Construction method and simulation method of electrochemical model of lithium-ion battery

Abstract

The present invention discloses a method for constructing an electrochemical model of a lithium ion battery and a simulation method. In the process of constructing the electrochemical model, the diffusion process of lithium ions in an electrolyte, the diffusion process of lithium ions from the inside to the surface of an active material and from the surface to the inside, the potential distribution of the electrolyte, the potential distribution of the active material, the reaction process of lithium ion embedding and extraction, and the distribution state of the active material in a two-dimensional space are taken into consideration. That is, the electrochemical model introduces the mesoscopic morphology of a positive electrode and a negative electrode into the model, and refines the lithium ion exchange of a solid and a liquid to the boundary conditions, and sets the lithium ion exchange to occur at the solid-liquid interface. After the electrochemical model is used for simulation, the obtained simulation results are more consistent with the characteristics of the lithium ion battery itself, and the simulation results are more accurate and reliable, thereby providing a reliable reference for the subsequent analysis and application of lithium ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method for constructing and simulating an electrochemical model of a lithium-ion battery. Background Art

[0002] The electrochemical model of lithium-ion batteries is generally a P2D (Pseudo-two-dimensions) model, which simplifies the positive and negative electrodes and only considers the porosity and tortuosity of the positive and negative electrodes. As a result, the simulation results obtained after simulation based on the P2D electrochemical model are less accurate. Summary of the invention

[0003] The embodiment of the present invention provides a method for constructing an electrochemical model and a simulation method for a lithium-ion battery, which are used to construct a new electrochemical model. The electrochemical model takes into account the mesoscopic morphology of the positive electrode and the negative electrode, so that after simulation based on the electrochemical model, the accuracy of the simulation results can be effectively improved.

[0004] In a first aspect, an embodiment of the present invention provides a method for constructing an electrochemical model of a lithium-ion battery, wherein the lithium-ion battery comprises: a positive electrode, a negative electrode and an electrolyte; wherein the positive electrode and the negative electrode both comprise: a pole piece and an active material located on the surface of the pole piece; the construction method comprises:

[0005] Dividing the lithium-ion battery into regions according to the distribution state of the active material in the two-dimensional space;

[0006] According to the distribution state of the active material in the two-dimensional space, respectively determine the first diffusion process of the lithium ions in the electrolyte, the second diffusion process of the lithium ions from the interior to the surface of the active material and from the surface to the interior of the active material, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process of the lithium ions embedding and de-embedding from the surface of the active material;

[0007] An electrochemical model of the lithium-ion battery is constructed according to the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process.

[0008] In a second aspect, an embodiment of the present invention provides a simulation method, including:

[0009] According to the electrochemical model constructed by the construction method provided in the embodiment of the present invention, a simulation model of a lithium-ion battery is established using a simulation platform;

[0010] Using the simulation model, performing simulation according to input parameters to obtain simulation results;

[0011] Wherein, the input parameters include: the distribution state of the active material on the surface of the electrode in the lithium-ion battery in two-dimensional space.

[0012] The beneficial effects of the present invention are as follows:

[0013] The electrochemical model construction method and simulation method of the lithium ion battery provided by the embodiment of the present invention, in the process of constructing the electrochemical model, the first diffusion process of lithium ions in the electrolyte, the second diffusion process of lithium ions from the inside to the surface of the active material and from the surface to the inside, the potential distribution of the electrolyte, the potential distribution of the active material, the reaction process of lithium ion insertion and extraction, and the distribution state of the active material in the two-dimensional space are considered. That is, the electrochemical model introduces the mesoscopic morphology of the positive and negative electrodes into the model, and divides the lithium ion battery into regions according to the distribution state of the active material in the two-dimensional space, and then constructs an electrochemical model based on the mesoscopic morphology based on the divided regions; after simulating using the electrochemical model, the simulation results obtained are more in line with the characteristics of the lithium ion battery itself, and the simulation results are more accurate and reliable, so as to provide a reliable reference for the subsequent analysis and application of lithium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A flow chart of a method for constructing an electrochemical model of a lithium-ion battery provided in an embodiment of the present invention;

[0015] Figure 2 The distribution state of active materials in a lithium-ion battery provided in an embodiment of the present invention;

[0016] Figure 3 For Figure 2 Schematic diagram of the division of the corresponding area;

[0017] Figure 4 A flowchart of a simulation method provided in an embodiment of the present invention;

[0018] Figure 5 A scanning electron microscope image provided in an embodiment of the present invention;

[0019] Figure 6 A distribution diagram of liquid lithium ion concentration at different positions at different times provided in an embodiment of the present invention;

[0020] Figure 7 A distribution diagram of solid-phase lithium ion concentration at different positions at different times provided in an embodiment of the present invention;

[0021] Figure 8 A distribution diagram of the liquid phase potential at the end of charging provided in an embodiment of the present invention;

[0022] Fig. 9 A distribution diagram of the solid phase potential at the end of charging provided in an embodiment of the present invention;

[0023] Fig.10 This is a predicted charging curve of a lithium-ion battery provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings to describe in detail the specific implementation methods of the method for constructing the electrochemical model of the lithium-ion battery and the simulation method provided by the embodiments of the present invention. It should be noted that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] The embodiment of the present invention provides a method for constructing an electrochemical model of a lithium-ion battery, wherein the lithium-ion battery comprises: a positive electrode, a negative electrode and an electrolyte; wherein the positive electrode and the negative electrode both comprise: a pole piece and an active material located on the surface of the pole piece;

[0026] Of course, lithium-ion batteries may also include: a separator located between the positive electrode and the negative electrode;

[0027] like Figure 1 As shown, the construction method may include:

[0028] S101, dividing the lithium-ion battery into regions according to the distribution state of active materials in two-dimensional space;

[0029] Among them, the distribution state of active materials in two-dimensional space can be understood as: the mesoscopic morphology of the positive and negative electrode surfaces.

