Lithium ion battery cell and method for detecting dissolved amount of transition metal

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery cell and a method for detecting the dissolved amount of transition metal. The lithium ion battery cell comprises a roll core formed by winding a positive plate, a diaphragm and a negative plate, electrolyte and a metal shell used for placing the roll core, the positive plate comprises a positive current collector and a positive active material substance layer coated on at least one surface of the positive current collector, and the negative plate comprises a negative current collector and a positive active material substance layer coated on at least one surface of the positive current collector. The positive electrode active material substance layer comprises one or more of lithium iron phosphate, lithium iron manganese phosphate, nickel cobalt lithium manganate, nickel cobalt lithium aluminate, nickel cobalt manganese lithium aluminate, spinel lithium manganate, spinel nickel lithium manganate and layered lithium manganate, and the dissolved amount of transition metal Mn in the battery cell is less than or equal to 0.02 g / Ah.

Description

Technical Field

[0001] This application relates to the technical field of lithium-ion batteries, and particularly relates to a lithium-ion battery cell and a method for detecting the dissolution amount of transition metals. Background Art

[0002] Currently, lithium-ion batteries have been widely used in many fields such as portable electronic devices, electric vehicles, and energy storage devices due to their advantages of high energy density, high working voltage, long cycle life, and environmental friendliness. Among them, the cathode material, as the core component of a lithium-ion battery, directly affects the overall performance and life of the battery. From early lithium manganate (LiMn2O4) and lithium iron phosphate (LiFePO4), to the current widely used nickel-cobalt-manganese ternary cathode material (LiNi x Co y Mn z O2), to the low-cobalt or cobalt-free manganese-rich cathode material with great potential in the future, these cathode materials containing transition metals will inevitably experience the phenomenon of transition metal dissolution in an electrochemical environment.

[0003] The dissolution of transition metals often destroys the structural stability of the cathode material, resulting in battery capacity attenuation and shortened cycle life. It also causes the dissolved metal ions to migrate and deposit on the surface of the anode material, catalyzing the decomposition and regeneration of the solid electrolyte interface film (SEI film), resulting in continuous loss of reversible active lithium and electrolyte, further deteriorating the cycle performance and power performance of the battery.

[0004] In this regard, in related technologies, the research on the dissolution of transition metal ions in batteries with cathode materials containing transition metals mainly relies on detection methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma atomic absorption spectrometry (ICP-AAS).

[0005] In the process of implementing the embodiments of the present disclosure, it is found that there are at least the following problems in related technologies:

[0006] The detection methods for transition metals in related technologies usually require the use of large-scale testing equipment for detection, and the battery needs to be disassembled or a specific structure needs to be extracted, resulting in the technical problems of complex detection process and expensive testing equipment. In addition, the detection methods for transition metals in related technologies can often only detect the content in the electrolyte of the battery or the content deposited on the anode, and cannot quantitatively calculate the dissolution amount of transition metals in the entire battery, thus unable to provide accurate detection data, restricting the dynamic monitoring and in-depth research on the transition metal dissolution process.

[0007] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present application, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0008] To provide a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary is not a comprehensive review, nor is it intended to identify key / important elements or delineate the scope of protection of these embodiments. Instead, it serves as a prelude to the subsequent detailed description.

[0009] Embodiments of the present disclosure provide a method for detecting a lithium-ion cell and the amount of transition metal dissolution, so as to simplify the detection process of the amount of transition metal dissolution, reduce the cost of detection equipment, improve detection efficiency and accuracy, so as to more deeply understand the dissolution mechanism of transition metals in lithium-ion batteries and lay a foundation for improving the performance and stability of the batteries.

[0010] In some embodiments, the lithium-ion cell includes a wound core formed by winding a positive electrode sheet, a separator, and a negative electrode sheet, an electrolyte, and a metal casing for placing the wound core. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface thereof. The positive electrode active material layer includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese aluminate, spinel lithium manganate, spinel lithium nickel manganate, and layered lithium manganate. Among them, the dissolution amount of transition metal Mn in the cell is ≤ 0.02 g / Ah.

[0011] Optionally, the dissolution amount of transition metal Mn is obtained by the following detection method, including:

[0012] According to the following formula, calculate the transition metal capture rate η of the test cell:

[0013]

[0014] where I1 is the response current corresponding to the test cell during the deposition current test, I2 is the response current corresponding to the test cell during the dissolution current test, and t is the scanning time of the cyclic voltammetry test during the dissolution current test of the test cell;

[0015] Assemble the test cell to be tested, where a detection sensor is provided between the positive electrode and the negative electrode of the test cell to be tested;

[0016] According to the following formula, calculate the dissolution amount of the transition metal of the test cell to be tested:

[0017]

[0018] Among them, I3 is the response current corresponding to the battery cell to be tested in the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge number after oxidation of the target element to be measured, M is the relative atomic mass of the target element to be measured, and m sensor is the mass of the captured transition metal, and m total is the dissolution amount of the transition metal of the battery cell to be tested, and t is the scanning time corresponding to the battery cell to be tested in the transition metal deposition current test.

