An intrinsically safe battery structure integrated with a dry method polyphenylene sulfide solid-state diaphragm and a preparation method thereof

Abstract

This invention relates to the field of lithium-ion battery technology, specifically to an intrinsically safe battery structure and its preparation method using an integrated dry-process polyphenylene sulfide solid separator. The technical solution includes a continuously folded separator assembly, an electrode assembly, a tab system, and a packaging structure. The continuously folded separator assembly includes a separator body, which is continuously folded in a Z-shape to form multiple interconnected pocket units. The two sides of the Z-folded separator body are sealed by thermo-pressing interlocking. The opening direction of the pocket units alternates between adjacent units. The advantages of this invention are: by using a single separator to continuously fold in a Z-shape to form pocket units, the large amount of independent separator cutting allowance, tape fixing area, and complex packaging materials required in traditional batteries are eliminated, improving production efficiency. Simultaneously, this integrated design significantly improves the alignment accuracy of the electrodes and separator at the structural level, avoiding short circuits caused by exposed edges due to electrode misalignment.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage systems, extremely high requirements have been placed on the energy density, cycle life and intrinsic safety of power batteries. At present, the cell structure of lithium-ion batteries is mainly divided into two categories: wound type and stacked type. Among them, the stacked type structure has gradually become the first choice for high energy density batteries due to its high electrode utilization rate, uniform internal resistance distribution and good expansion control.

[0003] In existing mainstream technologies, the stacking process generally adopts a layer-by-layer cutting and stacking mode of "separator-positive electrode-separator-negative electrode". That is, the production equipment first independently cuts out a rectangular separator, places a positive electrode sheet, then independently cuts out a separator, places a negative electrode sheet, and so on, and finally fixes it into a cell by hot pressing or tape. Although some improved solutions have tried to use double separators for simple U-shaped folding and wrapping, it is still essentially a segmented and discrete assembly method, which has insurmountable systemic defects in battery structure design, production efficiency and inherent safety.

[0004] 1. Efficiency bottleneck and cumulative error caused by discrete stacking: Traditional processes require independent cutting, positioning and placement of each layer of separator and electrode, which is cumbersome and has a low production cycle. Furthermore, the independent stacking of individual cells will cause the positioning error to accumulate linearly with the number of layers. In power cells with tens to hundreds of layers, it is difficult to guarantee the alignment accuracy between the electrode and the separator. It is very easy for the electrode edge to be exposed due to slight misalignment, which will cause internal micro-short circuit. This structure, which lacks overall continuity, inherently has the hidden danger of quality consistency.

[0005] 2. Exposed electrode edges pose insufficient intrinsic safety: In traditional structures, the electrode is merely "sandwiched" between two planar separators, with its four edges completely open and without any physical enclosure. Preventing short circuits relies entirely on the separator's size being larger than the electrode's margin. However, throughout the battery's lifespan, the electrode and separator are prone to relative slippage due to electrolyte swelling, charge / discharge volume changes, and vibration. Once the margin fails, the exposed active material edges directly contact the opposite electrode, a major cause of thermal runaway. Current technology lacks an integrated structure that utilizes the separator's continuity to achieve three-sided sealing of the electrode.

[0006] 3. Safety and performance shortcomings of same-side tab layout: In conjunction with traditional stacking structures, existing batteries mostly use positive and negative tabs to be led out on the same side. This not only leads to the positive and negative tabs being too close together, relying on easily aging insulating auxiliary materials, and having a very high risk of short circuit, but also easily causes the current path to be long, the internal resistance to increase, and the phenomenon of local overheating. The industry urgently needs an architecture that can naturally achieve double-sided current shunting of the tabs through structural innovation and does not require additional insulating components.

[0007] 4. The contradiction between traditional membrane materials and innovative structures: To solve the above problems, the industry has tried to explore the concept of continuously folded battery structures. However, in practical applications, it has been found that traditional polyolefin membrane materials (such as PE and PP wet / dry membranes) severely restrict the implementation of such advanced structures. For example, traditional membranes are relatively soft and have limited toughness. During high-speed continuous folding, microcracks or even breakage can easily occur at the folds, leading to isolation failure. In addition, traditional membranes have low melting points (130℃-165℃). When performing high-temperature hot-pressing interlocking required for the structure, they are prone to over-melting, pore closure, or severe shrinkage, which can damage ion channels or cause loss of dimensional stability. Furthermore, since traditional porous membranes only serve as carriers for liquid electrolytes and cannot serve as solid electrolyte substrates, the rigid contact between traditional materials and electrode interfaces is poor when constructing all-solid-state or semi-solid-state batteries. Moreover, interface integration cannot be achieved through dry processes, which limits further improvement in battery safety.