[0030] S102, according to the distribution state of the active material in the two-dimensional space, respectively determining a first diffusion process of lithium ions in the electrolyte, a second diffusion process of lithium ions from the interior to the surface of the active material and from the surface to the interior of the active material, a potential distribution of the electrolyte, a potential distribution of the active material, and a reaction process of lithium ions embedding and de-embedding from the surface of the active material;

[0031] S103, constructing an electrochemical model of the lithium-ion battery according to the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process.

[0032] Thus, in the process of constructing the electrochemical model, the first diffusion process of lithium ions in the electrolyte, the second diffusion process of lithium ions from the inside to the surface of the active material and from the surface to the inside, the potential distribution of the electrolyte, the potential distribution of the active material, the reaction process of lithium ion insertion and extraction, and the distribution state of the active material in two-dimensional space are considered. That is to say, the electrochemical model imports the mesoscopic morphology of the positive and negative electrodes into the model, and divides the lithium ion battery into regions according to the distribution state of the active material in two-dimensional space, and then constructs an electrochemical model based on the mesoscopic morphology based on the divided regions, refines the lithium ion exchange of solid and liquid to the boundary conditions, and sets the lithium ion exchange to occur at the solid-liquid interface; after simulation using the electrochemical model, the simulation results obtained are more in line with the characteristics of the lithium ion battery itself, and the simulation results are more accurate and reliable, so as to provide a reliable reference for the subsequent analysis and application of lithium ion batteries.

[0033] Optionally, in an embodiment of the present invention, when constructing an electrochemical model, it can be constructed according to Fick's law based on the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process.

[0034] Optionally, in an embodiment of the present invention, the first diffusion process includes: lithium ions diffusing in the electrolyte along the x direction and the y direction;

[0035] The second diffusion process includes: lithium ions diffuse from the inside of the active material to the surface and from the surface of the active material to the inside along the x direction and the y direction;

[0036] The potential distribution of the electrolyte includes: the potential distribution along the x direction and the y direction in the electrolyte;

[0037] The potential distribution of the active material includes: the potential distribution in the active material along the x direction and the y direction;

[0038] Among them, the x direction and the y direction constitute a two-dimensional space.

[0039] That is to say, in the embodiment of the present invention, whether it is the diffusion process of lithium ions or the potential distribution, both are aimed at the two directions of x and y, rather than one direction. Therefore, the electrochemical model is constructed based on the mesoscopic morphology of the positive and negative electrodes, thereby refining the lithium ion exchange between the solid and the liquid into the lithium ion exchange at the boundary conditions, and setting the lithium ion exchange to occur at the solid-liquid interface, so that the constructed electrochemical model is more in line with the actual situation.

[0040] Optionally, in an embodiment of the present invention, if Figure 3 As shown, the lithium-ion battery includes: two electrode regions (such as Q1n and Q1p), and a non-electrode region (such as Ω5);

[0041] The positive electrode is located in one of the electrode regions Q1p, and the negative electrode is located in the other electrode region Q1n;

[0042] The electrode region includes: a pole piece region (such as Ω1 and Ω9) and an active region (such as Ωn and Ωp); the pole piece is located in the pole piece region;

[0043] The active materials include: positive electrode active particles, negative electrode active particles, conductive glue and binder;

[0044] like Figure 3 As shown, the active region (such as Ωn) includes: a particle region Ω4 where the positive electrode active particles or the negative electrode active particles are located, a bonding region Ω2 where the conductive glue and the adhesive are located, and a spacing region Ω3.

[0045] In this way, the lithium-ion battery can be divided into multiple regions, and the electrode region can be subdivided, instead of simplifying the electrode region and not considering the more detailed structural characteristics or morphological features within the electrode region as in the prior art, so as to more deeply analyze the mesoscopic morphology of the positive and negative electrode surfaces, which is conducive to the subsequent construction of an electrochemical model based on the mesoscopic morphology.

[0046] Specifically, in the embodiment of the present invention, both the positive electrode and the negative electrode may include: a pole piece and an active material located on the surface thereof;

[0047] Among them, the pole piece can be understood as a current collector, a structure used to collect current;

[0048] The active materials may include: positive electrode active particles, negative electrode active particles, conductive glue and binder, wherein the binder can realize the bonding between the positive electrode active particles, the bonding between the positive electrode active particles and the pole piece, the bonding between the negative electrode active particles, and the bonding between the negative electrode active particles and the pole piece. The conductive glue can generally also play a certain bonding role and can also realize the conduction of electrons.

[0049] Specifically, in the embodiment of the present invention, the positive electrode plate may be but not limited to aluminum foil, the negative electrode plate may be but not limited to copper foil, the positive electrode active particles may be but not limited to spherical particles containing lithium compounds, and the negative electrode active particles may be but not limited to graphite;

[0050] The lithium-containing compounds may include: lithium manganese oxide, lithium iron phosphate and other lithium-containing compounds, which may be selected according to actual needs and are not limited here.

[0051] The division of regions is explained and illustrated below with reference to specific examples.

