A lithium ion battery electrode and a design method thereof, and a lithium ion battery
By simplifying the electrochemical process into two key characteristic length formulas, and controlling the ratio of the salt diffusion limit thickness to the charge transport limit thickness of the porous electrode film, the problem of capacity decay of thick electrodes at high rates is solved, achieving efficient capacity retention and improved energy density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU RELIANCE ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2026-04-02
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies, when increasing the thickness of lithium-ion battery electrodes, suffer from limitations in lithium salt transport at high rates or excessive ohmic polarization leading to rapid capacity decay. The lack of systematic theoretical guidance results in shortcomings in the designed electrodes in terms of conductivity or mass transfer, preventing the realization of energy density benefits.
By simplifying the electrochemical process into two key characteristic length formulas, the ratio of the salt diffusion limit thickness to the charge transport limit thickness of the porous electrode film is controlled within a suitable range to ensure that the electron transport capability matches the ion transport capability. Mathematical boundary design is used for thick electrodes.
It significantly improves the capacity retention of thick electrodes at high rates, guides the adjustment of electrode micro-process through theoretical formulas, avoids blind trial and error, saves costs, and improves efficiency.
Smart Images
Figure CN122158455A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery electrode and its design method, and a lithium-ion battery. Background Technology
[0002] With the increasing demands for range in electric vehicles and portable electronic devices, increasing the thickness of the active material coating on lithium-ion battery electrodes is the most direct and effective way to improve the energy density of a single battery cell. Theoretically, doubling the electrode thickness can significantly improve the volumetric energy density. However, in practical applications, thick electrode technology faces a serious "rate-capacity" trade-off: when the electrode thickness L increases, especially under high-rate (e.g., >2C) discharge conditions, the actual battery capacity does not increase proportionally, but rather experiences a precipitous drop. Specifically: Lithium salt depletion: The lithium ion concentration deep in the electrode (near the current collector side) drops sharply to zero, forming a "dead zone". The active material cannot be used due to the lack of reactants; Intensified polarization: The long-distance transport of electrons in the solid phase and ions in the liquid phase leads to a huge ohmic voltage drop, which makes the overpotential η deep in the electrode lower than the reaction threshold, and the reaction interface shrinks sharply to the vicinity of the membrane.
[0003] Related technologies include methods to address the aforementioned problems by fabricating porous electrodes, such as adding pore-forming agents to the electrode slurry and combining this with freeze-drying, achieving both high energy density and excellent rate performance. However, this method often relies on trial and error, requiring continuous adjustments to the slurry ratio or optimization of the coating process to improve the electrode porosity, lacking systematic theoretical guidance. This can lead to electrodes with limitations in conductivity (ionic conductivity). Too low or electronic conductivity (Too low), or there is a bottleneck in mass transfer (effective diffusion coefficient). (Too low), so the energy density benefits brought by increased thickness cannot be realized at high magnification.
[0004] Therefore, how to prevent the capacity of thick electrodes from rapidly decaying due to limited lithium salt transport or excessive ohmic polarization at high rates is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0005] To overcome the above problems, this application provides a lithium-ion battery electrode and its design method, as well as a lithium-ion battery. On the one hand, it simplifies the complex electrochemical process into two key characteristic length formulas, providing clear mathematical boundaries for thick electrode design and avoiding blind trial and error. On the other hand, by controlling the ratio of the two key characteristic lengths within a reasonable range, it ensures that the electron transport capability matches the ion transport capability, enabling the electrode material to react synchronously and uniformly at high rates, and significantly improving the capacity retention rate of the thick electrode at high rates.
[0006] To achieve the above objectives, this application adopts the following technical solution: A first aspect of this application provides a lithium-ion battery electrode, comprising a current collector and a porous electrode film disposed on at least one surface of the current collector, wherein the actual thickness of the porous electrode film is [missing information]. The actual thickness satisfy ,in, This indicates the salt diffusion limit thickness of the porous electrode film. The ratio of the charge transport limit thickness of the porous electrode film to the total charge transport thickness is given by the two values. satisfy: .
