Lithium polymer battery and preparation method thereof

Abstract

The present application provides a lithium polymer battery and a preparation method thereof. The preparation method of the lithium polymer battery comprises the following steps: placing a diaphragm in a molten hot melt adhesive for infiltration to obtain a reinforced diaphragm, thereby effectively preventing the lithium polymer battery from internal corrosion and expansion problems and improving the safety performance of the lithium polymer battery; attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced diaphragm respectively to obtain a rolled chip; performing a pole ear welding operation on the rolled chip to obtain a rolled chip to be wound; performing a winding operation on the rolled chip to be wound to obtain a rolled core body; performing a hot pressing operation on the rolled core body to obtain an integrated battery cell; placing the integrated battery cell in an aluminum-plastic sleeve, injecting an electrolyte, and then performing a packaging operation to obtain a lithium polymer battery, further improving the structural stability and safety of the lithium polymer battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium polymer battery and a preparation method thereof. Background Art

[0002] Lithium polymer batteries use solid polymer electrolytes instead of liquid electrolytes. This polymer can be "dry" or "colloidal". Currently, most of them use polymer gel electrolytes. Lithium polymer batteries have good shaping flexibility and high volume utilization. Therefore, the sales volume of lithium polymer batteries has been increasing, and the production pressure of lithium polymer batteries has also been increasing, especially for the transportation, production and application of lithium polymer batteries, which require higher conditions.

[0003] Lithium polymer batteries include polymer materials and aluminum-plastic films. When the aluminum-plastic film is damaged, the middle aluminum layer will come into contact with the negative electrode and electrolyte, thus forming ion channels and electron channels, leading to internal corrosion of the aluminum-plastic film. Internal corrosion of the aluminum-plastic film will cause battery bloating and leakage, and create a series of safety hazards. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a lithium polymer battery and a preparation method thereof which can prevent internal corrosion and improve safety.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a lithium polymer battery comprises the following steps:

[0007] The diaphragm is placed in molten hot melt adhesive for infiltration to obtain a reinforced diaphragm;

[0008] Attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced separator to obtain a rolled chip;

[0009] Performing a tab welding operation on the coiled chip to obtain a coiled chip to be wound;

[0010] Performing a winding operation on the core to be wound to obtain a winding core body;

[0011] Performing a hot pressing operation on the core body to obtain an integrated battery cell;

[0012] The integrated battery cell is placed in an aluminum-plastic casing, packaged, and then injected with electrolyte to obtain the lithium polymer battery.

[0013] In one embodiment, after the step of placing the diaphragm in molten hot melt adhesive for infiltration to obtain a reinforced diaphragm, and before the step of attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced diaphragm to obtain a rolled chip, the method for preparing a lithium polymer battery further includes the following steps:

[0014] A release film is attached to the surface of the reinforced separator.

[0015] In one embodiment, after the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting electrolyte, and then performing packaging to obtain the lithium polymer battery, the method for preparing the lithium polymer battery further includes the following steps:

[0016] The inner wall of the aluminum-plastic sleeve is coated with adhesive.

[0017] In one embodiment, the adhesive is PP glue or PE glue.

[0018] In one embodiment, after the step of placing the integrated battery cell into the aluminum-plastic casing and before the step of performing the packaging operation, the method for preparing the lithium polymer battery further comprises the following steps:

[0019] An adhesive coating operation is performed on the packaging portion of the pole ear and the aluminum-plastic sleeve to form pole ear glue.

[0020] In one embodiment, before the step of placing the diaphragm into molten hot melt adhesive for infiltration to obtain a reinforced diaphragm, the method for preparing a lithium polymer battery further includes the following steps:

[0021] Add 0.05 to 0.2 parts by weight of a foaming agent to the molten hot melt adhesive.

[0022] In one embodiment, the temperature during the hot pressing operation is 100°C to 150°C.

[0023] In one embodiment, the pressure in the hot pressing operation is 0.05 MPa to 0.5 MPa.

[0024] In one embodiment, after the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting electrolyte, and then performing packaging to obtain the lithium polymer battery, the method for preparing the lithium polymer battery further includes the following steps:

[0025] A layer of PP glue or PE glue is coated on the surface of the integrated battery core.

[0026] A lithium polymer battery is prepared by the method for preparing a lithium polymer battery as described in any of the above embodiments.

[0027] Compared with the prior art, the present invention has at least the following advantages:

[0028] 1. In the preparation method of the lithium polymer battery of the present invention, the diaphragm is placed in the molten hot melt adhesive for infiltration. Through the infiltration of the molten hot melt adhesive, a hot melt adhesive layer is formed on the surface of the diaphragm. The hot melt adhesive layer can protect the diaphragm to obtain a reinforced diaphragm, thereby effectively preventing the internal corrosion and expansion problems of the lithium polymer battery and improving the safety performance of the lithium polymer battery; further, the hot melt adhesive layer infiltrated on the surface of the diaphragm can also improve the mechanical properties of the diaphragm, such as strength, flexibility and ductility, which is beneficial to improve the stability of the core during the winding process, and then improve the electrical performance and structural stability of the lithium polymer battery.

[0029] 2. In the preparation method of the lithium polymer battery of the present invention, since the positive electrode sheet and the negative electrode sheet are respectively attached to the two sides of the reinforced diaphragm, the hot melt adhesive layer in the diaphragm can effectively enhance the bonding strength between the winding core, that is, the positive and negative electrode sheets and the diaphragm, thereby preventing the positive and negative electrode sheets and the diaphragm from sliding relative to each other during the winding process or during the use of the battery. In addition, the hot melt adhesive layer in the diaphragm has ductility during the winding process, and can compensate for the bending and fitting parts of the winding core, preventing the occurrence of gaps or poor contact in the winding core, thereby effectively improving the structural stability and safety of the winding core. In addition, by hot pressing the winding core, on the one hand, the hot melt adhesive layer in the diaphragm can be squeezed, further improving the compensation effect of the hot melt adhesive between the diaphragm and the electrode sheet, and improving the tightness of the winding core; on the other hand, after hot pressing the winding core, the hot melt adhesive in the winding core can be solidified, thereby obtaining an integrated battery cell, further improving the structural stability and safety of the lithium polymer battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 is a flow chart of a method for preparing a lithium polymer battery in one embodiment;

[0032] Figure 2 for Figure 1 The schematic diagram of the structure of the lithium polymer battery shown;

[0033] Figure 3 for Figure 2 A partial cross-sectional view of the lithium polymer battery shown;

[0034] Figure 4 for Figure 2 A partial enlarged schematic diagram of a lithium polymer battery is shown;

[0035] Figure 5 for Figure 3 A partial cross-sectional view of a lithium polymer battery is shown. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention 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 disclosure of the present invention more thoroughly understood.