[0052] Combination Figure 2 and Figure 3 As shown, Figure 2 The distribution state of active materials in a lithium-ion battery in two-dimensional space is shown in Figure 2. Taking an active particle (including positive electrode active particles and negative electrode active particles) and a binder on the surface of the positive electrode and the negative electrode as an example, Figure 3 For Figure 2 Schematic diagram of the corresponding area division.

[0053] See also Figure 2 As shown, for the positive electrode: the positive electrode active particles are bonded to the surface of the electrode sheet (here called the positive electrode sheet) through a binder (which can also be a conductive glue, and the binder is used as an example for explanation here); for the negative electrode: the negative electrode active particles are bonded to the surface of the electrode sheet (here called the negative electrode sheet) through a binder.

[0054] Let me explain. Figure 2 The distribution of only part of the active material is shown in Figure 2 When the dashed line frame 1 is regarded as a periodic structure, a lithium-ion battery may include many such periodic structures.

[0055] At this time, for the division of regions, such as Figure 3 As shown, assuming that the left side of the figure is the negative pole and the right side is the positive pole, for the negative pole:

[0056] The particle area where the negative electrode active particles are located is Ω4, the bonding area where the binder is located is Ω2, the area in the active area other than the particle area and the bonding area is the spacing area, represented by Ω3, and the electrode area where the negative electrode sheet is located is located at Ω1;

[0057] For the positive electrode:

[0058] The particle area where the positive electrode active particles are located is Ω7, the bonding area where the binder is located is Ω8, the area in the active area other than the particle area and the bonding area is the spacing area, represented by Ω6, and the pole piece where the positive electrode sheet is located is Ω9;

[0059] For the diaphragm:

[0060] The separator is located in the non-electrode region and is represented by Ω5.

[0061] Accordingly, the boundary division can be carried out according to the division of the aforementioned regions. Assume Figure 3 When the left side is the negative pole and the right side is the positive pole, for the negative pole:

[0062] The boundary between the electrode area and the outside is Г2, the boundary between the bonding area and the electrode area, and the boundary between the bonding area and the particle area are Г3, the boundary between the particle area and the spacing area is Г5, the boundary between the spacing area and the electrode area is Г4, and the boundary between the spacing area and the non-electrode area is Г6;

[0063] For the positive electrode:

[0064] The boundary between the electrode area and the outside is Г11, the boundary between the bonding area and the electrode area, and the boundary between the bonding area and the particle area are Г10, the boundary between the particle area and the spacing area is Г8, the boundary between the spacing area and the electrode area is Г9, and the boundary between the spacing area and the non-electrode area is Г7;

[0065] The boundary between adjacent periodic structures is Г1.

[0066] To avoid confusion, Figure 3 Γ1 to Γ11 are not shown.

[0067] Of course, the above division of regions and boundaries is only an embodiment, and the division of regions and boundaries in the embodiments of the present invention is not limited thereto, and can be divided according to actual conditions, which is not limited here.

[0068] Optionally, in an embodiment of the present invention, when the electrochemical model includes: a liquid-phase lithium ion diffusion model, a solid-phase lithium ion diffusion model, a liquid-phase potential model, a solid-phase potential model, and a BV (Butler–Volmer) equation, an electrochemical model of a lithium-ion battery is constructed according to the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process, specifically including:

[0069] According to the divided regions and the first diffusion process, a liquid phase lithium ion diffusion model is constructed;

[0070] According to the divided regions and the second diffusion process, a solid phase lithium ion diffusion model is constructed;

[0071] According to the potential distribution of the divided regions and the electrolyte, a liquid phase potential model is constructed;

[0072] Construct a solid phase potential model based on the potential distribution of each divided area and active material;

[0073] The BV equation is constructed based on the divided regions and reaction processes.

[0074] In this way, the electrochemical model of lithium-ion batteries can be represented by the above five models, so that the performance of lithium-ion batteries can be described from multiple aspects.

[0075] The five models mentioned above are explained below.

[0076] 1. Liquid phase lithium ion diffusion model.

[0077] Optionally, in an embodiment of the present invention, the lithium-ion battery further comprises: a separator located between the negative electrode and the positive electrode;

[0078] According to the divided regions and the first diffusion process, a liquid phase lithium ion diffusion model is constructed, which specifically includes:

[0079] The following formula is used to determine the lithium ion concentration at any location in the negative electrode at any time:

[0080]

[0081] The following formula is used to determine the lithium ion concentration at any location in the separator at any time:

[0082]

[0083] The following formula is used to determine the lithium ion concentration at any location in the positive electrode at any time:

[0084]

[0085] The first boundary condition is determined using the following formula:

[0086]

[0087]

[0088]

[0089]

[0090] The continuity condition is determined using the following formula:

[0091]

[0092]

[0093] Among them, C e,n Indicates the lithium ion concentration in the electrolyte near the negative electrode, D e represents the liquid phase diffusion coefficient, ε s Denotes the porosity of the diaphragm, D e,s eff is the effective diffusion coefficient of the liquid phase at the diaphragm, C e,p Indicates the lithium ion concentration in the electrolyte near the positive electrode, C e,s represents the lithium ion concentration in the electrolyte near the separator, j n represents the ion flux at the negative electrode, j pRepresents the ion flux of the positive electrode, t represents any time, n represents the negative electrode, p represents the positive electrode, c represents the lithium ion concentration, D represents the diffusion coefficient, eff represents the effective diffusion coefficient, s represents the separator, e represents the electrolyte, x and y represent the two directions that constitute the two-dimensional space, Ω3 represents the spacing area corresponding to the negative electrode, Ω5 represents the non-electrode area, Ω6 represents the spacing area corresponding to the positive electrode, Г9 represents the boundary between the spacing area corresponding to the positive electrode and the electrode area corresponding to the positive electrode, Г4 represents the boundary between the spacing area corresponding to the negative electrode and the electrode area corresponding to the negative electrode, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the spacing area corresponding to the positive electrode, Г6 represents the boundary between the spacing area corresponding to the negative electrode and the non-electrode area, and Г7 represents the boundary between the spacing area corresponding to the positive electrode and the non-electrode area.