[0008] In summary, the existing "monolithic stacking" process has inherent drawbacks such as low efficiency and poor safety. Although the concept of continuous folding into a bag structure can theoretically solve these problems, it has not been able to meet the needs of next-generation solid-state batteries due to the limitations of the mechanical and thermal properties of traditional separator materials. Therefore, it is necessary to invent an intrinsically safe battery structure and its preparation method that integrates a dry-process polyphenylene sulfide solid separator. Summary of the Invention

[0009] To achieve the above objectives, the present invention provides the following technical solution: an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator and its preparation method, comprising a continuously folded separator assembly, an electrode assembly, an electrode tab system, and an encapsulation structure;

[0010] The continuously folded diaphragm assembly includes a diaphragm body, which is continuously folded in a Z-shape to form multiple pocket units connected end to end. The two sides of the Z-fold of the diaphragm body are closed by heat-pressing interlocking, so that the pocket unit is in a single-sided open state. The opening direction of the pocket unit changes alternately between adjacent units, facing the first side and the second side of the battery respectively.

[0011] The electrode assembly includes a negative electrode and a positive electrode. A plurality of the negative electrode are disposed in a pocket unit with the opening of the diaphragm body facing the first side, and a plurality of the positive electrode are disposed in a pocket unit with the opening of the diaphragm body facing the second side.

[0012] The electrode system includes a negative electrode and a positive electrode plate. One end of the negative electrode is led out to the first side of the battery, and the other end of the negative electrode is led out to the second side of the battery.

[0013] The encapsulation structure includes an upper heat-sealing sleeve and a lower heat-sealing sleeve, which are respectively sandwiched between the upper and lower sides of the folded diaphragm body.

[0014] Preferably, a hot-melt solidification interface is provided at the edge of the separator body. The two folded sides of the hot-melt solidification interface are closed by hot-pressing interlocking. The two folded ends of the hot-melt solidification interface are both located on the first side of the battery. The two folded ends of the hot-melt solidification interface extend outward to form a continuous Z-shaped crease area close to the first side of the battery. The crease of the continuous Z-shaped fold of the separator body forms the closed bottom edge of the pocket unit. The separator at the crease is not melted, thus maintaining the original pore structure and ion conductivity of the separator.

[0015] Preferably, the surfaces of the negative electrode and the positive electrode have micro-nano rough structures, the surface of the separator body has corresponding microporous structures, and the non-thermal-melting solidification interface region in the middle of the separator body is partially penetrated into the micro-nano rough structures on the surfaces of the negative electrode and the positive electrode in a molten state through a melt interlocking treatment, and forms a micro-mechanical interlocking layer after cooling and solidification.

[0016] Preferably, the arrangement of the negative electrode and the positive electrode follows a "negative-positive-negative" sandwich logic, that is, the two pocket cells located on the outermost side of the battery stack each contain a negative electrode, and the number of negative electrode is always one more than the number of positive electrode.

[0017] Preferably, a negative current collector is provided at the end of the negative electrode sheet near the first side of the battery, and the negative electrode tab is welded to the negative current collector. A positive current collector is provided at the end of the positive electrode sheet near the second side of the battery, and the positive electrode tab is welded to the positive current collector. The positive current collector and the negative current collector are completely disposed on both sides of the separator body in space, without overlapping areas.

[0018] Preferably, the upper heat-sealing sleeve and the lower heat-sealing sleeve are made of aluminum-plastic film or multi-layer composite film. The upper heat-sealing sleeve has an upper heat-pressed sealing area at its edge, and the lower heat-sealing sleeve has a lower heat-pressed sealing area at its edge. The upper heat-pressed sealing area and the lower heat-pressed sealing area are heat-pressed and sealed to the heat-melting solidification interface to form a fully enclosed battery cavity.

[0019] Preferably, the membrane body is a solid or semi-solid membrane formed by hot pressing using solvent-free dry film forming technology. The material of the membrane body is polyphenylene sulfide, and the polyphenylene sulfide membrane has a heat shrinkage initiation temperature greater than 180°C to support the melt interlocking of the hot melt solidification interface without causing overall dimensional distortion.

[0020] The preparation method of the above-mentioned intrinsically safe battery structure with integrated dry polyphenylene sulfide solid membrane includes S1-S6;

[0021] S1: Select high molecular weight linear polyphenylene sulfide powder, mix the pretreated powder, tetrachloro-p-benzoquinone and an appropriate amount of alkaline catalyst, introduce anionic chelating functional group TCBQ grafting using hydrothermal method, disperse the above TCBQ functionalized polyphenylene sulfide powder in lithium-containing solution for pre-lithiation treatment, and finally use solvent-free dry film forming technology to hot press the film to form the separator body and wind it up.

