A method for predicting the polymerization degree of a solidified electrode plate prepared by a polymer monomer coating method or a polymer monomer immersion method and application thereof

Abstract

The application provides a polymer monomer coating method or polymer monomer immersion method for preparing a solidified electrode sheet, and a polymerization degree prediction method thereof, which is used for predicting a polymerization degree N prediction value of the solidified electrode sheet by calculation; wherein L is a theoretical polymer monomer feeding amount, which is a ratio of a theoretical polymer monomer surface density after the electrode sheet is coated / immersed to a surface density of active substances, conductive agents and binders when the electrode sheet is not coated / immersed; C is a compacted density of the electrode sheet before the polymer monomer is coated; TD is a true density of the electrode sheet before the polymer monomer is coated; ΔT is a change value of the thickness of the electrode sheet before and after rolling; and ε is a porosity of the solidified electrode sheet. The application develops a predictable polymerization degree evaluation method, especially establishes a prediction model based on easily obtained electrode sheet preparation parameters and initial physical properties, realizes early prediction and accurate regulation and control of the quality of the solidified electrode sheet of the polymer solid-state battery, and accelerates the industrialization process of the polymer solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of battery electrode materials and battery performance prediction technology, and in particular to a method and application for predicting the degree of polymerization of solidified electrodes prepared by polymer monomer coating or polymer monomer immersion. Background Technology

[0002] Polymer solid-state batteries, especially those based on solid-state electrodes formed by polymer monomer polymerization, are highly dependent on the quality and uniformity of the polymerization reaction. The most direct influencing factor is the degree of polymerization. The degree of polymerization directly reflects the content of residual monomers, and this parameter is directly related to the side reactions, interfacial impedance, electrode mechanical strength, and safety stability of the solid-state battery prepared from that electrode. Therefore, accurately assessing and controlling the degree of polymerization within the solid-state electrode is a core step in ensuring the electrochemical performance and reliability of the battery.

[0003] Currently, direct and accurate detection of the polymerization degree of solid-state electrodes faces significant technical challenges, and commonly used chemical analysis methods are complex to operate. Furthermore, because the polymerization reaction is affected by various factors such as temperature field, initiator distribution, and precursor penetration depth, the polymerization degree inside the electrode (from the surface to the current collector interface, from the center to the edge) may have a gradient distribution, making it difficult for point sampling or surface measurements to reflect the overall situation.

[0004] Current technologies lack effective models for quantitatively predicting the degree of polymerization within the electrode based directly on measurable preparation parameters (such as monomer feed rate, electrode thickness, and porosity). Process engineers often rely on experience for adjustments, making precise and repeatable process control difficult. Furthermore, the inability to conveniently and accurately obtain the key internal state variable of the degree of polymerization hinders closed-loop optimization of the solid-state process. This makes it difficult to systematically establish the relationship between the degree of polymerization, microstructure, and macroscopic electrochemical performance during battery R&D, thus impeding rapid material screening and efficient system development.

[0005] Because the polymerization reaction occurs within the complex three-dimensional porous structure of the electrode, the electrode's microstructure, such as porosity and pore distribution, reflects the filling and distribution of polymer monomers. Different monomer feed rates and coating thicknesses will also produce different polymerization kinetics, leading to different polymer network morphologies and degrees of polymerization. This makes the degree of polymerization closely coupled with the initial physical state of the electrode and the preparation process parameters.

[0006] Therefore, developing a predictable method for evaluating the degree of polymerization, particularly establishing a predictive model based on readily available electrode preparation parameters and initial physical properties, is of crucial industrial and scientific value. This paper provides a novel and practical technical solution to address the aforementioned challenges, enabling early prediction and precise control of the quality of solid-state electrodes in polymer solid-state batteries, thereby improving overall battery performance and manufacturing capabilities, and accelerating the industrialization of polymer solid-state batteries. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies, such as the complexity of solid-state electrode polymerization degree detection and the lack of methods for predicting battery electrochemical performance based on relevant parameters of the solid-state electrode before battery fabrication. This invention aims to establish a quantitative correlation model between the polymerization degree and key parameters such as solid-state electrode porosity, polymer monomer loading amount, and electrode thickness variation. It provides a method for predicting the polymerization degree of solid-state electrodes prepared by polymer monomer coating or immersion methods. This method accurately predicts the polymerization degree of solid-state electrodes based solely on their porosity, combined with other conventional physical characteristics and preparation parameters. Furthermore, it can predict the specific capacity of the main cell material and electrode swelling, providing a more accurate method for evaluating the electrochemical performance of cells assembled from solid-state electrodes. This contributes to the performance prediction and development of solid-state electrodes with excellent electrochemical performance, providing crucial technical support for the development of solid-state batteries.

