A positive electrode sodium supplement material for a sodium ion battery and a preparation method and application thereof

Abstract

The application provides a positive electrode sodium supplement material for a sodium ion battery and a preparation method and application thereof. a Fe 1‑x‑y‑z Al x Ti y Mg z O2, wherein a, x, y and z are molar fractions, 0.8<=a<=1.5, 0.05<=x<=0.3, 0.05<=y<=0.3 and 0.05<=z<=0.3. Compared with the prior art, the positive electrode sodium supplement material contains multiple elements of iron, aluminum, titanium and magnesium, the above-mentioned substances are mixed and prepared through multiple tests, the obtained novel sodium supplement compound has good compatibility with the positive electrode active material, the capacity loss of the battery in the first charge-discharge process can be effectively reduced in the positive electrode sheet, and thus the energy density and the cycle performance of the sodium ion single battery are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sodium batteries, in particular to a positive electrode sodium supplement material for sodium ion batteries and a preparation method and application thereof. BACKGROUND

[0002] Sodium resources are extremely abundant, low in price and widely distributed. Sodium-based secondary batteries have the advantage of low cost. Sodium ion batteries and lithium ion batteries have similar working principles, and utilize sodium ions to shuttle between the positive and negative electrodes to realize charging and discharging. Because the sodium ion radius is large, it cannot be embedded in the graphite layer, so the sodium ion battery uses hard carbon as the negative electrode material, and the sodium ion is embedded in the micropores and mesopores of the hard carbon negative electrode and forms a large amount of SEI film, resulting in excessive consumption of sodium ions. Thus, the first coulombic efficiency of the sodium ion battery is low, which reduces the energy density of the sodium ion battery. At present, sodium ions are supplemented to the sodium ion battery to solve the problem of low first coulombic efficiency of the sodium ion battery.

[0003] At present, the methods for supplementing sodium ions to sodium ion batteries mainly include melting metal sodium into the negative electrode, spraying organic sodium solution onto the negative electrode, and adding positive electrode additives to supplement sodium ions. Both metal sodium and organic sodium solution directly use metal sodium. This process has extremely strict requirements on the production environment, is difficult to mass-produce, and has safety hazards. The sodium supplement technology with application prospects is the positive electrode additive sodium supplement method. Currently used positive electrode sodium supplement materials such as sodium phosphide, sodium carbonate and organic sodium salt have low sodium supplement efficiency, poor compatibility with positive electrode materials, and negative effects on the cycle performance of the battery.

[0004] Therefore, it is necessary to provide a technical solution to solve the above problems. SUMMARY

[0005] One of the purposes of the present application is to provide a new positive electrode sodium supplement material for sodium ion batteries to solve the problems of low sodium supplement efficiency and poor compatibility with positive electrode materials of the current positive electrode sodium supplement additives, thereby improving the cycle performance of the sodium ion battery.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] A positive electrode sodium supplement material for sodium ion batteries, the molecular formula of the positive electrode sodium supplement material is Na a Fe 1-x-y- z Al x Ti y Mg z O2, wherein a, x, y and z are molar fractions, 0.8≤a≤1.5, 0.05≤x≤0.3, 0.05≤y≤0.3 and 0.05≤z≤0.3.

[0008] The second object of the present application is to provide a preparation method of the positive electrode sodium supplement material for sodium ion batteries.

[0009] S1, a sodium source compound, an iron source compound, an aluminum source compound, a titanium source compound, and a magnesium source compound are weighed according to the stoichiometric formula and pre-mixed to obtain a pre-mixed powder;

[0010] S2, the pre-mixed powder, a solvent, and a dispersant are added to a nano sand mill for ball milling to obtain a slurry;

[0011] S3, the slurry is dried to obtain a precursor; then the precursor is sintered and cooled to obtain a positive electrode sodium supplement material for sodium ion batteries of Na a Fe 1-x-y-z Al x Ti y Mg z O2.

[0012] Preferably, the sodium source compound includes one or more of sodium carbonate, sodium hydroxide, sodium oxalate, and sodium nitrate; the iron source compound includes one or more of iron carbonate, iron oxide, iron nitrate, and ferrous oxalate; the aluminum source compound includes one or more of aluminum nitrate, aluminum hydroxide, and aluminum oxide; the magnesium source compound includes one or more of magnesium carbonate, magnesium oxide, magnesium nitrate, and magnesium oxalate; the titanium source compound is nano titanium dioxide; and the primary particle size of the nano titanium dioxide is 200-500 nm.