[0019] Optionally, before calculating the transition metal capture rate η of the test battery cell, it further includes:

[0020] Assembling the test battery cell, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the test battery cell;

[0021] Wiring the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method;

[0022] Through the electrochemical workstation, simultaneously performing a dissolution current test and a deposition current test on the test battery cell, and respectively obtaining the corresponding response current I1 during the deposition current test and the corresponding response current I2 during the dissolution current test.

[0023] Optionally, wiring the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method includes:

[0024] Connecting the positive electrode of the test battery cell to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation;

[0025] Connecting the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation;

[0026] Connecting the negative electrode of the test battery cell to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation;

[0027] Connecting the negative electrode of the test battery cell to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

[0028] Optionally, simultaneously performing a dissolution current test and a deposition current test on the test battery cell includes:

[0029] Performing a cyclic voltammetry test on the working electrode WE2, with a scanning voltage speed of V step (mv / s), a scanning start voltage of the scanning start voltage of V star , a scanning upper limit voltage of V ub (mv), a scanning lower limit voltage of V lb (mv), and a scanning path from Vstar to V ub and then back to V lb then to V star ; record the corresponding response current I2 during the entire test process.

[0030] While conducting the dissolution current test, apply a specified excitation voltage V to the working electrode WE1 polar ; record the corresponding response current I1 during the entire test process.

[0031] Optionally, the scanning starting voltage V star is the open-circuit voltage of the cell to be tested, and the scanning speed V step ranges from 0.01 mV / s to 20 mV / s. The scanning upper limit voltage V ub is less than 5 V, and the scanning lower limit voltage V lb is greater than 1 V. The excitation voltage V polar is less than the electrode potential of the element to be tested with respect to lithium and greater than the reduction potential of the electrolyte.

[0032] Optionally, after assembling the cell to be tested, it further includes:

[0033] Wire the cell to be tested and a multi-channel electrochemical workstation according to a preset wiring method;

[0034] Through the electrochemical workstation, conduct a working condition test and a transition metal deposition current test on the cell to be tested simultaneously, and obtain the corresponding response current I3 in the transition metal deposition current test.

[0035] Optionally, wiring the cell to be tested and a multi-channel electrochemical workstation according to a preset wiring method includes:

[0036] Connect the positive electrode of the cell to be tested to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation;

[0037] Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation;

[0038] Connect the negative electrode of the cell to be tested to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation;

[0039] Connect the negative electrode of the cell to be tested to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

[0040] Optionally, conducting a working condition test and a transition metal deposition current test on the cell to be tested simultaneously includes:

[0041] Perform constant current, constant voltage, constant power charge and discharge or mixed working condition tests on the cell to be tested simultaneously;

[0042] While performing the working condition test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I3 during the entire test process.

[0043] Optionally, the excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

[0044] Optionally, the detection sensor is made of platinum (Pt) or gold (Au), has a mesh shape, the wire diameter of the mesh is 1 - 50 μm, and the diameter of the mesh holes is 1 - 50 μm.

[0045] Optionally, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer on the surface of the positive electrode current collector. Among them, the positive electrode current collector is a transition metal sheet or a metal mesh, and is composed of copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn) or aluminum (Al). Among them, the positive electrode active material layer includes lithium iron phosphate LiFePO4, lithium iron manganese phosphate LiFe x Mn 1-x PO4 (0.1 ≤ x ≤ 0.9), lithium nickel cobalt manganese oxide LiNi x Mn y Co z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt aluminate LiNi x Co y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt manganese aluminate LiNi x Co j Mn y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ j ≤ 0.3, 0.05 ≤ y ≤ 0.3, z = 1 - x - y - j), spinel lithium manganese oxide LiMn2O4, spinel lithium nickel manganese oxide LiNi x Mn 2-x O4 (0.1 ≤ x ≤ 0.9) and layered lithium manganese oxide Li 1+x MnO2 (-0.2 ≤ x ≤ 0.2), or one or more of them.

[0046] Optionally, the negative electrode sheet is a lithium (Li) sheet; or, it is a metal sheet or a metal mesh made of platinum (Pt), gold (Au) or silver (Ag).

[0047] In some embodiments, the method for detecting the dissolved amount of transition metal includes:

[0048] Calculate the transition metal capture rate η of the test battery cell according to the following formula:

[0049]

[0050] where I1 is the response current corresponding to the test battery cell during the deposition current test, I2 is the response current corresponding to the test battery cell during the dissolution current test, and t is the scanning time for cyclic voltammetry test during the dissolution current test of the test battery cell;

[0051] Assemble the battery cell to be tested, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the battery cell to be tested;

[0052] Calculate the dissolved amount of the transition metal of the battery cell to be tested according to the following formula:

[0053]

[0054] where I3 is the response current corresponding to the battery cell to be tested during the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge of the target element to be measured after oxidation, M is the relative atomic mass of the target element to be measured, m sensor is the mass of the captured transition metal, m total is the dissolved amount of the transition metal of the battery cell to be tested, and t is the scanning time corresponding to the battery cell to be tested during the transition metal deposition current test.