[0008] The applicant discovered in their research that by anchoring key parameters affecting porosity, a predictive correlation could be established between porosity and the degree of polymerization. By establishing a mapping relationship between the degree of polymerization N and the electrode porosity ε, the applicant developed the following electrode porosity screening model based on the degree of polymerization N, including the following steps: S1: The mass fraction of uncured polymer monomers in the extraction solution is obtained by extracting the solidified electrode sheet; S2: Calculate the degree of polymerization N of the solidified electrode based on the mass fraction of the uncured polymer monomers obtained in S1; When solidified electrodes are prepared using polymer monomer coating / polymer monomer immersion, the degree of polymerization N of the solidified electrodes is calculated using the following formula (F1); , formula (F1); When solidified electrodes are prepared using the polymer monomer slurry addition method, the degree of polymerization N of the solidified electrodes is calculated using the following formula (F2); , formula (F2); Where W0 is the mass of the pre-coated / immersed polymer monomer electrode; W1 is the mass of the solidified electrode; W2 is the mass of the extraction solvent; mi is the mass fraction of uncured polymer monomer in the extraction solution characterized by gas chromatography-mass spectrometry after each extraction; n is the number of extractions; C2 is the areal density of the solidified electrode; A is the solvent volatility coefficient, which is the ratio of the mass of the extraction solvent that evaporated to the mass of the extraction solvent after being placed in a sealed box for 5 days at 1 standard atmosphere at room temperature; S is the area of ​​the solidified electrode cut out; X is the ratio of the mass of polymer monomer added to the total mass of active material, conductive agent and binder added when preparing the solidified electrode; S3: Calculate the predicted porosity ε of the solidified electrode based on the degree of polymerization N obtained in S2, combined with the physical characteristics and preparation parameters during the solidified electrode preparation process. When solidified electrodes are prepared using polymer monomer coating / polymer monomer immersion methods, the predicted porosity ε of the solidified electrode is calculated using the following formula (F3): , formula (F3); When solidified electrodes are prepared using the polymer monomer slurry addition method, the predicted porosity ε of the solidified electrode is calculated using the following formula (F4): , formula (F4) Wherein, the degree of polymerization N is calculated as the ratio of the mass of the polymer monomer solidified in the solidified electrode to the mass of the polymer monomer remaining on the electrode after coating / soaking / slurry addition; the polymer monomer density coefficient P is the density ratio of the polymer monomer to poly(ethylene glycol) diacrylate at a temperature of 25°C; where L is the theoretical polymer monomer feed amount, which is the ratio of the theoretical polymer monomer areal density after coating / soaking to the areal density of the active material, conductive agent, and binder when the electrode is not coated / soaked; C is the compacted density value of the electrode before coating / soaking / slurry addition of polymer monomer; TD is the true density of the electrode before coating / soaking / slurry addition of polymer monomer; and ΔT is the change in thickness of the rolled electrode before and after coating / soaking / slurry addition of polymer monomer. The unit of measurement for C2 is g / cm³. 2 The unit of measurement for S is cm. 2 The units for W0, W1, and W2 are g; the unit of measurement for C is g / cm³. 3 The unit of measurement for TD is g / cm³. 3 The unit of measurement for △T is μm.

[0009] Therefore, the above correspondence provides a good correspondence verification for the present invention. A reverse strategy can be adopted to predict the degree of polymerization by measuring the porosity, thereby obtaining a method for predicting the degree of polymerization of solidified electrodes prepared by polymer monomer coating method or polymer monomer immersion method.

[0010] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for predicting the degree of polymerization of solidified electrodes prepared by polymer monomer coating or polymer monomer immersion, wherein the method for predicting the degree of polymerization N of the solidified electrode is calculated by the following formula (1): , formula (1); Where L is the theoretical amount of polymer monomers fed, which is the ratio of the theoretical areal density of the polymer monomers after coating / immersion to the areal density of the active material, conductive agent, and binder when the electrode is not coated / immersed; C is the compacted density of the electrode before coating with polymer monomers; TD is the true density of the electrode before coating with polymer monomers; ΔT is the change in thickness of the rolled electrode before and after coating with polymer monomers; ε is the porosity of the solidified electrode. The unit of measurement for C is g / cm³. 3 The unit of measurement for TD is g / cm³. 3 The unit of measurement for △T is μm.

[0011] The formulas in this invention correspond to values ​​under measurement units, but do not have a correspondence between physical quantities of units.

[0012] This invention innovatively proposes a method for predicting the degree of polymerization in the preparation of solidified electrodes using polymer monomer coating or polymer monomer immersion methods. Based on the porosity and other characteristics of the solidified electrodes, this invention achieves accurate prediction of the degree of polymerization. This prediction provides an expected basis for battery electrochemical performance, such as swelling, and offers scientific guidance for battery preparation and finished product performance prediction. The degree of polymerization of the polymer is a crucial parameter in electrode solidification, influenced by multiple factors. There is a dynamic balance relationship between the degree of polymerization, porosity, electrode thickness, and the amount of polymer monomers applied, all of which are interconnected and mutually restrictive. The porosity of the solidified electrode is a direct manifestation of the degree of polymerization, directly reflecting the microscopic changes after solidification. The ratio of the compacted density C of the electrode before polymer monomer coating to the true density TD of the electrode before polymer monomer coating, used in formula (1) of this invention, reflects the proportion of pores in the electrode before polymer monomer coating. This proportion reflects that the pores of the electrode before polymer monomer coating provide corresponding filling space for the polymer monomers, which to some extent also affects the subsequent polymerization effect. The monomer feeding amount L in the formula affects the monomer concentration in the electrode, which in turn directly affects the degree of monomer polymerization. At the same time, it is related to the pore capacity formed by the pore ratio before coating the polymer monomer. Meanwhile, the change in electrode thickness reflects the difference in preparation method. It, together with the feeding amount, affects the feeding basis and feeding state of polymer monomer. Under different polymer monomer feeding amounts and changes in electrode thickness before and after coating, the degree of monomer polymerization will be significantly affected. Based on the above, this invention establishes a formula relationship through a common fitting method (such as establishing a multi-order equation). The established formula (1) combines the initial pore state of the electrode, the difference in preparation method under changes in polymer monomer feeding amount and electrode thickness, and combines the final pore state, which can accurately predict the degree of polymerization of the solidified electrode.