[0013] Preferably, in step S2, the mass ratio of the pre-mixed powder to the solvent is 1:(1-4); the mass of the dispersant is 0.1-2% of the mass of the solvent; and the ball milling time is 8-15 h.

[0014] Preferably, the dispersant is any one of ammonium polyacrylate, polyvinylpyrrolidone, and polyethylene glycol; and the solvent is deionized water.

[0015] Preferably, in step S3, the drying temperature is 100-120℃, and the drying time is 10-15 h.

[0016] Preferably, in step S3, the sintering temperature is 500-900℃, and the sintering time is 10-20 h.

[0017] The third object of the present application is to provide a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent, a binder, and the positive electrode sodium supplement material described above.

[0018] Preferably, the weight of the positive electrode sodium supplement material is 1-10% of the weight of the positive electrode active material.

[0019] Preferably, the positive electrode active material is one or more of a layered oxide positive electrode material, a Prussian blue type positive electrode material, and a polyanion phosphate positive electrode material.

[0020] A fourth object of the present application is to provide a sodium ion battery comprising a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is any one of the positive electrode sheets described above.

[0021] Compared with the prior art, the sodium ion battery positive electrode sodium supplement material provided by the present application has the following beneficial effects: the sodium ion battery positive electrode sodium supplement material provided by the present application contains iron, aluminum, titanium, and magnesium, and the above-mentioned substances are mixed and prepared through multiple tests, so that a new sodium supplement compound with good compatibility with the positive electrode active material is obtained, which can effectively reduce the battery capacity loss in the first charge and discharge process in the positive electrode sheet, thereby effectively improving the energy density and cycle performance of the sodium ion single battery. In addition, the positive electrode sodium supplement material of the present application also has the characteristics of low cost and high efficiency, and the preparation process is simple, which can be mass-produced without changing the existing battery slurry preparation and coating process, thereby effectively reducing the manufacturing cost of the battery. DETAILED DESCRIPTION

[0022] 1. A positive electrode sodium supplement material for a sodium ion battery

[0023] A first aspect of the present application is to provide a positive electrode sodium supplement material for a sodium ion battery, wherein the molecular formula of the positive electrode sodium supplement material is Na a Fe 1-x-y-z Al x Ti y Mg z O2, wherein a, x, y, and z are molar fractions, 0.8≤a≤1.5, 0.05≤x≤0.3, 0.05≤y≤0.3, and 0.05≤z≤0.3.

[0024] The positive electrode sodium supplement material provided by the application can effectively reduce the battery capacity loss in the first charge and discharge process, does not participate in the subsequent cycle of the battery, has no negative effect on the subsequent cycle, and can effectively improve the energy density and cycle performance of the sodium ion single battery. Through the inventor's repeated test verification, it is found that when the positive electrode sodium supplement material only contains Fe, Al, Ti and Mg elements and does not contain other transition metal elements, the new positive electrode sodium supplement material has a better overall improvement effect on the sodium ion battery, can avoid the negative effect of too many transition metal elements on the long-term cycle of the battery, and can also avoid the situation that the first charge and discharge efficiency of the battery cannot be effectively improved when only Fe, Al, Ti and Mg elements are contained, and the synergistic effect of the four elements Fe, Al, Ti and Mg is better.

[0025] Preferably, the positive electrode sodium supplement material can be Na 1.1 Fe 0.7 Al 0.1 Ti 0.1 Mg 0.1 O2、Na 1.3 Fe 0.7 Al 0.05 Ti 0.2 Mg 0.05 O2、Na 1.5 Fe 0.5 Al 0.1 Ti 0.3 Mg 0.1 O2、Na 0.8 Fe 0.6 Al 0.05 Ti 0.05 Mg 0.3 O2。

[0026] Specifically, when the contents of Na, Fe, Al, Ti and Mg are different, the first charge and discharge efficiency of the battery will also be affected to a certain extent, and the first charge and discharge efficiency can be optimized to a greater extent when the molar ratio is controlled within a certain amount. In particular, the content of Al, Ti and Mg can be set to a suitable content to improve the first charge and discharge efficiency of the sodium ion battery to more than 88%, and the first charge and discharge efficiency can be improved by at least 12% compared with the sodium ion battery without the sodium supplement material. This is because the suitable range has better compatibility with the positive electrode material, and can better provide sodium ions for the sodium ion battery. In addition, Al, Ti and Mg can also help the dissolution of some transition metal ions, and can better ensure the stability of the sodium supplement material in the subsequent cycle of the sodium ion battery.

