A method for preparing a lithium-ion high energy density battery cell

Abstract

The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for preparing a lithium-ion high-energy-density battery cell, comprising: obtaining a battery cell after charge and discharge activation, detecting the initial state parameters of the battery cell; determining the control temperature and aging time of the battery cell aging process based on the initial state parameters; in the aging process, collecting the aging stage state parameters of the battery cell and the temperature of each position of the battery cell at several time points; determining an aging characterization curve based on each of the aging stage state parameters and the temperature of each position of the battery cell, and determining the start time of the initial aging stage; adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve; after aging is completed, obtaining the aging state parameters of the battery cell, and adjusting the formation control parameters of charge and discharge activation in the formation stage based on the aging state parameters and the initial state parameters. The present invention can improve the consistency of the battery cell interface.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for preparing a lithium ion high energy density battery cell. Background Art

[0002] Lithium-ion batteries are rechargeable secondary batteries that are not only small and light, but also can store more electrical energy than other types of batteries. Lithium-ion batteries use lithium-containing metal compounds in the positive electrode and carbon (graphite) that can absorb and store lithium in the negative electrode. With this structure, it is possible to generate electricity without the need for electrolytes to melt the electrodes as in conventional batteries, thereby slowing down the aging of the battery itself, and not only can more electricity be stored, but the number of charge and discharge cycles can also be increased. In addition, lithium is a very small and light substance, which can make the battery have various advantages such as being small and light.

[0003] Due to the urgent demand of users for long battery life, improving battery life has become very important. Improving battery life requires increasing the energy density of the battery. However, the higher the battery energy density, the more unstable the battery performance may be, and higher requirements are also placed on battery safety technology. High energy density is an important development direction for energy storage devices in the future. Lithium-ion batteries have been widely used as energy storage devices with excellent performance in the past few decades. However, the energy density of traditional lithium-ion battery positive electrode materials has approached the theoretical value, and how to further improve the energy density has become a research hotspot. In the existing technology, the energy density of the battery system is improved. For lithium metal negative electrodes, the theoretical specific capacity of lithium is very high, which can reach 3000mAh / g, but lithium dendrites are easily formed during use to pierce the battery diaphragm and form a battery short circuit. The high-voltage and high-specific-capacity materials of the positive electrode are unstable, and the high-voltage electrode material structure is easily destroyed, which also causes the decomposition of the electrolyte. The construction of artificial SEI membranes, the construction of three-dimensional metal negative electrodes, and the regulation of the interface between lithium metal electrodes and electrolytes can improve the cycle life of the battery. The ultimate goal is to add additives to regulate the growth process of the material so that it does not grow into dendrites, but research and development in this area is very difficult.

[0004] The production process of lithium-ion batteries generally includes the following steps: positive and negative electrode ingredients, positive and negative electrode coating, positive and negative electrode film making, battery cell assembly, laser welding, liquid injection, formation, aging, detection and capacity division, packaging and shipment. The purpose of the battery formation stage is to fully activate the active substances and electrolytes in the battery to achieve stable electrochemical performance, and to activate the materials by charging and discharging the positive and negative electrode materials for the first few times, so that the materials are in the best state of use. The main purposes of aging are: to make the electrolyte infiltration better, which is conducive to the stability of battery performance; after aging, the active substances in the positive and negative electrode materials can accelerate some side effects, such as gas production, electrolyte decomposition, etc., so that the electrochemical performance of lithium batteries can quickly reach stability; after aging for a period of time, lithium batteries are screened for consistency. After formation, the voltage of the battery cell is unstable, and its measured value will deviate from the actual value. After aging, the voltage and internal resistance of the battery cell are more stable, which is convenient for screening batteries with high consistency.

[0005] In order to improve the energy density of the battery, the prior art usually improves the positive and negative electrode materials without considering the impact of battery formation and aging on battery performance. If the battery cell formation process is not handled properly, the battery cell interface consistency will be poor. Summary of the invention

[0006] To this end, the present invention provides a method for preparing a lithium ion high energy density battery cell, which is used to overcome the problem of poor battery cell interface consistency caused by failure to consider the influence of the formation stage on the battery cell performance in the prior art.

