Preparation method of sodium ion battery cathode material, cathode plate and sodium ion battery

Abstract

The invention belongs to the technical field of sodium-ion batteries, and particularly discloses a preparation method of a sodium-ion battery cathode material, and the preparation method comprises the following steps: S1, mixing a substrate material with deionized water to prepare mixed slurry; s2, treating a metal salt and a precipitant, and adding the treated metal salt and precipitant into the mixed slurry to prepare precursor slurry; s3, centrifuging, washing and drying the precursor slurry to prepare a precursor material; and S4, uniformly mixing the precursor material, sodium salt and sodium fluoride, grinding, sieving and calcining to prepare the sodium ion cathode material. According to the sodium ion battery cathode material provided by the invention, the conductivity of the sodium ion battery cathode material can be improved, and the cycle performance of the battery can also be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a method for preparing a cathode material for a sodium ion battery, a cathode sheet and a sodium ion battery. Background Art

[0002] Sodium-ion battery is a secondary battery (rechargeable battery) with a working principle similar to that of lithium-ion battery. It mainly stores and releases electrical energy based on the insertion / deintercalation process of sodium ions between the positive and negative electrodes. During charging, sodium ions are extracted from the positive electrode material and embedded in the negative electrode material through the electrolyte. At the same time, electrons move from the positive electrode to the negative electrode through the external circuit to maintain the charge balance of the entire system. The discharge process is the opposite of the charging process. Sodium ions are extracted from the negative electrode material and migrate back to the positive electrode through the electrolyte. At the same time, electrons flow back to the positive electrode through the external circuit to release electrical energy.

[0003] Sodium-ion batteries are mainly composed of positive electrodes, negative electrodes, separators, current collectors, electrolytes, etc. According to whether their constituent materials directly participate in electrochemical reactions, they can be divided into active materials and inactive materials. Among them, active materials include positive electrode materials, negative electrode materials, and electrolyte materials, and inactive materials include separators, current collectors, conductive agents, binders, etc.

[0004] Transition metal layered oxides are one of the mainstream materials for sodium-ion battery cathodes. They have a layered structure that provides a larger diffusion channel for sodium ions, which is beneficial to the rapid transport of sodium ions within the material. They also have a higher specific capacity and energy density, which enables them to meet the needs of high energy density and have broad application prospects in sodium-ion batteries.

[0005] Transition metal layered oxides have a general formula of Na x MO 2 , by edge-to-edge MO 6 Octahedral sheet composition, of which Na + Located in MO 6 The octahedral sheets form a layered structure. The disadvantages of the prior art are that the conductivity of the transition metal layered oxide is poor and the material structure is unstable, resulting in poor battery cycle performance. Summary of the invention

[0006] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a sodium ion battery cathode material, which can improve its conductivity and improve the cycle performance of the battery.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a cathode material for a sodium ion battery, the preparation method comprising the following steps:

[0009] S1: mixing the substrate material with deionized water to prepare a mixed slurry;

[0010] S2: adding the treated metal salt and precipitant into the mixed slurry to prepare a precursor slurry;

[0011] S3: preparing a precursor material by centrifuging, washing and drying the precursor slurry;

[0012] S4: After the precursor material, sodium salt and sodium fluoride are evenly mixed, they are ground, sieved and calcined to prepare a sodium ion cathode material.

[0013] Furthermore, the specific process of step S1 is: mixing the substrate material with deionized water, stirring at room temperature for 1-2 hours to prepare a substrate slurry, ultrasonically treating the substrate slurry, and then placing it in a homogenizer for 30-60 minutes to prepare a mixed slurry;

[0014] The specific process of step S2 is: dissolving the metal salt and the precipitant in deionized water respectively, and preparing frozen metal salt and frozen precipitant after low-temperature freezing treatment, and then slowly melting the frozen metal salt and frozen precipitant at room temperature, adding the slowly melted frozen metal salt and frozen precipitant into the mixed slurry, and stirring the mixed slurry continuously, and after the addition is completed, continue stirring for 1-2 hours to prepare the precursor slurry;

[0015] The specific process of step S3 is: centrifuging the precursor slurry, repeatedly washing the precipitate after centrifugation, and after washing, drying the washed precipitate to prepare a precursor material;

[0016] The specific process of step S4 is: after the precursor material, sodium salt and sodium fluoride are mixed evenly, the cathode pre-material is prepared after grinding and screening, the cathode pre-material is calcined, and after calcination, it is cooled to room temperature to prepare the sodium ion cathode material.

