Composite diaphragm, preparation method thereof and semi-solid-state battery

Abstract

The invention provides a composite diaphragm, a preparation method thereof and a semi-solid battery. The composite diaphragm comprises a non-woven fabric porous substrate and a composite solid electrolyte coating filled in pores of the non-woven fabric porous substrate. Wherein the thickness of the non-woven fabric porous substrate is smaller than or equal to 20 microns, and the porosity is larger than or equal to 40%. The composite solid electrolyte coating comprises a dispersing agent, an expanding agent, a liquid pore guiding agent, an adhesive and a nano inorganic solid electrolyte. And the expanding agent can expand along with the temperature rise. The liquid pore guiding agent contains at least one of carbonyl, hydroxyl and phenyl, and the liquid pore guiding agent is dried and removed after the pores of the non-woven fabric porous substrate are filled with the composite solid electrolyte. The composite diaphragm can well reduce thermal shrinkage, and is good in structural stability and small in influence on ionic conductivity.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a composite diaphragm and a preparation method thereof, and a semi-solid battery. Background Art

[0002] Semi-solid-state batteries are a new type of batteries that have higher energy density and longer service life than traditional batteries, and have better safety performance. Therefore, semi-solid-state batteries are widely used in drones, electric vehicles and other fields, and show great application prospects.

[0003] Since the electrolyte of the semi-solid battery is semi-solid and cannot effectively isolate the negative electrode and the positive electrode, in actual use, the use of the diaphragm is mostly maintained. For example, the Chinese invention patent application with application number 201610988814.X uses a polypropylene porous membrane as the matrix of the diaphragm. However, the micropores of the polyolefin substrate will gradually close at high temperature, which manifests as overall shrinkage. When a short circuit occurs inside the semi-solid battery, it will shrink a lot, thereby exacerbating thermal runaway.

[0004] In order to reduce the shrinkage of the diaphragm, such as the Chinese invention patent application with application number 202210425385.0, ceramic particles are 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 diaphragm. Although the thermal shrinkage of the diaphragm is better avoided and the impact on ionic conductivity is reduced, the ceramic particles are easy to fall off and the blocking effect on lithium dendrites is poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a composite diaphragm and a preparation method thereof, as well as a semi-solid battery that can better reduce thermal shrinkage, has good structural stability and has little effect on ionic conductivity.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A composite diaphragm, comprising a non-woven porous substrate and a composite solid electrolyte coating filled in the pores of the non-woven porous substrate;

[0008] Wherein, the thickness of the non-woven porous substrate is ≤20 μm, and the porosity is ≥40%;

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

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

[0011] The liquid pore directing agent contains at least one of a carbonyl group, a hydroxyl group and a phenyl group, and the liquid pore directing agent is dried and removed after the composite solid electrolyte is filled in the pores of the non-woven fabric porous substrate.

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

[0013] In one embodiment, the adhesive includes 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 polyphosphide sulfide nano solid electrolyte.

[0015] In one embodiment, the number of carbon atoms in the liquid pore guiding agent is ≤7.

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

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

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

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

[0020] The nano inorganic solid electrolyte has a D50 of ≤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 diaphragm, used to prepare the composite diaphragm described in any of the above embodiments, the method for preparing the composite diaphragm comprising the following steps:

[0025] Dispersing the adhesive, the expander and the nano inorganic solid electrolyte to obtain a mixture;

[0026] placing a dispersant, a liquid pore directing agent and a solvent in the mixture and performing a static treatment;

[0027] Stirring and mixing the mixed material after the static treatment to obtain the composite solid electrolyte;

[0028] The composite solid electrolyte is used to perform pore filling treatment on a non-woven porous substrate;

[0029] The non-woven fabric porous substrate after the pore filling treatment is dried to obtain a composite separator.

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

[0031] A semi-solid battery comprises a positive electrode sheet, a negative electrode sheet and the composite diaphragm described in any one of the above embodiments, wherein the composite diaphragm is sandwiched between the positive electrode sheet and the negative electrode sheet.