[0007] In some embodiments, the salt diffusion limit thickness of the porous electrode film is... Its theoretical expression at the microscopic level is: , in, This represents the effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film. , Describing Faraday constant , Indicates the lithium ion concentration in the electrolyte. , Indicates the lithium-ion transference number in the electrolyte. Indicates the active specific surface area , Represents the exchange current density , Represents thermoelectric potential V -1 , It represents the overpotential V.
[0008] In some embodiments, the charge transport limit thickness of the porous electrode film layer is... Its theoretical expression at the microscopic level is: , in, This represents the solid-phase effective electronic conductivity of the porous electrode film. , This indicates the effective liquid-phase ionic conductivity of the porous electrode film. .
[0009] In some embodiments, the effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film is... ,in, Indicates the intrinsic lithium-ion diffusion coefficient of the electrolyte. , Indicates the porosity of the porous electrode. This indicates the tortuosity of the porous electrode.
[0010] In some embodiments, the solid-phase effective electronic conductivity of the porous electrode film is... ,in, The intrinsic conductivity of the porous electrode; the effective ionic conductivity of the porous electrode film in the liquid phase. ,in, This indicates the intrinsic ionic conductivity of the electrolyte.
[0011] In some embodiments, the thermoelectric potential ,in, Indicates the symmetry coefficient of the electrode electrochemical reaction. Represents the gas constant. It represents thermodynamic temperature (K).
[0012] In some embodiments, the salt diffusion limit thickness of the porous electrode film is... and the charge transport limit thickness of the porous electrode film layer The microscopic parameters in the theoretical expression are replaced with macroscopically measurable parameters: when the target discharge rate is determined... And the preset thickness of the porous electrode film is Below, volumetric density The following relationship exists between the electrochemical parameters and the parameters: ， In the above formula, the salt diffusion limit thickness of the aforementioned porous electrode film is... and charge transport limit thickness In theoretical expressions Equivalent substitution to macroscopic current density ,in, Indicates the overall effective conductivity of the electrodes ,and , The volumetric capacity density of the porous electrode film is indicated. ,Depend on Calculations show that This indicates the discharge specific capacity of the active material in the porous electrode film. , The true density of the active material is expressed in g / cm³. 3 , This indicates the discharge rate.
[0013] In some embodiments, the charge transport limit thickness of the porous electrode film layer is... Salt diffusion limit thickness of the porous electrode film ratio satisfy: .
[0014] In some embodiments, the porous electrode film is a positive electrode film or a negative electrode film. The positive electrode film includes a positive electrode active material, which is a lithium-containing transition metal oxide and / or a polyanionic lithium-containing compound. The negative electrode film includes a negative electrode active material, which is a mixture of one or more of graphite, silicon-containing graphite, silicon oxide-containing graphite, and phosphorus-containing compounds.
[0015] A second aspect of this application provides a method for designing a lithium-ion battery electrode, comprising the following steps: S1. Determine the target discharge rate of the battery. and the preset thickness of the porous electrode film ; S2. Determine the charge transport limit thickness of the porous electrode film. Salt diffusion limit thickness of the porous electrode film ratio Satisfying 0.5≤ The thickness of the porous electrode film is required to be ≤1.2. satisfy ; S3. Calculate the minimum target effective lithium-ion diffusion coefficient in the liquid phase possessed by the porous electrode film. Combined effective conductivity with minimum target electrode Substitute according to Calculate the effective electronic conductivity of the target solid phase Target liquid phase effective ionic conductivity The range is 0.1-2 ; S4. By adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode sheet, the actual effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film is improved. Actual solid-phase effective electronic conductivity and actual effective ionic conductivity in liquid phase The target value in step S3 is satisfied.
[0016] In some embodiments, in step S3, the minimum target liquid phase effective lithium-ion diffusion coefficient The calculation formula is as follows: , in, Indicates the lithium-ion transference number in the electrolyte. This represents the volumetric capacity density of the porous electrode film. Denotes Faraday's constant. This indicates the lithium-ion concentration in the electrolyte.
[0017] In some embodiments, the minimum target electrode has a combined effective conductivity. The calculation formula is as follows: , in, It represents thermoelectric potential.