[0017] Further, in step S1, the mass ratio of the substrate material to the deionized water is (1-5):100;

[0018] In step S1, during the ultrasonic treatment, the ultrasonic treatment time is 0.5-2h, and the ultrasonic power is 100-400W.

[0019] Further, in step S2, the metal in the metal salt is nickel;

[0020] The precipitant is sodium hydroxide.

[0021] Further, in step S2, the mass ratio of the metal salt to the deionized water is 1:(2-20);

[0022] The mass ratio of precipitant to deionized water is 1:(2-20);

[0023] The molar ratio of metal salt to precipitant is 1:(0.8-1.2);

[0024] The mass ratio of the total mass of the metal salt and the precipitant to the mass of the base material in the mixed slurry is (1-5):1.

[0025] Further, in step S4, the mass ratio of the precursor material, the sodium salt and the sodium fluoride is (0.8-2.0):1.0:

[0026] (0.001-0.03).

[0027] Furthermore, the base material is inorganic conductive carbon.

[0028] Furthermore, the inorganic conductive carbon is any one or more of conductive acetylene black, superconducting carbon black, conductive SP, graphite, graphene, carbon nanotubes, and single-walled carbon nanotubes mixed in any proportion.

[0029] Furthermore, during the calcination treatment in step S4, the calcination atmosphere is an inert atmosphere and a weak oxygen atmosphere, the calcination temperature is 350-450° C., and the calcination time is 1-2 h.

[0030] In a second aspect, the present invention provides a cathode sheet, which includes a sodium ion battery cathode material, and the sodium ion battery cathode material is prepared using the preparation method of the sodium ion battery cathode material provided in the embodiment of the first aspect of the present invention.

[0031] In a third aspect, the present invention provides a sodium ion battery, comprising the cathode sheet provided by the embodiment of the second aspect of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The preparation method of the sodium ion battery cathode material provided by the present invention, the introduced base material is inorganic conductive carbon, and the conductive performance is effectively improved through carbon coating and F doping, and the stability of the cathode material is improved, thereby extending the service life of the battery.

[0034] 2. In the present invention, molten frozen metal salt and frozen precipitant are added to the mixed slurry containing inorganic conductive carbon to improve the conductivity of the mixed slurry and improve the thermal stability of the mixed slurry. At the same time, through the freezing and precipitation process, the overall performance and stability of the slurry can be improved, and the processing performance of the slurry can be improved, so that the prepared sodium ion battery cathode material can improve its conductivity when used in the cathode sheet.

[0035] 3. In the present invention, the preparation process is simple and the cost is low. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In a first aspect, the present invention provides a method for preparing a cathode material for a sodium ion battery, the preparation method comprising the following steps:

[0038] S1: Preparation of mixed slurry

[0039] The base material and deionized water were mixed in a mass ratio of (1-5):100, and the base slurry was prepared after stirring at room temperature for 1-2 hours. The base slurry was ultrasonically treated and then placed in a homogenizer for 30-60 minutes to prepare a mixed slurry;

[0040] Wherein, during the ultrasonic treatment process, the ultrasonic treatment time is 0.5-2h, and the ultrasonic power is 100-400W;

[0041] The base material is inorganic conductive carbon;

[0042] Specifically, the inorganic conductive carbon can be any one or more of conductive acetylene black, superconducting carbon black, conductive SP, graphite, graphene, carbon nanotubes (CNTs), and single-walled carbon nanotubes (SWCNTs) mixed in any proportion;

[0043] S2: Preparation of precursor slurry

[0044] The metal salt and the precipitant are dissolved in deionized water respectively, and after low-temperature freezing treatment, frozen metal salt and frozen precipitant are prepared, and then the frozen metal salt and frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1-2 hours to prepare a precursor slurry;

[0045] The metal in the metal salt is nickel. Specifically, the metal salt may be NiCl 2、NiSO 4 ,Ni(NO 3 ) 2 Any one or more of the above are mixed in any proportion;

[0046] Sodium hydroxide is used as the precipitant;

