Composite separator and method for manufacturing the same, and semi-solid battery

Abstract

This application provides a composite separator, its preparation method, and a semi-solid-state battery. The composite separator comprises a non-woven porous substrate and a composite solid electrolyte coating filling the pores of the non-woven porous substrate. The non-woven porous substrate has a thickness ≤20 μm and a porosity ≥40%. The composite solid electrolyte coating comprises a dispersant, a swelling agent, a liquid pore guiding agent, an adhesive, and a nano-inorganic solid electrolyte. The swelling agent expands with increasing temperature. The liquid pore guiding agent contains at least one of carbonyl, hydroxyl, and phenyl groups, and is removed by drying after the composite solid electrolyte fills the pores of the non-woven porous substrate. The composite separator effectively reduces thermal shrinkage, exhibits good structural stability, and has minimal impact on ionic conductivity.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a composite separator and its preparation method, and a semi-solid-state battery. Background Technology

[0002] Semi-solid batteries are a new type of battery that has higher energy density and longer lifespan compared to traditional batteries, and also has better safety performance. Therefore, semi-solid batteries are widely used in drones, electric vehicles and other fields, and have shown great application prospects.

[0003] Because the electrolyte in a semi-solid battery is semi-solid, it cannot effectively isolate the negative and positive electrodes. Therefore, in practical applications, it often retains the use of a separator. For example, Chinese invention patent application No. 201610988814.X uses a polypropylene porous membrane as the separator substrate. However, because the micropores of the polyolefin substrate gradually close at high temperatures, resulting in overall shrinkage, a large amount of shrinkage will occur when a short circuit occurs inside the semi-solid battery, thereby exacerbating thermal runaway.

[0004] To reduce membrane shrinkage, Chinese invention patent application No. 202210425385.0 uses ceramic particles doped into the solid electrolyte to replace the use of polyolefin substrate. However, the ceramic particles are extruded into the solid electrolyte layer as a membrane. Although this avoids the thermal shrinkage of the membrane and reduces the impact on ionic conductivity, the ceramic particles are easy to fall off and have a poor blocking effect on lithium dendrites. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite separator that can better reduce thermal shrinkage, has good structural stability and has little impact on ionic conductivity, as well as its preparation method and a semi-solid battery.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A composite membrane includes a nonwoven porous substrate and a composite solid electrolyte coating filling the pores of the nonwoven porous substrate.

[0008] The thickness of the nonwoven porous substrate is ≤20μm, and the porosity is ≥40%.

[0009] The composite solid electrolyte coating includes a dispersant, an expanding agent, a liquid pore guiding agent, an adhesive, and a nano-inorganic solid electrolyte;

[0010] The expanding agent can expand as the temperature increases;

[0011] The liquid pore guiding agent contains at least one of carbonyl, hydroxyl and phenyl groups, and the liquid pore guiding agent is dried and removed after the composite solid electrolyte fills the pores of the nonwoven porous substrate.

[0012] In one embodiment, the expanding agent is at least one selected from aluminum oxide, calcium oxide, polyurethane, polystyrene, and polyvinyl alcohol.

[0013] In one embodiment, the adhesive comprises polyvinylidene fluoride.

[0014] In one embodiment, the nano-inorganic solid electrolyte is at least one of lithium titanium aluminum phosphate nano-solid electrolyte, lithium lanthanum titanium oxide nano-solid electrolyte, lithium lanthanum zirconium oxide nano-solid electrolyte, and lithium polyphosphoric sulfide nano-solid electrolyte.

[0015] In one embodiment, the liquid pore guiding agent has ≤7 carbon atoms.

[0016] In one embodiment, the liquid pore guiding agent comprises at least one of ethanol, toluene, isopropanone, 2-nonanone, and cyclohexanone.

[0017] In one embodiment, the dispersant is at least one of polyvinylpyrrolidone, herring oil, and polyethylene glycol.

[0018] In one embodiment, the nonwoven porous substrate is a natural fiber nonwoven porous substrate or a synthetic fiber nonwoven porous substrate.

[0019] In one embodiment, the pore size of the nonwoven porous substrate is 0.3 μm to 0.7 μm;

[0020] The nano-inorganic solid electrolyte has a D50 ≤ 20 nm.

