Hot pressing method for ion battery and battery

Abstract

The invention discloses a hot pressing method of an ion battery. The method comprises the following steps: preheating treatment; performing hot pressing treatment; in the hot-pressing treatment, the hot-pressing pressure P2, the hot-pressing temperature T2 and the hot-pressing time t2 are controlled to meet the condition that P2 * T2 * t2 * 10 <-3 > is more than 0.07 and less than 1. The battery hot-pressing method can obviously improve the discharge rate capability of the battery, so that the electrical property of the battery reaches a good state.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to an ion battery hot pressing method and a battery. Background Art

[0002] With the rise of the ion battery industry and the increasing demand for ion batteries year by year, consumers have also put forward higher requirements for the service life of ion batteries. At the same time, the market has also put forward development needs for ion batteries with higher discharge rate performance. In recent years, researchers have also been continuously optimizing the processing and manufacturing process of batteries to continuously improve the discharge rate performance of batteries and extend the service life of batteries.

[0003] Battery hot pressing is a very important process step in the battery manufacturing process. It improves battery performance by hot pressing and shaping the bare battery. Therefore, battery hot pressing is closely related to battery rate performance. However, the existing hot pressing process has very limited improvement on battery discharge rate performance. Therefore, it is urgent to effectively improve the hot pressing process to meet the battery processing and ensure the electrical performance of the later battery, so as to solve the problem of ion battery discharge rate performance. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a hot pressing method for an ion battery, which can significantly improve the discharge rate performance of the battery and make the electrical performance of the battery reach a good state.

[0005] Therefore, in the first aspect of the present invention, the present invention proposes a hot pressing method for a battery, comprising: preheating treatment; hot pressing treatment; during the hot pressing treatment, controlling the hot pressing pressure P2, hot pressing temperature T2 and hot pressing time t2 to satisfy: 0.07<P2×T2×t2×10 -3 <1.

[0006] Since the battery cell is relatively thick, there is a difference in heat conduction between the inner and outer layers of the battery cell, resulting in uneven heating. The first step of preheating treatment allows the temperature of the inner and outer layers of the battery cell to quickly tend to equilibrium, avoiding the inability of the colloid on the inner diaphragm to fully bond to the pole piece due to inconsistent temperatures between the inner and outer layers; secondly, the pole piece has a thermal expansion and contraction effect, and the preheating treatment can make the temperature of the inner and outer layers of the battery cell consistent, so that the pole piece and the diaphragm can expand to the maximum, allowing the pole piece and the diaphragm to fully contact, and at the same time, it can also effectively avoid inconsistent battery cell thickness caused by direct application of pressure. When the temperature inside and outside the battery cell tends to be consistent, the second step of hot pressing treatment is carried out, and the set pressure P2 is applied, which can make the hot pressing of the battery cell more uniform and the contact between the pole piece and the diaphragm more complete, thereby effectively reducing the interface impedance. At the same time, the second step of hot pressing satisfies 0.07<P×T×t×10 -3When the relationship is less than 1, the interface problem of the ion battery can be reduced and the battery electrical performance can reach a good state. Therefore, the hot pressing process can significantly improve the battery discharge rate performance and make the battery electrical performance reach a good state.

[0007] In some embodiments, during the preheating process, the control parameters satisfy at least one of the following:

[0008] (1) Hot pressing pressure P1 is 0;

[0009] (2) The hot pressing temperature T1 is 75°C to 100°C;

[0010] (3) Hot pressing time t1 is: 5min~10min.

[0011] In some embodiments, during the preheating process, the control parameters satisfy at least one of the following:

[0012] (a) Hot pressing pressure P1 is 0;

[0013] (b) hot pressing temperature T1 is 80°C to 95°C;

[0014] (c) The hot pressing time t1 is 6 min to 8 min.

[0015] In some embodiments, during the hot pressing process, the control parameters satisfy at least one of the following:

[0016] (i) hot pressing pressure P2 is 0.5MPa to 2MPa;

[0017] (ii) hot pressing temperature T2 is 80°C to 95°C;

[0018] (iii) The hot pressing time t2 is 2 min to 5 min.

[0019] In some embodiments, during the hot pressing process, the control parameters satisfy at least one of the following:

[0020] (A) hot pressing pressure P2 is 0.75MPa~1.5MPa;

[0021] (B) hot pressing temperature T2 is 85°C to 90°C;

[0022] (C) Hot pressing time t2 is 3min~4min.

