Sodium ion battery and application thereof

Abstract

The invention discloses a sodium ion battery and application thereof. The sodium ion battery comprises a negative electrode plate, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer arranged on the negative electrode current collector, an active substance in the negative electrode material layer is a hard carbon material, the ratio of the slope area capacity of the hard carbon material to the negative electrode total battery design capacity is 60-90%, and the slope area capacity of the hard carbon material is 140 mAh / g-180 mAh / g. According to the invention, the sodium ion battery is prepared by adopting the hard carbon material in the long slope region and the specific positive and negative electrode materials which are mutually matched, mutually coupled and mutually promoted. The sodium ion battery supports ultrahigh-rate pulse charging, such as 40-50C pulse charging under a high SOC (State of Charge), and also has high-rate cycle performance, for example, the 3C and 8000 cycle capacity retention rate is up to 82.57%, and the safety of the sodium ion battery in the high-rate pulse charging and cycle process is extremely good.

Description

Technical Field

[0001] This invention relates to a sodium-ion battery and its application. Background Technology

[0002] Currently, the charge / discharge performance of commercially available lithium iron phosphate and lead-acid batteries is limited to below 10C, such as BYD's megawatt flash charging. Sodium-ion batteries, as a novel electrochemical energy storage battery, far surpass existing commercially available lithium iron phosphate and lead-acid batteries in terms of high and low temperature performance and long cycle life. However, their charge / discharge performance is only 5-10C, which limits their application in ultra-high rate scenarios, such as kinetic energy recovery, cranes, and heavy truck starting and stopping. In particular, in the fields of HEVs and construction machinery, the extreme operating conditions for energy recovery are at high SOC levels, such as 80% SOC, charging at 30-50C for 3 seconds. This easily leads to a rapid drop in the negative electrode potential, and when the potential reaches 0V, sodium is deposited at the negative electrode, severely affecting battery performance.

[0003] Currently, there are no publicly available reports on ultra-high rate pulses (e.g., 50C) at high SOC (e.g., 80% SOC) for traditional technologies (lithium iron phosphate batteries, lead-acid batteries) and emerging sodium battery technologies.

[0004] While some existing technologies disclose research on improving battery rate performance, they still do not address how to achieve ultra-high rate pulses at high SOC. For example, Chinese patent application CN 202411206868.7 discloses a high-rate sodium-ion battery, which is fabricated using a hard carbon composite material (employing few-layer MXene material), combined with specific positive electrode slurry, electrolyte additives, and a separator. Although this process improves the battery's fast-charging performance, its maximum rate performance in rate testing is only 5C.

[0005] Chinese patent application CN202411006588.1 discloses a high-rate-charging sodium-ion battery negative electrode sheet with a specific three-layer structure and a reasonable particle distribution design. Although it claims that during fast charging, a gradient distribution of ion concentration from high to low is formed in the direction of electrolyte diffusion to current collector, thereby effectively improving the overall rate-charging performance of the negative electrode sheet, its maximum rate-cycle test is only 10C.

[0006] These problems urgently need to be addressed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of existing technologies (lithium iron phosphate batteries, lead-acid batteries) and emerging sodium battery technologies, which have not been publicly reported on ultra-high rate pulse under high SOC conditions, and sodium-ion batteries have the defect of sodium deposition on the negative electrode under high SOC and high rate pulse conditions, which seriously affects the performance of the battery. The present invention provides a sodium-ion battery and its application.

[0008] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0009] In a first aspect, the present invention provides a sodium-ion battery, comprising a positive electrode and a negative electrode, wherein the negative electrode comprises a negative current collector and a negative electrode material layer disposed on the negative current collector, wherein the active material in the negative electrode material layer is a hard carbon material, the ratio of the ramp region capacity of the hard carbon material to the design capacity of the negative electrode full cell is 60-90%, and the ramp region capacity of the hard carbon material is 140 mAh / g-180 mAh / g.

[0010] In this invention, the ratio of the slope region capacity of the hard carbon material to the design capacity of the negative electrode full cell is preferably 60-85%, for example 63%, 65%, 70%, 75%, 79.5%, 82% or 85%.

[0011] In this invention, the ramp capacity of the hard carbon material is generally obtained by half-cell testing of the negative electrode. For example, the half-cell is discharged at a current density of 0.1C. During discharge, the voltage corresponding to the ramp capacity is above 0.1V, and the voltage corresponding to the plateau capacity is between 0.1V and 0V.

