A modified coating, a preparation method, an electrode with modified coating, and a battery.

Abstract

This application belongs to the field of solid-state battery technology, specifically relating to a modified coating, a preparation method, a coated electrode, and a battery. The modified coating includes a polymer matrix and a fast-ion conductor filler; the fast-ion conductor filler is an oxyfluorine electrolyte, with a mass fraction accounting for 60-80 wt% of the total mass of the modified coating; the polymer matrix is ​​at least one of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, and vinylidene fluoride hexafluoropropylene, with a mass fraction accounting for 20-40 wt% of the total mass of the modified coating. The modified coating of this application has the advantages of both good air stability and high room temperature ionic conductivity, and is used to modify the positive and / or negative electrodes of batteries, and applied to ampere-hour (Ah) level solid-state batteries to simultaneously improve battery safety performance, cycle life, and energy density.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a modified coating, a preparation method, a coated electrode, and a battery. Background Technology

[0002] Compared to traditional liquid lithium-ion batteries, solid-state batteries are a popular research subject for the next generation of new batteries due to their high energy density and high safety.

[0003] To meet the application requirements of long-range and high-safety applications, ternary cathode materials with high energy density are considered promising. However, due to their poor thermal stability under extreme conditions (such as high temperature and extrusion), they are prone to thermal runaway, posing safety hazards. In recent years, coating technology has received widespread attention as one of the strategies to improve battery safety performance. Various coating materials have been applied to improve battery safety performance, including Al2O3, NASICON-type electrolytes, garnet-type electrolytes, and halide electrolytes. However, these materials often struggle to simultaneously achieve good air stability and high ionic conductivity.

[0004] Therefore, the issues of improving battery safety and long-range capability urgently need to be addressed. Summary of the Invention

[0005] This application aims to overcome the shortcomings of the prior art and provide a modified coating, a preparation method, a coated electrode and a battery. The modified coating has the advantages of both good air stability and high room temperature ionic conductivity. It is used to modify the positive electrode and / or negative electrode of the battery and applied to ampere-hour (Ah) level solid-state batteries to simultaneously improve the battery's safety performance, cycle life and energy density.

[0006] To achieve the above objectives, a first aspect of this application provides a modified coating comprising: a polymer matrix and a fast ion conductor filler; wherein the fast ion conductor filler is an oxyfluorine electrolyte, and its mass fraction accounts for 60-80 wt% of the total mass of the modified coating; wherein the polymer matrix is ​​at least one of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, and vinylidene fluoride hexafluoropropylene, and its mass fraction accounts for 20-40 wt% of the total mass of the modified coating.

[0007] A further technical solution is that the chemical formula of the oxygen-fluorine electrolyte is: Liγ1Xγ2M2O6F, where X=La / Al, La; M=Nb,Ta, 0≤γ1≤0.8, 0<γ2<4.

[0008] A further technical solution is that the oxygen-fluorine electrolyte has a room temperature ionic conductivity >1.0 mS / cm and a particle size of 0.1~1.0 μm.

[0009] A second aspect of this application provides a method for preparing the modified coating, comprising the following steps:

[0010] The oxyfluorine electrolyte and the polymer matrix are dissolved in an organic solvent and thoroughly stirred to form a slurry;

[0011] The slurry is uniformly coated onto the surface of the substrate using pulse spraying technology; subsequently, it is vacuum dried to obtain the modified coating.

[0012] A further technical solution is that the pulse spraying technology and drying steps are both carried out in an environment with a dew point below -40°C.

[0013] A third aspect of this application provides a coated electrode, comprising a current collector and an active material coated thereon, wherein the surface of the active material is coated with the modified coating or a modified coating prepared by the method described above.

[0014] A further technical solution is that the thickness of the modified coating is 1.25~4μm.

[0015] A further technical solution is that the electrode is a positive electrode, the active material is a positive electrode active material, and the chemical formula of the positive electrode active material is: LiNi x Co y Mn 1-x-y O2.

[0016] A further technical solution is that the electrode is a negative electrode, the active material is a silicon-carbon material, and the mass content of Si in the silicon-carbon material does not exceed 20 wt%.

[0017] A fourth aspect of this application provides a battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte; wherein the positive electrode is the coated electrode, and / or the negative electrode is the coated electrode.