[0037] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0039] The present application provides a method for preparing a lithium polymer battery. The method for preparing the lithium polymer battery comprises the following steps: placing a diaphragm in a molten hot melt adhesive for infiltration to obtain a reinforced diaphragm; attaching a positive electrode sheet and a negative electrode sheet to the two sides of the reinforced diaphragm respectively to obtain a rolled chip; performing a tab welding operation on the rolled chip to obtain a rolled chip to be wound; performing a winding operation on the rolled chip to be wound to obtain a rolled core body; performing a hot pressing operation on the rolled core body to obtain an integrated battery cell; placing the integrated battery cell in an aluminum-plastic sleeve, injecting an electrolyte, and then performing a packaging operation to obtain the lithium polymer battery.

[0040] In the above-mentioned preparation method of lithium polymer battery, the diaphragm is placed in molten hot melt adhesive for infiltration operation. Through the infiltration of molten hot melt adhesive, a layer of hot melt adhesive layer is formed on the surface of the diaphragm. The hot melt adhesive layer can protect the diaphragm to obtain a reinforced diaphragm, thereby effectively preventing the internal corrosion and expansion problems of the lithium polymer battery and improving the safety performance of the lithium polymer battery; further, the hot melt adhesive layer infiltrated on the surface of the diaphragm can also improve the mechanical properties of the diaphragm, such as strength, flexibility and ductility, which is beneficial to improve the stability of the core during the winding process, and then improve the electrical performance and structural stability of the lithium polymer battery. Furthermore, since the positive electrode sheet and the negative electrode sheet are respectively attached to the two sides of the reinforced diaphragm, the hot melt adhesive layer in the diaphragm can effectively enhance the bonding strength between the winding core, that is, the positive and negative electrode sheets and the diaphragm, thereby preventing the positive and negative electrode sheets and the diaphragm from sliding relative to each other during the winding process or during the use of the battery. Moreover, the hot melt adhesive layer in the diaphragm has ductility during the winding process, which can compensate for the bending and fitting parts of the winding core, prevent the occurrence of gaps or poor contact in the winding core, and effectively improve the structural stability and safety of the winding core. In addition, by hot pressing the winding core, on the one hand, the hot melt adhesive layer in the diaphragm can be squeezed, further improving the compensation effect of the hot melt adhesive between the diaphragm and the electrode sheet, and improving the tightness of the winding core; on the other hand, after hot pressing the winding core, the hot melt adhesive in the winding core can be solidified, thereby obtaining an integrated battery cell, further improving the structural stability and safety of the lithium polymer battery cell.

[0041] In order to better understand the preparation method of the lithium polymer battery of the present invention, the preparation method of the lithium polymer battery of the present invention is further explained below. Figure 1 As shown, a method for preparing a lithium polymer battery according to an embodiment of the present invention comprises some or all of the following steps:

[0042] S100, placing the diaphragm into molten hot melt adhesive for infiltration operation to obtain a reinforced diaphragm.

[0043] In this embodiment, the molten hot melt adhesive is placed in a reaction kettle, and the diaphragm is placed in the molten hot melt adhesive for infiltration. Through the infiltration of the molten hot melt adhesive, a layer of hot melt adhesive is formed on the surface of the diaphragm. The hot melt adhesive layer can protect the diaphragm to obtain a reinforced diaphragm, thereby effectively preventing the internal corrosion and expansion problems of the lithium polymer battery and improving the safety performance of the lithium polymer battery; further, the hot melt adhesive layer infiltrated on the surface of the diaphragm can also improve the mechanical properties of the diaphragm, such as strength, flexibility and ductility, which is beneficial to improve the stability of the core during the winding process, and then improve the electrical performance and structural stability of the lithium polymer battery.

[0044] S200, attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced separator respectively to obtain a rolled chip.

[0045] In this embodiment, the positive electrode sheet and the negative electrode sheet are respectively attached to the two sides of the reinforced diaphragm, that is, the prepared positive electrode sheet is attached to one side of the reinforced diaphragm, and the prepared negative electrode sheet is attached to the side of the reinforced diaphragm away from the positive electrode sheet, so that the hot melt adhesive layer in the diaphragm can effectively enhance the winding chip, that is, the bonding strength between the positive and negative electrode sheets and the diaphragm, thereby preventing the positive and negative electrode sheets and the diaphragm from sliding relative to each other during the winding process or during the use of the battery, and the hot melt adhesive layer in the diaphragm is ductile during the winding process, which can compensate for the bending and fitting parts of the winding core, prevent the occurrence of gaps or poor contact in the winding core, and thus effectively improve the structural stability and safety of the winding core.

[0046] S300, performing a winding operation on the core sheet to be wound to obtain a winding core body.

[0047] In this embodiment, the winding machine is used to wind the winding chip, so that the diaphragm, positive electrode sheet and negative electrode sheet are wound to form a single winding core. In the winding core, the negative electrode wraps the positive electrode, and the positive and negative electrode sheets are separated by the diaphragm. The operation of the winding battery cell is relatively simple, and it can be completed quickly whether it is semi-automatic or fully automatic. In addition, in terms of the quality control of the battery cell, the winding type is easier to control and can effectively improve the consistency of the lithium battery cell.

[0048] S400, performing a hot pressing operation on the core body to obtain an integrated battery cell.

[0049] It is understandable that, whether in winding or Z-type lamination, a certain tension must be applied to the diaphragm to ensure the neatness between the positive electrode sheet, the diaphragm, and the negative electrode sheet. However, the tension in the process will cause the diaphragm to be stretched in the direction of the tape, and the shrinkage of the diaphragm in the direction of the tape is large, which will cause the diaphragm to severely squeeze the electrode sheet, thereby causing the battery cell to deform after the battery cell assembly process, especially the winding process. The deformed battery cell not only has poor appearance flatness, but also has defects such as diaphragm wrinkles inside. In this embodiment, by hot pressing the core body, on the one hand, the hot melt adhesive layer in the diaphragm can be squeezed, further improving the compensation effect of the hot melt adhesive between the diaphragm and the electrode sheet, eliminating the diaphragm wrinkles, and driving out the air inside the battery cell, so that the diaphragm and the positive and negative electrode sheets are closely attached together, shortening the lithium ion diffusion distance, reducing the internal resistance of the battery, and improving the compactness and consistency of the core body; on the other hand, after hot pressing the core body, the hot melt adhesive in the core body can be solidified, thereby obtaining an integrated battery cell, further improving the structural stability and safety of the lithium polymer battery cell.

[0050] S500, the integrated battery cell is placed in an aluminum-plastic casing, packaged, and then injected with electrolyte to obtain a lithium polymer battery.

[0051] In this embodiment, after the tabs of the wound battery cell are welded, the welded battery cell is placed in a punched aluminum-plastic film and subjected to top and side sealing processes, and then an electrolyte is injected into the packaged battery cell to obtain a lithium polymer battery.

