Lithium ion battery based on double battery cells and preparation method thereof

Abstract

The invention provides a lithium ion battery based on double battery cells and a preparation method thereof, and the lithium ion battery comprises a first battery cell which comprises a plurality of first negative electrodes distributed at intervals and first positive electrodes arranged between the adjacent first negative electrodes in a laminated manner; the second battery cell and the first battery cell are arranged in a laminated manner, and the second battery cell comprises a plurality of second negative electrodes which are distributed at intervals and second positive electrodes which are arranged between the adjacent second negative electrodes in a laminated manner; wherein the second positive electrode is used as a first reference electrode and adopts a positive electrode active material with a characteristic voltage platform. According to the lithium ion battery based on the double battery cells and the preparation method of the lithium ion battery, the second positive electrode serves as the first reference electrode, the potential of the first reference electrode can be stabilized on a characteristic voltage platform by means of the charge capacity of the second battery cell, meanwhile, the positive electrode active material is adopted, use of active metal lithium is avoided, and the service life of the lithium ion battery is prolonged. Therefore, the preparation environment requirement and the assembly complexity of the lithium ion battery are effectively reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular to a dual-cell based lithium-ion battery and a preparation method thereof. Background Art

[0002] The application of lithium-ion batteries in pure electric vehicles and other fields is becoming increasingly popular. At the same time, the market has put forward increasingly stringent requirements on the charging rate of lithium-ion batteries for the convenience of pure electric vehicles and other products. The improvement of the fast charging capability of lithium-ion batteries has attracted the attention of researchers. However, in the design process of fast-charging batteries, there is a "trade-off effect". High-rate charging will cause the accelerated attenuation of battery performance such as capacity and output power. These characteristics often affect and restrict each other.

[0003] The reference electrode, as a sensor inside the battery, can obtain the potential change curves of the positive and negative electrodes during the charge and discharge process, especially the lithium insertion potential change of the negative electrode graphite. At the same time, based on the lithium precipitation potential criterion (0Vv.Li / Li + ), can prevent the negative electrode potential from crossing the lithium deposition boundary during fast charging, reducing the risk of lithium deposition during fast charging. At present, the material of the reference electrode is mostly lithium metal. However, the high activity of lithium metal leads to poor stability of the reference electrode, which is easily oxidized by air and even has the risk of spontaneous combustion when in contact with water in the air. It is also easy to have side reactions with the electrolyte, which leads to higher requirements for the preparation environment of the battery and more complicated assembly. Summary of the invention

[0004] The present disclosure aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of the present disclosure is to provide a dual-cell based lithium-ion battery and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides a dual-cell based lithium-ion battery, comprising: a first cell, the first cell comprising: a plurality of first negative electrodes distributed at intervals and a first positive electrode stacked between adjacent first negative electrodes; a second cell, the second cell and the first cell are stacked, and the second cell comprises: a plurality of second negative electrodes distributed at intervals and a second positive electrode stacked between adjacent second negative electrodes; wherein the second positive electrode serves as a first reference electrode, and adopts a positive electrode active material with a characteristic voltage platform.

[0007] Optionally, the positive electrode active material of the second positive electrode is lithium iron phosphate material; and / or, the positive electrode active material of the second positive electrode is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, or the iron content in the lithium iron manganese phosphate material is greater than the manganese content.

[0008] Optionally, the lithium-ion battery also includes: a copper wire, which is arranged between the second negative electrode and the second positive electrode in the second battery cell that are farthest from the first battery cell, and the copper wire is provided with a lithium-plated layer using the second positive electrode and the second negative electrode as lithium sources, and the copper wire serves as a second reference electrode and is used for calibrating the potential of the first reference electrode.

[0009] Optionally, the lithium-ion battery further includes: a plurality of first diaphragms, which are respectively arranged between adjacent first negative electrodes and first positive electrodes, between adjacent first negative electrodes and second negative electrodes, and between adjacent second negative electrodes and second positive electrodes, wherein the copper wire is located between the second negative electrode farthest from the first battery cell in the second battery cell and the first diaphragm; and a second diaphragm, which is arranged between adjacent second negative electrodes and the copper wire.

[0010] Optionally, the copper wire is arranged along the width direction of the lithium-ion battery, and the length of the copper wire in the overlapping part with the second positive electrode along the thickness direction of the lithium-ion battery ranges from 1 / 2 to 3 / 4 of the width of the second positive electrode.

[0011] Optionally, the first negative electrode is provided with a first pole ear, and the first positive electrode is provided with a second pole ear; the second negative electrode is provided with a third pole ear, and the second positive electrode is provided with a fourth pole ear; the copper wire is provided with a fifth pole ear; wherein the first pole ear and the second pole ear are respectively arranged at the top of the lithium-ion battery, and the third pole ear and the fourth pole ear are respectively arranged at the bottom of the lithium-ion battery, and the fifth pole ear is arranged on the side of the lithium-ion battery between the top and the bottom.

[0012] A second aspect of the present disclosure provides a method for preparing a dual-cell lithium-ion battery, the method comprising: distributing a plurality of first negative electrodes at intervals, and arranging a first positive electrode in layers between adjacent first negative electrodes to form a first cell; distributing a plurality of second negative electrodes at intervals, and arranging a second positive electrode in layers between adjacent second negative electrodes to form a second cell, wherein the second positive electrode serves as a first reference electrode and adopts a positive electrode active material with a characteristic voltage platform; arranging the first cell and the second cell in layers, and packaging them to obtain a semi-finished product; and sequentially baking, injecting, forming, and dividing the capacity of the semi-finished product to obtain the lithium-ion battery.

[0013] Optionally, the preparation method also includes: when the positive electrode active material of the second positive electrode is lithium iron phosphate material, regulating the potential of the first reference electrode to a first voltage platform corresponding to the lithium iron phosphate material; when the positive electrode active material of the second positive electrode is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, regulating the potential of the first reference electrode to a second voltage platform corresponding to the lithium iron manganese phosphate material; when the positive electrode active material of the second positive electrode is lithium iron manganese phosphate material, and the iron content in the lithium iron manganese phosphate material is greater than the manganese content, regulating the potential of the first reference electrode to a third voltage platform corresponding to the lithium iron manganese phosphate material.

[0014] Optionally, the preparation method also includes: placing a copper wire between the second negative electrode and the second positive electrode farthest from the first battery cell in the second battery cell to serve as a second reference electrode; connecting the first reference electrode to the positive electrode of a lithium plating device, and connecting the second reference electrode to the negative electrode of the lithium plating device, and forwardly plating lithium on the copper wire with a preset lithium plating current and a preset lithium plating time; disconnecting the first reference electrode from the positive electrode of the lithium plating device, and connecting the second negative electrode to the positive electrode of the lithium plating device, and reversely plating lithium on the copper wire with the preset lithium plating current and the preset lithium plating time to form a lithium plating layer on the copper wire with the second positive electrode and the second negative electrode as lithium sources.