[0023] In some embodiments, after the hot pressing treatment, a cooling treatment is further included; during the cooling treatment, the hot pressing pressure P3 is controlled to be greater than 0.

[0024] In some embodiments, during the temperature reduction process, the control parameters satisfy at least one of the following:

[0025] (I) hot pressing pressure P3≤0.5MPa;

[0026] (II) hot pressing temperature T3 is 25°C to 70°C;

[0027] (III) The hot pressing time t3 is 3 min to 7 min.

[0028] In some embodiments, during the temperature reduction process, the control parameters satisfy at least one of the following:

[0029] (a) hot pressing pressure P3 is 0.2MPa~0.3MPa;

[0030] (ii) hot pressing temperature T3 is 35°C to 55°C;

[0031] (iii) The hot pressing time t3 is 4 min to 6 min.

[0032] In some embodiments, the steps include:

[0033] Preheating treatment: hot pressing pressure P1 is 0; hot pressing temperature T1 is 75℃~100℃; hot pressing time t1 is 5min~10min;

[0034] Hot pressing treatment: hot pressing pressure P2 is 0.5MPa~2MPa; hot pressing temperature T2 is 80℃~95℃; hot pressing time t2 is 2min~5min;

[0035] Cooling treatment: hot pressing pressure P3 ≤ 0.5 MPa; hot pressing temperature T3 is 25°C ~ 70°C; hot pressing time t3 is 3min ~ 7min.

[0036] In a second aspect of the present invention, the present invention provides a method for preparing an ion battery, comprising the hot pressing method of the first aspect.

[0037] The hot pressing method can significantly improve the rate performance of the battery, thereby producing a battery with excellent electrical performance.

[0038] In the third aspect of the present invention, the present invention provides an ion battery, including the ion battery obtained by the preparation method of the second aspect, or including the ion battery processed by the hot pressing method of the first aspect.

[0039] As a result, the battery rate performance is improved and the battery electrical performance reaches a good state.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] (1) The battery hot pressing method of the present invention adopts a battery hot pressing method including preheating treatment, hot pressing treatment and cooling treatment. The preheating treatment can effectively avoid the problem of poor contact between the diaphragm and the pole piece caused by the inconsistent temperature of the inner and outer layers of the battery cell and the thermal expansion and contraction effect of the pole piece, and then the second step of hot pressing treatment is carried out. After the hot pressing treatment is completed, the third step of cooling treatment is carried out. Cooling will cause the pole piece and the diaphragm to shrink, and applying pressure while cooling can avoid interface problems caused by uneven shrinkage, and at the same time can improve the uneven thickness of the battery cell pole group, so that the flatness of the pole group is better. Therefore, the hot pressing method can reduce the interface problems of the battery, significantly improve the discharge rate performance of the battery, and make the battery electrical performance reach a good state.

[0042] (2) In the hot pressing process of the present invention, the hot pressing pressure P2, hot pressing temperature T2 and hot pressing time t2 are controlled to satisfy: 0.07<P2×T2×t2×10 -3 <1. It can further reduce the battery interface problem, significantly improve the battery discharge rate performance, and make the battery electrical performance reach a good state.

[0043] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0045] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0046] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0047] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0048] In a first aspect of an embodiment of the present invention, the present invention proposes a hot pressing method for an ion battery, comprising: preheating treatment; hot pressing treatment; during the hot pressing treatment, controlling the hot pressing pressure P2, hot pressing temperature T2 and hot pressing time t2 to satisfy: 0.07<P2×T2×t2×10 -3 <1.