[0018] A third aspect of this application also provides a lithium-ion battery, including a lithium-ion battery electrode or a lithium-ion electrode battery obtained by the aforementioned lithium-ion battery electrode or design method.
[0019] Compared with the prior art, this application has the following advantages: This application provides a lithium-ion battery electrode that, through theoretical design, simplifies the complex electrochemical process into two key characteristic length formulas, providing clear mathematical boundaries for thick electrode design and avoiding blind trial and error; simultaneously, through matching and By controlling the ratio of the two within a suitable range, it is possible to ensure that the electron transport capability matches the ion transport capability, so that the electrode material can react synchronously and uniformly at high rates, and significantly improve the capacity retention rate of thick electrodes at high rates.
[0020] The second aspect of this application provides a design method for lithium-ion battery electrodes, which first clarifies the target high rate of operation and the preset electrode thickness, while also satisfying high capacity utilization and matching appropriate... and The target diffusion coefficient and target conductivity are calculated based on the formula proposed in this application, which is convenient for engineering applications. Then, the microstructure parameters of the electrode, such as compaction density, tortuosity, and electrolyte formulation, are adjusted according to the theoretical expression so that the experimentally measured actual diffusion coefficient and actual conductivity values meet the aforementioned target values. This realizes that the theoretical formula guides the adjustment of the electrode microprocess, which to a certain extent guides the optimization of the system formulation, avoids blind trial and error, saves raw material costs, and improves efficiency.
[0021] The third aspect of this application provides a lithium-ion battery that significantly improves the capacity retention rate of thick electrodes at high rates by using the lithium-ion battery electrode designed above, thereby controlling the capacity retention rate of the lithium-ion battery to be above 98%. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below.
[0023] Figure 1 This is a graph showing the voltage and capacity retention of the batteries obtained in Examples 1-7 and Comparative Examples 1-3 of this application.
[0024] Figure 2 This is a graph showing the total discharge energy versus time of the batteries obtained in Examples 1-7 and Comparative Examples 1-3 of this application. Detailed Implementation
[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of this application, 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. It should be understood that the specific embodiments described are merely used to explain this application and are not intended to limit this application.
[0026] In the description of the embodiments of this application, it should be noted that all scopes disclosed in this application are to be understood to encompass any and all subscopes included therein. For example, the stated scope "0.5-1.2" should be considered to include any and all subscopes that begin with a minimum value of 0.5 or greater and end with a maximum value of 1.2 or less, such as 0.5 to 0.8, or 0.8 to 1.0, or 0.8 to 1.2. Furthermore, all scopes disclosed in this application are also considered to include the endpoints of the scope, unless otherwise expressly stated. For example, scopes "between 0.8 and 1.0," "0.8 to 1.0," or "0.8-1.0" should generally be considered to include the endpoints 0.8 and 1.0.
[0027] In the description of this embodiment, unless otherwise explicitly defined, terms such as "setting," "installing," and "connecting" should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of these terms in this embodiment based on the specific content of the technical solution. Furthermore, the use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, the number of indicated technical features, or the order of the indicated technical features.
[0028] Traditional thick electrode designs for lithium-ion batteries often rely on a trial-and-error approach, optimizing by adjusting slurry ratios or coating processes, lacking systematic theoretical guidance. This results in electrodes with limitations in conductivity (ionic conductivity). Too low, or electronic conductivity (Too low), or there is a bottleneck in mass transfer (effective diffusion coefficient). (If the porosity is too low), blindly increasing the conductive agent or porosity will be ineffective. Therefore, there is an urgent need in this field for theoretical formulas to guide formulation optimization, thereby saving R&D costs and improving efficiency. The concept of this application is to simplify the complex electrochemical process into two key characteristic length formulas through theoretical design, providing clear mathematical boundaries for thick electrode design and avoiding blind trial and error; at the same time, through matching and By controlling the ratio of the two within a suitable range, it is possible to ensure that the electron transport capability matches the ion transport capability, so that the electrode material can react synchronously and uniformly at high rates, and significantly improve the capacity retention rate of thick electrodes at high rates.
