Lithium ion battery fault gas coverage adsorption and fault early warning method

Abstract

The invention relates to a lithium ion battery fault gas coverage adsorption and fault early warning method, and belongs to the technical field of battery health management. The method comprises the following steps: firstly, constructing a model of lithium ion battery fault gas molecules and an adsorbent magnesium antimonide (MgTe); then calculating the energy, the energy band gap, the shortest adsorption distance and the Millikan transfer charge condition of the fault gas adsorbed on the MgTe surface based on the density functional theory DFT; then considering the change trend of the adsorption energy, the energy band gap and the Millikan transfer charge along with the coverage of the fault gas, and obtaining the conductivity of the adsorption system based on the change of the energy band gap; and finally, obtaining a lithium ion battery fault danger index and CO desorption time based on the CO adsorption energy change. According to the method, accurate early warning of the lithium ion battery fault is realized according to the change of the adsorption property of the lithium ion battery to the fault gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery health management and relates to a lithium-ion battery fault gas covering adsorption and fault early warning method. Background Art

[0002] Lithium batteries are widely used in electric vehicles and new energy fields due to their high energy density and long cycle life. However, due to the limitations of component materials and the influence of the application environment, lithium-ion batteries themselves have safety hazards. When lithium-ion batteries encounter mechanical abuse, thermal abuse, and electrical abuse, they are prone to cause violent reactions inside the battery and quickly release a large amount of heat, leading to serious failures such as thermal runaway. Related studies have shown that a variety of toxic and harmful gases (mainly H2, CO, and CO2) are released during lithium-ion battery failure. Therefore, the detection of these characteristic gases is particularly suitable for providing early warning signals for lithium-ion battery failures, thereby ensuring the safe operation of lithium-ion batteries.

[0003] At present, two-dimensional materials are widely used in gas sensing development and application due to their flexible electron transport and good adsorption properties. Magnesium antimonide (MgTe) is widely used in catalysis and light-emitting devices due to its high hygroscopicity, environmental friendliness and low thermal conductivity. Based on the Dmol3 module, a model for optimizing lithium-ion battery fault gas and MgTe can be constructed. At the same time, based on DFT, key adsorption properties such as adsorption energy, band gap and Mulliken transfer charge can be calculated and analyzed, which is of great significance for conducting research on efficient adsorption of lithium-ion battery fault gas.

[0004] In addition, the existing adsorption energy calculation method lacks consideration of the fault gas coverage problem. In practical applications, the coverage area of ​​the fault gas on the adsorbent surface will affect the adsorption properties. Therefore, it is very important to obtain the variation trend of the adsorption properties with the fault gas coverage.

[0005] Therefore, it is necessary to design a new lithium-ion battery fault gas cover adsorption and fault warning method to cope with the shortcomings of the existing technology in order to solve or alleviate the above problems. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a lithium-ion battery fault gas cover adsorption and fault warning method. The method can achieve efficient adsorption of thermal runaway gas of lithium batteries, improve the limitations of the prior art that do not consider the ambient temperature, the difficulty of engineering implementation, and other problems, and can achieve accurate estimation of the health status of lithium batteries.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A lithium-ion battery fault gas cover adsorption and fault early warning method, the method comprising the following steps:

[0009] S1: Construct models of lithium-ion battery failure gas molecules and MgTe adsorbent; lithium-ion battery failure gas molecules include H2, CO and CO2;

[0010] S2: Based on density functional theory (DFT), the energy, band gap, shortest adsorption distance and Mulliken transfer charge of fault gas adsorbed on the MgTe surface were calculated;

[0011] S3: Calculate the variation trend of adsorption energy, band gap and Mulliken transfer charge with fault gas coverage;

[0012] S4: Based on the variation trend of the energy band gap with fault gas coverage, the conductivity of MgTe with increasing fault gas coverage is calculated, and the optimal adsorption gas is determined;

[0013] S5: Calculate the fault risk index of the lithium-ion battery and the desorption time of the optimal adsorbed gas, thereby achieving accurate early warning of lithium-ion battery failure.

[0014] Further, in S1, a model of lithium-ion battery fault gas and MgTe adsorbent is constructed based on the material simulation calculation software Materials Studio, and the formation energy E is calculated. f Judging the structural stability of MgTe:

[0015] E f =(E MgTe -xE Mg -yE Te ) / n

[0016] Among them, E MgTe represents the energy after MgTe structure optimization, E Mg and E Te represent the energy of a single Mg atom and a Te atom, respectively, and x, y, and n represent the number of Mg atoms, the number of Te atoms, and the total number of atoms in MgTe, respectively.

