High-rate sodium ion battery and preparation method thereof

Abstract

The invention relates to the field of sodium ion batteries, in particular to a high-rate sodium ion battery and a preparation method thereof. According to the invention, few layers of MXene materials are adopted to manufacture the hard carbon composite material and the special layered structure of MXene, so that the permeation of electrolyte can be effectively improved, the rapid transmission of charges and the diffusion of sodium ions are facilitated, the high rate performance of sodium electricity can be effectively improved, meanwhile, the storage capacity of sodium ions can be improved, and the service life of the sodium electricity is prolonged. The volume change of the hard carbon material in the charging and discharging process is effectively inhibited, and the cycle performance of the battery is favorably improved; the composite glue solution of polyvinylidene fluoride and vinylene carbonate is adopted in the positive electrode slurry, so that the cohesiveness of the positive electrode can be effectively improved, and the composite glue solution is a polymer of a vinylene carbonate additive in the electrolyte, so that the stability between the positive electrode and the electrolyte can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion batteries, and in particular to a high-rate sodium ion battery and a preparation method thereof. Background Art

[0002] Sodium-ion batteries have similar working principles to lithium-ion batteries. Unlike lithium, which is mainly imported, sodium, the raw material of sodium, is widely distributed in the earth's crust and has abundant reserves. It has become a research hotspot in the field of electrochemistry. However, sodium-ion batteries are still in the early stages of industrialization, the price of their raw materials is still relatively high, and their performance is still being optimized.

[0003] Since the atomic radius of sodium ions is relatively large, and the interlayer spacing of graphite, the negative electrode active material used in lithium batteries, is small, resulting in poor embedding and de-embedding ability of sodium ions, and therefore poor sodium storage capacity, and is not suitable for sodium ion batteries. Hard carbon materials are active materials for the negative electrodes of sodium ion batteries. At present, the main active materials for the negative electrodes of sodium batteries are hard carbon. Hard carbon materials have more sodium storage active sites. The mechanism of ion embedding and de-embedding of hard carbon materials is different from that of graphite materials. At the same time, due to its relatively low gram capacity and compacted density, hard carbon materials are rarely used as the main active materials in lithium batteries. If hard carbon is used in lithium batteries, it mainly exists in the form of additives. However, due to the small interlayer spacing of hard carbon, the performance is slightly worse for the storage and migration of larger sodium ions. Therefore, the high-rate performance of hard carbon materials is poor. In the present invention, by modifying the hard carbon material, the high-rate performance of the battery can be effectively improved, and the volume expansion of the negative electrode can be effectively improved, which is beneficial to improving the cycle performance of the battery. Summary of the invention

[0004] The purpose of the present invention is to provide a high-rate sodium ion battery and a preparation method thereof in view of the deficiencies in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention is to provide a method for preparing a high-rate sodium ion battery, the steps comprising:

[0007] S1. After dry mixing carboxymethyl cellulose, carbon black and hard carbon, deionized water is added for the first stirring, and then MXene glue is added and stirred for the second time; then N-methyl pyrrolidone is added and stirred for the third time, and then styrene butadiene emulsion is added and stirred for the fourth time to obtain negative electrode slurry;

[0008] S2, adding a binder to N-methylpyrrolidone and stirring for the first time, adding carbon black and carbon nanotubes and stirring for the second time, adding positive electrode active materials and additives and stirring for the third time, so as to obtain positive electrode slurry;

[0009] S3. The negative electrode slurry and the positive electrode slurry are coated, rolled and cut in sequence to obtain the negative electrode roll and the positive electrode roll; the positive electrode roll, the negative electrode roll and the separator are wound, and sequentially subjected to hot pressing, ear welding, film coating, shelling, welding and baking, and then the electrolyte is added, and the electrolyte is infiltrated, negative pressure formed and capacity divided in sequence to obtain the high-rate sodium ion battery.

[0010] Preferably, in step S1, the mass ratio of the carboxymethyl cellulose, the carbon black and the hard carbon is (0.5wt.%-2.0wt.%): (1.0wt.%-2.0wt.%): (93.0wt.%-96.5wt.%); the amount of the MXene glue is 0.2wt.%-0.5wt.% of the hard carbon;

[0011] The first stirring includes: low-speed stirring, medium-speed stirring and high-speed stirring in sequence; wherein the rotation speed of the low-speed stirring is 100rpm-600rpm, and the time is 10min-30min; the rotation speed of the medium-speed stirring is 800rpm-1000rpm, and the time is 10min-30min; the rotation speed of the high-speed stirring is 1200rpm-1500rpm, and the time is 10min-30min.