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

[0033] The composite diaphragm of the present invention allows the composite solid electrolyte coating to contain an expansion agent and a nano inorganic solid electrolyte, and the dispersant promotes the expansion agent and the nano inorganic solid electrolyte to be uniformly dispersed in the composite solid electrolyte coating. Furthermore, under the guidance of the liquid pore guiding agent, the expansion agent and the nano inorganic solid electrolyte can better penetrate into the pores filled in the non-woven porous substrate. Since the expansion agent can expand with the increase of temperature, when the temperature of the composite diaphragm rises, the expansion agent filled in the pores of the non-woven porous substrate will expand to strengthen the structural support effect of the non-woven porous substrate during thermal contraction, and the nano inorganic solid electrolyte can be combined with the non-woven porous substrate to form a composite diaphragm. The structural support effect of the substrate during thermal shrinkage makes it possible for the composite solid electrolyte coating to still have a good structural support effect on the non-woven porous substrate when the thermal shrinkage of the non-woven porous substrate is more severe, effectively reducing the thermal shrinkage of the composite diaphragm, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, so that a self-healing SEI film can be formed in the pores of the non-woven porous substrate, which can effectively block lithium dendrites. Combined with the mechanical blocking of the composite solid electrolyte and the expander itself, the structural stability of the composite diaphragm is effectively improved, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, which effectively ensures the ionic conductivity of the composite diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A flow chart of a method for preparing a composite diaphragm according to an embodiment of the present invention;

[0036] Figures 2 to 3 The puncture test data of the composite diaphragm of Examples 5-12. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

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

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0040] The present application provides a composite diaphragm. In order to better understand the composite diaphragm of the present application, the composite diaphragm of the present application is further explained below:

[0041] A composite diaphragm in one embodiment includes a non-woven porous substrate and a composite solid electrolyte coating filled in the pores of the non-woven porous substrate. The thickness of the non-woven porous substrate is ≤20 μm, and the porosity is ≥40%. The composite solid electrolyte coating includes a dispersant, an expander, a liquid pore guiding agent, an adhesive, and a nano-inorganic solid electrolyte. The expander can expand with increasing temperature. The liquid pore guiding agent contains at least one of a carbonyl group, a hydroxyl group, and a phenyl group, and the liquid pore guiding agent is dried and removed after the composite solid electrolyte is filled in the pores of the non-woven porous substrate.

[0042] The composite diaphragm mentioned above allows the composite solid electrolyte coating to contain an expansion agent and a nano inorganic solid electrolyte, and the dispersant promotes the expansion agent and the nano inorganic solid electrolyte to be evenly dispersed in the composite solid electrolyte coating. Furthermore, under the guidance of the liquid pore guiding agent, the expansion agent and the nano inorganic solid electrolyte can better penetrate into the pores filled in the non-woven porous substrate. Since the expansion agent can expand with the increase of temperature, when the temperature of the composite diaphragm rises, the expansion agent filled in the pores of the non-woven porous substrate will expand to strengthen the structural support effect of the non-woven porous substrate during thermal contraction, and the nano inorganic solid electrolyte can be combined with the non-woven porous substrate to form a pore-forming structure. The structural support effect of the substrate during thermal shrinkage makes it possible for the composite solid electrolyte coating to still have a good structural support effect on the non-woven porous substrate when the thermal shrinkage of the non-woven porous substrate is more severe, effectively reducing the thermal shrinkage of the composite diaphragm, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, so that a self-healing SEI film can be formed in the pores of the non-woven porous substrate, which can effectively block lithium dendrites. Combined with the mechanical blocking of the composite solid electrolyte and the expander itself, the structural stability of the composite diaphragm is effectively improved, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, which effectively ensures the ionic conductivity of the composite diaphragm.