[0055] The lithium-ion battery cell and the method for detecting the dissolved amount of transition metal provided by the embodiments of the present disclosure can achieve the following technical effects:

[0056] Real-time monitoring: Without disassembling the battery or extracting a specific structure, in-situ and online monitoring of the transition metal dissolution process of the battery can be realized, and real-time data can be obtained.

[0057] High efficiency and accuracy: Simplify the pretreatment steps, reduce the detection time, and improve the detection efficiency and accuracy.

[0058] Low equipment dependence: Do not need to rely on large-scale detection equipment such as inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma atomic absorption spectrometry (ICP-AAS).

[0059] Guiding application: The dissolved amount of the transition metal of the entire battery can be quantitatively calculated, thereby providing key data support for evaluating the battery performance, optimizing the design of the positive and negative electrode materials, and improving the battery life.

[0060] Meanwhile, through the test method of this application, the dissolution mechanism of transition metals in lithium-ion batteries can be more profoundly understood, thus laying a foundation for improving the performance and stability of the batteries.

[0061] The above general description and the following description are only exemplary and explanatory, and are not used to limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] One or more embodiments are exemplarily illustrated by corresponding drawings. These exemplary illustrations and the drawings do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements. The drawings do not constitute a scale limitation, and wherein:

[0063] Figure 1 is a schematic structural diagram of a lithium-ion cell provided by an embodiment of the present disclosure;

[0064] Figure 2 is another schematic diagram of a lithium-ion cell provided by an embodiment of the present disclosure;

[0065] Figure 3 is a flowchart of a method for detecting the dissolution amount of transition metals provided by an embodiment of the present disclosure;

[0066] Figure 4 is an assembly schematic diagram of an inspection cell provided by an embodiment of the present disclosure;

[0067] Figure 5 is an assembly schematic diagram of a cell to be tested provided by an embodiment of the present disclosure;

[0068] Figure 6 is a schematic diagram of test wiring provided by an embodiment of the present disclosure;

[0069] Figure 7 is a cyclic voltammetry test result graph of the calibration process provided by an embodiment of the present disclosure;

[0070] Figure 8 is a graph of the current captured by a test sensor during the calibration process provided by an embodiment of the present disclosure;

[0071] Figure 9 is a graph of the voltage of a cylindrical battery and the current captured by a test sensor during the test process provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0072] In order to more comprehensively understand the features and technical content of the embodiments of the present disclosure, the implementation of the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The attached drawings are for reference and illustration only and are not used to limit the embodiments of the present disclosure. In the following technical descriptions, for the sake of explanation, numerous details are provided to provide a full understanding of the disclosed embodiments. However, one or more embodiments can still be implemented without these details. In other cases, well-known structures and devices may be shown in a simplified manner to simplify the drawings.

[0073] In the specification and claims of the embodiments of the present disclosure and the above-mentioned drawings, terms such as "first", "second", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to implement the embodiments of the present disclosure described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0074] In the embodiments of the present disclosure, the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "middle", "outer", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the embodiments of the present disclosure and their embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation or be constructed and operated in a specific orientation. And, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0075] In addition, the terms "arranged", "connected", "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0076] Unless otherwise specified, the term "plurality" means two or more.

[0077] In the embodiments of the present disclosure, the character " / " indicates that the objects before and after are in an "or" relationship. For example, A / B means: A or B.

[0078] The term "and / or" is a description of the associated relationship of an object and indicates that three relationships can exist. For example, A and / or B means: A or B, or, A and B these three relationships.

[0079] It should be noted that, without conflict, the embodiments in the present disclosure and the features in the embodiments may be combined with each other.

[0080] According to the packaging form, lithium-ion batteries can be divided into three forms: square, cylindrical and soft-pack. Among them, cylindrical lithium batteries have gradually become a research hotspot of lithium batteries due to their good consistency, high production efficiency, strong heat dissipation ability at the system level, etc. In this regard, as shown in Figure 1 and Figure 2 In order to solve the technical problems existing in the related art, the present application provides a lithium-ion cell, which includes a core 21 formed by winding a positive electrode sheet 5, a separator 4 and a negative electrode sheet 3, an electrolyte, and a metal case 2 for placing the core 21. The battery is packaged with a cylindrical steel case 2, and a cap 1 is located at the top of the battery. Specifically, the positive electrode sheet 5 includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface thereof. The positive electrode active material layer includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese aluminate, spinel manganese oxide, spinel nickel manganese oxide and layered manganese oxide. Among them, the dissolution amount of transition metal manganese (Mn) in the cell ≤ 0.02 g / Ah.

