Cylindrical battery partition diaphragm as well as preparation method and application thereof

Abstract

The invention provides a cylindrical battery partition diaphragm as well as a preparation method and application thereof. The cylindrical battery partition diaphragm is wound along the winding direction from the winding head to the winding tail, the winding direction is taken as the transverse direction, and the direction perpendicular to the winding direction is taken as the axial direction; the cylindrical battery partition diaphragm is sequentially divided into a rolling head area and a rolling tail area along the transverse direction; the tail rolling area is sequentially divided into a first edge area, a middle area and a second edge area in the axial direction; the diaphragm comprises a high-porosity flow guide area and a low-porosity stable area, the flow guide area comprises a winding head area and a middle area, and the stable area comprises a first edge area and a second edge area. The high-porosity diaphragm is arranged in the area where infiltration and ion conduction are difficult to enhance the diversion effect, the low-porosity diaphragm with high stability and high strength is arranged in other areas to improve the mechanical strength, it is ensured that electrolyte is evenly distributed in the diaphragm, the electrolyte wettability and the ion conductivity of the diaphragm are improved, and the service life of the diaphragm is prolonged. Therefore, the electrochemical performance and the safety performance of the battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a cylindrical battery partitioned separator, a preparation method and application thereof. BACKGROUND

[0002] When a cylindrical battery uses a silicon negative electrode system, due to a large volume change in the process of charge and discharge cycles, the internal pressure of the roll core frequently increases and decreases during use, which often leads to periodic extrusion and infiltration of electrolyte, and the speed of infiltration limits the performance of the battery to some extent. High-porosity separator is one of the key components of cylindrical lithium batteries, and the porosity design has an important influence on the performance of the battery. High porosity of the separator can provide more ion transmission channels, reduce the diffusion resistance of lithium ions, better absorb and retain electrolyte, ensure full contact between the electrode and the electrolyte, and facilitate infiltration.

[0003] However, the mechanical strength of the high-porosity separator is low, and if the entire separator has high porosity, the mechanical strength of the separator may decrease, and tearing may occur, increasing the risk of short circuit and thermal runaway of the battery. Moreover, the stability of the high-porosity separator is poor, and it is easily damaged at high temperatures, leading to contact between the positive and negative electrodes, causing short circuit, and also reducing the safety of the battery. SUMMARY

[0004] The main purpose of the present application is to provide a cylindrical battery partitioned separator, a preparation method and application thereof, to solve the problem that the cylindrical battery separator in the prior art is difficult to optimize the wettability and ion conductivity while ensuring the overall mechanical strength and stability, thereby making it difficult for the cylindrical battery to balance good electrochemical performance and high safety.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a cylindrical battery partitioned separator is provided, which is wound from the roll head to the roll tail along the winding direction, with the winding direction being the transverse direction and the axial direction being perpendicular to the winding direction. Along the transverse direction, the cylindrical battery partitioned separator is sequentially divided into a roll head region and a roll tail region. Along the axial direction, the roll tail region is sequentially divided into a first edge region, a middle region and a second edge region. The cylindrical battery partitioned separator includes a flow guide region and a stable region, the flow guide region includes the roll head region and the middle region, and the stable region includes the first edge region and the second edge region. The porosity of the flow guide region > the porosity of the stable region.

[0006] The technical scheme of the application maximizes the overall benefit of the diaphragm by the partition design of the diaphragm, in the area close to the outside of the roll core, including the two end faces of the roll tail, the electrolyte is easy to soak and conduct ions, and the diaphragm with slightly lower porosity is used to increase the stability and mechanical strength of the diaphragm. In the area close to the inside of the roll core, including the roll head and the axial middle part, the electrolyte is difficult to soak and conduct ions, and the diaphragm with higher porosity is used to increase the flow guiding capacity of the diaphragm. The cylindrical battery partition diaphragm of the application sets high-porosity diaphragm in the area where the soaking and ion conduction are difficult to strengthen the flow guiding effect, sets low-porosity diaphragm with high stability and high strength in other areas, and the two areas work together to solve the deficiency of the high-porosity diaphragm in mechanical strength and stability, while ensuring the uniform distribution of the electrolyte in the diaphragm, improving the electrolyte soaking property and ion conductivity of the diaphragm, and thus improving the electrochemical performance and safety performance of the battery.

[0007] Further, the porosity of the flow guiding area is greater than the porosity of the stability area, and the difference is 20-50%; and / or the porosity of the flow guiding area is 50-70%; and / or the porosity of the stability area is 10-40%, which can better balance the electrical conductivity and mechanical stability of the diaphragm.

[0008] Further, the percentage of the roll head area in the transverse length of the cylindrical battery partition diaphragm is 20-50%; and / or the percentage of the middle area in the axial length of the cylindrical battery partition diaphragm is 20-40%, which can promote the transmission of lithium ions in the difficult-to-soak area, make the distribution of electrolyte in the roll core more uniform, further reduce the local dryness phenomenon, and thus improve the electrical conductivity, charge and discharge efficiency and overall electrochemical stability of the battery.