[0022] S2: A continuous roll of diaphragm body is folded continuously in a Z-shape using a folding device to form an array of pocket cells with alternating opening directions. Then, the negative electrode is inserted into the pocket cell with the opening facing the first side, and the positive electrode is inserted into the pocket cell with the opening facing the second side.

[0023] S3: Apply high temperature and high pressure to both sides of the Z-shaped fold of the hot melt solidification interface to cause thermal pressure interlocking between the hot melt solidification interface layers of the diaphragm body, thereby sealing the pocket and fixing the electrode. Then, perform melt interlocking treatment on the middle area of ​​the diaphragm body to form a micro-mechanical interlocking layer between the diaphragm body and the negative and positive electrode sheets after cooling and solidification.

[0024] S4: Bend the negative and positive tabs to the first and second sides respectively, and weld them to the corresponding current collectors;

[0025] S5: The upper heat-sealing sleeve and the lower heat-sealing sleeve are respectively sandwiched on the upper and lower sides of the folded separator body. The upper heat-sealing edge area, the lower heat-sealing edge area and the heat-melting solidification interface are heat-sealed and connected to form the finished battery.

[0026] Preferably, in the hydrothermal method of introducing anionic chelating functional groups in step S1, the mixture needs to be placed in a high-pressure reactor, the temperature is controlled at 160℃-200℃, the pressure is controlled at 2-5MPa, and the reaction time is 6-12 hours. Li+ is introduced during the pre-lithiation process of S1 to form pre-lithiated polyphenylene sulfide.

[0027] Preferably, in the hot pressing process of the hot-melt solidification interface in S3, the hot pressing temperature range is 240°C to 280°C, and the pressure range is 1.0MPa to 5.0MPa. Under these conditions, molecular chain diffusion and entanglement occur at the contact interface of the polyphenylene sulfide membrane layer, forming a glue-free bulk fusion structure.

[0028] The beneficial effects of this invention are:

[0029] 1. The structure of forming pocket units by continuous Z-shaped folding of a single separator eliminates the large amount of independent separator cutting allowance, tape fixing area and complicated packaging materials in traditional batteries, simplifying the production steps and improving production efficiency. At the same time, this integrated design significantly improves the alignment accuracy of the electrode and the separator from the structural level, avoiding short circuits caused by exposed edges due to misalignment of the electrode. It also improves the internal space utilization of the battery, thereby increasing the energy density of the battery with the same volume / weight.

[0030] 2. Through a unique hot-pressing interlocking process, the molten separator material is partially infiltrated into the micro-nano rough structure on the electrode surface, forming a "micro-mechanical interlocking layer". The micro-interlocking structure can firmly lock the electrode and separator like an "anchor", eliminating the relative slippage between the electrode and separator, effectively resisting cycle stress, preventing interface delamination, and thus significantly improving the cycle life and rate performance of the battery. At the same time, this "solid-solid" tight contact completely eliminates the air gap caused by surface unevenness in the traditional stacking process, significantly reducing the interface contact resistance (down to below 10Ω·cm²) and improving ion transport efficiency.

[0031] 3. The design of leading the positive and negative tabs to both sides of the battery reduces the risk of short circuits in the tabs, shortens the current transmission path in the current collector, reduces the ohmic internal resistance, and eliminates the phenomenon of local overheating caused by long current paths and increased internal resistance. This is conducive to high-rate charging and discharging, while avoiding the increase in local thickness and stress concentration caused by leading out on the same side.

[0032] 4. The polyphenylene sulfide (PPS) membrane substrate prepared by the all-dry process completely eliminates the need for flammable and leak-prone liquid electrolytes. The PPS material itself has extremely high thermal stability (melting point > 280℃, thermal decomposition temperature > 500℃) and excellent flame retardancy. Unlike traditional PE / PP membranes, which are prone to shrinkage and short circuits at high temperatures, the dry-process PPS membrane of this invention can maintain dimensional stability and does not melt and collapse even at extreme high temperatures, effectively preventing internal short circuits. This eliminates fire and explosion accidents caused by battery thermal runaway from the source, achieving a truly "intrinsically safe" design.