[0027] The second aspect of the application provides a preparation method of the positive electrode sodium supplement material for the sodium ion battery, comprising the following steps:

[0028] S1. Weigh out sodium source compound, iron source compound, aluminum source compound, titanium source compound and magnesium source compound according to stoichiometric formula and premix them to obtain premixed powder;

[0029] S2. The premixed powder, solvent and dispersant are added to a nano-sand mill for ball milling to obtain a slurry;

[0030] S3. The slurry is dried to obtain a precursor; then the precursor is sintered and cooled to obtain Na. a Fe 1-x-y-z Al x Ti y Mg z O2 is used in sodium-ion batteries to supplement sodium in the positive electrode.

[0031] Preferably, the sodium source compound includes one or more of sodium carbonate, sodium hydroxide, sodium oxalate, and sodium nitrate; the iron source compound includes one or more of ferric carbonate, ferric oxide, ferric nitrate, and ferrous oxalate; the aluminum source compound includes one or more of aluminum nitrate, aluminum hydroxide, and aluminum oxide; the magnesium source compound includes one or more of magnesium carbonate, magnesium oxide, magnesium nitrate, and magnesium oxalate; and the titanium source compound is nano-titanium dioxide; the primary particle size of the nano-titanium dioxide is 200–500 nm. More preferably, the primary particle size of the nano-titanium dioxide is 300 nm.

[0032] Preferably, in step S2, the mass ratio of the premixed powder to the solvent is 1:(1-4); the mass of the dispersant is 0.1-2% of the mass of the solvent; and the ball milling time is 8-15 hours. More preferably, the mass ratio of the premixed powder to the solvent is 1:2; the mass of the dispersant is 1% of the mass of the solvent; and the ball milling time is 10 hours.

[0033] Preferably, the dispersant is any one of ammonium polyacrylate, polyvinylpyrrolidone, and polyethylene glycol; and the solvent is deionized water.

[0034] Preferably, in step S3, the drying temperature is 100-120°C and the drying time is 10-15 hours.

[0035] Preferably, in step S3, the sintering temperature is 500–900°C, and the sintering time is 10–20 h. More preferably, the sintering temperature is 600–800°C, specifically 600°C, 650°C, 700°C, 750°C, or 800°C; and the sintering time can be 10–12 h, 12–15 h, 15–18 h, or 18–20 h.

[0036] Preferably, in step S3, the sintering atmosphere is an air atmosphere.

[0037] 2. A positive electrode sheet

[0038] The third aspect of the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent, a binder and the positive electrode sodium supplementing material as described above.

[0039] Preferably, the weight of the positive electrode sodium supplementing material is 1-10% of the weight of the positive electrode active material. Specifically, the weight of the positive electrode sodium supplementing material is 1-2%, 2-3%, 3-4%, 4-5%, 5-6%, 6-7%, 7-8%, 8-9%, 9-10% of the weight of the positive electrode active material. More preferably, the weight of the positive electrode sodium supplementing material is 2-7% of the weight of the positive electrode active material.

[0040] Preferably, the positive electrode active material is one or more of a layered oxide positive electrode material, a Prussian blue type positive electrode material, and a polyanion phosphate positive electrode material. More preferably, the positive electrode active material is a layered oxide positive electrode material, which has better compatibility with the positive electrode sodium supplementing material.

[0041] Preferably, the conductive agent can be one or more of acetylene black, Ketjen black and Super P.

[0042] Preferably, the binder can be PVDF and / or PTFE.

[0043] 3. A sodium ion battery

[0044] The fourth aspect of the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is any one of the positive electrode sheets as described above.

[0045] In order to make the technical solutions and advantages of the present application clearer, the following will combine specific embodiments to further describe the present application and its beneficial effects in detail, but the embodiments of the present application are not limited thereto.

[0046] Example 1

[0047] A positive electrode sodium supplementing material for a sodium ion battery, wherein the molecular formula of the positive electrode sodium supplementing material is Na 1.1 Fe 0.7 Al 0.1 Ti 0.1 Mg 0.1 O2.

