CN105677979A - Lithium titanate battery improvement model based on Butler-Volmer equation - Google Patents

Abstract

The invention relates to a lithium titanate battery improvement model based on a Butler-Volmer equation. A traditional first-order RC circuit model structure is adopted, parameter values of different SOCs under the benchmark rate are obtained through OCV-SOC test data, the charging and discharging polarization voltage of each SOC point under the typical rate is solved, battery characteristic parameters are obtained on the basis of a least square fitting tool, and then the lithium titanate battery improvement model suitable for the wide rate range is obtained. The lithium titanate battery improvement model based on the Butler-Volmer equation not only inherits the advantages, being simple in structure and easy to simulate, of an electrical model, but also has the superiority of the mechanism description of an electrochemical dynamics equation, therefore, the problem that in high-rate application of a lithium titanate battery, the description error of a traditional first-order RC circuit model is too high is solved, the dynamic and static characteristics of the lithium titanate battery can be accurately described, and a theoretical basis is supplied to the design of a control system in large-scale application of the lithium titanate battery.

Description

Based on the lithium titanate battery improved model of Butler-Volmer equation

Technical field

The present invention relates to power cell modeling field, it is the lithium titanate battery improved model based on Butler-Volmer equation specifically. Espespecially can be applicable to the track traffic lithium titanate battery improved model of high magnification application operating mode.

Background technology

In order to tackle day by day serious environmental pollution and energy dilemma, the exploitation of electric vehicle and universal extremely urgent. The core component that power cell is united as electric vehicle powertrain, its performance is most important to the security of vehicle operating and high efficiency.

In recent years, lithium cell relies on from the advantage in specific power, specific energy and cycle life aspect, is widely used in new energy vehicle and electrical network energy storage field. Relative to adopting graphite as the power-type ferric phosphate lithium cell of negative pole and lithium manganate battery, lithium titanate material is adopted to have outstanding rate charge-discharge characteristic, temperature profile and more stable structure as the lithium titanate battery of negative pole, it is more suitable for the power-driven system for frequent start-stop, become following electric vehicle powertrain system, especially one of optimal selection of rail traffic vehicles.

As the basis of prediction energy capacity of battery state and power state, the accuracy of battery model directly has influence on final prediction precision. Set up battery model to need to take into account complexity and accuracy, the basis ensureing model accuracy makes model simplify.

Battery model conventional at present comprises: electrochemistry model and electrical model, wherein:

Electrochemistry model fully characterizes material behavior and the reaction mechanism of battery, foundation can be provided for battery optimization designs, but electrochemistry model comprises multiple mark partial differential equation and a large amount of known variables, add the complexity of model, and directly cannot connect with power system other parts. Although electrochemistry model can simplify from multiple angle, but while simplifying, model accuracy reduces, and the model after simplifying still is difficult to meet the requirement of application.

Electrical model portrays battery kinetic characteristic by the combination of electricity component, has simpler structure and less unknown parameter, comprises a traditional rank RC circuit model etc., is more suitable for battery performance emulation.

Multiplying power, as the important factor affecting battery behavior, refers to numerically equal the multiple of rated capacity by the current value that battery is released its rated capacity in specific time and exported. Multiplying power change can cause non-linear capacity effect, especially recovery Effects. Non-linear capacity effect refers to the phenomenon that cell container changes under different multiplying; Recovery Effects then refers to after high-multiplying power discharge terminates and leaves standstill certain time, battery still can low range electric discharge phenomenon.

The state-of-charge SOC interval under different multiplying is normalized by the multiplying power factor by introducing document, but detailed analysis multiplying power is not on the impact of battery parameter; Also there is document to establish a kind of strengthening circuit model based on electrical model and diffusion model, but comprise a large amount of unknown parameter and complicacy due to diffusion model so that this model cannot be used for real-time simulation; Having the mixture model researching and proposing a kind of electrical model and electrochemical kinetics models coupling, and demonstrate model accuracy in certain multiplying power scope, relatively diffusion model is simpler for this model, but still has higher complexity; Document is also had by the expression formula of parameter value when matched curve acquisition different multiplying and to carry out finishing fruit checking, but checking process is only less than in the narrow multiplying power scope of 2C in multiplying power and carries out, and formula form and parameter do not possess any actual meaning, there is certain limitation.