[0049] Since the battery cell is thick, there is a difference in heat conduction between the inner and outer layers of the battery cell, resulting in uneven heating. The first step of preheating treatment allows the temperature of the inner and outer layers of the battery cell to quickly tend to equilibrium, avoiding the inability of the colloid on the inner diaphragm to fully bond to the pole piece due to inconsistent temperatures between the inner and outer layers; secondly, the pole piece has a thermal expansion and contraction effect, and the preheating treatment can make the temperature of the inner and outer layers of the battery cell consistent, so that the pole piece and the diaphragm can expand to the maximum, allowing the pole piece and the diaphragm to fully contact, and at the same time, it can also effectively avoid inconsistent battery cell thickness caused by direct application of pressure. When the temperature inside and outside the battery cell tends to be consistent, the second step of hot pressing treatment is carried out, and the set pressure P2 is applied, which can make the hot pressing of the battery cell more uniform and the contact between the pole piece and the diaphragm more complete, thereby effectively reducing the interface impedance. At the same time, the second step of hot pressing satisfies 0.07<P2×T2×t2×10 -3 When the relationship is less than 1, the interface problem of the ion battery can be reduced, and the battery electrical performance can reach a good state. Therefore, the hot pressing process can significantly reduce the battery DC resistance, improve the battery discharge rate performance, and optimize the battery electrical performance.

[0050] In some embodiments of the present invention, during the preheating process, the control parameters satisfy at least one of the following:

[0051] (1) Hot pressing pressure P1 is 0;

[0052] (2) The hot pressing temperature T1 is 75°C to 100°C;

[0053] (3) The hot pressing time t1 is 5 min to 10 min.

[0054] Since the battery cell is thick, there is a difference in heat conduction between the inner and outer layers of the battery cell. During the preheating process, under no pressure, the temperature T1 is first raised to 75℃~100℃, and the battery cell is preheated for 5min~10min, so that the temperature of the inner and outer layers of the battery cell tends to be balanced, and at the same time, the pole piece and the diaphragm are expanded to the maximum, so that the pole piece and the diaphragm are in more complete contact. When the inner and outer temperatures tend to be consistent, the hot pressing process is performed. In this way, the discharge rate performance of the battery can be significantly improved.

[0055] As an example, the hot pressing temperature T1 is 75° C., 80° C., 85° C., 90° C., 95° C., 100° C., etc.

[0056] As an example, the hot pressing time t1 is 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0057] In some embodiments of the present invention, during the preheating process, the control parameters satisfy at least one of the following:

[0058] (a) Hot pressing pressure P1 is 0;

[0059] (b) hot pressing temperature T1 is 80°C to 95°C;

[0060] (c) The hot pressing time t1 is 6 min to 8 min.

[0061] When the preferred hot pressing temperature is 80°C to 95°C and the preferred hot pressing time is 6min to 8min, the battery cell can be quickly and fully heated, reducing the temperature difference between the inner and outer layers of the battery cell, and the temperatures of the inner and outer layers tend to be balanced. At the same time, the pole piece and the diaphragm are expanded to the maximum, allowing the pole piece and the diaphragm to be in more complete contact, which is beneficial to the second step of hot pressing treatment.

[0062] As an example, the hot pressing temperature T1 is 80° C., 82° C., 84° C., 86° C., 88° C., 90° C., 92° C., 94° C., 95° C., etc.

[0063] As an example, the hot pressing time t1 is 6 min, 6.5 min, 7 min, 7.5 min, 8 min, etc.

[0064] In some embodiments of the present invention, during the hot pressing process, the control parameters satisfy at least one of the following:

[0065] (i) hot pressing pressure P2 is 0.5MPa to 2MPa;

[0066] (ii) hot pressing temperature T2 is 80°C to 95°C;

[0067] (iii) The hot pressing time t2 is 2 min to 5 min.

[0068] The magnitude of hot pressing pressure can directly affect the interface impedance between the positive and negative electrodes and the diaphragm inside the battery cell. When the hot pressing pressure P2 is 0.5MPa to 2MPa, the diaphragm and the positive and negative electrodes can have sufficient contact surface, reduce the interface impedance, and improve the battery cell rate performance. It will not cause the pressure cracking between the excessive area and the normal area of ​​the negative electrode of the battery cell, and at the same time ensure the good compaction density of the positive and negative electrodes without overpressure, so as to stabilize the long-term performance of the battery.

[0069] As an example, the hot pressing pressure P2 is 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, etc.