[0018] Compared with the prior art, this application has the following beneficial effects:

[0019] This application provides a modification coating, which is composed of a polymer matrix and a fast ion conductor filler;

[0020] The fast ion conductor filler is an oxyfluorine electrolyte. Compared with NASICON-type solid electrolytes, garnet-type solid electrolytes, and halide-based solid electrolytes, the oxyfluorine electrolyte used in this application has both excellent air stability and high room temperature ionic conductivity (1.24 mS / cm), solving the problem that traditional coating materials cannot balance stability and conductivity.

[0021] This application also provides a method for preparing a modified coating, which uses high-precision pulse spraying technology to overcome the technical bottleneck of traditional coating processes in preparing ultra-thin, uniform, and dense coatings, and achieves precise control of coating thickness (1.25-4μm), which is beneficial to improving the energy density of the battery.

[0022] This application also provides a coated positive electrode sheet, comprising a positive current collector and a positive active material disposed on the surface of the positive current collector. A modified coating is applied to the surface of the positive active material. This modified coating facilitates the in-situ formation of a passivation CEI layer (such as AlF3 or LiF) at the interface between the positive electrode sheet and the electrolyte during battery cycling, helping to mitigate the damage of HF to the positive electrode structure and delaying thermal failure caused by the release of O2 due to the destruction of the transition metal-oxygen structure. CEI is a multilayered, heterogeneous, and dynamically evolving passivation layer, mainly composed of the products of oxidative decomposition of the electrolyte at high positive electrode potentials, with fluorides as the main component. The higher the voltage, the more intense the oxidative decomposition, the thicker the CEI layer, and the higher the proportion of inorganic components may be. This modified coating contains Al and F ions, thus facilitating the formation of a CEI protective layer during battery cycling.

[0023] This application also provides a coated negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material (silicon-carbon material) disposed on the surface of the negative electrode current collector. A modified coating is coated on the surface of the silicon-carbon material. Because the modified coating has stability for the SiC negative electrode, it can also act as an artificial solid electrolyte interface (SEI) film, effectively alleviating the problem of volume expansion of the SiC negative electrode during cycling, and improving the structural stability and cycle life of the negative electrode.

[0024] This application also provides a battery in which the modification coating of this application is applied to an Ah-level soft-pack solid-state battery, which can significantly improve the battery's first efficiency and long cycle capacity retention (e.g., it can still maintain high capacity after 400 cycles), and has passed a rigorous nail penetration safety test, achieving a synergistic improvement in high safety and long cycle life. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the positive electrode sheet after modification with the coating in this embodiment. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0027] For the sake of brevity, this document only discloses a few specific numerical ranges for a given parameter. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range; similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit, combined with any other point or single value, or with other lower or upper limits, to form an unspecified range. It should be understood that this disclosure is not limited to the specific methods, schemes, and reagents described herein, and is itself subject to variation. The terminology used herein is for the purpose of describing specific embodiments or aspects only and is not intended to limit the scope of this disclosure.

[0028] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise expressly stated, all reagents used in this application are commonly used reagents for chemical analysis or experiments and are derived from conventional commercial suppliers in the art.

[0029] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0030] This embodiment provides a modified coating, comprising: a polymer matrix and a fast ion conductor filler; the fast ion conductor filler is an oxyfluorine electrolyte, and its mass fraction accounts for 60-80 wt% of the total mass of the modified coating. For example, it can be 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, etc. The polymer matrix is ​​at least one of polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, and vinylidene fluoride hexafluoropropylene, and its mass fraction accounts for 20-40 wt% of the total mass of the modified coating. For example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, etc.

[0031] In this embodiment, the modified coating consists of a polymer matrix and a fast ion conductor filler. The fast ion conductor filler is an oxyfluorine electrolyte. Compared with NASICON-type solid electrolytes, garnet-type solid electrolytes, and halide-based solid electrolytes, oxyfluorine electrolytes possess both excellent air stability and high room temperature ionic conductivity (1.24 mS / cm). High room temperature conductivity is beneficial for the rapid transport of lithium ions, a characteristic with broad application prospects. Furthermore, when both the polymer matrix and the fast ion conductor filler are present, three ion transport mechanisms can be provided: 1. Ceramic phase conduction; 2. Polymer phase conduction; 3. A synergistic mode of ion transport enhanced by the ceramic / polymer interface. A higher content of oxyfluorine electrolyte can increase the withstand voltage, mechanical strength, and electrochemical stability; conversely, a lower content will weaken these properties. Therefore, a medium-to-high content of 60-80 wt% oxyfluorine electrolyte is selected to ensure high ion transport of the composite electrolyte and improve cycle performance. The addition of 20-40 wt% polymer matrix can play the following roles: 1) increase ion transport pathways, 2) introduce multiple F groups, and utilize the strong ionic electronegativity of F to further enhance ion transport speed and promote the dissociation ability of lithium salt.

