Preparation method of lithium ion battery cell

Abstract

The invention provides a preparation method of a lithium ion battery cell, which comprises the following steps: providing a positive plate, and respectively arranging a composite solid electrolyte membrane on two opposite surfaces of the positive plate to form a positive composite structure body; providing a negative plate, and respectively arranging the composite solid electrolyte membranes on two opposite surfaces of the negative plate to form a negative composite structure body; laminating the at least one positive electrode composite structure body and the at least one negative electrode composite structure body to form a battery cell prefabricated body; and pressing the battery cell prefabricated body, and carrying out edge closing, shaping and fixing on the composite solid electrolyte membrane in the battery cell prefabricated body.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for preparing a lithium ion battery cell based on a solid electrolyte composite structure. Background Art

[0002] In the existing preparation process of lithium-ion batteries, solid electrolyte is in a fluid state and exists on the surface of the electrode sheet by injection or coating. The flow of the material needs to be controlled by a coating machine. The preparation process is complicated and the process is not easy to control.

[0003] At the same time, the existing lithium-ion battery cell is composed of a positive electrode sheet, a negative electrode sheet and a separator. In the prior art, stacking equipment is mostly used to stack the formed positive electrode sheet and negative electrode sheet alternately with the separator in the positioning space, and there is no surface bonding preparation process between the three. It is easy to cause wrinkles in the separator during the stacking process, causing lithium to be deposited during the charging and discharging process of the battery cell, and lithium dendrites will be generated, leading to safety accidents. At the same time, during the stacking process, the positive electrode sheet, negative electrode sheet, separator, etc. need to be kept in precise alignment, and the dimensional accuracy requirements are high. At the same time, the prepared lithium-ion battery cell is easy to interfere with the packaging aluminum foil. Summary of the invention

[0004] In view of this, it is indeed necessary to provide a method for preparing a lithium-ion battery cell, which is simple and conducive to improving the assembly yield of the lithium-ion battery cell.

[0005] A method for preparing a lithium ion battery cell comprises the following steps:

[0006] S1, providing a positive electrode sheet, and disposing a composite solid electrolyte membrane on two opposite surfaces of the positive electrode sheet to form a positive electrode composite structure;

[0007] S2, providing a negative electrode sheet, and arranging the composite solid electrolyte membrane on two opposite surfaces of the negative electrode sheet to form a negative electrode composite structure;

[0008] S3, stacking at least one of the positive electrode composite structures and at least one of the negative electrode composite structures to form a battery cell preform;

[0009] S4, pressing the battery cell preform, trimming, shaping and fixing the composite solid electrolyte membrane in the battery cell preform.

[0010] Compared with the prior art, the present application provides a method for preparing a lithium-ion battery cell, in which the composite solid electrolyte membrane can be directly stacked and pressed with the positive electrode sheet and the negative electrode sheet to form a lithium-ion battery cell. Before pressing, there is no need to accurately align the positions of the composite solid electrolyte membrane and the positive electrode sheet and the negative electrode sheet, and a large dimensional error can be allowed. The preparation process is simple, the process is easy to control, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of the relative position of a positive electrode composite structure provided in one embodiment of the present application.

[0012] Figure 2 A schematic diagram of the transition size of a positive electrode composite structure provided in one embodiment of the present application.

[0013] Figure 3 A schematic diagram of a right side view (non-ear side) of a battery cell preform formed by stacking a first composite structure and a second composite structure provided in one embodiment of the present application.

[0014] Figure 4 A schematic diagram from the front side (ear side) of a battery cell preform formed by stacking a first composite structure and a second composite structure provided in one embodiment of the present application.

[0015] Figure 5 A preparation flow chart (non-ear side) for pressing, trimming and fixing a battery cell preform provided in one embodiment of the present application.

[0016] Figure 6 A preparation flow chart (ear side) for pressing, trimming and fixing a cell preform provided in one embodiment of the present application.

[0017] Figure 7 A schematic diagram of a lithium-ion battery cell provided in one embodiment of the present application.

[0018] Figure 8 A schematic cross-sectional view of a lithium-ion battery cell provided in accordance with one embodiment of the present application.

[0019] Fig. 9 A schematic diagram of a lithium-ion battery cell comprising a plurality of positive electrode composite structures and a plurality of negative electrode composite structures provided in one embodiment of the present application.

