battery; under the same voltage, the larger the specific capacity, the larger the energy density.

[0022] On the one hand, the present invention discloses a high-manganese Prussian white material, including: In the high-manganese Prussian white material, Mn has both +2-valent and +1-valent at the same time.

[0023] The applicant's research found that reducing part of the +2-valent Mn to +1-valent in the Prussian white material and introducing a high proportion of sodium helps to improve the first Coulomb efficiency, improve the long-life cycle ability, and further improve the stability and first Coulomb efficiency of the sodium-ion battery.

[0024] Compared with the prior art, in the Prussian white material of the present invention, +2-valent Mn is partially replaced by +1-valent Mn, which increases the manganese content compared with conventional Prussian white, increases the number of active sodium sites in the Prussian white material, and thus increases the specific capacity and energy density of the electrode material; a moderate increase in the manganese content helps to improve the crystallinity integrity and maintain the stability of the material structure and electrochemical performance. The specific capacity of the high-manganese Prussian white is 186.2 mAh / g to 196.4 mAh / g. Preferably, the specific capacity is 192.4 mAh / g to 196.4 mAh / g; the capacity retention rate after 100 cycles of the battery is 90.4% to 94.6%. Preferably, the capacity retention rate after 100 cycles of the battery is 93.8% to 94.6%.

[0025] Preferably, the chemical formula of the high-manganese Prussian white material satisfies: Na 6-2x-y A x [B y (CN)6]·zH2O; A is Mn 2 + , x is the number of atoms of A in the chemical formula; B is Mn + , y is the number of atoms of B in the chemical formula; z is the number of atoms of H2O in the chemical formula; 0.5 ≤ x + y ≤ 3, 0 < x ≤ 1.

[0026] More preferably, 1 ≤ x + y ≤ 2, 0.5 ≤ x ≤ 1.

[0027] It should be noted that the Prussian white material has a cubic structure. Although Mn + can replace Na + to form a cubic structure, the diameter of Mn + is larger than that of Na + . Excessive Mn + can increase the specific capacity and energy density of the electrode material, but it is not conducive to maintaining the crystallinity integrity of the cubic structure and the stability of the material structure and electrochemical performance.

[0028] Preferably, the proportion of manganese content in the high-manganese Prussian white material is 31 wt% to 34 wt%; it can be 31.0 wt%, 31.2 wt%, 31.3 wt%, 31.4 wt%, 31.6 wt%, 31.8 wt%, 32.0 wt%, 32.2 wt%, 32.04 wt%, 32.5 wt%, 32.6 wt%, 32.7 wt%, 32.8 wt%, 33.0 wt%, 33.2 wt%, 33.4 wt%, 33.5 wt%, 33.6 wt%, 33.8 wt% or 34.0 wt%.

[0029] It should be noted that when the manganese content is greater than 34 wt%, it will cause Prussian white to be more likely to trigger the Taylor effect during charge and discharge, resulting in corrosion and dissolution of material particles, generation of intergranular cracks, continuous increase in interfacial impedance, and serious degradation of the bulk structure, thus affecting the cycle stability of the material; at the same time, the electrode material cannot play a good role in sodium compensation during the cycle, resulting in a decrease in conductivity, poor rate performance, and decline in cycle performance; when the manganese content is <31 wt%, the proportion of the +2 valence state of Mn decreases at this time. During the first charging process, only a small part of Mn 2+ will be reduced to Mn + , resulting in a lower first discharge specific capacity; when the manganese content accounts for 31 wt% - 34 wt%, it is beneficial to obtain better cycle performance and first discharge specific capacity.

[0030] Preferably, the manganese content accounts for 33 wt% - 34 wt%.

[0031] Preferably, the chemical formula of the high-manganese Prussian white material satisfies: Na3A[B(CN)6]·zH2O; A is Mn + , B is Mn 2+ ; z is the number of H2O atoms in the chemical formula, and 0.2 ≤ z ≤ 0.4.

[0032] It should be noted that when z < 0.2, it is difficult for the Prussian white material to maintain a cubic structure; when z > 0.4, there is too much crystal water in the Prussian white material, which penetrates into the electrolyte during charge and discharge and reacts with the electrolyte, affecting the stable use of the battery; 0.2 ≤ z ≤ 0.4 is beneficial to obtaining better cycle performance.