[0009] Further, the percentage of the first edge area in the transverse length of the cylindrical battery partition diaphragm is 50-80%; and / or the percentage of the second edge area in the transverse length of the cylindrical battery partition diaphragm is 50-80%; and / or the percentage of the first edge area in the axial length of the cylindrical battery partition diaphragm is 30-40%; and / or the percentage of the second edge area in the axial length of the cylindrical battery partition diaphragm is 30-40%; and / or the percentage of the first edge area in the transverse length of the cylindrical battery partition diaphragm is the same as the percentage of the second edge area in the transverse length of the cylindrical battery partition diaphragm; and / or the percentage of the first edge area in the axial length of the cylindrical battery partition diaphragm is the same as the percentage of the second edge area in the axial length of the cylindrical battery partition diaphragm; and / or the area of the first edge area is the same as the area of the second edge area, to further improve the uniformity and stability of the mechanical properties of the diaphragm.

[0010] Further, the area ratio of the flow guide area to the stable area is (1-1.5):1. Under the above conditions, it is more conducive to promoting the infiltration of electrolyte and the rapid diffusion of lithium ions by using the high porosity of the flow guide area, while enhancing the mechanical strength and heat resistance of the separator by using the low porosity of the stable area, so as to simultaneously improve the strength of the separator and the electrolyte infiltration effect.

[0011] Further, the base film material of the cylindrical battery partitioned separator is a polyolefin separator or a non-woven fabric separator; wherein the polyolefin separator is a polyethylene separator, a polypropylene separator or a PE / PP composite separator; and / or the non-woven fabric separator is an aramid fiber separator or a polyimide separator; optionally, the surface of the base film material of the stable area further has a coating layer, and the coating layer includes one or more of a ceramic coating layer, an aluminum oxide coating layer and a silicon dioxide coating layer, which is conducive to balancing the mechanical strength of the base material and the temperature resistance and liquid affinity of the functional layer, and is suitable for high-end power batteries, long-life energy storage and other scenarios that require high safety and rate.

[0012] According to another aspect of the present application, a preparation method of the cylindrical battery partitioned separator of the present application is provided, comprising the following steps: step S1, preparing a mask plate, the mask plate comprising an opening area and a covered area, the shape of the opening area being the same as that of the stable area of the cylindrical battery partitioned separator, and the shape of the covered area being the same as that of the flow guide area of the cylindrical battery partitioned separator; step S2, placing the mask plate above the base film and performing electron beam irradiation to obtain the cylindrical battery partitioned separator. The above preparation method is simple and easy to operate, and the prepared separator has a stable area and a flow guide area, which can improve the performance balance of the separator, ensure uniform distribution of electrolyte inside the separator, and avoid local dryness, thereby improving the electrical performance of the battery while maximizing the safety of the battery.

[0013] Further, the porosity of the base film is 50-80%; and / or the thickness of the base film is 15-25 pm, and the width is 80-100 mm; and / or the material of the mask plate includes one or more of titanium alloy, stainless steel, aluminum oxide and polyether ether ketone, which is conducive to further optimizing the basic performance of the separator, promoting efficient ion conduction, making the adaptability of the separator in the battery structure better, and enhancing the mechanical stability of the separator in high energy density batteries, while being conducive to adjusting the porosity through electron beam irradiation.

[0014] Further, the acceleration voltage of the electron beam irradiation is 0.5-3 MeV, the absorbed dose is 20-100 kGy, the dose rate is 1-10 kGy / s, and the treatment time is the absorbed dose divided by the dose rate; and / or the base film processing speed of the electron beam irradiation is 5-20 m / min; and / or the environment of the electron beam irradiation includes a vacuum atmosphere or a protective atmosphere, and the protective atmosphere includes N2 atmosphere and / or Ar atmosphere. The above irradiation parameters are conducive to promoting the precise crosslinking of the molecular structure of the base film in the stable area, thereby effectively improving the mechanical strength and thermal stability of this area.

[0015] According to another aspect of the present application, there is provided a cylindrical battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, the separator comprising the above-mentioned cylindrical battery zoned separator of the present application, which can take into account both high conductivity and high safety of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of the specification, are included to provide a further understanding of the application and are incorporated herein for explanation by referring to the exemplary embodiments thereof. In the drawings:

[0017] Figure 1 A separator area plan view of a cylindrical battery according to Embodiment 1 of the present application is shown;

[0018] Figure 2 A separator area zoning schematic view of a cylindrical battery according to Embodiment 1 of the present application is shown;

[0019] Figure 3 A perspective schematic view of a cylindrical battery according to Embodiment 1 of the present application is shown.

[0020] In the above-mentioned drawings, the following reference signs are used:

[0021] 10, beginning of the roll; 20, end of the roll; 1, beginning of the roll zone; 2, middle zone; 31, first edge zone; 32, second edge zone; A, schematic of the first edge zone in the transverse length of the cylindrical battery zoned separator; B1, schematic of the first edge zone in the axial length of the cylindrical battery zoned separator; B2, schematic of the second edge zone in the axial length of the cylindrical battery zoned separator. DETAILED DESCRIPTION

[0022] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As described in the background of the present application, there is a problem in the prior art that the cylindrical battery separator is difficult to optimize wettability and ion conductivity while ensuring overall mechanical strength and stability, thereby making it difficult for the cylindrical battery to take into account both good electrochemical performance and high safety. In order to solve the above-mentioned problem, in a typical embodiment of the present application, a cylindrical battery zoned separator is provided, which is wound from the beginning of the roll to the end of the roll along the winding direction, with the winding direction being the transverse direction and the direction perpendicular to the winding direction being the axial direction; along the transverse direction, the cylindrical battery zoned separator is sequentially divided into the beginning of the roll zone and the end of the roll zone; along the axial direction, the end of the roll zone is sequentially divided into the first edge zone, the middle zone and the second edge zone; the cylindrical battery zoned separator comprises a flow guide zone and a stabilization zone, the flow guide zone comprises the beginning of the roll zone and the middle zone, and the stabilization zone comprises the first edge zone and the second edge zone; the porosity of the flow guide zone > the porosity of the stabilization zone.

