CN107634217B - Preparation method of chromium-doped ternary material - Google Patents

Abstract

The invention relates to a preparation method of chromium-doped ternary material, which is characterized in that the compound of chromium is Cr₂O₃、Cr(OH)₃、Cr(NO₃)₃Or CrCl₃Or a mixture of chromate or dichromate with a reducing agent and a strong acid. Mixing nickel, cobalt, manganese and a compound doped with ions according to a molar ratio, and preparing a dried precursor through the steps of wet grinding, adding ammonia water, adding a lithium compound, aging, drying and the like. And (3) placing the dried precursor in an oxygen atmosphere, and preparing the chromium-doped ternary cathode material by adopting a programmed heating method or a zone-by-zone heating method. The invention has the advantages of low cost of raw materials, wide raw material sources, simple preparation process, simple and convenient operation and less time consumption. Compared with a coprecipitation method, the sewage discharged in the preparation process is obviously reduced, and LiMn does not exist in the prepared sample₆The superlattice structure and the prepared electrode material have good consistency, uniform composition and excellent discharge performance.

Description

Preparation method of chromium-doped ternary material

Technical Field

The invention belongs to the technical field of preparation of battery electrode materials, and relates to a preparation method of a nickel-cobalt-manganese ternary material which can be used as a chromium-doped ternary material of lithium batteries, lithium ion batteries, polymer batteries and supercapacitors.

Technical Field

With the increasing exhaustion of fossil energy, energy problems become a focus of attention. The search for new energy storage materials becomes one of the hot spots of research. The lithium ion battery of the new energy storage system has the advantages of high voltage, large capacity, no memory effect, long service life and the like, and can be widely applied to digital products such as mobile phones, digital cameras, notebook computers and the like and power tools such as electric vehicles, hybrid electric vehicles and the like.

The lithium ion battery comprises a positive electrode material, a negative electrode material, a diaphragm, electrolyte, a current collector and the like. Among them, the positive electrode material largely determines the performance of the battery. The positive electrode materials that have been successfully commercialized include lithium cobaltate, lithium manganate, lithium iron phosphate, and the like. However, the above materials have many disadvantages, and it is a hot research to find a positive electrode material with higher cost performance. In 1997, Ohzuku et al [ Ohzuku t.et al, chem.lett., 1997, 68: 642.]LiNi was first studied_1/3Mn_1/3Co_1/3O₂The properties of type III ternary materials. Research shows that the material fuses LiCoO₂、LiNiO₂And LiMn₂O₄Has the advantages of high reversible capacity, low cost, low toxicity and the like. The nickel cobalt manganese ternary material can be represented as: LiNi_xCo_yMn_zO₂(wherein x + y + z is 1). The ternary material can be divided into different types according to the different mole ratios of nickel, cobalt and manganese elements in the chemical formula. For example, a ternary material with a molar ratio of nickel, cobalt and manganese (x: y: z) of 3: 3, for short 333 type; the ternary material with the mole ratio of nickel, cobalt and manganese of 5: 2: 3 is named as 523 type; a ternary material having a molar ratio of nickel, cobalt and manganese of 8: 1 is called type 811, and similarly other types, etc. The 333 type, 523 type, 622 type and 811 type ternary materials all have alpha-NaFeO₂A layer-shaped structure. In the ternary material, the valence of nickel, cobalt and manganese elements is +2 valence, +3 valence and +4 valence respectively. Ni is the main active element. Theoretically, the higher the relative content of nickel, the higher the discharge capacity of the ternary material.

Koymaya et al [ Koymaya y., et al, j.power Sources, 2003, 119 (2): 644-648.]It is considered that Li_1-xNi_1/3Co_1/3Mn_1/3O₂Charging process with LiNi_1/3Co_1/3Mn_1/3O₂The examples are: with the elimination of Li ions, different electron pairs react. When 0 < x < 1/3, Ni occurs²⁺/Ni³⁺A transition of (a); when 1/3 < x < 2/3, Ni occurs³⁺/Ni⁴⁺A transition of (a); when 2/3 < x < 1, Co occurs³⁺/Co⁴⁺Is performed.

When 0 < x < 1/3

When 1/3 < x < 2/3

When 2/3 < x < 1:

for ternary materials, Ni at charging voltages below 4.3V (vs Li/Li +)²⁺As the main active material, Co^{3 +}Can improve the cyclability and rate capability of the material, while Mn⁴⁺Does not participate in the oxidation-reduction reaction in the circulation process.