[0020] Fig.10 A schematic cross-sectional view of a lithium-ion battery cell including a plurality of positive electrode composite structures and a plurality of negative electrode composite structures provided in one embodiment of the present application.

[0021] Main component symbols

[0022] Positive electrode current collector 1

[0023] Negative electrode current collector 1"

[0024] Positive electrode 10

[0025] Positive electrode composite structure 11

[0026] Negative electrode composite structure 12

[0027] Positive electrode material layer 2

[0028] Negative electrode material layer 2"

[0029] Negative electrode 20

[0030] Composite solid electrolyte membrane 3

[0031] Part I Composite Solid Electrolyte Membrane 31

[0032] Part II Composite Solid Electrolyte Membrane 32

[0033] Battery cell preform 4

[0034] Transition layer 5

[0035] Cell forming device 6

[0036] Upper Platform 61

[0037] Lower platform 62

[0038] Side edge pressing plate 63

[0039] Lower folding plate 64

[0040] Sealing structure 65

[0041] Tab 7

[0042] Lithium-ion battery cell 100

[0043] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0044] 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 technical field of the present application. The terms used herein are only for the purpose of describing specific implementation methods and are not intended to limit the present application embodiments.

[0045] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0046] Some embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0047] The first embodiment of the present application provides a method for preparing a lithium-ion battery cell, comprising the following steps:

[0048] S1, providing a positive electrode sheet 10, and disposing a composite solid electrolyte membrane 3 on two opposite surfaces of the positive electrode sheet 10 to form a positive electrode composite structure 11;

[0049] S2, providing a negative electrode sheet 20, and placing the composite solid electrolyte membrane 3 on two opposite surfaces of the negative electrode sheet 20 to form a negative electrode composite structure 12;

[0050] S3, stacking at least one positive electrode composite structure 11 and at least one negative electrode composite structure 12 to form a battery cell preform 4;

[0051] S4, pressing the battery cell preform 4, trimming and fixing the composite solid electrolyte membrane in the battery cell preform 4, and obtaining the lithium ion battery cell.

[0052] In step S1, the positive electrode sheet 10 includes a positive electrode current collector 1 and a positive electrode material layer 2 disposed on two opposite surfaces of the positive electrode current collector. Figure 1 As shown. The positive electrode current collector 1 is a metal foil, for example, an aluminum sheet, a copper sheet, etc. The positive electrode material layer 2 includes a positive electrode material, which may be an existing commonly used positive electrode material. The positive electrode material may be at least one of a layered lithium-transition metal oxide, a spinel-type lithium-transition metal oxide, and an olivine-type lithium-transition metal oxide, for example, olivine-type lithium iron phosphate, layered lithium cobalt oxide, layered lithium manganese oxide, spinel-type lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide. The positive electrode material layer 2 may further include a conductive agent and a binder, which may be a binder and a conductive agent conventionally used in the prior art. The positive electrode material layer is formed by coating the slurry on the positive electrode current collector.

[0053] The composite solid electrolyte membrane 3 is laminated on the surface of the positive electrode material layer 2 away from the positive electrode current collector 1 by hot pressing, so as to obtain the positive electrode composite structure 11. The composite solid electrolyte membrane 3 is a formed layered structure, which means that the composite solid electrolyte membrane 3 is an independent layered structure before being formed on the positive electrode material layer 2. The composite solid electrolyte membrane 3 can be directly laid on the surface of the positive electrode material layer 2 away from the positive electrode current collector 1, rather than being obtained by coating or other methods by placing the coating of the composite solid electrolyte membrane 3 on the surface of the positive electrode material layer 2 and then drying it.

[0054] The composite solid electrolyte membrane 3 includes a polymer material and an inorganic solid electrolyte. Further, the composite solid electrolyte membrane 3 can be a composite membrane composed of a polymer material and an inorganic solid electrolyte. The polymer material can be polyvinylidene fluoride, polymethyl methacrylate, polyethylene oxide, etc. The polymer material can soften due to heat, and the surface forms a local softening, with surface micro-stickiness and thermoplasticity, so the polymer material can also improve the ductility and toughness of the composite solid electrolyte membrane 3. The inorganic solid electrolyte can be lithium lanthanum zirconium oxide, lithium aluminum titanium phosphate, lithium lanthanum titanium oxide, etc. The inorganic solid electrolyte can improve ionic conductivity, avoid lithium dendrite puncture, and improve the mechanical strength of the composite solid electrolyte membrane 3. After the composite solid electrolyte membrane 3 is heated, the surface of the composite solid electrolyte membrane 3 has micro plasticity and micro stickiness. When the pressing is continued, the composite solid electrolyte membrane 3 and the positive electrode material layer 2 have a transitional size of the bonding state, which can achieve a better bonding effect without destroying the surface morphology of the positive electrode material layer 2 and maintaining the material properties. At the same time, the composite solid electrolyte membrane 3 can be shaped after cooling, which is beneficial to the subsequent process operation. Preferably, the thickness of the composite solid electrolyte membrane 3 is between 5 microns and 100 microns.