[0029] To achieve the above objectives, this application adopts the following technical solution: A first aspect of this application provides a lithium-ion battery electrode, comprising a current collector and a porous electrode film disposed on at least one surface of the current collector, wherein the actual thickness of the porous electrode film is [missing information]. The actual thickness satisfy ,in, This indicates the salt diffusion limit thickness of the porous electrode film. The ratio of the charge transport limit thickness of the porous electrode film to the total charge transport thickness is given by the two values. satisfy: .
[0030] It should be noted that this application reveals two competing characteristic lengths in porous electrodes at high magnification: the salt diffusion limit thickness. With charge transport limit thickness Furthermore, this paper proposes an electrode design criterion based on the competition mechanism between the two characteristics. Through rigorous mathematical and physical derivation—dimensionless and asymptotic analysis based on the Newman model—this application determines that the actual thickness of the effective reaction layer of the electrode is taken from the minimum of the two characteristic lengths mentioned above, because when the thickness of the porous electrode film exceeds... Value, near the current collector region will fail due to salt deficiency; when the thickness of the porous electrode film exceeds The value, near the current collector region, will fail due to insufficient overpotential. The Newman electrochemical polarization model, based on concentrated solution theory and porous electrode theory, is a quasi-two-dimensional model that combines mass transfer and potential distribution in electrochemical processes.
[0031] It is understandable that the salt diffusion limit thickness of the electrode... This indicates the maximum depth to which lithium ions in the electrolyte can penetrate into the electrode film before being completely consumed by the reaction; it is determined by the mass transfer process of lithium ions within the electrode film; charge transport limit thickness. This represents the maximum depth to which electrons and ions can co-conduct before the ohmic voltage drop destroys the driving force of the reaction, and it is determined by the ohmic voltage drop between the solid and liquid phases within the electrode film. Therefore, the actual thickness of the electrode film is necessarily limited by the "weakest link" in the aforementioned two processes, for example, when... When this occurs, it indicates that mass transfer is the bottleneck; conversely, when... This indicates that conductivity is the bottleneck. Therefore, the two limiting thicknesses must be matched to eliminate the "weakest link effect." In other words, the ratio of their thicknesses needs to be strictly limited to a reasonable range.
[0032] It should be noted that the units for the actual thickness, salt diffusion limit thickness, and charge transport limit thickness of the porous electrode film are all [missing information]. .
[0033] In some possible implementations, the electrode film thickness can be controlled between 15-150 mm. For example, 20-120 For example, it can be 20 30 40 50 60 70 80 90 100 110 and 120 The range of any one or any two values in the range.
[0034] In some possible implementations, the ratio satisfy .
[0035] Furthermore, the ratio Furthermore, the ratio .
[0036] In some embodiments, the salt diffusion limit thickness of the porous electrode film is... Its theoretical expression is: , in, This represents the effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film. , Describing Faraday constant , Indicates the lithium ion concentration in the electrolyte. , Indicates the lithium-ion transference number in the electrolyte. Indicates the active specific surface area 1 / m². Represents the exchange current density , Represents thermoelectric potential V -1 , It represents the overpotential V.
[0037] Among them, the effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film is ,in, Indicates the intrinsic lithium-ion diffusion coefficient of the electrolyte. , Indicates the porosity of the porous electrode. This indicates the tortuosity of the porous electrode.
[0038] Among them, thermoelectric potential ,in, Indicates the symmetry coefficient of the electrode electrochemical reaction. Represents the gas constant. It represents thermodynamic temperature (K).
[0039] In some embodiments, the charge transport limit thickness of the porous electrode film layer is... Its theoretical expression is: , in, This represents the solid-phase effective electronic conductivity of the porous electrode film. , This indicates the effective liquid-phase ionic conductivity of the porous electrode film. .
[0040] In some possible implementations, the solid-phase effective electronic conductivity of the porous electrode film is... ,in, The intrinsic conductivity of the porous electrode; the effective ionic conductivity of the porous electrode film in the liquid phase. ,in, This indicates the intrinsic ionic conductivity of the electrolyte.
[0041] It should be noted that, for ease of engineering application, the salt diffusion limit thickness of the porous electrode film can typically be [not specified]. and the charge transport limit thickness of the porous electrode film layer The microscopic parameters in the theoretical expression are replaced with macroscopically measurable parameters.
