Sodium-ion battery, negative electrode of sodium-ion battery, negative electrode material, modified carbon-based negative electrode active material, preparation and application

Abstract

The invention belongs to the field of sodium secondary batteries, and particularly relates to a sodium ion battery, a negative electrode of the sodium ion battery, a negative electrode material, a modified carbon-based negative electrode active material, preparation and application, and a preparation method of the modified carbon-based negative electrode active material comprises the following steps: mixing a to-be-modified carbon-based active material and a modifier according to a weight ratio of 1: 0.01-0.15, carrying out first-stage roasting at a temperature T1 in advance, and carrying out second-stage roasting at a temperature T2, and then carrying out second-stage roasting treatment at the temperature T2 to prepare the modified carbon-based negative electrode active material, the modifying agent is prepared from at least one of Na2ZrF6 and Na2TiF6; the temperature T1 is 100 to 400 DEG C; and the temperature T2 is 550 to 1100 DEG C. According to the method disclosed by the invention, synergism can be realized, the physical and chemical structure of the negative electrode material can be optimized based on physical and chemical transformation of the modifier and the carbon-based active material at the temperature, so that the electrochemical performance of the sodium-ion battery is enhanced, for example, the first coulombic efficiency, high temperature and long cycle stability of the sodium-ion battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, specifically relating to the field of negative electrode materials for sodium-ion batteries. Background Technology

[0002] Sodium-ion batteries have great potential in large-scale energy storage and short-range electric vehicles due to their abundant resources and low cost. The carbon-based anode materials for sodium-ion batteries mainly include graphitic carbon materials, hard carbon materials, soft carbon materials, nano-carbon (carbon nanotubes, graphene), and amorphous carbon. However, the energy density of existing conventional carbon-based materials is significantly lower than that of lithium-ion batteries. One of the core reasons is the low initial efficiency of the anode; during the first charge and discharge cycle, a large number of sodium ions are consumed in the formation of the SEI (Sediment Injection), causing irreversible losses and reducing the actual usable capacity.

[0003] To address the challenges faced by carbon-based materials in sodium-ion batteries, existing technologies have provided several improvement solutions, such as doping and coating. For example, patent document CN120581580A discloses a negative electrode active material and its preparation method, a negative electrode for sodium-ion batteries, a sodium-ion battery, and an electrical device thereof; the negative electrode active material comprises: a nitrogen-doped carbon sphere matrix and manganese monoxide embedded within the nitrogen-doped carbon sphere matrix; the average particle size of the manganese monoxide is 1.5 nm to 2.5 nm.

[0004] Patent document CN120622465A discloses a composite biomass hard carbon material and its preparation method and application; the preparation method includes the following steps: (1) mixing biomass with a composite acid solution to obtain esterified biomass; (2) placing the esterified biomass in a mixed gas atmosphere for gas phase modification treatment to obtain a gas phase modified product; (3) mixing the gas phase modified product with nano-silicon and pre-carbonizing it under a protective gas atmosphere to obtain a composite pre-carbonized product; (4) performing two-stage gradient sintering of the composite pre-carbonized product under a protective gas atmosphere, then cooling it down and holding it in a fluorine gas atmosphere to obtain the composite biomass hard carbon material; the fluorine gas includes fluorine or carbon tetrafluoride.

[0005] For example, patent document CN120553686A discloses a multi-coal composite sodium battery hard carbon anode material, preparation method and application. Based on three coal raw materials with different characteristics, the paper utilizes their respective composition characteristics, pyrolysis characteristics and structural characteristics to prepare a hard carbon material with excellent structure and good performance.

[0006] In summary, the main improvement schemes for existing carbon-based materials lie in doping, which can improve their capacity, but the high-temperature and long-cycle stability of existing schemes need to be further improved. Summary of the Invention

[0007] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing modified carbon-based anode active materials, aiming to prepare anode active materials that meet the application requirements of sodium-ion batteries and also possess excellent electrochemical performance.

[0008] The second objective of this invention is to provide a modified carbon-based anode active material prepared by the aforementioned method and its application in sodium-ion batteries.

[0009] A third objective of this invention is to provide a sodium-ion battery comprising the modified carbon-based negative electrode active material, and the same as its negative electrode and negative electrode material.