[0033] 5. Thanks to the high crystallinity and excellent fatigue resistance of the polyphenylene sulfide (PPS) membrane, it can undergo plastic deformation at the creases during continuous folding without brittle fracture, ensuring the stable maintenance of the continuously folded pocket structure. Thanks to the high melting point and extremely low thermal shrinkage of the PPS membrane, it can be hot-pressed at high temperatures, ensuring that the melt has sufficient fluidity to fill the gaps and form strong molecular chain entanglements. After sealing, the pocket unit size remains accurate, and the electrode will not be "squeezed out" due to heat or cause excessive internal stress. Thanks to the suitable melt viscosity and rapid crystallization and solidification capability of the PPS membrane, it can penetrate into the micron-level rough structure of the electrode surface under high temperature and pressure (forming anchor points), and due to its surface tension characteristics, it will not excessively penetrate the nano-level micropores inside the membrane (preserving ion channels). Furthermore, when cooling in the molten state, the crystallization speed is extremely fast, allowing the PPS that has penetrated into the electrode pores to quickly "lock" its shape, forming a rigid mechanical interlocking structure. Attached Figure Description

[0034] Figure 1 A front view of an intrinsically safe battery provided by the present invention;

[0035] Figure 2 An exploded view of the packaging structure provided by this invention;

[0036] Figure 3 This is a schematic diagram of the packaging structure and the structure of the folded diaphragm assembly before hot pressing provided by the present invention;

[0037] Figure 4 This is a schematic diagram of the disassembly of the folded diaphragm assembly provided by the present invention;

[0038] Figure 5 A side view of an intrinsically safe battery provided by the present invention;

[0039] Figure 6 This is a cross-sectional view of the intrinsically safe battery before hot pressing, provided by the present invention.

[0040] Figure 7 This is an exploded side view of an intrinsically safe battery provided by the present invention.

[0041] Figure 8 This is a cross-sectional view of an intrinsically safe battery after hot pressing, provided by the present invention.

[0042] Figure 9 Provided by the present invention Figure 8 Detail image A;

[0043] Figure 10 Provided by the present invention Figure 8 Detail image B;

[0044] Figure 11 This is a schematic diagram of the micromechanical interlocking of the diaphragm body and the electrode sheet provided by the present invention.

[0045] In the figure: 111, diaphragm body; 112, hot-melt solidification interface; 121, upper heat-sealing sheath; 122, upper hot-pressing sealing area; 123, lower heat-sealing sheath; 124, lower hot-pressing sealing area; 131, negative electrode sheet; 132, negative electrode tab; 141, positive electrode sheet; 142, positive electrode tab. Detailed Implementation

[0046] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] like Figure 1 - Figure 8 As shown, an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator and its preparation method are disclosed, including a continuously folded separator assembly, an electrode assembly, an electrode tab system, and an encapsulation structure.

[0048] The continuously folded diaphragm assembly includes a diaphragm body 111, which is continuously folded in a Z-shape to form multiple pocket units connected end to end. The two sides of the Z-fold of the diaphragm body 111 are closed by heat-pressing interlocking, so that the pocket unit is in a single-sided open state. The opening direction of the pocket unit alternates between adjacent units, facing the first side and the second side of the battery respectively.

[0049] The electrode assembly includes a negative electrode 131 and a positive electrode 141. A plurality of negative electrode 131 are disposed in a pocket unit of the diaphragm body 111 with the opening facing the first side, and a plurality of positive electrode 141 are disposed in a pocket unit of the diaphragm body 111 with the opening facing the second side.

[0050] The electrode system includes a negative electrode 132 and a positive electrode 141. One end of the negative electrode 132 is led out to the first side of the battery, and the other end of the negative electrode is led out to the second side of the battery.

[0051] The encapsulation structure includes an upper heat-sealing sleeve 121 and a lower heat-sealing sleeve 123, which are respectively sandwiched on the upper and lower sides of the folded diaphragm body 111.

[0052] In the above embodiments, it should be noted that the membrane body 111 is a polyphenylene sulfide membrane substrate prepared by a completely dry process, which completely eliminates the flammable and leaky liquid electrolyte. The polyphenylene sulfide material itself has extremely high thermal stability (melting point > 280℃, thermal decomposition temperature > 500℃) and excellent flame retardancy. Unlike traditional PE / PP membranes, which are prone to shrinkage and short circuits at high temperatures, the dry PPS membrane of the present invention can still maintain dimensional stability at extreme high temperatures and does not melt and collapse, effectively preventing internal short circuits. It eliminates fire and explosion accidents caused by battery thermal runaway from the source and achieves a true "intrinsically safe" design.

[0053] Meanwhile, thanks to the high crystallinity and excellent fatigue resistance of the polyphenylene sulfide separator, it can undergo plastic deformation at the crease without brittle fracture during continuous folding, ensuring the stable maintenance of the continuous folding pocket structure. By adopting a structure that forms pocket units through continuous Z-shaped folding of a single separator, the large amount of independent separator cutting allowance, tape fixing area and complex packaging materials in traditional batteries are eliminated, simplifying the production steps and improving production efficiency. Moreover, this integrated design significantly improves the alignment accuracy of the electrode and the separator from a structural perspective, avoiding short circuits caused by exposed edges due to electrode misalignment, and also improves the internal space utilization of the battery, thereby increasing the energy density of the battery with the same volume / weight.