[0012] Preferably, in step S1, the hard carbon is biomass, with a D50 of 5 μm-7 μm and an ash content of less than 0.5%.

[0013] Preferably, in step S1, the MXene glue is Ti 3 C 2 T x Glue;

[0014] The Ti 3 C 2 T x The preparation method of the glue solution comprises:

[0015] Mix HCl solution and NaF and add them to the reactor, then add Ti 3 AlC 2 The reactor is placed at 50°C-70°C for 30h-50h. After the reactor is cooled to room temperature, the product is rinsed with deionized water until it is neutral, and the product is placed in deionized water for ultrasonic treatment. After the ultrasonic treatment, a centrifuge is used to centrifuge at a speed of 3000rpm-10000rpm for 10min-30min, and the upper layer of the dispersion is freeze-dried to obtain Ti 3 C 2 T x ; Ti 3 C 2 T xAfter ultrasonic dispersion in deionized water for 10-60 minutes, carboxymethyl cellulose was added and stirred for 20-40 minutes to obtain the Ti 3 C 2 T x Glue;

[0016] Among them, the Ti 3 C 2 T x The mass ratio of the carboxymethyl cellulose to the carboxymethyl cellulose is (1:10)-(1:5).

[0017] Preferably, in step S1, the amount of N-methylpyrrolidone used is 1.0wt.%-2.0wt.% of the hard carbon.

[0018] Preferably, in step S1, the second stirring is stirring at a rotation speed of 1200rpm-1500rpm for 60min-150min; the third stirring is stirring at a rotation speed of 1200rpm-1500rpm for 30min-60min; the fourth stirring is stirring at a rotation speed of 800rpm-1000rpm for 30min-60min.

[0019] Preferably, in step S2, the binder comprises: polyvinylidene fluoride and polyvinylene carbonate; the mass ratio of the polyvinylidene fluoride to the polyvinylene carbonate is (1:1)-(3:1); the mass ratio of the binder to the N-methylpyrrolidone is (2wt.%-6wt.%):(94wt.%-98wt.%);

[0020] The first stirring includes: low-speed stirring, medium-speed stirring and high-speed stirring in sequence; wherein the rotation speed of the low-speed stirring is 100rpm-600rpm, and the time is 10min-30min; the rotation speed of the medium-speed stirring is 1000rpm-1500rpm, and the time is 10min-30min; the rotation speed of the high-speed stirring is 2000rpm-2500rpm, and the time is 60min-120min.

[0021] Preferably, in step S2, in the positive electrode slurry, the mass ratio of the binder, the carbon black and the carbon nanotubes is: (1.0wt.%-2.0wt.%): (1.0wt.%~2.0wt.%): (1.0wt.%-2.0wt.%);

[0022] The second stirring comprises: stirring at a rotation speed of 300 rpm-600 rpm for 10 min-30 min, stirring at a rotation speed of 1000 rpm-1500 rpm for 10 min-30 min, and stirring at a rotation speed of 1800 rpm-2500 rpm for 100 min-150 min.

[0023] Preferably, in step S2, the positive electrode active material includes: layered oxide, polyanion; the additive includes: sodium oxalate, sodium alginate, sodium acrylate, Na 3 Zr 2 Si 2 PO 12 The amount of the additive is 0.1wt.%-0.5wt.% of the positive electrode active material.

[0024] The third stirring includes: stirring at a rotation speed of 100 rpm-500 rpm for 10 min-30 min, stirring at a rotation speed of 800 rpm-1200 rpm for 10 min-30 min, and stirring at a rotation speed of 1500 rpm-1800 rpm for 100 min-120 min.

[0025] Preferably, in step S3, the electrolyte contains vinylene carbonate; the diaphragm is a double-sided coated diaphragm, one side of the diaphragm is coated with aramid, and the other side is coated with polyvinylidene fluoride, and when winding, the aramid contacts the negative electrode and the polyvinylidene fluoride contacts the positive electrode.

[0026] The second aspect of the present invention is to provide a high-rate sodium ion battery prepared by the above-mentioned preparation method, wherein the high-rate sodium ion battery is a full-ear structure, and the battery capacity of the high-rate sodium ion battery is 10Ah-30Ah.

[0027] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0028] (1) In the present invention, a few-layer MXene material is used to make a hard carbon composite material. The special layered structure of MXene can effectively improve the penetration of electrolytes, and is conducive to the rapid transmission of charges and the diffusion of sodium ions, which can effectively improve the high-rate performance of sodium batteries, while improving the storage capacity of sodium ions, and effectively inhibiting the volume change of hard carbon materials during the charge and discharge process, which is beneficial to improving the cycle performance of the battery.

