Sodium ion battery, negative pole piece and electric equipment

Abstract

The invention provides a sodium ion battery, a negative electrode plate and electric equipment, the sodium ion battery comprises a negative electrode material layer, and the negative electrode material layer comprises a negative electrode material; the negative electrode material and a metal sodium sheet are prepared into a button type half cell, 0.1 C constant current discharge is carried out on the button type half cell at 20-30 DEG C, the voltage of the button type half cell at 60% DOD is recorded as V1, the voltage of the button type half cell at 90% DOD is recorded as V2, and V2-V1 is larger than or equal to 0 and smaller than or equal to 0.66 V. The sodium ion battery provided by the invention has improved low-temperature discharge and cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a sodium ion battery, a negative electrode sheet and an electrical device. Background Art

[0002] Sodium-ion batteries have attracted widespread attention due to their abundant sodium reserves, low price, and uniform distribution. They may replace lithium-ion batteries in certain areas in the future and are expected to be used in portable electronic devices, electric vehicles, hybrid vehicles, etc. However, current sodium-ion batteries often have problems with low-temperature discharge and poor cycle performance. Summary of the invention

[0003] Based on this, the present application provides a sodium ion battery, a negative electrode plate and an electrical device, which can enable the sodium ion battery to obtain improved low-temperature discharge and cycle performance.

[0004] A first aspect of the present application provides a sodium ion battery, comprising a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode material;

[0005] The negative electrode material and the sodium metal sheet are prepared into a button half-cell, and the button half-cell is discharged at a constant current of 0.1C at 20°C~30°C. The voltage of the button half-cell at 60%DOD is recorded as V1, and the voltage at 90%DOD is recorded as V2, satisfying: 0≤V2-V1≤0.66V.

[0006] In some implementations of the present application, the following condition is satisfied: 0.59V≤V2-V1≤0.66V.

[0007] In some embodiments of the present application, the negative electrode material includes hard carbon.

[0008] In some embodiments of the present application, the negative electrode material layer further comprises a negative electrode conductive agent and / or a negative electrode binder;

[0009] Optionally, the weight ratio of the negative electrode material, the negative electrode conductive agent and the negative electrode binder is (90% to 99%): (0.5% to 5%): (0.5% to 5%);

[0010] Optionally, the negative electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black, Ketjen black and graphene;

[0011] Optionally, the negative electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene and polyolefin compounds.

[0012] In some embodiments of the present application, a positive electrode material layer is further included, wherein the positive electrode material layer contains a positive electrode material, and an optional positive electrode conductor and / or an optional positive electrode binder.

[0013] In some embodiments of the present application, the positive electrode material layer comprises a positive electrode material, a positive electrode conductor and a positive electrode binder, and the weight ratio of the positive electrode material, the positive electrode conductor and the positive electrode binder is (90%~98%):(1%~5%):(1%~5%).

[0014] In some embodiments of the present application, one or more of the following conditions are met:

[0015] (1) The positive electrode material comprises a layered oxide;

[0016] Optionally, the layered oxide satisfies the chemical formula Na x Ni y1 Fe y2 Mn (0.4-y3) O2, where 0 <x≤1,0.2≤y1≤0.4,0.2≤y2≤0.4,0.05<y3<0.30;

[0017] (2) The positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black, Ketjen black and graphene;

[0018] (3) The positive electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene and polyolefin compounds.

[0019] A second aspect of the present application provides a negative electrode plate, comprising a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode material;

[0020] The negative electrode material and the sodium metal sheet are prepared into a button half-cell, and the button half-cell is discharged at a constant current of 0.1C at 20°C~30°C. The voltage of the button half-cell at 60%DOD is recorded as V1, and the voltage at 90%DOD is recorded as V2, satisfying: 0≤V2-V1≤0.66V.

[0021] In some embodiments of the present application, the negative electrode plate is the negative electrode plate in the sodium ion battery described in the first aspect of the present application.

[0022] The third aspect of the present application provides an electrical device, comprising the sodium ion battery described in the first aspect of the present application.

[0023] The electrical equipment of the present application includes the sodium ion battery provided in the present application, and thus has at least the same advantages as the sodium ion battery.

