CN110096774A - Mechanics impacts the emulation mode of lower electrolytic solution for super capacitor ion redistribution effect - Google Patents

Abstract

The invention discloses a method for simulating the ion redistribution effect of a supercapacitor electrolyte under mechanical impact. The method comprises the following steps: establishing an energy storage kinetic model of a supercapacitor; The migration and redistribution model of liquid ions is used to form a supercapacitor-based energy storage-shock sensitive coupling model system; the finite element software is used to simulate and calculate the energy storage-shock sensitive coupling model system to realize the supercapacitor electrolyte ion under mechanical impact. Efficient simulation of redistribution effects. This method can numerically calculate the change of the ion concentration of the electrolyte and the output voltage of the supercapacitor during the impact process, and can also scan the important working parameters of the capacitor to analyze its influence on the significance of the ion redistribution effect, which can effectively promote the study of The suppression or enhancement of the mechanical sensitivity effect of the supercapacitor meets its application requirements in different working environments.

Description

Simulation Method of Electrolyte Ion Redistribution Effect in Supercapacitor Under Mechanical Shock

technical field

The invention relates to the technical field of supercapacitors, in particular to a method for simulating the redistribution effect of electrolyte ions in a supercapacitor under mechanical impact.

Background technique

Supercapacitor is a widely used electrochemical energy storage device. It realizes energy storage and release through two mechanisms of electric double layer effect and Faraday reaction. It has the advantages of large capacity density, good high and low temperature performance, and long cycle life. It is widely used in fields such as electric vehicles, industrial detection and wearable electronic devices.

Modeling and simulation methods play an important role in the design and development of supercapacitors. Numerical calculations can be performed through parameter sweeps to optimize the design of each main design parameter, and partially replace the tedious experimental tests required in traditional design methods. However, the supercapacitor modeling and simulation methods in the related art only consider their electrochemical characteristics at normal temperature and pressure, and ignore the interference effects of environmental factors such as temperature and pressure, which limits the practical application of such simulation methods .

In fact, with the gradual application of supercapacitors in some industrial detection fields, it is inevitable that they will be subjected to external mechanical impacts under working conditions. The liquid electrolyte is stored inside the supercapacitor, which has an ion redistribution effect under the impact. Therefore, there is an urgent need for a new simulation method to realize the effective simulation of the ion redistribution effect of the supercapacitor electrolyte under mechanical impact.

Contents of the invention

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

For this reason, the purpose of the present invention is to propose a simulation method of the ion redistribution effect of the supercapacitor electrolyte under mechanical impact, the method is specifically realized by the comsol simulation software platform, and is compatible with the matlab simulation platform, and has the feasibility of being easy to transplant and expand sex.

In order to achieve the above object, the present invention proposes a simulation method for the ion redistribution effect of the supercapacitor electrolyte, comprising the following steps: establishing an energy storage kinetic model of the supercapacitor; The migration and redistribution model of liquid ions to form a supercapacitor-based energy storage-shock sensitive coupling model system; use finite element software to perform simulation calculations on the energy storage-shock sensitive coupling model system to realize supercapacitor electrolysis under mechanical impact Efficient simulation of liquid ion redistribution effects.

The simulation method of the ion redistribution effect of the supercapacitor electrolyte under the mechanical impact of the embodiment of the present invention describes the generation mechanism of the unbalanced ion concentration of the electrolyte in the charging and discharging process of the supercapacitor and the ion concentration redistribution mechanism caused by the mechanical impact , and considering the influence of the ion concentration redistribution effect on the electrochemical reaction of the supercapacitor, it is realized through the COMSOL simulation software platform, and is compatible with the matlab simulation platform, which is easy to transplant and expand; and then can realize the mechanical impact process Dynamic simulation of electrolyte ion redistribution effect in supercapacitors, including accurate simulation calculation of electrolyte ion concentration and device output voltage; can scan device operating parameters such as discharge current, and analyze its influence on supercapacitor mechanical shock sensitive characteristics The law of influence; the parameters of the discharge degree at the time of impact can be scanned to analyze its influence law on the mechanical shock sensitive characteristics of the supercapacitor.