[0013] In this invention, formula (1) is the result of reverse exploration of formulas (F1) to (F4), and the establishment process of formulas (F1) to (F4) is applicable to 2.8 g / cm³. 3 ≤C≤3.6 g / cm 3 The selectable range is 70%≤N≤99%, 0≤L≤20%, 0≤X≤25%. Within this range, more accurate data is obtained, avoiding discrepancies between the actual electrode loading amount and the pre-coating compaction density, as well as prediction deviations under extremely unreasonable conditions. This range can also be used as boundary conditions input into the fitting software during the establishment of formula (1) to obtain the fitting equation. Correspondingly, the applicable selectable range for formula (1) is 2.8 g / cm³. 3 ≤C≤3.6 g / cm 3 , 1%≤ε≤26%, 0≤L≤20%.

[0014] As a further embodiment, the mass W0 of the coated / immersed polymer monomer front electrode and the mass W1 of the solidified electrode are obtained by the following method: three circular pieces with a diameter d of 30 mm are cut from different positions of the coated / immersed polymer monomer front electrode and the solidified electrode, the weight data are recorded after weighing, and the average value is calculated to obtain W0 and W1 respectively. The theoretical polymer monomer areal density after coating / soaking the electrode is obtained by using the ratio of the difference between W1 and W0 to the area of ​​the disc. And / or, the areal density of the electrode material before coating / immersion can be obtained from the ratio of the electrode material mass before coating to the disc area; wherein the electrode material mass before coating / immersion is the disc mass before coating / immersion of polymer monomer minus the current collector mass; wherein the disc area is in cm². 2 .

[0015] As a further approach, the thickness of conventional and solidified electrodes was measured using a micrometer, and the difference in thickness was calculated to obtain the change in electrode thickness ΔT before and after coating with solid polymer monomer.

[0016] As a further method, the porosity ε of the solidified electrode can be obtained by mercury intrusion porosimetry.

[0017] As a further embodiment, the method for preparing solidified electrode sheets by polymer monomer coating is as follows: at a temperature of ≤-40℃, polymer monomers, initiators and prepolymer solvents are prepared into a prepolymer solution, which is then coated onto the already rolled electrode sheet. After the prepolymer solution is completely immersed in the electrode sheet, a solidified electrode sheet is obtained by thermal polymerization or ultraviolet polymerization.

[0018] As a further embodiment, the method for preparing solidified electrode sheets by polymer monomer immersion is as follows: at a temperature of ≤-40℃, polymer monomers, initiators and prepolymer solvents are prepared into a prepolymer solution, the pre-rolled electrode sheet is immersed in the prepolymer solution, and after the prepolymer solution is completely immersed in the electrode sheet, a solidified electrode sheet is obtained by thermal polymerization or ultraviolet polymerization.

[0019] In a second aspect, the present invention provides an application of formula (1) in the degree of polymerization of the solidified electrode described in the first aspect in the screening of solid-state batteries, wherein the porosity of the solidified electrode is 4%≤ε≤18.6% and the degree of polymerization is 80%≤N≤96%; and further preferably the porosity is 12%≤ε≤17% and the theoretical degree of polymerization is 84%≤N≤94%.

[0020] Based on the screening conditions of porosity and predicted degree of polymerization of the aforementioned solidified electrode, the porosity and degree of polymerization parameters obtained in this invention are the core basis for evaluating the final battery performance. Their main effects are on electrode expansion rate, active material specific capacity, and battery safety (such as performance in nail penetration tests). These effects are not isolated or direct, but rather achieved through a complex, multi-level physicochemical transmission mechanism.

[0021] On the one hand, the specific capacity of a battery depends on the transport efficiency of lithium ions and electrons within the electrode. Porosity indirectly reflects the challenges to the transport distance posed by electrode thickness and feed rate in this invention by affecting the tortuosity of the ion transport path: in low-porosity, high-compact electrodes, although interparticle electronic contact may be improved, the ion transport channel may be compressed, especially in thicker electrodes, where ion transport impedance becomes a limiting factor, resulting in insufficient capacity utilization; while in high-porosity, low-compact electrodes, although sufficient space is provided for ion transport, the contact points between active particles and conductive agents may decrease, the electron conduction network becomes sparse and discontinuous, and the lower compaction density may mean an increase in electrode thickness for the same areal capacity, which will also lengthen the electron conduction path, leading to increased ohmic polarization and limiting high-rate performance and capacity utilization. The degree of polymerization reflects the polymer monomer feed rate and electrode thickness in the polymerization degree prediction formula of this invention, which directly affects the ionic conductivity of the solid electrolyte itself and its interfacial contact with the active particles. Incomplete polymerization may leave behind a large number of polymer monomers or oligomers, forming network "islands" that affect ion transport; while proper polymerization can form a continuous ion transport network. The space provided by porosity is partially filled by the electrolyte, thus the pore structure under various factors and the conductivity of the polymer phase together constitute a "dual channel" for ion transport. Their synergistic effect determines the final lithium-ion flux, thereby affecting the specific capacity.

