A coated separator with lithium dendrite in-situ elimination function and a preparation method and application thereof
By constructing a nanoscale or submicron-scale active coating on the lithium-ion battery separator, lithium dendrites are actively eliminated, solving the thermal safety and lithium dendrite problems of lithium-ion batteries and improving the safety and cycle stability of high-energy-density batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU CHENGXING PHOSPH CHEMICALS CO LTD
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-05
AI Technical Summary
Existing lithium-ion battery separators suffer from poor thermal safety and an inability to suppress lithium dendrites, leading to internal short circuits and safety hazards in the battery.
A coating of chemically active nanoscale or submicron-scale materials is used to react with lithium dendrites to generate stable lithium compounds, thereby actively eliminating the growth path of lithium dendrites and forming a dense protective layer.
It significantly improves the safety and cycle life of lithium metal batteries, avoids the risk of internal short circuits caused by lithium dendrite penetration, and does not consume active lithium or increase additional impedance during normal charging and discharging.
Smart Images
Figure CN122158871A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium battery separator technology, specifically relating to a coated separator with in-situ lithium dendrite elimination function, its preparation method, and its application. Background Technology
[0002] Currently, commercial lithium-ion batteries mainly use polyolefin (such as PP / PE) separators, which have advantages such as low cost, good mechanical properties, and acceptable electrochemical stability. However, as batteries develop towards high energy density, high safety and long life, traditional separators have exposed the following fatal weaknesses: (1) Poor thermal safety: Polyolefin materials have a low melting point (~160℃), and will shrink or even melt severely at high temperatures, leading to large-area short circuits inside the battery and causing thermal runaway, which is one of the main reasons for battery fires and explosions; (2) Inability to suppress lithium dendrites: For the next generation of high energy density lithium metal batteries, lithium dendrites will grow on the surface of the negative electrode during cycling. Sharp lithium dendrites will pierce the soft polyolefin separator, causing internal short circuits and serious safety problems.
[0003] Currently, to address the safety issues caused by lithium dendrite growth in lithium-ion batteries, researchers generally employ the method of constructing inorganic coatings on the membrane surface. For example, patent CN113067098A uses a vacuum adsorption roller to coat the membrane with dense inorganic particles, primarily relying on increasing the membrane's mechanical strength to physically block dendrite penetration; patent CN113540688A uses LATP (lithium aluminum titanium phosphate) and inorganic fillers such as LiAl and LDH (lithium aluminum layered double hydroxide) to form a coating, focusing on improving the membrane's high-temperature resistance to delay thermal runaway; patents CN117458082A and CN117254205A modify solid electrolyte materials such as LATP to optimize the electrochemical performance of composite membranes; other technologies, such as CN117254205A and CN114709566A, use inert inorganic materials such as alumina and boehmite to prepare ultrathin coatings. The common feature of these existing technologies is that they essentially rely on the rigid structure, thermodynamic stability, or limited improvement in ionic conductivity of inorganic coatings, achieving only limited optimization of the mechanical strength, thermal stability, or electrochemical performance of the separator. However, these passive physical barrier layers are usually of limited thickness. When lithium deposition is uneven and lithium dendrites continue to grow and accumulate to a certain size, their sharp tips may still penetrate the coating and the separator substrate, leading to an internal short circuit in the battery and causing serious safety hazards. In other words, traditional technologies focus on physically blocking lithium dendrite penetration by improving the mechanical strength of the separator or adding ceramic coatings, which is a "blocking" strategy and cannot fundamentally eliminate the risk of short circuits. Summary of the Invention
[0004] The purpose of this invention is to provide a coating separator with in-situ lithium dendrite elimination function. By actively eliminating the growth path of metallic lithium through chemical means, the traditional physical barrier is transformed into in-situ chemical elimination, thereby fundamentally suppressing the risk of lithium dendrite penetration and significantly improving the intrinsic safety and cycle life of lithium metal batteries.
