Sodium ion battery sodium supplement and preparation method thereof, sodium ion battery and positive electrode active material thereof

Abstract

The present invention belongs to the technical field of sodium ion batteries, and discloses the application of Na4CaSi3O9 as a sodium ion battery positive electrode sodium supplement. The sodium ion battery positive electrode material and Na4CaSi3O9 are mixed and used as the sodium ion battery positive electrode active material. The assembled sodium ion battery has high first coulomb efficiency and excellent cycle stability. In addition, the present invention discloses a preparation method of the sodium ion battery positive electrode sodium supplement Na4CaSi3O9.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium supplement. Background Art

[0002] Although lithium-ion batteries are the main energy storage technology for portable devices and electric vehicles, the scarcity and uneven distribution of lithium resources limit their market expansion. In contrast, sodium resources are abundant and low-cost, making sodium-ion batteries an attractive alternative to lithium-ion batteries. In the initial cycle of sodium-ion batteries, the negative electrode side irreversibly consumes the limited sodium source released from the positive electrode, resulting in a decrease in the first-cycle coulombic efficiency and thus a decrease in energy density. In a full-battery system, releasing the full capacity inherent in the positive electrode material is a complex and challenging task. Especially when used in combination with the mainstream hard carbon negative electrode, its relatively low first-cycle coulombic efficiency will inevitably trigger the irreversible consumption of active sodium, resulting in a large loss of full battery capacity. Based on the consumption and loss of sodium, the development of sodium supplementation technology is imperative. Summary of the invention

[0003] The first object of the present invention is to provide a sodium ion battery sodium supplement and a preparation method thereof.

[0004] A second object of the present invention is to provide a positive electrode active material for a sodium ion battery.

[0005] A third object of the present invention is to provide a sodium ion battery.

[0006] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0007] Firstly, the present invention provides the application of Na4CaSi3O9 as a positive electrode sodium supplement for sodium ion batteries.

[0008] Secondly, the present invention provides a method for preparing a sodium ion battery positive electrode sodium supplement Na4CaSi3O9, comprising:

[0009] A sodium source, a calcium source and a silicon source are weighed as raw materials according to a molar ratio of Na:Ca:Si=4:1:3, and the raw materials are ground, mixed and then sintered to obtain the raw materials.

[0010] In a further preferred embodiment, the sodium source is at least one of sodium carbonate, sodium acetate, and sodium oxalate; the calcium source is at least one of calcium oxide, calcium carbonate, calcium oxalate, and calcium acetate; and the silicon source is silicon dioxide.

[0011] In a further preferred embodiment, a flux is added during the grinding and mixing process. Further preferably, the flux is ammonium chloride. Further preferably, the amount of the flux added is 5%-12% of the total mass of the sodium source, the calcium source, and the silicon source.

[0012] In a further preferred embodiment, during the grinding and mixing process, anhydrous ethanol is added as a grinding liquid.

[0013] In a further preferred embodiment, the material obtained by grinding and mixing is dried and then sintered.

[0014] In a further preferred embodiment, the sintering temperature is 900-1200° C. and the sintering time is 4-8 hours.

[0015] Based on the same inventive concept, the present invention provides a sodium ion battery positive electrode active material, including a sodium ion battery positive electrode material and Na4CaSi3O9.

[0016] In a further preferred embodiment, the molar ratio of the sodium ion battery positive electrode material to Na4CaSi3O9 in the sodium ion battery positive electrode active material is 1:0.05~0.1.

[0017] In a further preferred embodiment, the chemical formula of the sodium ion battery positive electrode material is Na 0.67 Mn x Ni 1-x O2, 0<x<1; more preferably Na 0.67 Mn 0.67 Ni 0.33 O2. The positive electrode material of sodium ion battery can be made by mixing hydroxide precursor with sodium and then sintering, or it can be purchased directly.

[0018] In addition, the present invention provides a sodium ion battery, comprising the aforementioned sodium ion battery positive electrode active material.

[0019] The above one or more technical solutions of the present invention can achieve at least one of the following beneficial effects:

[0020] The invention provides a novel positive electrode sodium supplement for sodium ion batteries.