Due to xLi₂MnO₃·(1-x)LiMO₂The structure and chemical composition of solid solution (M ═ Ni, Co, Mn) materials are very close to those of ternary materials, and many documents incorrectly express the structures of the two materials. For xLi₂MnO₃·(1-x)LiMO₂Solid solution (M ═ Ni, Co, Mn), charge voltage<4.4V, Li in solid solution₂MnO₃No electrochemical activity [ Yang f., Zhang q.et al, electrochim. acta, 2015, 165: 182-190.]. At this voltage, the LiMO in solid solution is mainly involved in the electrochemical reaction during charging₂。Li⁺From LiMO₂Is removed while M is oxidized to MO₂. During discharge in this case, with Li⁺Embedding, MO₂Can not be completely converted into LiMO₂Resulting in a partially irreversible reaction. When charging voltage>Li in solid solution at 4.4V₂MnO₃2 Li being extractable⁺And O^2-Incorporation (actually taking off Li)₂O), producing electrochemically active MnO₂Phase (1); during the discharge process, originallyPart of the Li taken off⁺Can be embedded back into MnO₂In (1). [ Chen c.j., et al, j.am. chem.soc., 2016, 138: 8824-8833.]. As can be seen from the above discussion, although both ternary and solid solution materials have layered alpha-NaFeO₂The structure and chemical composition are very similar. However, the charge-discharge curves and XRD diffraction patterns of the ternary material and the solid solution material are obviously different. From the relation curve of the discharge voltage and the discharge capacity of charge and discharge, when the charge voltage is higher than 4.4V, the charge specific capacity and the discharge specific capacity of the solid solution are obviously increased, and the discharge curve of the solid solution has the characteristic of oblique lines and has no obvious discharge voltage platform; in this case, the charging specific capacity and the discharging specific capacity of the ternary material are only slightly increased and are not obviously increased, and the discharging curve of the ternary material presents an S-shaped characteristic and has an obvious discharging voltage platform.

In recent years, spray drying and other preparation methods are also concerned, however, the coprecipitation method is still the main method for preparing the nickel, cobalt and manganese ternary material. Other methods are not industrially valuable. Briefly discussed below.

The coprecipitation method is to add a precipitator and a complexing agent into a mixed solution of various cations to control the nucleation and growth processes of precipitation, so as to obtain coprecipitation with controllable morphology and particle size. And filtering and drying the prepared coprecipitation to obtain a precursor. The precursor is mixed with lithium salt and then is sintered at high temperature to prepare the anode material. The synthesis method has good reproducibility, and the prepared product has uniform composition. The coprecipitation with controllable appearance and particle size can be prepared by controlling the stirring speed, pH value, aging temperature, precipitator, the dripping speed of the precipitator, the proportion of ammonia water and metal ions and the like in the precipitation process, and the problems of uneven material mixing, too wide particle size distribution and the like in the solid-phase synthesis method are solved. The coprecipitation method is classified into a hydroxide and carbonate coprecipitation method. Specifically, hydroxide and carbonate precipitating agents are respectively used for forming precursor precipitates of transition metal ions, then the precursor precipitates are mixed with lithium salt, and finally the ternary material is prepared by sintering. The hydroxide coprecipitation method is a common method for synthesizing ternary material precursors. The method generally uses NaOH as a precipitator and ammonia water as a complexing agent, and is controlled by the precipitatorThe pH value in the reaction process realizes the purpose of controlling the particle size and the morphology of the precursor by controlling the reaction temperature and the stirring speed, and finally controls the morphology and the electrochemical performance of the ternary material. During the preparation, due to the intermediate product Mn (OH) formed₂The precursor is unstable and is easily oxidized by air, and the performance of the material is affected, so nitrogen needs to be introduced for protection in the process of preparing the precursor. The hydroxide coprecipitation method has the advantages that a precursor with uniform particle size distribution is obtained by controlling reaction conditions; the disadvantage is the complex preparation process. In the preparation process, the concentration of raw materials, the dropping speed, the stirring speed, the pH value and the reaction temperature all influence the tap density and the particle size uniformity of the material. The biggest problems with this approach are: the precipitation conditions of hydroxide coprecipitation generated by nickel, cobalt and manganese are greatly different, and if the dosage of alkali in the precipitation process is insufficient, nickel and cobalt ions may be incompletely precipitated; if the amount of the alkali used in the precipitation process is excessive, the precipitated manganese ions may be dissolved, so that the room-temperature chemical composition and the performance of the prepared sample are difficult to be consistent.