[0042] In some possible implementations, when determining the target discharge rate... And the preset thickness of the porous electrode film is Below, volumetric density The following relationship exists between the electrochemical parameters and the parameters: , In the above formula, the salt diffusion limit thickness of the aforementioned porous electrode film is... and charge transport limit thickness Parameters involved in the theoretical expression Equivalent substitution to macroscopic current density ,in, Indicates the overall effective conductivity of the electrodes ,and , The volumetric capacity density of the porous electrode film is indicated. ,Depend on Calculations show that This indicates the discharge specific capacity of the active material in the porous electrode film. , The true density of the active material is expressed in g / cm³. 3 , This indicates the discharge rate.
[0043] In some embodiments, the charge transport limit thickness of the porous electrode film layer is... Salt diffusion limit thickness of the porous electrode film ratio satisfy: .
[0044] In some embodiments, the porous electrode film is a positive electrode film, which includes a positive electrode active material, and the positive electrode active material is a lithium-containing transition metal oxide and / or a polyanionic lithium-containing compound.
[0045] In some possible implementations, the lithium-containing transition metal oxide and the polyanionic lithium-containing compound are typically materials commonly used in the art, such as one or more of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), and lithium manganese oxide (LMO); the polyanionic lithium-containing compound is, for example, one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium iron silicate, and lithium manganese silicate.
[0046] In some possible implementations, the porous electrode film may also be a negative electrode film, which includes a negative electrode active material, and the negative electrode active material is one or more of graphite, silicon-containing graphite, silicon oxide-containing graphite, and phosphorus-containing compounds.
[0047] A second aspect of this application provides a method for designing a lithium-ion battery electrode, comprising the following steps: S1. Determine the target discharge rate of the battery. and the preset thickness of the porous electrode film ; S2. Determine the charge transport limit thickness of the porous electrode film. Salt diffusion limit thickness of the porous electrode film ratio Satisfying 0.5≤ The thickness of the porous electrode film is required to be ≤1.2. satisfy ; S3. Calculate the minimum target effective lithium-ion diffusion coefficient in the liquid phase possessed by the porous electrode film. Combined effective conductivity with minimum target electrode Substitute according to Calculate the effective electronic conductivity of the target solid phase Target liquid phase effective ionic conductivity The range is 0.1-2 ; S4. Adjust the compaction density, tortuosity, and electrolyte formulation of the electrode to improve the actual effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film. Actual solid-phase effective electronic conductivity and actual effective ionic conductivity in liquid phase The target value in step S3 is satisfied.
[0048] It should be noted that the design approach of this application for thick electrodes that meet performance requirements is to first clearly define the target high rate of operation and the preset electrode thickness, while also ensuring high capacity utilization and matching appropriate... and The target diffusion coefficient and target conductivity are calculated based on the formula proposed in this application, which is convenient for engineering applications. Then, the microstructure parameters of the electrode, such as compaction density, tortuosity, and electrolyte formulation, are adjusted according to the theoretical expression so that the experimentally measured actual diffusion coefficient and actual conductivity values meet the aforementioned target values. This realizes that the theoretical formula guides the adjustment of the electrode microprocess, which to a certain extent guides the optimization of the system formulation, avoids blind trial and error, saves raw material costs, and improves efficiency.
[0049] In some embodiments, in step S3, the minimum target liquid phase effective lithium-ion diffusion coefficient The calculation formula is as follows: , in, Indicates the lithium-ion transference number in the electrolyte. This represents the volumetric capacity density of the porous electrode film. Denotes Faraday's constant. This indicates the lithium-ion concentration in the electrolyte.
[0050] In some embodiments, the minimum target electrode has a combined effective conductivity. The calculation formula is as follows: , in, It represents thermoelectric potential.
[0051] It should be noted that, based on the obtained minimum target electrode comprehensive effective conductivity combined with the formula... The solid-phase effective electronic conductivity of the target porous electrode film can be calculated. Values, thus based on microscopic expressions , , This guides the adjustment of electrode compaction density, tortuosity, and electrolyte formulation to improve the actual effective electronic conductivity of the solid phase. Actual effective ionic conductivity in liquid phase and actual effective diffusion coefficient The target value is met, where the target effective ionic conductivity of the liquid phase is... The range is 0.1-2 For example, 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 and 2.0 The range of any one or any two values in the range.