[0047] The mass ratio of the metal salt to the deionized water is 1:(2-10), and the mass ratio of the precipitant to the deionized water is 1:(2-10);

[0048] The molar ratio of metal salt to precipitant is 1:(0.8-1.2);

[0049] The mass ratio of the total mass of the metal salt and the precipitant to the mass of the base material in the mixed slurry is (1-5): 1;

[0050] S3: Preparation of precursor materials

[0051] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed 2-3 times. After washing, the precipitate after washing is dried to prepare a precursor material;

[0052] S4: Preparation of cathode materials

[0053] The precursor material, sodium salt and sodium fluoride are uniformly mixed in a mass ratio of (0.8-2.0):1.0:(0.001-0.03), and then ground and sieved to prepare a cathode pre-material, and the cathode pre-material is calcined and cooled to room temperature after calcination to prepare a sodium ion cathode material;

[0054] Wherein, the sodium salt is any one or more of sodium carbonate, sodium bicarbonate, and sodium dihydrogen phosphate mixed in any proportion;

[0055] Wherein, during the calcination process, when the substrate material is inorganic conductive carbon, during the calcination process in step S4, the calcination atmosphere is an inert atmosphere or a weak oxygen atmosphere (in a weak oxygen atmosphere, O 2 <2%), the calcination temperature is 350-450°C, and the calcination time is 1-2h.

[0056] In a second aspect, the present invention provides a cathode sheet, which includes a sodium ion battery cathode material, and the sodium ion battery cathode material is prepared using the preparation method of the sodium ion battery cathode material provided in the embodiment of the first aspect of the present invention.

[0057] In a third aspect, the present invention provides a sodium ion battery, comprising the cathode sheet provided by the embodiment of the second aspect of the present invention.

[0058] The following are specific examples.

[0059] Example 1

[0060] This embodiment provides a method for preparing a cathode material for a sodium ion battery, which is as follows:

[0061] S1: Preparation of mixed slurry

[0062] Superconducting carbon black and deionized water were mixed in a mass ratio of 2:100, and the mixture was stirred at room temperature for 1.5 hours to prepare a base slurry. The base slurry was ultrasonically treated for 1 hour at an ultrasonic power of 200 W, and then placed in a homogenizer for 45 minutes to prepare a mixed slurry.

[0063] S2: Preparation of precursor slurry

[0064] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1.5 hours to prepare a precursor slurry;

[0065] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:5, and the mass ratio of NaOH to deionized water is 1:5;

[0066] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0067] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH and superconducting carbon black in the mixed slurry is 3:1;

[0068] S3: Preparation of precursor materials

[0069] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed twice. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0070] S4: Preparation of cathode materials

[0071] The precursor material, sodium carbonate and sodium fluoride were uniformly mixed in a mass ratio of 1:1.0:0.10, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 400° C. in an inert atmosphere for 1.5 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0072] Example 2

[0073] This embodiment provides a method for preparing a cathode material for a sodium ion battery, which is as follows:

[0074] S1: Preparation of mixed slurry

[0075] Superconducting carbon black and deionized water were mixed in a mass ratio of 1:100, and stirred at room temperature for 1 hour to prepare a base slurry. The base slurry was ultrasonically treated for 0.5 hours at an ultrasonic power of 400 W, and then placed in a homogenizer for 60 minutes to prepare a mixed slurry;

[0076] S2: Preparation of precursor slurry

[0077] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1 hour to prepare a precursor slurry;

[0078] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:2, and the mass ratio of NaOH to deionized water is 1:2;

[0079] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0080] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH and superconducting carbon black in the mixed slurry is 1:1;

[0081] S3: Preparation of precursor materials

[0082] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed for 3 times. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0083] S4: Preparation of cathode materials

[0084] The precursor material, sodium carbonate and sodium fluoride were uniformly mixed in a mass ratio of 0.8:1.0:0.001, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 350° C. in an inert atmosphere for 2 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0085] Example 3

[0086] This embodiment provides a method for preparing a cathode material for a sodium ion battery, which is as follows:

[0087] Superconducting carbon black and deionized water were mixed in a mass ratio of 5:100, and stirred at room temperature for 2 hours to prepare a base slurry. The base slurry was ultrasonically treated for 2 hours at an ultrasonic power of 100 W, and then placed in a homogenizer for 30 minutes to prepare a mixed slurry;