[0007] To achieve the above object, the present invention provides a method for preparing a lithium ion high energy density battery cell, comprising:

[0008] Obtaining the battery cell after charge and discharge activation, and detecting the initial state parameters of the battery cell; the state parameters at least include the battery cell voltage, internal resistance value, and SEI film resistance value;

[0009] Determine the control temperature and aging time of the battery cell aging process based on the initial state parameters;

[0010] During the aging process, the aging stage state parameters of the battery cell and the temperature of each position of the battery cell are collected at several time points;

[0011] Determining an aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell, and determining the start time of the initial aging stage;

[0012] Adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve;

[0013] After the aging is completed, the aging state parameters of the battery cell are obtained, and the formation control parameters of the charge-discharge activation in the formation stage are adjusted based on the aging state parameters and the initial state parameters;

[0014] Wherein, the formation control parameters include formation temperature, charging time and discharging time.

[0015] Further, the determining the control temperature and aging time of the battery cell aging process based on the initial state parameters includes:

[0016] Determining an initial eigenvector based on the initial state parameters;

[0017] The initial feature vector is compared with a preset feature vector, and the control temperature and aging time of the battery cell aging process are determined based on the comparison result.

[0018] Furthermore, the determining of the aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell includes:

[0019] Determine an aging characterization coefficient based on the state parameters of each aging stage corresponding to each time point;

[0020] Determine a first temperature characterization coefficient based on the temperature of each position of the battery cell corresponding to each time point;

[0021] An aging characterization curve is determined according to the aging characterization coefficient and the first temperature characterization coefficient.

[0022] Furthermore, the determining of the aging characterization coefficient based on the state parameters of each aging stage includes:

[0023] Based on the state parameters of the aging stages corresponding to each time point, a state parameter model of the state parameters of each aging stage in the aging process is constructed;

[0024] The aging characterization coefficient is determined based on each state parameter model.

[0025] Further, adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve includes:

[0026] Determine a first comparison value according to a comparison result of the time length from the first mutation region of the aging characterization curve to the start time of the initial aging stage and a preset time length;

[0027] The control temperature and / or aging time of the aging process are adjusted according to the first comparison value and the duration of the first mutation zone of the aging characterization curve.

[0028] Further, determining the first comparison value includes:

[0029] Determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve;

[0030] The first comparison value is determined according to a comparison result of the duration from the mutation time period to the start time of the initial aging stage and a preset duration.

[0031] Furthermore, the determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve includes:

[0032] If the slope of the aging characterization curve is greater than a preset slope threshold, and the duration corresponding to the slope of the aging characterization curve being greater than the preset slope threshold is greater than a preset duration threshold, the corresponding time period is determined as the mutation time period where the first mutation region is located.

[0033] Further, the formation control parameters of charge-discharge activation in the formation stage are adjusted based on the aging state parameters and the initial state parameters, including:

[0034] Determine a second comparison value based on the aging state parameter and the initial state parameter;

[0035] The formation control parameters of the charge-discharge activation in the formation stage are adjusted based on the second comparison value.

[0036] Further, the adjusting the formation control parameters of the charge-discharge activation in the formation stage based on the second comparison value includes:

[0037] Determining a formation control parameter adjustment coefficient based on a comparison result of the second comparison value and a preset comparison threshold;

[0038] The formation control parameter adjustment amount is determined based on the control parameter adjustment coefficient and the preset formation control parameter.

[0039] Furthermore, the step of acquiring the battery cell activated by charge and discharge and detecting the initial state parameters of the battery cell further includes: forming the battery cell based on preset formation control parameters.

[0040] Compared with the prior art, the beneficial effect of the present invention is that the present invention determines the control temperature and aging time of the aging process through the initial state parameters of the battery cell after charge and discharge activation, which can improve the efficiency of battery cell preparation. The aging characterization curve can be determined according to the aging stage state parameters of the battery cell at each time point in the aging process and the temperature of each position of the battery cell, thereby adjusting the control temperature and / or aging time of the aging process, which can ensure the aging quality of the battery cell and improve the consistency of the battery cell interface. By adjusting the formation control parameters of charge and discharge activation in the formation stage through the aging state parameters and the initial state parameters, the consistency of the battery cell interface can be improved and the yield rate of the battery cell can be improved.