[0081] In the embodiments of the present application, the dissolution amount of the transition metal Mn in the present application is obtained through the following detection method, which includes the following steps:

[0082] Step 100: Calculate the transition metal capture rate η of the test cell according to the following formula:

[0083]

[0084] where I1 is the response current corresponding to the test cell during the deposition current test, I2 is the response current corresponding to the test cell during the dissolution current test, and t is the scanning time of the cyclic voltammetry test during the dissolution current test of the test cell.

[0085] Step 200: Assemble the cell to be tested, and a detection sensor is arranged between the positive electrode and the negative electrode of the cell to be tested.

[0086] Step 300: Calculate the dissolution amount of the transition metal of the cell to be tested according to the following formula:

[0087]

[0088] where I3 is the response current corresponding to the cell to be tested during the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge number after oxidation of the target element to be measured, M is the relative atomic mass of the target element to be measured, and m sensorThe mass of the captured transition metal, m total The dissolved amount of the transition metal in the battery cell to be tested, and t is the scanning time corresponding to the battery cell to be tested in the transition metal deposition current test.

[0089] Optionally, before calculating the transition metal capture rate η of the test battery cell, it further includes:

[0090] Assemble the test battery cell, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the test battery cell;

[0091] Connect the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method;

[0092] Through the electrochemical workstation, perform a dissolution current test and a deposition current test on the test battery cell simultaneously, and respectively obtain the corresponding response current I1 during the deposition current test and the corresponding response current I2 during the dissolution current test.

[0093] Optionally, connecting the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method includes:

[0094] Connect the positive electrode of the test battery cell to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation;

[0095] Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation;

[0096] Connect the negative electrode of the test battery cell to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation;

[0097] Connect the negative electrode of the test battery cell to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

[0098] Optionally, performing a dissolution current test and a deposition current test on the test battery cell simultaneously includes:

[0099] Perform a cyclic voltammetry test on the working electrode WE2, the scanning voltage speed is V step (mv / s), the scanning start voltage is the scanning start voltage is V star , the scanning upper limit voltage is V ub (mv), the scanning lower limit voltage is V lb (mv), the scanning path is from V star to V ub and then back to V lb and then to V star , record the corresponding response current I2 during the whole test process;

[0100] While performing the dissolution current test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I1 during the entire test process.

[0101] Optionally, the scanning start voltage V star is the open-circuit voltage of the cell to be tested, and the scanning speed V step ranges from 0.01 mV / s to 20 mV / s. The scanning upper limit voltage V ub is less than 5 V, and the scanning lower limit voltage V lb is greater than 1 V. The excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

[0102] Optionally, after assembling the cell to be tested, it further includes:

[0103] Connect the cell to be tested to a multi-channel electrochemical workstation according to a preset wiring method;

[0104] Through the electrochemical workstation, perform a working condition test and a transition metal deposition current test on the cell to be tested simultaneously, and obtain the corresponding response current I3 in the transition metal deposition current test.

[0105] Optionally, connecting the cell to be tested to a multi-channel electrochemical workstation according to a preset wiring method includes:

[0106] Connect the positive electrode of the cell to be tested to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation;

[0107] Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation;

[0108] Connect the negative electrode of the cell to be tested to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation;

[0109] Connect the negative electrode of the cell to be tested to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

[0110] Optionally, performing a working condition test and a transition metal deposition current test on the cell to be tested simultaneously includes:

[0111] Perform constant current, constant voltage, constant power charge and discharge or mixed working condition tests on the cell to be tested simultaneously;

[0112] While performing the working condition test, apply a specified excitation voltage V to the working electrode WE1polar , record the response current I3 corresponding to the entire test process.

[0113] Optionally, the excitation voltage V of the present application polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

[0114] Optionally, the detection sensor of the present application is made of platinum (Pt) or gold (Au), in a mesh shape, with a wire diameter of 1 - 50 μm and a mesh hole diameter of 1 - 50 μm.

[0115] Optionally, the positive electrode sheet of the present application includes a positive electrode current collector and a positive electrode active material layer on the surface of the positive electrode current collector, wherein the positive electrode current collector is a transition metal sheet or a metal mesh, composed of copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), or aluminum (Al), and wherein the positive electrode active material layer includes lithium iron phosphate LiFePO4, lithium iron manganese phosphate LiFe x Mn 1-x PO4 (0.1 ≤ x ≤ 0.9), lithium nickel cobalt manganese oxide LiNi x Mn y Co z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt aluminate LiNi x Co y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt manganese aluminate LiNi x Co j Mn y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ j ≤ 0.3, 0.05 ≤ y ≤ 0.3, z = 1 - x - y - j), spinel lithium manganese oxide LiMn2O4, spinel lithium nickel manganese oxide LiNi x Mn 2-x O4 (0.1 ≤ x ≤ 0.9) and layered lithium manganese oxide Li 1+x MnO2 (-0.2 ≤ x ≤ 0.2), one or more of them.