[0024] The sodium ion battery provided in the present application, by restricting the negative electrode material so that it satisfies the above conditions (0≤V2-V1≤0.66V), can limit the rate of change of the discharge voltage of the negative electrode material in the slope area, so that the rate of decrease of the discharge voltage in the slope area can be reduced, thereby facilitating the improvement of the overall discharge voltage platform of the battery, so that it can effectively cope with low-temperature discharge, large-rate discharge capacity attenuation, and insufficient terminal discharge power, and improve the low-temperature discharge and cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an example diagram of the SOC charge and discharge curve of a button half-cell with a slope area. DETAILED DESCRIPTION

[0026] In order to facilitate understanding of the present application, the present application will be described more comprehensively below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0027] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. It should be noted that, unless otherwise specified, the term "and / or" used herein includes any and all combinations of one or more related listed items, and "above" and "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is more than two.

[0029] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0030] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0031] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0032] In traditional sodium-ion batteries, the negative electrode material is usually made of carbon-based materials, especially amorphous hard carbon. However, due to its own characteristics, hard carbon materials are usually prone to cause a slope region in the low-power 0%~40% SOC (State-of-Charge) range when the battery is discharged. This slope region not only contributes little to the battery capacity, but also is usually reflected in the battery discharge curve as a rapid drop in voltage (see Figure 1 This will result in a lower overall discharge voltage platform for the battery, which is not conducive to the application of the battery in low-temperature discharge, high-rate discharge, and terminal discharge (such as start-stop power supply) and other scenarios.

[0033] Based on this, the present application proposes a sodium ion battery, which reduces the rate of change of the discharge voltage in the slope zone by limiting the rate of change of the discharge voltage of the negative electrode material in the low SOC state (corresponding to the slope zone) during discharge, thereby improving the overall discharge voltage platform of the battery, and can effectively cope with low-temperature discharge, large-rate discharge capacity attenuation, and insufficient terminal discharge power, thereby improving the low-temperature discharge and cycle performance of the battery.

[0034] In a first aspect, the present application provides a sodium ion battery, comprising a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode material;

[0035] The negative electrode material and the sodium metal sheet are prepared into a button half-cell, and the button half-cell is discharged at a constant current of 0.1C at 20°C~30°C. The voltage of the button half-cell at 60%DOD is recorded as V1, and the voltage at 90%DOD is recorded as V2, satisfying: 0≤V2-V1≤0.66V.

[0036] The sodium ion battery provided in the present application, by restricting the negative electrode material so that it satisfies the above conditions (0≤V2-V1≤0.66V), can limit the rate of change of the discharge voltage of the negative electrode material in the slope area, so that the rate of decrease of the discharge voltage in the slope area can be reduced, thereby facilitating the improvement of the overall discharge voltage platform of the battery, so that it can effectively cope with low-temperature discharge, large-rate discharge capacity attenuation, and insufficient terminal discharge power, thereby improving the low-temperature discharge and cycle performance of the battery.

[0037] It should be noted that the "DOD" mentioned in this application refers to the depth of discharge, which refers to the percentage of the amount of electricity discharged by the battery during a discharge process to the rated capacity of the battery.

[0038] It should be noted that the button half-cell described in the present application includes a negative electrode, a positive electrode, a separator and an electrolyte, and the separator is arranged between the negative electrode and the positive electrode; wherein, the negative electrode includes a negative electrode collector and a negative electrode film layer arranged on opposite sides of the negative electrode collector, the positive electrode is a metal sodium sheet with a thickness of 0.3mm~0.8mm, and the separator can be a polyolefin separator or a glass fiber separator with a thickness of 10μm~30μm and a porosity of 30%~60%.

[0039] In some embodiments, V2-V1 may be 0, 0.1 V, 0.15 V, 0.2 V, 0.25 V, 0.3 V, 0.35 V, 0.4 V, 0.45 V, 0.5 V, 0.55 V, 0.6 V, 0.66 V or any range thereof.

[0040] In some embodiments, the negative electrode film layer includes a negative electrode material, a negative electrode conductor and a negative electrode binder, and the mass ratio of the three is (90%~99%):(0.5%~5%):(0.5%~5%), and its thickness on a single side of the negative electrode current collector is 50μm~200μm.

[0041] In some embodiments, the electrolyte includes a solvent and a sodium salt, wherein the solvent includes ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC), and the volume ratio of the three is 1:(0.5~1):(1~2); the sodium salt includes NaPF6 and / or NaClO4, and its concentration in the electrolyte is 0.8mol / L~1.2mol / L.

[0042] In some embodiments, the negative electrode material includes hard carbon.

[0043] In some embodiments, the negative electrode material layer further includes a negative electrode conductor and / or a negative electrode binder.

[0044] In some embodiments, the weight ratio of the negative electrode material, the negative electrode conductor and the negative electrode binder is (90%~99%): (0.5%~5%): (0.5%~5%).