[0033] Preferably, the average particle size of the Prussian white material is 20 μm - 60 μm, such as 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm, 60 μm.

[0034] It should be noted that the particle size of the electrode material has the following effects on the electrode performance: when the particle size is too large, the ion transport distance in the material is large, and the rate performance is poor; when the particle size is too small, the conductivity of the material is affected, and the electrode performance deteriorates; when the particle size is too small, it is difficult to disperse the material.

[0035] On the other hand, the present invention discloses a method for preparing a high-manganese Prussian white material, including: using NaH as a reducing agent to reduce Mn in the raw material 2+ to Mn + to prepare high-manganese Prussian white.

[0036] It should be noted that the valence state of Mn 2+ determines that its quantity cannot be increased without limit when complexing with cyanate in Prussian white; while Mn + can replace Na + in the cubic structure Prussian white to obtain high-manganese Prussian white, which increases the manganese content compared with conventional Prussian white, thereby increasing the specific capacity and energy density of the electrode material; a moderate increase in the manganese content helps to improve the crystallinity integrity and maintain the stability of the material structure and electrochemical performance.

[0037] Compared with the prior art, the present invention uses NaH as a strong reducing agent, which can reduce Mn 2+ in the raw materials to Mn + without introducing new impurities; enables part of the +2-valent Mn in the Prussian white material to be replaced by +1-valent Mn, improving the long-life cycle ability and the stability of sodium-ion batteries, the specific capacity and energy density of the electrode material. The specific capacity of high-manganese Prussian white is 186.2 mAh / g to 196.4 mAh / g. Preferably, the specific capacity is 192.4 mAh / g to 196.4 mAh / g; the capacity retention rate of the battery after 100 cycles is 90.4% to 94.6%. Preferably, the capacity retention rate of the battery after 100 cycles is 93.8% to 94.6%.

[0038] Specifically, the preparation method of the high-manganese Prussian white material includes: Using NaH as a reducing agent to reduce Mn 2+ in the first divalent manganese salt to Mn + to prepare an insoluble manganese-sodium composite salt; Co-precipitating the manganese-sodium composite salt with the second divalent manganese salt to prepare high-manganese Prussian white with lower solubility than the manganese-sodium composite salt.

[0039] It should be noted that as an electrode material, the water of crystallization content in Prussian white has a significant impact on both electrical properties and stability: if the water of crystallization is too little, for example, when z < 0.2, it is difficult for the Prussian white material to maintain the cubic structure; if the water of crystallization is too much, for example, when z > 0.4, it will penetrate into the electrolyte during charge and discharge and react with the electrolyte, affecting the stable use of the battery; 0.2 ≤ z ≤ 0.4 is beneficial to obtaining better cycle performance.

[0040] In order to control the water of crystallization in the high-manganese Prussian white material within the range of 0.2 ≤ z ≤ 0.4, the preparation method of the high-manganese Prussian white material further includes: Controlling the reaction temperature and reaction time during the co-precipitation of the manganese-sodium composite salt and the second divalent manganese salt so that the water of crystallization in the high-manganese Prussian white material meets the target range.

[0041] Specifically, the manganese-sodium composite salt can be sodium manganocyanide.

[0042] Specifically, the co-precipitation reaction temperature is 50°C to 60°C, and can be 50°C, 52°C, 53°C, 54°C, 55°C, 56°C, 58°C or 60°C.

[0043] Preferably, the co-precipitation reaction temperature is 55°C to 60°C.

[0044] It should be noted that at lower temperatures, the solubility of the raw materials is poor and the ion transfer rate is poor; at higher temperatures, although it is beneficial to reduce the formation of crystal water, it affects the stability of Mn + resulting in Mn in the high-manganese Prussian white material + being lower than expected.

[0045] Specifically, the co-precipitation reaction time is 10 h to 20 h, and can be 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h.