[0055] See also Figure 2 During the process of hot pressing the composite solid electrolyte membrane 3 and the positive electrode material layer 2, a transition layer 5 is formed between the composite solid electrolyte membrane 3 and the positive electrode material layer 2. The transition layer 5 is an uneven surface interlaced interval structure formed by the contact parts of the composite solid electrolyte membrane 3 and the positive electrode material layer 2 being mutually embedded after the composite solid electrolyte membrane 3 is heated, and this interval is the transition layer 5.

[0056] In the process of hot pressing the composite solid electrolyte membrane 3 and the positive electrode material layer 2, in order to ensure that the composite solid electrolyte membrane 3 and its adjacent positive electrode material layer 2 have a good bonding effect, the thickness of the transition layer 5 is 0.1 micron to 5.0 microns. When the thickness of the transition layer 5 is less than 0.1 micron, since the interval of the transition layer 5 is too thin, in the subsequent hot pressing process of the battery preform 4, the composite solid electrolyte membrane 3 and its adjacent positive electrode sheet 10 or negative electrode sheet 20 cannot achieve good bonding, resulting in poor bonding and peeling. When the thickness of the transition layer 5 is greater than 5.0 microns, since the thickness of the transition layer 5 is too thick, it is equivalent to compressing the insulation protection function, and the positive and negative electrodes are prone to internal short circuits, which affects the safety of the battery. Specifically, the hot pressing process can be performed by a flat pressing device. In this embodiment, the hot pressing temperature is 50°C to 250°C, the pressing speed is about 0.1μm / second, and the fixed force is 0.01Kg / cm 2 ~20.0Kg / cm 2, the moving time of a single pressing is controlled within 10 seconds. It can be understood that the thickness of the positive electrode composite structure 11 formed by the positive electrode sheet 10 and the composite solid electrolyte membrane 3 can be obtained by controlling the hot pressing temperature, the fixed force and the pressing time. Further explanation, the pressing speed can be a constant speed pressurization or a non-constant speed pressurization, such as a deceleration pressurization method from fast to slow.

[0057] In this embodiment, the thickness of the transition layer 5 is 0.1 microns to 5.0 microns. This thickness range can ensure that the electrode sheet adjacent to the composite solid electrolyte membrane 3 has a good surface morphology, while also ensuring that the composite solid electrolyte membrane and the surface of the adjacent electrode sheet are well fitted, so that the formed electrode sheet and the composite solid electrolyte membrane have good cycle performance.

[0058] In step S2, the negative electrode sheet 20 includes a negative electrode current collector 1" and a negative electrode material layer 2' arranged on two opposite surfaces of the negative electrode current collector 1'. The negative electrode material layer 2" includes a negative electrode material, which is an existing commonly used negative electrode material. The negative electrode material can be a carbon material, such as graphite; or it can be a non-carbon material, such as a silicon-carbon composite material. The negative electrode material layer can further include a conductive agent and a binder, and the conductive agent and the binder can both be binders and conductive agents conventionally used in the prior art.

[0059] The composite solid electrolyte membrane 3 is arranged on the surface of the negative electrode sheet 20 to prepare the negative electrode composite structure 12. Specifically, the composite solid electrolyte membrane 3 is heat-pressed and laminated on the surface of the negative electrode material layer away from the negative electrode current collector. The preparation method of the negative electrode composite structure 12 is basically the same as the preparation method of the positive electrode composite structure 11, except that the positive electrode sheet 10 is replaced by the negative electrode sheet 20, which will not be repeated here.