[0022] On the other hand, since thermal runaway behavior is closely related to the internal structural stability, thermal stability, and short-circuit current distribution of the electrode, the porosity defined in this invention reflects the compaction state and heat transfer characteristics of the electrode in this context. During needle puncture, the loose structure of a high-porosity, low-compact electrode results in weaker mechanical interlocking and electronic contact between particles, making short-circuit points easier to form. Furthermore, the initial short-circuit resistance may be low, triggering a large current surge. Simultaneously, the low thermal conductivity of the porous structure hinders heat diffusion along the in-plane direction, causing heat to accumulate rapidly near the puncture point, accelerating local temperature rise. The degree of polymerization reflects the amount of polymer monomers used and the electrode thickness variation in the polymerization degree prediction formula of this invention, which determines the thermal stability of the polymer network and its behavior at high temperatures. A highly polymerized cross-linked network has a higher thermal decomposition temperature, and the appropriate electrode thickness it reflects allows it to maintain mechanical integrity for a longer period under the high temperature at the moment of needle puncture, preventing the electrode structure from collapsing and causing a larger area of ​​internal short circuit. Electrodes with low polymerization degree exhibit poorer thermal stability and are more prone to short circuits and heat accumulation. In addition, the change in electrode thickness reflected by the degree of polymerization affects the interfacial stability. Poorly polymerized interfaces may fail faster under thermal shock, exacerbating side reactions and thermal runaway.

[0023] On the other hand, there is a profound synergistic and restrictive relationship between porosity and the degree of polymerization. The space provided by the pore structure needs to be effectively filled and supported by polymer electrolytes or binders with appropriate mechanical properties. If the porosity is high but the degree of polymerization is insufficient, the polymer network strength is low, and the loose skeleton cannot fully utilize the pore space to build a stable load-bearing structure. It is still prone to collapse and densification during cycling, ultimately leading to expansion. Conversely, if the degree of polymerization is very high but the porosity is extremely low, the buffer space is insufficient, and the rigid polymer network may experience brittle cracking under huge volume change stress due to its inability to coordinate deformation. This will also damage the structure and exacerbate expansion. The aforementioned ranges of porosity and degree of polymerization further reflect the structural characteristics of the polymer, and can further obtain electrodes with lower expansion rates.

[0024] Therefore, porosity and degree of polymerization, as core predictive indicators, are valuable because they are the key to understanding the organic tandem electrode preparation parameters (such as feed rate, compaction density, and polymer selection), microstructural characteristics (such as thickness, pore network, and interface state), and macroscopic electrochemical and safety performance based on the prediction formula of this invention. By accurately predicting these two parameters, this invention can proactively infer the complex performance characteristics derived from or related to them, thereby achieving closed-loop prediction and optimization from electrode manufacturing to battery performance, greatly improving the targeting and efficiency of solid-state battery R&D.

[0025] The features and beneficial effects of this invention are as follows: 1. This invention creatively establishes quantitative mathematical formulas relating the degree of polymerization to key measurable preparation parameters such as porosity (ε), theoretical polymer monomer feed rate (L), initial compaction density of the electrode (C), true density (TD), and thickness variation (ΔT). Without requiring complex direct chemical analysis, it utilizes readily available physical parameters during and after electrode preparation to achieve accurate and convenient prediction of the core state variable within the electrode—the degree of polymerization.

[0026] 2. Traditional point or surface sampling methods are difficult to reflect the gradient distribution of polymerization degree inside the electrode (such as in the thickness direction). The prediction method provided by this invention is essentially based on the overall average parameters of the electrode, and the result reflects the overall average polymerization degree of the electrode, effectively overcoming the problem of insufficient representativeness of local sampling, and providing a powerful tool for evaluating the uniformity and consistency of solidification processes.

[0027] 3. By limiting the range of key parameters, the model exhibits higher predictive reliability within the actual process window. Based on the predicted degree of polymerization and porosity, it can further effectively screen and predict the specific capacity utilization of active materials in electrodes, cycle expansion rate, and even battery safety performance (such as needle penetration pass rate), achieving cross-scale prediction from preparation parameters to battery end-use performance. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of 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.

[0030] The chemical raw materials used in the following examples and comparative examples are all prior art and commercially available. The experimental apparatus and testing equipment used in the following examples and comparative examples are all conventional equipment in the art, and there are no special requirements or limitations.