[0043] It can be understood that the slurry is attached to the porous sheet by coating, and it is difficult for the slurry to fully fill the micropores or nanopores on the porous sheet, that is, the composite solid electrolyte is coated on the non-woven porous substrate to form a coating. Since the pore size is less than 50μm, there is a capillary phenomenon in the pores, which makes it difficult for substances such as nano-inorganic solid electrolytes to fully and effectively fill the pores of the non-woven porous substrate. The only state is that there is a small amount of nano-inorganic solid electrolyte at the end of the pores of the non-woven porous substrate, so that it is more to use the structural strength of the composite solid electrolyte coating to slow down the thermal shrinkage of the non-woven porous substrate. In the case of more severe thermal shrinkage of the non-woven porous substrate, the composite solid electrolyte coating is easy to fall off from the non-woven porous substrate, thereby causing the non-woven porous substrate to shrink thermally. In the present application In the method, the composite solid electrolyte is coated in a manner, and the nano-inorganic solid electrolyte and the expansion agent are guided into the pores of the non-woven porous substrate by the liquid pore guiding agent for full and effective filling, so that the thermal shrinkage of the non-woven porous substrate is more intense, and the composite solid electrolyte coating still has a good structural support effect on the non-woven porous substrate, which effectively realizes the reduction of thermal shrinkage of the composite diaphragm, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, so that the pores of the non-woven porous substrate can form a self-healing SEI film, which can effectively block lithium dendrites, and combined with the mechanical blocking of the composite solid electrolyte itself, the structural stability of the composite diaphragm is effectively improved, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, which effectively ensures the ionic conductivity of the composite diaphragm.

[0044] It should be noted that, for coating a ceramic layer on the non-woven membrane, it is difficult for it to fully fill the pores of the non-woven membrane. Further adding a film-forming agent to adhere to the ceramic layer, although it can enhance the adhesion strength of the ceramic layer on the non-woven membrane, in fact, the film-forming agent is difficult to promote the ceramic particles in the ceramic layer to penetrate into the pores of the non-woven membrane, and the film-forming agent is mostly formed into a slurry using solvents such as NMP and DMF for coating. At this time, the film-forming agent is also difficult to fully penetrate into the pores of the non-woven membrane. Therefore, although the heat shrinkage of the non-woven membrane is achieved, It can effectively reduce the heat, but it is based on the structural strength of the coating layer on the surface of the non-woven membrane to resist the thermal shrinkage of the non-woven membrane. If the thermal shrinkage of the non-woven membrane is more severe, the coating layer will also fall off with a greater probability when the non-woven membrane shrinks. In addition, if the reactive film-forming agent is coated on the non-woven membrane, similarly, even if soluble lithium salts or other particles are generated, due to the capillary action of the pores of the non-woven membrane, it is still difficult to fully fill the pores of the non-woven membrane to play a structural support role with higher strength and stability. In addition, if high pressure is used to promote the penetration of the slurry of the coating layer, it will have a greater impact on the structure of the non-woven membrane, thereby affecting its performance and service life.

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

[0046] In one embodiment, the number of carbon atoms in the liquid pore guiding agent is ≤7. Further, the liquid pore guiding agent includes at least one of ethanol, toluene, isopropyl ketone, 2-nonanone and cyclohexanone. Further, the liquid pore guiding agent also contains amino groups. Further, the liquid pore guiding agent also includes triethylamine. Further, the liquid pore guiding agent includes triethylamine and isopropyl ketone. Further, the volume ratio of triethylamine and isopropyl ketone is (0.2-1):3. Further, the liquid pore guiding agent includes triethylamine, isopropyl ketone and toluene. Further, the volume ratio of triethylamine, isopropyl ketone and toluene is (0.2-0.7):2:(1-1.5).

