Sodium-ion batteries and their anodes, anode materials, modified carbon-based anode active materials, preparation and use

Abstract

The application belongs to the field of sodium secondary batteries, and particularly relates to a sodium ion battery and a negative electrode, a negative electrode material, a modified carbon-based negative electrode active material, a preparation method and application thereof. The preparation method of the modified carbon-based negative electrode active material is as follows: mixing a carbon-based active material to be modified and a modifier in a weight ratio of 1:0.01-0.15, preforming first-stage calcination at a temperature T1, and then performing second-stage calcination treatment at a temperature T2 to obtain the modified carbon-based negative electrode active material. The modifier comprises at least one of Na2ZrF6 and Na2TiF6. The temperature T1 is 100-400 DEG C, and the temperature T2 is 550-1100 DEG C. The method can realize synergy, can optimize the physicochemical structure of the negative electrode material based on the physicochemical transformation of the modifier and the carbon-based active material at the temperature, and can strengthen the electrochemical performance of the sodium ion battery, for example, improve the first coulomb efficiency, high-temperature and long-cycle stability thereof.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sodium ion batteries, in particular to the field of negative electrode materials of sodium ion batteries. BACKGROUND

[0002] Sodium ion batteries have great potential in large-scale energy storage and short-distance electric vehicles due to abundant resources and low cost. Carbon-based negative electrode materials of sodium ion batteries mainly include graphite carbon materials, hard carbon materials, soft carbon materials, nano-carbon (carbon nanotubes, graphene), amorphous carbon, etc. However, the energy density of existing conventional carbon-based materials is significantly lower than that of lithium batteries, and one of the core reasons is that the negative electrode has low initial efficiency, and a large amount of sodium ions are consumed to form SEI during the first charge and discharge, causing irreversible loss and reducing the actual available capacity.

[0003] In view of the problems faced by carbon-based materials of sodium ion batteries, existing technologies also provide some improvement schemes such as doping and coating. For example, the patent document with publication number CN120581580A discloses a negative electrode active material, a preparation method thereof, a negative electrode for sodium ion batteries, a sodium ion battery and an electric device; the negative electrode active material comprises: a nitrogen-doped carbon sphere matrix and manganese monoxide embedded inside the nitrogen-doped carbon sphere matrix; the average particle size of the manganese monoxide is 1.5 nm to 2.5 nm.

[0004] The patent document with publication number CN120622465A discloses a composite biomass hard carbon material, a preparation method and application thereof; the preparation method comprises the following steps: (1) mixing and reacting biomass and a composite acid solution to obtain esterified modified biomass; (2) placing the esterified modified biomass in a mixed gas atmosphere for gas phase modification treatment to obtain a gas phase modification product; (3) mixing the gas phase modification product with nano-silicon, and performing pre-carbonization under a protective gas atmosphere to obtain a composite pre-carbonization product; (4) performing two-stage gradient sintering on the composite pre-carbonization product under a protective gas atmosphere, then cooling, and performing heat preservation reaction under a fluorine-based gas substance atmosphere to obtain the composite biomass hard carbon material; the fluorine-based gas substance includes fluorine gas or carbon tetrafluoride.

[0005] Further, the patent document with publication number CN120553686A discloses a multi-coal-species composite sodium battery hard carbon negative electrode material, a preparation method and application thereof, which is based on three different characteristic coal raw materials, and utilizes their respective component characteristics, pyrolysis characteristics and structural characteristics to prepare a hard carbon material with excellent structure and good performance.

[0006] In summary, the existing improvement schemes of carbon-based materials mainly involve doping, which can improve the capacity, but the high-temperature and long-cycle stability of the existing schemes needs to be further improved. SUMMARY

[0007] In view of the problems in the prior art, the first object of the present application is to provide a preparation method of a modified carbon-based negative electrode active material, aiming to prepare a negative electrode active material that meets the application requirements of sodium-ion batteries and has excellent electrochemical performance.

[0008] The second object of the present application is to provide the modified carbon-based negative electrode active material prepared by the preparation method and the application thereof in sodium-ion batteries.

[0009] The third object of the present application is to provide a sodium-ion battery comprising the modified carbon-based negative electrode active material, a negative electrode thereof and a negative electrode material.