[0005] The technical solution adopted by this invention to solve the above problems is as follows: a coated separator with in-situ lithium dendrite elimination function, comprising a base film and an active coating coated on at least one surface of the base film, wherein the active coating comprises a binder, a dispersant, a solvent, and a nanoscale or submicron-sized material that can react with lithium, wherein the nanoscale or submicron-sized material is a mixed electron-ion conductor material or an ion conductor material. The particle size range of the nanoscale or submicron-sized material is 50 nm to 1 μm.
[0006] Preferably, the electron-ion mixed conductor material includes at least one of metal oxides, metal nitrides, metal fluorides, and solid electrolytes whose contained metal ions can undergo a reduction reaction with lithium metal, and the ion-generating conductor material includes at least one of sulfide electrolytes or ammonium salts that do not contain metal ions.
[0007] More preferably, the metal oxide is zinc oxide or tin oxide; the metal nitride is copper nitride or magnesium nitride; the metal fluoride is magnesium fluoride or copper fluoride; and the solid electrolyte is LATP, LAGP, LGPS, Li3InCl6 or Li3YCl6.
[0008] More preferably, the sulfide electrolyte is Li6PS5X (X = Cl, Br, I) or Li7P3S. 11 Or Li2S-P2S5; the ammonium salt includes NH4HF2 or NH4F.
[0009] Preferably, the binder is one or more of polyethylene oxide (PEO), polyvinylidene chloride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid, and their derivatives; the dispersant is one or more of silane coupling agents, anionic surfactants, and cationic surfactants; and the solvent is water or an organic solvent.
[0010] Preferably, the base membrane is one or more of a polyolefin microporous membrane, a nonwoven membrane, or a cellulose-based membrane.
[0011] More preferably, the polyolefin microporous membrane is a PE, PP, or PE / PP composite membrane.
[0012] Another object of the present invention is to provide a method for preparing a coated separator with in-situ lithium dendrite elimination function, comprising the following steps: S1: Preparation of active coating slurry Nanoscale or submicron-scale materials that can react with lithium, binders, and dispersants are weighed in a certain mass ratio, added together to the solvent, and dispersed evenly until a stable slurry with uniform viscosity and no obvious particle agglomeration is formed. S2: Coating slurry application The active coating slurry prepared in step S1 is continuously and uniformly coated onto at least one surface of the substrate membrane using a coating device to obtain a wet film. S3: Drying and Post-treatment The coated wet film is dried to remove the solvent in the slurry, forming an active coating that is firmly attached to the surface of the separator. The dried coated separator is then rolled, slit, and wound to obtain a coated separator with in-situ lithium dendrite elimination function.
[0013] Preferably, the wet film coating thickness in step S2 is 1-100 micrometers, and the coating equipment in step S2 is a linear coater, a slot coater, or a microgravure coater.
[0014] More preferably, the thickness of the wet film coating in step S2 is 10-20 micrometers.
[0015] Another object of the present invention is to provide a lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and the above-mentioned coated separator having the function of in-situ elimination of lithium dendrites.
[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) The coating membrane of the present invention has a chemically active functional coating on its surface, which transforms the membrane from a physical barrier into a "chemical cleaner". When lithium dendrites grow and come into contact with the coating, the coating acts as a sacrificial layer and actively reacts irreversibly with the metallic lithium at the dendrite tip, converting it into a stable lithium compound, thus "eliminating the danger source in situ" before a short circuit occurs.
[0017] (2) By transforming “physical barrier” into “chemical elimination”, this invention fundamentally suppresses the risk of internal short circuit caused by lithium dendrites penetrating the separator. The stable lithium compound generated by the reaction not only eliminates dendrites but also fills the pores of the separator, forming a denser protective layer, thereby significantly improving the cycle stability and intrinsic safety of high-energy-density batteries (such as lithium metal batteries and lithium-sulfur batteries).
[0018] (3) The active coating material of the present invention only triggers the reaction when lithium dendrites grow abnormally and come into physical contact, and remains electrochemically inert within the normal charge and discharge voltage window of the battery. This "non-contact non-reaction" characteristic ensures that the coating will not consume active lithium or increase additional impedance during the normal battery cycle, thus achieving a balance between safety protection and electrochemical performance.