[0015] Optionally, the preparation method also includes: connecting the first reference electrode to the positive electrode of the test equipment, and connecting the second reference electrode to the negative electrode of the test equipment; obtaining the potential difference between the first reference electrode and the second reference electrode according to the test equipment, and using the potential difference as the lithium potential value of the first reference electrode.

[0016] Optionally, the preparation method also includes: connecting the first positive electrode and the first negative electrode for chemical formation to form a solid electrolyte interface film on the surface of the first negative electrode; connecting the second positive electrode and the second negative electrode for chemical formation to form a solid electrolyte interface film on the surface of the second negative electrode; wherein the chemical formation includes: after a first preset standing time, charging with a first preset rate constant current for a first preset charging time; after a second preset standing time, charging with a second preset rate constant current for a second preset charging time; after a third preset standing time, completing the chemical formation; the second preset rate is greater than the first preset rate, and the second preset charging time is greater than the first preset charging time.

[0017] Optionally, the preparation method further includes: connecting the first positive electrode and the first negative electrode for capacity division to obtain the actual capacity value of the first battery cell; connecting the second positive electrode and the second negative electrode for capacity division to obtain the actual capacity value of the second battery cell; wherein the capacity division of the first battery cell includes: after a fourth preset rest time, charging to a first preset voltage with a third preset rate of constant current and constant voltage, with a cut-off current of a preset current; after a fifth preset rest time, discharging to a second preset voltage with a fourth preset rate of constant current; waiting for a sixth preset rest time; repeating the above steps according to a preset number of times. The method comprises the following steps, wherein the capacity of the last cycle is taken as the actual capacity value of the first battery cell; the capacity division of the second battery cell comprises: after a fourth preset resting time, charging to a third preset voltage with a current constant current and constant voltage of a third preset rate, with a cut-off current being a preset current; after a fifth preset resting time, discharging to a second preset voltage with a current constant current of a fourth preset rate; waiting for a sixth preset resting time; repeating the above steps according to a preset number of times, taking the capacity of the last cycle as the actual capacity value of the second battery cell; charging for a third preset charging time with a current constant current of a fifth preset rate; and waiting for a seventh preset resting time.

[0018] The technical solution provided by the present disclosure may have the following beneficial effects:

[0019] By using the second positive electrode as the first reference electrode, the charge of the second battery cell can be used to stabilize the potential of the first reference electrode at a characteristic voltage platform, thereby reducing the influence of the first reference electrode on the first battery cell. At the same time, the use of positive electrode active materials allows the first reference electrode to avoid the use of active metallic lithium, and has more stable chemical properties and good compatibility with the electrolyte, thereby effectively reducing the preparation environment requirements and assembly complexity of lithium-ion batteries, and thus enabling efficient preparation of lithium-ion batteries under conventional preparation environments.

[0020] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 is an exploded diagram of a dual-cell lithium-ion battery according to an embodiment of the present disclosure;

[0023] Figure 2 is an assembly diagram of a dual-cell lithium-ion battery according to an embodiment of the present disclosure;

[0024] Figure 3is a comparison diagram of charging curves of different materials proposed in an embodiment of the present disclosure;

[0025] Figure 4 is a schematic diagram of capacity and voltage platform regulation proposed in an embodiment of the present disclosure;

[0026] Figure 5 is a curve diagram of positive and negative electrode voltage test during charging proposed by an embodiment of the present disclosure;

[0027] As shown in the figure: 1, first battery cell, 11, first negative electrode, 12, first positive electrode, 13, first pole ear, 14, second pole ear;

[0028] 2. a second battery cell, 21. a second negative electrode, 22. a second positive electrode, 23. a third electrode tab, 24. a fourth electrode tab;

[0029] 3. Copper wire, 4. First diaphragm, 5. Second diaphragm, 6. Fifth pole ear. DETAILED DESCRIPTION

[0030] Embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present disclosure, and should not be construed as limitations on the present disclosure. On the contrary, the embodiments of the present disclosure include all changes, modifications, and equivalents that fall within the spirit and connotation of the appended claims.

[0031] like Figure 1 As shown, the embodiment of the present disclosure proposes a dual-cell lithium-ion battery, comprising: a first cell 1 and a second cell 2, the first cell 1 comprising: a plurality of first negative electrodes 11 distributed at intervals and a first positive electrode 12 stacked between adjacent first negative electrodes 11, the second cell 2 and the first cell 1 are stacked, and the second cell 2 comprises: a plurality of second negative electrodes 21 distributed at intervals and a second positive electrode 22 stacked between adjacent second negative electrodes 21. The second positive electrode 22 serves as a first reference electrode, and uses a positive electrode active material with a characteristic voltage platform.

[0032] It can be understood that, since the plurality of first negative electrodes 11 are distributed at intervals, and the first positive electrode 12 is arranged between adjacent first negative electrodes 11, the first negative electrode 11 and the first positive electrode 12 constitute the stacked structure of the first battery cell 1, and since the plurality of second negative electrodes 21 are distributed at intervals, and the second positive electrode 22 is arranged between adjacent second negative electrodes 21, the second negative electrode 21 and the second positive electrode 22 constitute the stacked structure of the second battery cell 2. Thus, based on the stacked arrangement structure of the first battery cell 1 and the second battery cell 2, the dual-cell structure of the lithium-ion battery is realized.

[0033] Moreover, by using the second positive electrode 22 as the first reference electrode, the charge (State of Charge, SOC) of the second battery cell 2 can be used to stabilize the potential of the first reference electrode at a characteristic voltage platform, thereby reducing the influence of the first reference electrode on the first battery cell 1. At the same time, the use of positive electrode active materials allows the first reference electrode to avoid the use of active metallic lithium, and has more stable chemical properties and good compatibility with the electrolyte, thereby effectively reducing the preparation environment requirements and assembly complexity of lithium-ion batteries, and thus enabling efficient preparation of lithium-ion batteries under conventional preparation environments.

[0034] It should be noted that the characteristic voltage platform refers to the voltage platform corresponding to the material itself. Selecting a positive electrode active material with an obvious voltage platform as the first reference electrode avoids the risk of water and air oxidation corrosion caused by using highly active lithium metal as a reference electrode, as well as the risk of side reactions with the electrolyte. The requirements for the preparation environment are lower than those for lithium metal, the assembly is simpler and more efficient, and the prepared lithium-ion battery has higher stability.

[0035] The first battery cell 1 is the main body of the lithium-ion battery. The first battery cell 1 uses the cooperation of the first negative electrode 11 and the first positive electrode 12 to store and release electric energy. The specific type of the first battery cell 1 can be set according to actual needs and is not limited to this. For example, the first negative electrode 11 and the first positive electrode 12 are both obtained by rolling and cutting to obtain battery pole pieces. The first negative electrode 11 and the first positive electrode 12 are parallel to each other and stacked. The size of the first negative electrode 11 is larger than that of the first positive electrode 12. Since multiple first negative electrodes 11 are distributed at intervals and the first positive electrodes 12 are stacked between adjacent first negative electrodes 11, when the first positive electrode 12 is single or multiple, the first negative electrode 11 and the first positive electrode 12 are staggered, and the two outermost pole pieces are both the first negative electrode 11.