[0041] Furthermore, the present invention can ensure the aging quality by determining the control temperature and aging time of the battery cell aging process based on the comparison result between the initial feature vector and the preset feature vector.

[0042] Furthermore, the present invention determines the aging characterization curve by jointly determining the state parameters of each aging stage corresponding to each time point and the temperature of each position of the battery cell, thereby ensuring that the aging characteristic curve can accurately reflect the characteristics of the battery cell aging process.

[0043] Furthermore, the present invention constructs a state parameter model of each aging stage state parameter in the aging process based on the aging stage state parameters corresponding to each time point, which can accurately characterize the changes of each state parameter in the aging process, thereby determining the aging characterization coefficient, and can improve the accuracy of the determined aging characterization curve.

[0044] Furthermore, the present invention determines a first comparison value based on a comparison result of the duration of the first mutation zone of the aging characterization curve from the start time of the initial aging stage to a preset duration, which can avoid interference from other factors and improve the accuracy of determining the first comparison value, thereby improving the accuracy of subsequent adjustment of the control temperature and / or aging time of the aging process to improve the consistency of the battery cell interface.

[0045] Furthermore, the present invention can improve the stability of the formation stage by adjusting the formation control parameters according to the second comparison value determined by the aging state parameter and the initial state parameter, thereby improving the consistency of the prepared battery cell interface and improving the battery cell yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a flow chart of a method for preparing a lithium-ion high energy density battery cell;

[0047] Figure 2 Schematic diagram of the process of step S2 of the embodiment of the present invention;

[0048] Figure 3 Schematic diagram of the process of step S4 of the embodiment of the present invention;

[0049] Figure 4 Schematic diagram of the process of step S41 of the embodiment of the present invention;

[0050] Figure 5 Schematic diagram of the process of step S5 of the embodiment of the present invention;

[0051] Figure 6 A schematic diagram of a process for determining a first comparison value according to an embodiment of the present invention;

[0052] Figure 7 Schematic diagram of the process of step S6 of the embodiment of the present invention;

[0053] Figure 8 Schematic diagram of the process of step S62 in the embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0056] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0057] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In practice, the lithium-ion battery production process generally includes: positive and negative electrode ingredients, positive and negative electrode coating, positive and negative electrode film making, battery cell assembly, laser welding, liquid injection, formation, aging, testing and capacity separation, packaging and shipment.

[0059] See also Figure 1 As shown, it is a flow chart of a method for preparing a lithium ion high energy density battery cell of the present invention. The present invention provides a method for preparing a lithium ion high energy density battery cell, comprising:

[0060] Step S1, obtaining a battery cell after charge and discharge activation, and detecting the initial state parameters of the battery cell; the state parameters at least include the battery cell voltage, internal resistance value, and SEI film resistance value;

[0061] Specifically, the step of acquiring the battery cell activated after charge and discharge and detecting the initial state parameters of the battery cell further includes: forming the battery cell based on preset formation control parameters.

[0062] In practice, the internal positive and negative electrode materials are activated through a certain charging and discharging method during the formation stage to improve the charging and discharging performance, self-discharge, storage and other comprehensive performance of the battery cell. The formation process of the battery cell is a conventional technical means in this field and will not be repeated here.

[0063] Specifically, the preset formation control parameters are determined based on the control parameters corresponding to the formation stage of the battery cells that have passed the qualification test. Generally, the average value of the formation stage control parameters corresponding to multiple groups of battery cells is taken to ensure the overall stability of the battery cell performance.

[0064] In practice, the cell voltage refers to the internal resistance of the positive and negative electrodes of the cell, which is an important parameter for measuring the charge transfer and ion migration capabilities of the cell, and directly affects the overall performance of the cell. During the first charge and discharge process of a lithium-ion battery, the electrode material and the electrolyte react at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. This passivation layer is an interface layer with the characteristics of a solid electrolyte. It is an electronic insulator but an excellent conductor of Li+. Li+ can be freely embedded in and out of the passivation layer. This passivation film is called a "solid electrolyte interface" (solid electrolyte interface), or SEI film for short. The resistance of the SEI film refers to the resistance of this passivation film.