[0012] In a preferred embodiment, the slope zone capacity is obtained by the following method:

[0013] S1 uses a conventional testing system in the field (e.g., the charge / discharge testing equipment Xinwei 5V, 10mA) to test the negative electrode. First, the half cell is discharged to 0V at a current density of 0.1C (30mA / g) to obtain the discharge capacity. After resting, it is charged to 2.0V at a current density of 0.1C to obtain the charging capacity. The charge / discharge voltage range is 0-2.0V.

[0014] S2 According to step S1, the second cycle discharge and charge curve of the negative electrode can be obtained. During discharge, the voltage corresponding to the capacity in the ramp region is above 0.1V, and the voltage corresponding to the capacity in the plateau region is between 0.1V and 0V.

[0015] In a preferred embodiment, the charge-discharge curve of the hard carbon material half-cell in the second week is as follows: Figure 1 As shown.

[0016] In a preferred embodiment, the preparation method of the half-cell may include: 95% hard carbon material, 1.5% Super P, and 3.5% CMC2200, where the percentages are the mass percentages of each component relative to the total amount of "hard carbon material, Super P, and CMC2200", using deionized water as a solvent, adjusting the solid content to 50%, and grinding in a planetary ball mill at 400 rpm for 30 min to obtain a slurry; coating the slurry onto copper foil and drying to obtain the half-cell;

[0017] The hard carbon material was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1; the Super P was purchased from Temico; and the CMC2200 was purchased from DAICEL of South Korea.

[0018] In this invention, the slope capacity of the hard carbon material is preferably 145 mAh / g-175 mAh / g, for example 150 mAh / g, 159 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, and 175 mAh / g, more preferably 150 mAh / g-170 mAh / g. The hard carbon material can be used in this invention as long as it meets the above-mentioned slope capacity and the ratio of slope capacity to the design capacity of the negative electrode full cell. In this invention, provided that the ratio of the slope capacity of the hard carbon material to the design capacity of the negative electrode full cell is met, the hard carbon material can be prepared according to conventional methods in the art or obtained commercially. For example, the preparation method of the hard carbon material may include the following steps: pre-carbonization, crushing, calcination, and cooling of biomass raw materials.

[0019] In a preferred embodiment, the hard carbon material is available from Shenzhen Jia Na Energy Technology Co., Ltd., and its model number is JNHCB-1.

[0020] In this invention, the design capacity of the negative electrode full battery is preferably 160 mAh / g-280 mAh / g, such as 165 mAh / g, 170 mAh / g, 175 mAh / g, 180 mAh / g, 185 mAh / g, 190 mAh / g, 200 mAh / g, 210 mAh / g, 220 mAh / g, 230 mAh / g, 240 mAh / g, 250 mAh / g, 260 mAh / g, or 270 mAh / g, and more preferably 180 mAh / g-220 mAh / g.

[0021] In this invention, the preferred design capacity of the positive electrode full battery is 96 mAh / g - 100 mAh / g, for example, 98 mAh / g.

[0022] In this invention, the N / P ratio of the sodium-ion battery is preferably designed to be 1.20-1.35, for example, 1.2, 1.25 or 1.3.

[0023] In this invention, the preparation method of the negative electrode sheet can be conventional in the art. For example, a negative electrode slurry containing the hard carbon material is uniformly coated on both sides of the carbon-coated aluminum foil of the negative electrode current collector, dried in an electric heating oven, and then rolled and slit to obtain the negative electrode sheet. The drying, rolling, and slitting operations are all conventional operations.

[0024] In a preferred embodiment, the carbon-coated aluminum foil can be purchased from the high-adhesion products of Shenzhen Yuqiang New Materials Co., Ltd.

[0025] The preparation method of the negative electrode slurry can be conventional in the art, such as using a planetary mixer to mix the components evenly.

[0026] The preferred formulation of the negative electrode slurry includes: 92-96% hard carbon material, 0.5-2.5% Super P, 0-1% carbon black, 0.08-0.5% CNT and 2.0-4.0% PVDF, where the percentages are the mass percentages of each component relative to the total raw materials.

[0027] In the negative electrode slurry, the amount of hard carbon material is preferably 92.5-96%, for example 92.9%, 94.2%, 94.3%, 95.3%, 95.7% or 95.9%.

[0028] In the negative electrode slurry, the amount of Super P is preferably 0.8-2.2%, for example 1.0%, 1.5% or 2.0%.

[0029] In the negative electrode slurry, the specific surface area of ​​Super P is preferably 54-66 m². 2 / g, for example 60m 2 / g.

[0030] In the negative electrode slurry, the amount of carbon black is preferably 0.1-0.9%, for example 0.2%, 0.5% or 0.8%.

[0031] In the negative electrode slurry, the specific surface area of ​​the carbon black is preferably 700-1400 m². 2 / g, for example 800m 2 / g、1200m 2 / g and 1400m 2 / g.