[0021] In one embodiment, the composite solid electrolyte comprises the following components in parts by weight:

[0022]

[0023] 50 to 80 parts of nano-inorganic solid electrolyte.

[0024] A method for preparing a composite separator, used to prepare the composite separator described in any of the above embodiments, the method comprising the following steps:

[0025] The adhesive, expanding agent, and nano-inorganic solid electrolyte are dispersed to obtain a mixture.

[0026] The dispersant, liquid pore guide agent and solvent are placed in the mixture and allowed to stand.

[0027] The mixture after static treatment is stirred and mixed to obtain the composite solid electrolyte.

[0028] The composite solid electrolyte is used to fill the pores of the nonwoven porous substrate.

[0029] The nonwoven porous substrate after pore filling treatment is dried to obtain a composite diaphragm.

[0030] In one embodiment, the drying temperature for the nonwoven porous substrate after pore filling treatment is 60°C to 130°C.

[0031] A semi-solid-state battery includes a positive electrode, a negative electrode, and a composite separator as described in any of the above embodiments, wherein the composite separator is sandwiched between the positive electrode and the negative electrode.

[0032] Compared with the prior art, the present invention has at least the following advantages:

[0033] The composite separator of this invention contains an expanding agent and nano-inorganic solid electrolyte in the composite solid electrolyte coating. A dispersant promotes the uniform dispersion of the expanding agent and nano-inorganic solid electrolyte in the composite solid electrolyte coating. Furthermore, under the guidance of a liquid pore-guiding agent, the expanding agent and nano-inorganic solid electrolyte effectively penetrate and fill the pores of the nonwoven porous substrate. Since the expanding agent expands with increasing temperature, when the temperature of the composite separator rises, the expanding agent filling the pores of the nonwoven porous substrate expands, thus strengthening the structural support for the nonwoven porous substrate during thermal shrinkage. Furthermore, the nano-inorganic solid electrolyte, combined with the nonwoven porous substrate… The structural support provided by the composite solid electrolyte coating during thermal shrinkage of the substrate ensures that even under severe thermal shrinkage of the nonwoven porous substrate, the composite solid electrolyte coating still provides good structural support, effectively reducing the thermal shrinkage of the composite separator. Furthermore, the composite solid electrolyte fills the pores of the nonwoven porous substrate, promoting the formation of a self-healing SEI film in these pores, which effectively blocks lithium dendrites. Combined with the mechanical barrier provided by the composite solid electrolyte and the expansion agent, the structural stability of the composite separator is effectively improved. Moreover, the composite solid electrolyte filling the pores of the nonwoven porous substrate effectively ensures the ionic conductivity of the composite separator. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of a method for preparing a composite diaphragm according to an embodiment of the present invention;

[0036] Figures 2 to 3 The data are puncture test data for the composite diaphragms in Examples 5-12. Detailed Implementation

[0037] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0038] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] This application provides a composite separator. To better understand the composite separator of this application, the following further explanation is provided:

[0041] One embodiment of the composite membrane includes a nonwoven porous substrate and a composite solid electrolyte coating filling the pores of the nonwoven porous substrate. The nonwoven porous substrate has a thickness ≤20 μm and a porosity ≥40%. The composite solid electrolyte coating includes a dispersant, a swelling agent, a liquid pore guiding agent, an adhesive, and a nano-inorganic solid electrolyte. The swelling agent expands with increasing temperature. The liquid pore guiding agent contains at least one of carbonyl, hydroxyl, and phenyl groups, and is dried and removed after the composite solid electrolyte fills the pores of the nonwoven porous substrate.

