阅读说明：本技术 提升锂电芯隔膜粘接力的设备 (Equipment for improving bonding force of lithium cell diaphragm ) 是由 杨帆 翟艳云 张健 谢孔岩 刘芬 杨锦帅 崔亚楠 彭冲 于 2021-07-30 设计创作，主要内容包括：本发明公开一种提升锂电芯隔膜粘接力的设备,通过对锂电芯的其中一个极片接入电流,此时该极片相当于一个发热电阻,会自身发热,热量会迅速传递至隔膜和另一极片,由于加热位置在锂电芯内部,能快速对锂电芯进行均匀加热,而且温度调节简单可控；同时,在压板的压力作用下,隔膜上的粘结剂会与正负极片表面的粘接剂之间发生粘接,隔膜的粘接效果在锂电芯内外侧保持一致,改善了现有工艺内外部粘接力存在差异的问题。(The invention discloses equipment for improving the bonding force of a lithium battery cell diaphragm, wherein current is connected to one of the pole pieces of the lithium battery cell, the pole piece is equivalent to a heating resistor and can generate heat by itself, the heat can be rapidly transferred to the diaphragm and the other pole piece, and the lithium battery cell can be rapidly and uniformly heated due to the fact that the heating position is arranged in the lithium battery cell, and the temperature adjustment is simple and controllable; meanwhile, under the pressure action of the pressing plate, the adhesive on the diaphragm can be adhered with the adhesives on the surfaces of the positive and negative pole pieces, the adhering effect of the diaphragm is kept consistent inside and outside the lithium battery cell, and the problem that the inside and outside adhesive force is different in the prior art is solved.)

1. The equipment for improving the diaphragm bonding force of the lithium battery cell comprises a winding body, a first tab and a second tab, wherein the winding body consists of the first tab, the diaphragm and the second tab; the first pole piece and the second pole piece are opposite in polarity, and the first pole piece is provided with a conductive part exposed to the outer layer of the winding body; the apparatus includes a platen assembly having a first platen and a second platen that provide relative pressure to the lithium cell; the device is characterized in that the first pressing plate and/or the second pressing plate are provided with: the first connecting piece is used for being electrically connected with the first electrode lug of the lithium battery cell, and the third connecting piece is used for being electrically connected with the conductive part; the equipment also comprises a heating power supply with two poles respectively connected with the first connecting piece and the third connecting piece.

2. The apparatus of claim 1, wherein the first and/or second platens have a second connector disposed thereon for electrically connecting to the second pole ear; the device also comprises a Hi-pot test power supply with two poles respectively connected with the first connecting piece and the second connecting piece.

3. The apparatus according to claim 2, wherein at least one lithium cell placement location is provided between the first pressing plate and the second pressing plate, and corresponding first connecting member, second connecting member and third connecting member are provided on the first pressing plate and/or the second pressing plate corresponding to each lithium cell placement location.

4. The apparatus of claim 2 or 3, wherein the third connector is an electrically conductive contact plate for contacting and mating with the electrically conductive portion.

5. The apparatus of claim 4, wherein the conductive contact plate has a length and a width that are both greater than a length and a width of the jelly roll.

6. The apparatus of claim 4, wherein the first and second connectors are conductive contacts for contacting and mating with the first and second tabs, respectively.

7. The apparatus of claim 6, wherein the first, second and third connectors protrude from a surface of the first and/or second platen; the protruding heights of the first connecting piece and the second connecting piece are higher than those of the third connecting piece.

8. The apparatus of claim 1, further comprising a controllable pressure drive mechanism for driving the first platen and the second platen in relative motion.

9. The apparatus of claim 1, wherein the heating power source provides a selectable current of 0.5-40A for electrically heating the lithium cell coupled between the first and third connectors to 70-120 ℃.

10. The apparatus of claim 2, wherein the Hi-pot test power supply has a test voltage of 30V to 200V.

Technical Field

The invention belongs to the technical field of battery manufacturing, and particularly relates to equipment for improving the bonding force of a lithium battery core diaphragm.

Background

At present, lithium ion batteries (lithium batteries for short) are becoming indispensable components in production and life, research and improvement aiming at the lithium batteries are continuous, and the improvement mainly focuses on the aspects of quick charging, quick discharging, light weight, high density, safety and the like.