In addition, the simulation method for the ion redistribution effect of the supercapacitor electrolyte under mechanical impact according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

Further, in an embodiment of the present invention, the energy storage kinetic model includes an electric double layer effect model and a Faradaic reaction model.

Further, in one embodiment of the present invention, the energy storage-shock sensitive coupling model system includes the electrode kinetic model of the electric double layer effect, the electrode kinetic model of the Faraday reaction, the ion diffusion model in the electrolyte, and the mechanical Electrolyte ion redistribution model under shock.

Further, in one embodiment of the present invention, the energy storage kinetic model generates and stores energy through the highly reversible redox reaction between the electrode active material and the electrolyte material, so that the charge transfer occurs, wherein, The Faradaic reaction model described above dominates energy storage.

Further, in one embodiment of the present invention, the electric double layer effect model is corrected by Faraday current through the energy storage dynamics model, so that the electric potential field and ion concentration field of the supercapacitor during charging and discharging are at The change trend driven by the Faraday reaction model and the electric double layer effect model was determined.

Further, in one embodiment of the present invention, at the moment of embedded mechanical impact, the electrolyte will be driven by inertial force to generate directional flow, and the dynamic process of its flow field change is described by the Navier-Stokes equation:

Among them, u ₁ , ρ ₁ , and μ represent the flow field velocity, density, and dynamic viscosity of the electrolyte fluid, respectively.

Further, in one embodiment of the present invention, the built-in model of the lithium-ion battery module is corrected through the complex model construction method of the COMSOL weak form equation and the general form partial differential equation, so that the energy storage kinetic model conforms to the construction The energy storage-shock sensitive coupling model system of .

Further, in one embodiment of the present invention, the general-form partial differential equation framework is as follows:

Among them, u is the dependent variable of the partial differential equation, t is the independent variable, and other parameters are general coefficients.

Further, in one embodiment of the present invention, COMSOL software is used to simulate the shock sensitivity characteristics of the supercapacitor, and the supercapacitor has two kinds of shock sensitivity phenomena in different operating modes, wherein the first case is when When the supercapacitor is charged with a large current, the rate at which the reaction current gains and loses ions is far greater than the rate at which the ions diffuse in the solution. The second case is contrary to the first case. Due to the self-discharge effect of the supercapacitor, ions The concentration distribution has become balanced.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, wherein:

Fig. 1 is the simulation method flow chart of supercapacitor electrolyte ion redistribution effect under the mechanical impact according to the embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a supercapacitor according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of the electric double layer effect of a supercapacitor according to an embodiment of the present invention;

Fig. 4 is according to the Faraday reaction schematic diagram of supercapacitor in the embodiment of the present invention;

5 is a schematic diagram of ion redistribution of a supercapacitor under impact according to an embodiment of the present invention;

Fig. 6 is according to the weak form equation entry schematic diagram of COMSOL software in the embodiment of the present invention;

Figure 7 is a simulation diagram of two impact sensitive phenomena of a supercapacitor according to an embodiment of the present invention, wherein (a) is the first sensitive phenomenon: voltage fluctuates downward, and (b) is the second sensitive phenomenon: voltage fluctuates upward ;

Figure 8 is a simulation diagram of ion distribution during the shock process of a supercapacitor according to an embodiment of the present invention, wherein (a) is the first sensitive phenomenon, (b) is the second sensitive phenomenon, and ts represents the duration of the shock in the figure ;

FIG. 9 is a simulation diagram of a supercapacitor voltage peak amplitude under different discharge currents and discharge degrees according to an embodiment of the present invention;

Fig. 10 is the ion concentration field simulation diagram of the supercapacitor under different discharge currents according to the embodiment of the present invention, wherein, (a) is discharge current 5mA, (b) is discharge current 20mA;

Fig. 11 is a graph showing changes in the measured impact sensitivity phenomenon of a supercapacitor according to an embodiment of the present invention, wherein (a) is the impact sensitivity phenomenon of downward voltage fluctuation, and (b) is the impact sensitivity phenomenon of upward voltage fluctuation.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

The simulation method and system for the ion redistribution effect of the supercapacitor electrolyte proposed according to the embodiments of the present invention will be described below with reference to the accompanying drawings. First, the simulation method for the ion redistribution effect of the supercapacitor electrolyte proposed according to the embodiments of the present invention will be described with reference to the accompanying drawings .

