Battery, battery separator, and method for manufacturing separator

Abstract

The present invention provides a battery, a battery separator, and a method for manufacturing the separator, wherein the battery separator comprises a base film and a coating layer structure provided on the base film, the coating layer structure including a plurality of material layers, each of which includes a one-dimensional nanomaterial, and the average length of the one-dimensional nanomaterial in each of the material layers decreases with each layer along a direction away from the base film.

Description

[Technical Field]

[0001] The present invention relates to the field of batteries, and more particularly to batteries, battery separators, and methods for manufacturing separators. [Background technology]

[0002] The separator of a lithium-ion battery is one of the core components of the battery, and its performance has a significant impact on the overall performance of the battery, making it one of the key technologies limiting the development of lithium-ion batteries. As the application fields of lithium-ion batteries expand and the influence of lithium-ion electrical appliances in people's lives deepens, the requirements for the performance of lithium-ion batteries are also becoming higher. To meet the development requirements of lithium-ion batteries, the separator, as an important component of lithium-ion batteries, not only needs to have good chemical stability and low manufacturing costs, but also improving the safety performance of lithium-ion batteries has become an important trend in the current development of lithium-ion batteries.

[0003] In the related art, a separator for a lithium-ion battery may include a base film and a coating layer covering at least one surface of the base film. The coating layer may include one-dimensional nanomaterials, but the one-dimensional nanomaterials have an irregular and disordered stacking pattern, which is prone to problems such as too many gaps and insufficient contact points, thereby affecting the thermal stability of the separator. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a battery, a battery separator, and a method for manufacturing the separator to solve the problems of too many gaps and too few contact points. [Means for solving the problem]

[0005] According to a first aspect, the present invention provides a battery separator, the separator comprising a base film and a coating layer structure provided on the base film, the coating layer structure including multiple material layers, each of which includes a one-dimensional nanomaterial, and the average length of the one-dimensional nanomaterial in each material layer shortens with each layer along a direction away from the base film.

[0006] Optionally, the one-dimensional nanomaterial in the coating layer structure satisfies 5≧L50 / L10≧1.3 and 4≧L90 / L50≧1.3; L10 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 10% is a first target percentage; L50 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 50% is a first target percentage; L90 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 90% is a first target percentage; The length description value of the one-dimensional nanomaterial in the coated layer structure indicates the length of the one-dimensional nanomaterial when the ratio of the number of one-dimensional nanomaterials in the coated layer structure obtained by sequentially accumulating them in order of shortest length to the total number of one-dimensional nanomaterials in the coated layer structure reaches the first target ratio.

[0007] Selectively, The length value L10 of the one-dimensional nanomaterial in the coating layer structure is 100 nm to 300 nm; The length value of L50 of the one-dimensional nanomaterial in the coating layer structure is 250 nm to 400 nm; The length value of L90 of the one-dimensional nanomaterial in the coating layer structure is 350 nm to 900 nm; Optionally, the one-dimensional nanomaterials of the different material layers form different length description values ​​for the same second target fraction; The length description of the one-dimensional nanomaterial in the layer of material is When the number of one-dimensional nanomaterials in the corresponding material layer is sequentially accumulated in order of shortest length, the ratio between the accumulated number and the total number of one-dimensional nanomaterials in the corresponding material layer reaches the second target ratio, which indicates the length of the corresponding one-dimensional nanomaterial, and the second target ratio is not 50%; The length description value of the one-dimensional nanomaterial in each layer of material successively decreases along a direction away from the base film to the same second target percentage.

[0008] Optionally, the second target percentage is in the interval range of 5% to 40%, or in the interval range of 60% to 99%.

[0009] Optionally, the one-dimensional nanomaterial comprises at least one of nanocellulose, aramid nanofibers, and polyimide nanofibers.

[0010] Optionally, between adjacent first and second material layers, the gaps between the one-dimensional nanomaterial of the first material layer are partially or completely filled with the one-dimensional nanomaterial of the second material layer, provided that the first material layer is located on the side of the second material layer facing the base film.

[0011] According to a second aspect, the present invention provides a battery comprising a separator according to the first aspect and its alternative solutions.

[0012] According to a third aspect, the present invention provides a method for manufacturing a separator, which is used to manufacture the separator according to the first aspect and its alternative solutions, and the manufacturing method includes: Dispersing one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion; forming at least one corresponding slurry based on said at least one dispersion; applying the at least one slurry to the base film, and baking the base film and the slurry to dry, thereby obtaining the separator.

[0013] Optionally, before dispersing the one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion, the method for producing the same or different nanomaterials may further comprise the steps of: The method further includes cutting the one-dimensional nanomaterial source or the cut one-dimensional nanomaterial to form one-dimensional nanomaterials of at least different lengths by one or more cuts.

