CN115189047B - A lithium-ion battery non-lithium deposition control method and system - Google Patents

Abstract

The present invention relates to a lithium-ion battery non-lithium deposition control method and system. The method comprises: introducing correction items of lithium deposition reaction, SEI film growth and battery charging and discharging temperature to establish an electrochemical aging model of the battery; setting multiple simulation operating points; based on the electrochemical aging model, pre-simulating battery charging under multiple operating conditions according to the simulation operating points, determining a lithium deposition thickness change curve and an overpotential curve at the negative electrode-diaphragm; obtaining the actual ambient temperature and the actual charging rate; based on the above curves, determining two adjacent temperature operating points, and extracting the maximum charging current rate corresponding to the temperature operating points; performing a parameterized scan of the charging rate according to the two maximum charging current rates, and determining the maximum charging current rate allowed without the occurrence of lithium deposition; obtaining the current charging rate; and adjusting the current charging rate according to the maximum charging current rate allowed without the occurrence of lithium deposition. The present invention can adjust the charging current rate to achieve non-lithium deposition control.

Description

A lithium-ion battery non-lithium deposition control method and system

Technical Field

The present invention relates to the field of fast charging of power batteries, and in particular to a lithium-ion battery non-lithium plating control method and system.

Background Art

Vehicle electrification has become one of the mainstream trends in the current development of the automotive industry, and lithium-ion batteries have become the mainstream choice for on-board power batteries for electric vehicles due to their advantages in energy density, volume density, cycle life, and output voltage. Since the energy density of lithium-ion batteries is much lower than that of traditional fossil fuels, consumers are increasingly demanding fast-charging technology for power batteries due to the "range anxiety". However, existing studies have shown that due to the occurrence of lithium plating at the negative electrode, fast charging of batteries often comes at the expense of battery life and reduced battery safety. Therefore, achieving lithium plating-free control of lithium-ion batteries under fast-charging conditions, thereby suppressing safety hazards and reduced battery life, is a key technology that urgently needs to be broken through for the further development of electric vehicles.

At present, in engineering, there are two main ways to achieve lithium-free control under fast charging.

One is to find new electrode materials and electrolyte materials with good performance through the development of battery materials, such as the preparation of low tortuosity electrodes and electrolyte additives, which can increase the maximum current rate that the battery can withstand and reduce the capacity decay of the battery during fast charging. However, the research and development of new materials is often very difficult, and as a multi-material system, the improvement and upgrade of one material requires corresponding adjustments to other materials to ensure that the battery has excellent comprehensive performance. At the same time, the commercialization process of new materials involves the layout of the industrial chain, which is quite costly.

The second is to improve the charging strategy of lithium batteries, and shorten the charging time on the basis of ensuring that the battery does not have abnormal lithium deposition. The most traditional charging method is constant current-constant voltage (CC-CV) charging. On this basis, researchers have proposed a multi-level constant current (MCC) charging strategy, which uses multi-level segmented constant current to increase the current in the initial charging stage to reduce the charging time, and uses a smaller current at the end of charging to prevent lithium deposition. The constant power (CP) charging strategy is similar to the multi-level constant current (MCC). In the early stage of charging, the charging current is large due to the low battery voltage. As the battery terminal voltage increases, the charging current will continue to decrease to prevent lithium deposition at the end. The pulse charging (PC) strategy uses intermittent voltage pulses for charging, which can leave sufficient relaxation time for the electrochemical reaction inside the battery, increase the upper limit of the charging current that the battery can accept, and achieve the purpose of fast charging without lithium deposition. Compared with the research and development of new materials, the improvement of charging methods is easier to achieve in engineering, but the current mainstream improved charging strategies are mostly passive charging strategies. These charging protocols are relatively simple, will not be actively adjusted according to the feedback of the battery during charging, and lack the ability to adapt to the charging environment. When the ambient temperature drops, the passive charging method can only continue to charge according to the preset current and power. At this time, the chemical reaction conditions inside the battery have changed. This type of passive charging method is prone to lithium precipitation.

Summary of the invention

The purpose of the present invention is to provide a lithium-ion battery non-lithium deposition control method and system to solve the problem that passive charging methods easily lead to lithium deposition.