Fig. 1 is a flow chart of a simulation method for the ion redistribution effect of the supercapacitor electrolyte under mechanical impact according to an embodiment of the present invention.

As shown in Figure 1, the simulation method for the ion redistribution effect of the supercapacitor electrolyte under mechanical impact includes the following steps:

In step S101, an energy storage dynamics model of the supercapacitor is established.

Among them, the energy storage kinetic model includes the electric double layer effect model and the Faraday reaction model.

Specifically, the energy storage kinetic model generates and stores energy through the highly reversible redox reaction between the electrode active material and the electrolyte material, in which the Faraday reaction model is dominant.

Further, in one embodiment of the present invention, the electric double layer effect model is corrected by faraday current through the energy storage dynamics model, so that the electric potential field and ion concentration field of the supercapacitor in the charging and discharging process are in the Faraday reaction model and The change trend driven by the two mechanisms of the electric double layer effect model was determined.

Specifically, as shown in Figure 2, the positive and negative electrodes of the supercapacitor are both porous film materials with high specific surface area, separated by a separator in the middle, and the pores of the electrodes and the separator are filled with liquid electrolyte. The energy storage mechanism of a supercapacitor includes two mechanisms, the electric double layer effect and the Faraday pseudocapacitance effect, and the embodiments of the present invention will carry out mechanism modeling studies based on the two mechanisms.

As shown in Figure 3, the porous electrode has a microscopic pore structure, forming a rich solid-liquid interface with the electrolyte. The energy storage mechanism of the electric double layer effect of supercapacitors is based on the electric double layer structure formed by the adsorption of positive and negative ions at the solid-liquid interface.

The essence of the charging and discharging process of a supercapacitor is the formation and disintegration of the microscopic electric double layer structure, and the resulting coupled changes in the potential and ion concentration of the electrode and electrolyte. For the two parts of the electrode and the diaphragm of the supercapacitor, the embodiment of the present invention respectively constructs electric field and electrolyte concentration field models, and conducts dynamic modeling research.

First, in a porous electrode, the current flowing from the electrode matrix phase to the electrode electrolyte phase can be described by the electric double layer current,

Among them, i ₁ represents the surface current density of the electrolyte phase of the electrode, and i _DL represents the current density generated by the electric double layer effect.

For the electrode matrix phase, the relationship between current and potential can be given by Ohm's law,

where is is the surface current density of the electrode matrix phase, _{σs ,eff} is the equivalent conductivity of the electrode matrix phase and _Ψs is the potential of the electrode matrix phase.

However, for the electrode electrolyte phase, a concentration field correction to Ohm's law is required,

Among them, i ₁ is the surface current density of the electrolyte phase of the electrode, σ _1,eff is the equivalent conductivity of the electrolyte phase of the electrode, Ψ ₁ is the potential of the electrolyte phase of the electrode, t ₊ is the transfer coefficient of the electrolyte solution, c ₁ is the ion concentration of the electrolyte solution, F, R and T represent Faraday's constant, universal gas constant and Kelvin temperature, respectively.

In porous media, the equivalent conductivity σ _l,eff of the electrolyte phase obeys the Bragman relation, that is, σ _1,eff =σ ₁ ε ₁ ^1.5 , where σ ₁ is the ionic conductivity of the electrolyte, and ε ₁ represents the electrode porosity.

