A modified lithium nickel oxide cathode material, a preparation method and application thereof

Abstract

The application discloses a modified lithium nickelate positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion battery materials. The preparation method of the modified lithium nickelate positive electrode material comprises the following steps: raw materials containing at least alginate, betaine substances, a lithium source and a nickel source are heated and cross-linked to form a hydrogel in the presence of an initiator and a cross-linking agent, the hydrogel is dried and crushed, and then the modified lithium nickelate positive electrode material is obtained through solid-phase sintering. The unique precursor preparation method is adopted, the alginate and the betaine substances are selected as the substances for forming the hydrogel, the two substances are complementary to each other, the hydrogel with good performance can be formed, and the carbon coating on the surface of the lithium nickelate positive electrode material can be more uniform in the subsequent sintering process, and the stability of the lithium nickelate positive electrode material in the charging and discharging cycle process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, in particular to a modified lithium nickelate positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] At present, with the increasing demand of the market for high-capacity, high-power and long-life batteries, lithium nickelate (LiNiO2) has become a research hotspot for lithium ion battery positive electrode materials. It has high theoretical specific capacity, low self-discharge rate, low price and no pollution. However, it also has some defects, such as the difficulty of converting Ni 2+ to Ni 3+ , which further leads to lithium-nickel mixing, and poor cycle stability caused by lattice distortion and structure collapse during charging and discharging. The commonly used modification method is element doping. For example, Yang Jianwen et al. improved the structural stability and electrochemical performance of lithium nickelate positive electrode material by means of iron and titanium atomic chemical doping modification (CN113845150A); Wang Hao et al. improved the specific capacity and cycle stability of the material by preparing aluminum and zirconium doped spherical precursor nickel hydroxide (CN113809321A); Meng Yabin et al. improved the specific capacity and cycle stability of lithium nickelate material by using copper doped precursor (CN108511749A).

[0003] The above methods have limited performance improvement of lithium nickelate material, and a new modified lithium nickelate positive electrode material and its preparation method and application need to be developed. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a modified lithium nickelate positive electrode material and a preparation method and application thereof.

[0005] The technical problem of the present application is solved by the following technical scheme.

[0006] The present application provides a preparation method of a modified lithium nickelate positive electrode material, which comprises: heating and cross-linking the aqueous solution of raw materials containing at least alginate, betaine, lithium source and nickel source in the presence of an initiator and a cross-linking agent to form a hydrogel, then drying and crushing the hydrogel, and finally obtaining the modified lithium nickelate positive electrode material by solid phase sintering.

[0007] The present application also provides a modified lithium nickelate positive electrode material prepared by the above preparation method, wherein the composition of the lithium nickelate positive electrode material is LiNi 1-x M x O2, M includes at least one of Mn, Co, Mg, Zr, Ti, Nb and Sr, and x is 0.05-0.3.

[0008] The application further provides a lithium battery, wherein a positive electrode of the lithium battery comprises the modified lithium nickelate positive electrode material.

[0009] The application has the following beneficial effects:

[0010] The application provides a modified lithium nickelate positive electrode material, a preparation method and application thereof, and the preparation method comprises the following steps: at least raw materials containing alginate, betaine, a lithium source and a nickel source are heated and cross-linked to form a hydrogel in the presence of an initiator and a cross-linking agent. In the above preparation method, alginate and betaine are selected as the substances for forming the hydrogel, and the advantages of alginate and betaine are complementary, so that the hydrogel with good performance can be formed, and meanwhile, the formation of the hydrogel can uniformly disperse various raw materials, so that the uniformity and consistency of the carbon coating layer formed by the alginate on the surface of the lithium nickelate positive electrode material can be ensured when high-temperature sintering is performed, and the cycle stability of the material in the charging and discharging process can be improved, so that the modified lithium nickelate positive electrode material prepared has high charging and discharging capacity and excellent electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0012] Figure 1 XRD patterns of the samples prepared in Examples 1-4;

[0013] Figure 2 SEM patterns of the samples prepared in Examples 1-4. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the technical solutions in the embodiments of the application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are used. If the reagents or instruments used are not specified by the manufacturers, they are all conventional products that can be purchased on the market.