[0017] Further, in S2, the adsorption energy (E) of the fault gas adsorbed on the MgTe surface is calculated based on the DFT theory. ad ), Energy band gap (Energy band gap, E bg ) and Mulliken transfer charge (Q MC ), specifically comprising the following steps:

[0018] S21: Calculate the energy of lithium-ion battery failure gas and MgTe respectively, through E adCharacterization of MgTe's adsorption capacity for fault gases:

[0019] E ad =E MgTe / Gas -E MgTe -E Gas

[0020] Among them, E MgTe / gas represents the energy of fault gas adsorbed on the MgTe surface, E MgTe represents the energy of MgTe, E Gas Represents the energy of gas molecules from lithium-ion battery failure;

[0021] S22: Calculation of the band structure E of MgTe after adsorption of faulty gas bg :

[0022] E bg =|E CBM -E VBM |

[0023] Among them, E CBM and E VBM They represent the conduction band minimum and valence band maximum in the band structure respectively;

[0024] S23: Calculation of charge distribution Q of MgTe and adsorption model MC :

[0025] Q MC =Q MgTe -Q MgTe / Gas

[0026] Among them, Q MgTe and Q MgTe / Gas They represent the Mulliken charge of MgTe before and after adsorption of fault gas, respectively.

[0027] Further, in S3, the variation trends of adsorption energy, energy band gap and Mulliken transfer charge with fault gas coverage are calculated, which specifically includes the following steps:

[0028] S31: determining the fault gas coverage position according to the structural characteristics of the MgTe constructed in S1;

[0029] S32: According to E in S2 ad 、E bg and Q MC The calculation formula was used to obtain the variation curves of the three adsorption properties with the increase of H2, CO and CO2 coverage.

[0030] Further, in said S4, based on the variation trend of the energy band gap with the fault gas coverage, the conductivity of MgTe with the increase of the fault gas coverage is calculated, and the optimal adsorption gas is determined, which specifically includes the following steps:

[0031] S41: Based on E bg As the fault gas coverage changes, the conductivity δ of the adsorption system is calculated:

[0032] δ∝exp(-E bg / 2K B T)

[0033] Among them, exp(.) is the exponential operation, K B represents the Boltzmann constant, which is 1.381×10-23J / K, and T is the ambient temperature of the lithium battery;

[0034] S42: E according to H2, CO and CO2 bg The optimal adsorption gas can be determined by analyzing the changing trend of

[0035] Furthermore, in S5, the fault risk index of the lithium-ion battery and the desorption time of the optimal adsorbed gas are calculated to achieve early warning of lithium-ion battery faults, which specifically includes the following steps:

[0036] S51: Obtaining a corresponding relationship between the fault gas coverage rate and the temperature according to the content and composition of the fault gas released by the lithium-ion battery and the gas coverage position of MgTe in S1;

[0037] S52: Based on the variation trend of the adsorption energy of the optimal adsorbed gas, the corresponding desorption time is calculated:

[0038]

[0039] Among them, exp(.) is the exponential operation, f0 represents the test frequency, the unit is 10 12 s -1 , E ad-T represents the adsorption energy at different ambient temperatures;

[0040] S53: normalizing the adsorption energy at different ambient temperatures to obtain a risk index of lithium-ion batteries at different temperatures, so as to achieve fault warning of lithium-ion batteries:

[0041] Risk Index=(E ad-T -E ad-min ) / (E ad-max -E ad-min )

[0042] Among them, E ad-min represents the minimum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures, E ad-max Represents the maximum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures.

[0043] The beneficial effect of the present invention is that the magnesium antimonide (MgTe) constructed by the present invention exhibits a strong adsorption capacity for lithium-ion battery fault gases (H2, CO and CO2). At the same time, the influence of fault gas coverage on adsorption energy, band gap and Millikan transfer charge is considered, and the conductivity of MgTe is calculated based on the change in band gap. The results show the superiority of MgTe monolayer to high conductivity changes and sensing applications of CO gas. The adsorption energy under different CO coverage is correlated with temperature and normalized, and the fault risk index of lithium-ion batteries at different temperatures is calculated, thereby achieving accurate fault warning.