[0116] Optionally, the negative electrode sheet of the present application is a lithium (Li) sheet; or, it is a metal sheet or a metal mesh composed of platinum (Pt), gold (Au), or silver (Ag).

[0117] In an embodiment of the present application, as shown in combination with Figure 3 , the present application provides a method for detecting the dissolution amount of transition metals, including:

[0118] Step 301: Assemble and inspect the battery cell.

[0119] Specifically, in combination with Figure 4 As shown, the test battery cell is assembled in the order of the positive electrode a - separator b - detection sensor c - separator b - negative electrode d, so that a detection sensor c is arranged between the positive electrode a and the negative electrode d of the test battery cell.

[0120] Preferably, the detection sensor c of the present application can be composed of platinum (Pt), gold (Au) or silver (Ag), and its shape is net-shaped, the diameter of the net wire is 1 - 50 um, and the diameter of the mesh hole is 1 - 50 um.

[0121] Preferably, the positive electrode a of the test battery cell of the present application can be a transition metal sheet or a metal mesh, and the transition metal sheet or the metal mesh serves as both the positive electrode current collector and the reaction electrode. Among them, the positive electrode current collector can be composed of copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn) or aluminum (Al).

[0122] Preferably, the negative electrode d of the test battery cell of the present application can be a lithium (Li) sheet; or it can be a metal sheet or a metal mesh composed of platinum (Pt), gold (Au) or silver (Ag).

[0123] Step 302: Connect the test battery cell to a multi-channel electrochemical workstation.

[0124] Specifically, the test battery cell is connected to the multi-channel electrochemical workstation according to a preset wiring method. The specific preset wiring method is as shown in combination with Figure 6 including:

[0125] Connect the positive electrode a of the test battery cell to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation EW;

[0126] Connect the detection sensor c to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation EW;

[0127] Connect the negative electrode d of the test battery cell to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation EW;

[0128] Connect the negative electrode d of the test battery cell to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation EW.

[0129] Step 303: Perform a dissolution current test and a deposition current test on the test battery cell.

[0130] Specifically, in the dissolution current test, a cyclic voltammetry test is performed on the working electrode WE2, and the scanning voltage speed is V step(mv / s), the starting voltage of the scan is V star , the upper limit voltage of the scan is V ub (mv), the lower limit voltage of the scan is V lb (mv), the scan path is from V star to V ub and then back to V lb and then to V star , record the corresponding response current I2 during the entire test process. And, while performing the dissolution current test, apply a specified excitation voltage V polar to the working electrode WE1 and record the corresponding response current I1 during the entire test process.

[0131] Among them, the above-mentioned starting voltage V star of the scan is the open-circuit voltage of the cell to be tested, and the scan speed V step ranges from 0.01 mV / s to 20 mV / s. The upper limit voltage V ub of the scan is less than 5 V, and the lower limit voltage V lb of the scan is greater than 1 V. The excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

[0132] Step 304: Calculate the transition metal capture rate η of the test cell.

[0133] Specifically, according to the following formula, calculate the transition metal capture rate η of the test cell:

[0134]

[0135] Among them, I1 is the response current corresponding to the test cell during the deposition current test, I2 is the response current corresponding to the test cell during the dissolution current test, and t is the scan time of the cyclic voltammetry test during the dissolution current test of the test cell.

[0136] Step 305: Assemble the cell to be tested.

[0137] Specifically, as shown in Figure 5 , assemble the cell to be tested in the order of positive electrode a'-separator b-detection sensor c-separator b-negative electrode d to form the cell to be tested, so that a detection sensor c is provided between the positive electrode a and the negative electrode d of the cell to be tested.

[0138] Preferably, the detection sensor c of the present application can be composed of platinum (Pt), gold (Au) or silver (Ag), and its shape is net-shaped, the diameter of the net wire is 1-50 um, and the diameter of the mesh hole is 1-50 um.

[0139] Preferably, the positive electrode a' of the battery cell to be tested in the present application includes a positive current collector and a positive active material layer on the surface of the positive current collector. That is, the positive active material layer is formed by powder adhesion and forms a stable current path by collecting electrons through the positive current collector. Among them, the positive current collector can be a transition metal sheet or a metal mesh, which is composed of copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn) or aluminum (Al). The positive active material layer includes lithium iron phosphate LiFePO4, lithium iron manganese phosphate LiFe x Mn 1-x PO4 (0.1 ≤ x ≤ 0.9), lithium nickel cobalt manganese oxide LiNi x Mn y Co z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt aluminate LiNi x Co y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.3, z = 1 - x - y), lithium nickel cobalt manganese aluminate LiNi x Co j Mn y Al z O2 (0.7 ≤ x ≤ 0.95, 0.05 ≤ j ≤ 0.3, 0.05 ≤ y ≤ 0.3, z = 1 - x - y - j), spinel lithium manganese oxide LiMn2O4, spinel lithium nickel manganese oxide LiNi x Mn 2-x O4 (0.1 ≤ x ≤ 0.9) and layered lithium manganese oxide Li 1+x MnO2 (-0.2 ≤ x ≤ 0.2), or one or more of them.