[0010] The active ion in sodium-ion batteries is the sodium ion, which has a larger radius than the active lithium ion in lithium-ion batteries. Therefore, anode materials adapted for lithium-ion batteries often struggle to meet the requirements of sodium ion insertion and extraction, making it difficult to achieve the expected electrochemical performance, especially under special conditions such as high temperature and long cycling, in sodium-ion batteries. To address the problems faced by carbon-based anode materials for sodium-ion batteries, this invention proposes the following improvement:

[0011] A method for preparing a modified carbon-based anode active material involves mixing the carbon-based active material to be modified and a modifier in a weight ratio of 1:0.01~0.15, then performing a first-stage calcination at temperature T1, followed by a second-stage calcination at temperature T2 to obtain the modified carbon-based anode active material.

[0012] The modifiers include at least one of Na2ZrF6 and Na2TiF6;

[0013] Temperature T1 is 100~400℃; temperature T2 is 550~1100℃.

[0014] This invention innovatively uses Na2ZrF6 and Na2TiF6 as modifiers, and combines them with carbon-based active materials for a two-stage gradient thermal modification treatment. Furthermore, by jointly controlling the amount of modifier and temperature during the thermal modification, a synergistic effect can be achieved. Based on the physicochemical transformation of the modifier and carbon-based active materials at the stated temperature, the physicochemical structure of the negative electrode material can be optimized, thereby enhancing the electrochemical performance of sodium-ion batteries, such as improving their high-temperature and long-cycle stability.

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

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

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

[0018] The modifiers described in this invention 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; and modifier F is Na₂ZrF₆, Na₂TiF₆, and Na₃AlF₆.

[0019] In this invention, when the modifier is a composite modifier containing two or more components, the content of the components can be reasonably adjusted as needed. For example, the content of auxiliary components (components with a smaller content) can be controlled below 40 wt.%.

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

[0021] In this invention, the use of composite modifiers, especially ternary composite modifiers, can further optimize the modification effect of carbon materials and help to further improve the high-temperature and long-cycle stability of sodium-ion batteries.

[0022] In this invention, the weight ratio of carbon-based active material to modifier is 1:0.03~0.1; more preferably 1:0.04~0.08, and even more preferably 1:0.04~0.06. In this invention, under the preferred ratio, combined with the modifier described herein and the joint control of the two-stage gradient calcination mechanism, the physicochemical structure of the carbon material can be further optimized, making it suitable for the application requirements of sodium-ion batteries and improving the high-temperature, long-cycle stability of sodium-ion batteries.

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

[0024] The atmosphere for spray drying is at least one of nitrogen and rare gases.

[0025] The inlet air temperature of the spray dryer is 100~220℃, and the outlet air temperature is 80~200℃.

[0026] Preferably, the roasting atmosphere is at least one of nitrogen and rare gases.

[0027] In this invention, the two-stage calcination process, combined with the modifier, can further optimize the physicochemical structure of carbon materials, making them suitable for the application requirements of sodium-ion batteries and improving the high-temperature and long-cycle stability of sodium-ion batteries.

[0028] The temperature T1 can be 100~350℃; further, it can be 120~300℃.

[0029] The heat preservation time at temperature T1 can be 0.5~3 h, and can be further extended to 1~2 h.

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

[0031] The heat preservation time at temperature T2 can be 2~10 h, further can be 3~9 h; and even further can be 4~8 h.

[0032] The present invention also provides a modified carbon-based anode active material prepared by the preparation method described above.

[0033] The preparation method described in this invention can endow the prepared material with special physicochemical properties, and the material with the properties obtained by the preparation method can unexpectedly adapt to the application requirements of sodium-ion batteries, thus achieving excellent sodium-ion battery performance.

[0034] The present invention also provides an application of the modified carbon-based anode active material prepared by the above preparation method, which is used as an anode active material in the preparation of sodium-ion batteries.

[0035] The present invention also provides a negative electrode material for a sodium-ion battery, comprising a negative electrode active material, a binder, and a conductive agent, wherein the negative electrode active material comprises a modified carbon-based negative electrode active material prepared by the preparation method described above.

[0036] The anode material described in this invention, apart from the modified carbon-based anode active material described in this invention, may have other components and contents that are known or can be reasonably controlled based on known principles.

[0037] The present invention also provides a negative electrode for a sodium-ion battery, comprising a current collector and a negative electrode material composited thereon, wherein the negative electrode material is the negative electrode material described in the present invention.