[0024] The porosity directly determines the performance of the separator in ion conduction and mechanical isolation. Too low porosity means that there are too few and too narrow channels in the separator for electrolyte filling and lithium ion transmission, sacrificing ion "passage" and ensuring mechanical strength, but leading to the deterioration of electrochemical performance. Too high porosity means that the separator becomes too "sparse", its skeleton structure is weakened, the mechanical strength decreases, and the short circuit risk increases. The present application provides a new partition design of the separator for cylindrical batteries, which is divided into a flow guide area and a stable area. Around the virtual central axis, the separator of the cylindrical battery is wound from the beginning to the end along a direction, the winding direction is transverse, and the axial direction perpendicular to the winding direction is the direction of the virtual central axis. The beginning part of the winding direction close to the central hole along the transverse direction of the winding core and the middle part of the axial direction of the winding core, i.e. the flow guide area, including the beginning area and the middle area, the electrolyte infiltration and ion conduction in this area are difficult, a separator with high porosity is used to increase the flow guide ability of the separator, including the infiltration ability and the ion diffusion ability, to promote infiltration and lithium ion transmission path is shorter, the diffusion resistance is smaller. In the flow guide area, the use of high-porosity separator material helps to promote the full infiltration of electrolyte and the effective transmission of lithium ions, especially in the area difficult to infiltrate inside the winding core, the increase of porosity directly reduces the diffusion resistance of lithium ions, thereby optimizing the electrochemical performance of the battery, such as capacity retention rate.

[0025] In the area close to the outside of the winding core, including the end and the two end faces, i.e. the stable area, including the first edge area and the second edge area, the transmission path is shorter, the electrolyte infiltration and ion conduction are easier, the porosity redundancy is reduced to obtain a high-strength separator, and a separator with slightly lower porosity is used to increase the stability and mechanical strength of the separator. In the stable area, the porosity of the separator is relatively low, these areas are located outside the winding core, the electrolyte infiltration is relatively easy, the lower porosity helps to increase the mechanical strength and thermal stability of the separator, especially during battery assembly and cycling, which can effectively prevent the separator from tearing and structural damage at high temperature, thereby significantly reducing the risk of battery short circuit and improving the overall safety of the battery.

[0026] In summary, the partitioned separator of the cylindrical battery of the present application maximizes the overall benefit of the separator through the partition design of the stable area and the flow guide area, sets high-porosity separators in areas where infiltration and ion conduction are difficult to strengthen the flow guide effect, sets low-porosity separators with high stability and high strength in other areas, and the two areas work together to solve the deficiency of high-porosity separators in mechanical strength and stability, while ensuring uniform distribution of electrolyte inside the separator, improving the electrolyte wettability and ion conductivity of the separator, and thus improving the electrochemical performance and safety performance of the battery.

[0027] For the purpose of better balancing the electrical conductivity and mechanical stability of the separator, in a preferred embodiment, the porosity of the flow guiding zone is > the porosity of the stabilizing zone, with a difference of 20-50%; and / or the porosity of the flow guiding zone is 50-70%; and / or the porosity of the stabilizing zone is 10-40%. The porosity of the flow guiding zone set in the above range is conducive to optimizing the wettability of the electrolyte and the transmission efficiency of lithium ions, shortening the diffusion path of lithium ions, reducing the transmission resistance, and thus improving the overall electrical performance of the battery. The porosity of the stabilizing zone limited in a lower range is conducive to enhancing the mechanical strength and heat-resistant stability of the separator, reducing the risk of damage under extreme conditions, and maintaining the safe operation of the battery.

[0028] Further preferably based on similar reasons, the porosity of the flow guiding zone is 55-65%; and / or the porosity of the stabilizing zone is 14-30%.

[0029] In a preferred embodiment, the percentage of the transverse length of the prologue zone to the zoned separator of the cylindrical battery is 20-50%; and / or the percentage of the axial length of the middle zone to the zoned separator of the cylindrical battery is 20-40%.

[0030] The high-porosity separator can increase the number of pores in the lithium ion diffusion path, reduce the resistance of ion transmission, and the above-mentioned zoning can further promote the effective wettability of the electrolyte inside the battery to the central area of the roll core, promote the transmission of lithium ions in the difficult-to-wet area, make the distribution of the electrolyte inside the roll core more uniform, further reduce the local dryness phenomenon, and thus improve the electrical conductivity, charge and discharge efficiency, and overall electrochemical stability of the battery.

[0031] To further improve the uniformity and stability of the mechanical properties of the separator, in a preferred embodiment, the percentage of the transverse length of the first edge zone to the zoned separator of the cylindrical battery is 50-80%; and / or the percentage of the transverse length of the second edge zone to the zoned separator of the cylindrical battery is 50-80%; and / or the percentage of the axial length of the first edge zone to the zoned separator of the cylindrical battery is 30-40%; and / or the percentage of the axial length of the second edge zone to the zoned separator of the cylindrical battery is 30-40%; and / or the percentage of the transverse length of the first edge zone to the zoned separator of the cylindrical battery is the same as the percentage of the transverse length of the second edge zone to the zoned separator of the cylindrical battery; and / or the percentage of the axial length of the first edge zone to the zoned separator of the cylindrical battery is the same as the percentage of the axial length of the second edge zone to the zoned separator of the cylindrical battery; and / or the area of the first edge zone is the same as the area of the second edge zone.