[0042] The aforementioned composite diaphragm incorporates an expanding agent and nano-inorganic solid electrolyte in its composite solid electrolyte coating. A dispersant promotes the uniform dispersion of the expanding agent and nano-inorganic solid electrolyte within the coating. Furthermore, under the guidance of a liquid pore-guiding agent, the expanding agent and nano-inorganic solid electrolyte effectively penetrate and fill the pores of the nonwoven porous substrate. Since the expanding agent expands with increasing temperature, as the temperature of the composite diaphragm rises, the expanding agent filling the pores of the nonwoven porous substrate expands, strengthening the structural support for the nonwoven porous substrate during thermal shrinkage. This, combined with the nano-inorganic solid electrolyte, enhances the structural support of the nonwoven porous substrate. The structural support provided by the composite solid electrolyte coating during thermal shrinkage of the substrate ensures that even under severe thermal shrinkage of the nonwoven porous substrate, the composite solid electrolyte coating still provides good structural support, effectively reducing the thermal shrinkage of the composite separator. Furthermore, the composite solid electrolyte fills the pores of the nonwoven porous substrate, promoting the formation of a self-healing SEI film in these pores, which effectively blocks lithium dendrites. Combined with the mechanical barrier provided by the composite solid electrolyte and the expansion agent, the structural stability of the composite separator is effectively improved. Moreover, the composite solid electrolyte filling the pores of the nonwoven porous substrate effectively ensures the ionic conductivity of the composite separator.

[0043] It is understandable that when the slurry is applied to porous sheets via coating, it is difficult for the slurry to fully fill the micropores or nanopores on the porous sheets. Similarly, when the composite solid electrolyte is coated onto a non-woven porous substrate, capillary action occurs due to pore sizes smaller than 50 μm, making it difficult for the nano-inorganic solid electrolyte and other substances to fully and effectively fill the pores of the non-woven porous substrate. The resulting state is that only a small amount of nano-inorganic solid electrolyte exists at the pore ends of the non-woven porous substrate. This means that the structural strength of the composite solid electrolyte coating primarily mitigates the thermal shrinkage of the non-woven porous substrate. However, in cases of severe thermal shrinkage of the non-woven porous substrate, the composite solid electrolyte coating easily detaches from the substrate, leading to further thermal shrinkage. In this application… In this process, the composite solid electrolyte is coated and guided into the pores of the nonwoven porous substrate by a liquid pore guide agent, along with a nano-inorganic solid electrolyte and an expanding agent, for thorough and effective filling. This ensures that even with significant thermal shrinkage of the nonwoven porous substrate, the composite solid electrolyte coating still provides good structural support, effectively reducing the thermal shrinkage of the composite separator. Furthermore, the composite solid electrolyte filling the pores of the nonwoven porous substrate promotes the formation of a self-healing SEI film, effectively blocking lithium dendrites. Combined with the mechanical barrier effect of the composite solid electrolyte itself, this effectively improves the structural stability of the composite separator. Finally, the composite solid electrolyte filling the pores of the nonwoven porous substrate effectively ensures the ionic conductivity of the composite separator.

[0044] It should be noted that when coating a ceramic layer onto a nonwoven membrane, it is difficult for the ceramic to fully fill the pores of the membrane. While adding a film-forming agent to adhere to the ceramic layer can strengthen its adhesion, it is actually difficult for the film-forming agent to promote the penetration of ceramic particles into the pores of the membrane. Furthermore, film-forming agents often use solvents such as NMP and DMF to form a slurry for coating, which also makes it difficult for the film-forming agent to fully penetrate the pores of the membrane. Therefore, although the thermal shrinkage of the nonwoven membrane is achieved... While effectively mitigating thermal shrinkage, the coating layer on the surface of the nonwoven membrane relies on structural strength to resist its thermal contraction. However, in cases of severe thermal shrinkage, the coating layer is highly likely to detach during this process. Furthermore, if a reactive film-forming agent is applied to the nonwoven membrane, even if soluble lithium salts or other particles are generated, the capillary action of the membrane's pores makes it difficult for them to fully fill the pores and provide sufficient strength and stability for structural support. Additionally, using high pressure to promote the penetration of the coating slurry significantly impacts the membrane's structure, consequently affecting its performance and lifespan.

[0045] In one embodiment, the porosity of the nonwoven porous substrate is ≤65%.

[0046] In one embodiment, the liquid pore guiding agent has ≤7 carbon atoms. Further, the liquid pore guiding agent comprises at least one selected from ethanol, toluene, isopropanone, 2-nonanone, and cyclohexanone. Further, the liquid pore guiding agent also contains an amino group. Further, the liquid pore guiding agent further comprises triethylamine. Further, the liquid pore guiding agent comprises triethylamine and isopropanone. Further, the volume ratio of triethylamine to isopropanone is (0.2–1):3. Further, the liquid pore guiding agent comprises triethylamine, isopropanone, and toluene. Further, the volume ratio of triethylamine, isopropanone, and toluene is (0.2–0.7):2:(1–1.5).