[0048] The preparation method of the positive electrode sodium supplementing material for a sodium ion battery, comprising the following steps:

[0049] S1, sodium carbonate, ferric nitrate, aluminum nitrate, 300 nm titanium dioxide and magnesium carbonate were weighed according to the stoichiometric formula, ground and premixed to obtain a premixed powder; wherein the molar ratio of Na:Fe:Al:Ti:Mg is 1.1:0.7:0.1:0.1:0.1;

[0050] S2, the premixed powder and deionized water were added to a nano sand mill at a mass ratio of 1:2 and polyacrylamide (1% of the mass of deionized water) and high-energy ball milled for 10h to obtain a slurry;

[0051] S3, the slurry was placed in a blast oven and dried at 120℃ for 12h to obtain a precursor; then the precursor was sintered in an air atmosphere, the sintering temperature was 800℃, the sintering time was 10h, and the natural cooling to room temperature obtained Na 1.1 Fe 0.7 Al 0.1 Ti 0.1 Mg 0.1 O2 sodium ion battery positive electrode sodium supplement material.

[0052] The above positive electrode sodium supplement material is applied to the positive electrode sheet and sodium ion battery, and the preparation process is:

[0053] Positive electrode sheet: the positive electrode sodium supplement material, layered oxide positive electrode material, Super P and PVDF are uniformly mixed and coated on an aluminum foil current collector to obtain a positive electrode sheet; wherein the mass of the positive electrode sodium supplement material is 5% of the mass of the layered oxide positive electrode material.

[0054] Sodium ion battery: hard carbon negative electrode sheet, electrolyte and prepared positive electrode sheet are assembled into a single sodium ion battery, and the formation condition is: charging current is 0.05C, charging cut-off voltage is 4.3V, discharging current is 0.1C, and discharging cut-off voltage is 1.5V.

[0055] Example 2

[0056] The difference between this embodiment and example 1 is the positive electrode sodium supplement material used. The molecular formula of the positive electrode sodium supplement material of this embodiment is Na 1.3 Fe 0.7 Al 0.05 Ti 0.2 Mg 0.05 O2, and the corresponding raw material content is modified.

[0057] The rest is the same as example 1, which will not be repeated here.

[0058] Example 3

[0059] The difference between this embodiment and example 1 is the positive electrode sodium supplement material used. The molecular formula of the positive electrode sodium supplement material of this embodiment is Na 1.5 Fe0.5 Al 0.1 Ti 0.3 Mg 0.1 O2, with the corresponding raw material content being modified accordingly.

[0060] The rest is the same as example 1, which will not be repeated here.

[0061] Example 4

[0062] The difference from example 1 is the sodium supplement material used in the positive electrode. The molecular formula of the sodium supplement material in this example is Na 0.8 Fe 0.6 Al 0.05 Ti 0.05 Mg 0.3 O2, with the corresponding raw material content being modified accordingly.

[0063] The rest is the same as example 1, which will not be repeated here.

[0064] Example 5

[0065] The difference from example 1 is the content of the sodium supplement material in the positive electrode sheet, which is 2%.

[0066] The rest is the same as example 1, which will not be repeated here.

[0067] Example 6

[0068] The difference from example 1 is the content of the sodium supplement material in the positive electrode sheet, which is 10%.

[0069] The rest is the same as example 1, which will not be repeated here.

[0070] Example 7

[0071] The difference from example 1 is the content of the sodium supplement material in the positive electrode sheet, which is 7%.

[0072] The rest is the same as example 1, which will not be repeated here.

[0073] Example 8

[0074] A sodium supplement material for a sodium ion battery, the molecular formula of the sodium supplement material is Na 1.3 Fe 0.7 Al 0.05 Ti 0.2 Mg 0.05 O2.