[0060] In step S3, at least one positive electrode composite structure 11 and at least one negative electrode composite structure 12 are stacked to form a battery cell preform 4. Figure 3 and Figure 4, which is a schematic diagram of the structure of the right side view and the front side view of the battery cell preform 4. The number of the positive electrode composite structure 11 and the negative electrode composite structure 12 contained in the battery cell preform 4 can be selected according to actual needs. The function of the composite solid electrolyte membrane 3 is to insulate and separate the positive electrode sheet 10 and the negative electrode sheet 20. The area of ​​the composite solid electrolyte membrane 3 is larger than the area of ​​the positive electrode sheet 10 or the negative electrode sheet 20, that is, the composite solid electrolyte membrane 3 can completely cover the positive electrode sheet 10 or the negative electrode sheet 20. In this way, it can be ensured that when the positive electrode sheet 10 or the negative electrode sheet 20 is offset, the composite solid electrolyte membrane 3 can still isolate the positive electrode sheet 10 and the negative electrode sheet 20. At the same time, since the area of ​​the composite solid electrolyte membrane 3 is larger than the area of ​​the positive electrode sheet 10 or the negative electrode sheet 20, the composite solid electrolyte membrane 3 does not need to be aligned with the positive electrode sheet 10 or the negative electrode sheet 20.

[0061] As long as the positive electrode sheet 10 and the negative electrode sheet 20 in the battery cell preform 4 are insulated, at least one composite solid electrolyte membrane 3 is provided between the positive electrode sheet 10 and the negative electrode sheet 20. That is, when at least the positive electrode composite structure 11 and at least one negative electrode composite structure 12 are stacked, one of the two composite solid electrolyte membranes in the positive electrode composite structure 11 or the negative electrode composite structure 12 can be removed, so that there is one composite solid electrolyte membrane 3 between the positive electrode sheet 10 and the negative electrode sheet 20.

[0062] Therefore, it can be understood that before step S3, the preparation method may include a step of removing the composite solid electrolyte membrane 3 in the positive electrode composite structure 11 or the negative electrode composite structure 12. The position of the removed composite solid electrolyte membrane 3 can be selected according to actual needs, as long as the insulation between the positive electrode sheet 10 and the negative electrode sheet 20 in the battery cell preform 4 is ensured.

[0063] In one embodiment, the battery cell preform 4 is composed of a positive electrode composite structure 11 and a negative electrode composite structure 12 stacked together.

[0064] In another embodiment, the battery cell preform 4 includes a plurality of the positive electrode composite structures 11 and a plurality of the negative electrode composite structures 12 , and the plurality of the positive electrode composite structures 11 and the plurality of the negative electrode composite structures 12 are alternately stacked.

[0065] In step S4, during the pressing of the battery cell preform 4, the battery cell preform 4 is placed horizontally, and pressure is applied to the battery cell preform 4 in the vertical direction. The applied pressure is perpendicular to the surface of the battery cell preform 4, so that the upper and lower surfaces of the battery cell preform 4 can always remain flat during the pressing process. Since the area of ​​the composite solid electrolyte membrane 3 in the battery cell preform 4 is different from the area of ​​the positive electrode sheet 10 or the negative electrode sheet 20, the composite solid electrolyte membrane 3 protrudes from the positive electrode sheet 10 or the negative electrode sheet 20, and the side edge of the battery cell preform 4 is still uneven after pressing. The trimming, shaping and fixing of the battery cell preform 4 is to fold the uneven side edges of the battery cell preform 4 in a uniform direction so that the side edges remain neat, and at the same time fix the structure after the side edges are folded, so as to obtain a battery cell with neat side edges and stable structure. Here, the uneven side edge of the battery cell preform 4 refers to the composite solid electrolyte membrane 3 protruding from the positive electrode sheet 10 or the negative electrode sheet 20 .