[0140] Preferably, the negative electrode d of the battery cell to be tested in the present application can be a lithium (Li) sheet; or, it can be a metal sheet or a metal mesh composed of platinum (Pt), gold (Au) or silver (Ag).

[0141] Step 306: Connect the battery cell to be tested to a multi-channel electrochemical workstation.

[0142] Specifically, connect the battery cell to be tested to the multi-channel electrochemical workstation according to a preset wiring method. The specific preset wiring method is as shown in Figure 6 and includes:

[0143] Connect the positive electrode a' of the battery cell to be tested to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation EW;

[0144] Connect the detection sensor c to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation EW;

[0145] Connect the negative electrode d of the cell to be tested to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation EW;

[0146] Connect the negative electrode d of the cell to be tested to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation EW.

[0147] Step 307: Simultaneously perform a working condition test and a transition metal deposition current test on the cell to be tested.

[0148] Specifically, perform a constant current, constant voltage, constant power charge and discharge or a mixed working condition test on the cell to be tested. While performing the working condition test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I3 during the entire test process.

[0149] Preferably, the above excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

[0150] Step 308: Calculate the dissolution amount of the transition metal in the cell to be tested.

[0151] Specifically, calculate the dissolution amount of the transition metal in the cell to be tested according to the following formula:

[0152]

[0153] where I3 is the response current corresponding to the cell to be tested in the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge number of the element to be measured after oxidation, M is the relative atomic mass of the element to be measured, m sensor is the mass of the captured transition metal, m total is the dissolution amount of the transition metal in the cell to be tested, and t is the scanning time corresponding to the cell to be tested in the transition metal deposition current test.

[0154] In this way, the detection method for the dissolution amount of the transition metal in this application does not rely on large-scale professional equipment. By setting the detection sensor between the positive electrode and the negative electrode and cooperating with the multi-channel electrochemical workstation for wiring to test the battery characteristics, the dissolution amount of the transition metal of the entire battery can be quantitatively calculated based on the test data. The detection process is simple and efficient, and in-situ detection of the battery is achieved.

[0155] In a specific application of the present application, taking the dissolution amount of manganese (Mn) element during the complete charging process of a lithium-ion cylindrical battery as an example, the method for detecting the dissolution amount of transition metals in the present application includes:

[0156] Step 401: Inspect cell assembly: Assemble into a test cell cell in the order of positive electrode - separator - detection sensor - separator - negative electrode.

[0157] Among them, the detection sensor is a platinum wire mesh, the diameter of the platinum wire is 40um, and the mesh aperture is 300um. The positive electrode plate is a manganese metal plate. The separator is a PE separator with a thickness of 16um. The electrolyte used in the test cell cell is EC / EMC (30 / 70:v / v), 1.2mol / L lithium hexafluorophosphate LiPF6.

[0158] Step 402: Connect the test cell to a multi-channel - electrochemical workstation.

[0159] Connect the positive electrode of the test cell to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel - electrochemical workstation;

[0160] Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel - electrochemical workstation;

[0161] Connect the negative electrode of the test cell to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel - electrochemical workstation;

[0162] Connect the negative electrode of the test cell to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel - electrochemical workstation.

[0163] Among them, the model of the multi-channel - electrochemical workstation is Gamry Interface 5000P.

[0164] Step 403: Conduct a dissolution current test on the test cell: Perform cyclic voltammetry on the working electrode WE2, with a scanning voltage rate of V step (mv / s), the starting scanning voltage is the starting scanning voltage of V star , the upper scanning voltage limit is V ub (mv), the lower scanning voltage limit is V lb (mv), the scanning path is from V star to V ub and then back to V lb and then to V star , and record the corresponding response current I2 during the entire test process.

[0165] Among them, the scanning voltage rate V step is 1mV / s, and the starting scanning voltage V staris 2V, the upper limit voltage of the scan is V ub is 3V, the lower limit voltage of the scan is V lb is 1V, the cyclic voltammetry test results are as Figure 7 shown

[0166] Step 404: Conduct a deposition current test on the test cell: While conducting the dissolution current test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I1 during the entire test process

[0167] Among them, apply a specified excitation voltage V to the working electrode WE1 polar is 1V, the response current I1 is as Figure 8 shown

[0168] Step 405: Calculate the transition metal capture rate η of the test cell. The calculation formula is as follows

[0169]

[0170] Among them, t is the scan time of the cyclic voltammetry test during the dissolution current test of the test cell. After calculation, the transition metal capture rate η of the test cell is 80.35%