[0036] The specific type of the first positive electrode 12 can be set according to actual needs and is not limited to this. For example, the active material of the first positive electrode 12 can be selected from any one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, and nickel-cobalt-manganese ternary materials. The positive electrode active material is coated on a substrate, and the substrate can be a carbon-coated aluminum foil.

[0037] The specific type of the first negative electrode 11 can be set according to actual needs, and there is no limitation on this. For example, the active material of the first negative electrode 11 can be graphite, which is coated on a substrate, and the substrate can be copper foil.

[0038] The second battery cell 2 is an auxiliary part of the lithium-ion battery. The second battery cell 2 realizes the first reference electrode and ensures the stability of the potential of the first reference electrode by the cooperation of the second negative electrode 21 and the second positive electrode 22. The specific type of the second battery cell 2 can be set according to actual needs and is not limited to this. For example, the second negative electrode 21 and the second positive electrode 22 are both obtained by rolling and cutting to obtain battery pole pieces. The second negative electrode 21 and the second positive electrode 22 are parallel to each other and arranged in layers. The size of the second negative electrode 21 is larger than that of the second positive electrode 22. At the same time, the overall structure formed by the second negative electrode 21 and the second positive electrode 22 is stacked with the overall structure formed by the first negative electrode 11 and the first positive electrode 12. Since the multiple second negative electrodes 21 are distributed at intervals and the second positive electrodes 22 are stacked between adjacent second negative electrodes 21, when the second positive electrode 22 is single or multiple, the second negative electrode 21 and the second positive electrode 22 are staggered, and the two outermost pole pieces are both the second negative electrode 21.

[0039] Preferably, the second positive electrode 22 is single, and the second negative electrodes 21 are two, which are arranged on both sides of the second positive electrode 22, respectively. That is, two second negative electrodes 21 and a second positive electrode 22 arranged between the two second negative electrodes 21 are additionally arranged on the outside of the first battery cell 1 to realize the arrangement of the first reference electrode.

[0040] Wherein, through the structural coordination of the first battery cell 1 and the second battery cell 2 , the first positive electrode 12 and the second positive electrode 22 are separated by at least two negative electrode sheets.

[0041] The specific type of the second positive electrode 22 can be set according to actual needs, and there is no limitation on this. For example, the active material of the second positive electrode 22 can be selected from any one of lithium iron phosphate and lithium manganese iron phosphate materials. The positive electrode active material is coated on a substrate, and the substrate can be a carbon-coated aluminum foil. Among them, except for the material, the parameters of the second positive electrode 22 and the first positive electrode 12 are consistent, and other parameters such as coating surface density, rolling thickness, pole piece punching area, etc.

[0042] The specific type of the second negative electrode 21 can be set according to actual needs, and there is no limitation on this. For example, the active material of the second negative electrode 21 can be graphite, which is coated on a substrate, and the substrate can be copper foil. The parameters of the second negative electrode 21 and the first negative electrode 11 are consistent, such as coating surface density, rolling thickness, and pole piece punching area.

[0043] The fast charging capability of a battery depends on the rapid lithium insertion capability of the negative electrode. Graphite is the main negative electrode material for lithium-ion batteries. The slow interface dynamics and large overpotential non-uniformity (polarization) on the graphite surface make lithium deposition on the graphite surface easy to occur, leading to short circuit and capacity decay. Therefore, evaluating the rapid lithium insertion capability and lithium plating boundary current of the graphite negative electrode is an important part of the development of fast-charging lithium-ion battery technology.

[0044] Thus, the first reference electrode, that is, the second positive electrode 22, can be used as a sensor inside the battery to obtain the positive and negative electrode potential change curves during the charge and discharge process, especially the lithium insertion potential change of the negative electrode graphite, and at the same time based on the lithium precipitation potential criterion (0Vvs.Li / Li + ), which can prevent the negative electrode potential from crossing the lithium deposition boundary during fast charging and reduce the risk of lithium deposition during fast charging.

[0045] The voltage platform refers to the stable voltage range that the positive electrode material can provide when the battery is working. Specifically, the voltage platform is essentially the so-called "equilibrium potential", that is, the potential state when the electrochemical reaction reaches equilibrium. The curve platform at this time can be regarded as the result of subtracting the polarization potential from the standard equilibrium potential.

[0046] In some embodiments, the positive electrode active material of the second positive electrode 22 is lithium iron phosphate material, and / or the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, or the iron content in the lithium iron manganese phosphate material is greater than the manganese content.

[0047] It is understandable that when the positive electrode active material of the second positive electrode 22 is lithium iron phosphate material, the second positive electrode 22 has a corresponding first voltage platform, so that the potential of the first reference electrode can be stabilized at the first voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0048] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, the second positive electrode 22 has a corresponding second voltage platform, so that the potential of the first reference electrode can be stabilized on the second voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0049] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the iron content in the lithium iron manganese phosphate material is greater than the manganese content, the second positive electrode 22 has a corresponding third voltage platform, so that the potential of the first reference electrode can be stabilized at the third voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0050] It should be noted that the reference Figure 3 , Figure 4 According to the following table, the positive electrode active material of the second positive electrode 22 in this embodiment is preferably lithium manganese iron phosphate (LiMn x Fe 1-x PO4), the ionic radius of manganese and iron is close, and they have similar chemical properties, so that lithium iron phosphate and lithium manganese iron phosphate both have orthorhombic olivine crystal structure, and their physical and chemical properties are also similar. The charging and discharging of lithium iron phosphate has a voltage platform corresponding to Fe 3+ / Fe2+ Valence state changes, lithium manganese iron phosphate has two voltage platforms corresponding to Fe 3+ / Fe 2+ and Mn 3+ / Mn 2+ Valence state changes. It can be seen from the material's charge curve that the voltage is in the platform area after a certain charge, and the voltage remains stable at this time; after the second battery cell 2 is constant-capacity, it is first discharged to 2.5V at a current rate of 0.1C-0.3C, and then charged to the corresponding charge interval (SOC interval) corresponding to the corresponding platform area at a current rate of 0.1C-0.3C. Since there are differences in the ratio of manganese to iron in different platform areas in lithium manganese iron phosphate, it is adjusted to the corresponding charge interval according to the different ratios of manganese to iron.