[0088] S2: Preparation of precursor slurry

[0089] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 2 hours to prepare a precursor slurry;

[0090] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:10, and the mass ratio of NaOH to deionized water is 1:10;

[0091] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0092] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH and superconducting carbon black in the mixed slurry is 5:1;

[0093] S3: Preparation of precursor materials

[0094] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed for 3 times. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0095] S4: Preparation of cathode materials

[0096] The precursor material, sodium carbonate and sodium fluoride were uniformly mixed in a mass ratio of 2.0:1.0:0.03, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 450° C. in an inert atmosphere for 1 hour, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0097] Example 4

[0098] This embodiment provides a method for preparing a cathode material for a sodium ion battery, which is as follows:

[0099] S1: Preparation of mixed slurry

[0100] Conductive acetylene carbon black and deionized water were mixed in a mass ratio of 2:100, and stirred at room temperature for 1.5 hours to prepare a base slurry. The base slurry was ultrasonically treated for 1 hour at an ultrasonic power of 200 W, and then placed in a homogenizer for 45 minutes to prepare a mixed slurry;

[0101] S2: Preparation of precursor slurry

[0102] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1.5 hours to prepare a precursor slurry;

[0103] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:5, and the mass ratio of NaOH to deionized water is 1:5;

[0104] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0105] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH and the mass ratio of the conductive acetylene black in the mixed slurry is 3:1;

[0106] S3: Preparation of precursor materials

[0107] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed twice. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0108] S4: Preparation of cathode materials

[0109] The precursor material, sodium carbonate and sodium fluoride were uniformly mixed in a mass ratio of 1:1.0:0.10, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 400° C. in an inert atmosphere for 1.5 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0110] Example 5

[0111] This embodiment provides a method for preparing a cathode material for a sodium ion battery, which is as follows:

[0112] S1: Preparation of mixed slurry

[0113] The single-walled carbon nanotubes and deionized water were mixed in a mass ratio of 2:100, and stirred at room temperature for 1.5 hours to prepare a base slurry. The base slurry was ultrasonically treated for 1 hour at an ultrasonic power of 200 W, and then placed in a homogenizer for 45 minutes to prepare a mixed slurry;

[0114] S2: Preparation of precursor slurry

[0115] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1.5 hours to prepare a precursor slurry;

[0116] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:5, and the mass ratio of NaOH to deionized water is 1:5;

[0117] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0118] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH to the mass ratio of the single-walled carbon nanotubes in the mixed slurry is 3:1;

[0119] S3: Preparation of precursor materials

[0120] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed twice. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0121] S4: Preparation of cathode materials

[0122] The precursor material, sodium carbonate and sodium fluoride were uniformly mixed in a mass ratio of 1:1.0:0.10, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 400° C. in an inert atmosphere for 1.5 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0123] Comparative Example 1

[0124] This comparative example provides a method for preparing a cathode material for a sodium ion battery. The difference from Example 1 is that in this comparative example, the sodium fluoride in step S4 is removed. The specific preparation process is as follows:

[0125] S1: Preparation of mixed slurry

[0126] Superconducting carbon black and deionized water were mixed in a mass ratio of 2:100, and the mixture was stirred at room temperature for 1.5 hours to prepare a base slurry. The base slurry was ultrasonically treated for 1 hour at an ultrasonic power of 200 W, and then placed in a homogenizer for 45 minutes to prepare a mixed slurry.

[0127] S2: Preparation of precursor slurry

[0128] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1.5 hours to prepare a precursor slurry;

[0129] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:5, and the mass ratio of NaOH to deionized water is 1:5;

[0130] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0131] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH and superconducting carbon black in the mixed slurry is 3:1;

[0132] S3: Preparation of precursor materials

[0133] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed twice. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0134] S4: Preparation of cathode materials

[0135] The precursor material and sodium carbonate were uniformly mixed in a mass ratio of 1:1.0, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 400° C. in an inert atmosphere for 1.5 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0136] Comparative Example 2

[0137] This comparative example provides a method for preparing a cathode material for a sodium ion battery. The difference from Example 1 is that in this comparative example, the superconducting carbon black in step S1 is replaced by a mixture of metal oxides (i.e., FeO, Mn 2 O 3 The mixture is mixed uniformly according to a molar ratio of 2:1), and the sodium fluoride in step S4 is removed. The specific preparation process is as follows:

[0138] S1: Preparation of mixed slurry

[0139] The metal oxide mixture was mixed with deionized water at a mass ratio of 2:100, and stirred at room temperature for 1.5 hours to prepare a base slurry. The base slurry was ultrasonically treated for 1 hour at an ultrasonic power of 200 W, and then placed in a homogenizer for 45 minutes to prepare a mixed slurry;

[0140] S2: Preparation of precursor slurry

[0141] Will Ni(NO 3 ) 2 and NaOH are dissolved in deionized water respectively, and after low-temperature freezing treatment, a frozen metal salt and a frozen precipitant are prepared, and then the frozen metal salt and the frozen precipitant are slowly melted at room temperature, and the slowly melted frozen metal salt and the frozen precipitant are added to the mixed slurry, and the mixed slurry is continuously stirred. After the addition is completed, the stirring is continued for 1.5 hours to prepare a precursor slurry;

[0142] Ni(NO 3 ) 2 The mass ratio of NaOH to deionized water is 1:5, and the mass ratio of NaOH to deionized water is 1:5;

[0143] Ni(NO 3 ) 2 The molar ratio of NH4OH to NaOH is 1:1;

[0144] Ni(NO 3 ) 2 The mass ratio of the total mass of NaOH to the mass ratio of the mixture of metal oxides in the mixed slurry is 3:1;

[0145] S3: Preparation of precursor materials

[0146] The precursor slurry is centrifuged, and the precipitate after centrifugation is repeatedly washed twice. After the washing is completed, the washed precipitate is dried to prepare a precursor material;

[0147] S4: Preparation of cathode materials

[0148] The precursor material and sodium carbonate were uniformly mixed in a mass ratio of 1:1.0, and then ground and sieved to prepare a cathode pre-material. The cathode pre-material was calcined at 400° C. in an inert atmosphere for 1.5 h, and then cooled to room temperature after calcination to prepare a sodium ion cathode material.

[0149] Experimental example

[0150] The sodium ion cathode materials prepared in Examples 1-5 and Comparative Examples 1-2 were assembled into sodium ion batteries, and then the performance of the assembled sodium ion batteries was tested.

[0151] Among them, the assembly method of the sodium ion battery is as follows:

[0152] The prepared sodium ion cathode material was ground in a mortar and passed through a 200-mesh sieve. The sodium ion cathode material, conductive carbon powder, and 12 wt% PVDF (wherein the solvent is NMP) were mixed in a mass ratio of 7:1:1, and then stirred with a magnetic stirrer for 2 hours to prepare a slurry. The slurry was coated on an aluminum foil using an automatic coating machine, dried in an oven at 50°C, and then dried in a vacuum drying oven at 110°C for 12 hours to obtain an aluminum foil sheet. The aluminum foil sheet was pressed by a small roller press and punched by a slicer to obtain a cathode sheet. The cathode sheet was placed in a glove box for buckling. 2032 battery assembly, specifically, the cathode sheet is placed in the middle of the positive electrode shell, and 35uL of electrolyte is measured and dripped on the electrode sheet; a glass fiber diaphragm sheet is placed on the cathode sheet of the sodium ion battery, and 35uL of electrolyte is dripped on the glass fiber diaphragm sheet. After the electrolyte completely soaks the glass fiber diaphragm sheet, a conductive steel sheet is placed on the reference electrode; the reference electrode is then placed in the center of the diaphragm, a metal gasket is added to the conductive steel sheet, and finally the negative electrode shell is covered, and the button battery packaging machine is used for sealing. After standing and activating for 10 hours, a sodium ion battery is prepared.

[0153] The electrolyte is a 1 mol / L sodium perchlorate PC solution, the diaphragm is a glass fiber diaphragm, and the reference electrode is a sodium sheet.

[0154] The electrochemical performance of the prepared sodium ion battery was tested at 0.1C and 1C rates, respectively. The test results are shown in Table 1.