The potential equation of the electrolyte phase can be obtained by combining equations (1) and (3)

Due to the conservation of charge, always holds. Combine this charge conservation equation with equation (2):

The ion concentration field is affected by both reflected current and ion migration, as shown in equation (6)

Among them, ε ₁ and D _1,eff represent the porosity of the electrode and the ion diffusion coefficient of the electrolyte solution, respectively, and t represents the time.

In the diaphragm part, since the diaphragm matrix is not conductive, i _s =0. so you can get Then the potential equation of the electrolyte phase can be expressed as:

Similar to equation (6), since there is no electric double layer reaction in the diaphragm part, the ion concentration field equation of the electrolyte phase can be given by the following formula,

According to the mechanism of the electric double layer effect, the electric double layer current density i _DL can be calculated by the following formula ^[85–87]

Among them, a _v represents the specific surface area of the porous electrode, and C _dl represents the capacitance parameter related to the electric double layer effect.

In addition, some supercapacitors also store and release energy through Faraday reactions. Faradaic reactions are highly reversible redox reactions that occur between electrode active materials and electrolyte materials (such as the redox reaction between a ruthenium oxide electrode and a sulfuric acid electrolyte). As shown in Figure 4, the electron gain and loss effect of the redox reaction makes the charge transfer, thereby realizing the energy storage.

The faraday current in the electrochemical system of the supercapacitor in which the faraday reaction plays a leading role in energy storage is much larger than the electric double layer current. Therefore, this type of supercapacitor energy storage kinetic model needs a series of corrections based on the electric double layer energy storage model equations (1)-(9).

First, in a porous electrode, the current flowing from the electrode matrix phase to the electrode electrolyte phase is composed of the electric double layer current and the Faraday current. The original equation (1) needs to add the Faraday current term:

Among them, i _F represents the current density generated by the Faradaic reaction.

Correspondingly, the electrolyte phase potential equation of Equation (4) and the electrode matrix phase potential equation of Equation (5) also need to add the Faraday current correction term:

For the ion concentration field described in Equation (6), the reaction current term should be composed of the electric double layer current and the Faraday current,

According to the electrochemical theory, the Faraday current density can be calculated by the following formula:

i _F =a _v j _1oc (14)

Among them, j _1oc represents the Faraday transfer current density, and its value can be calculated by the Butler-Volmer equation:

Among them, i ₀ represents the Faradaic exchange current density, α _a and α _c represent the transfer coefficients of the anode and cathode, respectively, and U _oc represents the open circuit potential of the Faradaic process.

By modifying the electric double layer energy storage model through equations (10) to (15), the embodiment of the present invention obtains a universal energy storage dynamics model of supercapacitors. Through this model, the change process of the electric potential field and ion concentration field of the supercapacitor during the charging and discharging process driven by the two mechanisms of Faraday reaction and electric double layer effect can be completely determined.

In step S102 , in the kinetic model of energy storage, a migration and redistribution model of electrolyte ions under mechanical impact is embedded to form a supercapacitor-based energy storage-shock sensitive coupling model system.

Further, in one embodiment of the present invention, the energy storage-shock sensitive coupling model system includes the electrode dynamics model of the electric double layer effect, the electrode kinetics model of the Faraday reaction, the ion diffusion model in the electrolyte, and the Electrolyte ion redistribution model.

It should be noted that energy storage dynamics modeling is an effective method for studying micro-nano energy devices, and has been applied in many fields in the field of supercapacitor research. The embodiment of the present invention comprehensively considers the energy storage effect and impact sensitivity effect of the supercapacitor, and performs integrated coupling modeling.

Specifically, in the electrochemical system of a supercapacitor, the electrochemical reaction will continuously generate ions at one electrode and consume ions at the other electrode at the same time. The general trend is to make the concentration of the positive and negative electrodes of ions in the electrolyte Distribution creates imbalances that accumulate. On the other hand, ions have a diffusion effect in the electrolyte, and the general trend is to equalize the ion concentration in the electrolyte. When the charge and discharge current of the supercapacitor is large and the electrochemical reaction is strong, the diffusion effect of the electrolyte will be far from enough to counteract the rapid production and consumption of ions caused by the reaction process. Therefore, the ion concentration imbalance in the electrolyte may be more significant, as shown in FIG. 5 .