[0094] Specifically, ion flux can be understood as the number of lithium ions passing through a unit area per unit time.

[0095] Specifically, the liquid-phase lithium ion diffusion model can be used to describe the diffusion process of lithium ions in the electrolyte, in the gaps of the separator, and in the gaps of the active particles, that is, the lithium ion concentration at each position (x, y) at each time (t).

[0096] To illustrate one point, optionally, in the electrochemical model constructed in the embodiment of the present invention, lithium ions diffuse along both the x and y directions, so the surface integral is used in the above formula.

[0097] Moreover, the first boundary condition in the model is that there is no liquid-phase lithium ion diffusion at the contact surface between the electrode and the active material, and the ion flux is 0; at the same time, on the surface of the active particles (including positive electrode active particles and negative electrode active particles), when the concentration of lithium ions entering and leaving the active particles is the same, the ion concentration inside and outside the active particles is in dynamic equilibrium; under the continuity condition, since there is no lithium ion accumulation at the diaphragm, the concentration of lithium ions entering and leaving the diaphragm should be the same.

[0098] 2. Solid phase lithium ion diffusion model.

[0099] According to the divided regions and the second diffusion process, a solid phase lithium ion diffusion model is constructed, which specifically includes:

[0100] The following formula is used to determine the lithium ion concentration at any location in the negative electrode at any time:

[0101]

[0102] The following formula is used to determine the lithium ion concentration at any location in the positive electrode at any time:

[0103]

[0104] The second boundary condition is determined using the following formula:

[0105]

[0106]

[0107] Among them, C so,n represents the lithium ion concentration in the negative electrode, D so,n represents the solid phase diffusion coefficient in the negative electrode, C so,p represents the lithium ion concentration in the positive electrode, D so,p represents the solid phase diffusion coefficient in the positive electrode, j n represents the ion flux at the negative electrode, j p Represents the ion flux of the positive electrode, so represents the solid phase, t represents any time, n represents the negative electrode, p represents the positive electrode, c represents the lithium ion concentration, D represents the diffusion coefficient, x and y represent the two directions that constitute the two-dimensional space, Ω4 represents the particle area corresponding to the negative electrode active particles, Ω7 represents the particle area corresponding to the positive electrode active particles, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the spacing area corresponding to the positive electrode, and the solid phase is: positive electrode or negative electrode.

[0108] Specifically, the solid-phase lithium ion diffusion model can be used to describe the diffusion process of lithium ions from the interior to the surface of the active material and from the surface to the interior, that is, the lithium ion concentration at each position (x, y) at each time (t).

[0109] To clarify, since there is no active material at the diaphragm, there is no solid phase diffusion at the diaphragm.

[0110] Furthermore, in the model, the second boundary conditions include: the ion flux of the positive electrode and the ion flux of the negative electrode;

[0111] The ion flux of the positive electrode is the flux of lithium ions on the surface of the positive electrode active particles, and the ion flux of the negative electrode is the flux of lithium ions on the surface of the negative electrode active particles.

[0112] 3. Liquid phase potential model.

[0113] Optionally, in an embodiment of the present invention, the lithium-ion battery further comprises: a separator located between the negative electrode and the positive electrode;

[0114] According to the potential distribution of each divided area and electrolyte, a liquid phase potential model is constructed, which includes:

[0115] Use the following formula to determine the potential at any location in the negative electrode at any time:

[0116]

[0117] The potential at any location in the diaphragm at any time is determined using the following formula:

[0118]

[0119] Use the following formula to determine the potential at any location in the positive electrode at any time:

[0120]

[0121] The third boundary condition is determined using the following formula:

[0122]

[0123]

[0124]

[0125] Among them, K e represents the conductivity of the electrolyte, represents the effective conductivity of the electrolyte at the diaphragm, Фe represents the potential of the electrolyte, C e,n Indicates the lithium ion concentration in the electrolyte at the negative electrode, C e,s It represents the lithium ion concentration in the electrolyte at the membrane, C e,p represents the lithium ion concentration in the electrolyte at the positive electrode, j n represents the ion flux at the negative electrode, j p represents the ion flux of the positive electrode, x and y represent the two directions of the two-dimensional space, e represents the electrolyte, R represents the particle radius, T represents the temperature, and t 0 represents the mobility of lithium ions, F represents the Faraday constant, eff represents the effective diffusion coefficient, s represents the separator, n represents the negative electrode, p represents the positive electrode, Ω3 represents the spacing area corresponding to the negative electrode, Ω5 represents the non-electrode area, Ω6 represents the spacing area corresponding to the positive electrode, Г4 represents the boundary between the spacing area corresponding to the negative electrode and the electrode area corresponding to the negative electrode, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the spacing area corresponding to the positive electrode, Г9 represents the boundary between the spacing area corresponding to the positive electrode and the electrode area corresponding to the positive electrode.