The lithium battery mainly comprises a positive pole piece, a negative pole piece, a diaphragm, electrolyte and a shell, wherein the diaphragm of the lithium battery mainly plays a role in blocking direct contact short circuit between the positive pole and the negative pole, allowing electrolyte ions to pass through and bonding the electrolyte ions with the positive pole and the negative pole to increase the hardness of the lithium battery. In the existing process of manufacturing the winding type soft package lithium ion battery, the bonding between the diaphragm and the positive and negative electrodes occurs in the formation stage after the liquid injection of the battery core. At this stage, the lithium ion battery is charged and discharged and hot-pressed, the battery cell is activated by charging and discharging, and an SEI film is formed on the surface of the negative electrode, so that the performance of the battery is more stable. Under the action of hot pressing, the adhesive on the surface of the diaphragm is bonded with the adhesive on the surfaces of the positive and negative pole pieces, so that the thickness of the battery cell is reduced, and the hardness is increased.

In the current conventional formation technology, heat is provided by the hot plate (or called hot pressboard) subassembly of putting lithium cell electricity core (lithium cell), adds soft rubber pad in order to increase electric core roughness usually between hot plate subassembly and the lithium cell, leads to the thermal conductivity poor. In the whole formation process, the equipment needs to be heated continuously, the heat quantity borne by the lithium ion battery is gradually reduced from outside to inside, and the difference exists between the inside and outside of the diaphragm and the adhesiveness between the anode and the cathode. Meanwhile, in order to ensure the bonding effect, the prior art generally adopts higher temperature and pressure, which easily causes the problems of more electrolyte secondary reactions, thickened SEI film, increased internal resistance, cell displacement and the like in formation.

Disclosure of Invention

The invention aims to provide equipment capable of effectively improving the adhesion of a lithium battery cell diaphragm. The technical scheme adopted by the invention is as follows:

the equipment for improving the diaphragm bonding force of the lithium battery cell comprises a winding body, a first tab and a second tab, wherein the winding body consists of the first tab, the diaphragm and the second tab; the first pole piece and the second pole piece are opposite in polarity, and the first pole piece is provided with a conductive part exposed to the outer layer of the winding body; the apparatus includes a platen assembly having a first platen and a second platen that provide relative pressure to the lithium cell; the device is characterized in that the first pressing plate and/or the second pressing plate are provided with: the first connecting piece is used for being electrically connected with the first electrode lug of the lithium battery cell, and the third connecting piece is used for being electrically connected with the conductive part; the equipment also comprises a heating power supply with two poles respectively connected with the first connecting piece and the third connecting piece.

Furthermore, a second connecting piece used for being electrically connected with the second pole lug is arranged on the first pressure plate and/or the second pressure plate; the device also comprises a Hi-pot test power supply with two poles respectively connected with the first connecting piece and the second connecting piece.

Specifically, be provided with at least one lithium cell between first clamp plate and second clamp plate and place the position, correspond every lithium cell and place the position set up the correspondence on first clamp plate and or the second clamp plate first connecting piece, second connecting piece and third connecting piece.

Specifically, the third connecting piece is a conductive contact plate for contact-fitting with the conductive part.

Specifically, the length and the width of the conductive contact plate are both larger than those of the winding body.

Specifically, the first connecting piece and the second connecting piece are respectively conductive contacts for contacting and matching with the first tab and the second tab.

Specifically, the first connecting piece, the second connecting piece and the third connecting piece protrude out of the surfaces of the first pressing plate and the second pressing plate; the protruding heights of the first connecting piece and the second connecting piece are higher than those of the third connecting piece.

Further, the device also comprises a controllable pressure driving mechanism which drives the first pressing plate and the second pressing plate to move relatively.

Specifically, the heating power supply provides an optional current of 0.5-40A for electrically heating the lithium battery cell connected between the first and third connectors to 70-120 ℃.

Specifically, the testing voltage of the Hi-pot testing power supply is 30V-200V.

According to the invention, current is switched on one of the pole pieces (the pole piece positioned on the outer layer of the winding body, such as a positive pole piece) of the lithium battery cell, at the moment, the pole piece is equivalent to a heating resistor, and the power P (I) according to the heat production is equal to I²R, the pole piece can generate heat by itself, the heat can be quickly transferred to the diaphragm and the other pole piece, the lithium battery cell can be quickly and uniformly heated due to the fact that the heating position is located inside the lithium battery cell, and temperature adjustment is simple and controllable; meanwhile, under the pressure action of the pressing plate, the adhesive on the diaphragm can be adhered with the adhesives on the surfaces of the positive and negative pole pieces, the adhesion effect of the diaphragm is kept consistent on the inner side and the outer side of the lithium battery cell, and the problem of difference of the internal and external adhesion forces in the prior art is solved; in addition, the lithium battery core is shaped by hot pressing once, so that the temperature, pressure and time required by the subsequent formation process can be reduced, the occurrence of side reactions in the formation is reduced, the first effect is improved, the difficulty in subsequent packaging can be reduced, and the thickness of the battery core is effectively reduced.