[0031] As a specific example of the implementation of this invention, detailed cases are provided below: Solid-state electrodes were prepared in Examples 1-14 and Comparative Examples 1-16 within the following ranges: Solid-state electrodes are prepared using polymer monomer coating or polymer monomer immersion methods. A positive electrode slurry containing a binder, a conductive agent, and a positive electrode active material is coated onto a current collector. The mass ratio of the binder, conductive agent, and positive electrode active material in the positive electrode slurry is (0.8~3.0):(0.6~3.0):(94~98.6). The solvent for the positive electrode slurry is N-methylpyrrolidone, and the mass fraction of the binder, conductive agent, and positive electrode active material in the solvent is 65%~75%. The slurry is then subjected to a concentration of 55 mg / cm³. 2 The areal density is coated on the current collector, dried at 80℃, and then the electrode is rolled to obtain a conventional electrode, which is the electrode before coating / immersion of polymer monomer. The thickness T of the electrode before coating polymer monomer is measured using a Mitutoyo digital display micrometer. At a dew point temperature of ≤-40℃ and an ambient temperature of 15-25℃, the polymer monomer, initiator, and prepolymer solvent are prepared into a prepolymer solution according to a mass ratio of (5~100):(0.2~1.8):(0~95) (the mass of the prepolymer solvent can be 0, the total mass ratio of polymer monomer and prepolymer solution is 100, and the mass ratio of initiator to monomer is compared). The polymer monomer is coated or immersed on the rolled electrode according to a mass ratio of (0~20):100 (the mass of polymer monomer does not include 0). After the prepolymer solution is completely immersed in the electrode, a solidified electrode is obtained by thermal polymerization or ultraviolet polymerization. Polymerize at 50℃~80℃ for 20~48h, or UV polymerize at 365 / 385 / 405nm wavelength for 0.5~3min. Use a Mitutoyo digital display micrometer to measure the thickness T2 of the solidified electrode. Calculate the difference between T2 and T to obtain the change in electrode thickness ΔT before and after coating with polymer monomer.

[0032] The compaction density C of the pre-electrode coated with polymer monomer is: .

[0033] The true density TD of the pre-electrode coated with polymer monomer was obtained by gas gravity method using an Ultra PYC 1200e true density analyzer, referring to GB / T 5071-2013 "True Density Test Method for Refractory Materials".

[0034] The mass W0 of the coated solid polymer monomer front electrode and the mass W1 of the solidified electrode are both cut into three circular pieces with a diameter d of 30 mm at different positions of the coated solid polymer monomer front electrode and the solidified electrode by a cutting machine. After weighing and recording the weight data, the theoretical amount of polymer monomer can be obtained based on the weight difference and the area of ​​the circular pieces, and the theoretical amount of polymer monomer L can be obtained.

[0035] Theoretical polymer monomer feeding ratio calculation method: Three circular pieces with a diameter d of 30mm are cut from different positions of the pre-coated and solidified electrode sheets using a cutting machine. After weighing, the weight data is recorded and the average value is calculated. The theoretical areal density of polymer monomer on the electrode sheet can be obtained by the ratio of the average weight difference of a single circular piece before and after coating to the area of ​​the circular piece. The areal density of the material before coating can be obtained by the ratio of the mass of the electrode material before coating (mass of the circular piece before coating minus the mass of the current collector) to the area of ​​the circular piece. The ratio of the theoretical areal density of polymer monomer to the areal density of the material before coating is the theoretical polymer monomer feeding amount L.

[0036] Specifically, the theoretical polymer monomer feed rate L is calculated as follows: .

[0037] When preparing solid-state electrodes using polymer monomer coating / polymer monomer immersion methods, the prepolymer solution taken during the coating process may be residual or lost, and the loss cannot be quantified. The theoretical amount of polymer monomer fed, L, can only be calculated by the above-mentioned weighing method.

[0038] S2 is the cross-sectional area of ​​the pre-electrode coated / immersed with polymer monomer, and S1 is the cross-sectional area of ​​the solidified electrode. The mass W0 of the coated / immersed polymer monomer front electrode and the mass W1 of the solidified electrode are obtained by the following method: three circular pieces with a diameter d of 30 mm are cut from different positions of the coated / immersed polymer monomer front electrode and the solidified electrode, respectively. After weighing, the weight data are recorded and the average value is calculated to obtain W0 and W1 respectively. The theoretical polymer monomer areal density after coating / soaking the electrode is obtained by using the ratio of the difference between W1 and W0 to the area of ​​the disc. The areal density of the electrode material before coating / immersion can be obtained from the ratio of the electrode material mass before coating to the disc area; where the electrode material mass before coating / immersion is the disc mass before coating / immersion of polymer monomer minus the current collector mass; and the disc area is in cm². 2 .

[0039] The current collector, binder, conductive agent, positive electrode active material, polymer monomer, and initiator are not specifically limited.

[0040] As an example, the current collector is selected from any type of metal foil, specifically, it may be selected from aluminum foil / carbon-coated aluminum foil or copper foil / carbon-coated copper foil.

[0041] As an example, the adhesive is selected from one or more of polyvinylidene fluoride (PVDF), polyacrylic acid, polyacrylonitrile, and polyvinyl alcohol, specifically, it can be selected from PVDF5130, HSV900, etc.

[0042] As an example, the positive electrode active material is selected from nickel-cobalt-manganese ternary materials, specifically, it can be selected from one or more of NCM622, NCM811, NCM83, NCM9 series, etc.

[0043] As an example, the polymer monomer is selected from one of acrylates, carbonates, fluorinated monomers, phosphorus-containing monomers, and ionic liquids.