Liang et al [ Liang L, et al, Electrochim Acta, 2014, 130: 82-89.]With NiSO₄·6H₂O、CoSO₄·7H₂O and MnSO₄·H₂Taking O as a raw material and 0.6mol/L ammonia water as a complexing agent, and preparing a uniformly mixed spherical precursor at a stirring speed of 800r/min and a pH value of 11.2. Washing, filtering, drying and calcining the precursor to obtain the product with the tap density of 2.59g/cm³622 type material. Under the current of 1C multiplying power and the voltage range of 2.8-4.3V, the discharge specific capacity of the prepared sample at the 1 st cycle is 172.1 mAh.g^-1The capacity retention rates at 100 cycles were 94.3%, respectively. Wen Lei et al [ Wen Lei, et al, Beijing university school newspaper, 2006, 42 (1): 12-17.]With LiOH. H₂O、NaHCO₃、CoSO₄·7H₂O、NiSO₄·6H₂O and MnSO₄·5H₂O is used as a raw material, carbonate precursor precipitate is prepared, and LiNi is prepared by washing, filtering, drying and secondary sintering_1/3Mn_1/3Co_1/3O₂And (3) sampling. Research shows that the voltage range of 2.5-4.4VThe first discharge capacity of the prepared sample was 162mAh · g^-1And has good cycle performance.

Mao yu qin, etc. (Mao yu qin, Chinese patent: CN 103972499A, 2014-08-06]Firstly, preparing soluble nickel salt, cobalt salt, aluminum salt and lithium salt into spherical LiNi by a coprecipitation method_1-a-bCo_aAl_bO₂Mixing the material with nano TiO₂Spraying the powder into a coating device to obtain LiNi_1-a-bCo_aAl_bO₂/TiO₂Capacity retention of greater than 99% at 50 cycles.

Previous researches show that the concentration of raw materials, the dropping speed of a precipitator, the stirring speed, the pH value and the reaction temperature are the key points for preparing the ternary material with high tap density and uniform particle size distribution. Zhou new east et al [ zhou new east et al, chinese patent: CN 102244239A, 2011-11]The spherical nickel-cobalt-aluminum ternary material is prepared by using a nickel, cobalt and aluminum salt solution and a lithium source through a secondary precipitation method, and the prepared sample has high tap density (3.02 g/cm)³) And the like. Further studies have shown that, in addition to the composition, particle size and particle size distribution of particles prepared by co-precipitation having an effect on the properties of the prepared samples, the radial distribution of the sample particle composition also has a significant effect on the properties of the samples. Hua et al [ Hua C, et al, j. alloys and Compounds, 2014, 614: 264-270.]With NiSO₄·6H₂O、CoSO₄·7H₂O、MnSO₄·5H₂Dissolving O as raw material in a circulating stirring kettle, adding ammonia water as complexing agent, and adding sodium hydroxide solution to adjust pH to 11.5. Stirring the mixture for 24 hours at the rotating speed of 750rpm and at the temperature of 55 ℃ to prepare a hydroxide precursor. And filtering, washing and drying the prepared precursor, and mixing and calcining the precursor and lithium hydroxide to prepare the 811 type ternary material with linear gradient. Studies show that the nickel content gradually decreases and the manganese content gradually increases from the core to the surface of the sample particles. Under the condition of large multiplying current, the discharge capacity and the cycle performance of the 811 type ternary material with the composition gradient distribution are obviously superior to those of the corresponding material with the uniform composition distribution. The discharge capacity of the 811 type ternary material forming the linear gradient distribution in the 1 st cycle is 185.2 mAh.g in a voltage interval of 2.8-4.3 and under a current of 1C multiplying power^-1The capacity retention at 100 cycles was 93.2%.

Hou et al, j.power Sources, 2014, 265: 174-181 ] sample preparation by fractional precipitation: pumping reactant solution with the molar ratio of nickel, cobalt and manganese of 8: 1 into a reaction kettle to form 811 nuclei, and pumping reactant solution with the molar ratio of nickel, cobalt and manganese of 3: 3 to form a first shell layer; then pumping reactant solution with the molar ratio of nickel, cobalt and manganese being 4: 2 to form a second shell layer; finally, the ternary material with a core of 811 type and a shell of 333 type and 422 type is prepared. The capacity retention for the 300 cycles of the prepared sample at 4C rate current was 90.9%.

Guokai et al [ guokai et al, chinese patent: CN 104979553A, 2015-10-14]Soluble nickel salt, cobalt salt, aluminum salt, lithium carbonate or lithium hydroxide are prepared into LiNi by a coprecipitation method_cCo_1-c-dAl_dO₂(c is more than 0.5, 0.5 is more than d is more than 0, 1 is more than c + d) coated LiNi_aCo_1-a-bAl_bO₂(a is more than 0.7, b is more than or equal to 0.05 and more than or equal to 0, and a + b is more than 1). Research shows that the coated micron LiNi_aCo_1-a-bAl_bO₂The cycle stability and the thermal stability of (a is more than 0.7, b is more than or equal to 0 and more than 1 and more than a + b) are obviously improved, and the flatulence rate is obviously reduced. Micron LiNi_0.8Co_0.15Al_0.05O₂Has a tap density of 2.51g/cm³. Under the voltage range of 3.0-4.3V and the current with 0.1C multiplying power, the first discharge capacity of the sample is 194.5mAh/g, and the first charge-discharge efficiency is 91.9%.