[0032] To further balance the ion conduction ability and mechanical stability inside the battery, in a preferred embodiment, the area ratio of the flow guide area to the stable area is (1-1.5):1. Under the above conditions, it is more conducive to promote the infiltration of electrolyte and the rapid diffusion of lithium ions by using the high porosity of the flow guide area, while enhancing the mechanical strength and heat resistance of the separator by using the low porosity of the stable area, reducing the redundancy of porosity in the easy-to-infiltrate area, while providing sufficient porosity support in the ion-conducting-difficult area, to simultaneously improve the strength of the separator and the electrolyte infiltration effect.

[0033] In a preferred embodiment, the base film material of the zoned separator of the cylindrical battery is a polyolefin separator or a non-woven fabric separator; wherein the polyolefin separator is a polyethylene separator (PE), a polypropylene separator (PP), or a PE / PP composite separator; and / or the non-woven fabric separator is an aramid fiber separator or a polyimide separator (PI); optionally, the surface of the base film material of the stable area further has a coating layer, which includes one or more of a ceramic coating layer, an aluminum oxide coating layer, and a silicon dioxide coating layer.

[0034] Polyolefin separators have the core advantages of excellent mechanical properties, good chemical stability, low cost, and the thermal closure safety effect of PE; non-woven fabric separators have excellent temperature resistance (250-400℃), good liquid affinity, and controllable pore size. The above separators are conducive to balancing the mechanical strength of the base material and the temperature resistance and liquid affinity of the functional layer, and have balanced performance, which are suitable for high-end power batteries (such as 800V fast charging), long-life energy storage, and other scenarios that have high requirements for safety and rate. In the flow guide area, the non-coated polyolefin or non-woven fabric separator with high porosity is conducive to promoting the full infiltration of electrolyte and the transmission of lithium ions; while in the stable area, the non-coated polyolefin or non-woven fabric separator with low porosity is conducive to enhancing the physical stability and heat resistance of the separator, and improving the safety performance of the battery in a high-temperature environment. Adding a coating layer can further improve the stability and mechanical strength of the stable area of the separator, thereby better resisting external forces and reducing the risk of short circuit during battery assembly and use.

[0035] In another typical embodiment of the present application, a preparation method of the zoned separator of the cylindrical battery of the present application is also provided, which comprises the following steps: step S1, preparing a mask plate, the mask plate comprising an opening area and a covering area, the shape of the opening area being the same as that of the stable area of the zoned separator of the cylindrical battery, and the shape of the covering area being the same as that of the flow guide area of the zoned separator of the cylindrical battery; step S2, placing the mask plate above the base film and performing electron beam irradiation to obtain the zoned separator of the cylindrical battery.

[0036] The cylindrical battery partition separation membrane of the application is prepared by irradiation crosslinking method, and the polymer molecular structure of the base film in a specific area is selectively changed by high-energy rays through a mask plate, so as to accurately regulate the local porosity. The initial porosity, pore size and thickness of the base film are uniform, and the base film is clean and defect-free. The mask plate is designed to have openings according to the partition design, so that the local area of the separation membrane is irradiated to form a stable area, and the remaining part is used as a flow guide area. The shape of the opening area of the mask plate is the same as that of the stable area, and the shape of the covered area is the same as that of the flow guide area. The mask plate is composed of a material with high absorption / reflection to irradiation rays, and only the opening area allows the rays to pass through, so that the rays can only act on a specific area of the separation membrane, realizing spatial selectivity and allowing the creation of a complex porosity distribution pattern on the separation membrane.

[0037] During preparation, the mask plate is placed above the base film, and electron beam irradiation causes the entire polymer network to shrink, causing the original micropores to be compressed and smaller. As charged particles, high-energy electrons directly bombard the polymer molecular chains of the base film, causing ionization and excitation, generating a large number of active macromolecular radicals. These radicals combine with each other to form a three-dimensional network crosslinking structure throughout the material, and the crosslinking network itself occupies more space and blocks the communication path of some pores, resulting in a decrease in the overall porosity of the irradiated area, and the corresponding area forms a stable area, and the remaining part is used as a flow guide area.

[0038] Compared with other preparation methods, electron beam irradiation has a high energy deposition rate, and the electron beam can quickly deliver a large amount of energy to the polymer of the base film, which is efficient and easy to initiate crosslinking. In addition, the penetration depth is controllable, and by adjusting the acceleration voltage, the penetration depth can be accurately controlled to perfectly match the thickness of the separation membrane, realizing bulk crosslinking rather than just surface treatment. In addition, it is easy to be patterned and industrialized, and the electron beam can be precisely controlled and scanned by electromagnetic field, which is suitable for patterned irradiation through a mask plate and easy to be integrated into a roll-to-roll production line for high-speed processing.