[0032] When the above-mentioned modified coating is applied to solid-state batteries, it can promote the dissociation of lithium salts in the electrolyte and improve the battery's cycle performance. In the electrolyte, Li... + With anions (such as PF6) - TFSI - The atoms are tightly bound together by Coulomb forces, and dissociation requires energy to overcome this interaction. Many F-containing coated materials (such as AlF3 and lithium fluoride salts) have strong Lewis acidic sites on their surfaces. For example, Al... 3+ Fluorine (F) atoms, whether ions or partially electron-deficient, have a strong ability to accept electron pairs. These strongly Lewis acidic sites strongly adsorb or coordinate anions (such as PF6) in the electrolyte. - Because the surface of the modified coating has a much stronger attraction for F ions than for Li. + The attraction to anions causes them to "anchor" at the solid-liquid interface, thus forcibly elongating the Li... + With FSI - PF6 - The distance between them significantly weakens the Coulomb force between them, making Li + It is more likely to dissociate into free (or bound to solvent molecules) lithium ions. Furthermore, LiF is an ionic compound, but its surface-terminated... Ions carry a high negative charge and can interact with FSI through electrostatic interactions. - / PF6 - The anions repel each other, and this repulsion "pushes" the anions away, indirectly helping Li... +Dissociation. Meanwhile, LiF is an excellent electronic insulator but allows Li to dissociate. + Through, it can be used for Li + The transmission provides a low-impedance path.

[0033] In this embodiment, it should be noted that the chemical formula of the oxyfluorine electrolyte is: Li γ1 X γ2 M2O6F, where X=La / Al, La; M=Nb, Ta, 0≤γ1≤0.8, 0<γ2<4.

[0034] It should be noted that the room temperature ionic conductivity of oxygen-fluorine electrolytes is >1.0 mS / cm, and the amount of Al involved can be controlled by controlling different ranges of γ1. The introduction of Al plays a stabilizing role at the positive electrode interface by forming AlF3 CEI during battery cycling.

[0035] In this embodiment, it should be noted that the particle size of the oxyfluorine electrolyte is 0.1~1.0 μm, for example, it can be 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.7 μm, 0.85 μm, 0.9 μm, 1 μm, etc. It should be noted that controlling the appropriate particle size of the oxyfluorine electrolyte is mainly to regulate the porosity of the modified coating. If the particle size of the oxyfluorine electrolyte is too large, it easily leads to large porosity, causing direct contact between the electrolyte and the electrode, thus negating the coating's function. If the particle size of the oxyfluorine electrolyte is too small, it easily leads to agglomeration and uneven coverage.

[0036] This embodiment also provides a method for preparing a modified coating, including the following steps:

[0037] S1. Dissolve the oxyfluorine electrolyte and polymer matrix in an organic solvent and mix thoroughly to form a slurry;

[0038] S2. The slurry is uniformly coated onto the surface of the substrate using pulse spraying technology; then vacuum dried to obtain a modified coating.

[0039] In the preparation process, the oxyfluorine electrolyte and polymer matrix are dissolved in an organic solvent such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), or tetrahydrofuran (THF), and thoroughly stirred to form a slurry. NMP is preferred because it is the optimal choice in this case, balancing solubility, dispersibility, evaporation rate, and process controllability. It is particularly suitable for thin-film spraying processes of PVDF-based slurries, enabling the formation of a uniform and dense functional modified coating. When applying the modified coating to the positive electrode of a solid-state battery, at the physical level, compared with traditional coating processes, this application uses pulse spraying technology to overcome the process difficulties in preparing ultra-thin coatings and produces a modified coating with high density and good uniformity. This modified coating has excellent properties such as high room temperature ionic conductivity and high insulation. At the same time, this modified coating avoids adverse side reactions at the interface caused by direct series connection between the high-nickel positive electrode and the electrolyte, thus stabilizing the positive electrode interface structure. In addition, the modified coating isolates the series connection between the positive and negative electrodes, avoiding internal short circuits during nail penetration testing and improving the battery's nail penetration safety performance.