[0047] It can be understood 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 the capillary action and better guide the expansion agent and the nano-inorganic solid electrolyte into the pores of the non-woven porous substrate. The liquid pore guiding agent tends to have a higher wettability to the non-woven porous substrate, thereby better guiding the expansion agent and the nano-inorganic solid electrolyte into the pores of the non-woven porous substrate. In particular, when the liquid pore guiding agent contains amino groups, it can more effectively guide the expansion agent and the nano-inorganic solid electrolyte into the pores of the non-woven porous substrate.

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

[0049] In one embodiment, the expansion agent is at least one of aluminum oxide, calcium oxide, polyurethane, polystyrene and polyvinyl alcohol. Further, the expansion agent includes aluminum oxide and / or calcium oxide, and the expansion agent also includes at least one of polyurethane, polystyrene and polyvinyl alcohol.

[0050] In one embodiment, the adhesive includes 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 polyphosphide sulfide nano solid electrolyte.

[0052] In one embodiment, the dispersant is at least one of polyvinyl pyrrolidone, 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 non-woven porous substrate is 0.3 μm to 0.7 μm. Further, the nano inorganic solid electrolyte D50 ≤ 20 nm. Further, the nano inorganic solid electrolyte Dmax ≤ 65 nm.

[0055] In one embodiment, the non-woven fabric porous substrate is a natural fiber non-woven fabric porous substrate. Furthermore, the main preparation material of the natural fiber non-woven fabric porous substrate includes cellulose and its derivatives.

[0056] In one embodiment, the non-woven fabric porous substrate is a synthetic fiber non-woven fabric porous substrate. Further, the synthetic fiber non-woven fabric porous substrate is mainly made of polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyethylene terephthalate, polyimide, aramid or polypropylene.

[0057] The present application also provides a method for preparing a composite membrane, which is used to prepare the composite membrane described in any of the above embodiments. In order to better understand the method for preparing the composite membrane of the present application, the method for preparing the composite membrane of the present application is further explained below:

[0058] A method for preparing a composite diaphragm according to one embodiment comprises the following steps:

[0059] S100, dispersing the adhesive, the swelling agent and the nano inorganic solid electrolyte to obtain a mixture. It can be understood that the swelling agent, the adhesive and the nano inorganic solid electrolyte include organic and inorganic substances, which makes the adhesive, the swelling agent and the nano inorganic solid electrolyte have poor compatibility. If the adhesive is first formed into a viscous solution and then mixed with the swelling agent and the nano inorganic solid electrolyte, the dispersion effect of the nano inorganic solid electrolyte will be affected. Therefore, the adhesive, the swelling agent and the nano inorganic solid electrolyte are first preliminarily mixed and dispersed in a solid form, which is conducive to the uniform dispersion of the nano inorganic solid electrolyte.

[0060] S200, placing a dispersant, a liquid pore guiding agent and a solvent in the mixture for static treatment. It can be understood that if the dispersant, the liquid pore guiding agent and the solvent are directly added to the mixture and stirred and mixed immediately, the nano inorganic solid electrolyte will float on the surface or deposit on the lower part in the adhesive, and then a long time or a large rate of stirring is required to achieve uniform dispersion of the nano inorganic solid electrolyte, so the dispersant, the liquid pore guiding agent and the solvent are used to swell or dissolve the adhesive to form a viscous liquid, and then the nano inorganic solid electrolyte is kept uniformly dispersed in the adhesive and the swelling agent before the adhesive swells or dissolves by a static manner, that is, the mixture is static, so that the adhesive forms a viscous liquid, thereby increasing the suspension capacity of the nano inorganic solid electrolyte, reducing the floating of the nano inorganic solid electrolyte on the surface or the deposition of the lower part in the adhesive, and better ensuring the rapid and effective dispersion of various substances in the mixture.