[0019] (4) The preparation method of the coating membrane of the present invention is based on the existing mature coating technology, the raw materials are widely available, the cost is controllable, and it is easy to promote and apply it quickly on the existing battery production line, which has extremely high industrialization value. Attached Figure Description
[0020] Figure 1 The image shows a SEM image of LATP@CA prepared in Example 1.
[0021] Figure 2 The image shows a SEM image of Al2O3@CA prepared in Comparative Example 1.
[0022] Figure 3 SEM image of LATP@CA prepared in Comparative Example 3.
[0023] Figure 4 The XRD patterns are of LATP@CA prepared in Examples 1-4.
[0024] Figure 5 The XRD pattern of Al2O3@CA prepared in Comparative Example 1.
[0025] Figure 6 The graphs show the physical properties of the composite membranes prepared in Comparative Example 1 and Examples 1-4. (a) is a displacement-force curve, and (b) is a stress-strain curve.
[0026] Figure 7 The critical current density (CCD) test results of the composite separators prepared in Example 1 and Comparative Example 1 for use in Li||Li symmetric cells are shown.
[0027] Figure 8 The graph shows the cycle performance of Example 1 and Comparative Example 1 in a Li||LFP full cell (0.5C).
[0028] Figure 9 The graph shows the cycle performance of Comparative Example 2 and Examples 5-6 in Li||NCM622 full cells (1C). Detailed Implementation
[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1
[0030] A method for preparing a coated separator with in-situ lithium dendrite elimination function includes the following steps: Preparation of active coating slurry: A 1% PEO aqueous solution was prepared in advance as a binder. Submicron-sized LATP was sieved to obtain submicron-sized LATP powder with d50=300nm. LATP (d50=300nm), 1% PEO aqueous solution, deionized water, and KH550 were added to a sealed container equipped with a stirring device in a mass ratio of 1:1:1:0.25. The mixture was first initially mixed at a low speed (300rpm) for 5 minutes, and then the speed was increased to 2000rpm for high-speed shear dispersion for 60 minutes. The resulting slurry was then transferred to an ultrasonic cleaner and ultrasonically treated at 500W power for 30 minutes under ice-water bath conditions to completely break up the soft agglomerates between the powders and obtain a stable slurry with uniform viscosity and no obvious particle agglomeration or bubbles.
[0031] Coating slurry application: The above slurry was applied to the cellulose acetate (CA) membrane using a linear coater (10 μm) to obtain a wet membrane (LATP@CA).
[0032] Drying and post-treatment: The wet diaphragm is placed in a vacuum oven at 60°C for 12 hours to remove the solvent in the slurry and form an active functional coating that is firmly attached to the surface of the diaphragm. The dried coated diaphragm can be further rolled at 5 MPa by a roller press to enhance the density of the coating and its adhesion to the substrate. Finally, after slitting and winding, the coated diaphragm with the lithium dendrite in-situ elimination function is obtained.
[0033] SEM image of LATP@CA prepared in Example 1 is shown below. Figure 1 As shown, the surface and cross-section of the prepared composite membrane were characterized by SEM and EDS. EDS showed extremely weak Ti element signals, indicating that LATP did not permeate to the back side. Example 2
[0034] The material preparation method in this embodiment is basically the same as that in Example 1, except that: Preparation of composite membrane: The slurry was coated onto the cellulose acetate membrane (CA) using a linear coater (20 μm) to obtain a wet membrane (LATP@CA). Example 3
[0035] The material preparation method in this embodiment is basically the same as that in Example 1, except that: Preparation of composite membrane: The slurry was coated onto the cellulose acetate membrane (CA) using a linear coater (50 μm) to obtain a wet membrane (LATP@CA). Example 4
[0036] The material preparation method in this embodiment is basically the same as that in Example 1, except that: Preparation of composite membrane: The slurry was coated onto the cellulose acetate membrane (CA) using a linear coater (100 μm) to obtain a wet membrane (LATP@CA).