[0046] It should be noted that the co-precipitation reaction is a process for preparing high-manganese Prussian white with lower solubility from the manganese-sodium composite salt. In the manganese-sodium composite salt, Na + is replaced by Mn 2+ A longer co-precipitation reaction time is beneficial for Na + to be fully replaced by Mn 2+

[0047] Specifically, the method for preparing the high-manganese Prussian white material includes: Step 1) Dissolve the reducing agent NaH in molten NaOH to prepare the precursor liquid A; Step 2) Disperse the first divalent manganese salt and sodium cyanide in an acidic solution to obtain the precursor liquid B; Step 3) Add the precursor liquid B to the precursor liquid A to obtain sodium manganocyanide precipitate; Step 4) Disperse sodium manganocyanide in deionized water to obtain the precursor liquid C; Step 5) Dissolve the second divalent manganese salt and the complexing agent in deionized water to obtain the precursor liquid D; Step 6) Slowly add the precursor liquid C to the precursor liquid D to co-precipitate the high-manganese Prussian white.

[0048] Specifically, Step 1) is carried out in an inert gas environment, and the reaction temperature is 320°C to 350°C, which can ensure the full melting of NaOH.

[0049] Specifically, in Step 1), the mass ratio of NaH to NaOH is 1:3 to 12, and can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11 or 1:12.

[0050] It should be noted that if the proportion of NaH is too high, it cannot be completely dissolved in the molten NaOH liquid, and if the proportion of NaH is too low, after adding divalent manganese salt later, Mn cannot be fully reduced, 2+ resulting in the appearance of impurity phases in the product.

[0051] Specifically, the pH of the acidic solution in step 2) is 3 - 6, which can inhibit the hydrolysis of sodium cyanide and is conducive to keeping the cyanate ions in sodium cyanide free to participate in the coordination reaction.

[0052] Specifically, the acidic solution in step 2) can be one or more of citric acid solution, acetic acid solution, hydrocyanic acid solution and dilute sulfuric acid solution.

[0053] Specifically, the molar ratio of the divalent manganese salt to NaCN in step 2) is 1:6.1 - 6.5, ensuring that NaCN is slightly in excess.

[0054] Specifically, the volume ratio of precursor liquid A to precursor liquid B in step 3) is (1 - 1.5):2, which can be 1:2, 1.1:2, 1.2:2, 1.3:2, 1.4:2 or 1.5:2.

[0055] It should be noted that in step 3), precursor liquid B needs to be dropped into precursor liquid A at a high temperature to ensure that the water in precursor liquid B volatilizes at a high temperature and does not react with NaH in precursor liquid A; at the same time, the molten NaOH can serve as a good reaction solvent, enabling the divalent manganese salt and sodium hydride in precursor liquid B to come into full contact and react.

[0056] Compared with the prior art, the present invention realizes the full contact and reduction of NaH to divalent manganese salt in an anhydrous environment by dropping an aqueous solution of divalent manganese salt into a molten NaH / NaOH solution, while avoiding the introduction of impurities.

[0057] Preferably, the precursor liquid C in step 4) includes 3 wt% - 10 wt% of ascorbic acid as an antioxidant and 10 wt% - 50 wt% of sodium manganocyanide.

[0058] Specifically, the divalent manganese salt in step 2) and the divalent manganese salt in step 5) are one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; the divalent manganese salt in step 2) and the divalent manganese salt in step 5) can be the same or different.

[0059] Specifically, the complexing agent in step 5) is one or more of sodium nitrilotriacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, and diethylenetriaminepentaacetate.

[0060] Specifically, the mass ratio of the complexing agent in the precursor liquid D is 0.5% to 2%, which can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0061] Specifically, the mass ratio of the divalent manganese salt in the precursor liquid D is 10 wt% to 50 wt%.

[0062] Specifically, the prepared Prussian white material with high manganese content is dried at a temperature not higher than 180 °C.

[0063] It should be noted that the water in the Prussian white material with high manganese content includes interstitial water and coordinated water. The interstitial water is the free water physically adsorbed in the atomic gaps of the Prussian white with high manganese content and does not participate in the formation of the Prussian blue crystal structure; the coordinated water is the water molecule that participates in the formation of the Prussian blue crystal structure through chemical bonds. The crystal water in the Prussian white material with high manganese content refers to the coordinated water; the drying treatment at a temperature not higher than 180 °C will cause the Prussian white material with high manganese content to lose the interstitial water, and the coordinated water in the Prussian blue crystal structure will not be affected.

[0064] Regarding step 6), it should also be noted that the present invention can adjust the total amount of Mn in the precursor liquid C added to the reaction system + and Mn in the precursor liquid D 2+ to adjust the ratio of Mn + and Mn 2+ in the product.