[0061] S300, stirring and mixing the mixture after the static treatment to obtain the composite solid electrolyte. It can be understood that the main function of stirring and mixing the static treated mixture is to increase the sufficient contact between the dispersant and the liquid pore guiding agent solvent and the adhesive and the nano inorganic solid electrolyte, thereby promoting the full swelling or compatibility of the adhesive, and accelerating the full swelling or dissolution of the adhesive while ensuring the uniform dispersion of each substance in the mixture, thereby improving the preparation efficiency of the composite solid electrolyte. Further, the stirring parameters are: revolution 25rpm, dispersion 900rpm~1100rpm, and stirring 40min~60min.

[0062] S400, using the composite solid electrolyte to perform pore filling treatment on the non-woven porous substrate. It can be understood that the expansion agent is better accommodated and filled in the pores of the non-woven porous substrate through the liquid pore guide, and the nano inorganic solid electrolyte is also better accommodated and filled in the pores of the non-woven porous substrate under the guidance of the liquid pore guide. Further, the expansion agent and the nano inorganic solid electrolyte are stably accommodated and filled in the pores of the non-woven porous substrate through the adhesive. In this way, the expansion agent and the nano inorganic solid electrolyte effectively buffer the pore closure of the non-woven porous substrate under the action of heat, better reduce the thermal shrinkage of the non-woven porous substrate, and improve the structural stability of the composite diaphragm; in addition, the nano inorganic solid electrolyte is filled in the pores of the non-woven porous substrate, combined with the porosity of the non-woven porous substrate ≥40% and the thickness ≤20μm, which effectively improves the ionic conductivity of the composite diaphragm. Furthermore, the non-woven porous substrate is subjected to pore filling treatment by coating. The coating process of the non-woven membrane is a relatively conventional operation and will not be described in detail here.

[0063] S500, drying the non-woven porous substrate after the pore filling treatment to obtain a composite separator. It can be understood that drying the non-woven porous substrate promotes the drying and removal of the solvent mixed with the liquid pore guiding agent in the composite separator, reduces the interference of the solvent and the liquid pore guiding agent with the chemical stability of various substances used in the semi-solid battery, and better ensures the chemical stability of the semi-solid battery.

[0064] The preparation method of the composite diaphragm is as follows: the adhesive, the swelling agent and the nano inorganic solid electrolyte are dispersed, so that the adhesive, the swelling agent and the nano inorganic solid electrolyte are first preliminarily mixed and dispersed in a solid form, which is conducive to the uniform dispersion of the nano inorganic solid electrolyte; the dispersant, the liquid pore guiding agent and the solvent are placed in the mixture for static treatment, so that the adhesive forms a viscous liquid, thereby increasing the suspension holding strength of the swelling agent and the nano inorganic solid electrolyte, reducing the floating of the nano inorganic solid electrolyte and the swelling agent on the surface or the deposition of the lower part in the adhesive, and better ensuring the rapid and effective dispersion of the various substances in the mixture; the mixture after the static treatment is stirred and mixed to increase the sufficient contact between the dispersant, the liquid pore guiding agent solvent and the adhesive and the nano inorganic solid electrolyte, respectively, thereby promoting the full swelling or compatibility of the adhesive, and under the condition of ensuring the uniform dispersion of the various substances in the mixture, adding The invention speeds up the full swelling or dissolution of the adhesive, thereby improving the preparation efficiency of the composite solid electrolyte, so that in the pore filling process, the expansion agent is better accommodated and filled in the pores of the non-woven porous substrate through the liquid pore guiding agent, and the nano inorganic solid electrolyte is also better accommodated and filled in the pores of the non-woven porous substrate under the guidance of the liquid pore guiding agent. Further, the expansion agent and the nano inorganic solid electrolyte are stably accommodated and filled in the pores of the non-woven porous substrate through the adhesive. In this way, the expansion agent and the nano inorganic solid electrolyte effectively buffer the pore closure of the non-woven porous substrate under the action of heat, better reduce the thermal shrinkage of the non-woven porous substrate, and effectively improve the structural stability of the composite diaphragm; in addition, the nano inorganic solid electrolyte is filled in the pores of the non-woven porous substrate, combined with the porosity of the non-woven porous substrate ≥40% and the thickness ≤20μm, which effectively improves the ionic conductivity of the composite diaphragm.