It is therefore desirable to propose a kind of battery model taking into account complexity and accuracy apply with accurate description lithium titanate battery high magnification under electrical behavior.

Summary of the invention

For the defect existed in prior art, it is an object of the invention to provide the lithium titanate battery improved model based on Butler-Volmer equation, it is achieved that the battery model taking into account complexity and accuracy is with the electrical behavior under the application of accurate description lithium titanate battery high magnification.

For reaching above object, the technical scheme that the present invention takes is:

Based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: the impact adding the multiplying power factor on the basis of a traditional rank RC circuit model structure, by controlled voltage source U_ocv, series resistance R_ΩAnd RC network is formed with polarization amending unit four part;

Described controlled voltage source U_ocvRepresent the change of open circuit voltage OCV with battery SOC of battery;

Described series resistance R_ΩEmbody the power loss that battery produces in charge and discharge process;

Described RC network is R_pC_pParallel network, reflects inside battery by the overpotential caused by electrochemical reaction imbalance, is commonly referred to polarizing voltage, is designated as U_p;

Controlled voltage source U_ocv, series resistance R_Ω, electric capacity C_pThere is nonlinear relationship with SOC, physical relationship is:

$\left\{\begin{array}{c}{U}_{ocv}\[SOC\left(t\right)\]=a_{1}SOC\left(t\right)+a_2\\ R_{\mathrm{\Ω}}\[SOC\left(t\right)\]=b_{1}SOC\left(t\right)+b_2\\ C_p\[SOC\left(t\right)\]=c_{1}SOC\left(t\right)+c_2\end{array}\right.---\left(1\right)$

In formula (1), a₁、a₂、b₁、b₂、c₁、c₂For constant, the parameter basis of different SOC is obtained by linear interpolation.

On the basis of technique scheme, described polarization amending unit is made up of Butler-Volmer equation simplification form, for revising battery circuit to polarization resistance R_pInfluence degree, physical relationship is:

$R_p=\left\{\begin{array}{cc}\[f_1\left(SOC\right)*ln\left(f_2\right(SOC)\·I_o(t)+\sqrt{{\left(f_2\right(SOC)\·I_o(t\left)\right)}^2+1})\]/I_o\left(t\right),& I_o\left(t\right)\≠0\\ R_{pc},& I_o\left(t\right)=0\end{array}\right.---\left(2\right)$

In formula (2), f₁(SOC)、f₂(SOC) coefficient of Butler-Volmer equation simplification form under different SOC is represented, and R_pcThe polarization resistance value obtained under representing benchmark multiplying power, I_oFor by the current value of battery.

On the basis of technique scheme, described improved model obtains in the following manner:

Adopt a traditional rank RC circuit model structure, the parameter value of different SOC under obtaining benchmark multiplying power by OCV-SOC test data, ask for the discharge and recharge polarizing voltage of typical case's multiplying power under each SOC point, obtain battery behavior parameter based on least square fitting instrument simultaneously, obtain being applicable to the lithium titanate battery improved model of wide multiplying power scope.

On the basis of technique scheme, described OCV-SOC test data comprises 20 charging pulses and 20 discharge pulses, and each pulse duration is 180 seconds;

For making battery reach equilibrium state, all have the time of repose of 1 hour after each pulse, leave standstill the magnitude of voltage terminating the moment namely as the U under current SOC_ocv。

On the basis of technique scheme, choose the numerical value being obtained series resistance by the voltage saltus step in 1s based on formula (9),

R_Ω=Δ U_o/ΔI_o(9)

Wherein, Δ U_oWith Δ I_oRepresent the voltage change in 1 second and curent change respectively.