[0075] The preparation method of the sodium supplement material for the sodium ion battery, comprising the following steps:

[0076] S1, sodium carbonate, ferric nitrate, aluminum nitrate, 200 nm titanium dioxide and magnesium carbonate were weighed according to the stoichiometric formula, ground and premixed to obtain a premixed powder; wherein the molar ratio of Na:Fe:Al:Ti:Mg is 1.3:0.7:0.05:0.2:0.05;

[0077] S2, the premixed powder and deionized water were added to a nano sand mill at a mass ratio of 1:1 and ammonium polyacrylate (ammonium polyacrylate was 2% of the mass of deionized water), and high-energy ball milling was carried out for 15h to obtain a slurry;

[0078] S3, the slurry was placed in a blast oven and dried at 100℃ for 15h to obtain a precursor; then the precursor was sintered in an air atmosphere, the sintering temperature was 500℃, the sintering time was 20h, and the natural cooling to room temperature obtained Na 1.3 Fe 0.7 Al 0.05 Ti 0.2 Mg 0.05 O2 positive electrode sodium supplement material for sodium ion battery.

[0079] The above positive electrode sodium supplement material is applied to the positive electrode sheet and sodium ion battery, and the preparation process is as follows:

[0080] Positive electrode sheet: the positive electrode sodium supplement material, prussian blue positive electrode material, ketjen black and PVDF are uniformly mixed and coated on an aluminum foil current collector to obtain a positive electrode sheet; wherein the mass of the positive electrode sodium supplement material is 1% of the mass of the prussian blue positive electrode material.

[0081] Sodium ion battery: hard carbon negative electrode sheet, electrolyte and prepared positive electrode sheet are assembled into a single sodium ion battery, and the formation condition is: charging current is 0.1C, charging cut-off voltage is 4.2V, discharging current is 0.1C, and discharging cut-off voltage is 1.5V.

[0082] Example 9

[0083] The difference between example 8 and example 9 is that the content of the positive electrode sodium supplement material in the positive electrode sheet is 5%.

[0084] The rest is the same as example 8, which will not be repeated here.

[0085] Example 10

[0086] The difference between example 8 and example 10 is that the content of the positive electrode sodium supplement material in the positive electrode sheet is 7%.

[0087] The rest is the same as example 8, which will not be repeated here.

[0088] Example 11

[0089] The difference between example 9 and example 11 is that the positive electrode active material used in the positive electrode sheet is a layered oxide positive electrode material.

[0090] The rest is the same as example 9, which will not be repeated here.

[0091] Example 12

[0092] The difference from example 8 is the sodium supplement material for the positive electrode. The molecular formula of the sodium supplement material for the positive electrode of this embodiment is Na 1.5 Fe 0.5 Al 0.1 Ti 0.3 Mg 0.1 O2, and the corresponding raw material content is modified accordingly.

[0093] The rest is the same as example 8, which will not be repeated here.

[0094] Example 13

[0095] The difference from example 8 is the sodium supplement material for the positive electrode. The molecular formula of the sodium supplement material for the positive electrode of this embodiment is Na 0.8 Fe 0.6 Al 0.05 Ti 0.05 Mg 0.3 O2, and the corresponding raw material content is modified accordingly.

[0096] The rest is the same as example 8, which will not be repeated here.

[0097] Example 14

[0098] A sodium supplement material for the positive electrode of a sodium ion battery, the molecular formula of the sodium supplement material for the positive electrode is Na 1.5 Fe 0.5 Al 0.1 Ti 0.3 Mg 0.1 O2.

[0099] The preparation method of the sodium supplement material for the positive electrode of the sodium ion battery, comprising the following steps:

[0100] S1, according to the stoichiometric formula, sodium carbonate, ferric nitrate, aluminum nitrate, 500nm titanium dioxide and magnesium carbonate are weighed and ground for pre-mixing to obtain a pre-mixed powder; wherein the molar ratio of Na: Fe: Al: Ti: Mg is 1.5: 0.5: 0.1: 0.3: 0.1;

[0101] S2, the pre-mixed powder and deionized water are added to a nano sand mill according to the mass ratio of 1:4 and polyacrylamide (0.1% of the mass of deionized water), and high-energy ball milling is carried out for 8h to obtain a slurry;

[0102] S3, drying the slurry in a blast oven at 110°C for 15h to obtain a precursor; then sintering the precursor under air atmosphere, sintering temperature is 900°C, sintering time is 10h, and naturally cooling to room temperature to obtain Na 1.5 Fe 0.5 Al 0.1 Ti 0.3 Mg 0.1 O2.