[0047] It is understandable that when the number of carbon atoms in the liquid pore guiding agent is ≤7, and it contains amino, carbonyl, hydroxyl and / or phenyl groups, it can better eliminate capillary action and guide the expanding agent and nano-inorganic solid electrolyte into the pores of the nonwoven porous substrate. The liquid pore guiding agent tends to have high wettability to the nonwoven porous substrate, thus better guiding the expanding agent and nano-inorganic solid electrolyte into the pores of the nonwoven porous substrate. In particular, when the liquid pore guiding agent contains amino groups, it can guide the expanding agent and nano-inorganic solid electrolyte into the pores of the nonwoven porous substrate more effectively.

[0048] In one embodiment, the composite solid electrolyte comprises the following components in parts by weight: 0.2 to 1.2 parts of dispersant; 0.1 to 1 part of swelling agent; 8 to 20 parts of liquid pore guiding agent; 5 to 15 parts of adhesive; and 50 to 80 parts of nano-inorganic solid electrolyte.

[0049] In one embodiment, the expanding agent is at least one selected from alumina, calcium oxide, polyurethane, polystyrene, and polyvinyl alcohol. Further, the expanding agent includes alumina and / or calcium oxide, and further includes at least one selected from polyurethane, polystyrene, and polyvinyl alcohol.

[0050] In one embodiment, the adhesive comprises polyvinylidene fluoride.

[0051] In one embodiment, the nano-inorganic solid electrolyte is at least one of lithium titanium aluminum phosphate nano-solid electrolyte, lithium lanthanum titanium oxide nano-solid electrolyte, lithium lanthanum zirconium oxide nano-solid electrolyte, and lithium polyphosphoric sulfide nano-solid electrolyte.

[0052] In one embodiment, the dispersant is at least one of polyvinylpyrrolidone, herring oil, and polyethylene glycol.

[0053] In one embodiment, the thickness of the composite solid electrolyte coating is 3 μm to 5 μm.

[0054] In one embodiment, the pore size of the nonwoven porous substrate is 0.3 μm to 0.7 μm. Further, the nano-inorganic solid electrolyte has a D50 ≤ 20 nm. Further, the nano-inorganic solid electrolyte has a Dmax ≤ 65 nm.

[0055] In one embodiment, the nonwoven porous substrate is a natural fiber nonwoven porous substrate. Further, the main material used in the fabrication of the natural fiber nonwoven porous substrate includes cellulose and its derivatives.

[0056] In one embodiment, the nonwoven porous substrate is a synthetic fiber nonwoven porous substrate. Further, the main materials used to prepare the synthetic fiber nonwoven porous substrate are polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyethylene terephthalate, polyimide, aramid, or polypropylene.

[0057] This application also provides a method for preparing a composite membrane, used to prepare the composite membrane described in any of the above embodiments. To better understand the method for preparing the composite membrane of this application, the following further explanation is provided:

[0058] The method for preparing the composite membrane according to one embodiment includes the following steps:

[0059] S100. The adhesive, expanding agent, and nano-inorganic solid electrolyte are dispersed to obtain a mixture. It is understood that the expanding agent, adhesive, and nano-inorganic solid electrolyte contain both organic and inorganic substances, resulting in poor compatibility among them. If the adhesive is first formed into a viscous solution before being mixed with the expanding agent and nano-inorganic solid electrolyte, the dispersion effect of the nano-inorganic solid electrolyte will be affected. Therefore, preliminary mixing and dispersion of the adhesive, expanding agent, and nano-inorganic solid electrolyte in solid form is beneficial for the uniform dispersion of the nano-inorganic solid electrolyte.