[0014] Optionally, before dispersing one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion, the method for producing the same or different nanomaterials may further comprise: A joining process in which one end of a one-dimensional nanomaterial source material is joined to one end of another source material. (a) , A bonding process for bonding a bonded one-dimensional nanomaterial to one end of said feedstock. (b) , or A bonding process for bonding one end of a bonded one-dimensional nanomaterial to one end of another bonded one-dimensional nanomaterial. (c) to form one-dimensional nanomaterials of at least partially different lengths by one or more bondings.

[0015] Optionally, the bond is Mixing the one-dimensional nanomaterial to be grafted and the material rich in hydroxyl functional groups in a solution; adding molecular sieve particles as a catalyst to the solution; The solution is heated and then cooled to remove the molecular sieve. particles and filtering out the grafted one-dimensional nanomaterial.

[0016] Optionally, forming at least one corresponding slurry based on the at least one dispersion may include: adding an adhesive and an auxiliary agent sequentially to the dispersion.

[0017] Optionally, the adhesive comprises at least one of polyacrylic acid, lithium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose; The co-agent includes at least one of glycerol, fluoroalkylethoxy alcohol ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium lauryl sulfate.

[0018] Optionally, the method of manufacture comprises: adding poly-N-isopropylacrylamide to the dispersion or the slurry. [Effects of the Invention]

[0019] In the battery, battery separator, and separator manufacturing method provided by the present invention, the length of the one-dimensional nanomaterial is related to the surface energy, and thus related to the adhesive ability of the base film. Therefore, compared with one-dimensional nanomaterials distributed randomly, the present invention distributes them layer by layer based on their adhesive ability, achieving an orderly distribution. The orderly distribution avoids the formation of large gaps that can be formed due to an irregular and disordered distribution and ensures a sufficient number of contact points. Furthermore, because the gaps in the one-dimensional nanomaterial of the first material layer are partially or completely filled with the one-dimensional nanomaterial of the second material layer, and the first material layer is located on the side of the second material layer facing the base film, the one-dimensional nanomaterial further reduces gaps and increases contact points under the condition of ensuring order. [Brief explanation of the drawings]

[0020] In order to more clearly describe the embodiments of the present invention or the solutions of the prior art, the following will briefly describe the drawings that need to be used in the description of the embodiments or the prior art. Of course, the drawings described below are only some embodiments of the present invention, and those skilled in the art can devise other drawings based on these drawings without any creative effort.

[0021] [Figure 1] 1 is a structural schematic diagram of a portion of a separator of a battery in one embodiment of the present invention. [Figure 2]1 is a flowchart of a method for manufacturing a separator in one embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing the change in length value l50 of a material layer according to the applied layer position in a specific example of the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the technical solutions of the present invention will be described clearly and completely with reference to the drawings of the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments thereof, and all other embodiments obtained by those skilled in the art without creative work based on the embodiments of the present invention fall within the protection scope of the present invention.

[0023] In the description of the present invention, the orientations or positional relationships indicated by terms such as "upper", "lower", "upper end", "lower end", "lower surface", and "upper surface" are orientations or positional relationships shown in the drawings, and are terms used only for the convenience and simplification of the description of the present invention. These terms do not indicate or imply that the devices or components shown necessarily have a specific orientation or are constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0024] In describing the present specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as terms that indicate or teach the relative importance or implicitly indicate the number of technical features shown. Thus, a feature qualified by "first" or "second" may explicitly or implicitly include one or more of the feature.

[0025] In the description of the present invention, "plurality" means many, for example, two, three, four, etc., unless expressly limited otherwise.

[0026] In the description of the present invention, unless otherwise clearly defined and limited, the term "connected" and the like should be interpreted broadly, and may mean, for example, fixedly connected, detachably connected, or connected to form an integral unit, mechanically connected, electrically connected, or connected to be able to communicate with each other, directly connected, indirectly connected via an intermediate medium, or connected to establish communication between two components or an interactive relationship between two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the actual situation.

[0027] The technical solutions of the present invention will be described in detail below using specific examples. Some of the following specific examples can be combined with each other, and the same or similar concepts or processes may not be repeatedly described in some of the examples.

[0028] See Figure 1. An embodiment of the present invention provides a battery separator 1, which includes a base film 11 and a coating layer structure 12 provided on the base film 11, the coating layer structure 12 including multiple material layers, each of which includes a one-dimensional nanomaterial, and along a direction away from the base film, the average length of the one-dimensional nanomaterial in each material layer decreases with each layer, and accordingly, the average size of the gaps between the one-dimensional nanomaterials in each material layer also decreases sequentially.

[0029] The coating layer has three material layers as shown in FIG. 1 , where the one-dimensional nanomaterial in the bottom layer has a longer average length than the one-dimensional nanomaterial in the middle layer, which in turn has a longer average length than the one-dimensional nanomaterial in the top layer. The difference in average length between the one-dimensional nanomaterials in each layer can be set arbitrarily, and the one-dimensional nanomaterials in the same layer may have the same or different lengths. In one embodiment, the one-dimensional nanomaterial includes at least one of nanocellulose, aramid nanofibers, and polyimide nanofibers. The one-dimensional nanomaterials in the embodiments of the present invention are not limited to those selected from the above examples.