[0032] In the negative electrode slurry, the carbon black can be selected from Ketjen Black EC-300J (specific surface area 800 m²). 2 / g), EC600JD (specific surface area 1200m²) 2 / g) and ECP600JD (specific surface area 1400m²) 2 One or more of the following ( / g).

[0033] In the negative electrode slurry, the amount of CNT is preferably 0.09-0.4%, for example 0.1%, 0.2% or 0.3%.

[0034] In the negative electrode slurry, the CNTs can be purchased from OCSIAL's oil-based single-walled carbon nanotubes.

[0035] In the negative electrode slurry, the amount of PVDF is preferably 2.5-4.0%, for example 3%, 3.5% or 4%.

[0036] In some preferred embodiments, the negative electrode slurry may be any of the following formulations:

[0037] Formula-1: Hard carbon fiber 95.9%, Super P 1.0%, CNT 0.1%, and PVDF 3%;

[0038] Formula-2: Hard carbon fiber 95.3%, Super P 1.5%, CNT 0.2%, and PVDF 3%;

[0039] Formula-3: Hard carbon material 94.2%, Super P 1.5%, CNT 0.3%, and PVDF 4%;

[0040] Formula-4: Hard carbon material 95.7%, Super P 1.0%, carbon black 0.2%, CNT 0.1%, and PVDF 3%;

[0041] Formula-5: Hard carbon material 94.3%, Super P 1.0%, carbon black 0.5%, CNT 0.2%, and PVDF 4.0%;

[0042] Formula-6: Hard carbon material 92.9%, Super P 2.0%, Carbon black 0.8%, CNT 0.3%, PVDF 4.0%;

[0043] The hard carbon material was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1, with a specific surface area of ​​approximately 60 m². 2 / g, CNTs were purchased from OCSIAL's oil-based single-walled carbon nanotubes, and the carbon black was EC600JD with a specific surface area of ​​1200m². 2 / g.

[0044] In this invention, the positive electrode sheet can be prepared by conventional methods in the art, for example: uniformly coating a positive electrode slurry containing a positive electrode active material onto both sides of a carbon-coated aluminum foil current collector, drying it in an electric heating oven, and then rolling and slitting it to obtain the positive electrode sheet. The drying, rolling, and slitting operations are all conventional operations.

[0045] The preferred positive electrode active material is sodium iron pyrophosphate (NFPP).

[0046] In a preferred embodiment, the sodium iron pyrophosphate NFPP is available from Shenzhen Jia Na Energy Technology Co., Ltd., model JNFP-1.

[0047] In a preferred embodiment, the carbon-coated aluminum foil can be purchased from Shenzhen Yuqiang New Materials Co., Ltd., a high-adhesion product.

[0048] The preparation method of the positive electrode slurry can be conventional in the art, such as using a planetary mixer to mix the components evenly.

[0049] The preferred formulation of the positive electrode slurry includes: sodium iron pyrophosphate NFPP 92-97%, Super P 1.0-2.2%, carbon black 0.1-1.0%, CNT 0.05-0.3%, and PVDF 2.0-4.5%, where the percentages are the mass percentages of each component relative to the total raw materials.

[0050] In the positive electrode slurry, the amount of sodium iron pyrophosphate (NFPP) is preferably 92.5-97%, for example 92.95%, 93.95%, 95.35% or 96.75%.

[0051] In the positive electrode slurry, the amount of Super P is preferably 1.0-2.0%, for example 1.0%, 1.5% or 2.0%.

[0052] In the positive electrode slurry, the specific surface area of ​​Super P is preferably 54-66 m². 2 / g, for example 60m 2 / g.

[0053] In the positive electrode slurry, the amount of carbon black is preferably 0.1-0.9%, for example 0.2%, 0.5% or 0.8%.

[0054] In a preferred embodiment of the positive electrode slurry, the carbon black may be selected from Cabot MAX30 and / or Cabot MAX90.

[0055] In the positive electrode slurry, the amount of CNT is preferably 0.05-0.28%, for example 0.05%, 0.15% or 0.25%.

[0056] In a preferred embodiment of the cathode slurry, the CNTs are available from OCSIAL's oil-based single-walled carbon nanotubes.

[0057] In the positive electrode slurry, the amount of PVDF is preferably 2.0-4.2%, for example 2%, 2.5%, 3.0% or 4.0%.