[0044] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0046] Figure 1 This is a flow chart of the method for gas covering adsorption and fault early warning of lithium-ion battery faults according to the present invention;

[0047] Figure 2 Optimized models for gas molecules and MgTe in lithium-ion battery failures;

[0048] Figure 3 is the variation trend of adsorption energy with fault gas coverage;

[0049] Figure 4 is the variation trend of the energy band gap with fault gas coverage;

[0050] Figure 5 is the variation trend of the Millikan transfer charge with the fault gas coverage;

[0051] Figure 6 is the failure risk index of lithium-ion batteries at different temperatures;

[0052] Figure 7 is the desorption time of CO gas at different temperatures. DETAILED DESCRIPTION

[0053] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0054] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0055] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0056] Figure 1 The present invention provides a lithium-ion battery fault gas cover adsorption and fault warning method, which comprises the following steps:

[0057] Step S1: Use the material simulation software Materials Studio to build a model of lithium-ion battery fault gas and MgTe adsorbent, and calculate the formation energy (E f ) to determine the structural stability of MgTe:

[0058] E f =(E MgTe -xE Mg -yE Te ) / n

[0059] Among them, E MgTe represents the energy after MgTe structure optimization, E Mg and E Terepresent the energy of a single Mg atom and a Te atom, respectively, and x, y, and n represent the number of Mg atoms, the number of Te atoms, and the total number of atoms in MgTe, respectively.

[0060] Optimized structure of fault gases and adsorbent MgTe in lithium-ion batteries Figure 2 As shown. H2, CO and CO2 are all linear structures, and the HH bond length is The C≡O bond length is The bond length of C=0 is The MgTe monolayer is an oblique hexagonal crystal, in which the Mg-Te bond length is The Te-Mg-Te bond angle is 117.711°. The formation energy of the MgTe monolayer is -2.52 eV, indicating the stability of the MgTe structure. The MgTe monolayer has four adsorption sites: Mg-Te bond position, Mg atom position, center position, and Te atom position. 1 to 7 represent the coverage positions of the fault gas on the MgTe monolayer.

[0061] Step S2: Calculate the adsorption energy (E) of the fault gas adsorbed on the MgTe surface based on DFT theory ad ), Energy band gap (Energy band gap, E bg ) and Mulliken transfer charge (Q MC ), specifically comprising the following steps:

[0062] S21: Calculate the energy of lithium-ion battery failure gas and MgTe respectively, through E ad Characterization of MgTe's adsorption capacity for fault gases:

[0063] E ad =E MgTe / Gas -E MgTe -E Gas

[0064] Among them, E MgTe / gas represents the energy of fault gas adsorbed on the MgTe surface, E MgTe represents the energy of MgTe, E Gas Represents the energy of gas molecules from lithium-ion battery failure;

[0065] S22: Calculation of the band structure E of MgTe after adsorption of faulty gas bg :

[0066] E bg =|E CBM -E VBM |

[0067] Among them, E CBM and EVBM They represent the conduction band minimum and valence band maximum in the band structure respectively;

[0068] S23: Calculation of charge distribution Q of MgTe and adsorption model MC :

[0069] Q MC =Q MgTe -Q MgTe / Gas

[0070] Among them, Q MgTe and Q MgTe / Gas They represent the Mulliken charge of MgTe before and after adsorption of fault gas, respectively.

[0071] Adsorption energy, band gap, Mulliken transfer charge and shortest adsorption distance (D) of fault gases in lithium-ion batteries adsorbed on MgTe surface l ) as shown in Table 1.

[0072] Table 1

[0073]

[0074] It can be seen from Table 1 that the E of H2 adsorbed on the MgTe surface ad 、E bg , Q MC and D l They are -1.551eV, 2.963eV, -0.003e and The adsorption property is the weakest among the three gases. Q MC The adsorption rates of CO and MgTe monolayers are close to each other, while CO has an advantage in the other adsorption indicators, indicating the strong selective adsorption of CO by MgTe monolayer.

[0075] Step S3: Calculate the variation trend of adsorption energy, energy band gap and Mulliken transfer charge with fault gas coverage, specifically including the following steps:

[0076] S31: determining the fault gas coverage position according to the structural characteristics of the MgTe constructed in S1;

[0077] S32: According to E in S2 ad 、E bg and Q MC The calculation formulas of the three adsorption properties were obtained with the increase of H2, CO and CO2 coverage.