[0015] In order to overcome the defect of poor cycle stability of lithium nickelate, the lithium nickelate positive electrode material is modified by one or both of element doping and surface coating according to the application. The uniformity and consistency of carbon coating and element doping of the lithium nickelate material are realized from the source. The modified lithium nickelate positive electrode material with high cycle stability and high capacity can be obtained by the method provided in the embodiments of the application.

[0016] The application further provides a modified lithium nickelate positive electrode material, a preparation method and application thereof.

[0017] In a first aspect, the application also provides a preparation method of the modified lithium nickelate positive electrode material, which comprises: mixing raw materials containing at least alginate, betaine, a lithium source and a nickel source, and then mixing the raw materials with an initiator and a crosslinking agent in water, and then heating and crosslinking the water solution of the raw materials to form a hydrogel, and then drying and crushing the hydrogel, and then performing solid-phase sintering to obtain the modified lithium nickelate positive electrode material.

[0018] The application provides a preparation method of a modified lithium nickelate positive electrode material, which comprises: mixing raw materials containing at least alginate, betaine, a lithium source and a nickel source with an initiator and a crosslinking agent in water, and then heating and crosslinking the mixture to form a hydrogel, and then drying and crushing the hydrogel, and then performing high-temperature sintering to obtain the modified lithium nickelate positive electrode material. The alginate is a natural polysaccharide, which is widely available and economical, environmentally friendly and biodegradable. The alginate water solution can form a hydrogel by adding divalent cations, and the gelation condition is relatively mild. However, the alginate macromolecular material has poor stability, and the mechanical property of the hydrogel is low, and the mechanical strength is greatly reduced with the increase of water content. The betaine and its derivatives are neutral substances, and the effective component is trimethyl glycine. The betaine has strong hygroscopicity, and has active methyl and double-charge properties. The betaine also has excellent degradability and stability. In the application, the alginate and the betaine are used to prepare a high-performance hydrogel, which can overcome the defects of the two substances when used alone, and can combine the advantages of the two substances, so as to obtain a hydrogel material with controllable structure and excellent functional properties. The above hydrogel with good properties can make the raw materials uniformly distributed in the whole system. Then, the hydrogel is dried and crushed, and then solid-phase sintering is performed, so that the alginate is converted into a carbon layer uniformly coated on the surface of the generated lithium nickelate positive electrode material particles, and a high-stability carbon-coated lithium nickelate positive electrode material is obtained. As can be seen from the above, the alginate not only acts as a carbon source and a binder in the high-temperature carbonization process during the synthesis of the modified lithium nickelate positive electrode material, but more importantly, the alginate can form a three-dimensional carbon network structure to coat the surface of the lithium nickelate particles, so as to improve the electrochemical performance of the lithium nickelate positive electrode material.

[0019] In the embodiment of the present application, at least the raw materials containing alginate, betaine, lithium source and nickel source are mixed with initiators and cross-linking agents in water, and then cross-linked to form hydrogel after heating, so that each raw material in the hydrogel system is uniformly distributed in the whole system. After high-temperature sintering of the hydrogel, the alginate is converted into carbon particles to form a uniform and stable carbon coating layer on the surface of the lithium nickelate positive electrode material. The in-situ carbon-coated method generates a uniform and dense carbon coating layer on the surface of the lithium nickelate positive electrode material, which can ensure the uniformity and consistency of the carbon coating on the surface of the lithium nickelate positive electrode material, and is beneficial to improving the cycle stability of the material during charging and discharging.

[0020] In an optional embodiment, the preparation method of the modified lithium nickelate positive electrode material comprises the following steps:

[0021] The alginate is dissolved in water to obtain an alginate aqueous solution;

[0022] The remaining raw materials are added to the alginate aqueous solution and mixed, and then initiators and cross-linking agents are added. After sufficient stirring, the hydrogel is formed after heating;

[0023] After freeze-drying and crushing of the hydrogel, the modified lithium nickelate positive electrode material is obtained by solid-phase sintering.