[0030] In one embodiment, the one-dimensional nanomaterials in the different layers of material form different length description values ​​for the same second target fraction; The length description of the one-dimensional nanomaterial in the layer of material is The material Layer When the number of one-dimensional nanomaterials in a material layer is sequentially accumulated in order of shortest length, the ratio of the accumulated number to the total number of one-dimensional nanomaterials in the material layer reaches the second target proportion, which indicates the length of the one-dimensional nanomaterial. Accordingly, among the one-dimensional nanomaterials in the corresponding material layer, one-dimensional nanomaterials that are smaller than the corresponding length description value are the proportion that can reach the target proportion. Although the above explanation indicates the statistical significance of the length description value of one-dimensional nanomaterials, when actually determining the length description value, the actual calculation method can be handled in accordance with common knowledge in the field.

[0031] In one example, the second target percentage is set to be in the range of 5% to 40% or in the range of 60% to 99%, such as 5%, 10%, 20%, 40%, 60%, 70%, 80%, 90%, 99%, etc.

[0032] In one embodiment, the length description of the one-dimensional nanomaterial in each layer of material decreases sequentially along a direction away from the base film for the same second target percentage. Length may tend to decrease from layer to layer.

[0033] Furthermore, with regard to the length description value of the corresponding material layer, the meaning of the length description value is defined above using a method of performing accumulation and determining the length description value based on the accumulation result, but this does not necessarily indicate that the actual manufacturing and acceptance process includes this statistical process. In an actual solution, if the one-dimensional nanomaterial in the material layer is statistically analyzed for any product using values ​​with the same statistical meaning, the resulting length description value will satisfy the above-mentioned rules, i.e., will not deviate from the scope of protection of the embodiment. In some solutions, the satisfaction of the above-mentioned length rules can be ensured by selecting the length of the one-dimensional nanomaterial in advance or by manufacturing the one-dimensional nanomaterial to a specific length.

[0034] For length description values ​​of one-dimensional nanomaterials in a material layer, e.g. The term "l10" refers to the length of the one-dimensional nanomaterial in the material layer, where the ratio of the number of one-dimensional nanomaterials of each length in the corresponding material layer, calculated in ascending order of length, to the total number of one-dimensional nanomaterials in the corresponding material layer, reaches 10%; The l50 of the one-dimensional nanomaterial in the material layer refers to the length of the one-dimensional nanomaterial when the ratio of the number of one-dimensional nanomaterials of each length in the corresponding material layer, calculated in order from shortest to longest, to the total number of one-dimensional nanomaterials in the corresponding material layer reaches 50%, and the l50 can be understood to indicate to some extent the average length of the corresponding material layer.

[0035] The l90 of a one-dimensional nanomaterial in the material layer refers to the length of the one-dimensional nanomaterial when the ratio of the number of one-dimensional nanomaterials of each length in the corresponding material layer, calculated in order from shortest to longest, to the total number of one-dimensional nanomaterials in the corresponding material layer, reaches 90%.

[0036] When l50 (i.e., the average length) is realized to be gradually decreased, one or more other length description values ​​(e.g., l90 and / or l10) may also be realized to be gradually decreased.

[0037] Therefore, in the above solution, it is fully realized that from the change trend of the defined length description value, in the cases of l50 and each second target ratio, the one-dimensional nanomaterials both tend to decrease layer by layer, and the one-dimensional nanomaterials are ensured to be distributed in an orderly manner, resulting in the one-dimensional nanomaterials having a more concentrated and unified length gradient distribution, which further reduces the number and size of gaps and contributes to increasing the number of contact points, thereby further improving heat resistance.

[0038] In one embodiment, The length value L10 of the one-dimensional nanomaterial in the coating layer structure is 100 nm to 300 nm; The length value L50 of the one-dimensional nanomaterial in the coating layer structure is 250 nm to 400 nm; The length value L90 of the one-dimensional nanomaterial in the coating layer structure is 350 nm to 900 nm; L10 of the one-dimensional nanomaterial in the coating layer structure represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 10% is a first target percentage; L50 of the one-dimensional nanomaterial in the coated layer structure indicates a length description value of the one-dimensional nanomaterial in the coated layer structure when 50% is a first target proportion, and may be understood as the average length of the one-dimensional nanomaterial in the coated layer structure; L90 of the one-dimensional nanomaterial in the coating layer structure indicates a length description value of the one-dimensional nanomaterial in the coating layer structure when 90% is a first target percentage; The length description value of the one-dimensional nanomaterial in the coating layer structure is When the number of one-dimensional nanomaterials in the coating layer structure is successively accumulated in order of length from shortest to longest, the ratio between the accumulated number and the total number of one-dimensional nanomaterials in the coating layer structure reaches the first target ratio, and the ratio indicates the length of the one-dimensional nanomaterials corresponding to the first target ratio; And, for the one-dimensional nanomaterial in the coating layer structure, L50 / L10>1.3 and L90 / L50>1.3 are satisfied; L10 of the one-dimensional nanomaterial in the coating layer structure refers to the length description value of the one-dimensional nanomaterial in the coating layer structure when 10% is a first target percentage; L50 of the one-dimensional nanomaterial in the coating layer structure refers to the length description value of the one-dimensional nanomaterial in the coating layer structure when 50% is a first target ratio; The L90 of the one-dimensional nanomaterial in the coating layer structure refers to the length description value of the one-dimensional nanomaterial in the coating layer structure when 90% is a first target percentage; The above explanation shows the statistical significance of the length description value of the coating layer structure, but when actually determining the length description value, the actual calculation method can be handled according to common knowledge in the art.