[0054] The diaphragm body 111 adopts a Z-shaped reciprocating folding process, and its key geometric parameters and control logic are as follows:

[0055] (1) Folding pitch Set as: ;

[0056] in: This represents the total thickness of the electrode assembly; To allow for a clearance, its value ranges from 0.1mm to 0.3mm;

[0057] Reserved gap Its existence has a dual key role:

[0058] Firstly, it is used to accommodate the micro-adjustment of volume when the electrode and the diaphragm are micro-interlocked during the hot pressing process, so as to avoid the active material of the electrode being crushed or the current collector being deformed due to interference fit.

[0059] Secondly, it prevents the internal components of the battery from becoming loose due to excessive gaps, and ensures the stability of the relative position of the electrode and the separator during long-term cyclic vibration.

[0060] (2) The inner radius of curvature R at the fold is controlled within the range of 0.5mm to 1.5mm;

[0061] This specific radius design fully utilizes the high toughness of polyphenylene sulfide material:

[0062] On the one hand, it avoids stress concentration caused by sharp-angle folding, prevents micro-cracks or structural damage to the diaphragm at the fold, and ensures insulation integrity; on the other hand, the moderate rebound characteristics can maintain the natural opening of the pocket opening, forming a stable "self-supporting" entrance, which greatly facilitates the rapid and accurate insertion of the electrode sheet by subsequent automated equipment and improves production efficiency.

[0063] like Figure 1 - Figure 7 and Figure 11As shown, an intrinsically safe battery structure and its preparation method using an integrated dry-process polyphenylene sulfide solid separator are disclosed. The structure further includes a hot-melt solidification interface 112 at the edge of the separator body 111. The two folded sides of the hot-melt solidification interface 112 are sealed by thermal interlocking. The two folded ends of the hot-melt solidification interface 112 are located on the first side of the battery. The folded ends of the hot-melt solidification interface 112 extend outwards to form a continuous Z-shaped crease region near the first side of the battery. The creases of the continuous Z-shaped folds of the separator body 111 form the closed bottom edge of the pocket unit. The separator at the creases is not melted, maintaining the original pore structure and ion conductivity of the separator. The surfaces of the negative electrode 131 and the positive electrode 141 have micro-nano rough structures, and the surface of the separator body 111 has corresponding microporous structures. The non-hot-melt solidification interface 112 region in the middle of the separator body 111 is sealed by a hot-melt interlocking interface. The membrane partially penetrates into the micro-nano rough structure on the surface of the negative electrode 131 and the positive electrode 141 in the molten state, and forms a micro-mechanical interlocking layer after cooling and solidification. The separator body 111 is a solid or semi-solid separator formed by hot pressing using solvent-free dry film forming technology. The material of the separator body 111 is polyphenylene sulfide. The polyphenylene sulfide separator has a heat shrinkage initiation temperature greater than 180°C to support the molten interlocking of the hot melt solidification interface 112 without causing overall dimensional distortion. The materials of the upper heat-sealing sleeve 121 and the lower heat-sealing sleeve 123 are aluminum-plastic film or multi-layer composite film. The upper heat-sealing sleeve 121 has an upper hot-pressed sealing area 122 at its edge, and the lower heat-sealing sleeve 123 has a lower hot-pressed sealing area 124 at its edge. The upper hot-pressed sealing area 122 and the lower hot-pressed sealing area 124 are hot-pressed and sealed with the hot melt solidification interface 112 to form a fully enclosed battery cavity.

[0064] In the above embodiments, it should be noted that the specific process parameters for the melt interlocking treatment in the middle of the diaphragm body 111 are as follows:

[0065] Hot pressing temperature: controlled between 285℃ and 310℃; this temperature range is slightly higher than the melting point of PPS (about 280℃) to ensure that the membrane surface reaches a low-viscosity molten state to penetrate into the micropores of the electrode, but is lower than the thermal decomposition temperature of PPS (500℃) to avoid material degradation; if the temperature is lower than 280℃, the melting will be insufficient and effective intercalation will not be formed; if it is higher than 320℃, it may cause the membrane body to soften and deform excessively;

[0066] Hot pressing pressure: controlled at 2.0 to 5.0 MPa; this pressure is sufficient to drive the melt to penetrate into the micron-sized pores on the surface of the electrode (depth of about 5-15 μm), while avoiding excessive pressure that could cause a significant decrease in the porosity of the diaphragm body or the shedding of the active material from the electrode.