On the basis of technique scheme, voltage responsive adopts formula (10) to carry out least square fitting, and then the R obtained under different SOC_pcAnd C_pNumerical value,

$\left\{\begin{array}{c}{U}_p\left(t\right)=A\·\[1-e^{-t/\mathrm{\τ}}\]\\ R_{pc}=A/I_o\\ C_p=\mathrm{\τ}/R_{pc}\end{array}\right.---\left(10\right)$

Wherein, A represents the polarizing voltage amplitude needing matching, and τ represents the time constant in polarizing voltage process of establishing.

On the basis of technique scheme, the discharge and recharge polarizing voltage of each SOC point described lower typical case multiplying power is obtained by the charge-discharge test under typical case's multiplying power and the parameter value under benchmark multiplying power, specifically such as formula shown in (11):

U_p(t)=U_ocv(t)-U_o(t)-R_ΩI_o(t)(11)

Wherein U_oRepresent battery terminal voltage.

On the basis of technique scheme, the described battery behavior parameter obtained based on least square fitting instrument, comprising: the charging part of Butler-Volmer equation simplification form coefficient and discharge portion.

On the basis of technique scheme, in view of in different multiplying process of charging, battery is in different SOC when being changed into constant voltage charge from constant current charge, and along with multiplying power increase battery more early enter the constant voltage charge stage, therefore: the charging part of Butler-Volmer equation simplification form coefficient only discusses SOC ∈ [10,75];

When SOC ∈ [75,90], owing to the reduction gradually of constant-voltage phase electric current excitation is close to zero, it is believed that battery parameter is substantially constant, the parameter value obtained under still adopting benchmark multiplying power;

The interval of the discharge portion discussion of Butler-Volmer equation simplification form coefficient is SOC ∈ [10,90].

Lithium titanate battery improved model based on Butler-Volmer equation of the present invention, not only inherit the simple advantage with being easy to emulation of structure of electrical model, more have the superiority of electrochemical kinetics equation mechanism description, efficiently solve a traditional rank RC circuit model in the application of lithium titanate battery high magnification and describe the excessive problem of error, can accurate description lithium titanate battery static and dynamic performance, in lithium titanate battery large-scale application, the design of Controlling System provides theoretical foundation. Useful effect is:

1. first the reduced form of electrochemistry Butler-Volmer equation is combined with a traditional rank RC circuit model, not only inherits the superiority of theoretical description, more can be directly used in system integration project and precision height;

2. a kind of battery improved model being applicable to the application of metatitanic acid lithium high magnification is proposed first, can accurately portray the static and dynamic performance under lithium titanate battery continuous current operating mode and FUDS (FederalUrbanDrivingSchedule) time-dependent current operating mode, in the large-scale application of lithium titanate battery, the design of Controlling System provides theoretical foundation.

Accompanying drawing explanation

The present invention has following accompanying drawing:

Fig. 1 the present invention proposes the structural representation of model;

Fig. 2 lithium titanate battery typical case's OCV-SOC curve;

Fig. 3 typical pulse charging voltage responds;

Model error contrasts (10C electric discharge is example) Fig. 4 tradition one rank RC circuit model with proposing;

The contrast of model emulation voltage and experimental data is proposed under Fig. 5 continuous current operating mode;

The error distribution of voltage is emulated under Fig. 6 continuous current operating mode;

The contrast of model emulation voltage and experimental data is proposed under Fig. 7 FUDS time-dependent current operating mode;

The error distribution of voltage is emulated under Fig. 8 FUDS time-dependent current operating mode;

Fig. 9 overall flow figure of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

As shown in Figure 9, for the overall flow figure of the present invention, lithium titanate battery improved model based on Butler-Volmer equation of the present invention, adopt a traditional rank RC circuit model structure, the parameter value of different SOC under obtaining benchmark multiplying power (being taken as 1C in the present invention) by OCV-SOC test data, ask for the discharge and recharge polarizing voltage of typical case's multiplying power under each SOC point, obtain battery behavior parameter based on least square fitting instrument simultaneously, obtain being applicable to the lithium titanate battery improved model of wide multiplying power scope. High magnification continuous current operating mode and FUDS time-dependent current operating mode are all had the voltage precision within 2% by empirical tests.