[0037] The XRD patterns of LATP@CA prepared in Examples 1-4 are shown below. Figure 4 As shown, its main diffraction peak is CA, and impurities (AlPO4, etc.) in LATP are easily soluble in the aqueous phase, thus producing impurity peaks. Example 5
[0038] A method for preparing a coated separator with in-situ lithium dendrite elimination function includes the following steps: Preparation of active coating slurry: PVDF was used as a binder and N-methylpyrrolidone (NMP) was used as a solvent. Submicron-sized LATP was sieved to obtain submicron-sized LATP powder with d50=300nm. LATP (d50=300nm), PVDF, NMP, and KH550 were added to a sealed container equipped with a stirring device in a mass ratio of 1:1:1:0.25. First, the mixture was initially mixed at a low speed (300 rpm) for 5 minutes, and then the speed was increased to 2000 rpm for high-speed shear dispersion for 60 minutes. The resulting slurry was then transferred to an ultrasonic cleaner and ultrasonically treated at 500 W power for 30 minutes under ice-water bath conditions to completely break up the soft agglomerates between the powders and obtain a stable slurry with moderate solid content, uniform viscosity, and no obvious particle agglomeration or bubbles.
[0039] Coating slurry application: The slurry is applied to the polypropylene (PP) diaphragm using a linear coater (10 μm) to obtain a wet diaphragm (LATP@PP).
[0040] Drying and post-treatment: The wet diaphragm is placed in a vacuum oven at 60°C for 12 hours to remove the solvent in the slurry and form an active functional coating that is firmly attached to the surface of the diaphragm. The dried coated diaphragm can be further rolled at 5 MPa by a roller press to enhance the density of the coating and its adhesion to the substrate. Finally, after slitting and winding, the coated diaphragm with the lithium dendrite in-situ elimination function is obtained. Example 6
[0041] A method for preparing a coated separator with in-situ lithium dendrite elimination function includes the following steps: Preparation of active coating slurry: A mixture of NMP and isopropanol in a mass ratio of 1:1 was prepared in advance. Submicron-sized LATP was sieved to obtain submicron-sized LATP powder with d50=300nm. LATP (d50=300nm), the NMP and isopropanol mixture, PVDF, and KH550 were added to a sealed container equipped with a stirring device in a mass ratio of 1:2:0.5:0.25. First, the mixture was initially mixed at a low speed (300 rpm) for 5 minutes, and then the speed was increased to 2000 rpm for high-speed shear dispersion for 60 minutes. The resulting slurry was then transferred to an ultrasonic cleaner and ultrasonically treated at 500 W power for 30 minutes under ice-water bath conditions to completely break up the soft agglomerates between the powders and obtain a stable slurry with moderate solid content, uniform viscosity, and no obvious particle agglomeration or bubbles.
[0042] Coating slurry application: The slurry is applied to the polypropylene diaphragm (PP) using a linear coater (15 μm) to obtain a wet diaphragm (LATP@PP).
[0043] Drying and post-treatment: The wet diaphragm is placed in a vacuum oven at 60°C for drying to remove the solvent in the slurry and form an active functional coating that is firmly attached to the surface of the diaphragm. The dried coated diaphragm can be further lightly rolled by a roller press to enhance the density of the coating and its adhesion to the substrate. Finally, after slitting and winding, the coated diaphragm with the lithium dendrite in-situ elimination function is obtained. Example 7
[0044] The only difference from Example 5 is: Coating slurry application: The slurry is applied to the polypropylene (PP) diaphragm using a linear coater (25 μm) to obtain a wet diaphragm (LATP@PP).
[0045] Comparative Example 1 The material preparation method in this comparative example is basically the same as that in Example 1, except that: The coating used is Al2O3, which does not react with metallic lithium. Al2O3 is coated onto a CA membrane to obtain an Al2O3@CA composite membrane.
[0046] SEM image of Al2O3@CA prepared in Comparative Example 1 is shown below. Figure 2 As shown, the sample surface exhibits a relatively uniform particle distribution, with relatively small and uniform particle size. The overall surface roughness is relatively consistent, and there are no obvious large-sized agglomerates or special structures protruding from the surface, showing a relatively homogeneous microstructure.
[0047] The XRD pattern of Al2O3@CA prepared in Comparative Example 1 is shown below. Figure 5 As shown in the figure, the main peak and Figure 4 In (Examples 1-4), the main peak of the XRD is consistent, which is the diffraction peak of CA, and the other diffraction peak is the diffraction peak of Al2O3.