[0029] (2) The composite glue of polyvinylidene fluoride and polyvinyl carbonate is used in the positive electrode slurry, which can effectively improve the adhesion of the positive electrode. It is also a polymer of vinyl carbonate additive in the electrolyte, which can effectively improve the stability between the positive electrode and the electrolyte. Aramid and polyvinylidene fluoride are used in the diaphragm to coat the polyvinylidene fluoride coating layer in contact with the positive electrode, which can effectively improve the interface performance. The aramid coating layer is used in the diaphragm to significantly increase the membrane rupture temperature to above 350°C, while improving the mechanical properties, which can effectively improve the safety problems caused by negative electrode dendrites. At the same time, the electrolyte wettability can be improved, which is beneficial to improving the fast charging performance of the battery. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0032] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0033] Example 1

[0034] This embodiment provides a method for preparing a high-rate sodium ion battery, the steps comprising:

[0035] S1. Mix 30 mL 12 mol / L HCl solution with 0.7 g NaF, add to the reactor, and then add 0.7 g Ti 3 AlC 2 The reactor was placed at 60°C for 40 hours. After the reactor was cooled to room temperature, the product was rinsed with deionized water until it was neutral, and the product was placed in deionized water for ultrasonic treatment. After ultrasonic treatment, a centrifuge was used to centrifuge at a speed of 5000 rpm for 30 minutes, and the upper layer of the dispersion was freeze-dried to obtain Ti 3 C 2 T x ; Ti 3 C 2 T x After ultrasonic dispersion in deionized water for 30 minutes, carboxymethyl cellulose (CMC) was added and stirred for 30 minutes to obtain the Ti 3 C 2 T x Glue; CMC and Ti 3 C2 T x The ratio is 10:1;

[0036] CMC, carbon black (SP) and hard carbon were dry mixed in a mass ratio of 2.0wt.%: 2.0wt.%: 93.0wt.% and stirred for 30 minutes. Deionized water was added and stirred at 200rpm for 10 minutes, 800rpm for 20 minutes and 1500rpm for 30 minutes. Ti was then added. 3 C 2 T x The glue solution (0.2wt.% of the hard carbon) was stirred at 1300rpm for 60min; then 2.0wt.% of N-methylpyrrolidone (NMP) was added, and the mixture was stirred at 1200rpm for 30min. 3.0wt.% of styrene-butadiene emulsion (SBR) was added, and the mixture was stirred at 1000rpm for 30min to obtain the negative electrode slurry;

[0037] S2. Add the binder (polyvinylidene fluoride (PVDF): polyvinyl carbonate (PVCA) = 1:1) to NMP (binder: NMP = 2:98), stir at 300 rpm for 10 min, 1000 rpm for 20 min, and 2000 rpm for 120 min, add 2 wt.% SP and 1.5 wt.% carbon nanotubes (CNT), stir at 300 rpm for 10 min, 1000 rpm for 10 min, and 2300 rpm for 100 min, then add the positive electrode active material and 0.2 wt.% Na 3 Zr 2 Si 2 PO 12 , stirring at 100 rpm for 10 min, 800 rpm for 20 min, and 1800 rpm for 120 min to obtain a positive electrode slurry;

[0038] S3. The negative electrode slurry and the positive electrode slurry are coated, rolled and cut in sequence to obtain the negative electrode roll and the positive electrode roll; the positive electrode roll, the negative electrode roll and the separator are wound, and the aramid contacts the negative electrode and the polyvinylidene fluoride contacts the positive electrode during winding, and after hot pressing, ear welding, film coating, shelling, welding and baking in sequence, an electrolyte is added, and the electrolyte is infiltrated, negative pressure formed and capacity divided in sequence to obtain the high-rate sodium ion battery.

[0039] Example 2

[0040] This embodiment provides another method for preparing a high-rate sodium ion battery, the steps comprising:

[0041] S1. Mix 30 mL 12 mol / L HCl solution with 0.7 g NaF, add to the reactor, and then add 0.7 g Ti 3 AlC 2 The reactor was placed at 60°C for 40 hours. After the reactor was cooled to room temperature, the product was rinsed with deionized water until it was neutral, and the product was placed in deionized water for ultrasonic treatment. After ultrasonic treatment, a centrifuge was used to centrifuge at 7000 rpm for 20 minutes, and the upper layer of the dispersion was freeze-dried to obtain Ti 3 C 2 T x ; Ti 3 C 2 T x After ultrasonic dispersion in deionized water for 60 minutes, CMC was added and stirred for 30 minutes to obtain the Ti 3 C 2 T x Glue; CMC and Ti 3 C 2 T x The ratio is 5:1;