[0058] In some preferred embodiments, the positive electrode slurry may be any of the following formulations:

[0059] Formula +1: NFPP 96.75%, Super P 1.0%, Carbon Black 0.2%, CNT 0.05%, PVDF 2.0%;

[0060] Formula +2: NFPP 95.35%, Super P 1.5%, Carbon Black 0.5%, CNT 0.15%, PVDF 2.5%;

[0061] Formula +3: NFPP 93.95%, Super P 2.0%, Carbon Black 0.8%, CNT 0.25%, PVDF 3.0%;

[0062] Formula +4: NFPP 92.95%, Super P 2.0%, Carbon Black 0.8%, CNT 0.25%, PVDF 4.0%;

[0063] NFPP, specifically sodium iron pyrophosphate, was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNFP-1. Super P has a specific surface area of ​​approximately 60 m² / g. 2 / g, CNTs are oil-based single-walled carbon nanotubes purchased from OCSIAL, and carbon black is selected from Cabot MAX30 and / or Cabot MAX90.

[0064] In a preferred embodiment, the ultra-high rate pulse voltage curve of the sodium-ion battery at 80% SOC can be as follows: Figure 2 .

[0065] In a preferred embodiment, the voltage range and curve for normal operation of the sodium-ion battery full cell can be as follows: Figure 3 .

[0066] In a preferred embodiment, the full-cell cycle curve of the sodium-ion battery can be: Figure 5 .

[0067] Secondly, the present invention also provides a method for preparing a sodium-ion battery, which can be obtained by conventional methods in the art, such as stacking the positive electrode, the separator and the negative electrode in sequence, then loading the stacked bare cells into a soft-pack casing, and obtaining a sodium-ion battery after top-side sealing, liquid injection, formation, capacity testing and sorting.

[0068] Thirdly, the present invention also provides an application of the sodium-ion battery in the fields of power tools or motor vehicles.

[0069] In this invention, the motor vehicle may include, but is not limited to, motor vehicles used in the fields of HEV, motorcycles, or construction machinery. HEV (Hybrid Electric Vehicle) generally refers to a hybrid electric vehicle, meaning a vehicle that is equipped with both a combustion engine and an electric motor.

[0070] In this invention, the sodium-ion battery can be applied to any scenario requiring high-rate pulses.

[0071] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0072] The reagents and raw materials used in this invention are all commercially available.

[0073] The positive and progressive effects of this invention are as follows:

[0074] This invention utilizes hard carbon materials in a long sloping region and specific positive and negative electrode materials to work together, couple with each other, and promote each other to produce a sodium-ion battery.

[0075] The sodium-ion battery of the present invention not only has higher electrode porosity, which helps the electrolyte to wet and improves the diffusion rate of sodium ions, but also forms a good electronic conductive network (multi-level conductive agent system) and porous and loose pores in the electrode to form an ion conductive network (porous structure). These pores are electrolyte wetting channels to ensure rapid migration of sodium ions.

[0076] The sodium-ion battery of the present invention supports ultra-high rate pulse charging, such as 40-50C pulse charging at high SOC, and also has high rate cycle performance, such as 82.57% capacity retention after 8000 cycles at 3C. Moreover, the sodium-ion battery has excellent safety during high rate pulse charging and cycling.

[0077] In the preferred embodiment, considering extreme cases, at 80% SOC, the full battery voltage is below 3.4V after 14 seconds of 50C charging. This can be considered as the negative electrode potential being above 0V, thus preventing sodium deposition. At this point, the battery charge is close to 100%, specifically 99.44%. Attached Figure Description

[0078] Figure 1 The charge-discharge curve of the half-cell prepared by the hard carbon material in Example 1 during the second week is shown.

[0079] Figure 2 The experimental group's battery exhibits ultra-high rate pulse voltage curves at 80% SOC.

[0080] Figure 3 The voltage range and curves for normal operation of the full battery in the experimental group are shown.

[0081] Figure 4 To compare the ultra-high rate pulse voltage curves of the battery pack at 80% SOC.

[0082] Figure 5 The cycling curves are for the experimental and control groups of batteries. Detailed Implementation

[0083] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0084] In this invention, all test conditions were conducted at room temperature (25°C).

[0085] Example 1

[0086] 1. Preparation of hard carbon materials

[0087] Half-cells were fabricated using hard carbon materials, and their performance was tested.

[0088] Half-cell preparation: 95% hard carbon material (purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1), 1.5% Super P (purchased from TMEGO), and 3.5% CMC2200 (purchased from DAICEL, South Korea). The percentages are the mass percentages of each component relative to the total amount of hard carbon material, Super P, and CMC2200. Deionized water was used as the solvent, and the solid content was adjusted to 50%. The mixture was ground in a planetary ball mill at 400 rpm for 30 minutes to obtain a slurry. The slurry was coated onto copper foil and dried to obtain the half-cell.