[0065] As an example, when preparing Na3A[B(CN)6]·0.2H2O, the total amount of Mn in the precursor liquid C + and Mn in the precursor liquid D 2+ is controlled to be 1:1.

[0066] In a third aspect, the present invention discloses an application of a Prussian white material with high manganese content, which is used to prepare battery electrodes and rechargeable batteries, using the above-mentioned Prussian white material with high manganese content or the Prussian white material prepared by the above preparation method.

[0067] Specifically, Na3A[B(CN)6]·0.2H2O, where A is Mn 2+ , B is Mn + , conductive carbon black, and binder (PVDF) are added to a certain volume of NMP solvent in a ratio of 8:1:1, stirred and mixed evenly, and the slurry is coated on the surface of an aluminum foil (thickness 20 μm) to prepare a positive electrode plate, and the coating thickness is 50 μm; Five 1-cm 2The circular electrode is used as the positive electrode, the sodium sheet is used as the negative electrode, the separator is made of PP material, and the electrolyte is NaPF6. The button battery is assembled in a glove box; The button battery was left to stand for 48 hours and then subjected to electrochemical performance testing: the specific capacity of the high manganese Prussian white was 186.2 mAh / g ~ 196.4 mAh / g, preferably, the specific capacity was 192.4 mAh / g ~ 196.4 mAh / g; the capacity retention rate of the battery after 100 cycles was 90.4% ~ 94.6%, preferably, the capacity retention rate of the battery after 100 cycles was 93.8% ~ 94.6%.

[0068] In order to better illustrate the technical solution of the present invention, the following examples and comparative examples are further provided:

[0069] Example 1 This embodiment discloses a high-manganese Prussian white material: Na3A[B(CN)6]·0.2H2O; A is Mn 2+ , B is Mn + .

[0070] The preparation method comprises: Under argon protection, 15 g of NaOH was weighed and heated to 325°C to melt, and then 3 g of NaH was weighed and dissolved in the molten NaOH liquid to obtain precursor liquid A; Weigh 0.2 g of acetic acid and dissolve it in 20 mL of deionized water to prepare a weak acid solution with a pH of 4.2. Then, weigh 1.42 g of MnCl2 and 6.05 g of NaCN and dissolve them in the weak acid solution. Stir in a closed container for 50 minutes to obtain precursor solution B. Precursor liquid B was slowly added to precursor liquid A, stirred and mixed, and then allowed to stand for 15 hours. After separation and precipitation, it was washed with deionized water and dried under vacuum at 90°C for 35 hours to prepare sodium manganous cyanide (Na5Mn(CN)6). Weigh 4 g of Na5Mn(CN)6 and 0.15 g of ascorbic acid and dissolve them in 15 mL of deionized water. Stir well to obtain precursor solution C. Weigh 1.86 g of MnSO4 and 0.02 g of disodium ethylenediaminetetraacetate and dissolve them in 10 mL of deionized water to obtain precursor solution D; Precursor liquid C was slowly added to precursor liquid D to carry out a co-precipitation reaction. The reaction temperature was set at 40°C. After standing for 20 hours, it was washed and vacuum-dried at 90°C for 30 hours to obtain cubic high-manganese Prussian white, namely Na3A[B(CN)6]·0.2H2O.

[0071] The crystalline water content in the high manganese Prussian white product is calculated as follows: After weighing the high manganese Prussian white product for the first time, drying it at 190°C for 8 hours, and then weighing it again. Drying continues, and the high manganese Prussian white is weighed again every hour. If the weight change between the two weighings is less than 0.1%, it is determined that all crystal water has been removed from the high manganese Prussian white. The crystal water content of the high manganese Prussian white product is calculated based on the weight of the high manganese Prussian white weighed last and the weight of the first weighing. The calculated crystal water content z in the high manganese Prussian white product of the present invention is 0.2012, which is substantially the same as the theoretical value. The structural formula of the high manganese Prussian white product satisfies Na3A[B(CN)6]·0.2H2O, and the manganese content accounts for 33.28%.