[0040] At the chemical level, due to the inherent high electronic insulation and high room temperature ionic conductivity of the modified coating, the porosity of the modified coating can be uniformly and densely controlled by pulse spraying technology, and the lithium ion transport pathway can be precisely constructed (1. ceramic phase conduction; 2. polymer phase conduction; 3. ceramic / polymer interface enhanced conduction). Furthermore, by adjusting the thickness of the modified coating, the dissolution of transition metal ions on the positive electrode side can be mitigated.

[0041] The modified coating serves two purposes: 1) Physical isolation: By coating the surface of the positive electrode active material with a dense, stable, and ion-conducting ceramic layer, it directly separates the active material from the electrolyte. 2) Chemical capture: It preferentially reacts with HF to generate stable fluorides (such as AlF3), thereby consuming free HF in the electrolyte and preventing it from reaching the surface of the positive electrode active material. Furthermore:

[0042] Suppressing lattice oxygen release: Modified coatings can stabilize surface lattice oxygen and reduce irreversible oxygen release under high voltage. The formation of oxygen vacancies is the starting point for structural degradation and metal ion migration.

[0043] Anchoring surface metal ions: The modified coating and the cathode surface may form a stable interface phase, effectively "fixing" the transition metal ions (especially Ni) on the surface. 3+ / Ni 4+ They are easily reduced and dissolved, preventing them from migrating into the electrolyte.

[0044] Strengthening grain boundaries: The modified coating can cover the boundaries of primary nanocrystals, strengthen the grain boundaries, prevent electrolyte from penetrating and corroding along the grain boundaries, and thus inhibit dissolution starting from the grain boundaries.

[0045] In this embodiment, it should be noted that both the pulse spraying technology and the drying step are performed in an environment with a dew point below -40°C. It should also be noted that for high-nickel NCM materials, the moisture content of the positive electrode typically needs to be controlled below the ppm level; a dew point below -40°C essentially controls moisture content.

[0046] 1) The surface of high-nickel materials inevitably contains residual lithium compounds such as Li2CO3 and LiOH. Moisture will react with them, exacerbating the surface alkalinity and potentially generating a thicker, more impedance-rich Li2CO3 layer.

[0047] 2) Moisture can also react with the electrolyte to form HF, leading to the dissolution of transition metals, including Mn ions. 2+ These ions migrate to the negative electrode, catalyzing the decomposition and reconstruction of the SEI film, continuously consuming electrolyte and active lithium, and accelerating capacity decay. Furthermore, surface corrosion causes nickel-rich materials to transform from a stable layered structure into an electrochemically inert spinel or rock salt phase (such as NiO). These inert layers hinder lithium-ion diffusion and increase interfacial impedance.

[0048] 3) The H of water molecules + Possibly related to Li in the material + Ion exchange occurs, leading to protonation of the surface structure and disruption of lithium-ion transport channels.

[0049] This embodiment also provides a coated electrode, comprising a current collector and an active material coated thereon, wherein the surface of the active material is coated with the aforementioned modified coating or a modified coating prepared by the aforementioned method (e.g., refer to...). Figure 1 (As shown).

[0050] In one example, the thickness of the modification coating is 1.25~4μm, such as 1.25μm, 1.5μm, 1.65μm, 1.75μm, 2.15μm, 2.35μm, 2.65μm, 3.4μm, 3.7μm, 4μm, etc. It should be noted that an excessively thick modification coating may affect the battery's long cycle life because increasing the modification coating increases the interfacial resistance between the electrode, modification coating, and electrolyte with increasing cycle count. A modification coating that is too thin has a poor effect on improving the battery's needle penetration safety performance. In this invention, when the modification coating thickness is less than 1.25μm, the coverage is too low to reflect the beneficial effect of the modification coating on needle penetration performance; when it is greater than 4μm, it leads to increased internal resistance and affects the improvement of the battery's first-time efficiency.

[0051] In one specific implementation, the electrode is a positive electrode, the current collector is a positive electrode current collector, and the active material is a positive electrode active material with the chemical formula: LiNi. x Coy Mn 1-x-y O2, where 0.5≤x≤0.88, 0.05≤y≤0.3, and molar ratios x=0.5, 0.6, 0.78, 0.80, 0.83, 0.88. It should be noted that the purpose of selecting a medium-to-high nickel layered oxide cathode is to pursue high energy density. Furthermore, the modified coating directly prevents the negative interfacial reaction between the electrolyte and the ternary cathode, which has a positive effect on the thermal failure of the cathode active material caused by oxygen release, thereby stabilizing the cathode structure and improving battery safety.