[0171] Step 406: Assemble the test cell to be tested: Assemble the test cell to be tested in the order of positive electrode - separator - detection sensor - separator - negative electrode to form a test battery to be tested, so that a detection sensor is arranged between the positive electrode and the negative electrode of the test cell to be tested

[0172] Among them, the active material of the positive electrode of the test cell to be tested is LiNi 0.5 Mn 1.5 O4. The test sensor, separator, and electrolyte are the same as those in Step 401

[0173] Step 407: Connect the test cell to be tested to a multi-channel electrochemical workstation: Connect the positive electrode of the test cell to be tested to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation

[0174] Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation

[0175] Connect the negative electrode of the test cell to be tested to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation

[0176] Connect the negative electrode of the test cell to be tested to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation

[0177] Step 408: Conduct a working condition test on the battery cell to be tested: Charge from the open-circuit voltage to 5V at 0.1C, and the voltage curve during the charging process is as Figure 9 shown.

[0178] Step 409: Conduct a transition metal deposition current test on the battery cell to be tested: While conducting the working condition test, apply a specified excitation voltage V polar to the working electrode WE1, and record the corresponding response current I3 during the entire test process.

[0179] Among them, the excitation voltage V polar is set to 1V, and the response current I3 is as Figure 9 shown.

[0180] Step 410: Calculate the dissolution amount of the transition metal in the battery cell to be tested. The calculation formula is as follows:

[0181]

[0182] Among them, I3 is the response current corresponding to the battery cell to be tested in the transition metal deposition current test, F is the Faraday constant, Z is 2, M is the relative atomic mass of manganese Mn element, which is 54.938 g / mol, m sensor is the mass of the captured manganese Mn element, t is the scanning time corresponding to the battery cell to be tested in the transition metal deposition current test, and m total is the dissolution amount of the manganese Mn element in the battery cell to be tested.

[0183] After calculation, the dissolution amount of the manganese Mn element in the battery cell to be tested is 0.017 g / Ah.

[0184] By using the lithium-ion battery cell and the detection method of the transition metal dissolution amount provided in the embodiments of the present disclosure, the following technical effects can be achieved:

[0185] Real-time monitoring: Without disassembling the battery or extracting a specific structure, in-situ and online monitoring of the transition metal dissolution process of the battery can be realized, and real-time data can be obtained.

[0186] High efficiency and accuracy: Simplify the pretreatment steps, reduce the detection time, and improve the detection efficiency and accuracy.

[0187] Low equipment dependence: Do not need to rely on large-scale detection equipment such as inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma atomic absorption spectrometry (ICP-AAS).

[0188] Guiding application: The dissolution amount of the transition metal of the entire battery can be quantitatively calculated, thereby providing key data support for evaluating the battery performance, optimizing the design of the positive and negative electrode materials, and improving the battery life.

[0189] Meanwhile, through the test method of the present application, the dissolution mechanism of transition metals in lithium-ion batteries can be more profoundly understood, thus laying a foundation for improving the performance and stability of the batteries.

[0190] The above description and drawings fully illustrate the embodiments of the present disclosure so that those skilled in the art can practice them. Other embodiments may include structural and other changes. Embodiments merely represent possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations may vary. Parts and features of some embodiments may be included in or substituted for parts and features of other embodiments. The embodiments of the present disclosure are not limited to the structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present disclosure is only limited by the appended claims.

Claims

1. A lithium-ion cell, comprising a wound core formed by winding a positive electrode sheet, a separator, and a negative electrode sheet, an electrolyte, and a metal casing for placing the wound core. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface thereof. The positive electrode active material layer includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, spinel lithium manganate, spinel lithium nickel manganate, and layered lithium manganate, wherein, The dissolution amount of transition metal Mn in the battery cell ≤ 0.02 g / Ah.

2. The lithium-ion battery cell according to claim 1, wherein the dissolved amount of transition metal Mn is obtained by the following detection method, characterized in that Including: According to the following formula, calculate the transition metal capture rate η of the test battery cell: Wherein, I1 is the response current corresponding to the test battery cell during the deposition current test, I2 is the response current corresponding to the test battery cell during the dissolution current test, and t is the scanning time of the cyclic voltammetry test during the dissolution current test of the test battery cell; Assemble the battery cell to be tested, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the battery cell to be tested; According to the following formula, calculate the dissolution amount of the transition metal of the battery cell to be tested: Among them, I3 is the response current corresponding to the test cell during the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge number after oxidation of the target element to be measured, M is the relative atomic mass of the target element to be measured, and m sensor is the mass of the captured transition metal, and m total is the dissolution amount of the transition metal of the test cell to be tested, and t is the scanning time corresponding to the test cell during the transition metal deposition current test.