[0089] Half-cell testing method: First, discharge the half-cell to 0V at a current density of 0.1C 30mA / g to obtain the discharge capacity. Then, allow it to stand and charge it to 2.0V at a current density of 0.1C to obtain the charging capacity. The charge / discharge voltage range is 0-2.0V. Charge / discharge testing equipment: Xinwei 5V 10mA.

[0090] The charge-discharge curve of the hard carbon material half-cell in the second week is as follows: Figure 1 As shown, the voltage corresponding to the capacity in the ramp region is above 0.1V, and the capacity in the ramp region is 159 mAh / g. The region between 0.1V and 0V is a plateau region, but in the area near 0.1V of the plateau region, there are still some small ramps, extending to about 200 mAh / g. Therefore, hard carbon materials have a relatively long ramp region, with a capacity of about 200 mAh / g.

[0091] 2. Preparation of negative electrode sheet

[0092] Hard carbon negative electrode slurry was uniformly coated onto both sides of the carbon-coated aluminum foil of the negative electrode current collector. After drying in an electric heating oven, the negative electrode sheets were obtained by rolling and slitting. The drying, rolling, and slitting operations were all standard procedures. The carbon-coated aluminum foil was purchased as a high-adhesion product from Shenzhen Yuqiang New Materials Co., Ltd.

[0093] The hard carbon anode slurry can be any of the following formulations, where each percentage represents the mass percentage of each component relative to the total raw materials of the formulation. A planetary mixer is used to thoroughly mix all components of the formulation:

[0094] Formula-1: Hard carbon material 95.9% Super P 1.0% CNT 0.1% PVDF 3%;

[0095] Formula-2: Hard carbon material 95.3% Super P 1.5% CNT 0.2% PVDF 3%;

[0096] Formula-3: Hard carbon material 94.2% Super P 1.5% CNT 0.3% PVDF 4%;

[0097] Formula-4: Hard carbon material 95.7%, Super P 1.0%, Carbon black A 0.2%, CNT 0.1%, PVDF 3%;

[0098] Formula-5: Hard carbon material 94.3%, Super P 1.0%, Carbon black A 0.5%, CNT 0.2%, PVDF 4.0%;

[0099] Formula-6: Hard carbon material 92.9%, Super P 2.0%, Carbon black A 0.8%, CNT 0.3%, PVDF 4.0%.

[0100] In the above formulation, the hard carbon material was purchased from Shenzhen Jia Na Energy Technology Co., Ltd., model JNHCB-1; the specific surface area of ​​Super P is approximately 60 m². 2 / g, CNTs were purchased from OCSIAL's oil-based single-walled carbon nanotubes, and carbon black A was ECP600JD with a specific surface area of ​​1200m². 2 / g.

[0101] The negative electrode slurry uses an oil-based system with PVDF as the binder. Hard carbon material is combined with three different conductive agents, resulting in higher electrode porosity, which aids in electrolyte wetting and improves the sodium ion diffusion rate. Furthermore, it forms a robust electronic conductivity network (multi-level conductive agent system) and a porous pore structure, creating an ion conductivity network (porous structure). These pores serve as electrolyte wetting channels, ensuring rapid sodium ion migration. This overall negative electrode design is more conducive to improving the overall battery performance.

[0102] 3. Preparation of positive electrode sheet

[0103] The positive electrode slurry was uniformly coated onto both sides of the carbon-coated aluminum foil of the positive electrode current collector. After drying in an electric heating oven, the positive electrode sheet was obtained by rolling and slitting. The drying, rolling, and slitting operations were all standard procedures. The carbon-coated aluminum foil was purchased as a high-adhesion product from Shenzhen Yuqiang New Materials Co., Ltd.

[0104] The positive electrode slurry can be any of the following formulations, where each percentage represents the mass percentage of each component relative to the total raw materials of the formulation. A planetary mixer is used to thoroughly mix all components of the formulation:

[0105] Formula +1: NFPP 96.75%, Super P 1.0%, Carbon Black B 0.2%, CNT 0.05%, PVDF 2.0%;

[0106] Formula +2: NFPP 95.35%, Super P 1.5%, Carbon Black B 0.5%, CNT 0.15%, PVDF 2.5%;

[0107] Formula +3: NFPP 93.95%, Super P 2.0%, Carbon Black B 0.8%, CNT 0.25%, PVDF 3.0%;

[0108] Formula +4: NFPP 92.95%, Super P 2.0%, Carbon Black B 0.8%, CNT 0.25%, PVDF 4.0%.