[0052] In one embodiment, after the step of placing the diaphragm in the molten hot melt adhesive for infiltration to obtain a reinforced diaphragm, and before the step of attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced diaphragm to obtain a rolled chip, the preparation method of the lithium polymer battery also includes the following steps: attaching a release film to the surface of the reinforced diaphragm. It can be understood that after infiltration in the molten hot melt adhesive, a layer of hot melt adhesive is adhered to both sides of the diaphragm, making the diaphragm have strong adhesion, and the diaphragm is in the form of a sheet or strip, so it is easy to cause the problem of winding and bonding, which is not convenient for the diaphragm to be adhered to the positive and negative electrode sheets. Moreover, before the diaphragm is adhered to the positive and negative electrode sheets, the hot melt adhesive layer in the diaphragm is easy to adhere to dust or other impurities, thereby reducing the adhesion between the diaphragm and the positive and negative electrode sheets. In order to ensure the adhesion between the diaphragm and the positive and negative electrode sheets and improve the stability of the adhesion operation, in the present embodiment, the diaphragm is infiltrated in molten hot melt adhesive to form a hot melt adhesive layer. After obtaining a reinforced diaphragm, a release film is attached to the surface of the reinforced diaphragm to prevent the reinforced diaphragms from being entangled and adhered to each other. At the same time, it can protect the hot melt adhesive layer in the reinforced diaphragm from adhering to dust or other impurities, thereby ensuring the adhesion of the hot melt adhesive layer, and facilitating the adhesion operation between the diaphragm and the positive and negative electrode sheets. Furthermore, when the diaphragm is adhered to the positive and negative electrode sheets, the release film on one side of the reinforced diaphragm is first maintained unchanged, and then the release film on the other side is gradually torn off, and at the same time, the positive electrode sheet and the exposed hot melt adhesive layer in the reinforced diaphragm are adhered; after the adhesion between the positive electrode sheet and the reinforced diaphragm is completed, the reinforced diaphragm is turned over, and the release film on the side away from the positive electrode sheet is gradually torn off, and at the same time, the negative electrode sheet and the exposed hot melt adhesive layer in the reinforced diaphragm are adhered. In this way, the bonding stability between the reinforced diaphragm and the positive and negative electrode sheets can be effectively improved.

[0053] In one embodiment, after the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting electrolyte, and then performing packaging to obtain a lithium polymer battery, the method for preparing a lithium polymer battery further includes the following steps: coating the inner wall of the aluminum-plastic sleeve with an adhesive. It is understandable that in conventional soft-pack lithium batteries, the aluminum-plastic sleeve is prone to being exposed, thereby generating an electron path and an ion path inside the lithium battery, that is, the negative electrode and the aluminum layer of the aluminum-plastic film form an electron path, and the aluminum layer of the aluminum-plastic film and the electrolyte form an ion path, so that internal corrosion occurs inside the lithium battery, thereby destroying the performance of the lithium battery. Moreover, lithium ions react with the aluminum layer of the aluminum-plastic film to generate aluminum alloy; and lithium-aluminum alloy is a powdery substance that can cause the aluminum-plastic film to be pierced. In order to prevent the internal corrosion and leakage of lithium polymer batteries and improve the stability of lithium polymer batteries, in this embodiment, the inner wall of the aluminum-plastic film is coated with an adhesive so that an adhesive coating layer is formed on the inner wall of the aluminum-plastic film, and then the aluminum-plastic film is stamped to form an aluminum-plastic sleeve matching the integrated battery core, and then the integrated battery core is placed in the aluminum-plastic sleeve for electrolyte injection and packaging. Since the inner wall of the aluminum-plastic film is coated with an adhesive coating layer, it can play a buffering and compensating role on the aluminum-plastic film during the stamping operation, thereby improving the sealing and flexibility of the aluminum-plastic sleeve, and effectively preventing the lithium polymer battery from leaking. Furthermore, the adhesive is coated on the inner wall of the aluminum-plastic sleeve, which can protect the aluminum-plastic sleeve and effectively isolate the aluminum-plastic sleeve from forming an electron path with the negative electrode, or the aluminum layer of the aluminum-plastic film and the electrolyte from forming an ion path. In this way, the two necessary conditions for the internal corrosion of the lithium polymer battery can be effectively blocked, thereby preventing the internal corrosion of the lithium polymer battery. In addition, the adhesive layer on the inner wall of the aluminum-plastic sleeve can improve the adhesion between the aluminum-plastic sleeve and the integrated battery cell, thereby avoiding displacement or swelling of the battery cell in the aluminum-plastic sleeve, improving the stability of the battery cell in the aluminum-plastic sleeve, and thus improving the performance of the lithium polymer battery.

[0054] Furthermore, the adhesive is PP or PE adhesive. In this embodiment, PP is polypropylene (abbreviated as "PP"), which is a thermoplastic resin obtained by polymerization of propylene. Since polypropylene has a regular structure and is highly crystallized, its melting point is as high as 167°C and has good heat resistance; the density of PP is 0.90g / cm 3, is the lightest general-purpose plastic; in addition, PP also has good corrosion resistance and insulation. Applying PP as an adhesive to the inner wall of the aluminum-plastic sleeve can resist electrolyte and have good insulation effect, which can effectively prevent the internal corrosion of the lithium polymer battery, and at the same time, it can improve the mechanical properties of the aluminum-plastic sleeve while ensuring the lightness of the aluminum-plastic sleeve. PE is polyethylene (abbreviated as "PE"), which is a thermoplastic resin obtained by polymerization of ethylene. PE has excellent low-temperature resistance (the lowest operating temperature can reach -70℃~-100℃), good chemical stability, and good corrosion resistance. In addition, PE also has good electrical insulation. Applying PP as an adhesive to the inner wall of the aluminum-plastic sleeve can resist electrolyte and have good insulation effect, which can effectively prevent the internal corrosion of the lithium polymer battery, and at the same time, it can effectively improve the low-temperature resistance of the lithium polymer battery.

[0055] In one embodiment, after the step of loading the integrated battery into the aluminum-plastic sleeve and before the step of performing the packaging operation, the preparation method of the lithium polymer battery further includes the following steps: applying adhesive to the packaging part of the pole ear and the aluminum-plastic sleeve to form a pole ear glue. In this embodiment, the pole ear glue is applied to the packaging part of the pole ear and the aluminum-plastic sleeve to prevent a short circuit between the metal strip and the aluminum-plastic film during battery packaging, and is sealed and bonded to the aluminum-plastic film by heating during packaging to prevent leakage. Further, the adhesive is PP or PE glue, which can be resistant to electrolyte and has a good insulation effect, can effectively prevent the internal corrosion of the lithium polymer battery, and can improve the mechanical properties of the pole ear and ensure the lightness of the lithium polymer battery. Further, PP glue and PE glue have good thermoplasticity, and through hot pressing operation, the bonding tightness between the pole ear, the pole ear glue and the aluminum-plastic film can be effectively improved, thereby further improving the sealing of the packaging and achieving a better anti-leakage effect. In addition, during the hot pressing process, since PP glue and PE glue have good thermoplasticity, the ear glue can play a good compensation role, preventing the aluminum-plastic film from wrinkling or shifting during the hot pressing process, thereby improving the flatness of the lithium polymer battery packaging.