[0039] Furthermore, with regard to the length description value of the coating layer structure, the meaning of the length description value is defined above using a method of performing accumulation and determining the length description value based on the accumulation result, but this does not necessarily indicate that the actual manufacturing and acceptance process includes such a statistical process. In an actual solution, if the one-dimensional nanomaterial in the material layer of any product is statistically analyzed using values ​​with the same statistical meaning, the resulting length description value will satisfy the above-mentioned rules, i.e., will not deviate from the scope of protection of the embodiment. In some solutions, the satisfaction of the above-mentioned length rules can be ensured by selecting the length of the one-dimensional nanomaterial in advance or by manufacturing the one-dimensional nanomaterial to a specific length.

[0040] In one example, for the one-dimensional nanomaterial in the coating layer structure, L10=110 nm, L50=310 nm, and L90=850 nm.

[0041] The fitting results of the relationship between the l50 length value of the one-dimensional nanomaterial in each material layer and the coating layer position (position in the thickness direction of the coating layer) where the material layer is located in the direction away from the base film can be understood by referring to curves 1, 2a, and 2b in Figure 3, whereby the curves can be embodied such that the l50 length value sequentially decreases as the thickness increases (i.e., as the distance between the coating layer position where the material layer is located and the base film increases).

[0042] In Figure 3, the coating layer position on the abscissa indicates the position where the material layer is located in the coating layer structure along the thickness direction. When expressed as a percentage, it can indicate the percentage of the distance between the coating layer position where the material layer is located and the base film in the thickness of the entire coating layer structure. For example, 10% indicates that the distance between the coating layer position and the base film accounts for 10% of the thickness of the entire coating layer structure.

[0043] For curve 1, the length value l50 of the one-dimensional nanomaterial in the material layer can be understood by fitting as a linear change as the distance between the coating layer position where the material layer is located and the base film increases. In this case, the relationship between the length value x of l50 and the coating layer position Y can be, for example, Y = kx + b (k < 0, b > 0). For the case of curve 2a, the length value l50 of the one-dimensional nanomaterial in the material layer can change from a fast to a slow trend as the distance between the coating layer position where the material layer is located and the base film increases. For the case of curve 2b, the length value l50 of the one-dimensional nanomaterial in the material layer can change from a slow to a fast change trend as the distance between the coating layer position where the material layer is located and the base film increases.

[0044] The above linear change, the change tendency from fast to slow, or the change tendency from slow to fast can be realized by setting the length of the one-dimensional nanomaterial in the coating layer structure, which allows the length setting of the one-dimensional nanomaterial in the coating layer structure to be selected according to the required change tendency. for example, If a linear change needs to be realized (for example, as shown in curve 1), the length of the one-dimensional nanomaterial in the coating layer structure should be set so that 2≧L90 / L50>1.5 is satisfied; If it is necessary to realize a change from slow to fast (for example, as shown in curve 2b), the length of the one-dimensional nanomaterial in the coating layer structure should be set so that L50 / L10>2 and 1.5≧L90 / L50≧1.3 are satisfied; If a change from fast to slow needs to be realized (for example, as shown in curve 2a), the applied layer structure The length of the one-dimensional nanomaterial in should be set so that L90 / L50>2 is satisfied.

[0045] Since the prior art did not intend to form a layered structure, the length setting performed for different change trends in the above solution cannot be disclosed or taught by the prior art.

[0046] The table below describes some of the one-dimensional nanomaterials (the length is shown as the fiber length in the table below) and the effects of their use.

[0047] [Table 1]

[0048] Here, L represents the length of the one-dimensional nanomaterial.

[0049] As can be seen from Examples 1 to 6, when L is within an appropriate range, the coated separator has optimal heat resistance, but when L is too small (Examples 10, 11, and 12) or too large (Examples 15 and 16), the coated separator has reduced heat resistance.

