A calculation method and application of the optimal cycle number of electric vehicles

Abstract

The present invention discloses a method for quickly and accurately calculating the optimal cycle number of an electric vehicle. Under specific conditions, such as the charge and discharge voltages of the positive and negative electrodes, the specific capacity, the average coulombic efficiency of the battery, and the proportion of electrode active materials, the optimal cycle number of an electric vehicle can be quickly and accurately calculated. The present invention theoretically calculates the optimal cycle number of an electric vehicle, helps to understand the ideal and actual performance of different electric vehicles, and provides a certain theoretical reference basis for designing and selecting appropriate electric vehicle operating modes.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle batteries, and in particular to a method for rapidly calculating the optimal cycle number of an electric vehicle. Background Art

[0002] In recent years, with the advancement of science and society, energy demand has continued to grow, and environmental crises have intensified. New energy vehicles (NEVs) produced by companies like Tesla have rapidly entered the market. While different EVs have varying performance, power consumption, and other parameters, battery life and service life are the most important performance parameters.

[0003] Alkali metals, with their extremely low redox potential and high specific capacity, easily meet the requirements of high-energy-density energy storage devices, thereby enabling longer driving ranges for electric vehicles. However, the utilization rate of alkali metals and the number of battery cycles can also affect vehicle performance. Therefore, calculating the appropriate number of cycles for electric vehicles is crucial.

[0004] Theoretical calculation of the optimal number of cycles for different electric vehicles helps to understand the ideal and actual performance of different electric vehicles, and provides a certain theoretical reference basis for designing and selecting appropriate electric vehicle operation modes. Summary of the Invention

[0005] In view of the key issues of the background technology, the purpose of the present invention is to provide a method for quickly and accurately calculating the optimal number of cycles of an electric vehicle.

[0006] A method for calculating the optimal number of cycles of an electric vehicle comprises the following steps:

[0007] 1) Given the mileage, determine parameters such as friction coefficient, wind resistance, battery type, and range based on the type of electric vehicle;

[0008] 2) Determine the positive and negative electrode materials, obtain parameters such as the charge and discharge voltage, specific capacity, average coulombic efficiency of the battery, and the proportion of electrode active materials of the positive and negative electrodes, and derive the formula for the maximum number of cycles of electric vehicles;

[0009] 3) Substitute the above data into the formula to calculate the formula for the number of electric vehicle cycles, and perform functional correlation between the formula for the maximum number of electric vehicle cycles and the formula for the number of electric vehicle cycles to obtain the optimal number of cycles.

[0010] The types of electric vehicles described in step 1) include but are not limited to pure electric vehicles produced by manufacturers such as Tesla, BYD, and Toyota.

[0011] The friction coefficient in step 1) refers to the friction coefficient between the wheels of the car and the ground during driving, which can be 0.2-0.8, preferably 0.4-0.6, and most preferably 0.6.

[0012] The wind resistance in step 1) refers to the component of the air force in the direction of travel that the car is subjected to when traveling in a straight line, which can be 0.2-0.8, preferably 0.3-0.7, and most preferably 0.4-0.6.

[0013] There are three main types of batteries described in step 1): conventional batteries are type X, lithium-rich positive electrodes matched with excess lithium metal or negative electrodes containing reserve lithium are type Y, and lithium-poor positive electrodes matched with excess lithium metal or negative electrodes containing reserve lithium are type Z.

[0014] The electric vehicle endurance value mentioned in step 1) refers to the maximum mileage that the electric vehicle battery can reach after being fully charged on average.

[0015] The specific capacity of the positive electrode and the negative electrode described in step 2) is the specific capacity at a certain current density.

[0016] The certain current density may be 0.1-50C, preferably 1-10C, and most preferably 1C.

[0017] The positive electrode and negative electrode voltages described in step 2) are the average potentials to lithium at the same current density as the specific capacity.

[0018] The average coulombic efficiency of the battery in step 2) refers to the percentage of the discharge capacity to the charge capacity per cycle after the battery has been cycled a certain number of times.

[0019] The electrode active material in step 2) may account for 30%-90%, preferably 50%-80%, and most preferably 60%-70%.

[0020] The formula for the maximum number of cycles of the electric vehicle described in step 2) is as follows:

[0021]

[0022] Where: m is the lithium metal utilization rate, is the average coulombic efficiency per cycle of electric vehicle batteries under ideal conditions.

[0023] The formula for the number of cycles of the electric vehicle described in step 3) is valid under the condition that the number of cycles of the electric vehicle is less than or equal to the maximum number of cycles of the electric vehicle.

[0024] The formula for the number of electric vehicle cycles described in step 3) is as follows:

[0025]

[0026] Where: n is the number of cycles, L is the total mileage, The average mileage that the battery can reach per lap.