[0155] Table 1

[0156]

[0157] It can be seen from the data in Table 1 that the performance parameters of the sodium ion battery cathode materials provided by Examples 1-5 of the present invention have been significantly improved compared with those of Comparative Examples 1-2, among which the effect of Example 1 is the best;

[0158] It can be seen from the data of Examples 1-5 and Comparative Example 1 that in the embodiments of the present invention, fluorine doping can improve the battery performance and cycle stability;

[0159] It can be seen from the data of Examples 1-5 and Comparative Example 2 that in the embodiments of the present invention, the conductivity of the prepared sodium ion battery can also be improved by carbon coating.

[0160] Therefore, the sodium ion battery cathode material provided by the present invention has an inorganic conductive carbon as the introduced base material, which can effectively improve the conductivity and stability of the cathode material through carbon coating and F doping, thereby extending the service life of the battery.

[0161] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0162] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a sodium ion battery cathode material, characterized in that: The preparation method comprises the following steps: S1: mixing the substrate material with deionized water to prepare a mixed slurry; S2: adding the treated metal salt and precipitant into the mixed slurry to prepare a precursor slurry; S3: preparing a precursor material by centrifuging, washing and drying the precursor slurry; S4: After the precursor material, sodium salt and sodium fluoride are evenly mixed, they are ground, sieved and calcined to prepare a sodium ion cathode material.

2. The method for preparing a sodium ion battery cathode material according to claim 1, characterized in that: The specific process of step S1 is: mixing the substrate material with deionized water, stirring at room temperature for 1-2 hours to prepare a substrate slurry, ultrasonically treating the substrate slurry, and then placing it in a homogenizer for 30-60 minutes to prepare a mixed slurry; The specific process of step S2 is: dissolving the metal salt and the precipitant in deionized water respectively, and preparing frozen metal salt and frozen precipitant after low-temperature freezing treatment, and then slowly melting the frozen metal salt and frozen precipitant at room temperature, adding the slowly melted frozen metal salt and frozen precipitant into the mixed slurry, and stirring the mixed slurry continuously, and after the addition is completed, continue stirring for 1-2 hours to prepare the precursor slurry; The specific process of step S3 is: centrifuging the precursor slurry, repeatedly washing the precipitate after centrifugation, and after washing, drying the washed precipitate to prepare a precursor material; The specific process of step S4 is: after the precursor material, sodium salt and sodium fluoride are mixed evenly, the cathode pre-material is prepared after grinding and screening, the cathode pre-material is calcined, and after calcination, it is cooled to room temperature to prepare the sodium ion cathode material.

3. The method for preparing a sodium ion battery cathode material according to claim 2, characterized in that: In step S2, the metal in the metal salt is nickel; The precipitant is sodium hydroxide.

4. The method for preparing a sodium ion battery cathode material according to claim 2, characterized in that: In step S1, the mass ratio of the substrate material to the deionized water is (1-5):100; In step S1, during the ultrasonic treatment, the ultrasonic treatment time is 0.5-2h and the ultrasonic power is 100-400W; In step S2, the mass ratio of metal salt to deionized water is 1:(2-20), the mass ratio of precipitant to deionized water is 1:(2-20), the molar ratio of metal salt to precipitant is 1:(0.8-1.2), and the mass ratio of the total mass of metal salt and precipitant to the base material in the mixed slurry is (1-5):

1.

5. The method for preparing a sodium ion battery cathode material according to claim 2, characterized in that: In step S4, the mass ratio of the precursor material, the sodium salt and the sodium fluoride is (0.8-2.0):1.0:(0.001-0.03).

6. The method for preparing a sodium ion battery cathode material according to claim 2, characterized in that: The base material is inorganic conductive carbon.

7. The method for preparing a sodium ion battery cathode material according to claim 6, characterized in that: The inorganic conductive carbon is any one or more of conductive acetylene black, superconducting carbon black, conductive SP, graphite, graphene, carbon nanotubes, and single-walled carbon nanotubes mixed in any proportion.

8. The method for preparing a sodium ion battery cathode material according to claim 2, characterized in that: During the calcination treatment in step S4, the calcination atmosphere is an inert atmosphere or a weak oxygen atmosphere, the calcination temperature is 350-450° C., and the calcination time is 1-2 hours.

9. A cathode sheet, characterized in that: The cathode sheet comprises a sodium ion battery cathode material, and the sodium ion battery cathode material is prepared by the preparation method according to any one of claims 1 to 8.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the cathode sheet as claimed in claim 9.

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