[0066] The processes of pressing, trimming, shaping and fixing the battery cell preform can be completed by a battery cell forming device 6. The battery cell forming device 6 includes an upper platform 61, a lower platform 62, a side edge trimming pressure plate 63, and a lower folding plate 64. The upper platform 61 and the lower platform 62 are spaced apart and used to provide pressure to the battery cell preform 4 for pressing. The side edge trimming pressure plate 63 and the lower folding plate 64 are used to trim and shape the side edges of the battery cell preform 4. After trimming and shaping the battery cell preform 4, the battery cell forming device 6 can further glue and fix the battery cell preform 4, so that the structure after the side edge is folded remains stable and does not deform. The specific steps of pressing, trimming and fixing the battery cell preform 4 using the battery cell forming device 6 are as follows:

[0067] S41, positioning, placing and clamping the cell preform 4. Figure 5 The cell preform 4 is horizontally placed on the lower platform 62 of the cell forming device 6, and the upper platform 61 is moved downward to clamp and fix the cell preform 4. To ensure the flatness of the cell preform 4, the pressure is controlled at 5000kg / cm 2 Within this pressure range, the position of the battery cell preform 4 can be fixed and the battery cell preform 4 can be flattened at the same time.

[0068] S42, the side edge pressing plate 63 moves vertically downward to fold the side edge structure of the cell preform 4 downward; the lower folding plate 64 rotates upward to fold the side edge structure upward until it is again attached to the side edge of the cell preform 4. Figure 5As shown, the side edge pressing plate 63 moves vertically downward from the top of the battery cell preform 4 to collect the composite solid electrolyte membrane 3 protruding from the positive electrode sheet 10 or the negative electrode sheet 20. Since the side edge pressing plate 63 has a tapered design, the collection process will not damage the composite solid electrolyte membrane 3. Furthermore, the surface of the side edge pressing plate 63 has an antistatic component and will not cause sticking to the surface of the polymer composite solid electrolyte membrane. When the lower folding plate 64 rotates, it rotates upward with the lower side edge of the battery cell preform 4 as the center until it is vertical to the horizontal direction of the battery cell preform 4 and then stops and is fixed. At this time, the side edge portion collected by the side edge pressing plate 63 is just folded and attached to the side edge of the battery cell preform 4. The upward folding of the composite solid electrolyte membrane 3 by the lower folding plate 64 can confine the composite solid electrolyte membrane 3 to the side area of ​​the battery cell preform 4, so that the composite solid electrolyte membrane 3 will not interfere with the upper and lower surface areas of the battery cell preform 4.

[0069] For further information, please refer to Figure 6 and Figure 7 When the battery cell preform 4 is provided with a pole ear 7, since the pole ear 7 is also provided in the side area of ​​the battery cell preform 4, it is necessary to consider the thickness difference of the pole ear when folding, and design the size of the folding plate according to the position of the pole ear to ensure the safety and aesthetic requirements of the subsequent battery packaging.

[0070] The so-called side edge trimming plate and the lower folding plate of the present invention can be generated into the required size and shape according to the size and shape of the battery, and the purpose is to trim the composite solid electrolyte membrane 3 with protruding size, so as to achieve the purpose of not wasting the internal space of the battery and improving the volume energy density. This embodiment is implemented with a square battery, but it is not limited to square batteries.

[0071] S43, glue and fix the battery cell preform 4. The battery cell forming device 6 may further include a glue supply wheel and a glue clamp (not shown). When the battery cell forming device 6 is sealing and attaching, the glue supply wheel is used to feed the glue and automatically cut it to a specified length, and then the glue clamp is used to clamp it, and the sealing structure 65 is first positioned and attached to the slot below the battery cell preform 4. After the gluing below is completed, the glue clamp continues to move up to a fixed length position, and then the glue clamp is pressed down to complete the gluing. In this way, one gluing point is completed, and the remaining gluing points repeat this cycle until all gluing points are completed.

[0072] The present application provides a method for preparing a lithium-ion battery cell. The composite solid electrolyte membrane 3 can be directly stacked and pressed with the positive electrode sheet 10 and the negative electrode sheet 20 to form a lithium-ion battery cell 100. Before pressing, there is no need to accurately align the positions of the composite solid electrolyte membrane 3 and the positive electrode sheet 10 and the negative electrode sheet 20. A large dimensional error can be allowed. The preparation process is simple, the process is easy to control, and it is suitable for industrial production.