[0126] Specifically, the liquid phase potential model can be used to describe the change of the potential in the electrolyte over time, that is, the potential at each position (x, y) at each moment (t).

[0127] 4. Solid phase potential model.

[0128] Optionally, in an embodiment of the present invention, a solid phase potential model is constructed according to the potential distribution of each divided region and active material, specifically including:

[0129] Use the following formula to determine the potential at any location in the negative electrode at any time:

[0130]

[0131] Use the following formula to determine the potential at any location in the positive electrode at any time:

[0132]

[0133] Use the following formula to determine the potential at any location in the negative electrode at any time:

[0134]

[0135] Use the following formula to determine the potential at any location in the positive electrode at any time:

[0136]

[0137] Use the following formula to determine the potential at any location in the conductive glue at any time:

[0138]

[0139] The constraints are determined using the following formula:

[0140] Φ SO | (x，y)∈Γ2 =0

[0141] The fourth boundary condition is determined using the following formula:

[0142]

[0143]

[0144]

[0145] Among them, Ф so represents the electric potential of the solid phase, σ n represents the conductivity of the negative electrode active particles, σ p represents the conductivity of the positive electrode active particles, σ n,col Represents the conductivity of the negative electrode, σ p,col Represents the conductivity of the positive electrode, σ gl Indicates the conductivity of the conductive glue and / or adhesive, j n represents the ion flux at the negative electrode, j prepresents the ion flux of the positive electrode, x and y represent the two directions that constitute the two-dimensional space, n represents the negative electrode, s represents the diaphragm, p represents the positive electrode, col represents the electrode, gl represents the binder and / or conductive glue, I represents the current, A represents the area of ​​the electrode in the positive electrode, F represents the Faraday constant, Г2 represents the boundary between the electrode area corresponding to the negative electrode and the outside world, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the interval area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the interval area corresponding to the positive electrode, Г11 represents the boundary between the electrode area corresponding to the positive electrode and the outside world, and the solid phase is: positive electrode or negative electrode.

[0146] Specifically, the solid phase potential includes the internal and surface potentials of the active material, and the potentials of the conductive glue and the binder.

[0147] Specifically, the solid phase potential model can be used to describe the change of the solid phase potential over time, that is, the potential at each position (x, y) at each moment (t).

[0148] It should be noted that in this model, the solid phase potential not only considers the internal and surface potential of the active material, but also needs to consider the electron distribution of the electrode, binder and conductive glue.

[0149] 5.BV equation.

[0150] Optionally, in an embodiment of the present invention, a BV equation is constructed according to the divided regions and reaction processes, specifically including:

[0151] The solid-liquid interface of the negative electrode was determined using the following formula:

[0152]

[0153] The solid-liquid interface of the positive electrode is determined using the following formula:

[0154]

[0155] Among them, C so,n,max represents the maximum solid phase lithium ion concentration in the negative electrode, C so,n,surf represents the solid surface lithium ion concentration in the negative electrode, C n represents the lithium ion concentration of the negative electrode, j n represents the ion flux at the negative electrode, C so,p,max represents the maximum solid phase lithium ion concentration in the positive electrode, C so,p,surf represents the solid surface lithium ion concentration in the positive electrode, C p represents the lithium ion concentration of the positive electrode, j prepresents the ion flux of the positive electrode, n represents the negative electrode, so represents the solid phase, p represents the positive electrode, Г5 represents the boundary between the particle region corresponding to the negative electrode active particle and the interval region corresponding to the negative electrode, Г8 represents the boundary between the particle region corresponding to the positive electrode active particle and the interval region corresponding to the positive electrode, F represents the Faraday constant, R represents the particle radius, T represents the temperature, η n represents the overpotential on the surface of the negative electrode active particles, η p represents the overpotential on the surface of the positive electrode active particles, k n represents the electrochemical reaction constant of the negative electrode, k p Represents the electrochemical reaction constant of the positive electrode.

[0156] Specifically, in the embodiment of the present invention, η in the above formula is n and η p It can be specifically:

[0157] η n =Eneg(soc2)=85.177×(soc2) 6 -285.63×(soc2) 5 +373.12×(soc2) 4 -239.19×(soc2) 3 +77.716×(soc2) 2 -11.938×(soc2)+0.797;

[0158] Where, soc2=c so,n,surf / c so,n,max ;

[0159] η p =Epos(soc1)=7.7041×(soc1) 6 -6.9969×(soc1) 5 +10.43×(soc1) 4 -15.906×(soc1) 3 +8.0493×(soc1) 2 -3.0494×(soc1)+4.6155;

[0160] Where, soc1=c so,p,surf / c so,p,max .

[0161] Specifically, the above BV equation can be used to describe the relationship between current and voltage in electrochemical reactions. Since the electrochemical reaction of lithium-ion batteries is a process in which lithium ions are embedded from the liquid phase to the solid phase, or from the solid phase to the liquid phase, it can serve as a bridge to connect the transmission of lithium ions between the solid phase and the liquid phase and the changes in current and voltage.

[0162] It should be emphasized that, in the embodiment of the present invention, the difference from the traditional P2D model is that the traditional P2D model adopts a porous electrode model. Although the model has both liquid and solid components, it only sets the material exchange of lithium ions in the source term of the partial differential equation, and the material exchange of lithium ions here is a general concept.