[0060] S200. The dispersant, liquid pore guide, and solvent are placed in the mixture and allowed to stand. It is understood that if the dispersant, liquid pore guide, and solvent are added directly to the mixture and immediately stirred, the nano-inorganic solid electrolyte will float on the surface or settle at the bottom of the adhesive. This would require a longer stirring time or a higher stirring rate to achieve uniform dispersion of the nano-inorganic solid electrolyte. Therefore, the dispersant, liquid pore guide, and solvent are used to swell or dissolve the adhesive to form a viscous liquid. Then, the mixture is allowed to stand to ensure that the nano-inorganic solid electrolyte remains uniformly dispersed in the adhesive and swelling agent before the adhesive swells or dissolves. This allows the adhesive to form a viscous liquid, increasing the suspension capacity of the nano-inorganic solid electrolyte and reducing the likelihood of the nano-inorganic solid electrolyte floating on the surface or settling at the bottom of the adhesive, thus ensuring rapid and effective dispersion of the substances in the mixture.

[0061] S300. The mixture after static treatment is stirred and mixed to obtain the composite solid electrolyte. It can be understood that stirring and mixing the statically treated mixture mainly increases the contact between the dispersant, liquid pore-guiding solvent, and the adhesive and nano-inorganic solid electrolyte, thereby promoting the full swelling or compatibility of the adhesive. While ensuring the uniform dispersion of each substance in the mixture, it accelerates the full swelling or dissolution of the adhesive, thus improving the preparation efficiency of the composite solid electrolyte. Further, the stirring parameters are: revolution 25 rpm, dispersion 900 rpm–1100 rpm, stirring for 40 min–60 min.

[0062] S400. The composite solid electrolyte is used to fill the pores of the nonwoven porous substrate. This allows the expanding agent to be better contained and filled into the pores of the nonwoven porous substrate through the liquid pore guide, while the nano-inorganic solid electrolyte is also better contained and filled into the pores of the nonwoven porous substrate under the guidance of the liquid pore guide. Furthermore, the expanding agent and the nano-inorganic solid electrolyte are stably contained and filled into the pores of the nonwoven porous substrate through an adhesive. Thus, the expanding agent and the nano-inorganic solid electrolyte effectively buffer the pore closure of the nonwoven porous substrate under thermal action, effectively reducing the thermal shrinkage of the nonwoven porous substrate and significantly improving the structural stability of the composite membrane. In addition, the nano-inorganic solid electrolyte filling the pores of the nonwoven porous substrate, combined with the nonwoven porous substrate's porosity ≥40% and thickness ≤20μm, effectively improves the ionic conductivity of the composite membrane. Furthermore, the porous substrate of nonwoven fabric is filled with pores by coating. The coating process of nonwoven fabric diaphragm is a relatively conventional operation and will not be described in detail here.

[0063] S500. The nonwoven porous substrate after pore filling treatment is dried to obtain a composite separator. It can be understood that drying the nonwoven porous substrate promotes the drying and removal of the solvent-mixed liquid pore guiding agent in the composite separator, reducing the interference of solvent and liquid pore guiding agent on the chemical stability of various substances used in the semi-solid battery, and better ensuring the chemical stability of the semi-solid battery.

[0064] The above-described method for preparing the composite membrane involves dispersing the adhesive, expanding agent, and nano-inorganic solid electrolyte. This initial mixing and dispersion in solid form facilitates the uniform dispersion of the nano-inorganic solid electrolyte. Next, the dispersant, liquid pore-guiding agent, and solvent are placed in the mixture and allowed to stand. This causes the adhesive to form a viscous liquid, increasing its suspension capacity for the expanding agent and nano-inorganic solid electrolyte. This reduces the likelihood of the nano-inorganic solid electrolyte and expanding agent floating on the surface or settling at the bottom of the adhesive, ensuring rapid and effective dispersion of the substances in the mixture. The mixture after standing is then stirred to increase the contact between the dispersant, liquid pore-guiding agent, and solvent and the adhesive and nano-inorganic solid electrolyte, promoting sufficient swelling or compatibility of the adhesive. This ensures uniform dispersion of the substances in the mixture. The process accelerates the full swelling or dissolution of the adhesive, thereby improving the preparation efficiency of the composite solid electrolyte. This allows the expanding agent to be better contained and filled into the pores of the nonwoven porous substrate during the pore-filling process, while the nano-inorganic solid electrolyte is also better contained and filled into the pores of the nonwoven porous substrate under the guidance of the liquid pore-guiding agent. Furthermore, the expanding agent and nano-inorganic solid electrolyte are stably contained and filled into the pores of the nonwoven porous substrate through the adhesive. Thus, the expanding agent and nano-inorganic solid electrolyte effectively buffer the pore closure of the nonwoven porous substrate under thermal action, effectively reducing the thermal shrinkage of the nonwoven porous substrate and significantly improving the structural stability of the composite membrane. In addition, the filling of the nano-inorganic solid electrolyte into the pores of the nonwoven porous substrate, combined with the nonwoven porous substrate's porosity ≥40% and thickness ≤20μm, effectively improves the ionic conductivity of the composite membrane.