[0065] Step S2, determining the control temperature and aging time of the battery cell aging process based on the initial state parameters;

[0066] Step S3, during the aging process, collecting the aging stage state parameters of the battery cell and the temperature of each position of the battery cell at several time points;

[0067] Step S4, determining an aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell, and determining the start time of the initial aging stage;

[0068] Step S5, adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve;

[0069] Step S6, after the aging is completed, obtaining the aging state parameters of the battery cell, and adjusting the formation control parameters of the charge-discharge activation in the formation stage based on the aging state parameters and the initial state parameters;

[0070] Wherein, the formation control parameters include formation temperature, charging time and discharging time.

[0071] The present invention determines the control temperature and aging time of the aging process through the initial state parameters of the battery cell after charge and discharge activation, which can improve the efficiency of battery cell preparation. According to the aging stage state parameters of the battery cell at each time point in the aging process and the temperature of each position of the battery cell, an aging characterization curve can be determined, thereby adjusting the control temperature and / or aging time of the aging process, which can ensure the aging quality of the battery cell and improve the consistency of the battery cell interface. By adjusting the formation control parameters of charge and discharge activation in the formation stage through the aging state parameters and the initial state parameters, the consistency of the battery cell interface can be improved, and the yield rate of the battery cell can be improved.

[0072] See also Figure 2 As shown, it is a flow chart of step S2 of an embodiment of the present invention; specifically, in step S2, the control temperature and aging time of the battery cell aging process are determined based on the initial state parameters, including:

[0073] Step S21, determining an initial feature vector based on the initial state parameters; each initial state parameter has a corresponding initial feature;

[0074] Step S22, comparing the initial feature vector with a preset feature vector, and determining a control temperature and an aging time of the battery cell aging process based on the comparison result.

[0075] In implementation, actual implementers may determine the preset feature vector based on the initial state parameters of multiple cells that have passed qualification tests according to actual conditions.

[0076] Specifically, according to the initial eigenvectors Y1, Y2, ..., Y j , …, Y m With the preset feature vectors E1, E2, ..., E j , …, E m Determine a first matching degree P1;

[0077] Where j = 1, 2, ..., m; P1 = (∑ m j=1 Y j ×E j ) / (sqrt(∑ m j=1 (Y j ) 2 )×sqrt(∑ m j=1 (E j ) 2 )); sqrt() is the preset square root determination function; m is the number of initial state parameters; Y j is the jth initial feature in the initial feature vector; E j is the jth preset feature in the preset feature vector;

[0078] If P1 is greater than or equal to the first preset threshold, the control temperature and aging time of the battery cell aging process are adjusted to the preset control temperature YT and the preset aging time Yt corresponding to the preset characteristic vector; if P1 is less than the first preset threshold, the control temperature of the battery cell aging process is adjusted to KT, and the aging time of the battery cell aging process is adjusted to Kt; wherein, KT=YT / P1, Kt=Yt / P1; the actual implementer can set the first preset threshold according to the actual situation. Preferably, the value range of the first preset threshold can be set to 0.8~0.95.

[0079] The present invention determines the control temperature and aging time of the battery cell aging process by comparing the initial characteristic vector with the preset characteristic vector, thereby ensuring the aging quality.

[0080] Specifically, in step S3, during the aging process, the aging stage state parameters of the battery cell and the temperature of each position of the battery cell are collected at several time points; the several time points can be set according to the aging time to obtain each data value in the aging characterization curve. Usually, fixed time intervals are used for periodic acquisition, and the number of time points is at least 15.

[0081] See also Figure 3 As shown, it is a flow chart of step S4 of an embodiment of the present invention; specifically, in step S4, determining the aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell includes:

[0082] Step S41, determining an aging characterization coefficient based on the state parameters of each aging stage corresponding to each time point;

[0083] See also Figure 4 As shown, it is a flow chart of step S41 of an embodiment of the present invention; specifically, in step S41, determining the aging characterization coefficient based on the state parameters of each aging stage includes:

[0084] Step S411, constructing a state parameter model of each aging stage state parameter during the aging process based on the aging stage state parameters corresponding to each time point;

[0085] In implementation, the state parameter model takes each state parameter as output and time as input, and constructs a state parameter model of the state parameters of each aging stage during the aging process based on the changes in the state parameters of the aging stage corresponding to each time point. The changes in the state parameters of each aging stage during the aging process can be simulated based on each state parameter model.