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

[0066] In one embodiment, the liquid pore directing agent and the solvent are placed in the mixture for static treatment, which specifically includes the following steps:

[0067] The dispersant and the solvent are added to the mixture and allowed to stand for a preliminary period of time, preferably for 10 to 22 minutes.

[0068] Furthermore, a liquid pore guiding agent is added to the mixture after the initial standing to perform a secondary standing. Furthermore, the standing time is 8 minutes to 15 minutes.

[0069] It can be understood that the liquid pore directing agent contains carbonyl, hydroxyl and / or phenyl groups, and has poor solubility in dispersants, expanders and adhesives, or cannot dissolve dispersants, expanders and adhesives. Therefore, if the liquid pore directing agent is first added to the mixture and allowed to stand, since the liquid pore directing agent contains carbonyl, hydroxyl and / or phenyl groups, it has a strong affinity for the nano-inorganic solid electrolyte, thereby causing accelerated agglomeration and deposition of the nano-inorganic solid electrolyte, and further dispersion of the nano-inorganic solid electrolyte requires a longer time or a higher rate of stirring; if the liquid pore directing agent, dispersant and solvent are added to the mixture together, although the dispersant can provide a dispersion effect of the nano-inorganic solid electrolyte and the expander in the solvent, on the basis of the absence of a binder to suspend and accommodate the nano-inorganic solid electrolyte and the expander, and on the basis of the nano-inorganic solid electrolyte When the proportion of electrolyte is relatively large, more dispersant needs to be added to achieve uniform dispersion of nano-inorganic solid electrolyte and swelling agent in the solvent. The use of more dispersant will cause the proportion of nano-inorganic solid electrolyte in the composite solid electrolyte coating to decrease, affecting the conductive properties of the diaphragm. Therefore, in the present application, the solvent and dispersant are first added to the mixture to prompt the binder to form a viscous liquid first. In the process of the binder forming the viscous liquid, the dispersing effect of the dispersant on the nano-inorganic solid electrolyte and the swelling agent is combined with the suspension and containment effect of the viscous liquid on the nano-inorganic solid electrolyte and the swelling agent, so that during the entire standing process, the nano-inorganic solid electrolyte and the swelling agent can still be uniformly dispersed in the viscous liquid, avoiding subsequent long-term or high-speed stirring, and achieving rapid, effective and uniform dispersion and mixing of the composite solid electrolyte.

[0070] In one embodiment, the non-woven fabric porous substrate after the pore filling treatment is dried at a temperature of 60° C. to 130° C., and the drying time is 30 min to 2 h.

[0071] The present application also provides a semi-solid battery. A semi-solid battery of one embodiment includes a positive electrode sheet, a negative electrode sheet and a composite diaphragm as described in any of the above embodiments, wherein the composite diaphragm is sandwiched between the positive electrode sheet and the negative electrode sheet. Furthermore, in this embodiment, the composite diaphragm includes a non-woven porous substrate and a composite solid electrolyte coating filled in the pores of the non-woven porous substrate. The thickness of the non-woven porous substrate is ≤20μm and the porosity is ≥40%. The composite solid electrolyte coating includes an expander, an adhesive and a nano-inorganic solid electrolyte. The expander may expand as the temperature rises.

[0072] The above-mentioned semi-solid battery adopts a composite diaphragm, which effectively improves the safety and electrochemical performance of the semi-solid battery.