[0065] In one embodiment, the solvent is at least one selected from N-methylpyrrolidone, dimethylformamide, tetrahydrofuran, and acetonitrile. Further, the composite solid electrolyte comprises 22 to 30 parts by weight of solvent.

[0066] In one embodiment, the liquid pore-directing agent and solvent are placed in the mixture for a settling process, specifically including the following steps:

[0067] The dispersant and solvent are added to the mixture for initial settling. Further, the settling time is 10 min to 22 min.

[0068] Furthermore, a liquid pore-guiding agent is added to the mixture after the initial settling, and a second settling is performed. The settling time is further 8 to 15 minutes.

[0069] It is understandable that liquid pore-guiding agents, containing carbonyl, hydroxyl, and / or phenyl groups, have poor or no solubility for dispersants, expanding agents, and adhesives. Therefore, if the liquid pore-guiding agent is added to the mixture and allowed to stand, the presence of carbonyl, hydroxyl, and / or phenyl groups in the liquid pore-guiding agent will lead to accelerated agglomeration and deposition of the nano-inorganic solid electrolyte due to their strong affinity for it. Further dispersion of the nano-inorganic solid electrolyte requires prolonged or high-rate stirring. If the liquid pore-guiding agent, dispersant, and solvent are added to the mixture together, although the dispersant can provide dispersion for the nano-inorganic solid electrolyte and expanding agent in the solvent, without the suspending and containing properties of the binder, and given the lack of a binder for the nano-inorganic solid electrolyte and expanding agent, further dispersion will occur. When the proportion of electrolyte is large, a large amount of dispersant is needed to achieve uniform dispersion of the nano-inorganic solid electrolyte and the expanding agent in the solvent. However, the use of a large amount of dispersant will reduce the proportion of nano-inorganic solid electrolyte in the composite solid electrolyte coating, affecting the conductivity of the membrane. Therefore, in this application, the solvent and dispersant are added to the mixture first, causing the binder to form a viscous liquid. During the formation of the viscous liquid by the binder, the dispersing effect of the dispersant on the nano-inorganic solid electrolyte and the expanding agent, combined with the suspending and containing effect of the viscous liquid on the nano-inorganic solid electrolyte and the expanding agent, allows the nano-inorganic solid electrolyte and the expanding agent to remain uniformly dispersed in the viscous liquid throughout the standing process. This avoids the need for subsequent long-term or high-speed stirring, and achieves rapid, effective and uniform dispersion and mixing of the composite solid electrolyte.

[0070] In one embodiment, the temperature for drying the nonwoven porous substrate after pore filling treatment is 60°C to 130°C, and the drying time is 30 min to 2 h.

[0071] This application also provides a semi-solid-state battery. One embodiment of the semi-solid-state battery includes a positive electrode, a negative electrode, and a composite separator as described in any of the above embodiments, wherein the composite separator is sandwiched between the positive electrode and the negative electrode. Further, in this embodiment, the composite separator includes a non-woven porous substrate and a composite solid electrolyte coating filling the pores of the non-woven porous substrate. The non-woven porous substrate has a thickness ≤20 μm and a porosity ≥40%. The composite solid electrolyte coating includes an expanding agent, an adhesive, and a nano-inorganic solid electrolyte. The expanding agent expands with increasing temperature.

[0072] The aforementioned semi-solid-state battery uses a composite separator, which effectively improves the safety and electrochemical performance of the semi-solid-state battery.