[0050] After careful consideration and analysis, the main reasons for the above results were: When the length of one-dimensional nanomaterials is too small, the degree of stacking between the one-dimensional nanomaterials is insufficient to form a network structure where the nanomaterials intertwine with each other, resulting in insufficient heat resistance. However, after increasing the thickness, the heat resistance of the coating layer is effectively improved. Furthermore, when the length of one-dimensional nanomaterials is too long, the one-dimensional nanomaterials (i.e., nanowires) are formed into a twisted structure, and the twisted structure One-dimensional nanomaterials with When deposited on the surface of the separator, One-dimensional nanomaterials with twisted structures The reason is that they self-fold, making insufficient contact with other nanowires and resulting in weaker interactions (as shown in Examples 10, 11, and 12).

[0051] Furthermore, if the one-dimensional nanomaterial is too long, the deposited coating layer will have large gaps and the distance between contact points will be too far. When subjected to external forces (such as the shrinkage of the base film due to heating), these contact points will not be able to immediately transmit force to each other, leading to the collapse or destruction of the entire coating layer structure, and therefore making it impossible to suppress the thermal shrinkage of the coated separator (as shown in Examples 15 and 16).

[0052] Therefore, when L is 100 nm to 900 nm, the coating layer has both a relatively thin coating layer structure (thickness of the coating layer structure is less than 1 micron) and excellent heat resistance (180°C). That is, due to the characteristics of the layered structure, the coating layer can achieve excellent heat resistance with a relatively thin thickness (less than 1 micron). When the nanowires (i.e., one-dimensional nanomaterials) have a length of 100 nm to 900 nm, the nanowires (i.e., one-dimensional nanomaterials) are deposited on the surface of the base film, forming a layered structure (i.e., one-dimensional nanomaterials of different lengths). During the deposition process on the base film, surface energy plays a role, so the longest one-dimensional nanomaterials (which have the highest surface energy, are the most unstable, and are most likely to adhere when in contact with an interface with low surface energy) are deposited first, followed by the next-longest nanowires, and the shortest nanowires are deposited last, forming a layered structure stacked in order of length.

[0053] Furthermore, in adjacent material layers, the interstices of the one-dimensional nanomaterial in the lower layer are partially or completely filled by the one-dimensional nanomaterial in the upper layer.

[0054] As can be seen from the above, the gaps between long nanomaterials are large when they are stacked, so the lower the layer, the larger the gaps become. The relatively short nanomaterials in the upper layer can fill these gaps to a certain extent, and after being deposited layer by layer, there are not too many gaps inside the coating layer and there are relatively many contact points. Therefore, when heated, the coating layer has a tight structure that can suppress thermal deformation of the separator.

[0055] By comparing Example 4 with Comparative Examples 3 and 4, Example 15 with Comparative Example 1, and Example 16 with Comparative Example 2, It has been found that the coated separator has optimal heat resistance when the length of the one-dimensional nanofibers gradually decreases with each layer (embodied as a gradual decrease in the length description value of the one-dimensional nanofibers in each material layer), but the heat resistance of the coated separator is poor when the length of the one-dimensional nanofibers gradually increases with each layer or when the one-dimensional nanofibers are randomly arranged and distributed. The main reason for this phenomenon is that only when the one-dimensional nanofibers are gradually decreased with each layer can the coated layers have the greatest layer adhesion and the most contact between the nanofibers. Whether the coated layers are gradually increased with each layer or randomly arranged and distributed, the coating layers have poor layer adhesion, so the improvement in heat resistance is very limited.

[0056] In other solutions, some solutions can be further introduced to ensure the layering of 1D nanomaterials. For example, the layering of 1D nanomaterials is mainly completed through the coating and drying process. To achieve the purpose of layering during heating, a temperature-sensitive polymer such as poly(N-isopropylacrylamide) (PNIPAM), which has a certain ratio of hydrophobic isopropyl groups and hydrophilic amide groups in its molecule, can be added. At temperatures below 40°C, strong hydrogen bonding exists between the hydrophilic amide groups and the hydroxyl groups of the 1D nanomaterial, improving the affinity of the polymer chains with the 1D nanomaterial and the solvent. At this time, the PNIPAM polymer chains are extended, absorbing water and swelling, resulting in poor solution fluidity. As the temperature rises above 40°C, the hydrophilic force between the water molecules and the amide groups weakens, while the hydrophobic force between the isopropyl groups in the PNIPAM molecular chains strengthens. The hydrophobic effect of the PNIPAM polymer chains gradually strengthens and eventually becomes dominant. The polymer chains gather together through hydrophobic interaction to form a hydrophobic layer, which eventually expels water molecules and causes a phase transition. At this time, the polymer chains change from a sparse random coil structure to a dense colloidal particle structure, improving the fluidity of the solution. The longer the one-dimensional nanomaterial, the more PNIPAM it can support and the stronger its hydrophobicity, making it more likely to precipitate initially. Therefore, the introduction of PNIPAM can contribute to ensuring the realization of layering.