However, despite the above improvements, the ternary materials prepared at present have problems such as low electronic conductivity, poor high rate stability, poor high voltage cycling stability, cation shuffling, poor high and low temperature performance, and the like. In response to the above problems, the performance is currently improved mainly by doping, surface coating and post-treatment. However, the actual improvement effect is not significant at present.

Disclosure of Invention

The coprecipitation method is to add a precipitant into a solution of mixed metal salts to precipitate two or more cations in the solution together to produce a precipitate mixture or a pure solid solution precursor. The sample prepared by the coprecipitation method has the advantages of narrow particle size distribution, high tap density, excellent electrochemical performance and the like. However, the coprecipitation method requires energy-consuming and water-consuming preparation steps such as filtration and washing. A large amount of industrial wastewater is generated. In the preparation process of the coprecipitation method, the added precipitant is difficult to form uniform concentration in each part of the solution, so that precipitated particles are agglomerated or form nonuniform composition. In addition, the precipitation concentration products of nickel, cobalt and manganese salts have large difference, and the precipitation conditions of different ions have large difference. Manganese ions are easy to over-dissolve in a strong alkaline solution, the stoichiometric ratio of precursors is difficult to control, and the electrochemical properties of samples in different batches are affected. In order to improve the preparation process conditions and reduce the defects of the preparation method, the invention adopts a direct precipitation method to prepare the nickel-cobalt-manganese ternary material. In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

according to the molar ratio x of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions: y: z: k: and m, respectively weighing a nickel compound, a cobalt compound, a manganese compound, a lithium compound and a chromium compound. A nickel compound, a cobalt compound, a manganese compound and a chromium compound were mixed to obtain a mixture 1. Adding a wet grinding medium with the volume 1-20 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the pH value of the solution falls within the range of 9.5-12.5, adding a weighed lithium compound, and aging at any temperature within the temperature range of 65-90 ℃ for 24-48 hours under an inert atmosphere without oxygen to prepare a mixture serving as a precursor 2. Heating the precursor 2 at any temperature in the range of 160-260 ℃ under the vacuum condition of less than 1 atmosphere to prepare a dried precursor 3, or preparing the dried precursor 3 at any temperature in the range of 160-260 ℃ by adopting a spray drying method. And (3) placing the dried precursor 3 in an oxygen atmosphere, and preparing the chromium-doped ternary cathode material by adopting a programmed heating method or a temperature-region-by-temperature-region heating method.

Two or more compounds of the weighed nickel compound, cobalt compound, manganese compound, lithium compound and chromium compound are soluble in water.

The molar ratio x of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions is as follows: y: z: k: m satisfies the following relationship: x: y: z: m is (0.49-0.51): (0.12-0.19): (0.20-0.30): (0.01-0.08), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m is equal to k;

or y: z: m is (0.59-0.61): (0.12-0.19): (0.19-0.21): (0.01-0.08), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m is equal to k;

or y: z: m ═ 0.79 to 0.81: (0.03-0.09): (0.05-0.10): (0.01-0.07), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m is equal to k.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern are equal to the layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; under the conditions of 0.2C multiplying current and 1 st charge-discharge cycle, the proportion of increasing the charging specific capacity by 4.6V to 4.4V is less than 25 percent relative to the constant current charging of a lithium electrode; the 2 theta angle of a sample XRD diffraction pattern in the range of 20-25 degrees does not correspond to Li₂MnO₃Diffraction peaks of (JCPDS cards 27-1252).

The programmed heating method is carried out as follows: and (3) placing the dried precursor 3 in an oxygen atmosphere, heating to any temperature in the temperature range of 800-880 ℃ from the room temperature program at the speed of 0.1-8 ℃/min, and cooling to the room temperature to obtain the chromium-doped ternary cathode material.

The temperature rising method by temperature zones is carried out as follows: and (3) placing the dried precursor 3 in an oxygen atmosphere, heating from a room temperature region to any temperature in a temperature range of 800-880 ℃ at a heating speed of 0.1-8 ℃/temperature region, and cooling to room temperature to obtain the chromium-doped ternary cathode material.