[0038] The present invention also provides a sodium-ion battery comprising the negative electrode described herein.

[0039] Beneficial effects

[0040] This invention innovatively uses Na3AlF6 or Na2TiF6 as a modifier, and combines it with carbon-based active materials for a two-stage gradient thermal modification treatment. Furthermore, by coordinating the dosage of the modifier and the temperature of the two-stage gradient thermal treatment, a synergistic effect can be achieved. Based on the physicochemical transformation of the modifier and carbon-based active materials at the stated temperature, the physicochemical structure of the negative electrode material can be optimized, thereby enhancing the electrochemical performance of sodium-ion batteries.

[0041] In this invention, the combined modifiers described above, in conjunction with the two-stage gradient calcination process, can further synergistically improve the fast charging and high-temperature cycling stability of the prepared sodium-ion batteries. Attached Figure Description

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

[0043] Figure 2 This is a comparison chart of the initial coulombic efficiency of Example 1 and Comparative Example 1;

[0044] Figure 3 300 mAh g for Example 1 and Comparative Example 1 -1 30 o A loop diagram of a C loop iterating 1500 times;

[0045] Figure 4 Example 4 and Comparative Example 4 were tested at 1 Ah and 30 °C. o C. A loop diagram that repeats 1000 times;

[0046] Figure 5 Example 4 and Comparative Example 4 were tested at 1 Ah and 60 °C. o C. A loop diagram that repeats 1000 times. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0048] Test conditions

[0049] To verify whether the modified negative electrode achieved the aforementioned excellent effects, a sodium-ion full cell was prepared, and the cell parameters are as follows:

[0050] Positive electrode: The positive electrode active material used is sodium iron pyrophosphate (NFPP). The positive electrode composition is: positive electrode active material: conductive carbon black: carbon nanotubes: PVDF = 90:3:2:5, with a positive electrode active material loading of ~14.1 mg / cm³. -2 The diaphragm is made of polypropylene (PP).

[0051] Negative electrode: Negative electrode active material: Conductive carbon black: Carbon nanotubes: PVDF = 93.9:1.9:1.2:3, Negative electrode active material loading ~5.8 mg / cm³ -2 .

[0052] The assembled battery has an NP ratio of approximately 1.2. Both the positive and negative electrodes of the button cell use 12 mm diameter plates. The theoretical capacity of the soft-pack 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 (ethylene carbonate and dimethyl carbonate volume ratio 1:1), wherein the concentration of NaPF6 is 0.95M and the concentration of NaDFOB is 0.05M. In addition, 3 vol% FEC is added to the electrolyte (based on electrolyte volume).

[0054] In this invention, as an optional approach, the hard carbon before treatment can be prepared using conventional methods or be a common commercial product. For example, in the following case, the hard carbon used was purchased from Hunan Nako New Materials Co., Ltd.

[0055] Example 1

[0056] Step 1:

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

[0058] Step 2:

[0059] The composite particles from step 1 were heated at 120°C. o Calcined at a constant temperature of C for 2 hours, followed by calcination at 700°C. o Surface-modified hard carbon was obtained by constant-temperature calcination at C for 4 h in an argon atmosphere. The surface-modified hard carbon was then used to prepare a negative electrode sheet according to the above-mentioned negative electrode composition ratio, and then assembled into a coin cell.

[0060] Button batteries at 30 o C was left to stand for 12 hours, at 60 mAh g −1 Activation cycle 1, at 300 mAh g −1 The current density is at 30 o The C loop iterates 1500 times.

[0061] Example 2

[0062] Compared with Example 1, the only difference is the quality and combination of the modifier, as detailed below:

[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] All other operations and parameters are the same as in Example 1.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that the roasting process has been optimized, as follows:

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

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

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

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

[0077] All other operations and parameters are the same as in Example 1.

[0078] Example 4

[0079] Compared with Example 1, the only difference is that the battery used for testing is an assembled pouch cell. The positive electrode size of the pouch cell is 4.3 × 6.3 mm, the negative electrode size is 4.5 × 6.5 mm, the assembled pouch cell is left to stand for 60 h, activated once at 0.1C, and cycled 1000 times at different temperatures with a current density of 1 Ah.

[0080] Example 4A: Cycling temperature is 30°C o C;

[0081] Example 4B: Cycling temperature is 60°C o C.

[0082] Comparative Example 1

[0083] The only difference from Example 1 is that the hard carbon used was not modified.