The generation process of the ion concentration difference in the charging and discharging process and the impact sensitivity effect caused by it will be described in detail below. Before charging and discharging starts, the reaction current is 0, and the ions in the electrolyte are in a balanced state after a long-term diffusion effect.

When the charging and discharging process starts, the signs of the reaction currents of the positive and negative electrodes of the supercapacitor are opposite, and the two electrodes gain and lose ions respectively.

For the charging process:

For the discharge process:

Therefore, when the charge or discharge process starts, the ion concentration of the positive and negative electrodes will change oppositely, the equilibrium state of the ion concentration will be broken, and a difference in ion concentration will be generated between the positive and negative electrodes. This ion concentration difference effect is manifested by the ion concentration field having a non-zero gradient value:

At the moment of acceleration shock, the electrolyte will be driven by inertial force to generate directional flow, and the dynamic process of its flow field change can be described by the Navier-Stokes equation:

Among them, u ₁ , ρ ₁ , and μ represent the flow field velocity, density, and dynamic viscosity of the electrolyte fluid, respectively.

According to the theory of fluid mechanics, in the presence of an ion concentration gradient, the electrolyte flow will significantly change the ion concentration field distribution in a short time, so it is necessary to add flow field correction term,

Similarly, for the ion concentration field equation of the diaphragm part described by equation (8), the corresponding flow field correction is also required,

Equations (20)-(23) constitute the supercapacitor electrolyte flow field and ion concentration field acceleration shock response model. Combining it with the energy storage dynamics model, the complex coupling change process of the supercapacitor at the moment of impact caused by the impact sensitive effect of electrolyte ions on the electrochemical system can be quantitatively described. Thus, a foundation is laid for the subsequent simulation research on the ion impact sensitivity effect of the electrolyte according to the embodiment of the present invention.

In step S103, the finite element software is used to simulate the energy storage-shock sensitive coupling model system, so as to realize the effective simulation of the ion redistribution effect of the supercapacitor electrolyte under mechanical shock.

Wherein, the finite element software that the embodiment of the present invention utilizes is COMSOL software, and COMSOL software is a powerful multi-physics field simulation software, and the main body model equation of the lithium-ion battery module wherein and the supercapacitor impact that the embodiment of the present invention proposes The sensitive dynamic model is relatively close, so it is modified on the basis of this module to realize the simulation calculation of the impact sensitive characteristics of supercapacitors.

The embedded model of the Li-ion module is as follows:

However, the embedded model only includes the electrode energy storage kinetic equation, and does not consider the ion impact sensitivity effect of the supercapacitor proposed by the embodiment of the present invention.

Therefore, the embodiment of the present invention corrects the embedded model of the lithium-ion battery module through the complex model construction method of COMSOL weak form equation and general form partial differential equation, so that the energy storage kinetic model conforms to the established electrochemical energy storage-shock Sensitive coupling model system.

On the one hand, the embedded model ignores the influence of electrolyte flow and flow field changes on the ion concentration field and electric potential field. This defect can be corrected by editing the weak form code of the embedded equation. The so-called weak form is a form after the original partial differential equations are subjected to variational processing in the finite element calculation. As shown in Figure 6, select the "equation view" option in the COMSOL software system settings to enter the weak form editing mode. After transforming the ion concentration field correction model described by Equation (22) and Equation (23) into a weak form, the flow field correction of the concentration field equation of the module is realized by replacing the embedded original code in the module.

On the other hand, the relationship between shock acceleration and electrolyte flow field in the model system of the embodiment of the present invention is described by Equation (20) and Equation (21), which can be realized by adding new equations to the module. The general form partial differential equation framework provided by COMSOL is as follows:

Comparing with the model equations shown in Equation (20) and Equation (21), the corresponding coefficients are input into the general form Equation (25), and the supplementary correction of the simulation module can be completed.