[0070] The hot pressing temperature can directly affect the porosity of the diaphragm, and has a direct or indirect impact on the contact between the positive and negative electrodes and the diaphragm, as well as the subsequent process of the battery cell. Since the diaphragm currently used is generally a polyethylene film, it has a low melting point and a certain porosity. When the hot pressing temperature T2 is 80℃~95℃, on the one hand, it can avoid the appearance of closed pores and thermal shrinkage of the diaphragm, avoid local film breakage or even melting, which may cause internal short circuits in the contact between the positive and negative electrodes, and make the positive and negative electrodes have good contact with the diaphragm, reducing the interface impedance; on the other hand, because the pole roll itself is relatively loose, when the hot pressing temperature T2 is 80℃~95℃, it can also further tighten the pole roll of the battery cell to reach the set thickness value, which is convenient for the smooth progress of subsequent processes. As a result, the discharge rate performance of the battery can be significantly improved.

[0071] As an example, the hot pressing temperature T2 is 80° C., 82° C., 84° C., 86° C., 88° C., 90° C., 92° C., 94° C., 95° C., etc.

[0072] When the hot pressing time t2 is 2 minutes to 5 minutes, the hot pressing effect is excellent, which not only reduces the interface impedance of the battery cell, but also enables the overall manufacturing process of the battery to proceed normally, ensuring production efficiency. Therefore, the discharge rate performance of the battery can be significantly improved.

[0073] As an example, the hot pressing time t2 is 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, etc.

[0074] In some embodiments of the present invention, during the hot pressing process, the control parameters satisfy at least one of the following:

[0075] (A) hot pressing pressure P2 is 0.75MPa~1.5MPa;

[0076] (B) hot pressing temperature T2 is 85°C to 90°C;

[0077] (C) Hot pressing time t2 is 3min~4min.

[0078] When the preferred hot pressing pressure P2 is 0.75MPa to 1.5MPa, the preferred hot pressing temperature T2 is 85℃ to 90℃, and the preferred hot pressing time t2 is 3min to 4min, the temperature of the inner and outer layers of the battery core can be further quickly balanced, and the diaphragm has sufficient contact surface with the positive and negative electrode sheets. As a result, the DC resistance of the battery can be significantly reduced, the rate performance can be improved, and the battery has excellent electrical performance.

[0079] As an example, the hot pressing pressure P2 is 0.75 MPa, 0.85 MPa, 0.95 MPa, 1.05 MPa, 1.15 MPa, 1.25 MPa, 1.35 MPa, 1.45 MPa, 1.5 MPa, etc.

[0080] As an example, the hot pressing temperature T2 is 85° C., 86° C., 87° C., 88° C., 89° C., 90° C., etc.

[0081] As an example, the hot pressing time t2 is 3 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min, 4 min, etc.

[0082] In some embodiments of the present invention, after the hot pressing treatment, a cooling treatment is further included; during the cooling treatment, the hot pressing pressure P3 is controlled to be greater than 0.

[0083] Applying pressure P3 after the temperature is lowered can avoid interface problems caused by uneven shrinkage of the electrode and the diaphragm during the cooling process, and can reduce the uneven thickness of the battery cell electrode group, making the electrode group flatter, which is beneficial to processes such as battery cell shelling.

[0084] In some embodiments of the present invention, during the cooling process, the control parameters satisfy at least one of the following:

[0085] (I) hot pressing pressure P3≤0.5MPa;

[0086] (II) hot pressing temperature T3 is 25°C to 70°C;

[0087] (III) The hot pressing time t3 is 3 min to 7 min.

[0088] The hot pressing pressure P3≤0.5Mpa, this pressure can avoid the interface problems caused by the uneven shrinkage of the pole piece and the diaphragm, and can reduce the uneven thickness of the battery cell pole group; the hot pressing temperature T3 is 25℃~70℃, and the hot pressing time t3 is 3min~7min. During this process, the temperature is lowered and kept warm for t3 minutes to avoid the huge temperature difference caused by the sudden temperature drop, which will cause the battery cell to have adverse effects on thermal expansion and contraction. In this way, the battery can have excellent electrical performance.

[0089] As an example, the hot pressing pressure P3 is 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, etc.

[0090] As an example, the hot pressing temperature T3 is 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0091] As an example, the hot pressing time t3 is 3 min, 4 min, 5 min, 6 min, 7 min, etc.

[0092] In some embodiments of the present invention, during the cooling process, the control parameters satisfy at least one of the following:

[0093] (a) hot pressing pressure P3 is 0.2MPa~0.3MPa;

[0094] (ii) hot pressing temperature T3 is 35°C to 55°C;

[0095] (iii) The hot pressing time t3 is 4 min to 6 min.