[0163] The electrochemical model provided by the embodiment of the present invention takes into account the mesoscopic morphology of the positive electrode and the negative electrode, and imports the mesoscopic morphology into the model, divides the mesoscopic morphology into regions according to the formulated strategy, assigns corresponding control equations to different regions, and refines the lithium ion exchange of solids and liquids into lithium ion exchange at boundary conditions, thereby improving the accuracy and authenticity of the constructed electrochemical model.

[0164] Based on the same inventive concept, an embodiment of the present invention provides a simulation method, such as Figure 4 As shown, it may include:

[0165] S401, using a simulation platform to establish a simulation model of a lithium-ion battery according to the electrochemical model constructed by the construction method provided in the embodiment of the present invention;

[0166] S402, using a simulation model, performing simulation according to input parameters to obtain simulation results; wherein the input parameters include: the distribution state of active materials on the surface of the electrode in the lithium-ion battery in two-dimensional space.

[0167] In this way, after simulation according to the electrochemical model constructed above, the simulation results obtained can be more accurate, reliable, and closer to the actual situation of the lithium-ion battery, thereby providing a reliable reference value for the subsequent analysis and application of lithium-ion batteries.

[0168] Optionally, in the embodiment of the present invention, the distribution state of the active material in the two-dimensional space can be artificially designed (such as Figure 2 as shown), or scanning electron microscopy images (such as Figure 5 shown).

[0169] Among them, Figure 5 In the figure, (a) is a scanning electron microscope image obtained after the test, (b) is a schematic diagram of the edge determined after learning the scanning electron microscope image after the test, and (c) is a schematic diagram of the negative electrode active particles, positive electrode active particles and binder in the determined scanning electron microscope image.

[0170] In this way, the distribution state of the active material can be selected according to actual needs to meet the needs of different application scenarios.

[0171] Optionally, in the embodiment of the present invention, the simulation platform may be, but is not limited to, Comsol software, and may also be other platforms that can implement this function, which is not limited here.

[0172] Optionally, in an embodiment of the present invention, the simulation results may include: a charge and discharge curve of a lithium-ion battery, a solid phase potential distribution diagram, a liquid phase potential distribution diagram, a solid phase lithium ion concentration distribution diagram, and a liquid phase lithium ion concentration distribution diagram.

[0173] The following is an explanation based on specific simulation results.

[0174] by Figure 2 The distribution state of the active material in two-dimensional space is shown as an example for explanation, but in actual situations it is not limited to Figure 2 The distribution state of active materials in two-dimensional space is shown.

[0175] Combination Figure 6 As shown, the figure is a distribution diagram of liquid lithium ion concentration at different positions at different times, where the left side of the figure is the negative electrode and the right side of the figure is the positive electrode; it can be found that:

[0176] This figure shows the change in lithium ion concentration in the electrolyte; the change in liquid phase lithium ion concentration is a rapid process. At the initial moment, lithium ions begin to be generated in the electrolyte around the positive electrode active particles and the negative electrode active particles, causing the lithium ion concentration to begin to change; and within 20 seconds, the lithium ion concentration changes to a uniform gradient from the positive electrode to the negative electrode.

[0177] Combination Figure 7 As shown, this figure is a distribution diagram of solid phase lithium ion concentration at different positions at different times, where the left side of the figure is the negative electrode and the right side of the figure is the positive electrode; it can be found that:

[0178] This figure shows the change in lithium ion concentration from the inside to the surface of the active particles and from the surface to the inside, so the change process is bidirectional; among them, the change in solid-phase lithium ion concentration is a slow process, and the lithium ion concentration distribution gradient in the active particles is changing from beginning to end. During the charging process, the concentration on the surface of the negative electrode active particles is higher than that in the center, and the concentration on the surface of the positive electrode active particles is lower than that in the center.

[0179] Combination Figure 8 As shown in the figure, this figure is the distribution diagram of the liquid phase potential at the end of charging, in which the left side of the figure is the negative electrode and the right side of the figure is the positive electrode; and the liquid phase potential distribution is also a fast process. Almost at the beginning of charging, the liquid phase potential has established its uniform TV distribution.

[0180] Combination Fig. 9As shown in the figure, this figure is a distribution diagram of the solid phase potential at the end of charging, wherein the left side of the figure is the negative electrode and the right side of the figure is the positive electrode; and, since the electrical conductivity of the solid phase is relatively high, the potential distribution of the solid is not obvious. At the end of charging, the positive electrode potential is about 4.5V and the negative electrode potential is about 0.2V.

[0181] Combination Fig.10 As shown in the figure, this figure is the charging curve of the lithium-ion battery predicted by the above simulation method, wherein, since the negative electrode has been constrained, the potential is 0, and the potential change of the positive electrode is the voltage output of the entire battery. By sampling the voltage at different times, the charging curve of the lithium-ion battery can be obtained.

[0182] Furthermore, through the above simulation results, a structure-activity relationship between the distribution state and performance of an active material in two-dimensional space can be constructed, so that the performance of lithium-ion batteries can be artificially controlled based on the structure-activity relationship.