[0051] Among them, the first reference electrode material is lithium manganese iron phosphate. Since manganese and iron are close in ion radius and have similar chemical properties, a certain proportion of manganese and iron will not significantly affect the original structure. They both belong to the orthorhombic olivine crystal structure, and the discharge mechanism is similar to that of lithium iron phosphate, which is a two-phase conversion reaction. The lithium manganese iron phosphate material has two voltage platforms of about 4.1V (the second voltage platform) and 3.4V (the third voltage platform), corresponding to Fe 3+ / Fe 2+ and Mn 3+ / Mn 2+ The valence state changes and the voltage is controlled in the corresponding voltage platform area with high element content to adjust the stability of the reference electrode potential and ensure that the overall system is less affected by potential fluctuations.

[0052] At the same time, manganese-doped materials are cheaper, and lithium manganese iron phosphate materials have excellent thermal stability and low oxidizability, which improves the material's anti-interference ability when used as a reference electrode.

[0053] SOC adjustment range of materials with different ferromanganese content:

[0054]

[0055] like Figure 1 As shown, in some embodiments, the lithium-ion battery further includes: a copper wire 3, which is arranged between the second negative electrode 21 and the second positive electrode 22 in the second battery cell 2 which are farthest from the first battery cell 1, and the copper wire 3 is provided with a lithium-plated layer using the second positive electrode 22 and the second negative electrode 21 as lithium sources, and the copper wire 3 serves as a second reference electrode and is used for potential calibration of the first reference electrode.

[0056] It is understandable that using the lithium-plated copper wire 3 as the second reference electrode to calibrate the potential of the first reference electrode can accurately adjust the first reference electrode to the characteristic voltage platform, thereby ensuring the potential stability of the first reference electrode.

[0057] Among them, a positive electrode active material with a characteristic voltage platform is selected as the first reference electrode, which avoids the risk of low dynamic service life caused by the limited amount of lithium plating on the copper wire 3. At the same time, the lithium source for the lithium plating of the second reference electrode comes from the second positive electrode 22 and the second negative electrode 21 in the second battery cell 2, which has little impact on the first battery cell 1. Moreover, the second reference electrode after the copper wire 3 is plated with lithium is only used for potential calibration of the first reference electrode, and will not be affected by the short service life on the test results. After multiple cycles, if the first reference electrode needs to be re-calibrated in terms of potential, the copper wire 3 can be re-plated with lithium for potential calibration due to the shedding of the lithium layer caused by galvanic corrosion, thereby ensuring the long-term use of the reference electrode.

[0058] It should be noted that the copper wire 3 is arranged between the second negative electrode 21 and the second positive electrode 22 in the second battery cell 2, and the second positive electrode 22 and the second negative electrode 21 are used as lithium sources for electrochemical lithium plating for potential calibration of the first reference electrode. The specific type of the copper wire 3 can be set according to actual needs, and there is no limitation to this. For example, the copper wire 3 can be an enameled copper wire 3, and the copper wire 3 is depainted at the top end inside the second battery cell 2, and the length is maintained at 1cm-2cm.

[0059] In the relevant embodiments using active metallic lithium as the reference electrode, when lithium is plated using metals such as copper wire 3 as the current collector, some side reactions will occur due to the high reactivity of lithium, which will reduce the coulombic efficiency of the lithium plating process and the thickness of the lithium plating will also be limited. Due to the particularity of the position of the lithium-plated reference electrode (between the positive and negative electrodes), the battery charging and discharging process will lead to redistribution of the lithium layer and exposure of the copper wire 3 current collector, causing severe galvanic corrosion and causing the lithium layer to fall off, affecting the service life of the reference electrode. In the present embodiment, since the positive electrode active material with a characteristic voltage platform is used as the first reference electrode, the above-mentioned problems can be effectively avoided, and the risk of low dynamic service life due to the limited amount of lithium plating on the copper wire 3 can be avoided.

[0060] like Figure 1 As shown, in some embodiments, the lithium-ion battery further includes: a plurality of first separators 4 and a second separator 5, wherein the plurality of first separators 4 are respectively arranged between adjacent first negative electrodes 11 and first positive electrodes 12, between adjacent first negative electrodes 11 and second negative electrodes 21, and between adjacent second negative electrodes 21 and second positive electrodes 22, wherein the copper wire 3 is located between the second negative electrode 21 farthest from the first battery cell 1 in the second battery cell 2 and the first separator 4, and the second separator 5 is arranged between the adjacent second negative electrode 21 and the copper wire 3.

[0061] It can be understood that, since the plurality of first separators 4 are respectively arranged between the adjacent first negative electrode 11 and the first positive electrode 12, between the adjacent first negative electrode 11 and the second negative electrode 21, and between the adjacent second negative electrode 21 and the second positive electrode 22, the first separator 4 can be used to cover and separate the adjacent first negative electrode 11 and the first positive electrode 12, between the adjacent first negative electrode 11 and the second negative electrode 21, and between the adjacent second negative electrode 21 and the second positive electrode 22, and since the copper wire 3 is located between the second negative electrode 21 farthest from the first battery cell 1 in the second battery cell 2 and the first separator 4, and the second separator 5 is arranged between the adjacent second negative electrode 21 and the copper wire 3, the first separator 4 can be used to cover and separate the copper wire 3 and the second positive electrode 22, and the second separator 5 can be used to cover and separate the copper wire 3 and the second negative electrode 21. Therefore, through the cooperation of the plurality of first separators 4 and the second separator 5, the short circuit risk of the lithium-ion battery can be avoided, thereby ensuring the safe and stable operation of the lithium-ion battery.

[0062] It should be noted that the multiple first separators 4 are used to cover and separate the adjacent first negative electrode 11 and the first positive electrode 12, the adjacent first negative electrode 11 and the second negative electrode 21, and the adjacent second negative electrode 21 and the second positive electrode 22. The specific type of the first separator 4 can be set according to actual needs, and there is no limitation on this. For example, the material of the first separator 4 can be one of a polypropylene microporous membrane, a polyethylene microporous membrane, and a polypropylene and polyethylene composite membrane. The thickness of the first separator 4 can range from 9μm to 20μm. Among them, the outer side of the first negative electrode 11 farthest from the second battery cell 2 in the first battery cell 1 and the outer side of the second negative electrode 21 farthest from the first battery cell 1 in the second battery cell 2 can also be covered and separated by the first separator 4, so that the first battery cell 1 and the second battery cell 2 can be integrated and packaged in the shell after preparation.

[0063] The second separator 5 is used to cover and separate the adjacent second negative electrode 21 and the copper wire 3. The specific type of the second separator 5 can be set according to actual needs, and there is no limitation on this. For example, the material of the second separator 5 can be one of a polypropylene microporous membrane, a polyethylene microporous membrane, and a polypropylene and polyethylene composite membrane. The thickness of the first separator 4 can range from 9μm to 20μm. Among them, the second separator 5 is completely consistent with the first separator 4 in material, but the size is different. The area of ​​the second separator 5 is smaller than that of the first separator 4. The second separator 5 only ensures that the copper wire 3 can be completely covered to avoid short circuit with the second positive electrode 22 and the second negative electrode 21.