[0103] The above positive electrode sodium supplement material is applied to a positive electrode sheet and a sodium ion battery, and the preparation process is as follows:

[0104] The positive electrode sheet: the positive electrode sodium supplement material, a layered oxide positive electrode material, acetylene black and PTFE are uniformly mixed and coated on an aluminum foil current collector to obtain a positive electrode sheet; wherein the mass of the positive electrode sodium supplement material is 10% of the mass of the layered oxide positive electrode material.

[0105] The sodium ion battery: a hard carbon negative electrode sheet, an electrolyte and the prepared positive electrode sheet are assembled into a single sodium ion battery, and the formation conditions are as follows: the charging current is 0.2C, the charging cut-off voltage is 4.1V, the discharging current is 0.1C, and the discharging cut-off voltage is 1.5V.

[0106] Example 15

[0107] The difference between this embodiment and example 14 is the positive electrode sodium supplement material used. The molecular formula of the positive electrode sodium supplement material of this embodiment is Na 1.3 Fe 0.7 Al 0.05 Ti 0.2 Mg 0.05 O2, and the corresponding raw material content is adaptively modified.

[0108] The rest is the same as example 14, which will not be repeated here.

[0109] Example 16

[0110] The difference between this embodiment and example 14 is the content of the positive electrode sodium supplement material in the positive electrode sheet, which is 5%.

[0111] The rest is the same as example 14, which will not be repeated here.

[0112] Example 17

[0113] A positive electrode sodium supplement material for a sodium ion battery, the molecular formula of the positive electrode sodium supplement material is Na 0.8 Fe 0.6 Al 0.05 Ti 0.05 Mg 0.3 O2.

[0114] The preparation method of the sodium ion battery positive electrode sodium supplement material comprises the following steps:

[0115] S1, sodium carbonate, ferric nitrate, aluminum nitrate, 500nm titanium dioxide and magnesium carbonate are weighed according to the stoichiometric formula, ground and premixed to obtain a premixed powder; wherein the molar ratio of Na:Fe:Al:Ti:Mg is 0.8:0.6:0.05:0.05:0.3;

[0116] S2, the premixed powder and deionized water are added to a nano sand mill for high-energy ball milling at a mass ratio of 1:2 and polyacrylamide (1% of the mass of deionized water), and a slurry is obtained;

[0117] S3, the slurry is placed in a blast oven and dried at 120℃ for 13h to obtain a precursor; then the precursor is sintered in an air atmosphere, the sintering temperature is 700℃, the sintering time is 10h, and the natural cooling to room temperature obtains a Na 0.8 Fe 0.6 Al 0.05 Ti 0.05 Mg 0.3 O2 sodium ion battery positive electrode sodium supplement material.

[0118] The above positive electrode sodium supplement material is applied to the positive electrode sheet and sodium ion battery, and the preparation process is:

[0119] The positive electrode sheet: the positive electrode sodium supplement material, polyanion phosphate positive electrode material, Super P and PVDF are uniformly mixed and coated on the aluminum foil current collector to obtain the positive electrode sheet; wherein the mass of the positive electrode sodium supplement material is 2% of the mass of the polyanion phosphate positive electrode material.

[0120] Sodium ion battery: hard carbon negative electrode sheet, electrolyte and prepared positive electrode sheet are assembled into a single sodium ion battery, and the formation condition is: charging current is 0.05C, charging cut-off voltage is 4.2V, discharging current is 0.1C, and discharging cut-off voltage is 1.5V.

[0121] Example 18

[0122] The difference between this embodiment and example 17 is the positive electrode sodium supplement material used. The molecular formula of the positive electrode sodium supplement material of this embodiment is Na 1.1 Fe 0.7 Al 0.1 Ti 0.1 Mg 0.1 O2, and the corresponding raw material content is modified.

[0123] The rest is the same as example 17, which will not be repeated here.

[0124] Comparative example 1

[0125] Different from example 1, the positive electrode sheet of the present comparative example does not add positive electrode sodium supplement material.

[0126] The rest is the same as example 1, which will not be repeated here.

[0127] Comparative example 2

[0128] Different from example 1, the positive electrode sodium supplement material used is different. The molecular formula of the positive electrode sodium supplement material of the present comparative example is Na 1.1 Fe 0.8 Ti 0.1 Mg 0.1 O2, and the corresponding raw material content is modified adaptively.

[0129] The rest is the same as example 1, which will not be repeated here.