[0024] The preparation method of the modified lithium nickelate positive electrode material provided in the embodiment of the present application is as follows: the alginate is first dissolved in water to prepare an alginate aqueous solution. Since the alginate is not easy to dissolve, it needs to be dissolved separately. After the alginate aqueous solution is prepared, it is convenient to mix with other raw materials such as betaine, lithium source and nickel source to form a mixed and uniform raw material aqueous solution. Then, the raw material aqueous solution is mixed with initiators and cross-linking agents, and the hydrogel is formed after heating after sufficient stirring. The hydrogel is freeze-dried to remove the solvent therein, and then crushed as a calcination object for high-temperature calcination. In this process, the lithium source and the nickel source become suspended particulate matter in the sol solution and are wrapped by the sol. After heating to remove part of the solvent, the sol undergoes gelation, changes into a gel and wraps the surface of the lithium source and the nickel source. During high-temperature sintering, the lithium source and the nickel source combine to form a lithium nickelate positive electrode material. The carbon coating layer is formed by carbonization of the alginate at high temperature. The carbon coating layer is continuous, stable and uniform, which prevents the electrolyte from directly contacting the lithium nickelate positive electrode material, thereby avoiding the side reaction between the lithium nickelate positive electrode material and the electrolyte, improving the thermal stability of the positive electrode material and the high-temperature cycle stability of the battery containing the positive electrode material.

[0025] In an optional embodiment, the raw material further comprises a metal salt;

[0026] Preferably, the addition amount of the metal salt is 500-6000 ppm;

[0027] Preferably, the metal salt comprises at least one of sulfate or nitrate containing Mn, Co, Mg, Zr, Ti, Nb and Sr.

[0028] The preparation method of the modified lithium nickelate positive electrode material provided by the embodiment of the application comprises the following steps: mixing raw materials containing at least alginate, betaine, a lithium source, a nickel source and a metal salt with an initiator and a crosslinking agent in water, and then heating and crosslinking to form a hydrogel. The metal salt is added in the raw materials, and the metal salt can be uniformly dispersed in the hydrogel system when the hydrogel system is formed. When sintering at high temperature, the metal ions enter the crystal structure of the lithium nickelate positive electrode material as dopants, so that the modified lithium nickelate positive electrode material with the following composition is obtained: LiNi 1-x M x O2@C, wherein M comprises at least one of Mn, Co, Mg, Zr, Ti, Nb and Sr, and x is 0.05-0.3. Experimental results prove that the specific metal ion doping can effectively overcome the problem of poor cycle stability of the lithium nickelate positive electrode material caused by lattice distortion and structure collapse in the charging and discharging process, effectively improve the structural stability of the positive electrode material, and make the prepared lithium nickelate positive electrode material have high charging and discharging capacity and excellent electrochemical performance.

[0029] In the optional embodiment, the solid-phase sintering comprises one-stage sintering and two-stage sintering.

[0030] Preferably, the sintering temperature of the one-stage sintering is 550-650℃, the heating rate is 0.5-5℃ / min, preferably 1-3℃ / min, and the sintering time is 1-5h, preferably 2-4h.

[0031] Preferably, the sintering temperature of the two-stage sintering is 680-800℃, the heating rate is 0.5-1.5℃ / min, preferably 0.75-1℃ / min, and the sintering time is 5-15h, preferably 8-12h.

[0032] Preferably, the solid-phase sintering is performed in an oxygen or air atmosphere.