[0010] The active ion of a sodium-ion battery is sodium ion, which has a larger radius than the active lithium ion of a lithium-ion battery. It is generally difficult for the negative electrode material of a lithium-ion battery to continue to meet the requirements of sodium ion intercalation and deintercalation, and it is difficult to obtain the expected electrochemical performance of the sodium-ion battery under special conditions such as high temperature and long cycle. In view of the problems faced by the carbon-based negative electrode material of the sodium-ion battery, the present application proposes the following improvement scheme:

[0011] A preparation method of a modified carbon-based negative electrode active material, wherein a carbon-based active material to be modified and a modifier in a weight ratio of 1:0.01-0.15 are mixed, then subjected to first-stage calcination at a temperature T1, and then subjected to second-stage calcination at a temperature T2 to obtain a modified carbon-based negative electrode active material.

[0012] The modifier comprises at least one of Na2ZrF6 and Na2TiF6.

[0013] The temperature T1 is 100-400 DEG C, and the temperature T2 is 550-1100 DEG C.

[0014] The present application innovatively uses Na2ZrF6 and Na2TiF6 as a modifier, and combines them with the carbon-based active material for two-stage gradient thermal modification treatment, and further cooperates with the joint control of the amount and temperature of the modifier for thermal modification, so as to realize synergy, optimize the physicochemical structure of the negative electrode material based on the physicochemical transformation of the modifier and the carbon-based active material at the temperature, and strengthen the electrochemical performance of the sodium-ion battery, for example, improve the high-temperature and long-cycle stability thereof.

[0015] In the present application, the carbon-based active material can be any publicly known carbon-based material suitable for sodium-ion batteries in the industry, for example, at least one of hard carbon (also referred to as hard carbon in the present application), graphite, and soft carbon (also referred to as soft carbon in the present application).

[0016] In the present application, the modifier can be single Na2ZrF6 or Na2TiF6, preferably a composite modifier of Na2ZrF6 and Na2TiF6. Studies have shown that the use of the composite modifier, combined with the amount of the modifier described in the present application and the joint control of the two-stage gradient roasting mechanism, can further optimize the physicochemical structure of the carbon material, making it suitable for the application requirements of sodium-ion batteries and improving the high-temperature and long-cycle stability of sodium-ion batteries.

[0017] The modifier also contains Na3AlF6, wherein the content of Na3AlF6 is 5-40 wt.% or less.

[0018] The modifier described in the present application can be modifier A, modifier B, modifier C, modifier D, modifier E and modifier F, wherein modifier A is Na2ZrF6. Modifier B is Na2TiF6. Modifier C is Na2ZrF6 and Na2TiF6. Modifier D is Na2ZrF6 and Na3AlF6. Modifier E is Na2TiF6 and Na3AlF6. Modifier F is Na2ZrF6, Na2TiF6 and Na3AlF6.

[0019] In the present application, when the modifier uses a composite modifier containing two or more components, the content of the components can be reasonably adjusted as needed, for example, the content of the auxiliary component (component with less content) can be controlled at 40 wt.% or less.

[0020] For example, modifier C can be Na2ZrF6 and Na2TiF6 with a weight ratio of 0.5-2:1. Modifier D can be Na2ZrF6 and Na3AlF6 with a weight ratio of 2-4:1 (further 2.5-3.5:1). The weight ratio of modifier E can be Na2TiF6 and Na3AlF6 with a weight ratio of 2-4:1 (further 2.5-3.5:1). The weight ratio of modifier F can be Na2ZrF6, Na2TiF6 and Na3AlF6 with a weight ratio of 1-2:1-2:1.

[0021] In the present application, the use of a composite modifier, especially a ternary composite modifier, can further optimize the modification effect of the carbon material and help further improve the high-temperature and long-cycle stability of sodium-ion batteries.

[0022] In the present application, the weight ratio of the carbon-based active material and the modifier is 1:0.03-0.1; further preferably 1:0.04-0.08, and more preferably 1:0.04-0.06. Under the preferred ratio, the combination of the modifier and the two-stage gradient roasting mechanism can further optimize the physicochemical structure of the carbon material, so that it can meet the application requirements of sodium-ion batteries and improve the high-temperature and long-cycle stability of sodium-ion batteries.

[0023] Preferably, the mixing method of the carbon-based active material and the modifier is dry mixing or wet mixing; wherein the wet mixing is, for example, spray drying.

[0024] The atmosphere of the spray drying is at least one of nitrogen and a noble gas.

[0025] The inlet air temperature of the spray drying is 100-220 DEG C, and the outlet air temperature is 80-200 DEG C.

[0026] Preferably, the atmosphere of the roasting is at least one of nitrogen and a noble gas.

[0027] In the present application, the two-stage roasting process in combination with the modifier can further optimize the physicochemical structure of the carbon material, so that it can meet the application requirements of sodium-ion batteries and improve the high-temperature and long-cycle stability of sodium-ion batteries.