[0073] Please also read Figure 7 and Figure 8 The second embodiment of the present application provides a lithium-ion battery cell 100, which includes the positive electrode composite structure 11 and the negative electrode composite structure 12 in the above-mentioned embodiments, and the positive electrode composite structure 11 and the negative electrode composite structure 12 are stacked, and the positive electrode composite structure 11 includes a positive electrode sheet 10 and a composite solid electrolyte membrane 3 arranged on two opposite surfaces of the positive electrode sheet 10, and the negative electrode composite structure 12 includes a negative electrode sheet 20 and a composite solid electrolyte membrane 3 arranged on two opposite surfaces of the negative electrode sheet 20, and the composite solid electrolyte membrane 3 is a continuous membrane structure and is divided into two parts, a first composite solid electrolyte membrane 31 is located between the positive electrode sheet 10 and the negative electrode sheet 20, and is arranged parallel to the positive electrode sheet 10 and the negative electrode sheet 20, and a second composite solid electrolyte membrane 32 is folded on the side area of ​​the lithium-ion battery cell 100.

[0074] The structure and arrangement of the positive electrode composite structure 11 and the negative electrode composite structure 12 are the same as those of the positive electrode composite structure 11 and the negative electrode composite structure 12 in the first embodiment. The positive electrode composite structure 11 includes a positive electrode sheet 10 and a composite solid electrolyte membrane 3 disposed on two opposite surfaces of the positive electrode sheet, and the negative electrode composite structure 12 includes a negative electrode sheet 20 and a composite solid electrolyte membrane 3 disposed on two opposite surfaces of the negative electrode sheet 20. The structure of the positive electrode sheet 10 and the negative electrode sheet 20" is the same as that of the positive electrode sheet 10 and the negative electrode sheet 20 in the first embodiment, and will not be repeated here.

[0075] For further information, see Fig. 9 and Fig.10 The lithium-ion battery cell 100 includes a plurality of positive electrode composite structures 11 and a plurality of negative electrode composite structures 12, and the plurality of positive electrode composite structures 11 and the plurality of negative electrode composite structures 12 are stacked in an intermittent manner. Specifically, the lithium-ion battery cell 100 includes N positive electrode composite structures 11 and N negative electrode composite structures 12, wherein N≥2, and N can be 2, 3, 4, 5, 6, etc. It can be understood that the value of N is a positive integer and has no upper limit, and the value of N can be set according to the structural size of the lithium-ion battery cell 100.

[0076] The composite solid electrolyte membrane 3 is disposed on both surfaces of the positive electrode sheet 10 and the negative electrode sheet 20. The area of ​​each composite solid electrolyte membrane 3 is larger than that of the positive electrode sheet 10 or the negative electrode sheet 20, that is, the composite solid electrolyte membrane 3 can completely cover the positive electrode sheet 10 or completely cover the negative electrode sheet 20, so as to isolate the positive electrode sheet 10 from the negative electrode sheet 20. Therefore, when the composite solid electrolyte membrane 3 is laminated with the positive electrode sheet 10 and the negative electrode sheet 20, the portion where the composite solid electrolyte membrane 3 overlaps with the positive electrode sheet 10 or the negative electrode sheet 20 is the first composite solid electrolyte membrane 31, and the first composite solid electrolyte membrane 31 is laminated with the positive electrode sheet 10 and the negative electrode sheet 20 and is parallel to each other. The portion of the composite solid electrolyte membrane 3 protruding from the positive electrode sheet 10 or the negative electrode sheet 20 is the second composite solid electrolyte membrane 32. The second composite solid electrolyte membrane 32 extends to the side of the lithium-ion battery cell 100. The second composite solid electrolyte membrane 32 is collected and folded in a uniform direction on the side area of ​​the lithium-ion battery cell 100, so that the overall structure of the lithium-ion battery cell 100 can be made neater and easier to handle later.

[0077] As shown above, arranging the second composite solid electrolyte membrane 32 in the side area of ​​the lithium-ion battery cell 100 is beneficial to the utilization of the internal space of the battery, and will not interfere with the upper and lower planes of the battery cell, thereby improving the overall structure of the battery cell. At the same time, the two-part arrangement of the composite solid electrolyte membrane 3 strengthens the side strength of the battery cell, so that the combination between the battery cell body and the battery packaging aluminum foil will not be interfered with, and the overall structural strength and stability of the battery cell are also improved.

[0078] See also Figure 7 and Fig. 9 Further, the lithium-ion battery cell 100 also includes a sealing structure 65, and the sealing structure 65 includes at least one tape. Each tape extends from the lower plane of the lithium-ion battery cell 100 to the upper plane, and is used to fix the second composite solid electrolyte membrane 32 folded in the side area. When the sealing structure 65 includes a plurality of tapes, the plurality of tapes are arranged on the lithium-ion battery cell 100 at intervals. Specifically, the plurality of tapes are distributed around the lithium-ion battery cell 100, and all extend from the lower plane of the lithium-ion battery cell 100 to the upper plane, providing a fixed support point for the second portion of the solid electrolyte membrane folded in the side area.