[0078] E ads 、E bg and Q MC The changing trend of the gas coverage rate of three lithium-ion battery faults is as follows Figure 3 to Figure 5As shown. According to existing research, S1 is defined as the normal working stage of lithium-ion batteries (300K~350K), S2 is the thermal runaway fault triggering stage (350K~475K), and S3 is the thermal runaway fault stage (475K~575K). The results show that E ads The value of increases with the increase of gas coverage, among which CO has the largest increase of 144.79%. As the coverage of H2 and CO2 increases, the corresponding E bg The E after CO adsorption fluctuates between 2.926eV and 3.010eV and 2.868eV and 2.996eV, respectively. bg It gradually decreases with the increase of CO coverage. Q after adsorption of three gases MC As the coverage of the corresponding gas increases, it fluctuates within a certain range and there is no obvious change pattern.

[0079] Step S4: Based on the variation trend of the energy band gap with the fault gas coverage, the conductivity of MgTe with the increase of the fault gas coverage is calculated, and the optimal adsorption gas is determined, which specifically includes the following steps:

[0080] S41: Based on E bg As the fault gas coverage changes, the conductivity δ of the adsorption system is calculated:

[0081] δ∝exp(-E bg / 2K B T)

[0082] Among them, exp(.) is the exponential operation, K B represents the Boltzmann constant, which is 1.381×10-23J / K, and T is the ambient temperature of the lithium battery;

[0083] S42: Obtaining E of H2, CO and CO2 bg The changing law of can determine the optimal adsorption gas.

[0084] At a certain temperature, δ increases with E bg The decrease of increases. Figure 4 It can be seen that the δ of MgTe increases with the increase of CO, indicating that as the thermal runaway fault deepens, the conductivity of the MgTe monolayer changes more significantly, and thus the sensitivity to the change of CO is more sensitive. At the same time, the δ of MgTe fluctuates within a certain range with the increase of H2 and CO2, which is not conducive to the engineering application of material property changes. This also further illustrates the high conductivity change of MgTe monolayer to CO gas and its superiority in engineering application.

[0085] Step S5: Calculate the fault risk index of the lithium-ion battery and the desorption time of the optimal adsorbed gas, thereby realizing the fault warning of the lithium-ion battery, which specifically includes the following steps:

[0086] S51: Based on the research on the content and composition of gas released from lithium-ion battery faults and the gas coverage position of MgTe in S1, the mathematical correspondence between the fault gas coverage rate and the temperature is obtained;

[0087] S52: Based on the variation trend of the adsorption energy of the optimal adsorbed gas, the corresponding desorption time is calculated:

[0088]

[0089] Among them, exp(.) is the exponential operation, f0 represents the test frequency (10 12 s -1 ), E ad-T represents the adsorption energy at different ambient temperatures;

[0090] S53: normalize the adsorption energy at different ambient temperatures, and calculate the danger index of the lithium-ion battery at different temperatures, so as to realize the fault warning of the lithium-ion battery:

[0091] Risk Index=(E ad-T -E ad-min ) / (E ad-max -E ad-min )

[0092] Among them, E ad-min represents the minimum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures, E ad-max Represents the maximum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures.

[0093] The failure risk index of lithium-ion batteries at different temperatures is as follows: Figure 6 As shown, Figure 7 is the desorption time of CO on the MgTe monolayer surface at different temperatures. Table 2 gives the failure risk index of lithium-ion batteries and the CO desorption time at different temperatures.

[0094] Table 2

[0095]

[0096] The fault risk index maintains a good correspondence with the operating state of the lithium-ion battery. During normal operation, the risk index is low, and as the fault is triggered and progresses, the risk index gradually increases, and the lithium-ion battery fault warning is realized. In addition, the desorption time is very large throughout the entire cycle of the lithium-ion battery, indicating the stable adsorption of CO gas. The MgTe monolayer can be used as a powerful adsorbent for the fault gas CO of the lithium-ion battery, further ensuring the safe operation of the lithium-ion battery.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for gas cover adsorption and fault early warning of lithium ion battery fault, characterized in that: The method comprises the following steps: S1: Construct models of lithium-ion battery failure gas molecules and MgTe adsorbent; lithium-ion battery failure gas molecules include H2, CO and CO2; S2: Based on density functional theory (DFT), the energy, band gap, shortest adsorption distance and Mulliken transfer charge of fault gas adsorbed on the MgTe surface were calculated; S3: Calculate the variation trend of adsorption energy, band gap and Mulliken transfer charge with fault gas coverage; S4: Based on the variation trend of the energy band gap with fault gas coverage, the conductivity of MgTe with increasing fault gas coverage is calculated, thereby determining the optimal adsorption gas; S5: Calculate the fault risk index of the lithium-ion battery and the desorption time of the optimal adsorbed gas, thereby achieving accurate early warning of lithium-ion battery failure.