[0028] The temperature T1 can be 100-350 DEG C; further can be 120-300 DEG C.

[0029] The holding time at temperature T1 can be 0.5-3 h, further can be 1-2 h.

[0030] The temperature T2 can be 600-850 DEG C; further can be 650-750 DEG C. Under the preferred roasting conditions, it is helpful to further improve the modification effect and to further improve the high-temperature and long-cycle stability of sodium-ion batteries.

[0031] The holding time at temperature T2 can be 2-10 h, further can be 3-9 h; and more preferably 4-8 h.

[0032] The present application also provides a modified carbon-based negative active material prepared by the preparation method.

[0033] The preparation method of the present application can endow the prepared material with special physicochemical characteristics, and the material prepared by the preparation method can unexpectedly meet the application requirements of sodium-ion batteries and can obtain excellent performance of sodium-ion batteries.

[0034] The application further provides application of the modified carbon-based negative electrode active material prepared by the preparation method, as a negative electrode active material, to preparation of a sodium ion battery.

[0035] The application further provides a negative electrode material of a sodium ion battery, comprising a negative electrode active material, a binder and a conductive agent, wherein the negative electrode active material comprises the modified carbon-based negative electrode active material prepared by the preparation method.

[0036] The negative electrode material provided by the application can comprise other components and contents known in the art or can be reasonably controlled based on known principles, in addition to the modified carbon-based negative electrode active material provided by the application.

[0037] The application further provides a negative electrode of a sodium ion battery, comprising a current collector and a negative electrode material compounded on the surface of the current collector, wherein the negative electrode material is the negative electrode material provided by the application.

[0038] The application further provides a sodium ion battery comprising the negative electrode provided by the application.

[0039] Advantages

[0040] The application innovatively uses Na3AlF6 or Na2TiF6 as a modifier, and performs two-stage gradient heat modification treatment on the modifier and a carbon-based active material, and further cooperates with the joint control of the amount of the modifier and the temperature of the two-stage gradient heat treatment, so that the synergistic effect can be achieved, the physicochemical structure of the negative electrode material can be optimized based on the physicochemical transformation of the modifier and the carbon-based active material at the temperature, and the electrochemical performance of the sodium ion battery can be strengthened.

[0041] In the application, the combination of the modifier and the two-stage gradient calcination process can further improve the fast charging and high-temperature cycle stability of the prepared sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 SEM images of the modified hard carbon finally prepared in Example 1 and the hard carbon of Comparative Example 1;

[0043] Figure 2 A comparison chart of the first coulombic efficiency of Example 1 and Comparative Example 1;

[0044] Figure 3 Cycle charts of 300 mAh g-1 of Example 1 and Comparative Example 1; -1 , 30 o C cycles 1500 times;

[0045] Figure 4 Cycle charts of 1 Ah, 30 o C, 1000 cycles of Example 4 and Comparative Example 4;

[0046] Figure 5 For Example 4 and Comparative Example 4, 1 Ah, 60 o C, cycle graph of 1000 cycles. DETAILED DESCRIPTION

[0047] The technical solutions of the present application are further described below in conjunction with examples, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be covered in the protection scope of the present application.

[0048] Test conditions

[0049] In order to test whether the modified negative electrode achieves the above excellent effect, a sodium-ion full battery is prepared, and the battery parameters are as follows:

[0050] Positive electrode: the positive electrode active material used is sodium iron pyrophosphate phosphate (NFPP), and the positive electrode composition is positive electrode active material: conductive carbon black: carbon nanotube: PVDF = 90:3:2:5, and the positive electrode active material loading is ~14.1 mg cm -2 The separator material is polypropylene (PP).

[0051] Negative electrode: negative electrode active material: conductive carbon black: carbon nanotube: PVDF = 93.9:1.9:1.2:3, and the negative electrode active material loading is ~5.8 mg cm -2 .

[0052] The NP ratio of the assembled battery is about 1.2, the positive and negative electrodes of the button cell both use a diameter of 12 mm, and the theoretical capacity of the soft package battery is ~1 Ah (1.5~3.9 V).

[0053] The electrolyte is a mixed solution of NaPF6 and NaDFOB dissolved in ethylene carbonate and dimethyl carbonate (volume ratio of ethylene carbonate to dimethyl carbonate is 1:1), wherein the concentration of NaPF6 is 0.95M, the concentration of NaDFOB is 0.05M, and additionally 3 vol% FEC (based on the volume of the electrolyte) is also added to the electrolyte.