[0073] Compared with the prior art, the present invention has at least the following advantages:

[0074] The composite separator of this invention contains an expanding agent and nano-inorganic solid electrolyte in the composite solid electrolyte coating. A dispersant promotes the uniform dispersion of the expanding agent and nano-inorganic solid electrolyte in the composite solid electrolyte coating. Furthermore, under the guidance of a liquid pore-guiding agent, the expanding agent and nano-inorganic solid electrolyte effectively penetrate and fill the pores of the nonwoven porous substrate. Since the expanding agent expands with increasing temperature, when the temperature of the composite separator rises, the expanding agent filling the pores of the nonwoven porous substrate expands, thus strengthening the structural support for the nonwoven porous substrate during thermal shrinkage. Furthermore, the nano-inorganic solid electrolyte, combined with the nonwoven porous substrate… The structural support provided by the composite solid electrolyte coating during thermal shrinkage of the substrate ensures that even under severe thermal shrinkage of the nonwoven porous substrate, the composite solid electrolyte coating still provides good structural support, effectively reducing the thermal shrinkage of the composite separator. Furthermore, the composite solid electrolyte fills the pores of the nonwoven porous substrate, promoting the formation of a self-healing SEI film in these pores, which effectively blocks lithium dendrites. Combined with the mechanical barrier provided by the composite solid electrolyte and the expansion agent, the structural stability of the composite separator is effectively improved. Moreover, the composite solid electrolyte filling the pores of the nonwoven porous substrate effectively ensures the ionic conductivity of the composite separator.

[0075] The following are some specific examples. Where %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively cover all possible scenarios, and unless otherwise specified, the materials used in the following examples are commercially available.

[0076] Example 1

[0077] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 10nm, Dmax is 50nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0078] Add the dispersant and solvent to the mixture and let it stand for 10 minutes. Then, add the liquid pore guide agent and let it stand for 8 minutes.

[0079] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0080] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 10 μm, a porosity of 40%, and a pore diameter of 0.3 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0081] Example 2

[0082] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 20nm, Dmax is 65nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0083] Add the dispersant and solvent to the mixture and let it stand for 10 minutes. Then, add the liquid pore guide agent and let it stand for 8 minutes.

[0084] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0085] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 10 μm, a porosity of 40%, and a pore diameter of 0.3 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0086] Example 3

[0087] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 10nm, Dmax is 50nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0088] Add the dispersant and solvent to the mixture and let it stand for 15 minutes. Then, add the liquid pore guide agent and let it stand for 12 minutes.

[0089] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0090] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 10 μm, a porosity of 40%, and a pore diameter of 0.3 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0091] Example 4

[0092] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 10nm, Dmax is 50nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0093] Add the dispersant and solvent to the mixture and let it stand for 22 minutes. Then, add the liquid pore guide agent and let it stand for 15 minutes.

[0094] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0095] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 10 μm, a porosity of 40%, and a pore diameter of 0.3 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0096] Example 5

[0097] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 10nm, Dmax is 50nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0098] Add the dispersant and solvent to the mixture and let it stand for 15 minutes. Then, add the liquid pore guide agent and let it stand for 12 minutes.

[0099] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0100] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 15 μm, a porosity of 50%, and a pore diameter of 0.5 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0101] Example 6

[0102] The adhesive, expanding agent and nano-inorganic solid electrolyte (D50 is 10nm, Dmax is 50nm) were uniformly dispersed, and the mixture was stirred for 20 minutes at 25 rpm and 400 rpm to obtain the mixture.

[0103] Add the dispersant and solvent to the mixture and let it stand for 15 minutes. Then, add the liquid pore guide agent and let it stand for 12 minutes.

[0104] The mixture after standing was stirred and mixed, with a revolution speed of 25 rpm, a dispersion speed of 900 rpm, and a stirring time of 60 min to obtain the composite solid electrolyte;

[0105] A composite solid electrolyte was coated onto a nonwoven porous substrate with a thickness of 20 μm, a porosity of 65%, and a pore size of 0.7 μm. The substrate was then dried at 90°C for 30 min, resulting in a composite solid electrolyte coating with a thickness of 3 μm on the nonwoven porous substrate after drying.