[0039] In summary, the application realizes local adjustment of the porosity of the separation membrane by electron beam irradiation combined with mask plate technology. Specifically, the mask plate is designed to have an opening area and a covered area, corresponding to a high stability area and a high flow area on the separation membrane, respectively. When the mask plate is placed above the base film for electron beam irradiation, only the base film under the opening area is irradiated, causing crosslinking reaction to occur, thereby reducing the porosity of the area and making the structure of the separation membrane more compact, significantly improving the mechanical strength and thermal stability. The base film under the covered area is not affected by irradiation and maintains the original porosity, ensuring good electrolyte wettability and ion conductivity. The above preparation method is simple and easy to operate, and the prepared separation membrane has a stable area and a flow area, which can improve the performance balance of the separation membrane, ensure uniform distribution of the electrolyte inside the separation membrane, and avoid local dryness, thereby improving the electrical performance of the battery while maximizing the safety of the battery.

[0040] To further optimize the basic performance of the separator, promote efficient ion conduction, make the separator better adapt to the battery structure, and at the same time enhance the mechanical stability of the separator in high energy density batteries, while also facilitating the adjustment of porosity by electron beam irradiation, in a preferred embodiment, the porosity of the base film is 50-80%; and / or the thickness of the base film is 15-25 μm, and the width is 80-100 mm; and / or the material of the mask plate includes one or more of titanium alloy, stainless steel, aluminum oxide, and polyether ether ketone. The high absorption / reflection characteristics of the mask plate material can enable precise control of the irradiation to the specified opening area, promote the formation of stable zones, and not affect the ion transmission performance of the flow guide zone.

[0041] Optionally, the surface of the base film also has a coating, which includes one or more of a ceramic coating, an aluminum oxide coating, and a silicon dioxide coating. The base film with a coating corresponding to the opening area of the mask plate is converted into a stable zone with a coating by electron beam irradiation, which can significantly enhance the physical strength of the separator, especially when subjected to external force impact or temperature rise. The coating can effectively reduce the tearing and deformation of the separator, thereby further improving the overall safety performance of the battery.

[0042] In a preferred embodiment, the acceleration voltage of the electron beam irradiation is 0.5-3 MeV, the absorbed dose is 20-100 kGy, the dose rate is 1-10 kGy / s, and the processing time = absorbed dose ÷ dose rate; and / or the base film irradiated by the electron beam has a processing speed of 5-20 m / min; and / or the electron beam irradiation environment includes a vacuum atmosphere or a protective atmosphere, and the protective atmosphere includes N2 atmosphere and / or Ar atmosphere. The above irradiation parameters are beneficial to promote the precise crosslinking of the molecular structure of the base film in the stable zone, thereby effectively improving the mechanical strength and thermal stability of the region. At the same time, the electron beam works in a vacuum atmosphere or a protective atmosphere, which can reduce oxidation or side reactions during irradiation and improve the integrity and performance consistency of the separator.

[0043] High-energy electron beams precisely act on the target separator stable zone through the mask plate, reducing the pore size and porosity, thereby significantly enhancing the mechanical strength of the separator and reducing the risk of puncture. In the high flow guide zone, the separator maintains a high porosity due to the absence of direct electron beam action, which is beneficial to the full wetting of the electrolyte and the rapid transmission of lithium ions. Under the above conditions, the capacity retention rate of the cylindrical battery during the cycle process is improved, and the mechanical strength and safety of the battery are improved, achieving balanced optimization of performance and safety.

[0044] In another typical embodiment of the present application, a cylindrical battery is also provided, comprising a positive electrode, a negative electrode, a separator and an electrolyte, the separator comprising the above-mentioned zoned separator of the cylindrical battery of the present application, by designing different porosities in different zones of the separator, both high conductivity and high safety of the lithium ion battery are taken into account, and the comprehensive performance of the cylindrical battery, especially the silicon-based negative electrode system battery, is significantly improved. In some embodiments, the negative electrode comprises a silicon-based negative electrode.

[0045] Typically but not limitedly, the porosity of the flow guide zone is greater than the porosity of the stable zone, and the difference is 20%, 25%, 30%, 35%, 40%, 45%, 50% or any range value composed of any two of the above values.

[0046] Typically but not limitedly, the porosity of the flow guide zone is 50%, 55%, 60%, 65%, 70% or any range value composed of any two of the above values; the porosity of the stable zone is 10%, 15%, 20%, 25%, 30%, 35%, 40% or any range value composed of any two of the above values.

[0047] Typically but not limitedly, the percentage of the prologue zone in the transverse length of the zoned separator of the cylindrical battery is 20%, 25%, 30%, 35%, 40%, 45%, 50% or any range value composed of any two of the above values; the percentage of the middle zone in the axial length of the zoned separator of the cylindrical battery is 20%, 25%, 30%, 35%, 40% or any range value composed of any two of the above values.

[0048] Typically but not limitedly, the percentage of the first edge zone in the transverse length of the zoned separator of the cylindrical battery is 50%, 55%, 60%, 65%, 70%, 75%, 80% or any range value composed of any two of the above values; the percentage of the second edge zone in the transverse length of the zoned separator of the cylindrical battery is 50%, 55%, 60%, 65%, 70%, 75%, 80% or any range value composed of any two of the above values; the percentage of the first edge zone in the axial length of the zoned separator of the cylindrical battery is 30%, 32%, 35%, 38%, 40% or any range value composed of any two of the above values; the percentage of the second edge zone in the axial length of the zoned separator of the cylindrical battery is 30%, 32%, 35%, 38%, 40% or any range value composed of any two of the above values.

[0049] Typically but not limitedly, the area ratio of the flow guide zone to the stable zone is 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1 or any range value composed of any two of the above values.

[0050] Typically but not limitedly, the porosity of the base film is 50%, 55%, 60%, 65%, 70%, 75%, 80% or any range value composed of any two of the above values.