[0048] The physical properties of the composite membranes prepared in Comparative Example 1 and Examples 1-4 are shown in the figure. Figure 6 As shown in the displacement-force curves, Comparative Example 1 fractured at a displacement of approximately 10 mm, with a peak stress of approximately 10 MPa. For the CA@LATP composite film, as the LATP thickness increased (from 10 μm to 100 μm), the fracture displacement significantly shortened (from ~30 mm to ~10 mm), indicating a decrease in the material's ductility and an increase in its brittleness. The stress-strain curves show that the peak stress first increased and then decreased, with the highest peak at 10 μm (Example 1), the lowest at 100 μm (Example 4), followed by 20 μm (Example 2), and the lowest strength observed in the 50 μm (Example 3) and 100 μm (Example 4) samples. This indicates that 10 μm LATP has the best reinforcing effect on CA. It is evident that LATP has a dual effect on the mechanical properties of CA. At 10 μm, LATP bonds well with the CA matrix, playing a reinforcing role and optimizing the material's strength and ductility. However, as the thickness of LATP continues to increase, the agglomeration of inorganic particles and stress concentration lead to increased brittleness and decreased strength and ductility.
[0049] The critical current density (CCD) test results of the composite separator prepared in Example 1 and Comparative Example 1 for use in a Li||Li symmetric battery are shown in the figure below. Figure 7 As shown, the CCD of Comparative Example 1 has an A / cm² value of 1.60 mA / cm². 2 The CCD in Example 1 achieved 2.0 mA / cm². 2 This indicates that the LATP-based composite membrane has a certain inhibitory effect on the growth of Li dendrites.
[0050] The cycling performance graphs of Example 1 and Comparative Example 1 for Li||LFP full cells (0.5C) are shown in the figure. Figure 8 As shown, Example 1 exhibits an initial discharge capacity of approximately 150 mAh g at 0.5C. -1After 100 cycles, the capacity retention rate was approximately 90%, with only slight polarization growth, demonstrating excellent long-cycle stability. Comparative Example 1, activated at 0.1C and tested at 0.5C, showed a slightly higher initial discharge capacity, but significant capacity decay occurred after only 30 cycles, with a significant voltage plateau shift and greatly intensified polarization. The results indicate that the technical solution of Example 1 of this invention can effectively suppress capacity decay and interface polarization during cycling, significantly improving the cycle life and rate performance of the battery, and exhibiting superior electrochemical stability compared to Comparative Example 1. Furthermore, the assembly of the Li||LFP full cell specifically involved dissolving lithium hexafluorophosphate (LiPF6) and lithium bis(trifluorosulfonyl)imide (LiTFSI) in dimethyl ethylene glycol (DME) at concentrations of 0.5 mol / L. -1 and 1.0 mol L -1 The resulting salt solution was mixed with 1,3-dioxolane (DOL) at a volume ratio of 1:4 to obtain the final electrolyte. The electrolyte was then dropwise added onto a composite membrane, and a coin cell was assembled using lithium metal as the negative electrode and lithium iron phosphate (LiFePO4) as the positive electrode. The assembled battery was allowed to stand for 10 hours to stabilize before electrochemical testing.
[0051] Comparative Example 2 The material preparation method in this comparative example is basically the same as that in Example 1, except that: The coating used is Al2O3, which does not react with metallic lithium. Al2O3 is coated onto a PP membrane to obtain an Al2O3@PP composite membrane.
[0052] The cycle performance graphs of Comparative Example 2 and Examples 5-6 for Li||NCM622 full cells (1C) are shown in the figure. Figure 9 As shown, Example 5 achieved an ultra-long cycle life of 400 cycles, and Example 6 achieved a stable cycle life of 300 cycles. The charge-discharge curves showed good consistency, and the interface stability was outstanding, demonstrating excellent long cycle life. Comparative Example 2 showed lithium dendrite growth only in the first cycle, which led to fluctuations in the voltage curve. The surface inactive Al2O3 could not significantly inhibit dendrite growth. The assembly of the Li||NCM622 full cell adopted the following steps: 1M LiPF6 was dissolved in DMC / EC / EMC (volume ratio 1:1:1) and 1% VC was added as liquid electrolyte. Using NCM622 positive electrode, lithium metal negative electrode and the prepared composite separator, coin cell full cells were assembled in a glove box. After assembly, the cells were left to stand for 6 hours to allow the electrolyte to fully wet and the interface to stabilize before electrochemical performance testing was performed.