[0079] The lithium-ion battery cell provided by the present application includes a composite solid electrolyte membrane, and a part of the structure of the composite solid electrolyte membrane is arranged in the side area of ​​the lithium-ion battery cell. This structure is conducive to the utilization of the internal space of the battery, and at the same time strengthens the side strength of the battery cell, so that the combination between the battery cell body and the battery packaging aluminum foil will not be interfered, and the overall structural strength and stability of the battery cell are improved, so that the lithium-ion battery cell has good cycle performance.

[0080] In addition, those skilled in the art may also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. A method for preparing a lithium ion battery cell, comprising the following steps: S1, providing a positive electrode sheet, and disposing a composite solid electrolyte membrane on two opposite surfaces of the positive electrode sheet to form a positive electrode composite structure; S2, providing a negative electrode sheet, and placing the composite solid electrolyte membrane on two opposite surfaces of the negative electrode sheet to form a negative electrode composite structure; S3, stacking at least one positive electrode composite structure and at least one negative electrode composite structure to form a battery cell preform; S4, pressing the battery cell preform, trimming and fixing the composite solid electrolyte membrane in the battery cell preform.

2. The method for preparing a lithium-ion battery cell according to claim 1, characterized in that: The positive electrode sheet includes a positive electrode collector and a positive electrode material layer arranged on the positive electrode collector, and the composite solid electrolyte membrane is arranged on the surface of the positive electrode material layer by thermal compression lamination. The negative electrode sheet includes a negative electrode collector and a negative electrode material layer arranged on the negative electrode collector, and the composite solid electrolyte membrane is arranged on the surface of the negative electrode material layer by thermal compression lamination.

3. The method for preparing a lithium-ion battery cell according to claim 2, characterized in that: When the composite solid electrolyte membrane is hot pressed onto the positive electrode material layer or the negative electrode material layer, a transition layer is formed between the positive electrode material layer or the negative electrode material layer and the composite solid electrolyte membrane.

4. The method for preparing a lithium-ion battery cell according to claim 3, characterized in that: The transition layer has a thickness of 0.1 micrometer to 5.0 micrometers.

5. The method for preparing a lithium-ion battery cell according to claim 2, characterized in that: The temperature of the hot pressing is 50℃~250℃, and the fixed force is 0.01Kg / cm 2 ~20.0Kg / cm 2 .

6. The method for preparing a lithium-ion battery cell according to claim 2, characterized in that: The pressing speed of the thermal compression bonding may be constant speed pressing or non-constant speed pressing.

7. The method for preparing a lithium-ion battery cell according to claim 1, characterized in that: Before step S3, a step of removing the composite solid electrolyte membrane in the positive electrode composite structure or the negative electrode composite structure is further included, so that there is a composite solid electrolyte membrane between the positive electrode sheet and the negative electrode sheet.

8. The method for preparing a lithium-ion battery cell according to claim 1, characterized in that: During the process of pressing the battery cell preform, the battery cell preform is placed horizontally, and the pressure applied is perpendicular to the surface of the battery cell preform.

9. The method for preparing a lithium-ion battery cell according to claim 1, characterized in that: The process of trimming, shaping and fixing the composite solid electrolyte membrane in the battery cell preform is completed by a battery cell forming device, which includes a side trimming pressing plate and a lower folding plate. The steps of trimming, shaping and fixing the composite solid electrolyte membrane in the battery cell preform include: Positioning, placing, clamping and fixing the battery cell preform; The side edge closing pressing plate moves vertically downward to fold the composite solid electrolyte membrane of the battery cell preform downward; The lower folding plate rotates upward to fold the composite solid electrolyte membrane upward until it is attached to the side edge of the battery cell preform again; The battery cell preform is fixed by gluing.

10. The method for preparing a lithium-ion battery cell according to claim 9, characterized in that: The area of ​​the composite solid electrolyte membrane is larger than that of the positive electrode sheet and the negative electrode sheet. The composite solid electrolyte membrane of the battery cell preform folded downward is the part of the composite solid electrolyte membrane protruding from the positive electrode sheet and the negative electrode sheet.

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