[0057] As can be seen from the above, in the above solution, the length of the one-dimensional nanomaterial is related to the surface energy, and thus related to the adhesive ability of the base film. Therefore, compared with one-dimensional nanomaterials distributed irregularly, the present invention distributes them layer by layer based on their adhesive ability, thereby achieving an orderly distribution. The orderly distribution avoids the formation of large gaps that may occur due to irregular and disordered distribution, and ensures a sufficient number of contact points. Furthermore, in the case of one-dimensional nanomaterials in a partial layer, the gaps are partially or completely filled by the one-dimensional nanomaterials in the layer above, thereby further reducing the gaps and increasing the contact points under conditions where the one-dimensional nanomaterials are ordered.

[0058] In addition to the separator and base film described above, other material layers may be incorporated in specific examples.

[0059] An embodiment of the present invention further provides a battery including a separator according to the above alternative solution.

[0060] The battery may be, for example, a lithium ion battery, and the separator may be a Electrode Furthermore, the separator may be provided with other existing or improved structural layers on or within the separator.

[0061] See Figure 2. An embodiment of the present invention further provides a separator manufacturing method for manufacturing the separator according to the first aspect and its alternative solutions, the manufacturing method including S21, S22, and S23. In S21, the one-dimensional nanomaterials of different lengths are dispersed in the same or different dispersants to obtain at least one dispersion. In S22, at least one corresponding slurry is formed based on the at least one dispersion. In S23, the at least one slurry is applied to the base film, and the base film and the slurry are baked to dry, thereby obtaining the separator.

[0062] In one example of step S23, the slurry may be applied only once and then baked and dried only once. In this case, the applied slurry may contain a plurality of types of one-dimensional nanomaterials with different lengths. In another example of step S23, the slurry may be applied multiple times and baked to dry once after each application. In this case, the type of slurry applied each time may be different, and the different slurries may be applied sequentially in order of the length of the one-dimensional nanomaterial. For example, in the case of applying three times to form three layers, first, the slurry containing the longest one-dimensional nanomaterial is applied to the base film and baked to dry, and then the slurry containing the next longest one-dimensional nanomaterial is again applied to the surface and baked to dry, and then the slurry containing the shortest one-dimensional nanomaterial is again applied to the surface.

[0063] Furthermore, one type of slurry may be used for each application, or two or more types of slurries may be mixed and then applied.

[0064] In one embodiment, one-dimensional nanomaterials of different lengths may be achieved based at least in part on the selection of raw materials for the one-dimensional nanomaterials, for example, when one-dimensional nanomaterials of different materials are selected and used, one-dimensional nanomaterials of different lengths may be able to be formed.

[0065] Alternatively, one-dimensional nanomaterials of different lengths may be formed using corresponding technical means.

[0066] In one example, before step S21, the manufacturing method further includes S24: In S24, the one-dimensional nanomaterial raw material or the cut one-dimensional nanomaterial is cut to form one-dimensional nanomaterials of at least partially different lengths by one or more cuts.

[0067] Cutting one-dimensional nanomaterials can form relatively short one-dimensional nanomaterials based on a single length of one-dimensional nanomaterial starting material, for example, the one-dimensional nanomaterial can be cut to half of the starting material, or in other cases, may not be achieved using a half-cutting method.

[0068] Any existing or improved means for achieving cutting of one-dimensional nanomaterials can be a specific example of an embodiment of the present invention, and in a specific example, the cutting can be achieved by etching the one-dimensional nanomaterial, for example, by etching the one-dimensional nanomaterial to half its original length.

[0069] Depending on the required layering, the raw material can be cut once or multiple times. For example, first, the one-dimensional nanomaterial can be etched to half its length, and then the one-dimensional nanomaterial with half the length can be retained. Then, the other half of the one-dimensional nanomaterial can be cut to obtain a one-dimensional nanomaterial with a quarter of its length. In this case, a three-layer structure can be formed. In another example, the one-dimensional nanomaterial with a quarter of its length can also be further cut. The number of cuts can be set arbitrarily as needed.

[0070] In one example, before step S21, the manufacturing method further includes S25: In S25, a bonding process (a) is performed to bond one end of a raw material of one-dimensional nanomaterial to one end of another raw material. (b) a bonding process in which a bonded one-dimensional nanomaterial is bonded to one end of the feedstock; or At least one of the bonding processes (c) is performed to bond a bonded one-dimensional nanomaterial to one end of another bonded one-dimensional nanomaterial, thereby forming one-dimensional nanomaterials of at least partially different lengths by one or more bondings. 。

[0071] As can be seen from the above, the objects to be joined may be one end of a raw material and one end of another raw material, one end of a raw material and one end of a joined one-dimensional nanomaterial, or one end of a joined one-dimensional nanomaterial and one end of another joined one-dimensional nanomaterial.

[0072] The joining of one-dimensional nanomaterials allows the formation of relatively long one-dimensional nanomaterials based on one length of one-dimensional nanomaterial starting material; for example, by joining two starting materials, a one-dimensional nanomaterial twice as long can be formed; in other examples, this may be achieved by using starting materials (or joined one-dimensional nanomaterials) of different lengths.

[0073] Any existing or improved means by which joining of one-dimensional nanomaterials can be achieved can be one specific example of an embodiment of the present invention.