Drawings

Fig. 1 is a perspective view of an apparatus provided in an embodiment of the present invention.

Fig. 2 is a front view of an apparatus provided by an embodiment of the present invention.

FIG. 3 is a schematic diagram of an electrical heating circuit and a Hi-pot test circuit in the apparatus according to the embodiment of the present invention.

Fig. 4 is a main flow chart of a method according to an embodiment of the present invention.

Detailed Description

In the following description of the embodiments of the present invention, reference is made to the accompanying drawings, which are included to provide further illustration of the invention, and in which orientation may be defined for the purpose of clarity only, and not for the purpose of limiting the device to the actual orientation during manufacture, use, sale, etc.

The following further describes embodiments of the present invention with reference to the accompanying drawings:

the equipment provided by the embodiment is used for carrying out hot pressing on the lithium battery cell and improving the bonding force of the lithium battery cell diaphragm, wherein the lithium battery cell refers to a winding body of a positive pole piece, a diaphragm and a negative pole piece, a pole lug is welded, and the pole piece positioned on the outer layer of the winding body (the positive pole is taken as an example in the embodiment) is provided with an exposed conductive part.

As shown in fig. 1, the apparatus includes at least one set of pressing plate assemblies having a first pressing plate 11 and a second pressing plate 12 that provide relative pressing force to the lithium battery cells. The embodiment comprises three groups of pressing plate assemblies which are arranged in an up-and-down stacked mode and share the structure of the middle pressing plate, wherein the first pressing plate 11 and the second pressing plate 12 form a first group of pressing plate assemblies, the second pressing plate 12 and the third pressing plate 13 form a second group of pressing plate assemblies, and the third pressing plate 13 and the fourth pressing plate 14 form a third group of pressing plate assemblies. Specifically, the first pressing plate 11 is fixedly disposed on the machine table 10, the second pressing plate 12, the third pressing plate 13, and the fourth pressing plate 14 are sequentially disposed above the first pressing plate 11 through a guide post, and the second pressing plate 12, the third pressing plate 13, and the fourth pressing plate 14 are driven by respective pressure driving mechanisms (e.g., respective motors and screw assemblies) to move up and down.

In this embodiment, the second pressing plate 12 and the third pressing plate 13 located in the middle are vertically shared, and it is understood that each pressing plate assembly may also have two pressing plates, as long as each pressing plate assembly has a first acting surface and a second acting surface for providing relative pressure to the lithium battery cell.

Further structure of the first group of platen assemblies including the first platen 11 and the second platen 12 will be described below as an example, and the other groups of platen assemblies have the same structure.

At least one lithium battery cell placement position is arranged between the first pressing plate 11 and the second pressing plate 12, and is used for placing a lithium battery cell, in this embodiment, the positive electrode plate is exposed to the outer-layer battery cell after winding is taken as an example for description (the negative electrode plate is exposed to the outer-layer battery cell after winding may be referred to correspondingly). Corresponding to each lithium battery cell placement position, first clamp plate 11 is last to be set up: the hot-pressing lithium battery comprises a first connecting piece 111 used for being electrically connected with a positive tab of a lithium battery cell, a second connecting piece 112 used for being electrically connected with a negative tab of the lithium battery cell to be hot-pressed, and a third connecting piece 113 used for being electrically connected with an outer electrode pole piece of the lithium battery cell to be hot-pressed. The first connecting member 111, the second connecting member 112, and the third connecting member 113 are insulated from each other.

Specifically, the third connecting member 113 is a conductive contact plate and is disposed at the lithium battery cell placement position, or the third connecting member 113 is the lithium battery cell placement position. Preferably, the length and the width of the third connection member 113 are both greater than those of the lithium battery cell winding body, and the lithium battery cell may be completely placed in the third connection member 113. The first and second connection members 111 and 112 are conductive contacts protruding from the surface of the first pressing plate 11. The third connecting member 113 also protrudes from the surface of the first pressing plate 11, but protrudes at a lower height than the first connecting member 111 and the second connecting member 112. The first connecting member 111, the second connecting member 112, and the third connecting member 113 are made of a material having good thermal and electrical conductivity, such as stainless steel, copper alloy, aluminum alloy, titanium alloy, nickel alloy, and magnesium alloy, and have good oxidation resistance. The first pressing plate 11 is made of an organic or inorganic material having a good insulation property, such as rubber, plastic, and natural fiber, and is used to support the first connecting member 111, the second connecting member 112, and the third connecting member 113, and to insulate and isolate the first connecting member 111, the second connecting member 112, and the third connecting member 113.