The nickel compound is nickel oxide, nickel hydroxide, nickel nitrate, nickel chloride, nickel acetate, basic nickel carbonate or nickel carbonate.

The cobalt compound is cobalt hydroxide, cobalt oxide, cobalt nitrate, cobalt chloride, cobalt acetate or cobalt carbonate.

The manganese compound is manganese hydroxide, manganese oxide, manganese nitrate, manganese chloride or manganese acetate.

The lithium compound is lithium fluoride, lithium citrate, lithium nitrate, lithium chloride, lithium carbonate, lithium acetate or lithium hydroxide.

The chromium compound is Cr₂O₃、Cr(OH)₃、Cr(NO₃)₃Or CrCl₃Or a mixture of chromate or dichromate with a reducing agent and a strong acid.

The chromate or dichromate is sodium or potassium chromate or dichromate. The reducing agent is hydrazine hydrate, formic acid, formaldehyde or hydrogen peroxide.

The strong acid is sulfuric acid or nitric acid. The strong acid is used in an amount such that the acidity of the reaction product of the chromate or dichromate with the mixture of the reducing agent and the strong acid is between pH1 and pH 5.

The reducing agent is used in an amount to completely reduce hexavalent chromium ions in the chromate or dichromate to trivalent chromium ions.

The temperature-region-by-temperature-region heating method is used for sintering in a roller kiln, a tunnel kiln or a mesh belt furnace.

The tunnel kiln is a push plate type tunnel kiln.

The temperature in different zones of roller kiln, tunnel kiln or mesh belt furnace is different, which is equivalent to different temperature zones, i.e. the temperature in each temperature zone is different, and generally the temperature is gradually increased from room temperature zone to the temperature needing sintering, and then the temperature is decreased from the temperature needing sintering to room temperature.

The wet grinding medium is deionized water, distilled water, ethanol, acetone, methanol or formaldehyde.

The spray drying method is drying at any temperature in a temperature range of 160-260 ℃.

The inert atmosphere is nitrogen, argon or helium.

The invention has the advantages of low cost of raw materials, wide raw material sources, simple preparation process, simple and convenient operation and less time consumption. Compared with a coprecipitation method, the sewage discharged in the preparation process is obviously reduced, and LiMn does not exist in the prepared sample₆The ratio of the super-lattice structure to the increase of the charging specific capacity of 4.6V to 4.4V by constant current charging of a lithium electrode is less than 25%, and the prepared electrode material is consistentThe material has the advantages of good performance, uniform composition, excellent discharge performance, particularly good discharge cycle performance under the condition of large current, and lays a good foundation for industrialization.

Compared with the invention patents (ZL201210391584.0, 201210391629.4, 201210391413.8, 201210391672.0, 201210391441.x) related to solid solution preparation, which were applied in the earlier stage of this project group, the invention patents are patents with completely different compositions. From a structural point of view, the samples prepared herein do not have LiMn₆Superlattice structure, and the structure of the solid solution sample has LiMn₆A superlattice structure; from the chemical composition of the sample, the compositions of the 523, 622, 811 type ternary materials are close to Li [ Ni ]_0.5Co_0.2Mn_0.3]O₂、Li[Ni_0.6Co_0.2Mn_0.2]O₂、Li[Ni_0.8Co_0.1Mn_0.1]O₂(ii) a And solid solution xLi₂MnO₃(1-x)Li[Ni_yMn_zCo_k]O₂Has the chemical formula of Li_(1+x)[Ni_(1-x)yCo_(1-x)kMn_(x+z-xz)]O_(2+x). If the formula xLi in patent ZL201210391584.0 is considered₂MnO₃(1-x)Li[Ni_yMn_zCo_k]O₂The value range of (a) can be calculated to obtain the theoretical composition of a solid solution sample: li: ni: co: mn: the O molar ratio is (1-1.39): (0.0173-0.333): (0.0174-0.443): (0.204-0.952): (1.87-2.26). The theoretical composition of the solid solution patent applied in the previous period of this project group is similar to that of patent ZL201210391584.0, therefore, the chemical formulas of the solid solution patent applied in the previous period and the solid solution applied in the previous period have certain similarities, but the two are completely different inventions.

Drawings

Figure 1 is an XRD diffractogram of a sample prepared in example 1 of the present invention.

Fig. 2 is a graph of the discharge at cycle 1 at 1C rate current for the sample prepared in example 1 of the present invention at a voltage interval of 2.5 to 4.3V.

FIG. 3 is a graph of discharge capacity versus cycle performance for samples prepared in example 1 of the present invention at a voltage interval of 2.5 to 4.3V and a current rate of 1C.