[0042] CMC, SP and hard carbon were dry mixed in a mass ratio of 1.5wt.%:1.0wt.%:95.5wt.% and stirred for 30min. Deionized water was added and stirred at 300rpm for 15min, 1000rpm for 20min and 1200rpm for 30min. Ti was then added. 3 C 2 T x The glue solution (0.5wt.% of the hard carbon) was stirred at 1500rpm for 60min; then 1.0wt.% of NMP was added, stirred at 1500rpm for 30min, and 2.0wt.% of SBR was added, stirred at 800rpm for 40min to obtain the negative electrode slurry;

[0043] S2. Add the binder (PVDF:PVCA=2:1) ​​to NMP (binder:NMP=3:97), stir at 500 rpm for 15 min, 1500 rpm for 15 min, and 2500 rpm for 100 min, add 1.5 wt.% SP and 2 wt.% CNT, stir at 300 rpm for 10 min, 1300 rpm for 10 min, and 2000 rpm for 100 min, then add the positive electrode active material and 0.1 wt.% sodium oxalate, stir at 200 rpm for 15 min, 1000 rpm for 15 min, and 1500 rpm for 120 min to obtain the positive electrode slurry;

[0044] S3. The negative electrode slurry and the positive electrode slurry are coated, rolled and cut in sequence to obtain the negative electrode roll and the positive electrode roll; the positive electrode roll, the negative electrode roll and the separator are wound, and the aramid contacts the negative electrode and the polyvinylidene fluoride contacts the positive electrode during winding, and after hot pressing, ear welding, film coating, shelling, welding and baking in sequence, an electrolyte is added, and the electrolyte is infiltrated, negative pressure formed and capacity divided in sequence to obtain the high-rate sodium ion battery.

[0045] Comparative Example 1

[0046] This comparative example provides another method for preparing a high-rate sodium-ion battery, in which the negative electrode slurry does not contain MXene material, and the binder in the positive electrode slurry is only PVDF.

[0047] Comparative Example 2

[0048] This comparative example provides another method for preparing a high-rate sodium-ion battery, in which the negative electrode slurry does not contain MXene material, the binder in the positive electrode slurry is only PVDF, and the diaphragm is a ceramic-coated diaphragm.

[0049] Detection Example

[0050] The batteries prepared by the preparation methods described in Example 1-2 and Comparative Example 1-2 were subjected to rate test and cycle performance test, respectively. The test results are shown in Table 1.

[0051] Table 1

[0052] plan 5.0C / 0.1C 1.0C charge / 4.0C discharge cycle 1000 times Example 1 96.58％ 89.4％ Example 2 94.33％ 88.7％ Comparative Example 1 90.15％ 80.5％ Comparative Example 2 87.63％ 78.1％

[0053] In summary, the battery prepared by the preparation method described in Examples 1-2 can effectively improve the rate performance and cycle performance of sodium ion batteries; the special layered structure of MXene can effectively improve the penetration of electrolytes, and is beneficial to the rapid transfer of charges and diffusion of sodium ions, which can effectively improve the high-rate performance of sodium batteries, while improving the storage capacity of sodium ions, and effectively inhibiting the volume change of hard carbon materials during the charge and discharge process, which is beneficial to improving the cycle performance of the battery; the composite glue of polyvinylidene fluoride and polyvinyl carbonate is used in the positive electrode slurry, which can effectively improve the adhesion of the positive electrode, and is a polymer of vinyl carbonate additive in the electrolyte, which can effectively improve the stability between the positive electrode and the electrolyte.

[0054] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-rate sodium ion battery, characterized in that the steps include: S1. After dry mixing carboxymethyl cellulose, carbon black and hard carbon, deionized water is added for the first stirring, and then MXene glue is added and stirred for the second time; then N-methyl pyrrolidone is added and stirred for the third time, and then styrene butadiene emulsion is added and stirred for the fourth time to obtain negative electrode slurry; S2, adding a binder to N-methylpyrrolidone and stirring for the first time, adding carbon black and carbon nanotubes and stirring for the second time, adding positive electrode active materials and additives and stirring for the third time, so as to obtain positive electrode slurry; S3. The negative electrode slurry and the positive electrode slurry are coated, rolled and cut in sequence to obtain the negative electrode roll and the positive electrode roll; the positive electrode roll, the negative electrode roll and the separator are wound, and sequentially subjected to hot pressing, ear welding, film coating, shelling, welding and baking, and then the electrolyte is added, and the electrolyte is infiltrated, negative pressure formed and capacity divided in sequence to obtain the high-rate sodium ion battery.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of the carboxymethyl cellulose, the carbon black and the hard carbon is (0.5wt.%-2.0wt.%): (1.0wt.%-2.0wt.%): (93.0wt.%-96.5wt.%); The amount of the MXene glue is 0.2wt.%-0.5wt.% of the hard carbon; The first stirring includes: low-speed stirring, medium-speed stirring and high-speed stirring in sequence; wherein the rotation speed of the low-speed stirring is 100rpm-600rpm, and the time is 10min-30min; the rotation speed of the medium-speed stirring is 800rpm-1000rpm, and the time is 10min-30min; the rotation speed of the high-speed stirring is 1200rpm-1500rpm, and the time is 10min-30min.