Of course, the first connecting member 111, the second connecting member 112 and the outer electrode sheet electrical connection contact member 113 may be disposed on the second pressing plate 12 in a similar manner; alternatively, the first connecting member 111, the second connecting member 112 and the third connecting member 113 may be disposed on the first pressing plate 11 and the second pressing plate 12 at the same time in the same manner, as shown in fig. 2; still alternatively, the first connecting member 111 and the second connecting member 112 are disposed on the first pressing plate 11, and the third connecting member 113 is disposed on the second pressing plate 12.

As shown in FIG. 3, the apparatus further includes a heating power supply 21 and a High-potential (Hi-pot) test power supply 22. Both poles of the heating power source 21 are connected to the first connection member 111 and the third connection member 113 through wires, respectively. The two poles of the Hi-pot test power supply 22 are connected to the first connection member 111 and the second connection member 112 through wires, respectively. When the lithium battery cell is subjected to hot pressing, the heating power supply 21 supplies power to the positive current collector of the lithium battery cell 200, the positive current collector serves as a heating resistor, heat is generated, and the hot pressing operation is performed on the battery cell under the action of the relative pressure of the first pressing plate 11 and the second pressing plate 12. In addition, after the electric heating voltage, the Hi-pot test power supply 22 applies a high voltage between the positive and negative electrodes to test the cell insulation performance.

As shown in fig. 4, the present application also provides a method for improving adhesion of a lithium battery cell membrane, including:

(1) and extruding and forming the lithium battery cell through the pressing plate assembly. Specifically, place the lithium cell in the position is placed to the lithium cell for the outer pole piece that the outer electrode pole piece electricity of lithium cell is connected contacts with the electric contact piece 113 that links that sets up on the pressure plate subassembly, and the anodal ear of lithium cell, negative pole ear respectively with the first connecting piece 111 that sets up on the pressure plate subassembly, second connecting piece 112 contact. Wherein, the pressing speed of the pressing plate component in the pressing process is controlled to be 10-600mm/min, and the pressing pressure is controlled to be 0.05-1.5 Mpa.

(2) During the extrusion molding, a heating power source 21 is connected between the first connecting member 111 and the third connecting member 113 to electrically heat the lithium battery cell. At the moment, due to the generation of ohmic heat, the temperature of the lithium battery cell rises rapidly, the diaphragm generates bonding force with the positive and negative pole pieces under the action of hot pressing, and the lithium battery cell is shaped. Specifically, the current of the electrically heated positive pole piece is 0.5-40A, the highest surface temperature of the electrically heated positive pole piece is controlled to be 70-120 ℃, and the time for electrically heating the positive pole piece is controlled to be 0.5-20 min.

In addition, a temperature sensor is used for monitoring the surface temperature of the lithium battery cell, when the temperature reaches a preset value, feedback control is adopted, the temperature is kept stable within a certain range by adjusting the current, and the electrifying heating is finished after the preset time is reached in the constant temperature stage. Preferably, the lithium battery cell after electric heating is subjected to cold pressing after the hot pressing process so as to cool and further solidify the lithium battery cell, and the cold pressing circulating water is at the temperature of 5-15 ℃ and under the pressure of 0.02-0.2MPa for 0.5-3 min.

The method further comprises the following steps:

(3) a Hi-pot test power supply 22 is connected between the first connecting piece 111 and the second connecting piece 112, and a high voltage is applied between the positive electrode tab and the negative electrode tab to perform a Hi-pot withstand voltage test. Specifically, the required voltage is 30V-200V, and the leakage current under the test high voltage is compared with the set judgment current to test whether the insulation performance of the lithium battery cell is qualified under the transient high voltage.

Based on the above-described apparatus and method, the following examples are given to illustrate the advantageous effects of the present invention:

example 1: adopt the coiling formula lithium cell that capacity is 4500mAh, anodal lithium cobaltate that adopts, the negative pole adopts artificial graphite, anodal mass flow body is the aluminium foil of 10um thickness, and the outermost circle of lithium cell is anodal light aluminium foil, and the surface does not have insulating property's organic or inorganic coating. The positive pole lug adopts aluminium system utmost point ear, is connected through ultrasonic bonding's mode between utmost point ear and the aluminium foil, and the resistance of measuring utmost point ear to the mass flow body tail end is 0.014 omega, and the negative pole mass flow body is the copper foil that 6um is thick, and the length and width height specification of lithium cell main part is 4.0mm, 58.0mm, 82.0mm respectively.