To achieve the above object, the present invention provides the following solutions:

A lithium-ion battery non-lithium deposition control method, comprising:

The correction items of lithium precipitation reaction, SEI film growth and battery charge and discharge temperature are introduced to establish an electrochemical aging model of the battery; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation and the lithium ion flow density during lithium deposition; the battery charge and discharge temperature is determined by ohmic heat, reaction heat and the heat convection dissipation process of the battery to the outside world;

In the temperature range and the charging current rate range, a plurality of simulation operating points are set according to the temperature interval and the charging current rate interval respectively;

Based on the electrochemical aging model, pre-simulation of battery charging under multiple working conditions is performed according to the simulation working condition points to determine the lithium deposition thickness variation curve and the overpotential curve at the negative electrode-diaphragm under the corresponding working conditions;

Obtain the actual ambient temperature and actual charging rate during the actual charging process;

Based on the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve, two temperature operating points adjacent to the actual temperature environment are determined, and the maximum charging current ratio corresponding to the temperature operating points is extracted;

According to the two maximum charging current rates, the actual ambient temperature is used as the fixed temperature condition of the electrochemical aging model to perform a parameterized scan on the charging rate to determine the maximum charging current rate allowed at the actual ambient temperature without causing lithium deposition;

Get the current charging rate;

The maximum charging current rate allowed without causing lithium plating is compared with the current charging rate, and the current charging rate is adjusted.

Optionally, the intercalation ion flow density of the lithium ions entering the negative electrode particles is:

Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles.

Optionally, the lithium ion flow density during the formation of the SEI is:

Wherein, j _SEI is the lithium ion flow density during SEI formation; a _s is the relative specific surface area; n is the lithium ion charge number; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential.

Optionally, the lithium ion flow density during the lithium deposition is:

Wherein, j _Pl is the lithium ion flow density during lithium deposition; k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential.

Optionally, the battery temperature during charging and discharging is:

Among them, mcell is the mass of the battery; ccell is the specific heat capacity of the battery; L is the thickness of the single-layer battery material; is the heat of reaction; for ohmic heat; The heat is dissipated by convection.

Optionally, comparing the maximum charging current rate allowed without causing lithium plating with the current charging rate and adjusting the current charging rate specifically includes:

Determine whether the current charging rate is less than 0.97 times the maximum charging current rate allowed without causing lithium deposition, and obtain a first determination result;

If the first judgment result is yes, the current charging rate is increased to 0.98 times the maximum charging current rate allowed without causing lithium deposition;

If the first judgment result is no, determine whether the current charging rate is greater than 0.99 times the maximum charging current rate allowed without causing lithium deposition, and obtain a second judgment result;

If the second judgment result is yes, the current charging rate is reduced to 0.98 times the maximum charging current rate allowed without causing lithium deposition;

If the second judgment result is no, charging continues at the current charging rate.

A lithium-ion battery non-lithium deposition control system, comprising:

The electrochemical aging model establishment module is used to introduce the correction items of lithium precipitation reaction, SEI film growth and the temperature of the battery during charging and discharging to establish the electrochemical aging model of the battery; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation and the lithium ion flow density during lithium deposition; the temperature of the battery during charging and discharging is determined by the ohmic heat, reaction heat and the heat convection dissipation process of the battery to the outside world;

A simulation operating point setting module is used to set multiple simulation operating points in the temperature range and the charging current rate range according to the temperature interval and the charging current rate interval respectively;

A lithium deposition thickness variation curve and a negative electrode-diaphragm overpotential curve determination module is used to perform a multi-condition battery charging pre-simulation based on the electrochemical aging model and the simulation operating point to determine the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve under the corresponding operating condition;

The actual ambient temperature and actual charging rate acquisition module is used to obtain the actual ambient temperature and actual charging rate during the actual charging process;

A maximum charging current rate extraction module is used to determine two temperature operating points adjacent to the actual temperature environment based on the lithium deposition thickness change curve and the negative electrode-diaphragm overpotential curve, and extract the maximum charging current rate corresponding to the temperature operating points;

A maximum charging current rate determination module that does not cause lithium deposition is used to perform a parameterized scan of the charging rate based on the two maximum charging current rates and take the actual ambient temperature as the fixed temperature condition of the electrochemical aging model to determine the maximum charging current rate that does not cause lithium deposition at the actual ambient temperature;

The current charging rate acquisition module is used to obtain the current charging rate;

The current charging rate adjustment module is used to compare the maximum charging current rate allowed without causing lithium plating with the current charging rate, and adjust the current charging rate.