[0056] In one embodiment, before the step of placing the diaphragm in the molten hot melt adhesive for infiltration to obtain the reinforced diaphragm, the preparation method of the lithium polymer battery further includes the following steps: adding 0.05 to 0.2 parts by mass of a foaming agent to the molten hot melt adhesive. It is understandable that the diaphragm is placed in the molten hot melt adhesive for infiltration, and a layer of hot melt adhesive is formed on the surface of the diaphragm through the infiltration of the molten hot melt adhesive. The hot melt adhesive layer can protect the diaphragm to obtain a reinforced diaphragm, thereby effectively preventing the lithium polymer battery from internal corrosion and expansion problems and improving the safety performance of the lithium polymer battery. However, the density of the traditional molten hot melt adhesive is relatively large and the permeability is relatively poor, making it difficult for the electrolyte to move from the positive electrode to the negative electrode through the hot melt adhesive layer, that is, it is difficult for the lithium ions generated on the positive electrode of the lithium polymer battery to move to the negative electrode through the electrolyte, thereby reducing the electrical performance and charge and discharge efficiency of the lithium polymer battery. In order to improve the anti-internal corrosion ability of lithium polymer batteries and improve the electrical performance and charge-discharge efficiency of lithium polymer batteries, in this embodiment, 0.05 to 0.2 parts by mass of a foaming agent is added to the molten hot melt adhesive. The foaming agent is a substance that makes the object material pore-forming. By adding a foaming agent to the molten hot melt adhesive, the molten hot melt adhesive in a viscous flow state can form a honeycomb pore structure, thereby improving the permeability of the hot melt adhesive layer in the diaphragm, so that the electrolyte can easily move from the positive electrode to the negative electrode through the hot melt adhesive layer, that is, the lithium ions generated on the positive electrode of the lithium polymer battery can move to the negative electrode more quickly through the electrolyte, thereby improving the electrical performance and charge-discharge efficiency of the lithium polymer battery. In addition, the mass part of the foaming agent is 0.05 to 0.2 parts. It can be understood that if the amount of the foaming agent added is too little, it is difficult to achieve a good foaming effect, and the permeability of the hot melt adhesive layer is likely to be poor; if the amount of the foaming agent added is too much, it is easy to destroy the anti-internal corrosion effect of the hot melt adhesive layer. In this embodiment, adding 0.05 to 0.2 parts by mass of a foaming agent to the molten hot melt adhesive can form a relatively uniform honeycomb cell structure in the hot melt adhesive layer on the diaphragm, thereby ensuring the anti-corrosion effect of the hot melt adhesive layer while improving the electrical properties and charge and discharge efficiency of the lithium polymer battery.

[0057] Furthermore, the foaming agent is at least one of butane, AC foaming agent, NaHCO3, p-toluenesulfonyl hydrazide, and N, N-dinitrosopentamethylenetetramine. It is understandable that the molten hot melt adhesive has a relatively high temperature. If the foaming agent has poor high temperature resistance, it is easy to fail to exert the foaming effect, resulting in a poor cell structure in the hot melt adhesive. In order to improve the foaming stability in the hot melt adhesive, in this embodiment, the foaming agent is at least one of butane, AC foaming agent, NaHCO3, p-toluenesulfonyl hydrazide, and N, N-dinitrosopentamethylenetetramine. Butane foaming agent belongs to hydrocarbon foaming agent, which can be separated from petroleum gas and does not need to be synthesized by special methods; the raw materials are cheap and easy to obtain, and the foaming effect is good; it will not produce ozone-depleting substances like chlorofluorocarbon foaming agents, and will not damage the atmospheric ozone layer, which is beneficial to environmental protection. Azodicarbonamide, commonly known as AC foaming agent, has the characteristics of large foaming gas volume, uniform foaming and ideal pore structure; and AC foaming agent has good dispersibility, mainly releasing N2 and CO2, and is not easy to overflow from the foam. As an inorganic foaming agent, NaHCO3 has the advantages of being non-toxic, absorbing heat during decomposition, and the product CO2 is easily dissolved and diffused in the polymer. Therefore, adding NaHCO3 as a foaming agent to the molten hot melt adhesive not only has a good foaming effect, forming a uniform pore structure in the hot melt adhesive layer, but also has good safety. Adding p-toluenesulfonylhydrazine as a foaming agent to the molten hot melt adhesive can make the pore structure of the hot melt adhesive layer formed on the surface of the diaphragm uniform and fine, with a small shrinkage rate and high fracture strength. In addition, the above-mentioned foaming agents all have good high temperature resistance, can play a good foaming effect in the molten hot melt adhesive, and improve the foaming stability in the hot melt adhesive.

[0058] In one embodiment, the temperature during the hot pressing operation is 100°C to 150°C. In this embodiment, by hot pressing the core body, on the one hand, the hot melt adhesive layer in the diaphragm can be squeezed, further improving the compensation effect of the hot melt adhesive between the diaphragm and the pole piece, eliminating the diaphragm wrinkles, driving out the air inside the battery cell, making the diaphragm and the positive and negative pole pieces fit closely together, shortening the lithium ion diffusion distance, reducing the internal resistance of the battery, and improving the compactness and consistency of the core body; on the other hand, after hot pressing the core body, the hot melt adhesive in the core body can be solidified to obtain an integrated battery cell, further improving the structural stability and safety of the lithium polymer battery cell. However, if the intensity of the hot pressing is too large, it is easy to cause wrinkles on the surface of the core, thereby affecting the flatness of the surface of the integrated battery cell. If the intensity of the hot pressing is too small, it is easy to reduce the compactness and consistency of the core body, and also affect the curing effect of the hot melt adhesive in the core body. In this embodiment, the temperature during the hot pressing operation is 100°C to 150°C, which can effectively avoid the problem of wrinkles on the surface of the core during the hot pressing process, improve the flatness of the surface of the integrated battery cell, and at the same time improve the tightness and consistency of the core body, and enhance the curing effect of the hot melt adhesive in the core body.