[0072] Na3A[B(CN)6]·0.2H2O, where A is Mn 2+ , B is Mn + , conductive carbon black, and binder (PVDF) were added to a certain volume of NMP solvent in a ratio of 8:1:1, stirred and mixed evenly, and the slurry was coated on the surface of aluminum foil (thickness 20μm) to prepare the positive electrode sheet with a coating thickness of 50μm; Cut the electrode sheet into 5 pieces of 1 cm 2 The circular electrode is used as the positive electrode, the sodium sheet is used as the negative electrode, the separator is made of PP material, and the electrolyte is NaPF6. The button battery is assembled in a glove box; The button battery was left standing for 48 hours before undergoing electrochemical performance testing. The test current density was 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity was 192.4 mAh / g. This material has a high specific capacity. After 100 cycles, the capacity retention rate was 93.8%.

[0073] Example 2 This embodiment discloses a high-manganese Prussian white material: Na3A[B(CN)6]·0.35H2O; A is Mn 2+ , B is Mn + .

[0074] The preparation method comprises: Under argon protection, 21 g of NaOH was weighed and heated to 325°C to melt, and then 4 g of NaH was weighed and dissolved in the molten NaOH liquid to obtain precursor liquid A; Weigh 0.25 g of citric acid and dissolve it in 20 mL of deionized water to prepare a weak acid solution with a pH of 4.2. Then, weigh 2.2 g of MnSO4 and 4.45 g of NaCN and dissolve them in the weak acid solution. Stir in a closed container for 35 minutes to obtain precursor solution B. Precursor liquid B was slowly added to precursor liquid A, stirred and mixed, and then allowed to stand for 12 hours. After separation and precipitation, it was washed with deionized water and dried under vacuum at 110°C for 40 hours to prepare sodium manganous cyanide (Na5Mn(CN)6). Weigh 4 g of Na5Mn(CN)6) and 0.15 g of ascorbic acid, dissolve them in 15 mL of deionized water, and stir evenly to obtain the precursor solution C; Weigh 2.2 g of MnSO4 and 0.03 g of nitrilotriacetic acid trisodium salt, dissolve them in 14 mL of deionized water to obtain the precursor solution D; Slowly add the precursor solution C to the precursor solution D for coprecipitation reaction. Set the reaction temperature at 75 °C. After standing for 15 h, wash and dry in vacuum at 90 °C for 24 h to obtain cubic high-manganese Prussian white, namely Na3A[B(CN)6]·0.35H2O; Detect z = 0.4998 in the high-manganese Prussian white product by the same method as in Example 1. The high-manganese Prussian white product conforms to Na3A[B(CN)6]·0.35H2O, and the manganese content accounts for 33.03%.

[0075] Add Na3A[B(CN)6]·0.35H2O, conductive carbon black, and binder (PVDF) in a ratio of 8:1:1 to a certain volume of NMP solvent, stir and mix evenly, and coat the slurry on the surface of aluminum foil (thickness 20 μm) to prepare a positive electrode plate, with a coating thickness of 50 μm; Cut 5 circular electrode plates of 1 cm 2 from the above electrode plate as the positive electrode, a sodium sheet as the negative electrode, a separator made of PP material, and an electrolyte of NaPF6, and assemble them into a button battery in a glove box; After the button battery stands for 48 h, perform electrochemical performance tests. The test current density is 50 mA / g, based on the mass of the positive electrode active material, the specific capacity is 189.7 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 94.6%.

[0076] Example 3 This example discloses a high-manganese Prussian white material: Na 2.5 A 1.5 [B 0.5 (CN)6]·0.2H2O.

[0077] The difference in the preparation method from Example 1 is as follows: Replace the divalent manganese salt with an equal molar amount of MnCl2; select disodium ethylenediaminetetraacetate as the complexing agent; Adjust the ratio of the precursor solution C to the precursor solution D so that the molar ratio of Mn + in the precursor solution C to MnCl2 in the precursor solution D is 3:1.

[0078] Detect z = 0.1988 in the prepared high-manganese Prussian white by the same method as in Example 1. The high-manganese Prussian white product meets Na 2.5 A 1.5 [B 0.5(CN)6]·0.2H2O, with a manganese content ratio of 33.32%.

[0079] Add Na 2.5 A 1.5 [B 0.5 (CN)6]·0.2H2O, where A is Mn + , B is Mn 2+ , conductive carbon black, and binder (PVDF) in a ratio of 8:1:1 to a certain volume of NMP solvent, stir and mix evenly, and coat the slurry on the surface of aluminum foil (thickness 20μm) to prepare the positive electrode plate, with a coating thickness of 50μm; Cut 5 circular electrode plates of 1 cm 2 from the above electrode plate as the positive electrode, sodium sheet as the negative electrode, the separator is made of PP, and the electrolyte is NaPF6, and assemble into a button battery in a glove box; After the button battery is left standing for 48h, perform electrochemical performance tests. The test current density is 50mA / g, based on the mass of the positive electrode active material, the specific capacity is 196.4mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 90.4%.