[0106] The following is a detailed breakdown of each component and its corresponding usage in the embodiments, as shown in Table 1:

[0107] Table 1

[0108]

[0109]

[0110] The performance of the diaphragm in the examples was tested, and the results are shown in Table 2:

[0111] Table 2

[0112]

[0113] It should be noted that Examples 5-1 to 5-11 used the same composite separator preparation method as Example 5, differing only in the materials used; additionally, the thermal shrinkage rate was recorded after treatment at 180°C for 30 min; the maximum puncture force was tested according to the puncture test standard GBT 36363-2018 (test speed 100 mm / min); the composite separators from each example were applied to 18650-3000mAh small cylindrical batteries, with DCR test method: IEC 61960; the 3C rate discharge capacity retention rate test method: fully charged with a 0.5C current, and the discharge capacity was tested with 0.5C and 3C currents respectively, and the 3C current discharge capacity / 0.5C current discharge capacity is the rate discharge capacity retention rate.

[0114] From Table 2, Figures 2 to 3 It can be seen that the composite separators of each embodiment have strong high-temperature shrinkage resistance and puncture resistance. In addition, please refer to Table 1. From Table 1 and Table 2, it can be seen that when the composite separators of this application are applied to semi-solid batteries, their ionic conductivity is high and their cycle performance is good. In particular, the composite separators in Examples 5-11 and 5-12 have even better ionic conductivity and cycle performance.

[0115] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A composite separator, characterized by, It includes a nonwoven porous substrate and a composite solid electrolyte filling the pores of the nonwoven porous substrate; The thickness of the nonwoven porous substrate is ≤20μm, and the porosity is ≥40%. The composite solid electrolyte includes a dispersant, a swelling agent, a liquid pore guiding agent, a binder, and a nano-inorganic solid electrolyte; The expanding agent can expand as the temperature increases; The liquid pore guiding agent contains at least one of carbonyl, hydroxyl and phenyl groups, and the liquid pore guiding agent is dried and removed after the composite solid electrolyte fills the pores of the nonwoven porous substrate; The expanding agent is at least one of aluminum oxide, calcium oxide, polyurethane, polystyrene, and polyvinyl alcohol. The liquid pore guiding agent includes at least one of ethanol, toluene, isopropanone, 2-nonanone, and cyclohexanone; The nano-inorganic solid electrolyte is at least one of lithium titanium aluminum phosphate nano-solid electrolyte, lithium lanthanum titanium oxide nano-solid electrolyte, lithium lanthanum zirconium oxide nano-solid electrolyte, and lithium polyphosphoric sulfide nano-solid electrolyte.

2. The composite diaphragm according to claim 1, characterized in that, The adhesive includes polyvinylidene fluoride.

3. The composite diaphragm according to claim 1, characterized in that, The number of carbon atoms in the liquid pore guiding agent is ≤7.

4. The composite diaphragm according to claim 1, characterized in that, The dispersant is at least one of polyvinylpyrrolidone, herring oil, and polyethylene glycol.

5. The composite diaphragm according to claim 1, characterized in that, The nonwoven porous substrate is a natural fiber nonwoven porous substrate or a synthetic fiber nonwoven porous substrate.

6. The composite diaphragm according to claim 1, characterized in that, The pore size of the nonwoven porous substrate is 0.3μm~0.7μm; The nano-inorganic solid electrolyte has a D50 ≤ 20 nm.

7. The composite diaphragm according to claim 1, characterized in that, The composite solid electrolyte comprises the following components in parts by weight: Dispersant: 0.2 to 1.2 parts; 0.1 to 1 part of expanding agent; 8 to 20 parts of liquid pore guiding agent; 5 to 15 parts adhesive; 50 to 80 parts of nano-inorganic solid electrolyte.

8. A method for preparing a composite diaphragm, characterized in that, The method for preparing the composite separator according to any one of claims 1 to 7 comprises the following steps: The adhesive, expanding agent, and nano-inorganic solid electrolyte are dispersed to obtain a mixture. The dispersant, liquid pore guide agent and solvent are placed in the mixture and allowed to stand. The mixture after static treatment is stirred and mixed to obtain the composite solid electrolyte. The composite solid electrolyte is used to fill the pores of the nonwoven porous substrate. The nonwoven porous substrate after pore filling treatment is dried to obtain a composite diaphragm.

9. The method for preparing the composite diaphragm according to claim 8, characterized in that, The drying temperature for the nonwoven porous substrate after pore filling treatment is 60℃~130℃.

10. A semi-solid-state battery, characterized in that, The invention includes a positive electrode, a negative electrode, and a composite separator according to any one of claims 1 to 7, wherein the composite separator is sandwiched between the positive electrode and the negative electrode.

Images