[0059] Furthermore, the pressure in the hot pressing operation is 0.05MPa~0.5MPa. It can be understood that if the pressure in the hot pressing operation is too large, even if the temperature is suitable, it is easy to cause wrinkles on the surface of the core, thereby affecting the flatness of the surface of the integrated battery cell; if the pressure in the hot pressing operation is too small, even if the temperature is suitable, it is easy to reduce the tightness and consistency of the core body, and at the same time affect the curing effect of the hot melt adhesive in the core body. In order to improve the hot pressing stability of the integrated battery cell, in this embodiment, the pressure in the hot pressing operation is 0.05MPa~0.5MPa, and the temperature in the hot pressing operation is set to 100℃~150℃, which can effectively avoid the problem of wrinkles on the surface of the core during the hot pressing process, improve the flatness of the surface of the integrated battery cell, and at the same time improve the tightness and consistency of the core body, and enhance the curing effect of the hot melt adhesive in the core body, further improving the hot pressing stability of the integrated battery cell.

[0060] In one embodiment, after the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting an electrolyte, and then performing a packaging operation to obtain a lithium polymer battery, the method for preparing a lithium polymer battery further includes the following steps: coating a layer of PP glue or PE glue on the surface of the integrated battery cell. It is understandable that during the hot pressing packaging process, the aluminum-plastic sleeve is prone to overpressure or damage to the surface of the integrated battery cell. In addition, there is a problem of poor consistency of the lithium polymer battery due to the easy existence of gaps or depressions between the aluminum-plastic sleeve and the integrated battery cell. The aluminum-plastic sleeve is prone to being exposed, thereby generating an electron path and an ion path inside the lithium battery, that is, the negative electrode and the aluminum layer of the aluminum-plastic film form an electron path, and the aluminum layer of the aluminum-plastic film and the electrolyte form an ion path, so that internal corrosion occurs inside the lithium battery, thereby destroying the performance of the lithium battery. In order to improve the consistency and anti-internal corrosion performance of lithium polymer batteries, in this embodiment, a layer of PP glue or PE glue is coated on the surface of the integrated battery cell to form a protective glue layer on the surface of the integrated battery cell. During the hot pressing packaging process, the protective glue layer can play a good buffering role, thereby ensuring the stability of the integrated battery cell. Furthermore, the protective glue layer can also lock the electrolyte in the integrated battery cell, maintaining full contact between the electrolyte and various parts of the integrated battery cell, thereby improving the electrical performance of the lithium polymer battery. In addition, during the high-temperature formation process of the lithium polymer battery, the PP glue or PE glue on the inner wall of the aluminum-plastic sleeve and the surface of the integrated battery cell melts, and plays a role in compensating and repairing the inside of the lithium polymer battery, thereby effectively improving the consistency of the lithium polymer battery.

[0061] Some specific examples are listed below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

[0062] Example 1

[0063] Place the molten hot melt adhesive in a reactor, add 0.05 parts by mass of a foaming agent, put the diaphragm into the molten hot melt adhesive for infiltration, then take it out to obtain a reinforced diaphragm, and attach a release film to the surface of the reinforced diaphragm. While tearing off the release film, attach the prepared positive electrode sheet to one side of the reinforced diaphragm, and attach the prepared negative electrode sheet to the side of the reinforced diaphragm away from the positive electrode sheet to form a roll chip to be wound. Then put the roll chip to be wound into a winding machine for winding operation, so that the diaphragm, positive electrode sheet and negative electrode sheet are wound to form a single roll core; the roll core body is hot-pressed to obtain an integrated battery cell, wherein the hot-pressing temperature is 100°C and the hot-pressing pressure is 0.05MPa. The integrated battery cell is placed in an aluminum-plastic sleeve, packaged, and then injected with electrolyte to obtain a lithium polymer battery.

[0064] Example 2

[0065] Place the molten hot melt adhesive in a reactor, add 0.2 parts by mass of a foaming agent, put the diaphragm into the molten hot melt adhesive for infiltration, then take it out to obtain a reinforced diaphragm, and attach a release film to the surface of the reinforced diaphragm. While tearing off the release film, attach the prepared positive electrode sheet to one side of the reinforced diaphragm, and attach the prepared negative electrode sheet to the side of the reinforced diaphragm away from the positive electrode sheet to form a roll chip to be wound. Then put the roll chip to be wound into a winding machine for winding operation, so that the diaphragm, positive electrode sheet and negative electrode sheet are wound to form a single roll core; the roll core body is hot-pressed to obtain an integrated battery cell, wherein the hot-pressing temperature is 150°C and the hot-pressing pressure is 0.5MPa. The integrated battery cell is placed in an aluminum-plastic sleeve, packaged, and then injected with electrolyte to obtain a lithium polymer battery.

[0066] Example 3

[0067] Place the molten hot melt adhesive in a reactor, add 0.1 parts by mass of a foaming agent, put the diaphragm into the molten hot melt adhesive for infiltration, then take it out to obtain a reinforced diaphragm, and attach a release film to the surface of the reinforced diaphragm. While tearing off the release film, attach the prepared positive electrode sheet to one side of the reinforced diaphragm, and attach the prepared negative electrode sheet to the side of the reinforced diaphragm away from the positive electrode sheet to form a roll chip to be wound. Then put the roll chip to be wound into a winding machine for winding operation, so that the diaphragm, positive electrode sheet and negative electrode sheet are wound to form a single roll core; the roll core body is hot-pressed to obtain an integrated battery cell, wherein the hot-pressing temperature is 120°C and the hot-pressing pressure is 0.3MPa. The integrated battery cell is placed in an aluminum-plastic sleeve, packaged, and then injected with electrolyte to obtain a lithium polymer battery.

[0068] Example 4

[0069] Place the molten hot melt adhesive in a reactor, add 0.15 parts by mass of a foaming agent, put the diaphragm into the molten hot melt adhesive for infiltration, then take it out to obtain a reinforced diaphragm, and attach a release film to the surface of the reinforced diaphragm. While tearing off the release film, attach the prepared positive electrode sheet to one side of the reinforced diaphragm, and attach the prepared negative electrode sheet to the side of the reinforced diaphragm away from the positive electrode sheet to form a roll chip to be wound. Then put the roll chip to be wound into a winding machine for winding operation, so that the diaphragm, positive electrode sheet and negative electrode sheet are wound to form a single roll core; the roll core body is hot-pressed to obtain an integrated battery cell, wherein the hot-pressing temperature is 130°C and the hot-pressing pressure is 0.25MPa. The integrated battery cell is placed in an aluminum-plastic sleeve, packaged, and then injected with electrolyte to obtain a lithium polymer battery.

[0070] The present application also provides a lithium polymer battery, which is prepared by the lithium polymer battery preparation method described in any of the above embodiments.