Optionally, the intercalation ion flow density of the lithium ions entering the negative electrode particles is:

Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles.

Optionally, the lithium ion flow density during the formation of the SEI is:

Wherein, j _SEI is the lithium ion flow density during SEI formation; a _s is the relative specific surface area; n is the lithium ion charge number; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential.

Optionally, the lithium ion flow density during the lithium deposition is:

Wherein, j _Pl is the lithium ion flow density during lithium deposition; k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: a lithium-ion battery non-lithium deposition control method and system provided by the present invention introduces correction terms for lithium deposition reaction, SEI film growth and battery charging and discharging temperature to establish an electrochemical aging model of the battery. The electrochemical model can simulate the lithium deposition reaction inside the battery during charging, and use the overpotential at the negative electrode-diaphragm to determine whether lithium deposition will occur; the electrochemical model simulates the growth of the lithium deposition film during charging, and can also simulate the continuous accumulation of lithium deposition during the cyclic charging and discharging of the lithium battery; the offline simulation results are used to determine whether lithium deposition will occur in the actual charging process under the same working condition, and further based on the lithium deposition-free reference working condition given by the offline simulation, the charging current rate is adjusted to achieve lithium deposition-free control.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of a lithium-ion battery non-lithium deposition control method provided by the present invention;

FIG2 is a graph showing a thickness variation curve of lithium deposition provided by the present invention;

FIG3 is a graph showing an overpotential curve at the negative electrode-diaphragm provided by the present invention;

FIG4 is a flow chart of the lithium-ion battery non-lithium deposition control method provided by the present invention applied in an actual operation process;

FIG5 is a structural diagram of a lithium-ion battery non-lithium deposition control system provided by the present invention.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, 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 creative work are within the scope of protection of the present invention.

The purpose of the present invention is to provide a lithium-ion battery non-lithium deposition control method and system, which can adjust the charging current ratio to achieve non-lithium deposition control.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a flow chart of a lithium-ion battery non-lithium deposition control method provided by the present invention. As shown in FIG. 1 , a lithium-ion battery non-lithium deposition control method comprises:

Step 101: Introduce correction items for lithium plating reaction, SEI film growth, and battery charge and discharge temperature to establish an electrochemical aging model for the battery; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation, and the lithium ion flow density during lithium deposition; the battery charge and discharge temperature is determined by ohmic heat, reaction heat, and the thermal convection dissipation process of the battery to the outside world.

A pseudo-two-dimensional model (P2D model) is used to establish an electrochemical aging model for the battery. The P2D model takes into account the charge transfer and material transport inside the battery along the electrode thickness direction (x) and within the solid particles (r), and couples the electrochemical reactions on the surface of the active material particles through the Butler-Volmer relationship. In addition, correction terms for lithium precipitation reaction and solid electrolyte interface (SEI) film growth are introduced into the P2D model, that is, side reactions that compete with lithium intercalation reactions during charging are introduced to characterize the aging phenomenon of lithium batteries.

The relevant governing equations of the P2D electrochemical model are:

Where _i0 is the concentration-dependent exchange current density:

Formulas (1) and (2) are Butler-Volmer kinetic equations, where j _tot is the lithium ion flow density of the entire lithium battery, α is the symmetry coefficient of the reaction, η is the electrochemical overpotential, k is the reaction rate constant, _ce is the concentration of Li ⁺ in the electrolyte, _cs is the concentration of Li ⁺ in the active material, c _max is the maximum concentration of Li ⁺ in the active material, F is the Faraday constant; R is the universal gas constant; T is the actual ambient temperature; the diffusion of lithium ions in spherical active material particles is described by Fick's law under the radial coordinate r:

Where _Ds is the solid phase diffusion coefficient.