[0052] In another specific embodiment, the electrode is a negative electrode, the current collector is a negative current collector, and the active material is a negative electrode active material, such as silicon carbide material. The mass content of Si in the silicon carbide material does not exceed 20wt%, for example, it can be 5wt%, 10wt%, 15wt%, 18wt%, 20wt%, etc. It's important to note that in silicon-carbon materials, the silicon content is typically limited to 10-20 wt% of the total anode mass. The main reasons are: 1. To utilize the high theoretical capacity of silicon (4200 mAh / g); 2. A low silicon content (≤20%) means that over 80% of the material is a structurally stable carbon matrix with minimal volume change (such as graphite). The carbon matrix acts as a buffer framework, absorbing and dispersing the stress generated by the expansion / contraction of silicon particles, thus preventing the overall electrode structure from pulverizing and collapsing, and mitigating the volume expansion effect; 3. The large volume change of silicon causes repeated rupture and regeneration of the SEI film on its surface, continuously consuming electrolyte and active lithium, leading to rapid capacity decay. Limiting the silicon content reduces the overall scale of this destructive interfacial reaction, contributing to the formation of a relatively more stable SEI film; 4. Carbon materials (especially graphite) possess excellent conductivity and mechanical strength. Sufficient carbon content ensures an effective electron transport pathway within the electrode and "binds" the silicon particles together, maintaining the overall conductive network and structural strength of the electrode.

[0053] This embodiment also provides a battery, including a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte; the positive electrode is an electrode modified with the above-mentioned coating, and / or the negative electrode is an electrode modified with the above-mentioned coating. The electrolyte can be a liquid electrolyte, a gel polymer electrolyte, or a composite solid electrolyte. Preferably, the electrolyte is a solution containing a high concentration of lithium salt, such as a 3 mol / L LiFSI electrolyte. The battery can be a lithium metal battery, a secondary lithium battery, or a lithium-air battery.

[0054] Positive electrode preparation:

[0055] LiNi, the positive electrode active material x Co y Mn 1-x-yO2 (x=0.78, abbreviated as Ni78), conductive carbon black (Super-P), and binder PVDF are mixed in a weight ratio of 98:1:1 in the solvent N-pyrrolidone (NMP). After uniform mixing, the mixture is coated onto an aluminum foil current collector. After drying, cold pressing, slitting, and die-cutting, a positive electrode sheet is obtained with an areal density of 511±2 g / m³. 2 .

[0056] Negative electrode preparation

[0057] A silicon-carbon material containing 15 wt% Si, conductive carbon black (Super-P), carbon nanotubes (CNTs), styrene-butadiene rubber (SBR) binder, and carboxymethyl cellulose (CMC) were mixed in deionized water at a weight ratio of 80:9.5:0.5:9.5:0.5. The mixture was then coated onto both sides of a copper foil current collector. After drying, cold pressing, slitting, and die-cutting, a negative electrode sheet was obtained with an areal density of 185 ± 1 g / m³. 2 .

[0058] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0059] Examples 1-5 below demonstrate the application of different coating formulations and thicknesses on positive electrode sheets; Examples 6-8 demonstrate the application on negative electrode sheets; Examples 9-11 demonstrate the simultaneous application on both positive and negative electrode sheets.

[0060] Example 1

[0061] LXMOF powder with a particle size D50 of 0.3 μm and a mass fraction of 80 wt% was used; PVDF with a mass fraction of 20 wt% was also used. LXMOF and PVDF were dissolved in NMP and thoroughly mixed to form a homogeneous slurry. Using a pulse spraying device, the slurry was uniformly sprayed onto one side of the prepared Ni78 positive electrode sheet. The positive electrode sheet was then placed in an 80°C constant temperature vacuum chamber for 12 hours until completely dry. The other side was then sprayed using the same process. All operations were performed in a dry room (dew point below -40°C). The total coating thickness was approximately 4 μm.

[0062] Example 2

[0063] The LXMOF mass fraction was 75 wt%, PVDF was 25 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 1, and the total thickness of the resulting coating was approximately 3.5 μm.