[0071] like Figure 2 and Figure 3 As shown, in one embodiment, the lithium polymer battery 10 includes an integrated battery cell 100, an aluminum-plastic sleeve 200 and a reinforced coating 300; the integrated battery cell 100 includes a winding core 110 and a pole ear 120, the pole ear 120 includes a negative pole ear 1220 and a negative pole ear 1240, the winding core 110 includes a positive electrode sheet 111, a negative electrode sheet 113 and a separator 115, the positive electrode sheet 111, the separator 115 and the negative electrode sheet 113 are stacked and wound in sequence, the negative pole ear 1240 is welded to the positive electrode sheet 111, and the negative pole ear 1220 is welded to the negative electrode sheet 11 3, the diaphragm 115 includes a diaphragm body 1151, a first cured adhesive layer 1153 and a second cured adhesive layer 1155, the first cured adhesive layer 1153 is respectively bonded to one side of the diaphragm body 1151 and the positive electrode sheet 111, and the second cured adhesive layer 1155 is respectively bonded to the other side of the diaphragm body 1151 and the negative electrode sheet 113; the integrated battery cell 100 is enclosed in the aluminum-plastic sleeve 200, and the negative electrode ear 1240 and the negative electrode ear 1220 are partially exposed outside the aluminum-plastic sleeve 200; the reinforcement coating 300 is coated on the inner wall of the aluminum-plastic sleeve 200.

[0072] In the above-mentioned lithium polymer battery 10, since the diaphragm 115 includes the diaphragm body 1151, the first cured adhesive layer 1153 and the second cured adhesive layer 1155, the first cured adhesive layer 1153 is respectively bonded to one side of the diaphragm body 1151 and the positive electrode sheet 111, and the second cured adhesive layer 1155 is respectively bonded to the other side of the diaphragm body 1151 and the negative electrode sheet 113, so that the diaphragm body 1151 can be bonded to the positive and negative electrode sheets 113, and the diaphragm 115 can also be protected by the first cured adhesive layer 1153 and the second cured adhesive layer 1155. , thereby preventing the tab 120 from puncturing the diaphragm 115 and avoiding leakage problems; and because the positive electrode sheet 111, the diaphragm 115 and the negative electrode sheet 113 are stacked and wound in sequence, the negative tab 1240 is welded to the positive electrode sheet 111, and the negative tab 1220 is welded to the negative electrode sheet 113, so that the first cured adhesive layer 1153 and the second cured adhesive layer 1155 are wound along with the positive and negative electrode sheets 113, thereby being able to protect the entire integrated battery cell 100 and provide an anti-corrosion effect, thereby improving the stability and safety of the lithium polymer battery 10. Since the integrated battery cell 100 is enclosed in the aluminum-plastic sleeve 200, and the negative electrode ear 1240 and the negative electrode ear 1220 are partially exposed outside the aluminum-plastic sleeve 200, the inner wall of the aluminum-plastic sleeve 200 is coated with a reinforcing coating 300, so that the aluminum-plastic sleeve 200 can cooperate with the integrated battery cell 100 to enhance the efficiency, and the reinforcing coating 300 can improve the adhesion between the aluminum-plastic sleeve 200 and the integrated battery cell, thereby avoiding the displacement or swelling of the battery cell in the aluminum-plastic sleeve 200, improving the stability of the battery cell in the aluminum-plastic sleeve 200, and thus improving the performance of the lithium polymer battery 10. Further, during the packaging stamping process, the reinforcing coating 300 can play a buffering and compensating role on the aluminum-plastic film, thereby improving the sealing and flexibility of the aluminum-plastic sleeve 200, and can effectively prevent the lithium polymer battery 10 from leaking. In addition, the reinforcing coating 300 is coated on the inner wall of the aluminum-plastic sleeve 200, which can protect the aluminum-plastic sleeve 200 and effectively isolate the aluminum-plastic sleeve 200 from forming an electron path with the negative electrode, or the aluminum layer of the aluminum-plastic film and the electrolyte from forming an ion path. In this way, the two necessary conditions for the internal corrosion of the lithium polymer battery 10 can be effectively blocked, thereby preventing the lithium polymer battery 10 from internal corrosion.

[0073] like Figure 3As shown, in one embodiment, the first cured adhesive layer 1153 is provided with a plurality of first honeycomb pore structures 1154. It is understandable that the first cured adhesive layer 1153 is respectively bonded to one side of the diaphragm body 1151 and the positive electrode sheet 111. If the permeability of the first cured adhesive layer 1153 is poor, it is easy for the electrolyte to pass through the first cured adhesive layer 1153 to reach the diaphragm body 1151, that is, it is difficult for the lithium ions generated on the positive electrode of the lithium polymer battery 10 to move to the negative electrode through the electrolyte, thereby reducing the electrical performance and charge and discharge efficiency of the lithium polymer battery 10. In order to improve the permeability of the first cured adhesive layer 1153 and improve the electrical performance and charge-discharge efficiency of the lithium polymer battery 10, in the present embodiment, the first cured adhesive layer 1153 is provided with a plurality of first honeycomb pore structures 1154, so that the electrolyte can reach the diaphragm body 1151 through the pore structure in the first cured adhesive layer 1153, thereby improving the permeability of the first cured adhesive layer 1153, and further improving the electrical performance and charge-discharge efficiency of the lithium polymer battery 10; further, the first honeycomb pore structure 1154 can further improve the uniformity of electrolyte penetration, thereby improving the uniformity of lithium ion transfer in the diaphragm 115, and further improving the performance stability of the lithium polymer battery 10.

[0074] like Figure 3 As shown, in one embodiment, the second cured adhesive layer 1155 is provided with a plurality of first honeycomb pore structures 1156. It is understandable that the second cured adhesive layer 1155 is bonded to the other side of the diaphragm body 1151 and the negative electrode sheet 113 respectively. If the permeability of the second cured adhesive layer 1155 is poor, it is easy to make it difficult for the electrolyte to pass through the diaphragm body 1151 to reach the second cured adhesive layer 1155, that is, it is difficult for the lithium ions generated on the positive electrode of the lithium polymer battery 10 to move to the negative electrode through the electrolyte, thereby reducing the electrical performance and charge and discharge efficiency of the lithium polymer battery 10. In order to improve the permeability of the second cured adhesive layer 1155 and improve the electrical performance and charge-discharge efficiency of the lithium polymer battery 10, in the present embodiment, the second cured adhesive layer 1155 is provided with a plurality of first honeycomb pore structures 1156, so that the electrolyte can reach the diaphragm body 1151 through the pore structure in the second cured adhesive layer 1155, thereby improving the permeability of the second cured adhesive layer 1155, and further improving the electrical performance and charge-discharge efficiency of the lithium polymer battery 10; further, the first honeycomb pore structure 1156 can further improve the uniformity of electrolyte penetration, thereby improving the uniformity of lithium ion transfer in the diaphragm 115, and further improving the performance stability of the lithium polymer battery 10.