Described lithium titanate battery espespecially track traffic lithium titanate battery.

Lithium titanate battery improved model based on Butler-Volmer equation of the present invention, as shown in Figure 1, adds the impact of the multiplying power factor, by controlled voltage source U on the basis of a traditional rank RC circuit model structure_ocv, series resistance R_ΩAnd RC network is formed with polarization amending unit four part;

Described controlled voltage source U_ocvRepresent the change of open circuit voltage OCV with battery SOC of battery;

Described series resistance R_ΩEmbody the power loss that battery produces in charge and discharge process;

Described RC network is R_pC_pParallel network, reflects inside battery by the overpotential caused by electrochemical reaction imbalance, is commonly referred to polarizing voltage, is designated as U_p;

Controlled voltage source U_ocv, series resistance R_Ω, electric capacity C_pThere is nonlinear relationship with SOC, physical relationship is:

$\left\{\begin{array}{c}{U}_{ocv}\[SOC\left(t\right)\]=a_{1}SOC\left(t\right)+a_2\\ R_{\mathrm{\Ω}}\[SOC\left(t\right)\]=b_{1}SOC\left(t\right)+b_2\\ C_p\[SOC\left(t\right)\]=c_{1}SOC\left(t\right)+c_2\end{array}\right.---\left(1\right)$

In formula (1), a₁、a₂、b₁、b₂、c₁、c₂For constant, the parameter basis of different SOC is obtained by linear interpolation.

On the basis of technique scheme, described polarization amending unit is made up of Butler-Volmer equation simplification form, for revising battery circuit to polarization resistance R_pInfluence degree, physical relationship is:

$R_p=\left\{\begin{array}{cc}\[f_1\left(SOC\right)*ln\left(f_2\right(SOC)\·I_o(t)+\sqrt{{\left(f_2\right(SOC)\·I_o(t\left)\right)}^2+1})\]/I_o\left(t\right),& I_o\left(t\right)\≠0\\ R_{pc},& I_o\left(t\right)=0\end{array}\right.---\left(2\right)$

In formula (2), f₁(SOC)、f₂(SOC) coefficient of Butler-Volmer equation simplification form under different SOC is represented, and R_pcThe polarization resistance value obtained under representing benchmark multiplying power, I_oFor by the current value of battery.

Described Butler-Volmer equation simplification form by Butler-Volmer equation primitive form through being repeatedly out of shape gained. The relation of the interpretation that Butler-Volmer equation primitive form reacts from inside battery between battery overpotential and current density, is also called stable state electrochemical polarization equation, is one of basic formula setting up electrochemistry model, and its expression formula is:

$J\left(t\right)=J_0\[\exp \left(\frac{\mathrm{\α}F}{RT}\mathrm{\η}\right(t\left)\right)-\exp \left(\frac{-(1-\mathrm{\α})F}{RT}\mathrm{\η}\right(t\left)\right)\]---\left(3\right)$

Wherein, R represents moles of gas constant; T represents Kelvin temperature; F is faraday's constant; J₀Representing exchange current density, α represents transmission coefficient, and J represents current density, and η represents battery overpotential, also referred to as battery polarization voltage.

But, formula (3) comprises multiple known variables and directly cannot obtain changing, by electric current excitation, the overpotential value caused from equation, it is thus desirable to could use after this equation is carried out form conversion. The electric current represented based on formula (4) and the relation of current density, formula (3) can abbreviation be formula (5), and wherein S represents useful area.