[0054] In the present application, as an optional scheme, the hard carbon before treatment can be prepared based on conventional means, or it is a common commercial product. For example, in the following cases, the hard carbon used is purchased from Hunan Naikexin Material Co., Ltd.

[0055] Example 1

[0056] Step 1:

[0057] The modifier (including 0.6 g Na2ZrF6 and 0.2 g Na3AlF6) was dispersed in 120 mL of ethanol by ultrasonic dispersion, 20 g of hard carbon was added and stirred to form a mixed slurry, and the mixed slurry was spray dried under an argon atmosphere, with an inlet temperature of 160 o C and an outlet temperature of 110 o C to obtain composite particles.

[0058] Step 2:

[0059] The composite particles of step 1 were heat-treated at 120 o C for 2 h, and then heat-treated at 700 o C for 4 h to obtain surface-modified hard carbon. The heat-treatment was performed in an argon atmosphere. The surface-modified hard carbon was prepared into a negative electrode sheet according to the composition of the above-mentioned negative electrode, and then assembled into a coin cell.

[0060] The coin cell was left to stand at 30 o C for 12 h, activated for 1 cycle, and cycled at 30 −1 C for 1500 times at a current density of 300 mAh g −1 . o C.

[0061] Example 2

[0062] Compared with Example 1, the only difference is that the mass and combination of the modifier are different, as follows:

[0063] Example 2A: Na2ZrF6: 0.3 g, Na3AlF6: 0.1 g, Na2TiF6: 0 g;

[0064] Example 2B: Na2ZrF6: 1.2 g, Na3AlF6: 0.4 g, Na2TiF6: 0 g;

[0065] Example 2C: Na2ZrF6: 0 g, Na3AlF6: 0.2 g, Na2TiF6: 0.6 g;

[0066] Example 2D: Na2ZrF6: 0.8 g, Na3AlF6: 0 g, Na2TiF6: 0 g;

[0067] Example 2E: Na2ZrF6: 0 g, Na3AlF6: 0 g, Na2TiF6: 0.8 g;

[0068] Example 2F: Na2ZrF6: 0.3 g, Na3AlF6: 0.2 g, Na2TiF6: 0.3 g;

[0069] Example 2G: Na2ZrF6: 0.4 g, Na3AlF6: 0 g, Na2TiF6: 0.4 g;

[0070] Other operations and parameters are the same as Example 1.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that the calcination process is optimized, specifically as follows:

[0073] Example 3A: First-stage calcination temperature, time: 300 o C / 2h, second-stage calcination temperature, time: 700 o C / 4h;

[0074] Example 3B: First-stage calcination temperature, time: 120 o C / 2h, second-stage calcination temperature, time: 600 o C / 4h;

[0075] Example 3C: First-stage calcination temperature, time: 120 o C / 2h, second-stage calcination temperature, time: 800 o C / 4h;

[0076] Example 3D: First-stage calcination temperature, time: 120 o C / 2h, second-stage calcination temperature, time: 600 o C / 8h;

[0077] Other operations and parameters are the same as Example 1.

[0078] Example 4

[0079] Compared with Example 1, the only difference is that the battery used for testing is a soft pack battery assembled, the size of the soft pack battery positive electrode is 4.3x6.3 mm, the size of the negative electrode is 4.5x6.5 mm, the standing time of the assembled soft pack battery is 60 h, and the battery is activated for one cycle at 0.1C, and is cycled for 1000 times at different temperatures at a current density of 1 Ah.

[0080] Example 4A: The cycle temperature is 30 o C;

[0081] Example 4B: The cycle temperature is 60 o C.

[0082] Comparative Example 1

[0083] Compared with Example 1, the only difference is that the hard carbon used is not modified.

[0084] Comparative Example 2

[0085] The difference compared with Example 1 is only that the baking schedule is different, and the experimental group is characterized in that:

[0086] Comparative Example 2A: No baking treatment was performed; the composite particles of Step 1 were directly used as the negative active material;

[0087] Comparative Example 2B: No first-stage baking treatment was performed;

[0088] Comparative Example 2C: No second-stage baking treatment was performed;

[0089] The other operations and parameters were the same as in Example 1.

[0090] Comparative Example 3

[0091] The difference compared with Example 1 is only that the modifier used is different, specifically:

[0092] Comparative Example 3A: NaPF6;

[0093] Comparative Example 3B: NaDFOB.

[0094] The amount of modifier used and the other operations and parameters were the same as in Example 1.