3. The preparation method according to claim 1, characterized in that: In step S1, the hard carbon is biomass, D50 is 5 μm-7 μm, and ash content is less than 0.5%.

4. The preparation method according to claim 1, characterized in that: In step S1, the MXene glue is Ti3C2T x Glue; The Ti3C2T x The preparation method of the glue solution comprises: HCl solution and NaF were mixed and added to the reactor, and then Ti3AlC2 was added. The reactor was placed at 50℃-70℃ for 30h-50h. After the reactor was cooled to room temperature, the product was rinsed with deionized water until it was neutral, and the product was placed in deionized water for ultrasonic treatment. After ultrasonic treatment, a centrifuge was used to centrifuge at a speed of 3000rpm-10000rpm for 10min-30min, and the upper layer of the dispersion was freeze-dried to obtain Ti3C2T x ; Ti3C2T x After ultrasonic dispersion in deionized water for 10-60 min, carboxymethyl cellulose was added and stirred for 20-40 min to obtain the Ti3C2T x Glue; Among them, the Ti3C2T x The mass ratio of the carboxymethyl cellulose to the carboxymethyl cellulose is (1:10)-(1:5).

5. The preparation method according to claim 1, characterized in that: In step S1, the second stirring is stirring at a rotation speed of 1200rpm-1500rpm for 60min-150min; the third stirring is stirring at a rotation speed of 1200rpm-1500rpm for 30min-60min; the fourth stirring is stirring at a rotation speed of 800rpm-1000rpm for 30min-60min.

6. The preparation method according to claim 1, characterized in that: In step S2, the binder includes: polyvinylidene fluoride and polyvinylene carbonate; the mass ratio of the polyvinylidene fluoride to the polyvinylene carbonate is (1:1)-(3:1); the mass ratio of the binder to the N-methylpyrrolidone is (2wt.%-6wt.%):(94wt.%-98wt.%); The first stirring includes: low-speed stirring, medium-speed stirring and high-speed stirring in sequence; wherein the rotation speed of the low-speed stirring is 100rpm-600rpm, and the time is 10min-30min; the rotation speed of the medium-speed stirring is 1000rpm-1500rpm, and the time is 10min-30min; the rotation speed of the high-speed stirring is 2000rpm-2500rpm, and the time is 60min-120min.

7. The preparation method according to claim 1, characterized in that: In step S2, in the positive electrode slurry, the mass ratio of the binder, the carbon black, and the carbon nanotubes is: (1.0wt.%-2.0wt.%): (1.0wt.%~2.0wt.%): (1.0wt.%-2.0wt.%); The second stirring comprises: stirring at a rotation speed of 300 rpm-600 rpm for 10 min-30 min, stirring at a rotation speed of 1000 rpm-1500 rpm for 10 min-30 min, and stirring at a rotation speed of 1800 rpm-2500 rpm for 100 min-150 min.

8. The preparation method according to claim 1, characterized in that: In step S2, the positive electrode active material includes: layered oxide, polyanion; the additive includes: sodium oxalate, sodium alginate, sodium acrylate, Na3Zr2Si2PO 12 The amount of the additive is 0.1wt.%-0.5wt.% of the positive electrode active material. The third stirring includes: stirring at a rotation speed of 100 rpm-500 rpm for 10 min-30 min, stirring at a rotation speed of 800 rpm-1200 rpm for 10 min-30 min, and stirring at a rotation speed of 1500 rpm-1800 rpm for 100 min-120 min.

9. The preparation method according to claim 1, characterized in that: In step S3, the electrolyte contains vinylene carbonate; the diaphragm is a double-sided coated diaphragm, one side of the diaphragm is coated with aramid, and the other side is coated with polyvinylidene fluoride, and when winding, the aramid contacts the negative electrode and the polyvinylidene fluoride contacts the positive electrode.

10. A high-rate sodium ion battery prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The high-rate sodium ion battery has a full-ear structure, and the battery capacity of the high-rate sodium ion battery is 10Ah-30Ah.