[0053] Comparative Example 3 The material preparation method of this comparative example is basically the same as that of Example 1, except that the LATP used is micron-sized and the D50 is 2.2 μm.
[0054] SEM image of LATP@CA prepared in Comparative Example 3 is shown below. Figure 3 As shown, by Figure 3 It can be seen that when large-sized micron-sized particles are used as active materials, the resulting coating layer has a rough surface and a loose structure, and cannot form a dense active layer, indicating that large particles are not conducive to building a uniform and complete membrane coating.
[0055] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.
Claims
1. A coated separator with in-situ lithium dendrite elimination function, characterized in that: It includes a base film and an active coating coated on at least one surface of the base film, the active coating including a binder, a dispersant, a solvent, and a nanoscale or submicron-scale material that can react with lithium, the nanoscale or submicron-scale material being a mixed conductor material that generates electrons and ions or a conductor material that generates ions.
2. The coated separator with in-situ lithium dendrite elimination function according to claim 1, characterized in that: The electron-ion generating mixed conductor material includes at least one of metal oxides, metal nitrides, metal fluorides, and solid electrolytes whose contained metal ions can undergo a reduction reaction with lithium metal. The ion generating conductor material includes at least one of sulfide electrolytes or ammonium salts that do not contain metal ions.
3. The coated separator with in-situ lithium dendrite elimination function according to claim 2, characterized in that: The metal oxide is zinc oxide or tin oxide; the metal nitride is copper nitride or magnesium nitride; the metal fluoride is magnesium fluoride or copper fluoride; the solid electrolyte is LATP, LAGP, LGPS, Li3InCl6 or Li3YCl6.
4. The coated separator with in-situ lithium dendrite elimination function according to claim 2, characterized in that: The sulfide electrolyte is Li7P3S. 11 The ammonium salt is either Li2S-P2S5 or Li6PS5X, where X = Cl, Br, I; or NH4HF2 or NH4F.
5. The coated separator with in-situ lithium dendrite elimination function according to claim 1, characterized in that: The binder is one or more of polyethylene oxide (PEO), polyvinylidene chloride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid, and their derivatives; the dispersant is one or more of silane coupling agents, anionic surfactants, and cationic surfactants; and the solvent is water or an organic solvent.
6. The coated separator with in-situ lithium dendrite elimination function according to claim 1, characterized in that: The base membrane is one or more of the following: polyolefin microporous membrane, nonwoven membrane, or cellulose-based membrane.
7. A method for preparing a coated separator with in-situ lithium dendrite elimination function according to any one of claims 1-6, characterized in that: Includes the following steps: S1: Preparation of active coating slurry Nanoscale or submicron-scale materials that can react with lithium, binders, and dispersants are weighed in a certain mass ratio, added together to the solvent, and dispersed evenly until a stable slurry with uniform viscosity and no obvious particle agglomeration is formed. S2: Coating slurry application The active coating slurry prepared in step S1 is continuously and uniformly coated onto at least one surface of the substrate membrane using a coating device to obtain a wet film. S3: Drying and Post-treatment The coated wet film is dried to remove the solvent in the slurry, forming an active coating that is firmly attached to the surface of the separator. The dried coated separator is then rolled, slit, and wound to obtain a coated separator with in-situ lithium dendrite elimination function.
8. The method for preparing the coated separator with in-situ lithium dendrite elimination function according to claim 7, characterized in that: The wet film coating thickness in step S2 is 1-100 micrometers, and the coating equipment in step S2 is a linear coater, a slot coater, or a microgravure coater.
9. A lithium-ion battery, characterized in that: It includes a positive electrode, a negative electrode, an electrolyte, and a coated separator with in-situ lithium dendrite elimination function according to any one of claims 1-6.