[0075] like Figure 3As shown, in one of the embodiments, the lithium polymer battery 10 also includes a hot melt adhesive layer 400, which is coated on the surface of the integrated battery cell 100, so that a protective adhesive layer is formed on the surface of the integrated battery cell. During the hot pressing packaging process, the protective adhesive layer can play a good buffering role, thereby ensuring the stability of the integrated battery cell. Furthermore, the protective adhesive layer can also lock the electrolyte in the integrated battery cell, maintaining full contact between the electrolyte and various parts of the integrated battery cell, thereby improving the electrical performance of the lithium polymer battery 10. In addition, during the high-temperature formation process of the lithium polymer battery 10, the hot melt adhesive layer 400 on the inner wall of the aluminum-plastic sleeve 200 and the surface of the integrated battery cell melts, and plays a role in compensating and repairing the inside of the lithium polymer battery 10, thereby effectively improving the consistency of the lithium polymer battery 10.

[0076] like Figure 4 As shown, in one embodiment, the tab 120 includes a tab body 121 and a tab glue 123, the tab glue 123 is coated on the surface of the tab body 121, and the tab glue 123 is used to bond with the aluminum-plastic sleeve 200. In this embodiment, the tab glue 123 can prevent a short circuit between the metal strip and the aluminum-plastic film when the lithium polymer battery 10 is packaged, and the tab glue 123 can be heat-melted and sealed with the aluminum-plastic film during packaging, thereby effectively preventing leakage.

[0077] Furthermore, if Figure 4As shown, the tab glue 123 includes an insulating portion 1231 and an adhesive portion 1233, the insulating portion 1231 is connected to the adhesive portion 1233, the adhesive portion 1233 is used to bond with the aluminum-plastic sleeve 200, the insulating portion 1231 is exposed outside the aluminum-plastic sleeve 200, and the thickness of the adhesive portion 1233 is greater than the thickness of the insulating portion 1231. It can be understood that the tab 120 is a metal conductor that leads the positive and negative electrodes from the battery cell, and is coated on the surface of the tab 120, and the tab glue 123 is used to bond with the aluminum-plastic sleeve 200. On the one hand, the tab glue 123 can prevent the short circuit between the metal strip and the aluminum-plastic film when the lithium polymer battery 10 is packaged; on the other hand, the tab glue 123 can be heated and hot-melt sealed with the aluminum-plastic film during packaging, thereby effectively preventing leakage. However, the bonding between the tab glue 123 and the aluminum-plastic sleeve 200 is prone to wrinkles or poor flatness during hot-press packaging. In order to improve the flatness of the bonding point between the ear glue 123 and the aluminum-plastic sleeve 200, in the present embodiment, the ear glue 123 includes an insulating portion 1231 and a bonding portion 1233, the insulating portion 1231 is connected to the bonding portion 1233, and the bonding portion 1233 is used to bond with the aluminum-plastic sleeve 200. When the lithium polymer battery 10 is packaged, the ear glue 123 of the bonding portion 1233 can be melted by hot pressing, thereby effectively improving the sealing of the bonding point between the ear glue 123 and the aluminum-plastic sleeve 200, thereby effectively preventing the lithium polymer battery 10 from leaking. Furthermore, the insulating portion 1231 is exposed outside the aluminum-plastic sleeve 200, and can provide good insulation for the positive and negative electrode sheets 113 outside the aluminum-plastic sleeve 200, and the thickness of the bonding portion 1233 is greater than the thickness of the insulating portion 1231, so that the tab glue 123 of the bonding portion 1233 can provide good compensation for the packaging of the aluminum-plastic sleeve 200 and the tab 120, so that the hot-pressed tab glue 123 has good consistency while ensuring sealing and insulation, and at the same time improves the flatness of the bonding portion between the tab glue 123 and the aluminum-plastic sleeve 200.

[0078] Furthermore, if Figure 5 As shown, in order to further improve the sealing performance of the packaging between the pole ear 120 and the aluminum-plastic sleeve 200, in one embodiment, the lithium polymer battery 10 also includes an auxiliary reinforcement coating layer 500, and the auxiliary reinforcement coating layer 500 is adhered to the surface of the bonding portion 1233, and the viscosity of the auxiliary reinforcement coating layer 500 is greater than the viscosity of the pole ear glue 123. On the one hand, the auxiliary reinforcement coating layer 500 can enhance the bonding strength between the pole ear glue 123 and the inner wall of the aluminum-plastic sleeve 200, that is, improve the packaging sealing performance of the lithium polymer battery 10; on the other hand, the auxiliary reinforcement coating layer 500 can protect the bonding portion 1233 of the pole ear glue 123, thereby ensuring the integrity and insulation of the bonding portion 1233 of the pole ear glue 123.

[0079] In order to improve the structural consistency of the lithium polymer battery 10, in one embodiment, the thickness of the first cured adhesive layer 1153 is the same as the thickness of the second cured adhesive layer 1155. It can be understood that the first cured adhesive layer 1153 is respectively bonded to one side of the diaphragm body 1151 and the positive electrode sheet 111, and the second cured adhesive layer 1155 is respectively bonded to the other side of the diaphragm body 1151 and the negative electrode sheet 113, and the first cured adhesive layer 1153 and the second cured adhesive layer 1155 are wound together with the diaphragm body 1151 to form an integrated battery cell 100. If the thickness of the first cured adhesive layer 1153 is inconsistent with the thickness of the second cured adhesive layer 1155, it is easy to make the internal structural symmetry of the integrated battery cell 100 poor, thereby affecting the structural consistency of the lithium polymer battery 10. In the present embodiment, the thickness of the first cured adhesive layer 1153 is the same as the thickness of the second cured adhesive layer 1155 , which can effectively improve the symmetry of the two sides of the diaphragm body 1151 , so that the integrated battery cell 100 formed by winding has better structural symmetry, thereby improving the structural consistency of the lithium polymer battery 10 .

[0080] In one embodiment, the thickness of the reinforcing coating 300 is 1 μm to 3 μm. It is understandable that if the thickness of the reinforcing coating 300 is too small, it cannot play a good buffering and compensating role on the aluminum-plastic sleeve 200, and the effect of preventing internal corrosion is also poor; if the thickness of the reinforcing coating 300 is too large, it is easy to increase the weight of the lithium polymer battery 10, affecting the portability of the lithium polymer battery 10, and the thickness of the reinforcing coating 300 is too large, it is easy to waste the space in the aluminum-plastic sleeve 200 and destroy the consistency of the lithium polymer battery 10. In order to ensure the lightness of the lithium polymer battery 10 and improve the consistency of the lithium polymer battery 10, in this embodiment, the thickness of the reinforcing coating 300 is 1 μm to 3 μm, so that the reinforcing coating 300 can completely cover the inner wall of the aluminum-plastic sleeve 200, and can play a good buffering and compensating role on the aluminum-plastic sleeve 200 during the hot pressing packaging process, and the thickness of the reinforcing coating 300 is appropriate, which can ensure the lightness of the lithium polymer battery 10 and improve the consistency of the lithium polymer battery 10.