[0086] Step S412: determining an aging characterization coefficient based on each state parameter model.

[0087] In implementation, the optimal solution of each state parameter model can be determined based on the least squares method and determined as the aging characterization coefficient, or a neural network model can be trained based on each state parameter model corresponding to the battery cells that have passed the qualification test in historical data to determine the aging characterization coefficient.

[0088] The present invention constructs a state parameter model of each aging stage state parameter in the aging process based on the aging stage state parameters corresponding to each time point, which can accurately characterize the changes of each state parameter in the aging process, thereby determining the aging characterization coefficient, and can improve the accuracy of the determined aging characterization curve.

[0089] Step S42, determining a first temperature characterization coefficient based on the temperature of each position of the battery cell corresponding to each time point;

[0090] In implementation, a three-dimensional curve of temperature characteristic change at each position of the battery cell is constructed based on the temperature change over time at each position of the battery cell and the temperature change at each position of the battery cell. The first temperature characterization coefficient YB is determined according to the projection area of ​​the three-dimensional curve of temperature characteristic change on each coordinate plane, where YB=1 / (Tx+Ty+Tz); wherein Tx is the projection area of ​​the three-dimensional curve of temperature characteristic change on the yOz coordinate plane, Ty is the projection area of ​​the three-dimensional curve of temperature characteristic change on the xOz coordinate plane, and Tz is the projection area of ​​the three-dimensional curve of temperature characteristic change on the xOy coordinate plane.

[0091] Step S43: determining an aging characterization curve according to the aging characterization coefficient and the first temperature characterization coefficient.

[0092] In implementation, a general equation of an aging characterization curve is constructed based on state parameters of cells that have passed qualification tests in historical data, and the aging characterization curve is determined by substituting the determined aging characterization coefficient and the first temperature characterization coefficient into the coefficients corresponding to the general equation of the aging characterization curve.

[0093] The present invention determines the aging characterization curve by jointly determining the state parameters of each aging stage corresponding to each time point and the temperature of each position of the battery cell, thereby ensuring that the aging characteristic curve can accurately reflect the characteristics of the battery cell aging process.

[0094] See also Figure 5 As shown, it is a schematic diagram of the process of step S5 of an embodiment of the present invention; specifically, in step S5, adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve includes:

[0095] Step S51, determining a first comparison value according to a comparison result of a time length from the first mutation region of the aging characterization curve to the start time of the initial aging stage and a preset time length;

[0096] See also Figure 6 As shown, it is a schematic diagram of a process of determining a first comparison value according to an embodiment of the present invention; specifically, in the step S51, determining the first comparison value includes:

[0097] Step S511, determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve;

[0098] Specifically, determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve includes:

[0099] If the slope of the aging characterization curve is greater than a preset slope threshold and the duration corresponding to the slope of the aging characterization curve being greater than the preset slope threshold is greater than a preset duration, the corresponding time period is determined as the mutation time period where the first mutation region is located.

[0100] During implementation, the actual implementer can set the preset slope threshold based on actual conditions or based on the average of the mutation slopes corresponding to the battery cells that have passed the qualification test in historical data. The actual implementer can determine the preset duration based on the average of the duration of the first mutation zone in the aging process of the battery cells that have passed the qualification test in historical data according to actual conditions.

[0101] Step S512: determining the first comparison value according to a comparison result of the duration from the mutation time period to the start time of the initial aging stage and a preset duration.

[0102] In implementation, the first comparison value S1 is determined according to the comparison result of the time length KH from the start time of the mutation time period corresponding to the first mutation zone of the aging characterization curve to the start time of the initial aging stage and the preset time length YH;

[0103] Among them, S1=(KH+YH) / (KH×YH).

[0104] Step S52: adjusting the control temperature and / or aging time of the aging process according to the first comparison value and the duration of the first mutation zone of the aging characterization curve.