[0064] Example 3

[0065] The LXMOF mass fraction was 70 wt%, PVDF was 30 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 1, and the total thickness of the resulting coating was approximately 3 μm.

[0066] Example 4

[0067] The LXMOF mass fraction was 65 wt%, PVDF was 35 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 1, and the total thickness of the resulting coating was approximately 2.5 μm.

[0068] Example 5

[0069] The LXMOF mass fraction was 60 wt%, PVDF was 40 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 1, and the total thickness of the resulting coating was approximately 1.25 μm.

[0070] Example 6

[0071] LXMOF powder with a particle size D50 of 0.3 μm and a mass fraction of 80 wt% was used; PVDF with a mass fraction of 20 wt% was also used. LXMOF and PVDF were dissolved in NMP and thoroughly mixed to form a homogeneous slurry. Using a pulse spraying device, the slurry was uniformly sprayed onto one side of the prepared SiC negative electrode sheet. The SiC negative electrode sheet was then placed in an 80°C constant temperature vacuum chamber for 12 hours until completely dry. The other side was then sprayed using the same process. All operations were completed in a dry room (dew point below -40°C). The total coating thickness was approximately 4 μm.

[0072] Example 7

[0073] The LXMOF mass fraction was 70 wt%, PVDF was 30 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 6, and the total thickness of the resulting coating was approximately 3 μm.

[0074] Example 8

[0075] The LXMOF mass fraction was 60 wt%, PVDF was 40 wt%, and D50 was 0.3 μm. The preparation and spraying process were the same as in Example 6, and the total thickness of the resulting coating was approximately 2.5 μm.

[0076] Example 9

[0077] Using the same slurry formulation (LXMOF 80wt%, PVDF 20wt%) and pulse spraying process as in Example 1, coatings were applied to both sides of the Ni78 positive electrode and the SiC negative electrode, respectively.

[0078] Example 10

[0079] Using the same slurry formulation (LXMOF 70wt%, PVDF 30wt%) and pulse spraying process as in Example 3, coatings were applied to both sides of the Ni78 positive electrode and the SiC negative electrode, respectively.

[0080] Example 11

[0081] Using the same slurry formulation (LXMOF 60wt%, PVDF 40wt%) and pulse spraying process as in Example 5, coatings were applied to both sides of the Ni78 positive electrode and the SiC negative electrode, respectively.

[0082] Comparative Example 1: Using the above-mentioned Ni78 positive electrode and SiC negative electrode without any coating modification.

[0083] Comparative Example 2: Using an uncoated Ni78 positive electrode and a SiC negative electrode coated using the process of Example 11.

[0084] Battery assembly and testing

[0085] 1) Battery assembly

[0086] The positive and negative electrode sheets from Examples 1-11 above are stacked with a separator (a separator with boehmite double-sided coating @PP) in a Z-shaped order to obtain a dry stack core. Then, tabs are welded to the stack core and it is sealed in an aluminum-plastic bag. Next, electrolyte is injected (injection coefficient E / C=2.0g / Ah), and the bag is sealed. Finally, after standing, aging, formation, and capacity testing, a 10Ah soft-pack solid-state battery is prepared.

[0087] 2) Battery cycle performance test

[0088] The assembled pouch cells were tested at 25°C. They were charged at a constant current of 0.5C to 4.35V (cutoff voltage), then charged at a constant voltage until the current dropped to 0.05C (cutoff); finally, they were discharged at a constant current of 1C to 2.5V. The initial efficiency and capacity retention after 400 cycles were recorded. The results are shown in Table 1 below.

[0089] The effect of coating thickness on the needle penetration safety performance of lithium ions.

[0090] Battery pretreatment before the needle penetration safety test: Under 25℃ conditions, the assembled soft pack battery is attached to the fixture and discharged at a constant current of 0.33C to 2.5V, and left to stand for 10 minutes; then it is charged at a constant current of 0.33C to 4.35V, then switched to constant voltage charging to 0.05C, charging is stopped, and left to stand for 1 hour.

[0091] Needle prick test procedure:

[0092] Step 1: Using a 5mm diameter steel needle, insert it perpendicularly to the battery plates at a speed of 0.1mm / s. After penetration, leave the needle in the battery for 15 minutes.