[0109] In the above formulation, NFPP is sodium iron pyrophosphate, purchased from Shenzhen Jia Na Energy Technology Co., Ltd., model JNFP-1. Super P has a specific surface area of ​​approximately 60 m² / g. 2 / g, CNTs are oil-based single-walled carbon nanotubes purchased from OCSIAL, and carbon black B is selected from Cabot MAX90.

[0110] The positive electrode slurry adopts an oil-based positive electrode system, with three conductive agents compounded to construct a good porous electrode and electronic conductivity network, which is beneficial to improving the overall performance of the battery.

[0111] 4. Preparation of sodium-ion batteries

[0112] The positive electrode, separator, and negative electrode are stacked in sequence, and then the stacked bare cells are put into a soft-pack casing. After top and side sealing, electrolyte injection, formation, capacity testing, and sorting, a sodium-ion battery is obtained.

[0113] Sodium-ion batteries (experimental group) were prepared using Formula-2 and Formula+2 as the negative and positive electrodes, respectively. In the sodium-ion batteries, the designed capacity of the negative electrode full cell was 200 mAh / g (79.5% capacity in the slope region), the designed capacity of the positive electrode full cell was 98 mAh / g, and the designed N / P ratio was 1.2.

[0114] Comparative Example 1

[0115] Sodium-ion batteries (control group) were prepared using formulation-2 and formulation+2 as the negative and positive electrodes, respectively. In the sodium-ion batteries, the designed capacity of the negative electrode full cell was 285 mAh / g (55.8% capacity in the slope region), the designed capacity of the positive electrode full cell was 98 mAh / g, and the designed N / P ratio was 1.2.

[0116] Effect Example

[0117] Full battery charge / discharge testing equipment: Xinwei 5V6A test cabinet.

[0118] Figure 2 This is the ultra-high rate pulse voltage curve of the experimental group's battery at 80% SOC. It shows that at 80% SOC, after charging at a 50C rate for 14 seconds, the voltage after polarization is only 3.3966V, which does not exceed the full-cell design upper limit voltage of 3.4V. After resting for 1 second, the voltage becomes 3.273V. At this point, the battery's charge is close to 100%, specifically 99.44% (80% + 50C * 14 / 3600 * 100% = 99.44%). The experimental group meets the design requirements and has no risk of sodium deposition.

[0119] Test conditions: 1C constant current and constant voltage charging to 3.4V, 0.05C cutoff, rest for 5 minutes, then 1C discharge to 1.5V. Figure 3 This shows the voltage range and curves for normal operation of the full cell in the experimental group. After the pulse, the voltage quickly recovered to below 3.2V after resting. This indicates the normal operating voltage range of the full cell, serving as a supplement to the experimental and control groups, and facilitating understanding that exceeding 3.4V poses a risk of sodium deposition.

[0120] Figure 4 To compare the ultra-high rate pulse voltage curves of the battery pack at 80% SOC. Therefore... It can be seen that, At 80% SOC, after charging at a 50C rate for 14 seconds, the voltage after polarization was 4.2262V, exceeding the full-cell design limit of 4.2V. After resting for 1 second, the voltage dropped to 3.8790V. The control group did not meet the experimental design requirements and there was a risk of sodium precipitation.

[0121] Cyclic curve test conditions: 3C constant current and constant voltage charging to 3.4V, 0.05C cutoff, rest for 5 minutes, then 3C discharge to 1.5V. After the first charge-discharge cycle, continue cyclic charge-discharge testing at a specific current density (3C) within the same voltage range. Record the discharge capacity at the 2000, 4000, 6000, and 8000 cycles, and calculate the capacity retention rate by comparing it with the initial discharge capacity.

[0122] Figure 5The images show the cycle curves of the experimental and control groups. It is evident that, compared to the control group, the experimental group exhibits improved high-rate pulse performance as well as enhanced cycle performance.

[0123] Table 1 shows the discharge capacity and capacity retention rate at different numbers of cycles during the cyclic test.

[0124] Table 1

[0125]

Claims

1. A sodium-ion battery, characterized in that, It includes a positive electrode and a negative electrode. The negative electrode includes a negative current collector and a negative electrode material layer disposed on the negative current collector. The active material in the negative electrode material layer is hard carbon material. The ratio of the slope region capacity of the hard carbon material to the design capacity of the negative electrode full cell is 60-90%, and the slope region capacity of the hard carbon material is 140 mAh / g-180 mAh / g.

2. The sodium-ion battery as described in claim 1, characterized in that, The ratio of the slope region capacity of the hard carbon material to the design capacity of the negative electrode full cell is 60-85%, for example, 63%, 65%, 70%, 75%, 79.5%, 82% or 85%.