[0067] Holding time: Controlled between 3 and 10 seconds; allow sufficient time for the melt to flow and fill, and utilize the rapid crystallization properties of PPS to complete the initial solidification and shaping before the end of the holding time.

[0068] Through a unique hot-press interlocking process, the molten separator material is partially infiltrated into the micro-nano rough structure on the electrode surface, forming a "micro-mechanical interlocking layer". The micro-interlocking structure can firmly lock the electrode and separator like an "anchor", eliminating the relative slippage between the electrode and separator, effectively resisting cycle stress, and preventing interface delamination, thereby significantly improving the cycle life and rate performance of the battery. At the same time, this "solid-solid" tight contact completely eliminates the air gap caused by surface unevenness in the traditional stacking process, significantly reducing the interface contact resistance (down to below 10Ω·cm²) and improving ion transport efficiency.

[0069] Meanwhile, thanks to the high melting point and extremely low thermal shrinkage rate of the polyphenylene sulfide (PPS) membrane, it can be hot-pressed at higher temperatures, ensuring that the melt has sufficient fluidity to fill the gaps and form a strong molecular chain entanglement. After sealing, the size of the pocket unit remains accurate, and the electrode will not be "squeezed out" due to heat or cause excessive internal stress. Thanks to the suitable melt viscosity and rapid crystallization and solidification ability of the PPS membrane, it can penetrate into the micron-level rough structure on the surface of the electrode under high temperature and pressure (forming anchor points). Due to its surface tension characteristics, it will not excessively penetrate into the nano-level micropores inside the membrane (preserving ion channels). Furthermore, when cooling in the molten state, the crystallization speed is extremely fast, allowing the PPS that has penetrated into the pores of the electrode to quickly "lock" its shape and form a hard mechanical interlocking structure.

[0070] The micromechanical interlocking layer formed by this invention has the following characteristics:

[0071] (1) Penetration depth: The molten PPS material penetrates to a depth of 3 μm to 12 μm into the rough structure of the surface of the negative electrode 131 and the positive electrode 141 (approximately 1.5 to 2 times the surface roughness Ra value of the electrode).

[0072] (2) Interface transition zone: A dense transition layer with a thickness of about 1 μm to 3 μm is formed between the electrode and the diaphragm. There is no air gap in this layer.

[0073] (3) Pore retention rate: The porosity of the membrane body region beyond 5 μm from the interface is maintained at 35% to 45% (consistent with the original membrane), proving that the melt penetration is limited to the shallow surface layer of the interface and does not block the ion transport channels;

[0074] (4) Adhesion test: Through the 180-degree peel test, the interfacial peel strength between the electrode and the separator reached more than 6.5 N / m, and the failure mode was 'cohesive failure' (i.e., internal fracture of the active material layer) rather than 'interfacial debonding', which proved the firmness of the mechanical interlocking.

[0075] like Figure 3 , Figure 4 , Figure 6 - Figure 10 As shown, an intrinsically safe battery structure and its preparation method with an integrated dry-process polyphenylene sulfide solid separator are disclosed. The structure further includes a negative electrode 131 and a positive electrode 141 arranged according to a "negative-positive-negative" sandwich logic. Specifically, the two outermost pocket units of the battery stack each contain a negative electrode 131, and the number of negative electrode 131s is always one more than the number of positive electrode 141s. A negative current collector is provided at the end of the negative electrode 131 closest to the first side of the battery, and a negative electrode tab 132 is welded to the negative current collector. A positive current collector is provided at the end of the positive electrode 141 closest to the second side of the battery, and a positive electrode tab 142 is welded to the positive current collector. The positive and negative current collectors are completely positioned on both sides of the separator body 111 without any overlapping areas.

[0076] In the above embodiments, it should be noted that the positive electrode tab 142 and the negative electrode tab 132 are respectively led out from opposite sides of the battery body:

[0077] On the negative electrode side, even-numbered pocket cells accommodate negative electrode plates 131, and the tabs of all negative electrode plates 131 extend toward the opposite side (defined as the first side of the battery) and converge to the negative electrode busbar.

[0078] On the positive electrode side, the odd-numbered pocket cells of the continuously folded separator strip accommodate the positive electrode 141. The tabs of all the positive electrode 141 extend toward the same side (defined as the second side of the battery) and converge to a positive electrode busbar by ultrasonic welding.