[0052] A third aspect of this application also provides a lithium-ion battery, including a lithium-ion battery electrode or a lithium-ion electrode battery obtained by the aforementioned lithium-ion battery electrode or design method.
[0053] The following examples will further illustrate this application.
[0054] All raw materials used in the embodiments of this application are commercially available. In addition, it should be understood that the adjustment and testing methods not specifically described in this application can be achieved by conventional means in the art.
[0055] Example 1 This embodiment 1 provides a high-rate electrode design, aiming to design a porous electrode film with a thickness of [missing information]. The NCM811 cathode is required to achieve a capacity utilization rate of over 90% at a 20C rate.
[0056] The specific steps are as follows: Step 1: Determine the target and intrinsic parameters of the material Target multiplier Volumetric density Initial concentration of electrolyte Lithium-ion transference number Faraday constant Thermoelectric potential: 1 / V Step 2: Determine the required diffusion coefficient based on the mass transfer limitation. according to Substitute Calculate the required effective diffusion coefficient : therefore, .
[0057] Step 3: Determine the required conductivity based on charge transport constraints. according to and Substitute Calculate the required overall effective conductivity of the electrodes. .
[0058] =1, then therefore, Using the effective ionic conductivity of the liquid phase For an electrolyte with a conductivity of 0.8 S / m, the total conductivity formula is used to... The effective solid-phase electronic conductivity of the porous electrode film was calculated by substituting the inputs. .
[0059] Step 4: Preparation and Verification According to calculations, the relationship between the effective electronic conductivity, ionic conductivity, and effective diffusion coefficient of the solid phase and the intrinsic conductivity of the electrode, the intrinsic ionic conductivity of the electrolyte, and the intrinsic diffusion coefficient of the electrolyte is as follows: , , This allows for the adjustment of the electrode's compaction density and tortuosity. The electrolyte formulation improves the actual effective electronic conductivity of the solid phase. Actual effective ionic conductivity in liquid phase and actual effective diffusion coefficient Meets the standards and satisfies the calculated requirements. , as well as That is, ultimately satisfied ,specific , and In this implementation, the adjusted compaction density of the electrode film layer is 3.53. Porosity =0.22, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte .
[0060] The prepared electrodes were assembled into a full cell, and the voltage and discharge energy were recorded at a 20C rate. The capacity retention rate was obtained from the test. The discharge efficiency was 98.1%, and the total discharge energy was 29.489Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0061] Example 2 This embodiment 2 provides a high-rate electrode design, which differs from embodiment 1 only in that: =1.2, according to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, so that... , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.50. Porosity =0.26, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0062] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The efficiency was 98.11%, and the total discharge energy was 29.595Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0063] Example 3 This embodiment 3 provides a high-rate electrode design, which differs from embodiment 1 only in that: =0.9. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.55. Porosity =0.21, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0064] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 98.06%, and the total discharge energy was 29.448Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0065] Example 4 This embodiment 4 provides a high-rate electrode design, which differs from embodiment 1 only in that: =0.8. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.51. Porosity =0.26, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0066] The prepared electrodes were assembled into a full cell, and the voltage and discharge energy were recorded at a 20C rate. The capacity retention rate was obtained from the test. The discharge efficiency was 98.11%, and the total discharge energy was 29.334Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0067] Example 5 This embodiment 5 provides a high-rate electrode design, which differs from embodiment 1 only in that: =0.7. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.57. Porosity =0.21, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0068] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 98.10%, and the total discharge energy was 29.177Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0069] Example 6 This embodiment 6 provides a high-rate electrode design, which differs from embodiment 1 only in that: =0.6. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.5. Porosity =0.26, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0070] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 98.09%, and the total discharge energy was 28.995Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0071] Example 7 This embodiment 7 provides a high-rate electrode design, which differs from embodiment 1 only in that: =0.5. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this implementation, the adjusted compaction density of the electrode film layer is 3.54. Porosity =0.23, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0072] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 98.06%, and the total discharge energy was 28.587Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0073] Comparative Example 1 Comparative Example 1 provides a high-rate electrode design, which differs from Example 1 only in that: =0.4. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this comparison, the adjusted compaction density of the electrode film was 3.53. Porosity =0.22, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0074] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 98.06%, and the total discharge energy was 27.865Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0075] Comparative Example 2 Comparative Example 2 provides a high-rate electrode design, which differs from Example 1 only in that: =0.3. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this comparison, the adjusted electrode film compaction density was 3.56. Porosity =0.22, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0076] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The discharge efficiency was 95.96%, and the total discharge energy was 25.754Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0077] Comparative Example 3 Comparative Example 3 provides a high-rate electrode design, which differs from Example 1 only in that: =0.2. According to calculations, by adjusting the compaction density, tortuosity, and electrolyte formulation of the electrode, the following can be achieved: , and Meets the standards, specifically , and In this comparison, the adjusted electrode film compaction density was 3.58. Porosity =0.2, tortuosity Intrinsic conductivity of electrode film The intrinsic ionic conductivity of the electrolyte used Intrinsic lithium-ion diffusion coefficient of electrolyte All other conditions are the same as in Example 1.