[0130] Comparative example 3

[0131] Different from example 1, the positive electrode sodium supplement material used is different. The molecular formula of the positive electrode sodium supplement material of the present comparative example is Na 1.1 Fe 0.8 Al 0.1 Mg 0.1 O2, and the corresponding raw material content is modified adaptively.

[0132] The rest is the same as example 1, which will not be repeated here.

[0133] Comparative example 4

[0134] Different from example 1, the positive electrode sodium supplement material used is different. The molecular formula of the positive electrode sodium supplement material of the present comparative example is Na 1.1 Fe 0.8 Al 0.1 Ti 0.1 O2, and the corresponding raw material content is modified adaptively.

[0135] The rest is the same as example 1, which will not be repeated here.

[0136] Comparative example 5

[0137] Different from example 1, the positive electrode sodium supplement material used is different. The molecular formula of the positive electrode sodium supplement material of the present comparative example is Na 1.1 Fe 0.7 Cu 0.1 Ti 0.1 Mg 0.1 O2, and the corresponding raw material content is modified adaptively.

[0138] The rest is the same as example 1, which will not be repeated here.

[0139] Comparative example 6

[0140] The positive electrode sodium supplement material used is different from that of Example 1. The molecular formula of the positive electrode sodium supplement material of this comparative example is Na 1.1 Fe 0.7 Al 0.1 Mn 0.1 Mg 0.1 O2, and the corresponding raw material content is modified adaptively.

[0141] The rest is the same as Example 1, which will not be repeated here.

[0142] Comparative Example 7

[0143] The positive electrode sodium supplement material used is different from that of Example 1. The molecular formula of the positive electrode sodium supplement material of this comparative example is NaFe 0.7 Al 0.1 Ti 0.1 Mg 0.1 Mn 0.1 O2, and the corresponding raw material content is modified adaptively.

[0144] The rest is the same as Example 1, which will not be repeated here.

[0145] Comparative Example 8

[0146] The positive electrode sodium supplement material used is different from that of Example 1. The molecular formula of the positive electrode sodium supplement material of this comparative example is NaFe 0.7 Cu 0.1 Ti 0.1 Mg 0.1 Mn 0.1 O2, and the corresponding raw material content is modified adaptively.

[0147] The rest is the same as Example 1, which will not be repeated here.

[0148] Comparative Example 9

[0149] The positive electrode sodium supplement material used is different from that of Example 8. The molecular formula of the positive electrode sodium supplement material of this comparative example is Na 1.1 Fe 0.8 Ti 0.1 Mg 0.1 O2, and the corresponding raw material content is modified adaptively.

[0150] The rest is the same as Example 8, which will not be repeated here.

[0151] Comparative Example 10

[0152] The positive electrode sodium supplement material used is different from that of Example 8. The molecular formula of the positive electrode sodium supplement material of this comparative example is Na 1.1 Fe 0.8 Al 0.1 Mg 0.1O2, with the corresponding raw material content being modified adaptively.

[0153] The rest is the same as in Example 8, which will not be repeated here.

[0154] The sodium-ion batteries obtained in Examples 1-18 and Comparative Examples 1-10 above were subjected to first charge-discharge efficiency tests, and the test results are shown in Table 1.

[0155] Table 1

[0156]

[0157]

[0158] As can be seen from the test results above, when no positive electrode sodium supplement material is added, such as Comparative Example 1, the sodium-ion battery exhibits the worst first charge-discharge efficiency, only 75.3%; while when the positive electrode sodium supplement material is added in Examples 1-18, the first charge-discharge efficiency of the sodium-ion battery is effectively improved, which can reach 88.2% in Example 1, and 88.6% in Example 16.

[0159] In addition, as can be seen from the test results of Example 1 and Comparative Examples 2-8, Example 8 and Comparative Examples 9-10, the composition and structure of the positive electrode sodium supplement material also significantly affect the first charge-discharge efficiency. When the positive electrode sodium supplement material does not contain or only contains Al, Ti, Mg and other elements, the first charge-discharge efficiency of the sodium-ion battery is not better than that of Example 1 or Example 8; and even if it contains Al, Ti, Mg and other elements, such as the selected sodium supplement material also contains other transition metal elements, such as Mn or Cu, although the first charge-discharge efficiency is improved, it is still worse than the positive electrode sodium supplement material protected by the present application. This is mainly because the positive electrode sodium supplement material disclosed in the present application has a stronger synergistic effect of Al, Ti, Mg and other elements in the sodium ion release process, thereby effectively improving the first charge-discharge efficiency.