[0064] In some embodiments, the copper wire 3 is arranged along the width direction of the lithium-ion battery, and the length of the copper wire 3 overlapping the second positive electrode 22 along the thickness direction of the lithium-ion battery is 1 / 2-3 / 4 of the width of the second positive electrode 22.

[0065] It can be understood that since the length range of the copper wire 3 and the overlapping part of the second positive electrode 22 along the thickness direction of the lithium-ion battery is 1 / 2-3 / 4 of the width of the second positive electrode 22, the copper wire 3 can be stably arranged between the second negative electrode 21 and the second positive electrode 22, and the second positive electrode 22 and the second negative electrode 21 can be used as lithium sources for efficient lithium plating and as second reference electrodes to accurately calibrate the potential of the first reference electrode.

[0066] It should be noted that the thickness direction of the lithium-ion battery is the stacking direction of the first positive electrode 12 and the first negative electrode 11 in the first battery cell 1, the stacking direction of the second positive electrode 22 and the second negative electrode 21 in the second battery cell 2, and the stacking direction between the first battery cell 1 and the second battery cell 2, wherein the sizes of the first positive electrode 12, the first negative electrode 11, the second positive electrode 22 and the second negative electrode 21 are close (the size of the negative electrode is larger than the size of the positive electrode) and the side faces are close to a rectangle, the width direction of the lithium-ion battery is the short side direction of the first positive electrode 12, and the length direction of the lithium-ion battery is the long side direction of the first positive electrode 12.

[0067] like Figure 2 As shown, in some embodiments, the first negative electrode 11 is provided with a first pole tab 13, the first positive electrode 12 is provided with a second pole tab 14, the second negative electrode 21 is provided with a third pole tab 23, the second positive electrode 22 is provided with a fourth pole tab 24, and the copper wire 3 is provided with a fifth pole tab 6. The first pole tab 13 and the second pole tab 14 are respectively provided at the top of the lithium-ion battery, the third pole tab 23 and the fourth pole tab 24 are respectively provided at the bottom of the lithium-ion battery, and the fifth pole tab 6 is provided on the side of the lithium-ion battery between the top and the bottom.

[0068] It can be understood that since the first negative electrode 11 is provided with a first pole ear 13, and the first positive electrode 12 is provided with a second pole ear 14, it is convenient to realize electron transmission between the first battery cell 1 and the external device by utilizing the cooperation of the first pole ear 13 and the second pole ear 14, and since the second negative electrode 21 is provided with a third pole ear 23, and the second positive electrode 22 is provided with a fourth pole ear 24, and the copper wire 3 is provided with a fifth pole ear 6, it is convenient to realize electron transmission between the second battery cell 2 and the copper wire 3 and the external device by utilizing the cooperation of the third pole ear 23, the fourth pole ear 24 and the fifth pole ear 6.

[0069] At the same time, since the first pole ear 13 and the second pole ear 14 are respectively arranged at the top of the lithium-ion battery, and the third pole ear 23 and the fourth pole ear 24 are respectively arranged at the bottom of the lithium-ion battery, and the fifth pole ear 6 is arranged on the side of the lithium-ion battery between the top and the bottom, the first pole ear 13 and the second pole ear 14 in the first battery cell 1 and the third pole ear 23 and the fourth pole ear 24 in the second battery cell 2 can be arranged close to each other, and the pole ears of the first battery cell 1, the pole ears of the second battery cell 2 and the pole ears of the copper wire 3 can be arranged far away, thereby making the wiring of the lithium-ion battery more efficient and safer.

[0070] It should be noted that the first pole ear 13, the second pole ear 14, the third pole ear 23, the fourth pole ear 24 and the fifth pole ear 6 are respectively used for the outward extension of the internal devices of the lithium-ion battery. The specific types of the first pole ear 13, the second pole ear 14, the third pole ear 23, the fourth pole ear 24 and the fifth pole ear 6 can be set according to actual needs and are not limited to this. For example, the first pole ear 13 and the third pole ear 23 are used as negative pole ears, and nickel-plated copper pole ears can be used. The second pole ear 14 and the fourth pole ear 24 are used as positive pole ears, and aluminum pole ears can be used. The fifth pole ear 6 can be a nickel-plated copper pole ear.

[0071] This embodiment provides a dual-cell structure placed in parallel and oppositely, and different positive electrodes are separated by two layers of negative electrode plates. The second positive electrode 22 is used as a reference electrode. The charge state of the second cell 2 is adjusted to make the positive electrode material in the voltage platform area, thereby ensuring the potential stability of the first reference electrode.

[0072] The present disclosure also provides a method for preparing a dual-cell lithium-ion battery, the method comprising:

[0073] S1: Distribute a plurality of first negative electrodes 11 at intervals, and stack first positive electrodes 12 between adjacent first negative electrodes 11 to form a first battery cell 1;

[0074] S2: distributing a plurality of second negative electrodes 21 at intervals, and stacking second positive electrodes 22 between adjacent second negative electrodes 21 to form a second battery cell 2, wherein the second positive electrode 22 serves as a first reference electrode and uses a positive electrode active material having a characteristic voltage platform;

[0075] S3: stacking the first battery cell 1 and the second battery cell 2, and packaging them to obtain a semi-finished product;

[0076] S4: The semi-finished product is baked, liquid-filled, formed and capacity-divided in sequence to obtain a lithium-ion battery.

[0077] It can be understood that a plurality of first negative electrodes 11 are spaced apart and a first positive electrode 12 is stacked between adjacent first negative electrodes 11, thereby forming a stacked structure of a first battery cell 1 in a lithium-ion battery, and a plurality of second negative electrodes 21 are spaced apart and a second positive electrode 22 is stacked between adjacent second negative electrodes 21, thereby forming a stacked structure of a second battery cell 2 in a lithium-ion battery. At the same time, the first battery cell 1 and the second battery cell 2 are stacked, thereby completing the preparation of a semi-finished lithium-ion battery. Finally, the prepared semi-finished product is sequentially subjected to baking, liquid injection, formation and capacity separation processes to obtain a lithium-ion battery.

[0078] Among them, the second positive electrode 22 is used as the first reference electrode, and the charge of the second battery cell 2 can be used to stabilize the potential of the first reference electrode at a characteristic voltage platform, thereby reducing the influence of the first reference electrode on the first battery cell 1. At the same time, the use of positive electrode active materials makes the first reference electrode avoid the use of active metallic lithium, and the chemical properties are more stable and have good compatibility with the electrolyte, thereby effectively reducing the preparation environment requirements and assembly complexity of lithium-ion batteries, and thus enabling efficient preparation of lithium-ion batteries under conventional preparation environments.

[0079] It should be noted that in steps S1, S2 and S3, the stacking structure of the first battery cell 1 and the second battery cell 2, and the stacking structure between the first battery cell 1 and the second battery cell 2 are prepared respectively. In the actual preparation process, the order of S1, S2 and S3 can be adjusted. Specifically, the various structures can be prepared in sequence along the order of S1, S2 and S3, and the various pole pieces can be stacked in sequence from the first battery cell 1 to the second battery cell 2. The various pole pieces can also be stacked in sequence from the second battery cell 2 to the first battery cell 1. There is no limitation to this.