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

[0074] The composite diaphragm of the present invention allows the composite solid electrolyte coating to contain an expansion agent and a nano inorganic solid electrolyte, and the dispersant promotes the expansion agent and the nano inorganic solid electrolyte to be uniformly dispersed in the composite solid electrolyte coating. Furthermore, under the guidance of the liquid pore guiding agent, the expansion agent and the nano inorganic solid electrolyte can better penetrate into the pores filled in the non-woven porous substrate. Since the expansion agent can expand with the increase of temperature, when the temperature of the composite diaphragm rises, the expansion agent filled in the pores of the non-woven porous substrate will expand to strengthen the structural support effect of the non-woven porous substrate during thermal contraction, and the nano inorganic solid electrolyte can be combined with the non-woven porous substrate to form a composite diaphragm. The structural support effect of the substrate during thermal shrinkage makes it possible for the composite solid electrolyte coating to still have a good structural support effect on the non-woven porous substrate when the thermal shrinkage of the non-woven porous substrate is more severe, effectively reducing the thermal shrinkage of the composite diaphragm, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, so that a self-healing SEI film can be formed in the pores of the non-woven porous substrate, which can effectively block lithium dendrites. Combined with the mechanical blocking of the composite solid electrolyte and the expander itself, the structural stability of the composite diaphragm is effectively improved, and the composite solid electrolyte is filled in the pores of the non-woven porous substrate, which effectively ensures the ionic conductivity of the composite diaphragm.

[0075] Some specific examples are listed below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

[0076] Example 1

[0077] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 10 nm, Dmax is 50 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0078] The dispersant and solvent were added to the mixture and allowed to stand for 10 minutes, and then the liquid pore directing agent was added and allowed to stand for 8 minutes;

[0079] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0080] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the thickness of the non-woven porous substrate is 10 μm, the porosity is 40%, and the pore size is 0.3 μm. The substrate is then dried at 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0081] Example 2

[0082] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 20 nm, Dmax is 65 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0083] The dispersant and solvent were added to the mixture and allowed to stand for 10 minutes, and then the liquid pore directing agent was added and allowed to stand for 8 minutes;

[0084] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0085] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the thickness of the non-woven porous substrate is 10 μm, the porosity is 40%, and the pore size is 0.3 μm. The substrate is then dried at 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0086] Example 3

[0087] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 10 nm, Dmax is 50 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0088] The dispersant and solvent were added to the mixture and allowed to stand for 15 minutes, and then the liquid pore directing agent was added and allowed to stand for 12 minutes;

[0089] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0090] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the thickness of the non-woven porous substrate is 10 μm, the porosity is 40%, and the pore size is 0.3 μm. The substrate is then dried at 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0091] Example 4

[0092] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 10 nm, Dmax is 50 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0093] The dispersant and solvent were added to the mixture and allowed to stand for 22 minutes, and then the liquid pore directing agent was added and allowed to stand for 15 minutes;

[0094] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0095] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the thickness of the non-woven porous substrate is 10 μm, the porosity is 40%, and the pore size is 0.3 μm. The substrate is then dried at 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0096] Example 5

[0097] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 10 nm, Dmax is 50 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0098] The dispersant and solvent were added to the mixture and allowed to stand for 15 minutes, and then the liquid pore directing agent was added and allowed to stand for 12 minutes;

[0099] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0100] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the non-woven porous substrate has a thickness of 15 μm, a porosity of 50%, and a pore size of 0.5 μm, and then dried at a temperature of 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0101] Example 6

[0102] The adhesive, the expander and the nano inorganic solid electrolyte (D50 is 10 nm, Dmax is 50 nm) are uniformly dispersed, the mixture is revolved at 25 rpm, dispersed at 400 rpm, and stirred for 20 min to obtain a mixture;

[0103] The dispersant and solvent were added to the mixture and allowed to stand for 15 minutes, and then the liquid pore directing agent was added and allowed to stand for 12 minutes;

[0104] The mixture after standing was stirred and mixed, revolved at 25 rpm, dispersed at 900 rpm, and stirred for 60 minutes to obtain the composite solid electrolyte;

[0105] The composite solid electrolyte is coated on a non-woven porous substrate, wherein the non-woven porous substrate has a thickness of 20 μm, a porosity of 65%, and a pore size of 0.7 μm, and then dried at a temperature of 90° C. for 30 minutes. After drying, the thickness of the composite solid electrolyte coating formed on the non-woven porous substrate is 3 μm.