[0183] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for constructing an electrochemical model of a lithium-ion battery, characterized in that: The lithium-ion battery comprises: a positive electrode, a negative electrode and an electrolyte; wherein the positive electrode and the negative electrode both comprise: a pole piece and an active material located on the surface of the pole piece; the construction method comprises: Dividing the lithium-ion battery into regions according to the distribution state of the active material in the two-dimensional space; According to the distribution state of the active material in the two-dimensional space, respectively determine the first diffusion process of the lithium ions in the electrolyte, the second diffusion process of the lithium ions from the interior to the surface of the active material and from the surface to the interior of the active material, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process of the lithium ions embedding and de-embedding from the surface of the active material; constructing an electrochemical model of the lithium-ion battery according to the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process; The divided areas include: two electrode areas and a non-electrode area; the positive electrode is located in one of the electrode areas, and the negative electrode is located in the other electrode area; the electrode area includes: a pole piece area and an active area; the pole piece is located in the pole piece area; the active material includes: positive electrode active particles, negative electrode active particles, conductive glue and binder; the active area includes: a particle area where the positive electrode active particles or the negative electrode active particles are located, a bonding area where the conductive glue and the binder are located, and a spacing area; The distribution state of the active material in two-dimensional space is: the mesoscopic morphology of the surface of the positive electrode and the negative electrode.

2. The construction method according to claim 1, characterized in that: The first diffusion process includes: the lithium ions diffuse in the electrolyte along the x direction and the y direction; The second diffusion process includes: the lithium ions diffuse from the interior to the surface of the active material and from the surface to the interior of the active material along the x direction and the y direction; The potential distribution of the electrolyte includes: the potential distribution in the electrolyte along the x direction and the y direction; The potential distribution of the active material includes: the potential distribution in the active material along the x direction and the y direction; The x direction and the y direction constitute the two-dimensional space.

3. The construction method according to claim 1 or 2, characterized in that: When the electrochemical model includes: a liquid-phase lithium ion diffusion model, a solid-phase lithium ion diffusion model, a liquid-phase potential model, a solid-phase potential model, and a BV equation, the electrochemical model of the lithium-ion battery is constructed according to the divided regions, the first diffusion process, the second diffusion process, the potential distribution of the electrolyte, the potential distribution of the active material, and the reaction process, specifically including: Constructing the liquid-phase lithium ion diffusion model according to the divided regions and the first diffusion process; Constructing the solid-phase lithium ion diffusion model according to the divided regions and the second diffusion process; Constructing the liquid phase potential model according to the divided regions and the potential distribution of the electrolyte; constructing the solid phase potential model according to the divided regions and the potential distribution of the active material; The BV equation is constructed according to the divided regions and the reaction process.

4. The construction method according to claim 3, characterized in that: The lithium-ion battery further comprises: a separator located between the negative electrode and the positive electrode; According to the divided regions and the first diffusion process, the liquid phase lithium ion diffusion model is constructed, specifically including: The lithium ion concentration at any position in the negative electrode at any time is determined using the following formula: The lithium ion concentration at any position in the diaphragm at any time is determined using the following formula: The lithium ion concentration at any position in the positive electrode at any time is determined using the following formula: The first boundary condition is determined using the following formula: The continuity condition is determined using the following formula: Among them, C e,n represents the lithium ion concentration in the electrolyte near the negative electrode, D e represents the liquid phase diffusion coefficient, ε s represents the porosity of the diaphragm, D e,s eff represents the effective diffusion coefficient of the liquid phase at the diaphragm, C e,p represents the lithium ion concentration in the electrolyte near the positive electrode, C e,s represents the lithium ion concentration in the electrolyte near the separator, j n represents the ion flux of the negative electrode, j p represents the ion flux of the positive electrode, t represents any time, n represents the negative electrode, p represents the positive electrode, c represents the lithium ion concentration, D represents the diffusion coefficient, eff represents the effective diffusion coefficient, s represents the separator, e represents the electrolyte, x and y represent the two directions constituting the two-dimensional space, Ω3 represents the spacing area corresponding to the negative electrode, Ω5 represents the non-electrode area, Ω6 represents the spacing area corresponding to the positive electrode, Г9 represents the boundary between the spacing area corresponding to the positive electrode and the electrode area corresponding to the positive electrode, Г4 represents the boundary between the spacing area corresponding to the negative electrode and the electrode area corresponding to the negative electrode, Г5 represents the boundary between the particle area corresponding to the negative electrode active particle and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particle and the spacing area corresponding to the positive electrode, Г6 represents the boundary between the spacing area corresponding to the negative electrode and the non-electrode area, and Г7 represents the boundary between the spacing area corresponding to the positive electrode and the non-electrode area.

5. The construction method according to claim 3, characterized in that: According to the divided regions and the second diffusion process, the solid phase lithium ion diffusion model is constructed, which specifically includes: The lithium ion concentration at any position in the negative electrode at any time is determined using the following formula: The lithium ion concentration at any position in the positive electrode at any time is determined using the following formula: The second boundary condition is determined using the following formula: Among them, C so,n represents the lithium ion concentration in the negative electrode, D so,n represents the solid phase diffusion coefficient in the negative electrode, C so,p represents the lithium ion concentration in the positive electrode, D so,p represents the solid phase diffusion coefficient in the positive electrode, j n represents the ion flux of the negative electrode, j p Represents the ion flux of the positive electrode, so represents the solid phase, t represents any time, n represents the negative electrode, p represents the positive electrode, c represents the lithium ion concentration, D represents the diffusion coefficient, x and y represent the two directions constituting the two-dimensional space, Ω4 represents the particle area corresponding to the negative electrode active particles, Ω7 represents the particle area corresponding to the positive electrode active particles, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the spacing area corresponding to the positive electrode, and the solid phase is: the positive electrode or the negative electrode.