Detailed Description

The present invention will be further described with reference to the following examples. The examples are merely further additions and illustrations of the present invention, and are not intended to limit the invention.

Example 1

According to the molar ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.5: 0.19: 0.3: 1: 0.01 separately weighing nickel acetate, cobalt acetate, manganese acetate, lithium hydroxide and Cr₂O₃. Nickel acetate, cobalt acetate, manganese acetate and Cr₂O₃Mixing to obtain a mixture 1. Adding deionized water with volume 5 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity of the solution is pH12.5, adding weighed lithium hydroxide, and aging for 24 hours at 85 ℃ in a nitrogen atmosphere to obtain a precursor 2. The precursor 2 was heated at 230 ℃ under a vacuum of 0.1 atm to obtain a dried precursor 3. The precursor 3 is put in an oxygen atmosphere, heated from room temperature to 850 ℃ at the speed of 5 ℃/min, and cooled to room temperature to prepare the layered alpha-NaFeO₂The zirconium-doped ternary cathode material with the structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; under the conditions of 0.2C multiplying current and 1 st cycle charge and discharge, the proportion of increasing the charging specific capacity to 4.6V to 4.4V by the constant current charge of the lithium electrode is 15 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 2

According to the molar ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.49: 0.12: 0.30: 0.97: 0.06 weight of nickel oxide, cobalt nitrate, manganese oxide, lithium citrate and Cr (OH)₃. Nickel oxide, cobalt nitrate, manganese oxide and Cr (OH)₃Mixing to obtain a mixture 1. Adding distilled water in an amount of 1 time of the total volume of the mixture 1, and continuously stirringUnder the condition of (1), ammonia water is dripped until the acidity pH of the solution is 12.0, weighed lithium citrate is added, and the mixture is aged for 48 hours at 65 ℃ in an argon atmosphere to prepare a precursor 2. Precursor 2 was spray dried at 260 c to prepare dried precursor 3. The precursor 3 is put into an oxygen atmosphere, is heated to 880 ℃ from room temperature by a program at the speed of 8 ℃/min, is cooled to room temperature, and the layered alpha-NaFeO is prepared₂The chromium-doped ternary cathode material has a structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half-cell prepared from the prepared ternary material is charged to 4.6V to 4.4V at a constant current relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and discharge, and the ratio of the increase of the charging specific capacity is 17 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 3

According to the molar ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.51: 0.19: 0.30: 1.08: 0.08 separately weigh Nickel nitrate, cobalt acetate, manganese oxide, lithium nitrate and Cr (OH)₃. Nickel nitrate, cobalt acetate, manganese oxide and Cr (OH)₃Mixing to obtain a mixture 1. Adding methanol with the volume 20 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity of the solution is pH9.5, adding weighed lithium nitrate, and aging for 38 hours at 90 ℃ in a helium atmosphere to obtain a precursor 2. The precursor 2 was heated at 260 ℃ under a vacuum of 0.9 atm to obtain a dried precursor 3. The precursor 3 is put in an oxygen atmosphere, heated from room temperature to 800 ℃ at the speed of 0.1 ℃/min, and cooled to room temperature to prepare the layered alpha-NaFeO₂The chromium-doped ternary cathode material has a structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half cell prepared from the prepared ternary material is constant relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and dischargeThe ratio of the increase of the charging specific capacity of the current charging to 4.6V to 4.4V is 18 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 4

According to the molar ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.61: 0.19: 0.20: 1.08: 0.08 separately weighing Nickel chloride, cobalt carbonate, manganese nitrate, lithium fluoride and Cr (NO)₃)₃. Nickel chloride, cobalt carbonate, manganese nitrate and Cr (NO)₃)₃Mixing to obtain a mixture 1. Adding formaldehyde with the volume 1 time of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity of the solution is pH 10, adding weighed lithium nitrate, and aging for 40 hours at 80 ℃ in an argon atmosphere to obtain a precursor 2. The precursor 2 is heated at 160 ℃ under the vacuum condition of 0.01 atmospheric pressure to prepare a dried precursor 3. The precursor 3 is put into an oxygen atmosphere, is heated to 800 ℃ from room temperature by a program at the speed of 8 ℃/min, and is cooled to room temperature to prepare the lamellar alpha-NaFeO₂The chromium-doped ternary cathode material has a structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half-cell prepared from the prepared ternary material is charged to 4.6V to 4.4V at a constant current relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and discharge, and the ratio of the increase of the specific charge capacity is 21 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 5