[0096] When the preferred hot pressing pressure P3 is 0.2MPa-0.3MPa, the preferred hot pressing temperature T3 is 35℃-55℃, and the preferred hot pressing time t3 is 4min-6min, the interface problems caused by the uneven shrinkage of the pole piece and the diaphragm can be further reduced, the uneven thickness of the battery cell pole group can be reduced, and the adverse effects caused by thermal expansion and contraction of the battery cell can be reduced. Thus, the battery can have excellent electrical performance.

[0097] As an example, the hot pressing pressure P3 is 0.2 MPa, 0.22 MPa, 0.24 MPa, 0.26 MPa, 0.28 MPa, 0.3 MPa, etc.

[0098] As an example, the hot pressing temperature T3 is 35° C., 40° C., 45° C., 50° C., 55° C., etc.

[0099] As an example, the hot pressing time t3 is 4 min, 4.5 min, 5 min, 5.5 min, 6 min, etc.

[0100] In some embodiments of the present invention, the steps include:

[0101] Preheating treatment: hot pressing pressure P1 is 0; hot pressing temperature T1 is 75℃~100℃; hot pressing time t1 is 5min~10min;

[0102] Hot pressing treatment: hot pressing pressure P2 is 0.5MPa~2MPa; hot pressing temperature T2 is 80℃~95℃; hot pressing time t2 is 2min~5min;

[0103] Cooling treatment: hot pressing pressure P3 ≤ 0.5 MPa; hot pressing temperature T3 is 25°C ~ 70°C; hot pressing time t3 is 3min ~ 7min.

[0104] During the battery hot pressing process, preheating treatment, hot pressing treatment and cooling treatment are carried out, and a three-step hot pressing process method is adopted. As a result, the battery's rate performance can be significantly improved and the electrical performance can be in a good state.

[0105] In a second aspect of the embodiments of the present invention, the present invention provides a method for preparing an ion battery, including the hot pressing method of the first aspect.

[0106] The hot pressing method can significantly improve the direct current resistance and rate performance of the battery, thereby producing a battery with excellent electrical performance.

[0107] In the third aspect of the embodiments of the present invention, the present invention provides an ion battery, which includes the ion battery obtained by the preparation method of the second aspect, or includes the ion battery processed by the hot pressing method of the first aspect.

[0108] Thereby, the DC resistance of the battery is reduced, the rate performance is improved, and the electrical performance of the battery reaches the optimum.

[0109] In some embodiments of the present invention, the battery further includes a positive electrode plate, which includes a positive current collector and a positive active material. The positive current collector can be a metal foil or a composite positive current collector, and the positive electrode material includes, but is not limited to, lithium iron phosphate material, LiCoO2 material, LiNi x Co y Mn z O2 (x + y + z = 1) material, lithium-rich manganese-based material (xLi2MnO3·(1 - x)LiMO2), lithium nickel manganate (LiNi 0.5 Mn 1.5 O4) material, and sodium nickel iron manganese oxide Na i Ni x Mn y A z B (1-x-y-z) O2 (0.8 < i ≤ 1.0, 0 < x ≤ 0.6, 0 < y ≤ 0.5, 0 < z ≤ 0.2), etc.

[0110] In some embodiments of the present invention, the battery further includes a negative electrode plate, which includes a negative current collector and a negative active material. The negative current collector can be a metal foil or a composite negative current collector, and the negative active material includes, but is not limited to, graphite negative electrode material, hard carbon negative electrode material, silicon oxide negative electrode material, and modified silicon oxide negative electrode material, etc.

[0111] In some embodiments of the present invention, the battery further includes an electrolyte, which includes a solvent, a lithium salt, and a functional additive. The solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, ethyl acetate, and ethyl propionate; the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium difluorobis(oxalato)phosphate; the additive includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, 1,3 - propane sultone, ethylene sulfite, vinylene carbonate, propylene sulfite, 1,4 - butane sultone, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, fluoroethylene carbonate, vinylene carbonate, fluoro vinylene carbonate, and lithium difluorophosphate.