[0081] In one embodiment, the thickness of the first cured adhesive layer 1153 and the thickness of the second cured adhesive layer 1155 are both 1 μm to 3 μm. It can be understood that the first cured adhesive layer 1153 is respectively bonded to one side of the diaphragm body 1151 and the positive electrode sheet 111, and the second cured adhesive layer 1155 is respectively bonded to the other side of the diaphragm body 1151 and the negative electrode sheet 113, and the first cured adhesive layer 1153 and the second cured adhesive layer 1155 are wound together with the diaphragm body 1151 to form an integrated battery cell 100. If the thickness of the first cured adhesive layer 1153 and the thickness of the second cured adhesive layer 1155 are too small, the main body of the diaphragm 115 cannot be well protected, and the anti-corrosion effect is poor; if the thickness of the first cured adhesive layer 1153 and the thickness of the second cured adhesive layer 1155 are too large, it is easy to increase the bulkiness of the integrated battery 100, and it is not conducive to the circulation of the electrolyte in the diaphragm 115, that is, it is not conducive to the transfer of lithium ions, affecting the electrical performance and charging and discharging efficiency of the lithium polymer battery 10. In order to improve the structural consistency of the integrated battery 100 and ensure the electrical performance and charging and discharging efficiency of the lithium polymer battery 10, in this embodiment, the thickness of the first cured adhesive layer 1153 and the thickness of the second cured adhesive layer 1155 are both 1μm to 3μm, so that the thickness of the first cured adhesive layer 1153 and the thickness of the second cured adhesive layer 1155 can completely cover the main body of the diaphragm 115, play a good protective role on the main body of the diaphragm 115, and have a good anti-corrosion effect. In addition, the thickness of the first cured adhesive layer 1153 and the second cured adhesive layer 1155 of 1 μm to 3 μm can effectively improve the structural consistency of the integrated battery cell 100 and ensure the electrical performance and charge and discharge efficiency of the lithium polymer battery 10 .

[0082] Compared with the prior art, the present invention has at least the following advantages:

[0083] 1. In the preparation method of the lithium polymer battery of the present invention, the diaphragm is placed in the molten hot melt adhesive for infiltration. Through the infiltration of the molten hot melt adhesive, a hot melt adhesive layer is formed on the surface of the diaphragm. The hot melt adhesive layer can protect the diaphragm to obtain a reinforced diaphragm, thereby effectively preventing the internal corrosion and expansion problems of the lithium polymer battery and improving the safety performance of the lithium polymer battery; further, the hot melt adhesive layer infiltrated on the surface of the diaphragm can also improve the mechanical properties of the diaphragm, such as strength, flexibility and ductility, which is beneficial to improve the stability of the core during the winding process, and then improve the electrical performance and structural stability of the lithium polymer battery.

[0084] 2. In the preparation method of the lithium polymer battery of the present invention, since the positive electrode sheet is attached to one side of the reinforced diaphragm, and the negative electrode sheet is attached to the side of the reinforced diaphragm away from the positive electrode sheet, the hot melt adhesive layer in the diaphragm can effectively enhance the bonding strength between the winding chip, that is, the positive and negative electrode sheets and the diaphragm, thereby preventing the positive and negative electrode sheets and the diaphragm from sliding relative to each other during the winding process or during the use of the battery, and the hot melt adhesive layer in the diaphragm has ductility during the winding process, which can compensate for the bending and fitting parts of the winding core body, prevent the problem of gaps or poor contact in the winding core body, and effectively improve the structural stability and safety of the winding core body. In addition, by hot pressing the winding core body, on the one hand, the hot melt adhesive layer in the diaphragm can be squeezed, further improving the compensation effect of the hot melt adhesive between the diaphragm and the electrode sheet, and improving the tightness of the winding core body; on the other hand, after hot pressing the winding core body, the hot melt adhesive in the winding core body can be solidified, thereby obtaining an integrated battery cell, further improving the structural stability and safety of the lithium polymer battery cell.

[0085] The above embodiments only express several implementation methods of the present invention, 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 those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a lithium polymer battery, characterized in that: The following steps are involved: The diaphragm is placed in molten hot melt adhesive for infiltration to obtain a reinforced diaphragm; Attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced separator to obtain a rolled chip; Performing a tab welding operation on the coiled chip to obtain a coiled chip to be wound; Performing a winding operation on the core to be wound to obtain a winding core body; Performing a hot pressing operation on the core body to obtain an integrated battery cell; The integrated battery cell is placed in an aluminum-plastic casing, packaged, and then injected with electrolyte to obtain the lithium polymer battery; Among them, after the step of placing the diaphragm into the molten hot melt adhesive for infiltration to obtain the reinforced diaphragm, and before the step of attaching the positive electrode sheet and the negative electrode sheet to the two sides of the reinforced diaphragm respectively to obtain the rolled chip, the preparation method of the lithium polymer battery further includes the following steps: Attaching a release film to the surface of the reinforced diaphragm; Before the step of placing the diaphragm into the molten hot melt adhesive for infiltration to obtain the reinforced diaphragm, the method for preparing the lithium polymer battery further comprises the following steps: Adding 0.05 to 0.2 parts by weight of a foaming agent to the molten hot melt adhesive; The foaming agent is at least one of butane, AC foaming agent, NaHCO3, p-toluenesulfonyl hydrazide, and N,N-dinitrosopentamethylenetetramine.

2. The method for preparing a lithium polymer battery according to claim 1, characterized in that: After the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting electrolyte, and then performing packaging to obtain the lithium polymer battery, the method for preparing the lithium polymer battery further includes the following steps: The inner wall of the aluminum-plastic sleeve is coated with adhesive.

3. The method for preparing a lithium polymer battery according to claim 2, characterized in that: The adhesive is PP glue or PE glue.

4. The method for preparing a lithium polymer battery according to claim 1, characterized in that: After the step of placing the integrated battery cell into the aluminum-plastic casing and before the step of performing the packaging operation, the method for preparing the lithium polymer battery further comprises the following steps: An adhesive coating operation is performed on the packaging portion of the pole ear and the aluminum-plastic sleeve to form pole ear glue.

5. The method for preparing a lithium polymer battery according to claim 1, characterized in that: The temperature in the hot pressing operation is 100°C to 150°C.

6. The method for preparing a lithium polymer battery according to claim 5, characterized in that: The pressure in the hot pressing operation is 0.05 MPa to 0.5 MPa.

7. The method for preparing a lithium polymer battery according to claim 1, characterized in that: After the step of hot pressing the core body to obtain an integrated battery cell, and before the step of placing the integrated battery cell into an aluminum-plastic sleeve, injecting electrolyte, and then performing packaging to obtain the lithium polymer battery, the method for preparing the lithium polymer battery further includes the following steps: A layer of PP glue or PE glue is coated on the surface of the integrated battery core.

8. A lithium polymer battery, characterized in that: The lithium polymer battery is prepared by the method for preparing a lithium polymer battery as claimed in any one of claims 1 to 7.

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