I_o(t)=J (t) × S (4)

$\frac{I_o\left(t\right)}{J_0\×S}=\[\exp \left(\frac{\mathrm{\α}F}{RT}\mathrm{\η}\right(t\left)\right)-\exp \left(\frac{-(1-\mathrm{\α})F}{RT}\mathrm{\η}\right(t\left)\right)\]---\left(5\right)$

Considering in electrochemical reaction generation process generally have α ≈ 0.5, now, formula (5) by further abbreviation, can obtain such as formula the relational expression shown in (6).

$\mathrm{\η}\left(t\right)=\frac{2RT}{F}ln(\frac{1}{2J_{0}S}{I}_o\left(t\right)+\sqrt{{\left(\frac{1}{2J_{0}S}{I}_o\right(t\left)\right)}^2+1})---\left(6\right)$

Formula (6) although in still comprise part cannot the outside electrochemistry variable obtained, but can directly obtain changing the overpotential caused by battery circuit, meanwhile, exchange current density and useful area Two Variables and battery state are closely related, and reflect the complexity of polarization process. It will be seen that other variable one timings, the increase of battery circuit can make battery substantial deviation equilibrium state, thus causes higher overpotential. And when battery circuit reduces and during close to zero, overpotential is also tending towards zero, shows that now battery is close to equilibrium state.

When battery discharge current is suddenly by I₁Turn into I₂Time, it will be recognized that Δ t < ε, wherein ε is a limited little variable, then have shown in formula (7) relation such as not, now Δ SOC ≈ 0. Series resistance is as the concentrated reflection of the resistance characteristic such as battery electrode, electrolytic solution, and its numerical values recited is basic unrelated with electric current. Curent change can be obtained on the impact of battery polarization by formula (6), shown in (8), wherein U_pmaxRepresent that battery polarization voltage sets up the value after completely. And then, it is possible to obtain R_pWith I_oRelational expression, i.e. Butler-Volmer equation simplification form in the present invention.

ΔSOC≤max{I₁Δt,I₂Δt}≤max{I₁ε,I₂ε}(7)

$\begin{array}{c}{U}_{p_{\max }}=R_p{I}_o\left(t\right)\\ =f_1\left(SOC\right)*\ln \left(f_2\right(SOC)\&CenterDot;I_o(t)+\sqrt{{\left(f_2\right(SOC)\&CenterDot;I_o(t\left)\right)}^2+1})\end{array}---\left(8\right)$

On the basis of technique scheme, described OCV-SOC test data comprises 20 charging pulses and 20 discharge pulses, and each pulse duration is 180 seconds;

For making battery reach equilibrium state, all have the time of repose of 1 hour after each pulse, leave standstill the magnitude of voltage terminating the moment namely as the U under current SOC_ocv。

Fig. 2 is the battery open circuit voltage under lithium titanate battery discharge and recharge two states, it can be seen that open circuit voltage and SOC are closely related, and the open circuit voltage under lithium titanate battery charging and discharging state has higher consistence.

Fig. 3 is the voltage responsive of typical pulse excitation, it can be seen that the response of pulse excitation meets the expression form of RC parallel network.

Consider the restriction of actual samples frequency, choose the numerical value being obtained series resistance by the voltage saltus step in 1s based on formula (9). Owing to circuit structure only adopts a RC network representation battery polarization process, therefore voltage responsive adopts formula (10) to carry out least square fitting, and then the R obtained under different SOC_pcAnd C_pNumerical value. It is noted that the present invention adopts two groups of parameters to describe the difference of battery charging with discharge process.

R_Ω=Δ U_o/ΔI_o(9)

$\left\{\begin{array}{c}{U}_p\left(t\right)=A\&CenterDot;\&lsqb;1-e^{-t/\mathrm{\&tau;}}\&rsqb;\\ R_{pc}=A/I_o\\ C_p=\mathrm{\&tau;}/R_{pc}\end{array}\right.---\left(10\right)$

Wherein, Δ U_oWith Δ I_oRepresenting the voltage change in 1 second and curent change respectively, and A represents the polarizing voltage amplitude needing matching, τ represents the time constant in polarizing voltage process of establishing.