[0080] Example 4 This example discloses a high-manganese Prussian white material: Na 3.5 A 0.5 [B 1.5 (CN)6]·0.2H2O.

[0081] The difference in the preparation method from Example 1 is that: Adjust the ratio of precursor solution C to precursor solution D so that the molar ratio of Mn + in precursor solution C to MnCl2 in precursor solution D is 1:3.

[0082] Detect z = 0.1988 for the prepared high-manganese Prussian white according to the same method as in Example 1. The high-manganese Prussian white product satisfies Na 3.5 A 0.5 [B 1.5 (CN)6]·0.2H2O, with a manganese content ratio of 35.59%.

[0083] Add Na 3.5 A 0.5 [B 1.5 (CN)6]·0.2H2O, where A is Mn + , B is Mn 2+ , conductive carbon black, and binder (PVDF) in a ratio of 8:1:1 to a certain volume of NMP solvent, stir and mix evenly, and coat the slurry on the surface of aluminum foil (thickness 20μm) to prepare the positive electrode plate, with a coating thickness of 50μm; Cut 5 circular electrode plates with a size of 1 cm from the above-mentioned electrode plate 2 as the positive electrode, sodium sheet as the negative electrode, the separator is made of PP material, and the electrolyte is NaPF6. Assemble a button battery in a glove box; After the button battery stands for 48 h, perform an electrochemical performance test. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity is 186.2 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 93.2%.

[0084] Comparative Example 1 This comparative example discloses a preparation method of a high-manganese Prussian white material. Compared with Example 1, in this comparative example, the mass ratio of NaH to NaOH is 30:75, the dosage of NaOH is 15 g, which is the same as that in Example 1, and the dosage of NaH exceeds the protection scope of the present invention.

[0085] The methods for preparing the electrode and the battery are the same as those in Example 1. After the button battery stands for 48 h, perform an electrochemical performance test. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity is 158.1 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 85.7%.

[0086] Comparative Example 2 This comparative example discloses a high-manganese Prussian white material: Na2A2[B(CN)6]·0.2H2O.

[0087] The difference in the preparation method from Example 1 is as follows: Adjust the ratio of precursor solution C to precursor solution D so that the molar ratio of Mn in precursor solution C + to MnCl2 in precursor solution D is 1:3: Take 1 g of Na5Mn(CN)6) and 0.15 g of ascorbic acid and dissolve them in 15 mL of deionized water, and stir evenly to obtain precursor solution C; Weigh 1.395 g of MnSO4 and 0.015 g of disodium ethylenediaminetetraacetate and dissolve them in 10 mL of deionized water to obtain precursor solution D.

[0088] Detect z = 0.1988 for the prepared high-manganese Prussian white according to the same method as in Example 1. The high-manganese Prussian white product meets Na2A2[B(CN)6]·0.2H2O, and the manganese content accounts for 44.68%.

[0089] The methods for preparing the electrode and the battery are the same as those in Example 1. After the button battery stands for 48 h, perform an electrochemical performance test. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity is 234.6 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 78.2%.

[0090] Comparative Example 3 This comparative example discloses a preparation method of a high-manganese Prussian white material. Compared with Example 1, the pH of the weak acid solution in this comparative example is 6.52; the pH of the weak acid solution is higher than the protection range of the present invention, which affects the formation of sodium ferrocyanide.

[0091] The methods for preparing the electrode and the battery are the same as those in Example 1. After the button battery is left standing for 48 h, the electrochemical performance is tested. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the manganese in the product is insufficient, and the specific capacity is reduced to 152.9 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 86.7%.

[0092] Comparative Example 4 This comparative example discloses a preparation method of a high-manganese Prussian white material. Compared with Example 1, the co-precipitation reaction temperature in this comparative example is 80 °C, which is higher than the protection range of the present invention.

[0093] The prepared high-manganese Prussian white is detected in the same method as in Example 1, and z = 0.88 is obtained. The product does not conform to Na3A[B(CN)6]·0.2H2O.