[0027] The It can be obtained by the following formula:

[0028]

[0029]

[0030] P=F×v

[0031]

[0032]

[0033] in: is the average mileage that the battery can run per lap; W is the energy density of the battery cell; γ is the correction factor; m 电池 is the weight of the electric vehicle battery; P is the power consumption of the entire vehicle, in watts (W); F is the resistance of the entire electric vehicle during driving, in N; v is the speed of the vehicle, in m / s; m 车 is the vehicle weight, in N; f 摩 is the drag coefficient, dimensionless; C D is the air resistance coefficient, dimensionless; θ is the inclination angle between the road surface and the horizontal plane, in rad; A is the frontal area of the vehicle, in m 2 .

[0034] The energy density of the battery cell can be obtained by the following formula:

[0035]

[0036] Where: W is the energy density of the battery cell, C is the specific capacity of the positive electrode, is the average coulombic efficiency of the battery, Q is the specific capacity of the negative electrode, f is the proportion of active material in the electrode, and E is the voltage difference between the positive and negative electrodes. Substituting formulas (3) and (5) into (2) yields the following formula:

[0037]

[0038] can be simplified to:

[0039]

[0040] in:

[0041]

[0042] For X type batteries:

[0043]

[0044] For Y type batteries:

[0045]

[0046] Where: Z is the theoretical capacity of lithium metal, and m is the utilization rate of lithium metal.

[0047] Substituting formula (9) into (7) yields the following formula:

[0048]

[0049] in:

[0050]

[0051]

[0052] can be simplified to:

[0053]

[0054]

[0055] Further simplified to:

[0056]

[0057] For Z type batteries:

[0058] Q=Z×m (12)

[0059] Where: Z is the theoretical capacity of lithium metal, and m is the utilization rate of lithium metal.

[0060] Substituting formula (12) into (7) yields the following formula:

[0061]

[0062] in:

[0063]

[0064]

[0065] so:

[0066]

[0067] The optimal number of cycles of the electric vehicle described in step 3) is obtained by plotting the two sets of functions of formula (1) and formula (9). The intersection of the two sets of functions is the optimal number of cycles of the electric vehicle. If the intersection value is not an integer, a larger integer value is taken.

[0068] The simplified formula and calculation method are intended to obtain a general calculation method for the optimal cycle number of electric vehicle batteries, simplify the code or program amount for new energy vehicle applications and theoretical calculations, and obtain the optimal cycle number of electric vehicle batteries for different parameters from an intuitive perspective.

[0069] The formula can quickly determine the utilization rate of the lithium metal negative electrode under a certain number of cycles, and can further infer the actual capacity of the battery at this time.

[0070] The formula is used to calculate the optimal cycle of electric vehicle batteries and to design suitable electric vehicles based on this result.

[0071] Compared with the prior art, the present invention has the following advantages and outstanding effects:

[0072] Compared to existing technologies, this invention offers the following advantages and significant effects: It can theoretically calculate the maximum and optimal cycle counts for different electric vehicles, allowing for intuitive data analysis to determine the most suitable operating mode for the electric vehicle. The required conditions and data are simple, direct, and convenient. This method is highly universal and can be applied to quickly determine the optimal cycle count for a single electric vehicle battery. This helps understand the ideal and actual performance of different electric vehicles, providing a theoretical basis for designing and selecting appropriate electric vehicle operating modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 is a calculation flow chart.

[0074] Figure 2 Coulomb efficiency diagram for the first 50 cycles of lithium cobalt oxide

[0075] Figure 3 Coulomb efficiency diagram for the first 30 cycles of lithium iron phosphate

[0076] Figure 4 The charge and discharge curve of lithium cobalt oxide in the first three cycles

[0077] Figure 5 The charge and discharge curve of lithium iron phosphate in the first three cycles DETAILED DESCRIPTION

[0078] The present invention will be described in detail below, but the present invention is not limited thereto.

[0079] Implementation Example 1

[0080] Taking Tesla Model 3 as an example, the vehicle weighs 16191kg and the battery weighs 9kg. The battery is a lithium iron phosphate battery with an energy density of 130Wh / kg. Substituting the main parameters into the formula, we can get:

[0081] γ=0.28

[0082]

[0083] so:

[0084] n=n 极大 =log 0.99989 0.8=2028

[0085] Comparative Example 1

[0086] If a battery with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode is used as the power source of an electric vehicle, then:

[0087] γ=0.28

[0088]

[0089]

[0090] The optimal number of cycles can be obtained by fitting the two curves into a graph.

[0091] Comparative Example 2

[0092] If a battery with lithium cobalt oxide as the positive electrode and lithium metal as the negative electrode is used as the power source of an electric vehicle,

[0093] γ=0.25

[0094]

[0095]

[0096] The optimal number of cycles can be obtained by fitting the two curves into a graph.