[0074] For example, one-dimensional nanomaterial conjugation can be achieved based on materials rich in hydroxyl functional groups (e.g., polyethylene glycol PEG), in which case the conjugation described above can be achieved by: Mixing the one-dimensional nanomaterial to be conjugated and a material rich in hydroxyl functional groups (e.g., PEG) in a solution; adding molecular sieve particles as a catalyst to the solution; The solution is heated and then cooled to form a molecular sieve. particles and filtering out the grafted one-dimensional nanomaterial to obtain the grafted one-dimensional nanomaterial.

[0075] Take nanocellulose as a specific example. Nanocellulose has a significantly higher hydroxyl group content in the port region than in the intermediate region. The activity of hydroxyl groups can be fully utilized to increase the length of nanocellulose, as shown in (1) to (4). (1) Nanocellulose and polyethylene glycol (PEG) are mixed, with the molecular weight of 50,000 to 1,000,000 g / mol, and PEG accounts for 1% of the nanocellulose. The mixture is stirred thoroughly to homogenize the nanocellulose and polyethylene glycol, forming a corresponding solution. (2) Particles of 13A molecular sieve with a size of 1 mm to 10 mm are added to the above solution as a catalyst. (3) Heat the water to 80 degrees over 1 to 2 hours. (4) After cooling to room temperature, the 13A molecular sieve particles can be filtered off to obtain the grafted nanocellulose.

[0076] In the above solution, the addition of a material rich in hydroxyl functional groups (e.g., PEG) can link and crosslink nanocelluloses, and the use of a molecular sieve (e.g., 13A molecular sieve) as a catalyst can accelerate the polymerization reaction between PEG and nanocellulose, ultimately forming a nanocellulose-PEG-nanocellulose structure. Depending on the required layering, single or multiple conjugation of raw materials can be achieved. For example, first, the raw material of one-dimensional nanomaterials can be conjugated twice as long as the raw material, and then some of the double-length one-dimensional nanomaterials can be reserved. Next, the other double-length one-dimensional nanomaterials can be conjugated with the raw material or the double-length one-dimensional nanomaterials to obtain triple- or quadruple-length one-dimensional nanomaterials. In this case, a three-layer structure can be formed. In other cases, further conjugation can be performed, and the number of conjugations can be set as needed.

[0077] In one solution of step S21, one-dimensional nanomaterials of different lengths are dispersed in the same dispersant, and the slurries corresponding to the same dispersant are applied and layered; in another solution of step S21, different dispersions (the lengths of the one-dimensional nanomaterials in different dispersions are different) are formed based on one-dimensional nanomaterials of different lengths, and thus different dispersions and slurries can be formed, and when applied, various slurries can be layered and applied based on the length of the one-dimensional nanomaterials.

[0078] In one example, in step S21, one-dimensional nanomaterials of various lengths can be thoroughly dispersed in a dispersant, such as water, ethanol, or methanol. Dispersion methods include ultrasonication, high-speed stirring, high-pressure homogenization, and sand mill dispersion, and the like. The concentration of one-dimensional nanomaterials in the dispersion can range from 0.01 to 50 wt%.

[0079] In one embodiment, step S22 may specifically include sequentially adding an adhesive and an auxiliary to the dispersion.

[0080] The adhesive may be any material that provides adhesive properties, such as at least one of polyacrylic acid, lithium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, and carboxymethyl cellulose, but is not limited to those exemplified here. An appropriate adhesive may be selected depending on the size and material of the one-dimensional nanomaterial without departing from the scope of the embodiments of the present invention.

[0081] The above-mentioned auxiliary may include, for example, at least one of glycerol, fluoroalkylethoxy alcohol ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium lauryl sulfate.

[0082] In step S23, the slurry is applied to the base film by microgroove roller coating, spray coating, dip coating, extrusion coating, etc., and then baked to dry, thereby obtaining a separator composited with one-dimensional nanomaterials. The slurry may be applied to one side (i.e., to one surface of the base film) or both sides (i.e., to both surfaces of the base film).

[0083] In one embodiment, as mentioned above, poly(N-isopropylacrylamide) (PNIPAM) may be added, i.e., the manufacturing method further comprises adding poly(N-isopropylacrylamide) to the dispersion or the slurry. It has been found that the longer the length of one-dimensional nanomaterials, the greater the amount of PNIPAM supported and the stronger their hydrophobicity, making them more likely to precipitate initially, and therefore the introduction of PNIPAM can contribute to ensuring the realization of layering.

[0084] In the description herein, the use of terms such as "one embodiment," "one example," "specific implementation process," "one example," and the like means that the specific features, structures, materials, or characteristics described with reference to the example or example are included in at least one example or example of the present invention. In the description herein, general expressions of the above terms do not necessarily refer to the same example or example. Furthermore, the described specific features, structures, materials, or characteristics may be combined in any suitable manner in any one or more examples or examples.