On the basis of technique scheme, the discharge and recharge polarizing voltage of each SOC point described lower typical case multiplying power is obtained by the charge-discharge test under typical case's multiplying power and the parameter value under benchmark multiplying power, specifically such as formula shown in (11):

U_p(t)=U_ocv(t)-U_o(t)-R_ΩI_o(t)(11)

Wherein U_oRepresent battery terminal voltage.

On the basis of technique scheme, the described battery behavior parameter obtained based on least square fitting instrument, comprising: the charging part of Butler-Volmer equation simplification form coefficient and discharge portion.

In view of in different multiplying process of charging, battery is in different SOC when being changed into constant voltage charge from constant current charge, and along with multiplying power increase battery more early enter the constant voltage charge stage, therefore the charging part of the Butler-Volmer equation simplification form coefficient of the present invention only discusses SOC ∈ [10,75]. And when SOC ∈ [75,90], owing to the reduction gradually of constant-voltage phase electric current excitation is close to zero, it is believed that battery parameter is substantially constant, the parameter value obtained under still adopting benchmark multiplying power. And the interval of the discharge portion discussion of Butler-Volmer equation simplification form coefficient is SOC ∈ [10,90].

The present invention is under the prerequisite of the integrity and consistence that ensure other parts of model, respectively a rank RC circuit model traditional under high magnification constant current operating mode and the present invention are verified, as can be seen from Figure 4, in battery 10C discharge process, the phantom error of a traditional rank RC circuit model shows a rising trend and eventually exceeds 80mV; And the phantom error of the present invention is maintenance trend and maximum is no more than 30mV. Result shows that the present invention effectively describes battery electrochemical behavior, significantly reduces model error.

High magnification constant current operating mode has been verified by the present invention, can find out that emulation result and experimental data have the consistence of height from Fig. 5 and Fig. 6, and error was less than 0.5% within 240 seconds, and in 300 seconds, error is less than 1.5%. As can be seen from Figures 7 and 8, under FUDS time-dependent current operating mode, the model emulation result that the present invention proposes is same has consistence highly with experimental data, is less than 1.5% with error error in 2250 seconds.

By above comparative analysis it will be seen that the present invention is more more accurate than a traditional rank RC circuit model, it is possible to the well static and dynamic performance of simulated battery, no matter under high magnification constant current operating mode or FUDS dynamic operation condition error all within 2%.

More than for the present invention's preferably specific implementation, in addition also have other implementations, it is necessary to explanation be that the replacement of any obvious suggestion under the prerequisite not departing from present inventive concept is all within protection domain of the present invention.

The content not being described in detail in this specification sheets belongs to the known prior art of professional and technical personnel in the field.

Claims (9)

1. based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: the impact adding the multiplying power factor on the basis of a traditional rank RC circuit model structure, by controlled voltage source U_ocv, series resistance R_ΩAnd RC network is formed with polarization amending unit four part;

Described controlled voltage source U_ocvRepresent the change of open circuit voltage OCV with battery SOC of battery;

Described series resistance R_ΩEmbody the power loss that battery produces in charge and discharge process;

Described RC network is R_pC_pParallel network, reflects inside battery by the overpotential caused by electrochemical reaction imbalance, is commonly referred to polarizing voltage, is designated as U_p;

Controlled voltage source U_ocv, series resistance R_Ω, electric capacity C_pThere is nonlinear relationship with SOC, physical relationship is:

$\left\{\begin{array}{c}{U}_{ocv}\&lsqb;SOC\left(t\right)\&rsqb;=a_{1}SOC\left(t\right)+a_2\\ R_{\mathrm{\&Omega;}}\&lsqb;SOC\left(t\right)\&rsqb;=b_{1}SOC\left(t\right)+b_2\\ C_p\&lsqb;SOC\left(t\right)\&rsqb;=c_{1}SOC\left(t\right)+c_2\end{array}\right.---\left(1\right)$

In formula (1), a₁、a₂、b₁、b₂、c₁、c₂For constant, the parameter basis of different SOC is obtained by linear interpolation.