[0033] The embodiment of the present application provides a preparation method of modified lithium nickelate positive electrode material, the prepared hydrogel is dried and crushed, and then the modified lithium nickelate positive electrode material is obtained through solid phase sintering, wherein the solid phase sintering includes one-stage sintering and two-stage sintering, the one-stage sintering temperature is controlled in the range of 550-650 DEG C, which is beneficial to high-temperature carbonization of alginate, and a uniform and stable carbon coating layer is formed on the surface of the lithium nickelate positive electrode material, meanwhile, when the raw material contains metal salt, the one-stage sintering can make the metal ions uniformly diffuse in the crystal structure, forming a metal-doped lithium nickelate positive electrode material, avoiding the problem that when the temperature is lower than 550 DEG C, the metal elements cannot be relatively uniformly diffused in the crystal structure, and further causing the lattice constant of the target product to be too high and the air stability to be reduced, and also avoiding the problem that when the temperature is too high, the material is over-sintered, causing the lattice constant to increase, and the air stability to be reduced due to the fact that the alginate is completely or partially burned. The two-stage sintering is carried out at 680-800 DEG C, so that the intermediate sintering product obtained through the one-stage sintering is in a suitable temperature range, avoiding over-sintering or the problem that the sintering temperature is too low, causing the lattice constant to be abnormal, so as to realize the purpose of further stabilizing the lattice, and obtain the modified lithium nickelate positive electrode material with good phase formation, that is, stable crystal structure. Further, the one-stage sintering and the two-stage sintering are carried out in an oxygen atmosphere or an air atmosphere; in the oxygen atmosphere or the air atmosphere, the structure of the formed lithium nickelate positive electrode material is more firm. The oxygen atmosphere or the air atmosphere is provided in a manner known to those skilled in the art.

[0034] In an optional embodiment, the mass ratio or molar ratio of the alginate, the betaine substance, the lithium source and the nickel source in the raw material is (8-10):(1-3):(1-2):(0.5-1);

[0035] And / or, the alginate includes one salt, multiple salts or a composite salt of sodium alginate, magnesium alginate, calcium alginate, potassium alginate and ammonium alginate;

[0036] And / or, the betaine substance includes at least one of alkyl betaine, alkyl amide betaine, hydroxypropyl betaine, hydroxypropyl betaine and phospholipid betaine;

[0037] And / or, the lithium source includes at least one of Li2SO4, LiNO3, Li2CO3 and LiOH;

[0038] And / or, the nickel source includes at least one of NiSO4, Ni(NO3)2, NiCO3 and Ni(OH)2.

[0039] In an optional embodiment, the crosslinking agent is N,N-methylene bisacrylamide (BIS); preferably, the amount of the crosslinking agent is 1%-3%;

[0040] And / or, the initiator is ammonium persulfate (APS), preferably, the amount of the initiator is 1%-5%.

[0041] In an optional embodiment, the preparation of the alginate aqueous solution comprises: adding alginate into water and heating and stirring until completely dissolved, standing overnight to obtain a transparent and uniform alginate aqueous solution.

[0042] Preferably, the heating temperature is controlled at 20-80℃, preferably 30-40℃.

[0043] Preferably, the stirring rate is controlled at 200-500 rad / min, preferably 300-400 rad / min.

[0044] Preferably, the concentration of the alginate aqueous solution is 0.1%-10%, preferably 2%-4%.

[0045] The embodiment of the present application provides a preparation method of a modified lithium nickelate positive electrode material, which comprises the following steps: preparing an alginate aqueous solution, and then mixing the alginate aqueous solution with betaine, a lithium source, a nickel source and a metal salt to prepare a mixed raw material aqueous solution. In the preparation of the alginate aqueous solution, the alginate is not easy to dissolve, and has a large viscosity when dissolved in water. Therefore, the alginate is first added into water, and then heated and stirred to accelerate the dissolution of the alginate. After the alginate is completely dissolved, the solution is left to stand overnight, so that a completely transparent and uniform alginate aqueous solution can be obtained. Then, the alginate aqueous solution is mixed with other materials to obtain a uniform raw material mixed solution, which is beneficial to the formation of a uniform hydrogel in the later stage.

[0046] In a second aspect, the embodiment of the present application provides a modified lithium nickelate positive electrode material prepared by the above preparation method, wherein the lithium nickelate positive electrode material comprises LiNi 1-x M x O2, M comprises at least one of Mn, Co, Mg, Zr, Ti, Nb and Sr, and x is 0.05-0.3.

[0047] In an optional embodiment, the particle surface of the lithium nickelate positive electrode material has a carbon coating layer, the mass of the carbon coating layer accounts for 3%-6% of the total mass of the particles of the modified lithium nickelate positive electrode material, and the thickness of the carbon coating layer is 0.01-0.2.