[0078] The prepared electrodes were assembled into a full cell and tested at a 20C rate. The test time, voltage, and discharge energy were recorded. The capacity retention rate was obtained from the test. The percentage was 58.93%, and the total discharge energy was 14.516Wh. The voltage vs. capacity retention curves are shown below. Figure 1 The total discharge energy vs. time curve is shown in the figure. Figure 2 .
[0079] Effect Example Capacity retention test The discharge capacity test is performed according to the following steps: Charge at a constant current of 0.33C to the upper limit voltage of 4.2V, and charge at a constant voltage of 4.2V until the current is less than 0.02C; Let stand for 30 minutes; Discharge at 20C to the lower limit voltage of 2.5V, and record the discharge capacity. With energy; The above multipliers are based on Calculate the capacity retention rate. ,in For discharge capacity, For design capacity.
[0080] The design parameters and test results of Examples 1-7 and Comparative Examples 1-3 are shown in Table 1: Table 1 Figure 1 This is a graph showing the voltage versus capacity retention of the batteries obtained in Examples 1-7 and Comparative Example 3. The horizontal axis represents the battery's capacity retention rate (%), and the vertical axis represents the test voltage (V). Figure 2This is a graph showing the total discharge energy versus time for the batteries obtained in Examples 1-7 and Comparative Example 3. The horizontal axis represents time (s), and the vertical axis represents discharge energy (Wh). The data in Table 1, combined with the results from the examples, demonstrates that the steps and ratios were followed correctly. If the range is met, the electrode performance can meet the design goals, ensuring excellent capacity retention even at high rates for thick electrodes. The ratios shown in Comparative Examples 1-3... None of them are within a suitable range; the capacity retention rate and total discharge capacity cannot simultaneously meet the requirements. Compared to Example 1, Comparative Examples 1-3 show changes. As can be observed from the value of , the capacity retention rate and / or total discharge capacity decrease significantly, especially when When the ratio is too small, both capacity retention and total discharge energy decrease significantly, for example when At a value of 0.2, the capacity retention rate decreased by 40%, which completely fails to meet our design requirements. In summary, the design scheme of this application can effectively guide formulation optimization, improve efficiency to a certain extent, and reduce trial-and-error costs, specifically through matching... and This ensures that the electron transport capability matches the ion transport capability, enabling the electrode material to react synchronously and uniformly at high rates, and significantly improving the capacity retention of thick electrodes at high rates.
[0081] Although embodiments of this implementation have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this implementation, the scope of which is defined by the claims and their equivalents.
Claims
1. A lithium-ion battery electrode, comprising a current collector and a porous electrode film disposed on at least one surface of the current collector, characterized in that, The actual thickness of the porous electrode film is: The actual thickness satisfy ,in, This indicates the salt diffusion limit thickness of the porous electrode film. The ratio of the charge transport limit thickness of the porous electrode film to the total charge transport thickness is given by the two values. satisfy: .