[0160] In addition, as can be seen from the comparison of Examples 1-18, the corresponding preparation method of different positive electrode sodium supplement materials will also affect the first charge-discharge performance of the final sodium-ion battery. When the contents of Na, Fe, Al, Ti, Mg and other elements are different, the effects of several positive electrode sodium supplement materials obtained under the same preparation conditions will also be different, such as the comparison of Examples 1-4, Na 1.1 Fe 0.7 Al 0.1 Ti 0.1 Mg 0.1 O2is obviously more suitable for the preparation conditions in Example 1; while as the comparison of Example 8 and Examples 12-13, Na 1.3 Fe 0.7 Al 0.05 Ti0.2 Mg 0.05 O2will be more suitable for the preparation conditions in Example 8. This should also be due to the influence between Fe, Al, Ti, Mg elements, but in general, the positive electrode sodium supplement material protected by the application can effectively improve the first charge and discharge performance of the sodium ion battery.

[0161] Based on the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application shall fall within the protection scope of the present application. In addition, although some specific terms are used in the present description, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A positive electrode sodium supplement material for a sodium-ion battery, characterized in that, The positive electrode sodium supplementing material has a molecular formula of Na a Fe 1-x-y- z Al x Ti y Mg z O2, wherein a, x, y, z are molar fractions, 0.8≤a≤1.5, 0.05≤x≤0.3, 0.05≤y≤0.3, 0.05≤z≤0.

3.

2. A method for preparing the positive sodium supplement material for sodium-ion batteries according to claim 1, characterized in that, The method comprises the following steps: S1. Pre-mixing sodium source compound, iron source compound, aluminum source compound, titanium source compound and magnesium source compound according to stoichiometric formula to obtain pre-mixed powder; S2. Adding the pre-mixed powder, solvent and dispersant into a nano sand mill for ball milling to obtain slurry; S3, drying the slurry to obtain a precursor; then sintering, cooling the precursor to obtain Na a Fe 1-x-y-z Al x Ti y Mg z O2 positive electrode sodium supplement material for sodium-ion battery.

3. The method for preparing the sodium-replenishing material for the positive electrode of a sodium-ion battery according to claim 2, characterized in that, The sodium source compound comprises one or more of sodium carbonate, sodium hydroxide, sodium oxalate and sodium nitrate; the iron source compound comprises one or more of iron carbonate, iron oxide, iron nitrate and ferrous oxalate; the aluminum source compound comprises one or more of aluminum nitrate, aluminum hydroxide and aluminum oxide; the magnesium source compound comprises one or more of magnesium carbonate, magnesium oxide, magnesium nitrate and magnesium oxalate; the titanium source compound is nano titanium dioxide; the primary particle size of the nano titanium dioxide is 200-500 nm.

4. The method for preparing the sodium-replenishing material for the positive electrode of a sodium-ion battery according to claim 2, characterized in that, In step S2, the mass ratio of the pre-mixed powder to the solvent is 1:(1-4); the mass of the dispersant is 0.1-2% of the mass of the solvent; the ball milling time is 8-15 h.

5. The method for preparing the sodium-replenishing material for the positive electrode of a sodium-ion battery according to claim 4, characterized in that, The dispersant is any one of polyacrylammonium, polyvinylpyrrolidone and polyethylene glycol; the solvent is deionized water.

6. The method for preparing the sodium-replenishing material for the positive electrode of a sodium-ion battery according to claim 2, characterized in that, In step S3, the drying temperature is 100-120℃, and the drying time is 10-15 h.

7. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, characterized by The positive electrode active material layer comprises positive electrode active material, conductive agent, binder and the positive electrode sodium supplement material of claim 1.

8. The positive electrode sheet according to claim 7, characterized by The weight of the positive electrode sodium supplement material is 1-10% of the weight of the positive electrode active material.

9. The positive electrode sheet according to claim 7, characterized by The positive electrode active material is one or more of layered oxide positive electrode material, Prussian blue type positive electrode material and polyanion phosphate positive electrode material.

10. A sodium-ion battery comprising a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet, characterized by, The positive electrode sheet is the positive electrode sheet of any one of claims 7-9.

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