[0051] Typically but not exclusively, the electron beam irradiation has an acceleration voltage of 0.5 MeV, 1 MeV, 1.5 MeV, 2 MeV, 2.5 MeV, 3 MeV or any range defined by any two of these values, an absorbed dose of 20 kGy, 40 kGy, 50 kGy, 70 kGy, 80 kGy, 90 kGy, 100 kGy or any range defined by any two of these values, and a dose rate of 1 kGy / s, 2 kGy / s, 4 kGy / s, 5 kGy / s, 8 kGy / s, 10 kGy / s or any range defined by any two of these values.

[0052] The application will be further described in conjunction with specific examples which are not to be understood as limiting the scope of the application as claimed.

[0053] Example 1

[0054] The base film is a commercial polyethylene separator membrane Wet-process PE (brand SK ie technology) with a porosity of 60% and a thickness of 20 pm and a width of 90 mm.

[0055] The polyethylene separator membrane is irradiated by electron beam in a roll-to-roll continuous production mode. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere to meet the irradiation environment: O2< 50 ppm. The separator membrane passes through the electron beam irradiation crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the polyether ether ketone mask plate are set according to the designed stable zone, as shown in Table 1. The electron beam irradiation parameters are: absorbed dose: 70 kGy, dose rate: 4 kGy / s, electron beam acceleration voltage: 1.5 MeV, and the separator membrane is wound after passing through the irradiation equipment.

[0056] Example 2

[0057] The base film is a commercial polyethylene separator membrane Wet-process PE (brand SK ie technology) with a porosity of 60% and a thickness of 20 pm and a width of 90 mm.

[0058] The polyethylene separator membrane is irradiated by electron beam in a roll-to-roll continuous production mode. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere to meet the irradiation environment: O2< 50 ppm. The separator membrane passes through the electron beam irradiation crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the polyether ether ketone mask plate are set according to the designed stable zone, as shown in Table 1. The electron beam irradiation parameters are: absorbed dose: 70 kGy, dose rate: 4 kGy / s, electron beam acceleration voltage: 1.5 MeV, and the separator membrane is wound after passing through the irradiation equipment.

[0059] Example 3

[0060] The base film is a commercial polyethylene separator membrane Wet-process PE (brand SK ie technology) with a porosity of 60% and a thickness of 20 pm and a width of 90 mm.

[0061] The polyethylene separator membrane is subjected to electron beam irradiation crosslinking in a roll-to-roll continuous production mode. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere to meet the irradiation environment: O2< 50 ppm. The separator membrane passes through the electron beam irradiation crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the polyether ether ketone mask plate are set according to the designed stable zone, as shown in Table 1. Electron beam irradiation parameters: absorbed dose: 90 kGy, dose rate: 4 kGy / s, electron beam acceleration voltage: 1.5 MeV, and the separator membrane is wound after passing through the irradiation equipment.

[0062] Example 4

[0063] The base film is a commercial polyethylene separator membrane Wet-process PE (brand SK ie technology) with a porosity of 60% and a thickness of 20 pm and a width of 90 mm.

[0064] The polyethylene separator membrane is subjected to electron beam irradiation crosslinking in a roll-to-roll continuous production mode. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere to meet the irradiation environment: O2< 50 ppm. The separator membrane passes through the electron beam irradiation crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the polyether ether ketone mask plate are set according to the designed stable zone, as shown in Table 1. Electron beam irradiation parameters: absorbed dose: 70 kGy, dose rate: 10 kGy / s, electron beam acceleration voltage: 1.5 MeV, and the separator membrane is wound after passing through the irradiation equipment.

[0065] Example 5

[0066] The difference from Example 1 is that the base film is a commercial polyethylene separator membrane (brand SK ie technology) with a porosity of 50% and a thickness of 20 pm and a width of 90 mm.

[0067] Example 6

[0068] The difference from Example 1 is that the base film is a commercial polyethylene separator membrane (brand SK ie technology) with a porosity of 70% and a thickness of 20 pm and a width of 90 mm.

[0069] Example 7

[0070] The difference from Example 1 is that the porosity of the stabilization zone is different, see Table 1 for details.

[0071] Examples 8 to 9

[0072] The difference from Example 1 is that the line scanning irradiation width and length of the electron beam after passing through the polyether ether ketone mask plate are set according to the designed stabilization zone, see Table 1 for details.

[0073] Example 10

[0074] The base film is a commercial polyimide separator roll, with a porosity of 60%, a thickness of 15 μm, and a width of 80 mm.

[0075] The polyethylene separator is irradiated and crosslinked by electron beam in a continuous production mode of roll-to-roll. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere, meeting the irradiation environment: O2< 50 ppm. The separator passes through the electron beam irradiation and crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the titanium alloy mask plate are set according to the designed stabilization zone, see Table 1 for details. Electron beam irradiation parameters: absorbed dose: 20 kGy, dose rate: 1 kGy / s, electron beam acceleration voltage: 0.5 MeV, and the separator is wound after passing through the irradiation equipment.

[0076] Example 11

[0077] The base film is a commercial PE / PP composite separator roll, with a porosity of 60%, a thickness of 25 μm, and a width of 100 mm.