In the electrolyte, the transport of lithium ions should consider both diffusion and migration:

In the formula, ε is the liquid volume fraction, is the effective diffusion coefficient of the liquid phase, _tp is the migration coefficient of lithium ions in the liquid phase, and a _s is the relative specific surface area.

The variation law of electromotive force in the liquid phase of lithium-ion batteries can be expressed by the modified Ohm's law, which is:

Where κ ^eff is the effective conductivity of the liquid phase, x is the linear coordinate orthogonal to the planar electrode area, φ _e is the liquid phase potential, and _ie is the liquid phase current density.

Similarly, Ohm's law in the solid phase can be described as:

Where ^σeff is the solid phase effective conductivity, _φs is the solid phase potential, and i _s is the solid phase current density.

In addition to the reaction current density satisfying the Butler-Volmer equation, the solid particles and the electrolyte must satisfy the basic rule of charge conservation. The charge conservation formulas for the solid phase and the liquid phase are:

In addition, in order to establish the connection between lithium ion deposition and SEI film growth and lithium battery cycle aging, two correction terms are introduced in the P2D model (hereinafter referred to as the model), in which the two reactions compete with the intercalation reaction during charging. The current density j _tot of the overall reaction can be redefined as:

j _tot ＝j _In +j _Pl +j _SEI (9)

Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles, _jSEI is the lithium ion flow density during SEI formation, and _jPl is the lithium ion flow density during lithium deposition.

The Butler-Volmer relationship of intercalation current can be used to obtain the intercalation current density formula for lithium ions entering the negative electrode particles as follows:

Where, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles. In the present invention, it is considered that the SEI film reaction is irreversible, and no secondary SEI film is generated on the surface of lithium deposition. When only the negative electrode Butler-Volmer is considered, the SEI film generation formula is as follows:

Where a _s is the relative specific surface area; n is the charge number of lithium ions; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential.

The present invention assumes that no lithium dissolution occurs and no "dead lithium" is generated in the reaction. The expression of lithium deposition in the model is similar to SEI film growth, and its formula is as follows:

Where k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential.

After completing the battery aging behavior modeling, the present invention couples a 0-dimensional thermal model in P2D to simulate the self-heating phenomenon during battery charging, so that the battery temperature change during simulation is closer to the actual situation. The formula for ohmic heat is as follows:

The above formula is the heat generation power per unit length. The first term on the right side of the equation is the ohmic heat from the solid electrode, and the second term is the ohmic heat from the electrolyte. For Ohmic heat, is the solid phase potential gradient; is the liquid phase potential gradient; is the gradient of the natural logarithm of the lithium ion concentration in the liquid phase; the effective ion diffusion conductivity of the electrolyte for:

In addition to ohmic heat, there is also reaction heat from the chemical reaction process during battery charging and discharging. The formula is as follows:

In the formula is the reaction heat, i _loc is the local reaction current.

In addition to heat generation, the battery also has heat dissipation. The heat convection dissipation formula of the battery surface to the environment is as follows:

In the above formula, is the heat dissipation by convection, h is the convection heat transfer coefficient, T is the absolute temperature of the battery, and _Tamb is the ambient temperature. Combining the ohmic heat, reaction heat and heat dissipation of the battery to the outside world, the temperature rise during battery charging and discharging can be expressed as:

In the above formula, m _cell and c _cell are the mass and specific heat capacity of the battery respectively, and L is the thickness of the single-layer battery material.

Step 102: setting a plurality of simulation operating points in the temperature range and the charging current rate range according to the temperature interval and the charging current rate interval respectively.

In the temperature range of -10℃～50℃, a simulation operating point is set every 5℃; in the charging current rate range of 0.5C-3C (1C is the rated current of the lithium battery), a simulation operating point is set every 0.5C, for a total of 78 groups (13×6) of simulations. The lithium deposition thickness change curve and the overpotential curve at the negative electrode-diaphragm under the corresponding working conditions are obtained, as shown in Figures 2-3. According to the model established by the present invention, it can be considered that when the overpotential η is less than the black dotted line 0V in Figure 3, lithium deposition will occur inside the battery.