3. The lithium-ion cell according to claim 2, wherein Before calculating the transition metal capture rate η of the test battery cell, it further includes: Assemble the test battery cell, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the test battery cell; Connect the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method; Through the electrochemical workstation, simultaneously perform a dissolution current test and a deposition current test on the test battery cell, and respectively obtain the response current I1 corresponding to the deposition current test process and the response current I2 corresponding to the dissolution current test process.

4. The lithium-ion cell according to claim 3, characterized in that, Connect the test battery cell to a multi-channel electrochemical workstation according to a preset wiring method, including: Connect the positive electrode of the test battery cell to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation; Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation; Connect the negative electrode of the test battery cell to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation; Connect the negative electrode of the test battery cell to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

5. The lithium ion cell according to claim 4, wherein Simultaneously perform a dissolution current test and a deposition current test on the test battery cell, including: Cyclic voltammetry test is carried out on the working electrode WE2, and the scanning voltage rate is V step (mv / s), and the starting scanning voltage is V star , the upper limit scanning voltage is V ub (mv), and the lower limit scanning voltage is V lb (mv), and the scanning path is from V star to V ub and then back to V lb and then to V star , and the corresponding response current I2 during the whole test process is recorded; While performing the dissolution current test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I1 throughout the test process.

6. The lithium ion cell according to claim 5, characterized in that, The scanning starting voltage V star is the open-circuit voltage of the cell to be tested. The range of the scanning speed V step is 0.01 mV / s to 20 mV / s. The scanning upper limit voltage V ub is less than 5 V, and the scanning lower limit voltage V lb is greater than 1 V. The excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

7. The lithium-ion battery cell according to claim 2, characterized in that, After assembling the battery cell to be tested, it further includes: Connect the battery cell to be tested to a multi-channel electrochemical workstation according to a preset wiring method; Through the electrochemical workstation, simultaneously perform a working condition test and a transition metal deposition current test on the battery cell to be tested, and obtain the response current I3 corresponding to the transition metal deposition current test.

8. The lithium-ion cell according to claim 7, wherein, Connect the battery cell to be tested to a multi-channel electrochemical workstation according to a preset wiring method, including: Connect the positive electrode of the battery cell to be tested to the working electrode WE2 and the working sensing electrode WS2 of the second channel of the multi-channel electrochemical workstation; Connect the detection sensor to the working electrode WE1 and the working sensing electrode WS1 of the first channel of the multi-channel electrochemical workstation; Connect the negative electrode of the battery cell to be tested to the counter electrode CE1 of the first channel and the counter electrode CE2 of the second channel of the multi-channel electrochemical workstation; Connect the negative electrode of the battery cell to be tested to the reference electrode RE1 of the first channel and the reference electrode RE2 of the second channel of the multi-channel electrochemical workstation.

9. The lithium-ion battery cell according to claim 8, wherein, Simultaneously perform a working condition test and a transition metal deposition current test on the battery cell to be tested, including: Simultaneously perform constant current, constant voltage, constant power charge and discharge or mixed working condition tests on the battery cell to be tested; While conducting the operating condition test, apply a specified excitation voltage V to the working electrode WE1 polar , and record the corresponding response current I3 throughout the test process.

10. The lithium-ion battery cell according to claim 9, wherein The excitation voltage V polar is less than the electrode potential of the element to be measured with respect to lithium and greater than the reduction potential of the electrolyte.

11. The lithium-ion battery cell according to any one of claims 1 to 10, characterized in that, The detection sensor is made of platinum or gold, in a mesh shape, with the wire diameter of the mesh being 1-50 μm and the hole diameter of the mesh being 1-50 μm.

12. The lithium-ion battery cell according to any one of claims 1 to 10, characterized in that, The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer on the surface of the positive electrode current collector. Among them, the positive electrode current collector is a transition metal sheet or a metal mesh, made of copper, nickel, cobalt, iron, manganese or aluminum.

13. The lithium-ion battery cell according to any one of claims 1 to 10, characterized in that, The negative electrode sheet is a lithium sheet; or a metal sheet or a metal mesh made of platinum, gold or silver.

14. A method for detecting the dissolution amount of transition metal, comprising: Calculating the transition metal capture rate η of the test battery cell according to the following formula: wherein, I1 is the response current corresponding to the test battery cell during the deposition current test, I2 is the response current corresponding to the test battery cell during the dissolution current test, and t is the scanning time of the cyclic voltammetry test during the dissolution current test of the test battery cell; Assembling the battery cell to be tested, wherein a detection sensor is arranged between the positive electrode and the negative electrode of the battery cell to be tested; Calculating the dissolution amount of the transition metal of the battery cell to be tested according to the following formula: Wherein, I3 is the response current corresponding to the test cell during the transition metal deposition current test, F is the Faraday constant, Z is the ionic charge number after oxidation of the target element to be measured, M is the relative atomic mass of the target element to be measured, and m sensor is the mass of the captured transition metal, and m total is the dissolution amount of the transition metal of the test cell to be tested, and t is the scanning time corresponding to the test cell during the transition metal deposition current test.

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