[0080] After the first battery cell 1 and the second battery cell 2 are stacked, they can be packaged with an aluminum-plastic film to obtain a semi-finished product.

[0081] In some embodiments, the preparation method further comprises:

[0082] When the positive electrode active material of the second positive electrode 22 is lithium iron phosphate material, the potential of the first reference electrode is adjusted to a first voltage platform corresponding to the lithium iron phosphate material;

[0083] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, the potential of the first reference electrode is adjusted to the second voltage platform corresponding to the lithium iron manganese phosphate material;

[0084] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the iron content in the lithium iron manganese phosphate material is greater than the manganese content, the potential of the first reference electrode is adjusted to the third voltage platform corresponding to the lithium iron manganese phosphate material.

[0085] It is understandable that when the positive electrode active material of the second positive electrode 22 is lithium iron phosphate material, the first voltage platform corresponding to the lithium iron phosphate material can be used to stabilize the potential of the first reference electrode at the first voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0086] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, the second voltage platform corresponding to the lithium iron manganese phosphate material can be used to stabilize the potential of the first reference electrode on the second voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0087] When the positive electrode active material of the second positive electrode 22 is lithium iron manganese phosphate material, and the iron content in the lithium iron manganese phosphate material is greater than the manganese content, the third voltage platform corresponding to the lithium iron manganese phosphate material can be used to stabilize the potential of the first reference electrode on the third voltage platform, thereby ensuring the higher performance of the lithium-ion battery.

[0088] It should be noted that the present embodiment preferably uses lithium manganese iron phosphate material, and for lithium manganese iron phosphate material, when the manganese content in the material is high, the potential is adjusted to Mn 3+ / Mn 2+ Interval (second voltage platform), when the iron content in the material is high, adjust the potential to Fe 3+ / Fe 2+ interval (third voltage platform), and adjusted to an appropriate SOC interval according to different element contents to stabilize the potential of the first reference electrode in the voltage platform area.

[0089] With the above-mentioned potential control method, the voltage of the first reference electrode is maintained in the platform area and remains stable after charge adjustment.

[0090] In some embodiments, the preparation method further comprises:

[0091] The copper wire 3 is placed between the second negative electrode 21 and the second positive electrode 22 in the second battery cell 2 which are farthest from the first battery cell 1, so as to serve as a second reference electrode;

[0092] Connecting the first reference electrode to the positive electrode of the lithium plating device, and connecting the second reference electrode to the negative electrode of the lithium plating device, and performing forward lithium plating on the copper wire 3 with a preset lithium plating current and a preset lithium plating time;

[0093] Disconnect the connection between the first reference electrode and the positive electrode of the lithium plating equipment, connect the second negative electrode 21 and the positive electrode of the lithium plating equipment, and reversely plate lithium on the copper wire 3 with a preset lithium plating current and a preset lithium plating time to form a lithium plating layer on the copper wire 3 with the second positive electrode 22 and the second negative electrode 21 as lithium sources.

[0094] It can be understood that the first reference electrode is connected to the positive electrode of the lithium plating device, and the second reference electrode is connected to the negative electrode of the lithium plating device, so that the lithium plating device is used to perform forward lithium plating on the copper wire 3 with a preset lithium plating current and a preset lithium plating time, and the second negative electrode 21 is connected to the positive electrode of the lithium plating device, and the second reference electrode is kept connected to the negative electrode of the lithium plating device, so that the lithium plating device is used to perform reverse lithium plating on the copper wire 3 with a preset lithium plating current and a preset lithium plating time. Thus, the forward and reverse lithium plating of the copper wire 3 is achieved, and the uniform lithium plating layer formed on the copper wire 3 can be used as the second reference electrode to achieve accurate calibration of the potential of the first reference electrode.

[0095] It should be noted that the preset lithium plating current can be set according to actual needs, and there is no limitation to this. For example, the preset lithium plating current can be in the range of 2μA-8μA.

[0096] The preset lithium plating time can be set according to actual needs, and there is no limitation on this. For example, the preset lithium plating time range can be 2h-3h.

[0097] For the above-mentioned method of positive and negative lithium plating of the copper wire 3, the second reference electrode can accurately calibrate the potential of the first reference electrode.

[0098] In some embodiments, the preparation method further comprises:

[0099] Connecting a first reference electrode to the positive pole of the test device and connecting a second reference electrode to the negative pole of the test device;

[0100] The potential difference between the first reference electrode and the second reference electrode is obtained according to the test equipment, and the potential difference is used as the potential value of the first reference electrode with respect to lithium.

[0101] It can be understood that the first reference electrode is connected to the positive electrode of the test equipment, and the second reference electrode is connected to the negative electrode of the test equipment, so that the potential difference between the first reference electrode and the second reference electrode is obtained by using the test equipment, and the lithium potential value of the first reference electrode is accurately obtained based on the potential difference, thereby completing the potential calibration of the second reference electrode to the first reference electrode.

[0102] It should be noted that after the copper wire 3 is fully lithium-plated, the potential value of the second reference electrode is 0V (vs. Li / Li + ), so that the potential difference between the first reference electrode and the second reference electrode is used as the lithium potential value of the first reference electrode to achieve potential calibration.

[0103] The above potential calibration method enables the potential of the first reference electrode to be accurately controlled at a characteristic voltage platform.

[0104] In some embodiments, the preparation method further comprises:

[0105] Connecting the first positive electrode 12 and the first negative electrode 11 to form a solid electrolyte interface (SEI) on the surface of the first negative electrode 11;

[0106] The second positive electrode 22 and the second negative electrode 21 are connected to perform chemical formation to form a solid electrolyte interface film on the surface of the second negative electrode 21 .

[0107] Among them, the formation includes:

[0108] After a first preset rest time, charging with a first preset rate constant current for a first preset charging time;

[0109] After a second preset rest time, charging with a constant current of a second preset rate for a second preset charging time;

[0110] After the third preset resting time, the formation is completed.

[0111] Furthermore, the second preset rate is greater than the first preset rate, and the second preset charging time is greater than the first preset charging time.

[0112] It can be understood that the first positive electrode 12 and the first negative electrode 11 are connected, and after a first preset standing time, the first battery cell 1 is charged with a constant current of a first preset rate for a first preset charging time. Thereafter, after a second preset standing time, the first battery cell 1 is charged with a constant current of a second preset rate for a second preset charging time. Finally, after a third preset standing time, the formation of the first battery cell 1 is completed, and a SEI film with gradient pores is formed on the surface of the first negative electrode 11. The dense inner layer is combined with the loose outer layer SEI film to improve the lithium ion transmission rate, and prevent the dense SEI film formed by long-term small current formation from being too thick, thereby hindering the transmission of lithium ions during the charge and discharge process.