[0044] As further examples, acrylate compounds include methyl methacrylate, ethyl acrylate, ethyl cyanoacrylate, polyethylene glycol diacrylate, diethylene glycol diacrylate, butyl acrylate, etc.; carbonates include ethylene ethylene carbonate, vinylene carbonate, propylene carbonate, etc.; fluorinated monomers include hexafluorobutyl methacrylate, hexafluorobutyl acrylate, octafluoropentyl acrylate, etc.; phosphorus-containing monomers include triallyl phosphate, diethyl allylphosphonate, etc.; and ionic liquids include 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-vinyl-3-butylimidazolium bis(fluorosulfonyl)imide salt, 1-allyl-3-methylimidazolium hexafluorophosphate, etc.

[0045] As an example, the initiator is selected from one of azo compounds, organic peroxides, α-hydroxy ketones, and acylphosphine oxides; specifically, it may be selected from one of AIBN, AIBME, TPO, and 819.

[0046] As an example, the prepolymer solvent is selected from one of acetonitrile, ethanol, acetone, methanol, ethylene glycol dimethyl ether, dimethyl carbonate, tetrahydrofuran, N,N-dimethylformamide, chloroform, and N-methylpyrrolidone.

[0047] Solid-state batteries are assembled by combining solid-state positive electrode sheets with graphite / silicon negative electrode sheets, semi-solid electrolyte, and conventional PP / PE separators.

[0048] The following tests and calculations were performed on Examples 1-14 and Comparative Examples 1-16 as described above: The porosity ε of solidified electrodes can be obtained by mercury intrusion porosimetry.

[0049] A 5cm x 5cm sample is cut, rolled into a strip, and placed into a special sealed container for testing, usually a mercury-sealed pressure chamber. The pressure chamber is then installed on a mercury porosimeter, and room-temperature mercury is injected. The pressure in the chamber is gradually increased, causing the pores in the electrode to be gradually filled with mercury. The greater the external pressure, the smaller the radius of the pores that mercury can enter. Finally, the electrical signal generated by the mercury entering the sample pores during the mercury porosimeter process is processed to simulate relevant spectra and calculate the porosity data.

[0050] The polymerization degree prediction method is to calculate the predicted value of polymerization degree N of solid-state electrode using the following formula (1): , formula (1); Where L is the theoretical polymer monomer feed rate, which is the ratio of polymer monomer mass / area density to electrode mass / area density; C is the compaction density of the electrode before polymer monomer coating; TD is the true density of the electrode before polymer monomer coating; ΔT is the change in electrode thickness before and after polymer monomer coating; ε is the porosity of the solidified electrode. The unit of measurement for C is g / cm³. 3 The unit of measurement for TD is g / cm³. 3 The unit of measurement for △T is μm.

[0051] Taking Example 1 as an example, the preparation method of the solidified electrode is as follows: Solid-state electrodes were prepared using a polymer monomer coating method. A positive electrode slurry containing PVDF binder, Super P and CNT conductive agents, and NCM811 positive electrode active material was coated onto aluminum foil. The mass ratio of PVDF, Super P and CNT conductive agents, and NCM811 positive electrode active material in the slurry was 1.3:1.2:97.5. The solvent for the positive electrode slurry was N-methylpyrrolidone (NMP), and the mass fractions of the binder, conductive agent, and positive electrode active material in the solvent were (0.91:0.84:68.25). The slurry was prepared at a concentration of 55 mg / cm³. 2 The areal density is coated on the current collector, dried at 80℃, and then the electrode is rolled to obtain the pre-coated polymer monomer electrode. The thickness T of the pre-coated polymer monomer electrode is measured to be 160.3μm using a Mitutoyo digital display micrometer. At a dew point temperature of ≤-40℃ and an ambient temperature of 20℃, the polymer monomer, initiator, and prepolymer solvent are prepared into a prepolymer solution with a mass ratio of 49.75:0.5:49.75. The prepolymer solution is coated on the rolled electrode with a mass ratio of polymer monomer to the pre-rolled electrode of 8.32:100. After the prepolymer solution is completely immersed in the electrode, the solidified electrode is obtained by thermal polymerization or ultraviolet polymerization. After polymerization at 80℃ for 24 h, or UV polymerization at 385 nm wavelength for 30 s, the thickness T2 of the solidified electrode was measured to be 161.8 μm using a Mitutoyo digital display micrometer. The difference between T2 and T was used to calculate the thickness change ΔT of the electrode before and after polymer monomer coating, which was 1.5 μm. The actual compaction density C of the electrode before polymer monomer coating was 3.43 g / cm³. 3 The true density (TD) of the polymer monomer-coated front electrode is 4.635 g / cm³. 3 .

[0052] The mass W0 of the pre-coated solid polymer monomer electrode and the mass W1 of the solidified electrode were both determined by cutting three circular pieces with a diameter d of 30 mm at different positions on the pre-coated solid polymer monomer electrode and the solidified electrode, respectively, using a cutting machine. After weighing, the weight data was recorded and the average value was calculated. The theoretical areal density of the polymer monomer on the electrode can be obtained by the ratio of the average weight difference of the single circular piece before and after coating to the area of ​​the circular piece. The areal density of the material before coating can be obtained by the ratio of the mass of the electrode material before coating (mass of the circular piece before coating minus the mass of the current collector) to the area of ​​the circular piece. The ratio of the theoretical areal density of the polymer monomer to the areal density of the material before coating is the theoretical polymer monomer feeding amount L. Through the above measurements, W0 is 1.1663 g; W1 is 1.2633 g; and the theoretical polymer monomer feeding amount L is 8.32%. The porosity ε of the solidified electrode was found to be 15.15% by mercury porosimetry.