[0045] In some embodiments, the negative electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, acetylene black (SP), Ketjen black, and graphene.

[0046] In some embodiments, the negative electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride (PVDF), polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene, and polyolefin compounds.

[0047] In some embodiments, a positive electrode material layer is further included, wherein the positive electrode material layer includes a positive electrode material, and an optional positive electrode conductor and / or an optional positive electrode binder.

[0048] In some embodiments, the positive electrode material layer comprises a positive electrode material, a positive electrode conductor and a positive electrode binder, and the weight ratio of the positive electrode material, the positive electrode conductor and the positive electrode binder is (90%~98%):(1%~5%):(1%~5%).

[0049] In some embodiments, the positive electrode material includes a layered oxide. Combining the negative electrode material that meets the above conditions of the present application with the layered oxide is beneficial to the discharge platform of the layered oxide, which is beneficial to the improvement of the discharge voltage platform of the battery as a whole and the improvement of low temperature cycle performance.

[0050] In some embodiments, the layered oxide satisfies the chemical formula Na x Ni y1 Fe y2 Mn (0.4-y3) O2, where 0 < x ≤ 1, 0.2 ≤ y1 ≤ 0.4, 0.2 ≤ y2 ≤ 0.4, 0.05 < y3 < 0.30. Matching the negative electrode material that meets the aforementioned conditions of this application with this layered oxide is beneficial to the discharge platform of the positive electrode, thus facilitating the further improvement of the overall discharge voltage platform of the battery and the further improvement of the low-temperature cycle performance.

[0051] In some embodiments, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black, Ketjen black, and graphene.

[0052] In some embodiments, the positive electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile rubber, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene, and polyolefin compounds.

[0053] In a second aspect, the present application provides a negative electrode sheet, including a negative electrode material layer, and the negative electrode material layer contains a negative electrode material;

[0054] The negative electrode material and a sodium metal sheet are prepared into a coin-type half-cell, and at 20°C to 30°C, the coin-type half-cell is subjected to constant current discharge at 0.1C. The voltage of the coin-type half-cell at 60% DOD is denoted as V1, and the voltage at 90% DOD is denoted as V2, satisfying: 0 ≤ V2 - V1 ≤ 0.66V.

[0055] In some embodiments, the negative electrode sheet is the negative electrode sheet in the sodium ion battery according to the first aspect of the present application.

[0056] The negative electrode sheet of the second aspect of the present application has the same function in the battery as that of the first aspect of the present application, and will not be elaborated here.

[0057] In a third aspect, the present application provides an electrical device, including the sodium ion battery according to the first aspect of the present application.

[0058] In some embodiments, the type of the electrical device is not particularly limited, and it can be any electronic device known in the prior art. For example, the electrical device may include, but is not limited to, power tools, electric vehicles, laptop computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, etc.

[0059] Examples

[0060] The following are specific examples, which more specifically describe the contents disclosed in this application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0061] Example 1

[0062] (1) Layered oxide positive electrode NaNi 0.33 Fe 0.33 Mn 0.33 O2, conductive agent, and binder PVDF were homogenized in N-methylpyrrolidone at a mass ratio of 95%:(1.5%CNTs+1.5%SP):4% to prepare positive electrode slurry, and the positive electrode slurry was coated on the opposite sides of the aluminum foil, and the positive electrode sheet was obtained after drying, roller baking, and slicing, wherein the single-sided coating surface density of the positive electrode sheet was 160mg / m 2 The compaction density after roller pressing is 1.6g / cm 3 .

[0063] (2) Hard carbon, conductive carbon black and binder are homogenized in a mass ratio of 96%:1%:3% to prepare negative electrode slurry, and the negative electrode slurry is coated on the opposite sides of the copper foil. After drying, roller pressing and baking, and slicing, a negative electrode sheet is obtained; the single-sided coating surface density of the negative electrode sheet is 80g / m 2 The compaction density after roller pressing is 0.95g / cm 3 .

[0064] (3) The positive electrode sheet, separator and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound into a square bare cell, loaded with aluminum plastic film, and then injected with non-aqueous electrolyte, sealed, and after standing, hot and cold pressing, and chemical formation, a sodium ion battery is obtained; wherein the solvent in the non-aqueous electrolyte includes PC (propylene carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate), the volume ratio of the three is 1:1:1, and the solute is sodium salt NaPF6, and its molar concentration is 1 mol / L.