[0085] Finally, it should be noted that the above embodiments are for illustrating the technical solutions of the present invention, not for limiting the same. The present invention will be described in detail with reference to the above embodiments. However, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some or all of the technical features thereof, and it should be understood that these modifications or substitutions will not deviate from the essence of the corresponding technical solutions and the scope of the technical solutions of the embodiments of the present invention. [Explanation of symbols]

[0086] 1 Separator 11 Base film 12 Coating layer structure

Claims

1. A battery separator comprising a base film and a coating layer structure provided on the base film, wherein the coating layer structure includes multiple material layers, each of which includes a one-dimensional nanomaterial, and wherein the average length of the one-dimensional nanomaterial in each material layer decreases with each layer along a direction away from the base film.

2. The one-dimensional nanomaterial in the coating layer structure satisfies 5≧L50 / L10≧1.3 and 4≧L90 / L50≧1.3; L10 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 10% is a first target percentage; L50 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 50% is a first target percentage; L90 represents a length description value of the one-dimensional nanomaterial in the coating layer structure when 90% is a first target percentage; The separator described in claim 1, characterized in that the length description value of the one-dimensional nanomaterial in the coated layer structure indicates the length of the one-dimensional nanomaterial when the ratio of the number obtained by sequentially accumulating the number of one-dimensional nanomaterials in the coated layer structure in order of shortest length to the total number of one-dimensional nanomaterials in the coated layer structure reaches the first target ratio.

3. The length value L10 of the one-dimensional nanomaterial in the coating layer structure is 100 nm to 300 nm; The length value L50 of the one-dimensional nanomaterial in the coating layer structure is 250 nm to 400 nm; The separator according to claim 2, wherein the L90 length value of the one-dimensional nanomaterial in the coating layer structure is 350 nm to 900 nm.

4. the one-dimensional nanomaterials of the different material layers form different length description values ​​for the same second target fraction; The length description of the one-dimensional nanomaterial in the layer of material is When the number of one-dimensional nanomaterials in the corresponding material layer is sequentially accumulated in order of length from shortest to longest, the ratio between the accumulated number and the total number of one-dimensional nanomaterials in the corresponding material layer reaches the second target ratio, which indicates the length of the corresponding one-dimensional nanomaterial, and the second target ratio is not 50%, the length description value of the one-dimensional nanomaterial of each layer of material sequentially decreases along a direction away from the base film to the same second target percentage; 2. The separator according to claim 1, wherein the second target ratio is in a range of 5% to 40% or in a range of 60% to 99%.

5. The separator according to any one of claims 1 to 3, wherein the one-dimensional nanomaterial includes at least one of nanocellulose, aramid nanofiber, and polyimide nanofiber.

6. The separator of claim 1, characterized in that, between adjacent first and second material layers, the gaps between the one-dimensional nanomaterial of the first material layer are partially or completely filled with the one-dimensional nanomaterial of the second material layer, and the first material layer is located on the side of the second material layer facing the base film.

7. A battery comprising the separator according to any one of claims 1 to 6.

8. A method for producing the separator according to any one of claims 1 to 6, comprising the steps of: Dispersing one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion; forming at least one corresponding slurry based on said at least one dispersion; applying the at least one slurry to the base film, and baking the base film and the slurry to dry, thereby obtaining the separator.

9. Before dispersing the one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion, 9. The method of claim 8, further comprising cutting the one-dimensional nanomaterial raw material or the cut one-dimensional nanomaterial to form one-dimensional nanomaterials of at least partially different lengths by one or more cuts.

10. Dispersing one-dimensional nanomaterials of different lengths in the same or different dispersants to obtain at least one dispersion, A bonding process (a) of bonding a raw material of one-dimensional nanomaterial to one end of another raw material; a bonding process (b) of bonding a bonded one-dimensional nanomaterial to one end of the feedstock; or 9. The method of claim 8, further comprising performing at least one of the bonding processes (c) bonding a bonded one-dimensional nanomaterial to one end of another bonded one-dimensional nanomaterial to form one-dimensional nanomaterials of at least partially different lengths by one or more bondings.

11. The above-mentioned joining is Mixing the one-dimensional nanomaterial to be grafted and the material rich in hydroxyl functional groups in a solution; adding molecular sieve particles as a catalyst to the solution; and heating the solution and then cooling it to filter out the molecular sieve particles and obtain the grafted one-dimensional nanomaterial.

12. forming at least one corresponding slurry based on said at least one dispersion, The method according to any one of claims 8 to 11, characterized in that it comprises adding an adhesive and an auxiliary agent sequentially to the dispersion.

13. the adhesive includes at least one of polyacrylic acid, lithium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, and carboxymethyl cellulose; 13. The method of claim 12, wherein the auxiliary comprises at least one of glycerol, fluoroalkylethoxy alcohol ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium lauryl sulfate.

14. The method according to any one of claims 8 to 11, further comprising adding poly-N-isopropylacrylamide to the dispersion or the slurry.

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