2. A lithium-ion battery fault gas cover adsorption and fault early warning method according to claim 1, characterized in that: In S1, a model of lithium-ion battery failure gas and MgTe adsorbent is constructed based on the material simulation calculation software Materials Studio, and the formation energy E is calculated. f Judging the structural stability of MgTe: E f =(E MgTe -xE Mg -yE Te ) / n Among them, E MgTe represents the energy after MgTe structure optimization, E Mg and E Te represent the energy of a single Mg atom and a Te atom, respectively, and x, y, and n represent the number of Mg atoms, the number of Te atoms, and the total number of atoms in MgTe, respectively.

3. A lithium-ion battery fault gas cover adsorption and fault early warning method according to claim 2, characterized in that: In S2, the adsorption energy (E) of the fault gas adsorbed on the MgTe surface is calculated based on the DFT theory. ad ), Energy band gap (Energy band gap, E bg ) and Mulliken transfer charge (Q MC ), specifically comprising the following steps: S21: Calculate the energy of lithium-ion battery failure gas and MgTe respectively, through E ad Characterization of MgTe's adsorption capacity for fault gases: AND ad =And MgTe / Gas -AND MgTe -AND Gas Among them, E MgTe / gas represents the energy of fault gas adsorbed on the MgTe surface, E MgTe represents the energy of MgTe, E Gas Represents the energy of gas molecules from lithium-ion battery failure; S22: Calculation of the band structure E of MgTe after adsorption of faulty gas bg : AND bg =|And CBM -AND VBM | Among them, E CBM and E VBM They represent the conduction band minimum and valence band maximum in the band structure respectively; S23: Calculation of charge distribution Q of MgTe and adsorption model MC : Q MC =Q MgTe -Q MgTe / Gas Among them, Q MgTe and Q MgTe / Gas They represent the Mulliken charge of MgTe before and after adsorption of fault gas, respectively.

4. A lithium-ion battery fault gas cover adsorption and fault early warning method according to claim 3, characterized in that: In said S3, the variation trend of adsorption energy, energy band gap and Mulliken transfer charge with fault gas coverage is calculated, which specifically includes the following steps: S31: determining the fault gas coverage position according to the structural characteristics of the MgTe constructed in S1; S32: According to E in S2 ad 、E bg and Q MC The calculation formula was used to obtain the variation curves of the three adsorption properties with the increase of H2, CO and CO2 coverage.

5. A lithium-ion battery fault gas cover adsorption and fault early warning method according to claim 4, characterized in that: In the S4, based on the variation trend of the energy band gap with the fault gas coverage, the conductivity of MgTe with the increase of the fault gas coverage is calculated, and the optimal adsorption gas is determined, which specifically includes the following steps: S41: Based on E bg As the fault gas coverage changes, the conductivity δ of the adsorption system is calculated: δ∝exp(-E bg / 2K B T) Among them, exp(.) is the exponential operation, K B represents the Boltzmann constant, which is 1.381×10-23J / K, and T is the ambient temperature of the lithium battery; S42: E according to H2, CO and CO2 bg The optimal adsorption gas can be determined by analyzing the changing trend of 6. A lithium-ion battery fault gas cover adsorption and fault early warning method according to claim 5, characterized in that: In the above S5, the fault risk index of the lithium-ion battery and the desorption time of the optimal adsorbed gas are calculated to realize the early warning of the lithium-ion battery fault, which specifically includes the following steps: S51: Obtaining a corresponding relationship between the fault gas coverage rate and the temperature according to the content and composition of the fault gas released by the lithium-ion battery and the gas coverage position of MgTe in S1; S52: Based on the variation trend of the adsorption energy of the optimal adsorbed gas, the corresponding desorption time is calculated: Among them, exp(.) is the exponential operation, f0 represents the test frequency, the unit is 10 12 s -1 , E ad-T represents the adsorption energy at different ambient temperatures; S53: normalizing the adsorption energy at different ambient temperatures to obtain a risk index of lithium-ion batteries at different temperatures, so as to achieve fault warning of lithium-ion batteries: Risk Index=(E ad-T -E ad-min ) / (E ad-max -E ad-min ) Among them, E ad-min represents the minimum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures, E ad-max Represents the maximum adsorption energy of the optimal adsorbed gas on the MgTe surface at different temperatures.

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