2. The lithium-ion battery electrode according to claim 1, characterized in that, Salt diffusion limit thickness of porous electrode film Its expression is: ， in, This represents the effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film. , Describing Faraday constant , Indicates the lithium ion concentration in the electrolyte. , Indicates the lithium-ion transference number in the electrolyte. Indicates the active specific surface area 1 / m². Represents the exchange current density , Represents thermoelectric potential V -1 , Indicates the overpotential V; The charge transport limit thickness of the porous electrode film layer Its expression is: ， in, This represents the solid-phase effective electronic conductivity of the porous electrode film. , This indicates the effective liquid-phase ionic conductivity of the porous electrode film. .
3. The lithium-ion battery electrode according to claim 2, characterized in that, The following conditions must be met: a. The effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film ,in, Indicates the intrinsic lithium-ion diffusion coefficient of the electrolyte. , Indicates the porosity of the porous electrode. Indicates the tortuosity of the porous electrode; b. Solid-phase effective electronic conductivity of the porous electrode film ,in, Indicates the intrinsic conductivity of the porous electrode; c. Liquid-phase effective ionic conductivity of the porous electrode film ,in, This indicates the intrinsic ionic conductivity of the electrolyte.
4. The lithium-ion battery electrode according to claim 2, characterized in that, The thermoelectric potential ,in, Indicates the symmetry coefficient of the electrode electrochemical reaction. Represents the gas constant. It represents the thermodynamic temperature in K.
5. The lithium-ion battery electrode according to claim 2, characterized in that, After determining the target discharge rate And the preset thickness of the porous electrode film is The following relationship is satisfied: ， in, Indicates the overall effective conductivity of the electrodes ,and , The volumetric capacity density of the porous electrode film is indicated. ,Depend on Calculations show that This indicates the discharge specific capacity of the active material in the porous electrode film. , The true density of the active material is expressed in g / cm³. 3 , This indicates the discharge rate.
6. The lithium-ion battery electrode according to claim 5, characterized in that, The charge transport limit thickness of the porous electrode film layer Salt diffusion limit thickness of the porous electrode film ratio satisfy: 。 7. The lithium-ion battery electrode according to claim 6, characterized in that, The porous electrode film is a positive electrode film or a negative electrode film. The positive electrode film includes a positive electrode active material, which is a lithium-containing transition metal oxide and / or a polyanionic lithium-containing compound. The negative electrode film includes a negative electrode active material, which is a mixture of one or more of graphite, silicon-containing graphite, silicon oxide-containing graphite, and phosphorus-containing compounds.
8. A method for designing a lithium-ion battery electrode, characterized in that, Includes the following steps: S1. Determine the target discharge rate of the battery. and the preset thickness of the porous electrode film ; S2. Determine the charge transport limit thickness of the porous electrode film. Salt diffusion limit thickness of the porous electrode film ratio Satisfying 0.5≤ The thickness of the porous electrode film is required to be ≤1.
2. satisfy ; S3. Calculate the minimum target effective lithium-ion diffusion coefficient in the liquid phase possessed by the porous electrode film. Combined effective conductivity of the minimum target electrode Substitute according to Calculate the effective electronic conductivity of the target solid phase Target liquid phase effective ionic conductivity The range is 0.1-2 ; S4. Adjust the compaction density, tortuosity, and electrolyte formulation of the electrode to improve the actual effective lithium-ion diffusion coefficient in the liquid phase of the porous electrode film. Actual solid-phase effective electronic conductivity and actual effective ionic conductivity in liquid phase The target value in step S3 is satisfied.
9. The design method according to claim 8, characterized in that, In step S3, the minimum target liquid phase effective lithium-ion diffusion coefficient The calculation formula is as follows: ， in, Indicates the lithium-ion transference number in the electrolyte. This represents the volumetric capacity density of the porous electrode film. Denotes Faraday's constant. Indicates the lithium-ion concentration in the electrolyte; The minimum target electrode's overall effective conductivity The calculation formula is as follows: ， in, It represents thermoelectric potential.
10. A lithium-ion battery, characterized in that, This includes the lithium-ion battery electrode according to any one of claims 1-7 or the lithium-ion battery electrode obtained by the design method according to claim 8 or 9.