[0093] Step 2: Retract the needle at a speed of 0.1 mm / s and check the battery status for 1 hour;

[0094] Step 3: Discharge the battery at a constant current of 0.33C until the cutoff voltage of 2.5V, and monitor the battery status for at least 1 hour after the discharge is completed;

[0095] The standard is: no fire, no explosion, and normal discharge.

[0096] Table 1: Capacity retention rate of pouch cells after 400 cycles at 0.5C / 1C rate and initial efficiency.

[0097]

[0098] The results above demonstrate that batteries employing the coating of this application (especially when the coating thickness is optimized to 3 μm or less) exhibit significantly better first-cycle efficiency and long-cycle stability than Comparative Example 1 without a coating. Furthermore, simultaneous coating of both positive and negative electrodes (Examples 9-11) demonstrates superior overall performance. Negative electrode coating alone (Comparative Example 2) also shows some improvement, but the effect is weaker than positive electrode coating or double-sided coating.

[0099] Coating thickness affects performance. Excessively thick coatings (such as the 4 μm coating in Example 1) may slightly increase interfacial impedance, affecting first-efficiency and rate performance, while excessively thin coatings (such as the 1.25 μm cathode coating in Example 5) show a slight decrease in protective performance during extreme safety testing (nail penetration). Overall, a coating thickness in the range of 1.25–3 μm achieves a good balance between performance and safety.

[0100] Test results: The batteries modified with the coating of this application (such as Examples 2, 6, 9, and 10) did not ignite or explode during the nail penetration test and were able to discharge normally, thus passing the safety test. In contrast, the uncoated battery of Comparative Example 1 experienced a severe short circuit during nail penetration, leading to thermal runaway and fire. This demonstrates that the coating of this application can effectively isolate internal short circuits and significantly improve the battery's safety during abuse.

[0101] In summary, the ultrathin, high-conductivity oxyfluorine electrolyte coating and its application provided in this application effectively improve the interface stability, cycle life, and safety performance of solid-state batteries, and have significant practical value and application prospects.

[0102] The embodiments described in this application are merely illustrative examples. The embodiments of this application are not limited to the above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and shall be included within the protection scope of this application.

Claims

1. A decorative coating, characterized in that, include: Polymer matrix and fast ion conductor filler; The fast ion conductor filler is an oxyfluorine electrolyte, and the chemical formula of the oxyfluorine electrolyte is: Li γ1 X γ2 M2O6F, wherein X = La / Al, La; M = Nb, Ta, 0 ≤ γ1 ≤ 0.8, 0 < γ2 < 4, and its mass fraction accounts for 60~80 wt% of the total mass of the modified coating; The polymer matrix is ​​at least one of polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, and vinylidene fluoride hexafluoropropylene, and its mass fraction accounts for 20-40 wt% of the total mass of the modified coating.

2. The decorative coating according to claim 1, characterized in that, The oxygen-fluorine electrolyte has a room temperature ionic conductivity >1.0 mS / cm and a particle size of 0.1~1.0 μm.

3. A method for preparing the modified coating as described in claim 1 or 2, characterized in that, Includes the following steps: The oxyfluorine electrolyte and the polymer matrix are dissolved in an organic solvent and thoroughly stirred to form a slurry; The slurry is uniformly coated onto the surface of the substrate using pulse spraying technology; subsequently, it is vacuum dried to obtain the modified coating.

4. The method according to claim 3, characterized in that, Both the pulse spraying technology and the drying process are carried out in an environment with a dew point below -40°C.

5. A coated electrode, characterized in that, It includes a current collector and an active material coated thereon, wherein the surface of the active material is coated with a modification coating as described in any one of claims 1-2 or a modification coating prepared by the method described in any one of claims 3-4.

6. The coated electrode according to claim 5, characterized in that, The thickness of the modified coating is 1.25~4μm.

7. The coated electrode according to claim 5, characterized in that, The electrode is a positive electrode, and the active material is a positive electrode active material. The chemical formula of the positive electrode active material is: LiNi. x Co y Mn 1-x-y O2, where 0.5≤x≤0.88, 0.05≤y≤0.

3.

8. The coated electrode according to claim 5, characterized in that, The electrode is a negative electrode, and the active material is a silicon-carbon material, wherein the mass content of Si in the silicon-carbon material does not exceed 20 wt%.

9. A battery, characterized in that, It includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte; the positive electrode is a coated electrode as described in claim 7, and / or the negative electrode is a coated electrode as described in claim 8.

Images