[0105] In implementation, if S1 < W2 and CH > W3, the control temperature and / or aging time of the aging process is not adjusted;

[0106] If S1<W2 and CH≤W3, the control temperature of the aging process is adjusted to QT, QT=YT / S1;

[0107] If S1≥W2 and CH>W3, the aging time of the aging process is adjusted to Qt, Qt=Yt / S1;

[0108] If S1≥W2 and CH≤W3, the control temperature of the aging process is adjusted to QT, and the aging time is adjusted to Qt;

[0109] Among them, W2 is the first comparison threshold, W3 is the duration threshold, CH is the duration of the first mutation zone of the aging characterization curve, and the actual implementer can set the first comparison threshold based on the average of the first comparison values ​​determined during the aging process of the battery cells that have passed the qualification test in the historical data according to the actual situation. The actual implementer can set the duration threshold based on the average or maximum value of the duration of the first mutation zone of the aging characterization curve corresponding to the battery cells that have passed the qualification test in the historical data according to the actual situation.

[0110] The present invention determines a first comparison value based on a comparison result of the time length from the first mutation zone of the aging characterization curve to the start time of the initial aging stage and a preset time length, which can avoid interference from other factors and improve the accuracy of determining the first comparison value, thereby improving the accuracy of subsequent adjustment of the control temperature and / or aging time of the aging process to improve the consistency of the battery cell interface.

[0111] See also Figure 7 As shown, it is a flow chart of step S6 of an embodiment of the present invention; specifically, in step S6, adjusting the formation control parameters of charge-discharge activation in the formation stage based on the aging state parameter and the initial state parameter includes:

[0112] Step S61, determining a second comparison value based on the aging state parameter and the initial state parameter;

[0113] Specifically, according to the aging state parameters A1, A2, ..., A i , …, A m With the initial state parameters B1, B2, ..., B i , …, B m Determine the second comparison value P2; wherein P2=sqrt(∑ m i=1 (A i -B i ) 2 ), i=1, 2, …, m, A i is the i-th aging state parameter, B i is the i-th initial state parameter.

[0114] Step S62: adjusting formation control parameters of charge-discharge activation in the formation stage based on the second comparison value.

[0115] See also Figure 8 As shown, it is a flow chart of step S62 of an embodiment of the present invention. Specifically, in step S62, adjusting the formation control parameters of charge-discharge activation in the formation stage based on the second comparison value includes:

[0116] Step S621, determining a formation control parameter adjustment coefficient based on a comparison result between the second comparison value and a preset comparison threshold;

[0117] In implementation, the formation control parameter adjustment coefficient L=P2 / P0, where P0 is a preset comparison threshold value, which can be determined by actual implementers based on the average value of the second comparison values ​​corresponding to the battery cells that have passed the qualification inspection in historical data according to actual conditions.

[0118] Step S622, determining a formation control parameter adjustment amount based on the control parameter adjustment coefficient and a preset formation control parameter.

[0119] In implementation, the formation control parameter adjustment amount X corresponding to the kth formation control parameter is a k ×L×Z k ; Among them, a k is the weight coefficient corresponding to the kth formation control parameter; Z k is the preset formation control parameter corresponding to the kth formation control parameter; the actual implementer can set the weight coefficient corresponding to the kth formation control parameter according to the actual situation, or determine it based on the statistical analysis of the formation control parameters of the battery cells that have passed the qualification inspection.

[0120] The present invention can improve the stability of the formation stage by adjusting the formation control parameter according to the second comparison value determined by the aging state parameter and the initial state parameter, thereby improving the consistency of the prepared battery cell interface and improving the battery cell yield.