[0106] The following is an example, and the details of each component and its corresponding usage are shown in Table 1:

[0107] Table 1

[0108]

[0109]

[0110] The performance test of the diaphragm in the embodiment is carried out, and the results are shown in Table 2:

[0111] Table 2

[0112]

[0113] It should be noted that Examples 5-1 to 5-11 adopt the same preparation method of the composite diaphragm as Example 5, except that the materials used are different; in addition, the thermal shrinkage rate is recorded after treatment at 180°C for 30 minutes; the maximum puncture force is tested according to the puncture test standard GBT 36363-2018 (test speed 100 mm / min); the composite diaphragm in each embodiment is applied to 18650-3000mAh small cylindrical batteries, DCR test method: IEC 61960; 3C rate discharge capacity retention rate test method: fully charged with 0.5C current, and the discharge capacity is tested at 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 membranes of each embodiment have strong high-temperature shrinkage resistance and puncture resistance. In addition, please refer to Table 1. It can be seen from Table 1 and Table 2 that when the composite membrane of the present application is applied to a semi-solid battery, its ion conductivity is high and the cycle performance is good, especially when the composite membranes in Examples 5-11 and 5-12 are used, its ion conductivity and cycle performance are better.

[0115] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A composite diaphragm, characterized in that: It includes a non-woven porous substrate and a composite solid electrolyte filled in the pores of the non-woven porous substrate; Wherein, the thickness of the non-woven porous substrate is ≤20 μm, and the porosity is ≥40%; The composite solid electrolyte comprises a dispersant, an expander, a liquid pore guiding agent, an adhesive and a nano inorganic solid electrolyte; The expansion agent can expand as the temperature increases; The liquid pore directing agent contains at least one of a carbonyl group, a hydroxyl group and a phenyl group, and the liquid pore directing agent is dried and removed after the composite solid electrolyte is filled in the pores of the non-woven fabric porous substrate.

2. The composite diaphragm according to claim 1, characterized in that: The expansion agent is at least one of aluminum oxide, calcium oxide, polyurethane, polystyrene and polyvinyl alcohol; and / or, The adhesive comprises polyvinylidene fluoride; and / or, 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 polyphosphide sulfide nano solid electrolyte.

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 liquid pore guiding agent includes at least one of ethanol, toluene, isopropyl ketone, 2-nonanone and cyclohexanone; and / or, The dispersant is at least one of polyvinyl pyrrolidone, herring oil and polyethylene glycol.

5. The composite diaphragm according to claim 1, characterized in that: The non-woven fabric porous substrate is a natural fiber non-woven fabric porous substrate or a synthetic fiber non-woven fabric porous substrate.

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

7. The composite diaphragm according to claim 1, characterized in that: The composite solid electrolyte comprises the following components in parts by mass:

8. A method for preparing a composite diaphragm, characterized in that: The composite diaphragm according to any one of claims 1 to 7 is prepared, wherein the preparation method of the composite diaphragm comprises the following steps: Dispersing the adhesive, the expander and the nano inorganic solid electrolyte to obtain a mixture; placing a dispersant, a liquid pore directing agent and a solvent in the mixture for static treatment; Stirring and mixing the mixture after the static treatment to obtain the composite solid electrolyte; The composite solid electrolyte is used to perform pore filling treatment on a non-woven porous substrate; The non-woven fabric porous substrate after the pore filling treatment is dried to obtain a composite separator.

9. The method for preparing a composite diaphragm according to claim 1, characterized in that: The temperature for drying the nonwoven fabric porous substrate after the pore filling treatment is 60°C to 130°C.

10. A semi-solid battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and a composite separator according to any one of claims 1 to 8, wherein the composite separator is sandwiched between the positive electrode sheet and the negative electrode sheet.

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