According to the mole ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.79: 0.03: 0.06: 0.95: 0.07 weight nickel hydroxide, cobalt hydroxide, manganese hydroxide, lithium carbonate and potassium dichromate respectively. Excess formic acid was weighed as 0.63mol per the amount needed to completely reduce the hexavalent chromium to trivalent chromium in the potassium dichromate. Mixing potassium dichromate, formic acid and nitric acid, and reacting in such amount thatThe acidity of the solution after the completion of the reaction was pH 2. Mixing with nickel hydroxide, cobalt hydroxide and manganese hydroxide to obtain a mixture 1. Adding ethanol with the volume 20 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity of the solution is pH 10.5, adding weighed lithium carbonate, and aging for 26 hours at 80 ℃ in a nitrogen atmosphere to obtain a precursor 2. The precursor 2 was heated at 160 ℃ under a vacuum of 0.1 atm to obtain a dried precursor 3. The precursor 3 is put into an oxygen atmosphere, is heated to 800 ℃ from room temperature by a program at the speed of 0.2 ℃/min, and is cooled to room temperature to prepare the layered alpha-NaFeO₂The chromium-doped ternary cathode material has a structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half-cell prepared from the prepared ternary material is charged to 4.6V to 4.4V at a constant current relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and discharge, and the ratio of the increase of the specific charge capacity is 20 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 6

According to the mole ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.81: 0.09: 0.10: 1.01: 0.01 nickel carbonate, cobalt oxide, manganese acetate, lithium acetate and sodium chromate are weighed respectively. And simultaneously weighing 0.99mol of excessive oxalic acid according to the amount required by completely reducing hexavalent chromium in the sodium chromate into trivalent chromium, mixing the weighed sodium chromate, the weighed oxalic acid and nitric acid for reaction, wherein the amount of the nitric acid used ensures that the acidity of the solution after the reaction is finished is pH 1. Nickel carbonate, cobalt oxide and manganese acetate were mixed to obtain mixture 1. Adding deionized water which is 1 time of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity of the solution is pH 11.0, adding weighed lithium acetate, and aging for 48 hours at 90 ℃ in an argon atmosphere to obtain a precursor 2. Precursor 2 was spray dried at 260 c to prepare dried precursor 3. Placing the precursor 3 in an oxygen atmosphere, gradually heating from room temperature to 880 ℃ at a heating rate of 0.1 ℃/temperature zone, and cooling to room temperatureWarming to prepare the alpha-NaFeO with the layer shape₂The chromium-doped ternary cathode material has a structure.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half-cell prepared from the prepared ternary material is charged to 4.6V to 4.4V at a constant current relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and discharge, and the ratio of the increase of the charging specific capacity is 17 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Example 7

According to the molar ratio of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions of 0.80: 0.06: 0.05: 0.97: 0.06 weight nickel acetate, cobalt chloride, manganese acetate, lithium nitrate and chromium chloride respectively. Nickel acetate, cobalt chloride, manganese acetate and chromium chloride were mixed to give a mixture 1. Adding ethanol with the volume 5 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the acidity pH of the solution is 12.5, adding weighed lithium nitrate, and aging for 24 hours at 85 ℃ in an argon atmosphere to obtain a precursor 2. Precursor 2 was spray dried at 200 ℃ to prepare dried precursor 3. The precursor 3 is placed in an oxygen atmosphere, heated from a room temperature zone to 800 ℃ at a heating speed of 0.1 ℃/temperature zone, and cooled to room temperature to prepare the layered alpha-NaFeO₂The structure of the chromium-doped ternary cathode material.

The ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern and layered alpha-NaFeO₂The characteristic diffraction peaks of the structure (JCPDS card 09-0063) are matched; the button half-cell prepared from the prepared ternary material is charged to 4.6V to 4.4V at a constant current relative to a lithium electrode under the conditions of 0.2C rate current and 1 st cycle charge and discharge, and the ratio of the increase of the specific charge capacity is 16 percent; no weak diffraction peak appears in the range of 20-25 degrees of 2 theta angle of XRD diffraction pattern of the sample, and no weak diffraction peak corresponds to Li₂MnO₃Diffraction peaks (JCPDS cards 27-1252) were generated by diffraction.