[0084] Comparative Example 2

[0085] Compared with Example 1, the only difference is the roasting regime; the experimental group is different in that:

[0086] Comparative Example 2A: No calcination treatment was performed; the composite particles from step 1 were directly used as the negative electrode active material.

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

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

[0089] All other operations and parameters are the same as in Example 1.

[0090] Comparative Example 3

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

[0092] Comparative Example 3A: NaPF6;

[0093] Comparative Example 3B: NaDFOB.

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

[0095] Comparative Example 4

[0096] Compared to Example 4, the only difference is that the hard carbon used to assemble the pouch cell was unmodified. All other operations and parameters are 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] Compared with Example 2F, the only difference is that the type of modifier is changed, or the amount of modifier used exceeds 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 5g; all other operations and parameters were the same as in Example 2F.

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

[0104]

[0105] The performance of the pouch cells in Example 4 and Comparative Example 4 is shown in Table 2:

[0106]

[0107] As shown in Table 1, based on the comparison of Example 1 and the comparative examples (Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5), it can be seen that the innovative use of Na2ZrF6 and Na2TiF6 as modifiers, combined with carbon-based active materials, for two-stage gradient thermal modification treatment, and further combined with the joint control of the amount of modifier and temperature, can achieve synergy. Based on the physicochemical transformation of the modifier and carbon-based active materials at the stated temperature, the physicochemical structure of the negative electrode material can be optimized, thereby enhancing the electrochemical performance of sodium-ion batteries, such as improving their initial coulombic efficiency and long-cycle stability.

[0108] As can be seen from Examples 1 and 2, the special combination of modifiers, combined with the control of dosage, can improve the initial coulombic efficiency and long-term cycle stability of the obtained negative electrode.

[0109] As can be seen from Examples 1 and 3, the special two-stage gradient calcination process described above can improve the initial coulombic efficiency and long-cycle stability of the obtained negative electrode.

[0110] As shown in Table 2, through Example 4 and Comparative Example 4, the modified material obtained by the modification method described in this invention can achieve excellent high-temperature long-cycle stability.

Claims

1. A method for preparing a modified carbon-based anode active material, characterized in that, The modified carbon-based active material and the modifier were mixed in a weight ratio of 1:0.01~0.15 and then calcined at temperature T1 for the first stage, followed by a second stage of calcination at temperature T2 to obtain the modified carbon-based anode active material. The modifiers include at least one of Na2ZrF6 and Na2TiF6; Temperature T1 is 100~400℃; temperature T2 is 550~1100℃.

2. The method for preparing the modified carbon-based anode active material as described in claim 1, characterized in that, The carbon-based active material is at least one of hard carbon, graphite, and soft carbon.

3. The method for preparing the modified carbon-based anode active material as described in claim 1, characterized in that, The modifiers include Na2ZrF6 and Na2TiF6 in a weight ratio of 0.1 to 10:

1.

4. The method for preparing the modified carbon-based anode active material according to any one of claims 1 to 3, characterized in that, The modifier also contains Na3AlF6; The content of Na3AlF6 is less than 5~40 wt.%.

5. The method for preparing the modified carbon-based anode active material as described in claim 1, characterized in that, The carbon-based active material and the modifier are mixed by dry mixing or wet mixing; wherein, the wet mixing is spray drying. The atmosphere for spray drying is at least one of nitrogen and rare gases; The inlet air temperature for spray drying is 100~220℃, and the outlet air temperature is 80~200℃. The roasting atmosphere is at least one of nitrogen and rare gases; The holding time at temperature T1 is 0.5~3 h; the holding time at temperature T2 is 2~10 h.

6. A modified carbon-based anode active material prepared by the preparation method according to any one of claims 1 to 5.

7. The application of a modified carbon-based anode active material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It is used as a negative electrode active material in the preparation of sodium-ion batteries.

8. A negative electrode material for a sodium-ion battery, comprising a negative electrode active material, a binder, and a conductive agent, characterized in that, The negative electrode active material includes the modified carbon-based negative electrode active material prepared by the preparation method according to any one of claims 1 to 5.

9. A negative electrode for a sodium-ion battery, comprising a current collector and a negative electrode material composited thereon, characterized in that, The negative electrode material is the negative electrode material according to claim 8.

10. A sodium-ion battery, characterized in that, It comprises the negative electrode as described in claim 9.

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