Step 103: Based on the electrochemical aging model, pre-simulation of battery charging under multiple operating conditions is performed according to the simulation operating points to determine the lithium deposition thickness variation curve and the overpotential curve at the negative electrode-diaphragm under the corresponding operating conditions.

Step 104: Obtain the actual ambient temperature and the actual charging rate during the actual charging process.

Step 105: Based on the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve, two temperature operating points adjacent to the actual temperature environment are determined, and the maximum charging current ratio corresponding to the temperature operating points is extracted.

The ambient temperature T is obtained through the temperature sensor, and then the current charging current rate I _c is read from the charging device. According to the actual ambient temperature obtained by the sensor, the upper and lower adjacent temperature operating points T _a and T _b are found in the simulation results. Assuming that T is 18°C, its adjacent temperature operating points are T _a = 15°C and T _b = 20°C. Then extract the maximum charging current rate corresponding to the adjacent temperature operating points and The ambient temperature T is used as the fixed temperature condition in the model. and A rate condition is set every 0.05C, and a parameterized scan of the charging rate is performed to search for the maximum charging current rate I _ref allowed without lithium deposition at temperature T, which is used as a reference for subsequent lithium deposition-free control.

Step 106: Based on the two maximum charging current rates, the actual ambient temperature is used as the fixed temperature condition of the electrochemical aging model to perform a parameterized scan on the charging rate to determine the maximum charging current rate allowed without causing lithium deposition at the actual ambient temperature.

Step 107: Obtain the current charging rate.

Step 108: Compare the maximum charging current rate allowed without causing lithium plating with the current charging rate, and adjust the current charging rate.

The step 108 specifically includes: determining whether the current charging rate is less than 0.97 times the maximum charging current rate allowed without lithium deposition, and obtaining a first judgment result; if the first judgment result is yes, increasing the current charging rate to 0.98 times the maximum charging current rate allowed without lithium deposition; if the first judgment result is no, determining whether the current charging rate is greater than 0.99 times the maximum charging current rate allowed without lithium deposition, and obtaining a second judgment result; if the second judgment result is yes, reducing the current charging rate to 0.98 times the maximum charging current rate allowed without lithium deposition; if the second judgment result is no, continuing charging at the current charging rate.

FIG4 is a flow chart of the lithium-ion battery non-lithium deposition control method provided by the present invention applied in the actual operation process. As shown in FIG4, the maximum current rate I _ref given by the model is compared with the current charging rate I _c to determine whether the current rate should be increased or decreased in the future. Because there are measurement errors in the sensor, and the current controlled by the charging device will also produce a certain deviation, a 2% current rate redundancy is set in the present invention to prevent the accidental occurrence of lithium deposition. At the same time, a 1% fluctuation amplitude is set for the control strategy to speed up the convergence speed of the control algorithm at I _ref , prevent current jitter, and thereby improve the robustness of the control algorithm. The specific judgment process is as follows:

1) When I _c ＜0.97I _ref , increase the charging current rate to 0.98I _ref ;

2) When I _c > 0.99I _ref , reduce the charging current rate to 0.98I _ref .

FIG5 is a structural diagram of a lithium-ion battery non-lithium deposition control system provided by the present invention. As shown in FIG5 , a lithium-ion battery non-lithium deposition control system includes:

The electrochemical aging model establishment module 501 is used to introduce correction items of lithium precipitation reaction, SEI film growth and battery charge and discharge temperature to establish the battery electrochemical aging model; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation and the lithium ion flow density during lithium deposition; the battery charge and discharge temperature is determined by ohmic heat, reaction heat and the thermal convection dissipation process of the battery to the outside world.

The simulation operating point setting module 502 is used to set a plurality of simulation operating points in the temperature range and the charging current rate range according to the temperature interval and the charging current rate interval respectively.

The lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve determination module 503 is used to perform a multi-condition battery charging pre-simulation based on the electrochemical aging model and the simulation operating point to determine the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve under the corresponding operating condition.

The actual ambient temperature and actual charging rate acquisition module 504 is used to acquire the actual ambient temperature and the actual charging rate during the actual charging process.