[0048] It can be seen that the modified lithium nickelate positive material is provided by the embodiment of the present application. Thanks to the unique preparation method of the precursor, the raw materials in the whole system can be uniformly distributed by the hydrogel with good properties, which can not only realize the uniform distribution of metal ions in the crystal, improve the microstructure defects of the positive material, and effectively improve the structural stability of the material, but also can ensure the uniformity and consistency of the carbon coating on the surface of the lithium nickelate positive material after high-temperature sintering, which is beneficial to improving the cycle stability of the material in the charging and discharging process. In the embodiment of the present application, the lithium nickelate positive material is modified by one or both of doping and coating. The metal ion doping is beneficial to overcoming the defects such as poor cycle stability caused by lattice distortion and structure collapse, and the carbon coating layer improves the stability of the whole material, so that the obtained modified lithium nickelate positive material has high charging and discharging capacity and excellent electrochemical performance.

[0049] In a third aspect, the embodiment of the present application also provides a lithium battery. The positive electrode of the lithium battery comprises the modified lithium nickelate positive material described above.

[0050] The features and performances of the present application are further described in detail below in combination with embodiments.

[0051] Embodiment 1

[0052] (1) 4g of sodium alginate was weighed and dissolved in deionized water, heated to 40℃ and stirred at a stirring rate of 200 rad / min. After complete dissolution, it was left overnight to prepare a sodium alginate solution.

[0053] (2) 12mL of the sodium alginate solution was weighed in a beaker, 5g of betaine derivative (DMAPS), 8g of LiNO3, 20g of Ni(OH)2, 1g of Mn(NO3)2, 0.01g of BIS and 0.01g of APS were added, and stirred until completely dissolved. The mixed solution was poured into a mold, reacted at 60℃ for 8h, and then taken out and freeze-dried.

[0054] (3) The powder obtained by freeze-drying was ground and placed in a tube furnace. In an oxygen atmosphere, it was first heated from room temperature to 550℃ at a heating rate of 1℃ / min, and then reacted at 700℃ for 12h at a heating rate of 0.6℃ / min to obtain the modified lithium nickelate positive material, which is recorded as LNO1.

[0055] Embodiment 2

[0056] (1) 4g of sodium alginate was weighed and dissolved in deionized water, heated to 40℃ and stirred at a stirring rate of 200 rad / min. After complete dissolution, it was left overnight to prepare a sodium alginate solution.

[0057] (2) Take 12 mL of sodium alginate solution in a beaker, add 5 g of betaine derivative (DMAPS), 8 g of LiNO3, 20 g of Ni(OH)2, 1 g of Mn(NO3)2, 0.01 g of BIS, 0.01 g of APS, and stir until completely dissolved. Pour the mixed solution into a mold, react at 60°C for 8 h, and freeze-dry after taking out.

[0058] (3) The freeze-dried powder is ground and placed in a tube furnace, heated to 550°C at a rate of 1 / min under an oxygen atmosphere, and reacted for 5 h. Then, heated to 700°C at a rate of 0.6°C / min, and reacted for 12 h to obtain a modified lithium nickelate positive electrode material, denoted as LNO2.

[0059] Example 3

[0060] (1) Weigh 4 g of sodium alginate into deionized water, heat to 40°C and stir, the stirring rate is 200 rad / min, and let stand overnight to prepare a sodium alginate solution.

[0061] (2) Take 12 mL of sodium alginate solution in a beaker, add 5 g of betaine derivative (DMAPS), 8 g of LiNO3, 20 g of Ni(OH)2, 1 g of Mn(NO3)2, 0.01 g of BIS, 0.01 g of APS, and stir until completely dissolved. Pour the mixed solution into a mold, react at 60°C for 8 h, and freeze-dry after taking out.

[0062] (3) The freeze-dried powder is ground and placed in a tube furnace, heated to 550°C at a rate of 1 / min under an oxygen atmosphere, and reacted for 5 h. Then, heated to 700°C at a rate of 0.7°C / min, and reacted for 12 h to obtain a modified lithium nickelate positive electrode material, denoted as LNO3.