Claims

1. A method for calculating the optimal number of cycles of an electric vehicle, comprising the following steps: 1) Given the mileage, determine the friction coefficient, wind resistance, battery type, and range parameters based on the electric vehicle type; 2) Determine the positive and negative electrode materials, obtain the charge and discharge voltage, specific capacity, average coulombic efficiency of the battery, and electrode active material ratio parameters of the positive and negative electrodes, and derive the formula for the maximum number of cycles of the electric vehicle. The formula for the maximum number of cycles of the electric vehicle is as follows: Where: m is the lithium metal utilization rate, is the average coulombic efficiency per cycle of electric vehicle batteries under ideal conditions; 3) Substitute the above parameters into the formula to calculate the electric vehicle cycle number formula. The electric vehicle maximum cycle number formula and the electric vehicle cycle number formula are functionally related to obtain the optimal cycle number. The calculation formula is simplified by the following conventional calculation formula: P=F×v Where: L is the total mileage, is the average mileage that the battery can run per lap; W is the energy density of the battery cell; γ is the correction factor; m 电池 is the weight of the electric vehicle battery; P is the power consumption of the entire vehicle, in watts (W); F is the resistance of the entire electric vehicle during driving, in N; v is the speed of the vehicle, in m / s; m 车 is the vehicle weight, in N; f 摩 is the drag coefficient, dimensionless; C D is the air resistance coefficient, which is 0.4 to 0.6 and dimensionless; θ is the inclination angle between the road surface and the horizontal plane, in rad; A is the frontal area of the vehicle, in m 2 ; And because: Where: W is the energy density of the battery cell, γ is the correction coefficient, C is the specific capacity of the positive electrode, is the average coulombic efficiency of the battery, Q is the specific capacity of the negative electrode, f is the proportion of electrode active materials, E is the voltage difference between the positive and negative electrodes, Z is the theoretical capacity of the alkali metal, and m is the utilization rate of the alkali metal; 4) will be and The calculated results are plotted in a correlation graph, and the intersection of the two sets of functions is the optimal number of cycles for the electric vehicle. If the intersection value is not an integer, a smaller integer value is taken.

2. The method for calculating the optimal number of cycles of an electric vehicle according to claim 1, characterized in that: In step 1), the electric vehicle types include pure electric vehicles produced by Tesla, BYD, and Toyota; the friction coefficient refers to the friction coefficient between the wheels and the ground during driving; the wind resistance refers to the component of the air force acting on the car in the driving direction when it is driving in a straight line; there are three types of batteries, conventional batteries are X type, lithium-rich positive electrodes matched with excess lithium metal or negative electrodes containing reserve lithium are Y type, and lithium-poor positive electrodes matched with excess lithium metal or negative electrodes containing reserve lithium are Z type; the electric vehicle endurance value refers to the maximum mileage that the electric vehicle battery can reach after an average of one full charge.

3. The method for calculating the optimal number of cycles of an electric vehicle according to claim 1, characterized in that: In step 2), the positive electrode and negative electrode voltages are the average potentials to lithium at the same current density as the specific capacity; the positive electrode and negative electrode specific capacities are the specific capacities at a preset current density; and the average coulombic efficiency of the battery refers to the percentage of the average discharge capacity to the charge capacity per cycle after the battery has been cycled a certain number of times.

4. The method for calculating the optimal number of cycles of an electric vehicle according to claim 1, wherein: In step 3), the formula for the number of cycles of the electric vehicle is valid under the condition that the number of cycles is less than or equal to the maximum number of cycles of the electric vehicle.

5. The method for calculating the optimal number of cycles of an electric vehicle according to claim 1, wherein: In step 3), the calculation formula is applicable to X, Y and Z types, and the calculation formula can be simplified as follows: For X type batteries: For Y type batteries: Where: Z is the theoretical capacity of lithium metal, m is the utilization rate of lithium metal; Substituting in: in: For Z type batteries: Q=Z×m Where: Z is the theoretical capacity of lithium metal, m is the utilization rate of lithium metal; Substituting in: in:

6. The method for calculating the optimal cycle number of an electric vehicle according to claim 1 aims to obtain a general method for calculating the optimal cycle number of an electric vehicle battery, simplify the code or program amount for new energy vehicle applications and theoretical calculations, and obtain the optimal cycle number of electric vehicle batteries for different parameters from an intuitive perspective.

7. The formula of the method for calculating the optimal number of cycles of an electric vehicle according to claim 1 can quickly determine the utilization rate of the alkali metal negative electrode under a certain number of cycles, and can further infer the actual capacity of the battery at that time.

8. The method for calculating the optimal cycle number of an electric vehicle according to any one of claims 1 to 7 is used to calculate the optimal cycle number of an electric vehicle battery and design a suitable electric vehicle based on the result.

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