[0053] The polymerization degree prediction method calculates the polymerization degree N of the solidified electrode using formula (1), and the predicted value is 84.51%.

[0054] The degree of polymerization was verified using the following method: Electrodes coated with unpolymerized solid polymer monomers and solidified electrodes with completed polymerization were taken. Appropriate shapes / areas of electrodes were cut from each method, and their weight before and after solidification was measured to obtain the amount of monomer added during curing. To remove uncured monomers, the solidified electrodes were baked under high vacuum, with gas changes every 4 hours (baked in a vacuum oven at -95 kPa and 50°C for 5 days, with gas changes every 4 hours). Uncured monomers were extracted until no significant weight change was observed after cutting the cured electrodes. This yielded the actual amount of monomer added and the degree of curing. This method has a longer baking time, and the results differ from the method described above by ±3%, indicating that the above method for calculating the degree of monomer polymerization is more accurate.

[0055] The degree of polymerization can also be verified by extraction. The verification method is as follows: the solidified electrode prepared in the above examples is extracted n times. For each extraction, the solidified electrode is placed in acetonitrile (mass W2) of extraction solvent (2g). Extraction continues until the mass fraction of uncured polymer monomers detected in the extraction solution is ≤0.1%. Then, extraction is stopped, and a polymerization inhibitor MEHQ is added according to the polymer monomer type (poly(ethylene glycol) diacrylate). The polymerization inhibitor accounts for 0.01% of the mass in the extraction solvent. After ultrasonication for 10 minutes under sealed conditions at 20-25℃, the solution is soaked for 8 hours to obtain the extraction solution. The same amount (2g) of extraction solvent is used for each extraction. The mass fraction mi of uncured polymer monomers in the extraction solvent is obtained by gas chromatography-mass spectrometry (GC-MS). In this example, m1 is 0.45%, m2 is 0.25%, and m3 is 0.08%. The degree of polymerization N of the solidified electrode is calculated using formula (F1). Where A is the solvent evaporation coefficient, which is the ratio of the mass of the extraction solvent that evaporates to the mass of the extraction solvent after being placed in a sealed box for 5 days at 1 standard atmosphere at room temperature. When the extraction solvent is acetonitrile, A is 1.9%; when the extraction solvent is isopropanol, A is 1.3%; when the extraction solvent is dichloromethane, A is 10.2%; and when the extraction solvent is n-propanol, A is 1%.

[0056] The following tests were performed on Examples 1-14 and Comparative Examples 1-16: Electrode swelling rate: After being soaked in electrolyte for 24 hours, the solidified electrode will swell and its thickness will increase. The thickness data of the solidified electrode before and after soaking is tested, and the ratio of the thickness difference to the thickness before soaking is the electrode swelling rate.

[0057] Positive electrode specific capacity test: The shipped battery cell is charged and discharged at 0.1C. The ratio of the 0.1C discharge capacity to the mass of the positive electrode material is the specific capacity data of the positive electrode.

[0058] Needle penetration test: At 25±3℃, a steel nail is inserted into the center of a fully charged fresh battery cell at a speed of 150 mm / s until it is completely penetrated. The nail is held for 10 minutes and then withdrawn. The diameter of the steel nail is 4±0.06 mm. After the test is completed, the combustion and temperature data during the needle penetration process are recorded.

[0059] The data obtained from the above tests for Examples 1-14 and Comparative Examples 1-16 are shown in Table 1 below.

[0060] Table 1

[0061] Table 2 shows the comparison between the degree of polymerization N obtained by the extraction method in Examples 1-14 and Comparative Examples 1-16 and the N calculated by formula (1).

[0062] Table 2

[0063] As can be seen from the comparison of Examples 1-14 and Comparative Examples 1-16, the polymerization degree prediction formula established in this invention and the battery screening parameter range set based on the formula have been fully verified. Table 1-2 shows that the theoretical polymerization degree N calculated based on the formula in all examples and comparative examples is basically consistent with the polymerization degree N obtained by the extraction method, with an absolute deviation of ≤3.5%.

[0064] Using the porosity ε of the solidified electrode and the predicted degree of polymerization N to screen for comprehensive battery performance, Examples 1-14 show that when 4%≤ε≤18.6% and 80%≤N≤96%, the prepared electrode exhibits a lower expansion rate, higher specific capacity of the positive electrode active material, and the assembled batteries all perform excellently in the nail penetration test. This confirms that the degree of polymerization obtained under this formula fully reflects the combined relationship between parameters such as porosity and polymer monomer loading in the formula. The above parameter range can effectively synergistically regulate the ion / electron transport network, interface stability, and mechanical structure integrity, thereby comprehensively optimizing the electrochemical and safety performance of the battery.