Claims (9)

1. The preparation method of the chromium-doped ternary material is characterized by comprising the following steps: according to the molar ratio x of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions: y: z: k: m respectively weighing a nickel compound, a cobalt compound, a manganese compound, a lithium compound and a chromium compound; mixing a nickel compound, a cobalt compound, a manganese compound and a chromium compound to obtain a mixture 1; adding a wet grinding medium with the volume 1-20 times of the total volume of the mixture 1, dropwise adding ammonia water under the condition of continuous stirring until the pH value of the solution falls within the range of 9.5-12.5, adding a weighed lithium compound, and aging at any temperature within the temperature range of 65-90 ℃ for 24-48 hours under the inert atmosphere of nitrogen, argon or helium without oxygen to prepare a mixture as a precursor 2; heating the precursor 2 at any temperature in a range of 160-260 ℃ under a vacuum condition with the pressure lower than 1 atmospheric pressure to prepare a dried precursor 3 or preparing the dried precursor 3 at any temperature in a range of 160-260 ℃ by adopting a spray drying method; placing the dried precursor 3 in an oxygen atmosphere, and preparing the chromium-doped ternary cathode material by adopting a programmed heating method or a temperature-region-by-temperature-region heating method;

more than two compounds of the nickel compound, the cobalt compound, the manganese compound, the lithium compound and the chromium compound are weighed to be soluble in water;

the molar ratio x of nickel ions, cobalt ions, manganese ions, lithium ions and chromium ions is as follows: y: z: k: m satisfies the following relationship:

x: y: z: m = (0.49 to 0.51): (0.12-0.19): (0.20-0.30): (0.01-0.08), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m = k;

or x: y: z: m = (0.59 to 0.61): (0.12-0.19): (0.19-0.21): (0.01-0.08), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m = k;

or x: y: z: m = (0.79-0.81): (0.03-0.09): (0.05-0.10): (0.01-0.07), k is more than or equal to 0.95 and less than or equal to 1.08, and x + y + z + m = k;

the ternary material simultaneously satisfies the following characteristics: diffraction peaks on an XRD diffraction pattern are all equal to the layered alpha-NaFeO of JCPDS card 09-0063₂The characteristic diffraction peaks of the structure are matched; the button half cell prepared from the material is opposite under the conditions of 0.2C multiplying current and 1 st charge-discharge cycleThe ratio of the increase of the specific charge capacity of the lithium electrode when the lithium electrode is charged to 4.6V to 4.4V at constant current is less than 25 percent; li which does not correspond to JCPDS card 27-1252 in the range of 20-25 degrees of 2 theta angle of sample XRD diffraction pattern₂MnO₃A diffraction peak of (a);

the temperature rising method by temperature zones is carried out as follows: placing the dried precursor 3 in an oxygen atmosphere, heating from a room temperature zone to any temperature in a temperature range of 800-880 ℃ at a heating speed of 0.1-8 ℃/temperature zone, and cooling to room temperature to obtain the chromium-doped ternary cathode material; the programmed heating method is carried out as follows: and (3) placing the dried precursor 3 in an oxygen atmosphere, heating to any temperature in the temperature range of 800-880 ℃ from the room temperature program at the speed of 0.1-8 ℃/min, and cooling to the room temperature to obtain the chromium-doped ternary cathode material.

2. The method according to claim 1, wherein the nickel compound is nickel oxide, nickel hydroxide, nickel nitrate, nickel chloride, nickel acetate, basic nickel carbonate or nickel carbonate.

3. The method of claim 1, wherein the cobalt compound is selected from the group consisting of cobalt hydroxide, cobalt oxide, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt carbonate.

4. The method of claim 1, wherein said manganese compound is selected from the group consisting of manganese hydroxide, manganese oxide, manganese nitrate, manganese chloride, and manganese acetate.

5. The method of claim 1, wherein said lithium compound is selected from the group consisting of lithium fluoride, lithium citrate, lithium nitrate, lithium chloride, lithium carbonate, lithium acetate, and lithium hydroxide.

6. The method of claim 1, wherein the chromium compound is Cr₂O₃、Cr(OH)₃、Cr(NO₃)₃Or CrCl₃Or a mixture of chromate or dichromate with a reducing agent and a strong acid.

7. The method of claim 6, wherein the chromate or dichromate is sodium chromate or dichromate, or potassium chromate or dichromate; the reducing agent is hydrazine hydrate, formic acid, formaldehyde or hydrogen peroxide, and the dosage of the reducing agent can completely reduce hexavalent chromium ions in chromate or dichromate into trivalent chromium ions; the strong acid is sulfuric acid or nitric acid, and the using amount of the strong acid is such that the acidity of a reaction product of chromate or dichromate, a reducing agent and a mixture of the strong acid is between pH1 and pH 5.

8. The method of claim 1, wherein the wet milling medium is deionized water, distilled water, ethanol, acetone, methanol, or formaldehyde.

9. The method for preparing the chromium-doped ternary material according to claim 1, wherein the temperature-region-by-temperature-region heating method is used for sintering in a roller kiln, a tunnel kiln or a mesh belt furnace, and the tunnel kiln is a push plate type tunnel kiln.

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