[0078] The polyethylene separator is irradiated and crosslinked by electron beam in a continuous production mode of roll-to-roll. The atmosphere control system is responsible for continuously filling high-purity nitrogen into the irradiation area to maintain a local inert atmosphere, meeting the irradiation environment: O2< 50 ppm. The separator passes through the electron beam irradiation and crosslinking equipment at a speed of 20 m / min, and the line scanning irradiation width and length of the electron beam after passing through the stainless steel mask plate are set according to the designed stabilization zone, see Table 1 for details. Electron beam irradiation parameters: absorbed dose: 100 kGy, dose rate: 10 kGy / s, electron beam acceleration voltage: 3 MeV, and the separator is wound after passing through the irradiation equipment.

[0079] Comparative Example 1

[0080] The separator is a commercial polyethylene separator roll Wet-process PE (brand SK ie technology), with a porosity of 60%, a thickness of 20 μm, and a width of 90 mm.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that no mask plate is used.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that the shape of the opening area of the mask plate is the same as the flow guiding area of the zoned separator of the cylindrical battery, and the shape of the masking area is the same as the stabilizing area of the zoned separator of the cylindrical battery.

[0085] Performance test:

[0086] The separators of the above examples and comparative examples were subjected to the following analysis and detection, and the results are shown in Tables 1 and 2.

[0087] Porosity: liquid immersion method, by measuring the mass change of the separator before and after immersion, the pore volume is calculated, and then the porosity is obtained. Test steps: a. Sample preparation: cut the separator into a regular shape (such as a round piece), and accurately measure its area (A) and thickness (T). After drying in a drying oven, weigh its dry weight (M1). b. Immersion and weighing: immerse the dried separator sample completely in liquid n-hexadecane, degas in a vacuum environment, then take out and quickly wipe off the excess liquid droplets on the surface with filter paper, immediately weigh the wet weight (M2). Calculation formula: porosity ε = [(M2-M1) ÷ ρ 正十六烷 ] ÷ (A × T) × 100%.

[0088] Puncture strength: simulates the resistance of the separator to being punctured by metal dendrites, electrode particle edges, or assembly foreign matter during the production assembly or battery cycling process. A steel needle with a specified diameter of 0.5 mm is vertically punctured at a constant speed (50 mm / min) to the fixed clamped separator sample until it is punctured, and the force-displacement curve during the whole process is recorded, and the peak force is the puncture strength.

[0089] Tensile strength: used to evaluate the ability of the separator to withstand longitudinal and transverse tensile stress during battery winding, assembly, and other manufacturing processes, and its tear resistance. The separator sample is made into a standard shape (dumbbell / strip), and is stretched on a universal material testing machine at a constant speed (100 mm / min) until it breaks, and the stress-strain during the process is recorded, and the tensile strength = breaking tension ÷ cross-sectional area of the sample.

[0090] Capacity retention: NCM811, conductive agent (carbon black) and binder (PVDF) were mixed according to the weight ratio of 97.8%:1.2%:1% and dissolved with NMP, slurry, coated, and rolled to obtain a positive electrode sheet. Graphite mixed silicon (10% silicon + 83% graphite), conductive agent (carbon black) and binder (4% PAA + 1% SBR) were mixed according to the weight ratio of 93%:2%:5% and dissolved with NMP, slurry, coated, and rolled to obtain a negative electrode sheet. The separator of the above examples and comparative examples was wound and assembled with the positive electrode sheet and the negative electrode sheet to obtain a battery cell, and electrolyte (1 mol / L LiPF6 solution, electrolyte solvent EC:DMC:EMC = 1:1:1 (v / v / v)) was injected to obtain a cylindrical battery, wherein the length of the separator was 6200 mm. The cylindrical battery was cycled at 1C for 500 cycles under the condition of 25°C and the voltage range of 2.5-4.25V, and the capacity was recorded. The 1C / 500 cycle capacity retention rate = the 500th cycle discharge capacity ÷ the first cycle discharge capacity x 100%.

[0091] Table 1

[0092]

[0093] Table 2

[0094]

[0095] The sectional view of the separator region of the cylindrical battery of Example 1 is shown in Figure 1 , which shows that the partitioned separator of the cylindrical battery is wound from the beginning of the roll 10 to the end of the roll 20 along the winding direction. The partitioned schematic diagram of the separator region of the cylindrical battery of Example 1 is shown in Figure 2 , which shows that the partitioned separator of the cylindrical battery is divided into the beginning of the roll region 1 and the end of the roll region along the transverse direction in the winding direction; the end of the roll region is divided into the first edge region 31, the middle region 2 and the second edge region 32 along the axial direction perpendicular to the winding direction; the flow guide region includes the beginning of the roll region and the middle region; the stable region includes the first edge region and the second edge region; and the transverse length of the first edge region 31 in the partitioned separator of the cylindrical battery is shown in schematic A, and the axial length of the first edge region 31 and the axial length of the second edge region 32 in the partitioned separator of the cylindrical battery are shown in schematic B1 and B2, respectively. For ease of understanding, the three-dimensional schematic diagram of the cylindrical battery of Example 1 is also provided in Figure 3 .

[0096] It can be seen that the partitioned irradiation of Comparative Example 1 results in a higher overall porosity and lower resistance of the separator, thereby reducing the cycle life. The overall porosity of Comparative Example 2 is lower due to the overall irradiation, which significantly hinders the electrolyte infiltration and ion diffusion of the separator, and the cycle life is affected by easy polarization, lithium precipitation, etc. The reverse partitioned irradiation of Comparative Example 3 results in a greater negative impact on the areas with poor infiltration and ion diffusion, thereby reducing the cycle life.