3. The sodium-ion battery as described in claim 1, characterized in that, The sodium-ion battery satisfies one or more of the following conditions: (1) The slope capacity of the hard carbon material is 145 mAh / g-175 mAh / g, for example 150 mAh / g, 159 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, 175 mAh / g, preferably 150 mAh / g-170 mAh / g; (2) The negative electrode full cell is designed to have a capacity of 160 mAh / g-280 mAh / g, for example, 165 mAh / g, 170 mAh / g, 175 mAh / g, 180 mAh / g, 185 mAh / g, 190 mAh / g, 200 mAh / g, 210 mAh / g, 220 mAh / g, 230 mAh / g, 240 mAh / g, 250 mAh / g, 260 mAh / g, or 270 mAh / g, preferably 180 mAh / g-220 mAh / g; and, (3) The positive electrode full cell is designed to have a capacity of 96 mAh / g - 100 mAh / g, for example 98 mAh / g; and, (4) In the sodium-ion battery, the N / P ratio is designed to be 1.20-1.35, for example 1.2, 1.25 or 1.

3.

4. The sodium-ion battery as described in claim 1, characterized in that, The ramp capacity of the hard carbon material is obtained by half-cell testing of the negative electrode. Preferably, the half-cell is discharged at a current density of 0.1C. During discharge, the voltage corresponding to the ramp capacity is above 0.1V, and the voltage corresponding to the plateau capacity is between 0.1V and 0V. Further optimization involves obtaining the slope zone capacity using the following method: S1 uses a half-cell testing system to test the negative electrode. First, the half-cell is discharged to 0V at a current density of 0.1C 30mA / g to obtain the discharge capacity. After resting, it is charged to 2.0V at a current density of 0.1C to obtain the charging capacity. The charge and discharge voltage range is 0-2.0V. S2 According to step S1, the second cycle discharge and charge curve of the negative electrode can be obtained. During discharge, the voltage corresponding to the capacity in the ramp region is above 0.1V, and the voltage corresponding to the capacity in the plateau region is between 0.1V and 0V. Preferably, the preparation method of the half-cell includes the following steps: 95% hard carbon material, 1.5% Super P, and 3.5% CMC2200, where the percentages are the mass percentages of each component relative to the total amount of "hard carbon material, Super P, and CMC2200", deionized water is used as the solvent, the solid content is adjusted to 50%, and the mixture is ground in a planetary ball mill at 400 rpm for 30 min to obtain a slurry; the slurry is coated on copper foil and dried to obtain the half-cell; The hard carbon material was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1; the Super P was purchased from Temico; and the CMC2200 was purchased from DAICEL of South Korea.

5. The sodium-ion battery as described in claim 1, characterized in that, In the preparation method of the negative electrode sheet, the formulation of the negative electrode slurry includes: 92-96% of the hard carbon material, 0.5-2.5% of Super P, 0-1% of carbon black, 0.08-0.5% of CNT and 2.0-4.0% of PVDF, where the percentages are the mass percentages of each component relative to the total raw materials.

6. The sodium-ion battery as described in claim 5, characterized in that, In the negative electrode slurry, each component satisfies one or more of the following conditions: (1) In the negative electrode slurry, the amount of hard carbon material is 92.5-96%, for example 92.9%, 94.2%, 94.3%, 95.3%, 95.7% or 95.9%; (2) In the negative electrode slurry, the hard carbon material was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1; (3) In the negative electrode slurry, the amount of Super P is 0.8-2.2%, for example 1.0%, 1.5% or 2.0%; (4) In the negative electrode slurry, the specific surface area of ​​Super P is 54-66 m². 2 / g, for example 60m 2 / g; (5) In the negative electrode slurry, the amount of carbon black is 0.1-0.9%, for example 0.2%, 0.5% or 0.8%; (6) In the negative electrode slurry, the specific surface area of ​​the carbon black is 700-1400 m². 2 / g, for example 800m 2 / g、1200m 2 / g and 1400m 2 / g; (7) In the negative electrode slurry, the carbon black is selected from one or more of Ketjen Black EC-300J, EC600JD and ECP600JD; (8) In the negative electrode slurry, the amount of CNT is 0.09-0.4%, for example 0.1%, 0.2% or 0.3%; (9) In the negative electrode slurry, the CNTs were purchased from OCSIAL's oil-based single-walled carbon nanotubes; and, (10) In the negative electrode slurry, the amount of PVDF is 2.5-4.0%, for example 3%, 3.5% or 4%.