[0079] By leading the positive and negative tabs to both sides of the battery respectively, the risk of tab short circuit is reduced, the current transmission path in the current collector is shortened, the ohmic internal resistance is reduced, and the local overheating caused by the long current path and increased internal resistance is eliminated, which is conducive to high-rate charging and discharging. At the same time, it avoids the local thickness increase and stress concentration caused by leading out on the same side.

[0080] Furthermore, at the edge where the tab protrudes from the diaphragm pocket, a thickened PPS hot melt adhesive ring or a reinforced sealing ring formed by local secondary hot pressing is provided to prevent the diaphragm from being punctured due to stress concentration at the base of the tab, while ensuring absolute airtightness at that point.

[0081] The method for preparing an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to the present invention is as follows:

[0082] 1. Preparation of solid polyphenylene sulfide membrane: High molecular weight linear polyphenylene sulfide powder was selected, and the pretreated powder, tetrachloro-p-benzoquinone and an appropriate amount of alkaline catalyst were mixed. The mixture was then placed in a high-pressure reactor, with the temperature controlled at 160℃-200℃, the pressure controlled at 2-5MPa, and the reaction time at 6-12 hours. The anionic chelating functional group TCBQ was introduced by hydrothermal method for grafting. The above TCBQ functionalized polyphenylene sulfide powder was dispersed in a lithium-containing solution, and Li+ was introduced by pre-lithiation treatment to form pre-lithiation polyphenylene sulfide. Finally, the membrane body 111 was formed by hot pressing and winding using solvent-free dry film forming technology.

[0083] 2. Fabrication of Intrinsically Safe Battery: A continuous roll of separator body 111 is selected and continuously folded in a Z-shape using a folding device to form an array of pocket cells with alternating opening directions. Next, a negative electrode 131 is inserted into a pocket cell with its opening facing the first side, and a positive electrode 141 is inserted into a pocket cell with its opening facing the second side. Then, a hot-pressing device is used to apply high temperature and high pressure to both sides of the Z-shaped folds of the hot-melt solidification interface 112. The hot-pressing temperature is controlled between 240°C and 280°C, and the pressure is controlled between 1.0 MPa and 5.0 MPa, causing hot-pressing interlocking between the layers of the hot-melt solidification interface 112 of the separator body 111. The bag is sealed and the electrode is fixed. Then, a hot pressing device is used to perform a melt interlocking treatment on the middle area of ​​the separator body 111, so that a micro-mechanical interlocking layer is formed between the separator body 111 and the negative electrode 131 and the positive electrode 141 after cooling and solidification. Then, the negative electrode tab 132 and the positive electrode tab 142 are bent out to the first side and the second side respectively, and welded to the corresponding current collector. The upper heat-sealing sleeve 121 and the lower heat-sealing sleeve 123 are respectively sandwiched on the upper and lower sides of the folded separator body 111. The upper heat-sealing edge area 122, the lower heat-sealing edge area 124 and the hot-melt solidification interface 112 are hot-pressed and sealed together by the hot pressing device to form the finished battery.

[0084] The above description is merely a preferred embodiment of the present invention. Any person skilled in the art can modify the present invention or modify it into an equivalent technical solution using the technical solutions described above. Therefore, any simple modifications or equivalent substitutions made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An intrinsically safe battery structure integrating a dry-processed polyphenylene sulfide solid membrane, characterized in that: Includes a continuously folded diaphragm assembly, electrode assembly, tab system, and packaging structure; The continuously folded diaphragm assembly includes a diaphragm body, which is continuously folded in a Z-shape to form multiple pocket units connected end to end. The two sides of the Z-fold of the diaphragm body are closed by heat-pressing interlocking, so that the pocket unit is in a single-sided open state. The opening direction of the pocket unit changes alternately between adjacent units, facing the first side and the second side of the battery respectively. The electrode assembly includes a negative electrode and a positive electrode. A plurality of the negative electrode are disposed in a pocket unit with the opening of the diaphragm body facing the first side, and a plurality of the positive electrode are disposed in a pocket unit with the opening of the diaphragm body facing the second side. The electrode system includes a negative electrode and a positive electrode plate. One end of the negative electrode is led out to the first side of the battery, and the other end of the negative electrode is led out to the second side of the battery. The encapsulation structure includes an upper heat-sealing sleeve and a lower heat-sealing sleeve, which are respectively sandwiched between the upper and lower sides of the folded diaphragm body.

2. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 1, characterized in that: A hot-melt solidification interface is provided at the edge of the separator body. The two folded sides of the hot-melt solidification interface are sealed by hot-pressing interlocking. The two folded ends of the hot-melt solidification interface are both located on the first side of the battery. The two folded ends of the hot-melt solidification interface extend outward to form a continuous Z-shaped crease area close to the first side of the battery. The crease of the continuous Z-shaped fold of the separator body forms the closed bottom edge of the pocket unit. The separator at the crease is not melted, thus maintaining the original pore structure and ion conductivity of the separator.

3. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid membrane according to claim 2, characterized in that: The surfaces of the negative and positive electrodes have micro-nano rough structures, and the surface of the membrane body has a corresponding microporous structure. The non-thermal-melting solidification interface region in the middle of the membrane body is partially penetrated into the micro-nano rough structures on the surfaces of the negative and positive electrodes in a molten state through a melt interlocking process. After cooling and solidification, a micro-mechanical interlocking layer is formed.

4. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 1, characterized in that: The arrangement of the negative and positive electrodes follows a "negative-positive-negative" sandwich logic, meaning that the two outermost pocket cells of the battery stack each contain a negative electrode, and the number of negative electrodes is always one more than the number of positive electrodes.

5. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 1, characterized in that: The negative electrode sheet is provided with a negative current collector at one end near the first side of the battery, and the negative electrode tab is welded to the negative current collector. The positive electrode sheet is provided with a positive current collector at one end near the second side of the battery, and the positive electrode tab is welded to the positive current collector. The positive current collector and the negative current collector are completely arranged on both sides of the separator body in space, without overlapping areas.

6. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 2, characterized in that: The upper heat-sealing sheath and the lower heat-sealing sheath are made of aluminum-plastic film or multi-layer composite film. The upper heat-sealing sheath has an upper heat-pressed sealing area at its edge, and the lower heat-sealing sheath has a lower heat-pressed sealing area at its edge. The upper heat-pressed sealing area and the lower heat-pressed sealing area are heat-pressed and sealed to the heat-melting solidification interface to form a fully enclosed battery cavity.

7. The intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 1, characterized in that: The membrane body is a solid or semi-solid membrane formed by hot pressing using solvent-free dry film forming technology. The material of the membrane body is polyphenylene sulfide. The polyphenylene sulfide membrane has a heat shrinkage initiation temperature greater than 180°C to support the melt interlocking of the hot melt solidification interface without causing overall dimensional distortion.

8. A method for preparing an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator as described in any one of claims 1-7, characterized in that: Including S1-S6; S1: Select high molecular weight linear polyphenylene sulfide powder, mix the pretreated powder, tetrachloro-p-benzoquinone and an appropriate amount of alkaline catalyst, introduce anionic chelating functional groups (TCBQ grafting) using hydrothermal method, disperse the above TCBQ functionalized polyphenylene sulfide powder in a lithium-containing solution for pre-lithiation treatment, and finally use solvent-free dry film forming technology to hot press the film to form the separator body and roll it up. S2: A continuous roll of diaphragm body is folded continuously in a Z-shape using a folding device to form an array of pocket cells with alternating opening directions. Then, the negative electrode is inserted into the pocket cell with the opening facing the first side, and the positive electrode is inserted into the pocket cell with the opening facing the second side. S3: Apply high temperature and high pressure to both sides of the Z-shaped fold of the hot melt solidification interface to cause thermal pressure interlocking between the hot melt solidification interface layers of the diaphragm body, thereby sealing the pocket and fixing the electrode. Then, perform melt interlocking treatment on the middle area of ​​the diaphragm body to form a micro-mechanical interlocking layer between the diaphragm body and the negative and positive electrode sheets after cooling and solidification. S4: Bend the negative and positive tabs to the first and second sides respectively, and weld them to the corresponding current collectors; S5: The upper heat-sealing sleeve and the lower heat-sealing sleeve are respectively sandwiched on the upper and lower sides of the folded separator body. The upper heat-sealing edge area, the lower heat-sealing edge area and the heat-melting solidification interface are heat-sealed and connected to form the finished battery.

9. The method for preparing an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 8, characterized in that: In the hydrothermal method of introducing anionic chelating functional groups in S1, the mixture needs to be placed in a high-pressure reactor, with the temperature controlled at 160℃-200℃, the pressure controlled at 2-5MPa, and the reaction time at 6-12 hours. Li+ is introduced during the pre-lithiation process of S1 to form pre-lithiated polyphenylene sulfide.

10. The method for preparing an intrinsically safe battery structure with an integrated dry-process polyphenylene sulfide solid separator according to claim 8, characterized in that: In the hot pressing process of the hot-melt solidification interface in S3, the hot pressing temperature range is 240℃ to 280℃, and the pressure range is 1.0MPa to 5.0MPa. Under these conditions, molecular chain diffusion and entanglement occur at the contact interface of the polyphenylene sulfide membrane layer, forming a glue-free bulk fusion structure.

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