6. The construction method according to claim 3, characterized in that: The lithium-ion battery further comprises: a separator located between the negative electrode and the positive electrode; According to the divided regions and the potential distribution of the electrolyte, the liquid phase potential model is constructed, which specifically includes: The potential at any position in the negative electrode at any time is determined using the following formula: The potential at any location in the diaphragm at any time is determined using the following formula: The potential at any position in the positive electrode at any time is determined using the following formula: The third boundary condition is determined using the following formula: Among them, K e represents the conductivity of the electrolyte, represents the effective conductivity of the electrolyte at the membrane, Фe represents the potential of the electrolyte, C e,n represents the lithium ion concentration in the electrolyte at the negative electrode, C e,s represents the lithium ion concentration in the electrolyte where the separator is wetted, C e,p represents the lithium ion concentration in the electrolyte at the positive electrode, j n represents the ion flux of the negative electrode, j p represents the ion flux of the positive electrode, x and y represent the two directions constituting the two-dimensional space, e represents the electrolyte, R represents the particle radius, T represents the temperature, t0 represents the mobility of the lithium ions, F represents the Faraday constant, eff represents the effective diffusion coefficient, s represents the separator, n represents the negative electrode, p represents the positive electrode, Ω3 represents the spacing area corresponding to the negative electrode, Ω5 represents the non-electrode area, Ω6 represents the spacing area corresponding to the positive electrode, Г4 represents the boundary between the spacing area corresponding to the negative electrode and the pole piece area corresponding to the negative electrode, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacing area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the spacing area corresponding to the positive electrode, and Г9 represents the boundary between the spacing area corresponding to the positive electrode and the pole piece area corresponding to the positive electrode.

7. The construction method according to claim 3, characterized in that: The lithium-ion battery further comprises: a separator located between the negative electrode and the positive electrode; According to the divided regions and the potential distribution of the active material, the solid phase potential model is constructed, which specifically includes: The potential at any position in the negative electrode at any time is determined using the following formula: The potential at any position in the positive electrode at any time is determined using the following formula: The following formula is used to determine the potential at any position in the electrode sheet of the negative electrode at any time: The following formula is used to determine the potential at any position in the positive electrode at any time: The following formula is used to determine the potential at any position in the conductive glue at any time: The constraints are determined using the following formula: Φso|(x,y)∈Γ2=0 The fourth boundary condition is determined using the following formula: Among them, Ф so represents the electric potential of the solid phase, σ n represents the conductivity of the negative electrode active particles, σ p represents the conductivity of the positive electrode active particles, σ n,col represents the conductivity of the electrode in the negative electrode, σ p,col represents the conductivity of the electrode in the positive electrode, σ gl represents the conductivity of the conductive glue and / or the adhesive, j n represents the ion flux of the negative electrode, j p represents the ion flux of the positive electrode, x and y represent the two directions constituting the two-dimensional space, n represents the negative electrode, s represents the separator, p represents the positive electrode, col represents the pole piece, gl represents the binder and / or the conductive glue, I represents the current, A represents the area of ​​the pole piece in the positive electrode, F represents the Faraday constant, Г2 represents the boundary between the pole piece area corresponding to the negative electrode and the outside world, Г5 represents the boundary between the particle area corresponding to the negative electrode active particles and the spacer area corresponding to the negative electrode, Г8 represents the boundary between the particle area corresponding to the positive electrode active particles and the positive electrode The boundary of the corresponding spacing area, Г11 represents the boundary between the pole piece area corresponding to the positive electrode and the outside world, and the solid phase is: the positive electrode or the negative electrode; Ω4 represents the particle area corresponding to the negative electrode active particles, Ω7 represents the particle area corresponding to the positive electrode active particles, Ω2 represents the bonding area where the conductive glue and / or the binder in the negative electrode are located, Ω8 represents the bonding area where the conductive glue and / or the binder in the positive electrode are located, Ω1 represents the pole piece area where the negative electrode sheet in the negative electrode is located, and Ω9 represents the pole piece area where the positive electrode sheet in the positive electrode is located.

8. The construction method according to claim 3, characterized in that: According to the divided regions and the reaction process, the BV equation is constructed, which specifically includes: The solid-liquid interface of the negative electrode is determined using the following formula: The solid-liquid interface of the positive electrode is determined using the following formula: Among them, C so,n,max represents the maximum solid phase lithium ion concentration in the negative electrode, C so,n,surf represents the solid surface lithium ion concentration in the negative electrode, C n represents the lithium ion concentration of the negative electrode, j n represents the ion flux of the negative electrode, C so,p,max represents the maximum solid phase lithium ion concentration in the positive electrode, C so,p,surf represents the solid surface lithium ion concentration in the positive electrode, C p represents the lithium ion concentration of the positive electrode, j p represents the ion flux of the positive electrode, n represents the negative electrode, so represents the solid phase, p represents the positive electrode, F represents the Faraday constant, R represents the particle radius, T represents the temperature, η n represents the overpotential on the surface of the negative electrode active particles, η p represents the overpotential on the surface of the positive electrode active particles, k n represents the electrochemical reaction constant of the negative electrode, k p represents the electrochemical reaction constant of the positive electrode.

9. A simulation method, characterized in that: include: The electrochemical model constructed by the construction method according to any one of claims 1 to 8 is used to establish a simulation model of a lithium-ion battery using a simulation platform; Using the simulation model, performing simulation according to input parameters to obtain simulation results; Wherein, the input parameters include: the distribution state of the active material on the surface of the electrode in the lithium-ion battery in two-dimensional space.

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