[0063] Example 4

[0064] (1) Weigh 4 g of sodium alginate into deionized water, heat to 40°C and stir, the stirring rate is 200 rad / min, and let stand overnight after complete dissolution to prepare a sodium alginate solution.

[0065] (2) Take 15 mL of sodium alginate solution in a beaker, add 6 g of betaine derivative (DMAPS), 8 g of LiNO3, 20 g of Ni(OH)2, 1 g of Mn(NO3)2, 0.01 g of BIS, 0.01 g of APS, and stir until completely dissolved. Pour the mixed solution into a mold, react at 60°C for 8 h, and freeze-dry after taking out.

[0066] (3) The powder obtained by freeze-drying was ground and crushed, and then placed in a tube furnace. Under an oxygen atmosphere, the temperature was first raised from room temperature to 550℃ at a rate of 1℃ / min, and then held for 5h. Subsequently, the temperature was raised to 700℃ at a rate of 0.7℃ / min, and then held for 12h to obtain the modified lithium nickelate positive electrode material, denoted as LNO4.

[0067] Comparative Example 1

[0068] (1) 8g of LiNO3 and 20g of commercial Ni(OH)2 were weighed.

[0069] (2) The powder was uniformly mixed and then placed in a tube furnace. Under an oxygen atmosphere, the temperature was first raised from room temperature to 550℃ at a rate of 1℃ / min, and then held for 5h. Subsequently, the temperature was raised to 700℃ at a rate of 0.7℃ / min, and then held for 12h to obtain the modified lithium nickelate positive electrode material.

[0070] The particle size data of the lithium nickelate positive electrode materials obtained in Examples 1-4 and Comparative Example 1 are shown in Table 1. It can be seen that the particle size is relatively uniform and small.

[0071] Table 1

[0072] Sample batch number D10 D50 D90 D97 D99 LNO1 4.00 9.50 19.60 25.30 29.30 LNO2 1.19 6.40 56.50 94.40 121.00 LNO3 1.19 3.58 31.70 58.10 78.40 LNO4 3.74 8.51 17.80 23.40 27.30 Comparative Example 1 3.19 9.72 20.8 27.4 33.4

[0073] The XRD pattern of the modified lithium nickelate positive electrode material prepared in Example 1-4 is shown in Figure 1 , compared with the XRD of the lithium nickelate standard card. From Figure 1 , it can be seen that the modified lithium nickelate positive electrode material has LiNiO2 diffraction peaks, and there is no obvious impurity diffraction peak in the XRD pattern of each sample, indicating that the phase purity of the sample is relatively high. The SEM pattern of the modified lithium nickelate positive electrode material prepared in Example 1-4 is shown in Figure 2 , from which it can be seen that the particles are uniformly distributed and have good sphericity. Figure 2 Comparative Example 1

[0074] ​In summary, the embodiment of the present application provides a modified lithium nickelate positive electrode material, a preparation method and application thereof. The preparation method of the modified lithium nickelate positive electrode material comprises the following steps: at least raw materials containing alginate, betaine, lithium source and nickel source are heated and cross-linked to form a hydrogel in the presence of an initiator and a cross-linking agent, and then the hydrogel is dried and crushed, and then solid-phase sintering is performed, and the modified lithium nickelate positive electrode material is obtained. The preparation method provided above can make the raw materials uniformly distributed in the whole system under the action of the cross-linking agent and the initiator, and the alginate is directly carbonized and coated on the surface of the lithium nickelate positive electrode material in the later sintering process. When the raw material system contains metal salt, metal ions are doped in the lithium nickelate particles through high-temperature sintering to form a metal ion-doped lithium nickelate positive electrode material, which can further improve the structural stability of the lithium nickelate positive electrode material. As can be seen from the above, the scheme provided in the embodiment of the present application can modify the material by one or two methods of element doping and surface coating, and realize the uniformity and consistency of carbon coating and element doping of the lithium nickelate material from the source. Compared with separately preparing the hydrogel and then adding other carbon sources, the above method provided in the embodiment of the present application not only saves the process, but also uniformly disperses the alginate and other raw materials. Experimental results show that the lithium nickelate positive electrode material prepared by the method provided in the embodiment of the present application has high charge and discharge capacity and excellent electrochemical performance.