[0094] The methods for preparing the electrode and the battery from the high-manganese Prussian white are the same as those in Example 1. After the button battery is left standing for 48 h, the electrochemical performance is tested. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity is 184.5 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 84.9%.

[0095] Comparative Example 5 This comparative example discloses a preparation method of a high-manganese Prussian white material. Compared with Example 1, the co-precipitation reaction time in this comparative example is 5 h, which is lower than the protection range of the present invention.

[0096] The prepared high-manganese Prussian white is detected in the same method as in Example 1, and z = 0.5 is obtained. The product does not conform to Na3A[B(CN)6]·0.2H2O.

[0097] The methods for preparing the electrode and the battery are the same as those in Example 1. After the button battery is left standing for 48 h, the electrochemical performance is tested. The test current density is 50 mA / g. Based on the mass of the positive electrode active material, the specific capacity is 182.1 mAh / g. This material has a relatively high specific capacity. After 100 cycles, the capacity retention rate is 86.3%.

[0098] As can be seen from the above, the specific capacity of the high-manganese Prussian white prepared in Examples 1-4 of the present invention is 186.2 mAh / g to 196.4 mAh / g. Preferably, the specific capacity is 192.4 mAh / g to 196.4 mAh / g; the capacity retention rate of the battery after 100 cycles is 90.4% to 94.6%. Preferably, the capacity retention rate of the battery after 100 cycles is 93.8% to 94.6%.

[0099] The amount of NaH used, the proportion of manganese content in the product, the pH of the weak acid solution, the co-precipitation reaction temperature, and the co-precipitation reaction time outside the protection range will all have an adverse effect on the specific capacity and the battery cycle stability.

[0100] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A high-manganese Prussian white material, characterized in that, In the high-manganese Prussian white material, Mn has both +2 and +1 valence states simultaneously.

2. The Prussian white material with high manganese according to claim 1, characterized in that, The chemical formula of the high-manganese Prussian white material satisfies: Na 6-2x-y A x [B y (CN)6]·zH2O; A is Mn 2+ , x is the number of atoms of A in the chemical formula; B is Mn + , y is the number of atoms of B in the chemical formula; z is the number of atoms of H2O in the chemical formula; 0.5 ≤ x + y ≤ 3, 0 < x ≤ 1.

3. The Prussian white material of manganese according to claim 2, wherein x and y satisfy: 1 ≤ x + y ≤ 2, 0.5 ≤ x ≤ 1.

4. The Prussian white material with high manganese according to claim 3, characterized in that, The manganese content in the high-manganese Prussian white material accounts for 31 wt% to 34 wt%.

5. The Prussian white material according to claim 4, characterized in that, The chemical formula of the high-manganese Prussian white material satisfies: Na3A[B(CN)6]·zH2O; A is Mn 2+ , B is Mn + ; z is the number of atoms of H2O in the chemical formula.

6. The Prussian white high manganese material according to claim 5, characterized in that, z satisfies: 0.2 ≤ z ≤ 0.

4.

7. A method for preparing a high-manganese Prussian white material, characterized in that, For preparing the high-manganese Prussian white material according to any one of claims 1-6, comprising: using NaH as a reducing agent to reduce Mn in the raw materials 2+ to Mn + , and preparing the high-manganese Prussian white.

8. The method for preparing the high-manganese Prussian white material according to claim 7, wherein, It includes: Using NaH as a reducing agent to reduce Mn in the first divalent manganese salt 2+ to Mn + , and preparing an insoluble manganese-sodium composite salt; Co-precipitating a manganese-sodium composite salt and a second divalent manganese salt to prepare high-manganese Prussian white with a lower solubility than the manganese-sodium composite salt.

9. The preparation method of the high-manganese Prussian white material according to claim 8, wherein The preparation method of the high-manganese Prussian white material further includes: Controlling the reaction temperature and reaction time during the co-precipitation of the manganese-sodium composite salt and the second divalent manganese salt so that the crystal water in the high-manganese Prussian white material meets the target range.

10. Application of a high-manganese Prussian white material, characterized in that, For preparing battery electrodes and rechargeable batteries, using the high-manganese Prussian white material described in any one of claims 1-6 or the high-manganese Prussian white material prepared by the preparation method described in any one of claims 7-9.

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