[0121] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-ion high energy density battery cell, characterized in that: include: Obtaining the battery cell after charge and discharge activation, and detecting the initial state parameters of the battery cell; the state parameters at least include the battery cell voltage, internal resistance value and SEI film resistance value; Determine the control temperature and aging time of the battery cell aging process based on the initial state parameters; During the aging process, the aging stage state parameters of the battery cell and the temperature of each position of the battery cell are collected at several time points; Determining an aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell, and determining the start time of the initial aging stage; Adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve; After aging is completed, the aging state parameters of the battery cell are obtained, and the formation control parameters of the charge and discharge activation in the formation stage are adjusted based on the aging state parameters and the initial state parameters, wherein the formation control parameters include formation temperature, charging time and discharging time; The step of determining the control temperature and aging time of the battery cell aging process based on the initial state parameters includes: Determining an initial eigenvector based on the initial state parameters; Comparing the initial feature vector with a preset feature vector, and determining a control temperature and an aging time of the battery cell aging process based on the comparison result; According to the initial eigenvectors Y1, Y2, ..., Y j , …, Y m With the preset feature vectors E1, E2, ..., E j , …, E m Determine a first matching degree P1; Where j = 1, 2, ..., m; P1 = (∑ m j=1 Y j ×E j ) / (sqrt(∑ m j=1 (Y j ) 2 )×sqrt(∑ m j=1 (E j ) 2 )); sqrt() is the preset square root determination function; m is the number of initial state parameters; Y j is the jth initial feature in the initial feature vector; E j is the jth preset feature in the preset feature vector; If P1 is greater than or equal to the first preset threshold, the control temperature and aging time of the battery cell aging process are adjusted to the preset control temperature YT and the preset aging time Yt corresponding to the preset feature vector; If P1 is less than the first preset threshold, the control temperature of the battery cell aging process is adjusted to KT, and the aging time of the battery cell aging process is adjusted to Kt; wherein KT=YT / P1, Kt=Yt / P1.

2. The method for preparing a lithium-ion high energy density battery cell according to claim 1, characterized in that: Determining an aging characterization curve based on the state parameters of each aging stage and the temperature of each position of the battery cell includes: Determine an aging characterization coefficient based on the state parameters of each aging stage corresponding to each time point; Determine a first temperature characterization coefficient based on the temperature of each position of the battery cell corresponding to each time point; An aging characterization curve is determined according to the aging characterization coefficient and the first temperature characterization coefficient.

3. The method for preparing a lithium-ion high energy density battery cell according to claim 2, characterized in that: Determining an aging characterization coefficient based on each of the aging stage state parameters includes: Based on the state parameters of the aging stages corresponding to each time point, a state parameter model of the state parameters of each aging stage in the aging process is constructed; The aging characterization coefficient is determined based on each state parameter model.

4. The method for preparing a lithium-ion high energy density battery cell according to claim 3, characterized in that: Adjusting the control temperature and / or aging time of the aging process based on the aging characterization curve comprises: Determine a first comparison value according to a comparison result of the time length from the first mutation region of the aging characterization curve to the start time of the initial aging stage and a preset time length; The control temperature and / or aging time of the aging process are adjusted according to the first comparison value and the duration of the first mutation zone of the aging characterization curve.

5. The method for preparing a lithium-ion high energy density battery cell according to claim 4, characterized in that: Determining the first comparison value includes: Determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve; The first comparison value is determined according to a comparison result of the duration from the mutation time period to the start time of the initial aging stage and a preset duration.

6. The method for preparing a lithium-ion high energy density battery cell according to claim 5, characterized in that: Determining the mutation time period where the first mutation region is located based on the slope change of the aging characterization curve includes: If the slope of the aging characterization curve is greater than a preset slope threshold, and the duration corresponding to the slope of the aging characterization curve being greater than the preset slope threshold is greater than a preset duration threshold, the corresponding time period is determined as the mutation time period where the first mutation region is located.

7. The method for preparing a lithium-ion high energy density battery cell according to claim 1, characterized in that: Adjusting the formation control parameters of charge-discharge activation in the formation stage based on the aging state parameters and the initial state parameters includes: Determine a second comparison value based on the aging state parameter and the initial state parameter; The formation control parameters of the charge-discharge activation in the formation stage are adjusted based on the second comparison value.

8. The method for preparing a lithium-ion high energy density battery cell according to claim 7, characterized in that: Adjusting the formation control parameters of charge-discharge activation in the formation stage based on the second comparison value includes: Determining a formation control parameter adjustment coefficient based on a comparison result of the second comparison value and a preset comparison threshold; The formation control parameter adjustment amount is determined based on the control parameter adjustment coefficient and the preset formation control parameter.

9. The method for preparing a lithium-ion high energy density battery cell according to claim 8, characterized in that: The method further comprises: forming the battery cell based on preset formation control parameters before obtaining the battery cell activated by charge and discharge and detecting the initial state parameters of the battery cell.

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