[0021] The preparation method of the sodium ion battery positive electrode sodium supplement provided by the invention is simple, easy to operate, and can be applied in large-scale industrial applications.

[0022] The positive electrode active material containing the above-mentioned positive electrode sodium supplement for sodium ion batteries of the present invention enables the sodium ion battery to have a higher initial coulombic efficiency and excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The first cycle charge and discharge curve of the button battery assembled with Na4CaSi3O9.

[0024] Figure 2 This is the cycle performance curve of the battery. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0028] Example 1

[0029] Sodium carbonate, calcium carbonate and silicon dioxide are used as raw materials, and the raw materials are weighed according to the molar ratio of Na:Ca:Si=4:1:3. 10wt% of ammonium chloride based on the total mass of sodium carbonate, calcium carbonate and silicon dioxide is added as a flux. An appropriate amount of anhydrous ethanol is added to an agate mortar, and the mixture is fully ground for 2h, and then placed in an oven for drying.

[0030] Take out the dried material, grind it and put it into a muffle furnace and sinter it at 1050℃ for 5h to obtain the sodium supplement Na4CaSi3O9.

[0031] The P2 phase cathode material Na 0.67 Mn 0.67 Ni 0.33 O2 and the sodium supplement Na4CaSi3O9 are uniformly mixed in a drying chamber at a molar ratio of 1:0.07 to obtain the active material.

[0032] Example 2

[0033] Use sodium acetate, calcium oxide and silicon dioxide as raw materials, weigh the raw materials according to the molar ratio of Na:Ca:Si=4:1:3, add 5wt% of ammonium chloride as a flux based on the total mass of sodium carbonate, calcium carbonate and silicon dioxide, add appropriate amount of anhydrous ethanol in an agate mortar, grind thoroughly for 2h, and then put it in an oven to dry.

[0034] Take out the dried material, grind it, and put it into a muffle furnace and sinter it at 900℃ for 8h to obtain the sodium supplement Na4CaSi3O9.

[0035] The P2 phase cathode material Na 0.67 Mn 0.67 Ni 0.33 O2 and the sodium supplement Na4CaSi3O9 are uniformly mixed in a drying chamber at a molar ratio of 1:0.08 to obtain the active material.

[0036] Example 3

[0037] Use sodium oxalate, calcium acetate and silicon dioxide as raw materials, weigh the raw materials according to the molar ratio of Na:Ca:Si=4:1:3, add 8wt% of ammonium chloride as a flux based on the total mass of sodium carbonate, calcium carbonate and silicon dioxide, add appropriate amount of anhydrous ethanol in an agate mortar, grind thoroughly for 2h, and then put it in an oven to dry.

[0038] Take out the dried material, grind it, and put it into a muffle furnace and sinter it at 1200℃ for 4h to obtain the sodium supplement Na4CaSi3O9.

[0039] The P2 phase cathode material Na 0.67 Mn 0.67 Ni 0.33 O2 and the sodium supplement Na4CaSi3O9 are uniformly mixed in a drying chamber at a molar ratio of 1:0.06 to obtain the active material.

[0040] Example 4

[0041] Sodium oxalate, calcium oxalate and silicon dioxide are used as raw materials, and the raw materials are weighed according to the molar ratio of Na:Ca:Si=4:1:3. 12wt% of ammonium chloride based on the total mass of sodium carbonate, calcium carbonate and silicon dioxide is added as a flux. An appropriate amount of anhydrous ethanol is added to an agate mortar, and the mixture is fully ground for 2h, and then placed in an oven for drying.

[0042] Take out the dried material, grind it, and put it into a muffle furnace and sinter it at 1000℃ for 4h to obtain the sodium supplement Na4CaSi3O9.

[0043] The P2 phase cathode material Na 0.67 Mn 0.67 Ni 0.33 O2 and the sodium supplement Na4CaSi3O9 are uniformly mixed in a drying chamber at a molar ratio of 1:0.05 to obtain the active material.

[0044] Example 5

[0045] Sodium carbonate, calcium acetate and silicon dioxide are used as raw materials, and the raw materials are weighed according to the molar ratio of Na:Ca:Si=4:1:3. 10wt% of ammonium chloride based on the total mass of sodium carbonate, calcium carbonate and silicon dioxide is added as a flux. An appropriate amount of anhydrous ethanol is added to an agate mortar, and the mixture is fully ground for 2h, and then placed in an oven for drying.