[0065] Embodiment 2~4

[0066] The preparation method is similar to that of Example 1, with the main difference being that in step (2), the hard carbon in Example 1 is replaced by a different hard carbon of equal mass. The replaced hard carbon can enable the button half-cell to exhibit different discharge voltage characteristics during 0.1C constant current discharge, as shown in Table 1 below.

[0067] Example 5

[0068] The preparation method is similar to that of Example 1, with the main difference being that in step (1), the layered oxide positive electrode is replaced by an equal mass of polyanionic positive electrode NaFePO4.

[0069] Comparative Examples 1 to 3

[0070] The preparation method is similar to that of Example 1, with the main difference being that in step (2), the hard carbon in Example 1 is replaced by a different hard carbon of equal mass. The replaced hard carbon can enable the button half-cell to exhibit different discharge voltage characteristics during 0.1C constant current discharge, as shown in Table 1 below.

[0071] The sodium ion batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to relevant performance tests, and the test results are shown in Table 1 below.

[0072] Among them, the test conditions or test standards for each performance test item are as follows:

[0073] (1) Low temperature cycle performance test

[0074] In a 25℃ environment, the sodium ion battery was placed for 10 minutes, charged to 3.95V at 0.25C constant current and constant voltage, and the charging capacity was recorded as C1; then, in a -20℃ environment, it was placed for 300 minutes, discharged to 1.5V at 0.25C constant current, and the discharge capacity was recorded as C2; -20℃ capacity retention rate = C2 / C1*100%.

[0075] Table 1

[0076]

[0077] It can be seen from Table 1 above that compared with Comparative Examples 1 to 3, when Examples 1 to 5 satisfy 0≤V2-V1≤0.66V, the -20°C capacity retention rate is significantly improved.

[0078] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A sodium ion battery, characterized in that: comprising a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode material; The negative electrode material and the sodium metal sheet are prepared into a button half-cell, and the button half-cell is discharged at a constant current of 0.1C at 20°C~30°C. The voltage of the button half-cell at 60%DOD is recorded as V1, and the voltage at 90%DOD is recorded as V2, satisfying: 0≤V2-V1≤0.66V.

2. The sodium ion battery according to claim 1, characterized in that The negative electrode material includes hard carbon.

3. The sodium ion battery according to claim 1 or 2, characterized in that: The negative electrode material layer further includes a negative electrode conductor and / or a negative electrode binder.

4. The sodium ion battery according to claim 3, characterized in that: One or more of the following conditions are met: (1) The weight ratio of the negative electrode material, the negative electrode conductive agent and the negative electrode binder is (90%~99%):(0.5%~5%):(0.5%~5%); (2) The negative electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black, Ketjen black and graphene; (3) The negative electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene and polyolefin compounds.

5. The sodium ion battery according to claim 1 or 2, characterized in that: The device further comprises a positive electrode material layer, wherein the positive electrode material layer comprises a positive electrode material, and optionally a positive electrode conductor and / or optionally a positive electrode binder.

6. The sodium ion battery according to claim 5, characterized in that: The positive electrode material layer comprises a positive electrode material, a positive electrode conductor and a positive electrode binder, and the weight ratio of the positive electrode material, the positive electrode conductor and the positive electrode binder is (90%~98%):(1%~5%):(1%~5%).

7. The sodium ion battery according to claim 5 or 6, characterized in that: One or more of the following conditions are met: (1) The positive electrode material comprises a layered oxide; Optionally, the layered oxide satisfies the chemical formula Na x Ni y1 Fe y2 Mn (0.4-y3) O2, where 0 <x≤1,0.2≤y1≤0.4,0.2≤y2≤0.4,0.05<y3<0.30; (2) The positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, carbon fibers, acetylene black, Ketjen black and graphene; (3) The positive electrode binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylonitrile, hydrogenated nitrile, polyvinylidene fluoride, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene and polyolefin compounds.

8. A negative electrode plate, characterized in that: comprising a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode material; The negative electrode material and the sodium metal sheet are prepared into a button half-cell, and the button half-cell is discharged at a constant current of 0.1C at 20°C~30°C. The voltage of the button half-cell at 60%DOD is recorded as V1, and the voltage at 90%DOD is recorded as V2, satisfying: 0≤V2-V1≤0.66V.

9. The negative electrode sheet according to claim 8, characterized in that: The negative electrode plate is the negative electrode plate in the sodium ion battery according to any one of claims 2 to 7.

10. An electrical device, characterized in that: A sodium ion battery comprising the sodium ion battery according to any one of claims 1 to 7.

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