[0097] As can be seen from the above, the stable / flow-conducting partition design of the cylindrical battery separator can meet the regional stability / diffusion requirements of the battery, improve the performance balance of the separator, and significantly optimize the cycle life of the battery. Compared with the comparative examples, the partition design of the separator in each embodiment of the present application maximizes the overall benefits of the separator. In the outer region of the winding core, including the two end faces of the winding tail, the electrolyte is easy to soak and conduct ions, and a separator with slightly lower porosity is used to increase the stability and mechanical strength of the separator. In the inner region of the winding core, including the winding head and the axial middle part, the electrolyte is difficult to soak and conduct ions, and a separator with higher porosity is used to increase the flow-conducting capacity of the separator. The partitioned separator of the cylindrical battery of the present application sets a high-porosity separator in the region where the soaking and ion conduction are difficult to strengthen the flow-conducting effect, and sets a low-porosity separator with high stability and high strength in other regions. The two regions work together to solve the mechanical strength and stability problems of the high-porosity separator, while ensuring uniform distribution of the electrolyte inside the separator, improving the electrolyte wettability and ion conductivity of the separator, and thus improving the electrochemical performance and safety performance of the battery.

[0098] In addition, it can be seen that when each process parameter is within the preferred range of the present application, the comprehensive effect is better.

[0099] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A partitioned separator for a cylindrical battery, characterized in that, The cylindrical battery separator is wound from the beginning to the end along the winding direction, with the winding direction as the transverse direction and the direction perpendicular to the winding direction as the axial direction. Along the transverse direction, the cylindrical battery partition membrane is sequentially divided into a roll-up area and a roll-up area; along the axial direction, the roll-up area is sequentially divided into a first side area, a middle area, and a second side area. The cylindrical battery partition membrane includes a flow guiding region and a stabilizing region. The flow guiding region includes the roll-up region and the middle region. The stabilizing region includes the first side region and the second side region. The porosity of the flow guiding zone is greater than that of the stable zone.

2. The cylindrical battery partition separator according to claim 1, characterized in that, The porosity of the flow guiding zone is greater than that of the stable zone, with a difference of 20-50%; and / or The porosity of the flow guiding zone is 50-70%; and / or The porosity of the stable region is 10-40%.

3. The cylindrical battery partition separator according to claim 1 or 2, characterized in that, The roll-up area occupies 20-50% of the lateral length of the cylindrical battery partition membrane; and / or The intermediate region accounts for 20-40% of the axial length of the cylindrical battery separator.

4. The cylindrical battery partition separator according to claim 1 or 2, characterized in that, The first side region accounts for 50-80% of the lateral length of the cylindrical battery partition membrane; and / or the second side region accounts for 50-80% of the lateral length of the cylindrical battery partition membrane; and / or The first edge region accounts for 30-40% of the axial length of the cylindrical battery partition membrane; and / or the second edge region accounts for 30-40% of the axial length of the cylindrical battery partition membrane; and / or The percentage of the first side region to the lateral length of the cylindrical battery partition membrane is the same as the percentage of the second side region to the lateral length of the cylindrical battery partition membrane; and / or the percentage of the first side region to the axial length of the cylindrical battery partition membrane is the same as the percentage of the second side region to the axial length of the cylindrical battery partition membrane; and / or the area of ​​the first side region is the same as the area of ​​the second side region.

5. The cylindrical battery separator according to claim 1 or 2, characterized in that, The area ratio of the flow guiding zone to the stable zone is (1~1.5):

1.

6. The cylindrical battery partition separator according to claim 1 or 2, characterized in that, The base membrane material of the cylindrical battery separator is a polyolefin separator or a non-woven fabric separator; wherein, the polyolefin separator is a polyethylene separator, a polypropylene separator, or a PE / PP composite separator; and / or the non-woven fabric separator is an aramid fiber separator or a polyimide separator. Optionally, the surface of the base film material in the stable region may further have a coating, the coating including one or more of a ceramic coating, an alumina coating, and a silica coating.

7. The method for preparing the cylindrical battery separator according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Prepare a mask plate, which includes an opening area and a covering area. The shape of the opening area is the same as the stable area of ​​the cylindrical battery partition membrane, and the shape of the covering area is the same as the current guiding area of ​​the cylindrical battery partition membrane. Step S2: Place the mask plate above the base film and irradiate it with an electron beam to obtain the cylindrical battery partition membrane.

8. The method for preparing a cylindrical battery partitioned separator according to claim 7, characterized in that, The porosity of the base membrane is 50-80%; and / or The base film has a thickness of 15~25μm and a width of 80~100mm; and / or The mask is made of one or more of the following materials: titanium alloy, stainless steel, alumina, and polyetheretherketone.

9. The method for preparing a cylindrical battery partitioned separator according to claim 7, characterized in that, The accelerating voltage of the electron beam irradiation is 0.5~3 MeV, the absorbed dose is 20~100 kGy, the dose rate is 1~10 kGy / s, and the treatment time = absorbed dose ÷ dose rate; and / or The electron beam irradiation of the substrate film has a passage speed of 5~20 m / min; and / or The environment in which the electron beam is irradiated includes a vacuum atmosphere or a protective atmosphere, wherein the protective atmosphere includes an N2 atmosphere and / or an Ar atmosphere.

10. A cylindrical battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The separator comprises any one of the cylindrical battery partition separators described in any one of 1 to 6.

Images