2. as claimed in claim 1 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: described polarization amending unit is made up of Butler-Volmer equation simplification form, for revising battery circuit to polarization resistance R_pInfluence degree, physical relationship is:

$R_p=\left\{\begin{array}{cc}\&lsqb;f_1\left(SOC\right)*\ln \left(f_2\right(SOC)\&CenterDot;I_o(t)+\sqrt{{\left(f_2\right(SOC)\&CenterDot;I_o(t\left)\right)}^2+1})\&rsqb;/I_o\left(t\right),& I_o\left(t\right)\&NotEqual;0\\ R_{pc},& I_o\left(t\right)=0\end{array}\right.---\left(2\right)$

In formula (2), f₁(SOC)、f₂(SOC) coefficient of Butler-Volmer equation simplification form under different SOC is represented, and R_pcThe polarization resistance value obtained under representing benchmark multiplying power, I_oFor by the current value of battery.

3. as claimed in claim 1 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: described improved model obtains in the following manner:

Adopt a traditional rank RC circuit model structure, the parameter value of different SOC under obtaining benchmark multiplying power by OCV-SOC test data, ask for the discharge and recharge polarizing voltage of typical case's multiplying power under each SOC point, obtain battery behavior parameter based on least square fitting instrument simultaneously, obtain being applicable to the lithium titanate battery improved model of wide multiplying power scope.

4. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: described OCV-SOC test data comprises 20 charging pulses and 20 discharge pulses, and each pulse duration is 180 seconds;

For making battery reach equilibrium state, all have the time of repose of 1 hour after each pulse, leave standstill the magnitude of voltage terminating the moment namely as the U under current SOC_ocv。

5. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: the numerical value being obtained series resistance by the voltage saltus step in 1s is chosen based on formula (9),

R_Ω=△ U_o/△I_o(9)

Wherein, Δ U_oWith Δ I_oRepresent the voltage change in 1 second and curent change respectively.

6. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterised in that: voltage responsive adopts formula (10) to carry out least square fitting, and then the R obtained under different SOC_pcAnd C_pNumerical value,

$\left\{\begin{array}{c}{U}_p\left(t\right)=A\&CenterDot;\&lsqb;1-e^{-t/\mathrm{\&tau;}}\&rsqb;\\ R_{pc}=A/I_o\\ C_p=\mathrm{\&tau;}/R_{pc}\end{array}\right.---\left(10\right)$

Wherein, A represents the polarizing voltage amplitude needing matching, and τ represents the time constant in polarizing voltage process of establishing.

7. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterized in that: the discharge and recharge polarizing voltage of each SOC point described lower typical case multiplying power is obtained by the charge-discharge test under typical case's multiplying power and the parameter value under benchmark multiplying power, specifically such as formula shown in (11):

U_p(t)=U_ocv(t)-U_o(t)-R_ΩI_o(t)(11)

Wherein U_oRepresent battery terminal voltage.

8. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterized in that: the described battery behavior parameter obtained based on least square fitting instrument, comprising: the charging part of Butler-Volmer equation simplification form coefficient and discharge portion.

9. as claimed in claim 3 based on the lithium titanate battery improved model of Butler-Volmer equation, it is characterized in that: in view of in different multiplying process of charging, battery is in different SOC when being changed into constant voltage charge from constant current charge, and along with multiplying power increase battery more early enter the constant voltage charge stage, therefore: the charging part of Butler-Volmer equation simplification form coefficient only discusses SOC ∈ [10,75];

When SOC ∈ [75,90], owing to the reduction gradually of constant-voltage phase electric current excitation is close to zero, it is believed that battery parameter is substantially constant, the parameter value obtained under still adopting benchmark multiplying power;

The interval of the discharge portion discussion of Butler-Volmer equation simplification form coefficient is SOC ∈ [10,90].