[0113] The second positive electrode 22 and the second negative electrode 21 are connected for formation, and after a first preset standing time, the second battery cell 2 is charged with a constant current of a first preset rate for a first preset charging time. Thereafter, after a second preset standing time, the second battery cell 2 is charged with a constant current of a second preset rate for a second preset charging time. Finally, after a third preset standing time, the formation of the second battery cell 2 is completed, and a SEI film with gradient pores is formed on the surface of the second negative electrode 21. The dense inner layer is combined with the loose outer layer SEI film to improve the lithium ion transmission rate, and prevent the dense SEI film formed by long-term small current formation from being too thick, thereby hindering the transmission of lithium ions during the charge and discharge process.

[0114] It should be noted that the first preset standing time, the second preset standing time and the third preset standing time can be set according to actual needs, without limitation. For example, the first preset standing time, the second preset standing time and the third preset standing time can all be 10 minutes.

[0115] The first preset magnification and the second preset magnification can be set according to actual needs, and there is no limitation on this. For example, the first preset magnification range may be 0.02C-0.05C, and the second preset magnification range may be 0.1C-0.2C.

[0116] The first preset charging time and the second preset charging time can be set according to actual needs, and there is no limitation on this. For example, the first preset charging time range may be 20min-30min, and the second preset charging time range may be 30min-60min.

[0117] In some embodiments, the preparation method further comprises:

[0118] Connecting the first positive electrode 12 and the first negative electrode 11 to divide the capacity, so as to obtain the actual capacity value of the first battery cell 1;

[0119] The second positive electrode 22 and the second negative electrode 21 are connected to divide the capacity to obtain the actual capacity value of the second battery cell 2 .

[0120] The capacity division of the first battery cell 1 includes:

[0121] After a fourth preset rest time, the battery is charged to a first preset voltage with a constant current and constant voltage at a third preset rate, and the cut-off current is a preset current;

[0122] After a fifth preset rest time, discharging at a fourth preset rate constant current to a second preset voltage;

[0123] Wait for the sixth preset rest time;

[0124] The above steps are repeated for a preset number of times, and the capacity of the last cycle is taken as the actual capacity value of the first battery cell 1 .

[0125] The capacity division of the second battery cell 2 includes:

[0126] After a fourth preset rest time, the battery is charged to a third preset voltage with a current constant current and constant voltage of a third preset rate, and the cut-off current is a preset current;

[0127] After a fifth preset rest time, discharging at a fourth preset rate constant current to a second preset voltage;

[0128] Waiting for a sixth preset rest time; repeating the above steps according to a preset number of times, and taking the capacity of the last cycle as the actual capacity value of the second battery cell;

[0129] Charging with a constant current of a fifth preset rate for a third preset charging time;

[0130] Wait for the seventh preset rest time.

[0131] It can be understood that the first positive electrode 12 and the first negative electrode 11 are connected, and after the fourth preset rest time, the first battery cell 1 is charged to the first preset voltage with a current of the third preset rate at a constant current and constant voltage, and the cut-off current is the preset current, and then, after the fifth preset rest time, the first battery cell 1 is discharged to the second preset voltage with a current of the fourth preset rate at a constant current, and finally, the sixth preset rest time is waited. Thus, the above steps are repeated according to the preset number of times, so as to obtain the actual capacity value of the first battery cell 1, and the capacity division of the first battery cell 1 is completed.

[0132] The second positive electrode 22 and the second negative electrode 21 are connected, and after the fourth preset standing time, the second battery cell 2 is charged with a constant current and constant voltage at a third preset rate to a third preset voltage, and the cut-off current is the preset current. Thereafter, after the fifth preset standing time, the second battery cell 2 is discharged with a constant current at a fourth preset rate to a second preset voltage, and then, the sixth preset standing time is waited. Thus, the above steps are repeated according to the preset number of times to obtain the actual capacity value C0 of the second battery cell 2, and the capacity division of the second battery cell 2 is completed. Finally, the battery is charged with a constant current at a fifth preset rate for a third preset charging time, and after waiting for the seventh preset standing time, the battery has a certain charge, so as to facilitate the subsequent lithium plating.

[0133] It should be noted that the fourth preset standing time, the fifth preset standing time, the sixth preset standing time and the seventh preset standing time can be set according to actual needs, without limitation. For example, the fourth preset standing time, the fifth preset standing time, the sixth preset standing time and the seventh preset standing time can all be 10 minutes.

[0134] The third preset magnification, the fourth preset magnification and the fifth preset magnification can be set according to actual needs without limitation. For example, the third preset magnification and the fourth preset magnification can both range from 0.1C to 0.5C, the fifth preset magnification can range from 0.1C0 to 0.3C0, and the preset current magnification of the cut-off current can be 0.05C.

[0135] The first preset voltage, the second preset voltage and the third preset voltage can be set according to actual needs without limitation. For example, the first preset voltage can be 3.65V, the second preset voltage can be 2.5V, and the third preset voltage can be 4.2V.

[0136] The third preset charging time can be set according to actual needs, and there is no limitation on this. For example, the third preset charging time range can be 60min-90min.

[0137] The preset number of times can be set according to actual needs and is not limited thereto. For example, the above steps are repeated for 3 weeks.

[0138] During the charging experiment, the positive electrode of the charging device is connected to the first positive electrode 12, and the negative electrode of the charging device is connected to the first negative electrode 11. The reference electrode potential recording device selects two test channels to record the potential changes of the positive and negative electrodes during the charging process respectively. Channel one records the potential changes of the positive electrode, the positive electrode terminal is connected to the first positive electrode 12, and the negative electrode terminal is connected to the first reference electrode; Channel two records the potential changes of the negative electrode, the positive electrode terminal is connected to the first reference electrode, and the negative electrode terminal is connected to the first negative electrode 11.

[0139] After potential calibration, the potential V1 of the first reference electrode can be obtained. During the charge and discharge test, the recording device records the potential difference V2 between the reference electrode and the negative electrode. Since the potential value of the reference electrode remains unchanged, when the negative electrode drops to 0V or even below due to polarization, the V2 value of the recording device is equal to or greater than V1. Therefore, when the calibration value is used as a reference line, when the potential value is above the reference line, it can be considered that the charge lithium deposition risk zone has been entered. The test is as follows: Figure 5 As shown, this method can realize the rapid identification of lithium plating risk during the charging process. Through charging tests, it is found that there is a greater risk of lithium plating under high SOC.

[0140] It should be noted that, in the description of the present disclosure, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, the meaning of "plurality" is two or more.

[0141] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0142] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0143] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A dual-cell lithium-ion battery, characterized in that: include: A first battery cell, the first battery cell comprising: a plurality of first negative electrodes distributed at intervals and a first positive electrode stacked between adjacent first negative electrodes; A second battery cell, wherein the second battery cell and the first battery cell are stacked, and the second battery cell comprises: a plurality of second negative electrodes distributed at intervals and a second positive electrode stacked between adjacent second negative electrodes; The second positive electrode is used as the first reference electrode, and a positive electrode active material having a characteristic voltage platform is used.