[0112] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0113] Embodiment 1:

[0114] (a) Preparation of positive electrode for lithium-ion batteries

[0115] Lithium iron phosphate (positive electrode active material), carbon black Super-P (conductive agent), carbon nanotubes (conductive slurry), and vinylidene fluoride (binder) are mixed in a mass ratio of 96.5:1:0.5:2, and solvent N-methylpyrrolidone is added and stirred to dissolve to obtain positive electrode slurry. The positive electrode slurry is coated on a 12μm carbon-coated aluminum foil, and the positive electrode sheet is obtained through processes such as drying, rolling, and cutting.

[0116] (b) Preparation of negative electrode for lithium-ion batteries

[0117] Graphite material (negative electrode active material), carbon black Super-P (conductive agent), carboxymethyl cellulose CMC (binder) and styrene-butadiene rubber SBR (binder) are mixed in a mass ratio of 96:1:1.2:1.8, added into solvent pure water for dissolution and stirring to obtain negative electrode slurry, and the negative electrode slurry is coated on a 6μm copper foil, and the negative electrode sheet is obtained through processes such as drying, rolling, and cutting.

[0118] (c) Lithium-ion battery preparation

[0119] The positive and negative electrode sheets prepared in (a) and (b) are stacked with the separator (PE) to obtain the corresponding electrode rolls, and the electrode rolls are subjected to three-step hot pressing, i.e., preheating treatment, hot pressing treatment and cooling treatment in sequence, and the parameters are as follows:

[0120] (1) Preheating treatment: hot pressing pressure P1 is 0 MPa, hot pressing temperature T1 is 90 °C, and hot pressing time t1 is 7 min;

[0121] (2) Hot pressing treatment: the hot pressing pressure P2 is 1 MPa, the hot pressing temperature T2 is 85°C, and the hot pressing time t2 is 3.5 min;

[0122] (3) Cooling treatment: hot pressing pressure P3 is 0.25 MPa, hot pressing temperature T3 is 50°C, and hot pressing time t3 is 5 min;

[0123] After the hot pressing is completed, the battery cell is placed in the shell and baked, and then liquid is injected, formed, and capacity is divided to obtain a lithium-ion battery.

[0124] Embodiment 2:

[0125] The difference between Example 2 and Example 1: The hot pressing pressure P2 of Example 2 is 0.75 MPa.

[0126] Embodiment 3:

[0127] The difference between Example 3 and Example 1: The hot pressing pressure P2 of Example 3 is 0.5 MPa.

[0128] Embodiment 4:

[0129] The difference between Example 4 and Example 3 is that the hot pressing temperature T2 of Example 4 is 90°C.

[0130] Embodiment 5:

[0131] The difference between Example 5 and Example 1 is that Example 5 is a two-step hot pressing without a cooling treatment.

[0132] Embodiment 6:

[0133] The difference between Example 6 and Example 1: The hot pressing pressure T1 of Example 6 is 75°C.

[0134] Embodiment 7:

[0135] The difference between Example 7 and Example 1 is that the hot pressing pressure T1 of Example 7 is 100°C.

[0136] Embodiment 8:

[0137] The difference between Example 8 and Example 1 is that the hot pressing pressure T1 of Example 8 is 80°C.

[0138] Embodiment 9:

[0139] The difference between Example 9 and Example 1: The hot pressing pressure T1 of Example 9 is 95°C.

[0140] Embodiment 10:

[0141] The difference between Example 10 and Example 1: The hot pressing pressure P3 of Example 10 is 0.5 MPa.

[0142] Embodiment 11:

[0143] The difference between Example 11 and Example 1: The hot pressing pressure P3 of Example 11 is 0.3 MPa.

[0144] Embodiment 12:

[0145] The difference between Example 12 and Example 1: The hot pressing pressure P3 of Example 12 is 0.2 MPa.

[0146] Embodiment 13:

[0147] The difference between Example 13 and Example 1: The hot pressing pressure T3 of Example 13 is 25°C.

[0148] Embodiment 14:

[0149] The difference between Example 14 and Example 1: The hot pressing pressure T3 of Example 14 is 70°C.

[0150] Embodiment 15:

[0151] The difference between Example 15 and Example 1: The hot pressing pressure T3 of Example 15 is 35°C.

[0152] Embodiment 16:

[0153] The difference between Example 16 and Example 1: The hot pressing pressure T3 of Example 16 is 55°C.

[0154] Embodiment 17:

[0155] The difference between Example 17 and Example 3: The hot pressing temperature T2 of Example 17 is 88°C.