Therefore, COMSOL software can be used to simulate the impact sensitive characteristics of supercapacitors. The simulation results show that two typical shock-sensitive phenomena will appear in different working modes of the supercapacitor, as shown in Fig. 7 respectively.

If the supercapacitor starts to discharge immediately after the high-current charging is completed, and receives an acceleration shock shortly after starting to discharge, the first sensitive phenomenon will occur, as shown in Fig. 7(a). At this time, the output voltage fluctuates downward at the moment of impact, which is recorded as ΔV<0. ΔV represents the rising value of the output voltage during the impact.

If the supercapacitor undergoes a long self-discharge process after being fully charged, and starts to discharge after the self-discharge is completed, and an impact occurs during the discharge process, the second sensitive phenomenon will occur, as shown in Figure 7(b). Contrary to Figure 7(a), the output voltage fluctuates upward at the moment of impact, which is recorded as ΔV>0.

The simulation of the ion concentration field during the impact can better explain the nature of these two sensitive phenomena.

For the first case, when the supercapacitor is charged with a large current, the rate of ion gain and loss by the reaction current is much greater than the rate of ion diffusion in the solution. Therefore, at the positive electrode, ions are accumulated in large quantities, and at the negative electrode, ions are consumed in large quantities. Before the impact begins, the ion concentration of the positive electrode is much greater than that of the negative electrode, and its ion concentration field distribution is shown in the square mark line in Fig. 8(a).

When the impact occurs, the flow of the electrolyte solution rapidly changes the ion concentration field distribution, and the ion concentration distribution in the solution returns to an approximately balanced state in a very short time. This ion redistribution process is shown in Fig. 8(a), where t _s represents the duration of the shock. According to the impact sensitive model of the supercapacitor, the change of the ion concentration field c ₁ will directly affect the electrolyte potential field Φ ₁ , and then affect its output voltage.

Furthermore, the voltage fluctuation phenomenon caused by the change of ion concentration field can be explained by the following electrochemical principle. During the discharge process, the ions are continuously combined with the positive electrode, and the impact makes the ion concentration distribution tend to be balanced, that is, the ion of the positive electrode is reduced. The reduction of the positive electrode ions reduces the discharge capacity of the positive electrode of the supercapacitor, thereby reducing its output voltage.

The second sensitive phenomenon is the opposite. Due to the self-discharge effect of the supercapacitor, after a long period of self-discharge, the ion concentration distribution has become balanced. Therefore, when the capacitor starts to discharge with a large current, the ion concentration of the negative electrode begins to significantly exceed that of the positive electrode, as shown by the square mark line in Figure 8(b). During the impact process, the ion concentration field also restores approximately equilibrium in a very short time. According to the description of the potential field of the electrolyte phase by equation (11), the influence of the ion concentration field c ₁ on the potential field depends on Since in Figure 8(a) and Figure 8(b) The signs of the values are opposite, so the voltage fluctuation corresponding to the second phenomenon is also opposite to the first phenomenon, which is manifested as an upward fluctuation of the voltage during the impact process. Based on the redistribution effect of electrolyte ions, the impact makes the concentration field distribution of electrolyte ions more balanced, that is, increases the positive ions. Therefore, the electrolyte can provide more ions for the Faraday reaction of the positive electrode, which increases the discharge capacity of the positive electrode of the supercapacitor and increases the output voltage.

Overall, the voltage fluctuation of the supercapacitor depends on the ion concentration distribution when the shock occurs. As shown in Fig. 7(a) and Fig. 8(a), if the ions are concentrated at the positive electrode (c ₁ |positive>c ₁ |negative) at the beginning of the shock, the voltage will fluctuate downward during the shock. As shown in Fig. 7(b) and Fig. 8(b), on the contrary, if the ions are concentrated on the negative electrode (c ₁ |positive<c ₁ |negative) at the initial moment of impact, the voltage will fluctuate upward during the process.