[0046] Take out the dried material, grind it, and put it into a muffle furnace and sinter it at 1100℃ for 4h to obtain the sodium supplement Na4CaSi3O9.

[0047] The P2 phase cathode material Na 0.67 Mn0.67 Ni 0.33 O2 and the sodium supplement Na4CaSi3O9 are uniformly mixed in a drying chamber at a molar ratio of 1:0.1 to obtain the active material.

[0048] (1) Testing the first cycle charge and discharge curve of button cells assembled with Na4CaSi3O9

[0049] Na4CaSi3O9, acetylene black and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a slurry. The slurry was coated on aluminum foil and dried to obtain a positive electrode. A button cell was assembled in a glove box using metallic sodium as the negative electrode, sodium electrolyte Whatman GF / D as the diaphragm, and 1M NaClO4in DMC:EC=1:1 Vol% with 5%FEC as the electrolyte.

[0050] The first cycle charge and discharge curve of the battery was tested under the conditions of voltage 2~4V and 0.1C. The results are as follows Figure 1 The button cell has a charge capacity of 178.6 mAh / g and a discharge capacity of 118.2 mAh / g, and is suitable as a sodium supplement material.

[0051] (2) Testing the active materials obtained in Examples 1-5 and the P2 phase positive electrode material Na 0.67 Mn 0.67 Ni 0.33 Electrical performance of button cells assembled with O2

[0052] The active materials obtained in Examples 1-5 and the P2 phase positive electrode material Na 0.67 Mn 0.67 Ni 0.33 O2, acetylene black and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a slurry. The slurry was coated on aluminum foil and dried to obtain a positive electrode. A button cell was assembled in a glove box using hard carbon as the negative electrode, sodium electrolyte Whatman GF / D as the diaphragm, and 1MNaPF6inDEC:EC=1:1 Vol%with 5%FEC as the electrolyte.

[0053] The battery was tested for 50 cycles at 2~4V and 0.5C. Figure 2 As shown. P2 phase positive electrode material Na 0.67 Mn 0.67 Ni 0.33 The capacity retention rate of the battery assembled by adding sodium supplement Na4CaSi3O9 to O2 is greatly improved during the cycle process.

[0054] Under the conditions of 2~4V and 0.1C, the active material obtained in Example 1 and the P2 phase positive electrode material Na 0.67 Mn 0.67 Ni 0.33 The first cycle coulombic efficiency of the battery assembled with O2 is shown in Table 1. It can be seen that after the sodium supplement is used in the positive electrode material, the first cycle coulombic efficiency of the battery is significantly improved.

[0055] Table 1

[0056]

[0057] After applying the sodium supplement, the first cycle coulomb efficiency of the battery was improved, and the capacity retention rate during the cycle was significantly improved. This may be because: Na4CaSi3O9 has 4 moles of sodium per unit molecular formula, which sacrifices itself at high potential and produces Na by oxidative decomposition. + ions, compensating for sodium consumption and effectively reducing the loss of sodium ions. Na4CaSi3O9 belongs to the cubic system in crystal structure and has Pa3 space group. In the unit cell, Na4CaSi3O9 consists of eight Si6O 18 Rings are composed of six SiO4 tetrahedra coordinated by 64 Na and 16 Ca ions, so they still have good structural stability after providing sodium ions.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Application of Na4CaSi3O9 as a positive electrode sodium supplement for sodium ion batteries.

2. A sodium ion battery positive electrode active material, characterized in that: Including sodium ion battery positive electrode materials and Na4CaSi3O9.

3. The sodium ion battery positive electrode active material according to claim 2, characterized in that The molar ratio of the sodium ion battery positive electrode material to Na4CaSi3O9 is 1:0.05~0.

1.

4. The sodium ion battery positive electrode active material according to claim 2, characterized in that The chemical formula of the sodium ion battery positive electrode material is Na 0.67 Mn x Ni 1-x O2, 0<x<1.

5. A sodium ion battery, characterized in that: The invention comprises the positive electrode active material of a sodium ion battery according to any one of claims 2 to 4.

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