[0095] Comparative Example 4

[0096] The difference compared with Example 4 is only that the hard carbon used to assemble the soft-pack battery was not modified. The other operations and parameters were the same as in Example 1.

[0097] Comparative Example 4A: 30 o C;

[0098] Comparative Example 4B: 60 o C.

[0099] Comparative Example 5

[0100] The difference compared with Example 2F is only that the type of modifier was changed, or the amount of modifier used was outside the specified range.

[0101] Comparative Example 5A: Na2ZrF6: 0 g, Na3AlF6: 0.8 g, Na2TiF6: 0 g;

[0102] Comparative Example 5B: The proportions of Na2ZrF6, Na3AlF6, and Na2TiF6 were the same as in Example 2F, and the total amount of the combined modifier was 5 g. The other operations and parameters were the same as in Example 2F.

[0103] The results of each case are shown in Table 1:

[0104]

[0105] The soft-pack battery performance of Example 4 and Comparative Example 4 is shown in Table 2:

[0106]

[0107] As can be seen from Table 1, based on the comparison of Example 1 and each of the comparative examples (Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5), the novel use of Na2ZrF6 and Na2TiF6 as modifiers, combined with two-stage gradient heat modification treatment of carbon-based active materials, further combined with the joint control of the amount, temperature, etc. of the modified modifier, can achieve synergy, can optimize the physicochemical structure of the negative electrode material based on the physicochemical transformation of the modifier and the carbon-based active material at the temperature, and can strengthen the electrochemical performance of the sodium-ion battery, for example, improve the first coulombic efficiency and long cycle stability.

[0108] As can be seen from Example 1 and Example 2, by using the special combination of modifiers and controlling the amount, the first coulombic efficiency and long cycle stability of the obtained negative electrode can be improved.

[0109] As can be seen from Example 1 and Example 3, by using the special two-stage gradient roasting process, the first coulombic efficiency and long cycle stability of the obtained negative electrode can be improved.

[0110] As can be seen from Table 2, by using Example 4 and Comparative Example 4, the modified material obtained by the modification method of the application can obtain excellent high-temperature long cycle stability.

Claims

1. A method for producing a modified carbon-based negative electrode active material, characterized by, The carbon-based active material to be modified and the modifier with a weight ratio of 1:0.01-0.15 are mixed, and then subjected to a first-stage calcination at a temperature T1, followed by a second-stage calcination at a temperature T2, to obtain a modified carbon-based negative electrode active material. The modifier comprises at least one of Na2ZrF6 and Na2TiF6. The temperature T1 is 100-400°C, and the temperature T2 is 550-1100°C.

2. The method for producing a modified carbon-based negative electrode active material according to claim 1, characterized by, The carbon-based active material is at least one of hard carbon, graphite and soft carbon.

3. The method for producing a modified carbon-based negative electrode active material according to claim 1, characterized by, The modifier comprises Na2ZrF6 and Na2TiF6 with a weight ratio of 0.1-10:

1.

4. The method for producing a modified carbon-based negative electrode active material according to any one of claims 1 to 3, characterized by, The modifier further comprises Na3AlF6. The content of Na3AlF6 is 5-40 wt.%.

5. The preparation method of the modified carbon-based negative electrode active material according to claim 1, wherein the mixing of the carbon-based active material and the modifier is dry mixing or wet mixing, and the wet mixing is spray drying. The atmosphere of the spray drying is at least one of nitrogen and a noble gas. The inlet air temperature of the spray drying is 100-220°C, and the outlet air temperature is 80-200°C. The atmosphere of the calcination is at least one of nitrogen and a noble gas. The holding time at the temperature T1 is 0.5-3 h, and the holding time at the temperature T2 is 2-10 h.

6. A modified carbon-based negative electrode active material prepared by the preparation method of any one of claims 1-5. The modified carbon-based negative electrode active material is used as a negative electrode active material to prepare a sodium-ion battery.

7. Use of the modified carbon-based negative electrode active material produced by the production method according to any one of claims 1 to 5, characterized in that, The negative electrode active material comprises the modified carbon-based negative electrode active material prepared by the preparation method of any one of claims 1-5.

8. A negative electrode material of a sodium-ion battery, comprising a negative electrode active material, a binder, and a conductive agent, characterized in that, The negative electrode material is the negative electrode material of claim 8.

9. A negative electrode of a sodium-ion battery comprising a current collector and a negative electrode material complexed on the surface thereof, characterized in that, The battery comprises the negative electrode of claim 9.

10. A sodium-ion battery, characterized in that, ​

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