[0075] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a modified lithium nickel oxide cathode material, characterized by, It comprises: The raw material containing at least alginate, betaine, lithium source and nickel source is heated and cross-linked to form a hydrogel in the presence of an initiator and a cross-linking agent, and then the hydrogel is dried and crushed, and then solid-phase sintering is performed to obtain the modified lithium nickelate positive material, and the surface of the lithium nickelate positive material in the modified lithium nickelate positive material has a carbon coating layer, wherein: the solid-phase sintering comprises one-stage sintering and two-stage sintering, the sintering temperature of the one-stage sintering is 550-650 DEG C, and the sintering temperature of the two-stage sintering is 680-800 DEG C, and the amount of the raw material comprises: 4g of sodium alginate is weighed and dissolved in deionized water to prepare a sodium alginate solution with a concentration of 0.1%-10%, 12mL of the sodium alginate solution is taken, 5g of betaine derivative DMAPS, 8g of LiNO3, 20g of Ni(OH)2, 1g of Mn(NO3)2, 0.01g of BIS and 0.01g of APS are added; or 4g of sodium alginate is weighed and dissolved in deionized water to prepare a sodium alginate solution with a concentration of 0.1%-10%, 15mL of the sodium alginate solution is taken, 6g of betaine derivative DMAPS, 8g of LiNO3, 20g of Ni(OH)2, 1g of Mn(NO3)2, 0.01g of BIS and 0.01g of APS are added.

2. The production method according to claim 1, characterized by, It comprises the following steps: alginate is dissolved in water to obtain an alginate aqueous solution; the remaining raw materials are added to the alginate aqueous solution and mixed, and then an initiator and a cross-linking agent are added, and after sufficient stirring, heating is performed to form a hydrogel; the hydrogel is freeze-dried and crushed, and then solid-phase sintering is performed to obtain the modified lithium nickelate positive material.

3. The method of any one of claims 1-2, wherein, The heating rate of the one-stage sintering is 0.5-5 DEG C / min.

4. The production method according to claim 3, characterized by, The heating rate of the one-stage sintering is 1-3 DEG C / min.

5. The preparation method according to claim 3, characterized in that, The sintering time of the one-stage sintering is 1-5h.

6. The production method according to claim 5, wherein The sintering time of the one-stage sintering is 2-4h.

7. The method of any one of claims 1-2, wherein, The heating rate of the two-stage sintering is 0.5-1.5 DEG C / min.

8. The preparation method according to claim 7, characterized in that, The heating rate of the two-stage sintering is 0.75-1 DEG C / min.

9. The preparation method according to claim 7, characterized in that, The sintering time of the two-stage sintering is 5-15h.

10. The method of claim 9, wherein, The sintering time of the two-stage sintering is 8-12h.

11. The method of claim 1, wherein, The solid-phase sintering is performed in an oxygen or air atmosphere.

12. The method of claim 2, wherein, The preparation of the alginate aqueous solution comprises: adding alginate to water and heating and stirring until completely dissolved, standing overnight to obtain a transparent and uniform alginate aqueous solution.

13. The method of claim 12, wherein, The heating temperature is controlled at 20-80 DEG C.

14. The method of claim 13, wherein, The heating temperature is controlled at 30-40 DEG C.

15. The method of claim 12, wherein, The stirring rate is controlled at 200-500 rad / min.

16. The method of claim 15, wherein, The stirring rate is controlled at 300-400 rad / min.

17. The method of claim 16, wherein the method further comprises, The concentration of the alginate aqueous solution is 2%-4%.

18. A modified lithium nickel oxide cathode material prepared according to the method of any one of claims 1-17, wherein, The surface of the lithium nickelate positive material has a carbon coating layer, and the mass of the carbon coating layer accounts for 3%-6% of the total mass of the particles of the modified lithium nickelate positive material.

19. A lithium battery, characterized by The positive electrode of the lithium battery comprises the modified lithium nickelate positive material prepared by the preparation method of any one of claims 1-17 or the modified lithium nickelate positive material of claim 18.

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