Discharge current and discharge degree are two important factors affecting the distribution of supercapacitor ion concentration field (the definition of discharge degree is 1 minus the ratio of output voltage and maximum charging voltage), and the simulation method proposed in the embodiment of the present invention can analyze parameters for mechanical impact Under the influence of ion redistribution effect. As shown in Figure 9, it shows the amplitude of the upward fluctuation of the voltage generated by the impact under different discharge currents and discharge degrees, so that the impact response characteristics of the supercapacitor can be analyzed.

First, when the discharge current is the same, the greater the discharge degree of the supercapacitor, the greater the amplitude of the upward fluctuation of the voltage generated by the shock; secondly, when the discharge degree of the supercapacitor is the same, the greater the discharge current, the greater the upward fluctuation of the voltage generated by the shock. The larger the fluctuation amplitude is; third, when the discharge current is small, the relationship between the voltage fluctuation amplitude and the discharge degree is shown as the square mark line and the circle mark line in Figure 9. At this time, when the discharge degree is small, the voltage fluctuation amplitude has an approximately linear relationship with the discharge degree, and when the discharge degree is large, as the discharge degree continues to increase, the voltage fluctuation amplitude increases more and more slowly, and eventually tends to in convergence. Fourth, when the discharge current is large, the relationship between the voltage fluctuation amplitude and the discharge degree can always be approximately linear, as shown by the triangle mark line in FIG. 9 .

The relationship between the shock voltage fluctuation amplitude of the supercapacitor in Fig. 9 and the discharge current and discharge degree can be further explained by the ion concentration field simulation results in Fig. 10 .

First, the generation of the ion concentration gradient comes from the accumulation of the Faraday reaction current gain and loss ion effect. Therefore, the greater the degree of discharge, the more ions accumulated in the negative electrode, and the greater the ion concentration gradient. Therefore, the ion concentration equalization redistribution effect generated by the impact will change the ion concentration field more, and then will have a more significant impact on the output voltage.

Second, the essence of the ion concentration gradient is that the rate of Faraday reaction gain and loss of ions exceeds the rate of ion diffusion, so the greater the discharge current, the more intense the Faraday reaction and the greater the ion concentration gradient.

Third, according to the ion concentration field dynamics mechanism described by Equation (13), the rate of ion diffusion depends on the size of the ion concentration gradient, so as the degree of discharge increases, the ion concentration gradient continues to accumulate. When the ion concentration gradient accumulates to a large enough size, the ion diffusion effect will be sufficient to offset the influence of the Faradaic reaction on the ion concentration field, and then the ion concentration field will remain in a stable state, as shown in Figure 10. Therefore, when the discharge degree is large enough, although the discharge degree continues to increase, the amplitude of the voltage fluctuation caused by the impact basically tends to be stable.

Therefore, the simulation method of the embodiment of the present invention has been able to comprehensively analyze the ion concentration redistribution effect of the supercapacitor under mechanical impact. In order to further verify the correctness of the conclusion of the simulation analysis, the embodiment of the present invention uses the Marshall hammer test system to test the impact response characteristics of the supercapacitor, and uses the CHI660 electrochemical workstation to record the voltage response signal of the device at the moment of impact.

The following experimental tests confirm the two shock-sensitivity phenomena discussed in the simulation analysis.

Corresponding to the first impact sensitive phenomenon, the experimental test charges the supercapacitor with a current of 20mA, and starts discharging immediately after the charging is completed, and performs a Marshall impact test. The output voltage of the device recorded in the experiment is shown in Figure 11(a), and the voltage fluctuates downward (ΔV<0) at the moment of impact.

Corresponding to the second impact sensitive phenomenon, after the supercapacitor is fully charged, it is kept at a constant voltage for a long time to restore its ion concentration field to balance, and then it starts to discharge at a current of 20mA, and a Marshall impact test is performed during the discharge process. The output voltage of the device recorded in the experiment is shown in Figure 11(b), and the voltage fluctuates upward (ΔV>0) at the moment of impact.