7. The sodium-ion battery as described in claim 1, characterized in that, In the preparation method of the positive electrode sheet, the formulation of the positive electrode slurry includes: sodium iron pyrophosphate NFPP 92-97%, Super P 1.0-2.2%, carbon black 0.1-1.0%, CNT 0.05-0.3% and PVDF 2.0-4.5%, where the percentages are the mass percentages of each component relative to the total raw materials; In the positive electrode slurry, each component preferably satisfies one or more of the following conditions: (1) In the positive electrode slurry, the amount of sodium iron pyrophosphate NFPP is 92.5-97%, for example 92.95%, 93.95%, 95.35% or 96.75%; (2) The sodium iron pyrophosphate NFPP was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNFP-1; (3) In the positive electrode slurry, the amount of Super P is 1.0-2.0%, for example 1.0%, 1.5% or 2.0%; (4) In the positive electrode slurry, the specific surface area of ​​Super P is 54-66 m². 2 / g, for example 60m 2 / g; (5) In the positive electrode slurry, the amount of carbon black is 0.1-0.9%, for example 0.2%, 0.5% or 0.8%; (6) In the positive electrode slurry, the carbon black is selected from Cabot MAX30 and / or Cabot MAX90; (7) In the positive electrode slurry, the amount of CNT is 0.05-0.28%, for example 0.05%, 0.15% or 0.25%; (8) In the positive electrode slurry, the CNTs were purchased from OCSIAL's oil-based single-walled carbon nanotubes; and, (9) In the positive electrode slurry, the amount of PVDF is 2.0-4.2%, for example 2%, 2.5%, 3.0% or 4.0%.

8. The sodium-ion battery as described in claim 1, characterized in that, In the preparation process of the negative electrode sheet in the sodium-ion battery, the negative electrode slurry used is any one of the following formulations: Formula 1: 95.9% hard carbon fiber, 1.0% Super P, 0.1% CNT, and 3% PVDF; Formula 2: 95.3% hard carbon fiber, 1.5% Super P, 0.2% CNT, and 3% PVDF; Formula 3: Hard carbon material 94.2%, Super P 1.5%, CNT 0.3%, and PVDF 4%; Formula 4: 95.7% hard carbon material, 1.0% Super P, 0.2% carbon black, 0.1% CNT, and 3% PVDF; Formula 5: Hard carbon material 94.3%, Super P 1.0%, carbon black 0.5%, CNT 0.2%, and PVDF 4.0%; Formula 6: Hard carbon material 92.9%, Super P 2.0%, Carbon black 0.8%, CNT 0.3%, PVDF 4.0%; The hard carbon material was purchased from Shenzhen Jiana Energy Technology Co., Ltd., model JNHCB-1, with a specific surface area of ​​approximately 60 m². 2 / g, CNTs were purchased from OCSIAL's oil-based single-walled carbon nanotubes, and the carbon black was EC600JD with a specific surface area of ​​1200m². 2 / g; And / or, in the preparation process of the positive electrode sheet in the sodium-ion battery, the positive electrode slurry used is any one of the following formulations: Formula 1: NFPP 96.75%, Super P 1.0%, Carbon Black 0.2%, CNT 0.05%, PVDF 2.0%; Formula 2: NFPP 95.35%, Super P 1.5%, Carbon Black 0.5%, CNT 0.15%, PVDF 2.5%; Formula 3: NFPP 93.95%, Super P 2.0%, Carbon Black 0.8%, CNT 0.25%, PVDF 3.0%; Formula 4: NFPP 92.95%, Super P 2.0%, Carbon Black 0.8%, CNT 0.25%, PVDF 4.0%; NFPP is sodium iron pyrophosphate, purchased from Shenzhen Jia Na Energy Technology Co., Ltd., model JNFP-1; Super P has a specific surface area of ​​approximately 60 m². 2 / g; CNTs are oil-based single-walled carbon nanotubes purchased from OCSIAL; carbon black is selected from Cabot MAX30 and / or Cabot MAX90.

9. The sodium-ion battery as described in claim 1, characterized in that, The sodium-ion battery satisfies one or more of the following conditions: (1) The charge-discharge curve of the hard carbon material half-cell in the second cycle is shown in Figure 1; (2) The ultra-high rate pulse voltage curve of the sodium-ion battery at 80% SOC is shown in Figure 2; (3) The voltage range and curve of the sodium-ion battery under normal operation are shown in Figure 3; and, (4) The full-cell cycle curve of the sodium-ion battery is shown in Figure 5.

10. An application of a sodium-ion battery as described in any one of claims 1-9 in the field of power tools or motor vehicles; The motor vehicle is preferably, but is not limited to, motor vehicles used in the fields of HEV, motorcycles, or construction machinery.

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