And 8 lithium battery cores are placed in the pressing plate assembly for each layer, the pressing pressure is set to be 0.3Mpa, the pressing speed is 120mm/min, and the positive electrode lug and the negative electrode lug of each lithium battery core are tightly attached to the first connecting piece 111 and the second connecting piece 112 respectively. After the pressing is finished, a 20A direct current power supply is connected between the positive electrode lug and the outermost positive electrode current collector, due to the impedance of the positive electrode current collector, heat can be rapidly generated when a large current passes through, the surface temperature of the lithium battery cell is monitored through a heat sensor, when the surface temperature of the lithium battery cell reaches 95 ℃, the current is automatically adjusted to keep the temperature of the lithium battery cell constant, and the heating is continuously carried out for 3 min; and then heating is finished, and a 50V power supply is connected between the positive electrode lug and the negative electrode lug to test whether a tiny short-circuit point exists between the positive electrode lug and the negative electrode lug. Picking out unqualified products, and then transferring the qualified battery cores into cold pressing equipment for cooling, wherein the cold pressing pressure is 0.1Mpa, the circulating water temperature is 10 ℃, and the time is 1 min. And after finishing, carrying out procedures such as rubberizing, packaging, liquid injection, aging, formation, capacity grading and the like on the lithium battery cell. In the formation procedure, the formation temperature of the battery cell is 70 ℃ and the pressure is 0.6 MPa.

Example 2: this example is different from example 1 in that a pressing pressure of 0.5MPa was used.

Example 3: this example is different from example 1 in that a pressing pressure of 0.1MPa was used.

Example 4: the present example is different from example 1 in that the maximum temperature of the hot pressing of the lithium cell was controlled at 105 ℃.

Example 5: the example is different from example 1 in that the maximum temperature of the hot pressing of the lithium cell was controlled to 85 ℃.

Example 6: the difference between the example and the example 1 is that the time for hot-pressing the lithium battery cell is controlled to be 0.5 min.

Example 7: the difference between this example and example 1 is that the time for hot-pressing the lithium cell was controlled to 10 min.

Comparative example 1: according to the comparative example, the lithium battery cell is hot-pressed by adopting a conventional process (a hot pressing plate mode), and the lithium battery cell is shaped by only carrying out hot pressing treatment under small pressure and low temperature, wherein the pressure is 0.05Mpa, the temperature of the hot pressing plate is 50 ℃, and the hot pressing time is 3 min; the formation process adopts conventional process, and the formation temperature is 88 deg.C and the pressure is 0.96 Mpa.

3 cells are taken out from examples 1-7 and comparative example 1 respectively to carry out a three-point bending hardness test, the pressing speed is 10mm/min, and the pressing displacement is 5 mm; the Hi-pot test was performed using a voltage of 50V, taking 20 cells from examples 1-7 and comparative example 1, respectively, and measuring the breakdown current, and if the current is greater than 100uA, it was considered as failing; the cell was charged and discharged in a 0.5C/0.5C mode, and the thickness expansion rate and the capacity retention rate after 800T were calculated.

Table 1 shows the hardness, Hi-pot test pass rate, cycle thickness expansion rate, and capacity retention rate test results of the lithium cores of examples 1 to 7 and comparative example 1.

As can be seen from table 1, the lithium battery cell manufactured by the apparatus and the method of the present invention can significantly improve the hardness of the battery cell, reduce the cycle expansion rate, and improve the cycle retention rate. In addition, when a lithium battery core is disassembled, the bonding strength of the diaphragm of the example 1 is better than that of the diaphragm of the comparative example 1, the diaphragm still has good bonding property with the positive electrode and the negative electrode after the circulation is finished, the bonding degree of the whole pole piece is consistent, the situation that the bonding strength of the diaphragm is inconsistent can be found in the comparative example after the circulation is finished, the bonding force of the diaphragm in a partial area is poor, and the phenomenon can cause the lithium precipitation of the negative electrode and the capacity attenuation. Meanwhile, the strength and the adhesive force of the cell can be improved by increasing the temperature and the pressure of the lithium cell in the electrifying and hot-pressing process, but a very small number of cell High-potential (High potential) tests may not pass, which may be caused by the fact that a small amount of dust pierces through the diaphragm in the electrifying and hot-pressing process.

The above embodiments are merely for full disclosure and not for limitation, and any replacement of equivalent technical features, which can be obtained without inventive work based on the gist of the present invention, should be construed as the scope of the present disclosure.