Therefore, according to the simulation method of the supercapacitor electrolyte ion redistribution effect under the mechanical impact proposed by the embodiment of the present invention, the effective simulation of the ion redistribution phenomenon of the supercapacitor under the mechanical impact can be realized, and the simulation results are qualitatively consistent with the experimental results. Consistent, can effectively promote the research on the mechanical impact characteristics of supercapacitors, and provide technical support for the research and development of supercapacitors used in special mechanical environments.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise specified limit. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first and second feature may be in direct contact with the second feature through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (9)

1. A simulation method of supercapacitor electrolyte ion redistribution effect under mechanical impact, it is characterized in that, comprises the following steps: Establish the energy storage dynamics model of supercapacitor; In the energy storage dynamics model, a migration and redistribution model of electrolyte ions under mechanical impact is embedded to form a supercapacitor-based energy storage-shock sensitive coupling model system; and The finite element software is used to simulate and calculate the energy storage-shock sensitive coupling model system, so as to realize the effective simulation of ion redistribution effect of supercapacitor electrolyte under mechanical impact. 2. the simulation method of supercapacitor electrolyte ion redistribution effect under mechanical impact according to claim 1, is characterized in that, described energy storage dynamics model comprises electric double layer effect model and Faraday reaction model. 3. the simulation method of supercapacitor electrolyte ion redistribution effect under mechanical impact according to claim 1, is characterized in that, described energy storage dynamics model is by the highly reversible that takes place between electrode active material and electrolyte material The oxidation-reduction reaction allows charge transfer to generate and store energy, where the Faradaic reaction model dominates energy storage. 4. the simulation method of supercapacitor electrolyte ion redistribution effect under mechanical shock according to claim 1, is characterized in that, described energy storage-shock sensitive coupling model system comprises the electrode dynamics model of electric double layer effect, Faraday The electrode kinetic model of the reaction, the ion diffusion model in the electrolyte and the electrolyte ion redistribution model under mechanical impact. 5. according to the simulation method of supercapacitor electrolyte ion redistribution effect under the described mechanical shock of claim 1 or 4, it is characterized in that, carry out Faraday current correction to electric double layer effect model by described energy storage dynamics model, make The variation trends of the electric potential field and the ion concentration field of the supercapacitor in the process of charging and discharging under the joint drive of the Faraday reaction model and the electric double layer effect model are determined. 6. the simulation method of ion redistribution effect of supercapacitor electrolyte under mechanical impact according to claim 1, it is characterized in that, when embedding mechanical impact, electrolyte will be driven by inertial force to produce directional flow, and the change of its flow field The kinetic process is described by the Navier-Stokes equation: Among them, u ₁ , ρ ₁ , and μ represent the flow field velocity, density, and dynamic viscosity of the electrolyte fluid, respectively. 7. the simulation method of supercapacitor electrolyte ion redistribution effect under mechanical impact according to claim 1, it is characterized in that, through the complex model building method of COMSOL weak form equation and general form partial differential equation, to lithium ion battery module The embedded model is corrected so that the energy storage dynamic model conforms to the constructed energy storage-shock sensitive coupling model system. 8. the simulation method of supercapacitor electrolyte ion redistribution effect under the mechanical shock according to claim 7, is characterized in that, described general form partial differential equation framework is as follows: Among them, u is the dependent variable of the partial differential equation, t is the independent variable, and other parameters are general coefficients. 9. the simulation method of supercapacitor electrolyte ion redistribution effect under the mechanical impact according to claim 1, it is characterized in that, utilize COMSOL software to simulate the impact sensitive characteristic of described supercapacitor, described supercapacitor is in different work There are two kinds of impact sensitive phenomena in the mode, wherein, the first case is that when the supercapacitor is charged with a large current, the rate of gaining and losing ions by the reaction current is far greater than the rate of ion diffusion in the solution, and the second case is the same as that of the supercapacitor Contrary to the first case described above, the ion concentration distribution has become equalized due to the self-discharge effect of the supercapacitor.