[0156] Embodiment 18:

[0157] (a) Preparation of positive electrode for sodium ion battery

[0158] Sodium nickel iron manganese oxide (sodium battery positive electrode active material), carbon black Super-P (conductive agent), carbon nanotubes (conductive slurry), and vinylidene fluoride (binder) are mixed in a mass ratio of 96.0:1.5:0.8:1.7, and solvent N-methylpyrrolidone is added and stirred to dissolve to obtain positive electrode slurry. The positive electrode slurry is coated on a 12μm aluminum foil, and the positive electrode sheet is obtained through processes such as drying, rolling, and cutting.

[0159] (b) Preparation of negative electrode for sodium ion battery

[0160] Hard carbon material (negative electrode active material), carbon black Super-P (conductive agent), carboxymethyl cellulose CMC (binder) and styrene-butadiene rubber SBR (binder) are mixed in a mass ratio of 95.0:1:1.5:2.5, added into solvent pure water for dissolution and stirring to obtain negative electrode slurry, and the negative electrode slurry is coated on 12μm aluminum foil, and the negative electrode sheet is obtained through processes such as drying, rolling and cutting.

[0161] (c) Preparation of sodium ion batteries

[0162] The positive and negative electrode sheets prepared in (a) and (b) are stacked with the separator (PE) to obtain the corresponding electrode rolls, and the electrode rolls are subjected to three-step hot pressing, i.e., preheating treatment, hot pressing treatment and cooling treatment in sequence, and the parameters are as follows:

[0163] (1) Preheating treatment: hot pressing pressure P1 is 0 MPa, hot pressing temperature T1 is 90 °C, and hot pressing time t1 is 7 min;

[0164] (2) Hot pressing treatment: the hot pressing pressure P2 is 1 MPa, the hot pressing temperature T2 is 85°C, and the hot pressing time t2 is 3.5 min;

[0165] (3) Cooling treatment: hot pressing pressure P3 is 0.25 MPa, hot pressing temperature T3 is 50°C, and hot pressing time t3 is 5 min;

[0166] After the hot pressing is completed, the battery cell is placed in the shell and baked, and then the liquid is injected, formed, and divided into different volumes to obtain a sodium ion battery.

[0167] Comparative Example 1:

[0168] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 is a one-step hot pressing without preheating treatment and cooling treatment.

[0169] Comparative Example 2:

[0170] The difference between Comparative Example 2 and Example 1: The hot pressing treatment step of Comparative Example 2: the hot pressing pressure P2 is 0.3 MPa, the hot pressing temperature T2 is 70°C, the hot pressing time t2 is 2 min, and the preheating treatment step and the cooling treatment step are consistent.

[0171] Comparative Example 3:

[0172] The difference between Comparative Example 3 and Example 1: The hot pressing treatment step of Comparative Example 3: the hot pressing pressure P2 is 2.0 MPa, the hot pressing temperature T2 is 100°C, the hot pressing time t2 is 10 min, and the preheating treatment step and the cooling treatment step are consistent.

[0173] Comparative Example 4:

[0174] The difference between Comparative Example 4 and Example 18: Comparative Example 4 is a one-step hot pressing without preheating and cooling treatment.

[0175] Battery performance test:

[0176] 1. Test Method

[0177] 1. Rate discharge capacity retention test

[0178] At room temperature of 25°C, the battery is charged to 3.65V at 1C constant current and constant voltage, and discharged to 2.0V at different rates (1C, 2C, 3C, 4C).

[0179] 2. High and low temperature discharge capacity retention rate test

[0180] 1C constant current and constant voltage charge to 3.65V, 1C discharge to 2.0V at different temperatures (25℃, 0℃), 1C discharge to 1.6V at different temperatures (-10℃, -20℃, -30℃).

[0181] 2. Test Results

[0182] 1. Rate discharge capacity retention test results

[0183] The test results of rate discharge capacity retention of the lithium ion batteries of all the embodiments and comparative examples are shown in Table 1.

[0184] Table 1 Battery rate discharge capacity retention test results

[0185]

[0186]

[0187] It can be seen from Table 1 that the battery rate discharge capacity retention rates of Examples 1-17 are significantly improved compared with Comparative Examples 1-3, and the battery rate discharge capacity retention rate of Example 18 is significantly improved compared with Comparative Example 4, indicating that the hot pressing method of the present invention can significantly improve the rate discharge performance of the battery.