The maximum charging current rate extraction module 505 is used to determine two temperature operating points adjacent to the actual temperature environment based on the lithium deposition thickness variation curve and the overpotential curve at the negative electrode-diaphragm, and extract the maximum charging current rate corresponding to the temperature operating points.

The maximum charging current rate determination module 506 allowed without causing lithium deposition is used to perform a parameterized scan of the charging rate based on the two maximum charging current rates and take the actual ambient temperature as the fixed temperature condition of the electrochemical aging model to determine the maximum charging current rate allowed without causing lithium deposition at the actual ambient temperature.

The current charging rate acquisition module 507 is used to acquire the current charging rate.

The current charging rate adjustment module 508 is used to compare the maximum charging current rate allowed without causing lithium plating with the current charging rate, and adjust the current charging rate.

In practical applications, the intercalation ion flow density of the lithium ions entering the negative electrode particles is:

Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles.

In practical applications, the lithium ion flow density when the SEI is formed is:

Wherein, j _SEI is the lithium ion flow density during SEI formation; a _s is the relative specific surface area; n is the lithium ion charge number; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential.

In practical applications, the lithium ion flow density during the lithium deposition is:

Wherein, j _Pl is the lithium ion flow density during lithium deposition; k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential.

The a priori model of the present invention is a reduced-order model based on electrochemical principles, has good adaptability to different battery material systems, and has better interpretability and transferability than non-physical models; the signal input of the present invention is based on the external signal characteristics of the battery, and there is no need to introduce additional hardware such as reference electrodes during the signal acquisition process; the present invention determines whether lithium precipitation occurs by predicting the overpotential at the negative electrode-diaphragm of the battery under different operating conditions. Compared with traditional imaging characterization methods, this method has more practical engineering application value on large mobile platforms such as electric vehicles.

The present invention monitors the overpotential at the negative electrode-diaphragm of the battery to determine in real time whether negative electrode lithium deposition occurs, and controls the charging conditions accordingly, thereby achieving fast charging of the battery without lithium deposition, reducing the risk of thermal runaway, and providing guidance for safe and efficient lithium-ion battery fast charging strategies. The method and system provided by the present invention can solve the problem of reduced battery life and increased risk of thermal runaway caused by negative electrode lithium deposition in lithium-ion batteries when charging at high current rates and extreme temperatures.

In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims (3)