[0065] The data from Comparative Examples 1 to 15 show that when ε and / or N deviate from the above ranges, one or more key performance indicators of the battery deteriorate significantly. For example, a low degree of polymerization (N) is usually accompanied by poor safety; while a low porosity (ε) may lead to uncontrolled expansion and deterioration of electronic conduction, resulting in reduced capacity utilization.

[0066] A comparison of Examples 1-4 with Examples 5-14 shows that by further setting the solid-state battery screening method to 12%≤ε≤17% and 84%≤N≤94%, the battery achieved higher positive electrode specific capacity, better needle penetration pass rate, and the electrode expansion rate was controlled at a more suitable level. This indicates that the parameter combination of 12%≤ε≤17% and 84%≤N≤94% represents a more precise balance between ion transport channels, electron conduction networks, and polymer structural stability.

[0067] These results clearly demonstrate that the polymerization degree prediction method provided by this invention not only possesses theoretical innovation but also has extremely strong engineering guidance value. It correlates the internal reaction state (polymerization degree), which is difficult to measure directly, with easily obtainable preparation parameters and macroscopic physical properties (porosity, thickness variation, etc.), and successfully defines a key parameter window corresponding to excellent overall performance. This shows that the formula can fully reflect the coupling relationship between the initial electrode pore state, monomer filling level, and polymerization kinetics, forming a comprehensive prediction tool that profoundly reflects the essence of the solid-state process. This provides a powerful tool for the quantitative design of solid-state electrode quality, precise process control, and reliable prediction of battery performance, which will greatly improve the R&D efficiency and product consistency of polymer solid-state batteries, and is of great significance for promoting their industrialization.

[0068] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A method for predicting the degree of polymerization in the preparation of solidified electrodes using a polymer monomer coating method or a polymer monomer immersion method, characterized in that, The polymerization degree prediction method is to calculate the predicted value of the polymerization degree N of the solidified electrode using the following formula (1): Formula (1); Where L is the theoretical amount of polymer monomers fed, which is the ratio of the theoretical areal density of the polymer monomers after coating / immersion to the areal density of the active material, conductive agent, and binder when the electrode is not coated / immersed; C is the compacted density of the electrode before coating with polymer monomers; TD is the true density of the electrode before coating with polymer monomers; ΔT is the change in thickness of the rolled electrode before and after coating with polymer monomers; ε is the porosity of the solidified electrode. The unit of measurement for C is g / cm³. 3 The unit of measurement for TD is g / cm³. 3 The unit of measurement for △T is μm.

2. The aggregation degree prediction method according to claim 1, characterized in that, In the formula (1), 2.8 g / cm 3 ≤C≤3.6 g / cm 3 , 1%≤ε≤26%, 0≤L≤20%.

3. The aggregation degree prediction method according to claim 1, characterized in that, The mass W0 of the coated / immersed polymer monomer front electrode and the mass W1 of the solidified electrode are obtained by the following method: three circular pieces with a diameter d of 30 mm are cut from different positions of the coated / immersed polymer monomer front electrode and the solidified electrode, the weight data are recorded after weighing, and the average value is calculated to obtain W0 and W1 respectively. The theoretical polymer monomer areal density after coating / soaking the electrode is obtained by using the ratio of the difference between W1 and W0 to the area of ​​the disc. And / or, the areal density of the electrode material when the electrode is not coated / soaked can be obtained from the ratio of the mass of the electrode material before coating to the area of ​​the disc; The mass of the electrode material before coating / immersion is the mass of the wafer before coating / immersion of the polymer monomer minus the mass of the current collector; the unit of wafer area is cm². 2 .

4. The aggregation degree prediction method according to claim 1, characterized in that, The thickness of conventional and solidified electrodes was measured using a micrometer, and the difference in thickness was calculated to obtain the change in electrode thickness ΔT before and after coating with solid polymer monomer.

5. The aggregation degree prediction method according to claim 1, characterized in that, The porosity ε of solidified electrodes can be obtained by mercury intrusion porosimetry.

6. The aggregation degree prediction method according to claim 1, characterized in that, The method for preparing solidified electrode sheets by polymer monomer coating is as follows: at a temperature of ≤-40℃, polymer monomers, initiators and prepolymer solvents are prepared into a prepolymer solution, which is then coated onto the already rolled electrode sheet. After the prepolymer solution is completely immersed in the electrode sheet, a solidified electrode sheet is obtained by thermal polymerization or ultraviolet polymerization.

7. The aggregation degree prediction method according to claim 1, characterized in that, The method for preparing solidified electrode sheets by polymer monomer immersion is as follows: at a temperature of ≤-40℃, polymer monomers, initiators and prepolymer solvents are prepared into a prepolymer solution, and the pre-rolled electrode sheet is immersed in the prepolymer solution. After the prepolymer solution is completely immersed in the electrode sheet, a solidified electrode sheet is obtained by thermal polymerization or ultraviolet polymerization.

8. The application of formula (1) in the method for predicting the degree of polymerization of solid-state electrode as described in any one of claims 1 to 7 in the screening of solid-state batteries, characterized in that, The porosity of the solidified electrode is 4%≤ε≤18.6%, and the degree of polymerization is 80%≤N≤96%.

9. The application according to claim 8, characterized in that, The predicted porosity of the solidified electrode is 12%≤ε≤17%, and the degree of polymerization is 84%≤N≤94%.

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