2. The dual-cell lithium-ion battery according to claim 1, characterized in that: The positive electrode active material of the second positive electrode is lithium iron phosphate material; and / or, The positive electrode active material of the second positive electrode is lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, or the iron content in the lithium iron manganese phosphate material is greater than the manganese content.

3. The dual-cell lithium-ion battery according to claim 1, characterized in that: The lithium-ion battery also includes: A copper wire, wherein the copper wire is arranged between the second negative electrode and the second positive electrode in the second battery cell which are farthest from the first battery cell, and the copper wire is provided with a lithium-plated layer using the second positive electrode and the second negative electrode as lithium sources, and the copper wire serves as a second reference electrode and is used for calibrating the potential of the first reference electrode.

4. The dual-cell lithium-ion battery according to claim 3, characterized in that: The lithium-ion battery also includes: A plurality of first separators, wherein the plurality of first separators are respectively arranged between the adjacent first negative electrode and the first positive electrode, between the adjacent first negative electrode and the second negative electrode, and between the adjacent second negative electrode and the second positive electrode, wherein the copper wire is located between the second negative electrode farthest from the first battery cell in the second battery cell and the first separator; A second separator is provided between the adjacent second negative electrode and the copper wire.

5. The dual-cell lithium-ion battery according to claim 3, characterized in that: The copper wire is arranged along the width direction of the lithium ion battery, and the length of the copper wire in the thickness direction of the lithium ion battery and the overlapping part of the second positive electrode ranges from 1 / 2 to 3 / 4 of the width of the second positive electrode.

6. The dual-cell lithium-ion battery according to claim 3, characterized in that: The first negative electrode is provided with a first pole lug, and the first positive electrode is provided with a second pole lug; The second negative electrode is provided with a third pole lug, and the second positive electrode is provided with a fourth pole lug; The copper wire is provided with a fifth pole lug; The first pole tab and the second pole tab are respectively arranged at the top of the lithium-ion battery, the third pole tab and the fourth pole tab are respectively arranged at the bottom of the lithium-ion battery, and the fifth pole tab is arranged on the side of the lithium-ion battery between the top and the bottom.

7. A method for preparing a dual-cell lithium-ion battery, characterized in that: The preparation method comprises: Distribute a plurality of first negative electrodes at intervals, and stack first positive electrodes between adjacent first negative electrodes to form a first battery cell; Distributing a plurality of second negative electrodes at intervals, and stacking second positive electrodes between adjacent second negative electrodes to form a second battery cell, wherein the second positive electrode serves as a first reference electrode and uses a positive electrode active material with a characteristic voltage platform; Laying the first battery cell and the second battery cell in layers and packaging them to obtain a semi-finished product; The semi-finished product is sequentially subjected to baking, liquid injection, formation and capacity separation to obtain the lithium-ion battery.

8. The method for preparing a dual-cell lithium-ion battery according to claim 7, characterized in that: The preparation method further comprises: When the positive electrode active material of the second positive electrode is lithium iron phosphate material, the potential of the first reference electrode is adjusted to a first voltage platform corresponding to the lithium iron phosphate material; When the positive electrode active material of the second positive electrode is a lithium iron manganese phosphate material, and the manganese content in the lithium iron manganese phosphate material is greater than the iron content, the potential of the first reference electrode is adjusted to a second voltage platform corresponding to the lithium iron manganese phosphate material; When the positive electrode active material of the second positive electrode is lithium iron manganese phosphate material, and the iron content in the lithium iron manganese phosphate material is greater than the manganese content, the potential of the first reference electrode is adjusted to a third voltage platform corresponding to the lithium iron manganese phosphate material.

9. The method for preparing a dual-cell lithium-ion battery according to claim 7, characterized in that: The preparation method further comprises: placing a copper wire between the second negative electrode and the second positive electrode in the second battery cell which are farthest from the first battery cell, to serve as a second reference electrode; Connecting the first reference electrode to the positive electrode of the lithium plating device, and connecting the second reference electrode to the negative electrode of the lithium plating device, and performing forward lithium plating on the copper wire at a preset lithium plating current and a preset lithium plating time; Disconnect the connection between the first reference electrode and the positive electrode of the lithium plating equipment, connect the second negative electrode and the positive electrode of the lithium plating equipment, and reversely plate lithium on the copper wire with the preset lithium plating current and the preset lithium plating time to form a lithium plating layer on the copper wire with the second positive electrode and the second negative electrode as lithium sources.

10. The method for preparing a dual-cell lithium-ion battery according to claim 9, characterized in that: The preparation method further comprises: Connecting the first reference electrode to the positive electrode of the test device, and connecting the second reference electrode to the negative electrode of the test device; The potential difference between the first reference electrode and the second reference electrode is obtained according to the test device, and the potential difference is used as the lithium potential value of the first reference electrode.

11. The method for preparing a dual-cell lithium-ion battery according to claim 7, characterized in that: The preparation method further comprises: Connecting the first positive electrode and the first negative electrode for chemical formation to form a solid electrolyte interface film on the surface of the first negative electrode; Connecting the second positive electrode and the second negative electrode for chemical formation to form a solid electrolyte interface film on the surface of the second negative electrode; Wherein, the formation comprises: after a first preset rest time, charging with a current constant current of a first preset rate for a first preset charging time; after a second preset rest time, charging with a current constant current of a second preset rate for a second preset charging time; after a third preset rest time, completing the formation; The second preset rate is greater than the first preset rate, and the second preset charging time is greater than the first preset charging time.

12. The method for preparing a dual-cell lithium-ion battery according to claim 7, characterized in that: The preparation method further comprises: Connecting the first positive electrode and the first negative electrode to divide the capacity to obtain an actual capacity value of the first battery cell; Connecting the second positive electrode and the second negative electrode to divide the capacity to obtain an actual capacity value of the second battery cell; The capacity division of the first battery cell includes: after a fourth preset rest time, charging to a first preset voltage with a current constant current and constant voltage of a third preset rate, with a cut-off current being a preset current; after a fifth preset rest time, discharging to a second preset voltage with a current constant current of a fourth preset rate; waiting for a sixth preset rest time; repeating the above steps for a preset number of times, and taking the capacity of the last cycle as the actual capacity value of the first battery cell; The capacity division of the second battery cell includes: after a fourth preset standing time, charging with a third preset rate of constant current and constant voltage to a third preset voltage, with a cut-off current being a preset current; after a fifth preset standing time, discharging with a fourth preset rate of constant current to a second preset voltage; waiting for a sixth preset standing time; repeating the above steps according to a preset number of times, taking the capacity of the last cycle as the actual capacity value of the second battery cell; charging with a fifth preset rate of constant current for a third preset charging time; and waiting for a seventh preset standing time.

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