1. A lithium-ion battery non-lithium deposition control method, characterized in that it includes: The correction items of lithium precipitation reaction, SEI film growth and battery charge and discharge temperature are introduced to establish the electrochemical aging model of the battery; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation and the lithium ion flow density during lithium deposition; the battery charge and discharge temperature is determined by ohmic heat, reaction heat and the heat convection dissipation process of the battery to the outside world; the intercalation ion flow density of lithium ions entering the negative electrode particles is: Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles; The lithium ion flow density during the formation of the SEI is: Wherein, j _SEI is the lithium ion flow density when SEI is formed; a _s is the relative specific surface area; n is the number of lithium ion charges; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential; The lithium ion flow density during the lithium deposition is: Wherein, j _Pl is the lithium ion flow density during lithium deposition; k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential; The temperature of the battery during charging and discharging is: Among them, mcell is the mass of the battery; ccell is the specific heat capacity of the battery; L is the thickness of the single-layer battery material; is the heat of reaction; for ohmic heat; For heat convection dissipation; In the temperature range and the charging current rate range, a plurality of simulation operating points are set according to the temperature interval and the charging current rate interval respectively; Based on the electrochemical aging model, pre-simulation of battery charging under multiple working conditions is performed according to the simulation working condition points to determine the lithium deposition thickness variation curve and the overpotential curve at the negative electrode-diaphragm under the corresponding working conditions; Obtain the actual ambient temperature and actual charging rate during the actual charging process; Based on the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve, two temperature operating points adjacent to the actual ambient temperature are determined, and the maximum charging current ratio corresponding to the temperature operating points is extracted; According to the two maximum charging current rates, the actual ambient temperature is used as the fixed temperature condition of the electrochemical aging model to perform a parameterized scan on the charging rate to determine the maximum charging current rate allowed at the actual ambient temperature without causing lithium deposition; Get the current charging rate; The maximum charging current rate allowed without causing lithium plating is compared with the current charging rate, and the current charging rate is adjusted. 2. The lithium-ion battery non-lithium deposition control method according to claim 1, characterized in that the comparison of the maximum charging current rate allowed without lithium deposition and the current charging rate, and adjusting the current charging rate, specifically includes: Determine whether the current charging rate is less than 0.97 times the maximum charging current rate allowed without causing lithium deposition, and obtain a first determination result; If the first judgment result is yes, the current charging rate is increased to 0.98 times the maximum charging current rate allowed without causing lithium deposition; If the first judgment result is no, determine whether the current charging rate is greater than 0.99 times the maximum charging current rate allowed without causing lithium deposition, and obtain a second judgment result; If the second judgment result is yes, the current charging rate is reduced to 0.98 times the maximum charging current rate allowed without causing lithium deposition; If the second judgment result is no, charging continues at the current charging rate. 3. A lithium-ion battery non-lithium deposition control system, characterized in that it includes: The electrochemical aging model establishment module is used to introduce the correction terms of lithium precipitation reaction, SEI film growth and the temperature during battery charging and discharging to establish the electrochemical aging model of the battery; the electrochemical aging model is determined by the intercalation ion flow density of lithium ions entering the negative electrode particles, the lithium ion flow density during SEI formation and the lithium ion flow density during lithium deposition; the battery charging and discharging temperature is determined by ohmic heat, reaction heat and the heat convection dissipation process of the battery to the outside world; the intercalation ion flow density of lithium ions entering the negative electrode particles is: Wherein, _jIn is the intercalation ion flow density of lithium ions entering the negative electrode particles; _kIn is the reaction rate of lithium ions entering the negative electrode particles; _cE is the concentration of Li ⁺ in the electrolyte, is the lithium ion concentration on the surface of the negative electrode particles; c _max is the maximum concentration of Li ⁺ in the active material; F is the Faraday constant; α is the symmetry coefficient of the reaction; R is the molar gas constant; T is the actual ambient temperature; η _In is the overpotential for lithium ions to enter the negative electrode particles; The lithium ion flow density during the formation of the SEI is: Wherein, j _SEI is the lithium ion flow density when SEI is formed; a _s is the relative specific surface area; n is the number of lithium ion charges; k _SEI is the SEI growth reaction rate; η _SEI is the SEI growth reaction overpotential; The lithium ion flow density during the lithium deposition is: Wherein, j _Pl is the lithium ion flow density during lithium deposition; k _Pl is the lithium deposition reaction rate; η _Pl is the lithium deposition reaction overpotential; The temperature of the battery during charging and discharging is: Among them, mcell is the mass of the battery; ccell is the specific heat capacity of the battery; L is the thickness of the single-layer battery material; is the heat of reaction; for ohmic heat; For heat convection dissipation; A simulation operating point setting module is used to set multiple simulation operating points in the temperature range and the charging current rate range according to the temperature interval and the charging current rate interval respectively; A lithium deposition thickness variation curve and a negative electrode-diaphragm overpotential curve determination module is used to perform a multi-condition battery charging pre-simulation based on the electrochemical aging model and the simulation operating point to determine the lithium deposition thickness variation curve and the negative electrode-diaphragm overpotential curve under the corresponding operating condition; The actual ambient temperature and actual charging rate acquisition module is used to obtain the actual ambient temperature and actual charging rate during the actual charging process; A maximum charging current rate extraction module is used to determine two temperature operating points adjacent to the actual ambient temperature based on the lithium deposition thickness variation curve and the overpotential curve at the negative electrode-diaphragm, and extract the maximum charging current rate corresponding to the temperature operating points; A maximum charging current rate determination module that does not cause lithium deposition is used to perform a parameterized scan of the charging rate based on the two maximum charging current rates and take the actual ambient temperature as the fixed temperature condition of the electrochemical aging model to determine the maximum charging current rate that does not cause lithium deposition at the actual ambient temperature; The current charging rate acquisition module is used to obtain the current charging rate; The current charging rate adjustment module is used to compare the maximum charging current rate allowed without causing lithium plating with the current charging rate, and adjust the current charging rate.