[0188] 2. High and low temperature discharge capacity retention test results

[0189] The test results of high and low temperature discharge capacity retention rates of the lithium ion batteries of all embodiments and comparative examples are shown in Table 2.

[0190] Table 2 Battery high and low temperature discharge capacity retention test results

[0191]

[0192]

[0193] It can be seen from Table 2 that the high and low temperature discharge capacity retention rates of the batteries of Examples 1-17 are significantly improved compared with those of Comparative Examples 1-3, and the high and low temperature discharge capacity retention rates of the batteries of Example 18 are significantly improved compared with those of Comparative Example 4, indicating that the hot pressing method of the present invention can significantly improve the discharge performance of the battery in a low temperature environment, which is beneficial to the long-term stability of the battery.

[0194] This indicates that the battery hot pressing method of the present invention can significantly improve the battery discharge rate performance and bring the battery's electrical performance to a good state.

[0195] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0196] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A hot pressing method for an ion battery, characterized in that: include: Preheat treatment; Heat pressing treatment; During the hot pressing process, the hot pressing pressure P2, hot pressing temperature T2 and hot pressing time t2 are controlled to satisfy: 0.07<P2×T2×t2×10 -3 <1.

2. The hot pressing method according to claim 1, characterized in that: In the preheating process, the control parameters satisfy at least one of the following: (1) Hot pressing pressure P1 is 0; (2) The hot pressing temperature T1 is 75°C to 100°C; (3) The hot pressing time t1 is 5 min to 10 min.

3. The hot pressing method according to claim 1, characterized in that: In the preheating process, the control parameters satisfy at least one of the following: (a) Hot pressing pressure P1 is 0; (b) hot pressing temperature T1 is 80°C to 95°C; (c) The hot pressing time t1 is 6 min to 8 min.

4. The hot pressing method according to claim 1, characterized in that: During the hot pressing treatment, the control parameters satisfy at least one of the following: (i) hot pressing pressure P2 is 0.5MPa to 2MPa; (ii) hot pressing temperature T2 is 80°C to 95°C; (iii) The hot pressing time t2 is 2 min to 5 min.

5. The hot pressing method according to claim 1, characterized in that: During the hot pressing treatment, the control parameters satisfy at least one of the following: (A) hot pressing pressure P2 is 0.75MPa~1.5MPa; (B) hot pressing temperature T2 is 85°C to 90°C; (C) Hot pressing time t2 is 3min~4min.

6. The hot pressing method according to any one of claims 1 to 5, characterized in that: After the hot pressing treatment, a cooling treatment is also included; during the cooling treatment, the hot pressing pressure P3 is controlled to be greater than 0.

7. The hot pressing method according to claim 6, characterized in that: In the cooling process, the control parameters satisfy at least one of the following: (I) hot pressing pressure P3≤0.5MPa; (II) hot pressing temperature T3 is 25°C to 70°C; (III) The hot pressing time t3 is 3 min to 7 min.

8. The hot pressing method according to claim 6, characterized in that: In the cooling process, the control parameters satisfy at least one of the following: (a) hot pressing pressure P3 is 0.2MPa~0.3MPa; (ii) hot pressing temperature T3 is 35°C to 55°C; (iii) The hot pressing time t3 is 4 min to 6 min.

9. The hot pressing method according to claim 1, characterized in that: Includes steps: Preheating treatment: hot pressing pressure P1 is 0; hot pressing temperature T1 is 75℃~100℃; hot pressing time t1 is 5min~10min; Hot pressing treatment: hot pressing pressure P2 is 0.5MPa~2MPa; hot pressing temperature T2 is 80℃~95℃; hot pressing time t2 is 2min~5min; Cooling treatment: hot pressing pressure P3 ≤ 0.5 MPa; hot pressing temperature T3 is 25°C ~ 70°C; hot pressing time t3 is 3min ~ 7min.

10. A method for preparing an ion battery, characterized in that: The hot pressing method comprising any one of claims 1 to 9.

11. An ion battery, characterized in that: An ion battery obtained by the preparation method according to claim 10, or an ion battery treated by the hot pressing method according to any one of claims 1 to 9.

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