Lithium compensating agent for lithium secondary battery, preparation method thereof, lithium secondary battery, battery module, battery pack and device

Abstract

The present application discloses a lithium compensator for lithium secondary batteries, a preparation method thereof, and lithium secondary batteries, battery modules, battery packs, and devices. Experiments show that the lithium compensator of the present application can maintain its own stability and low metal dissolution during the long-term use of lithium secondary batteries, effectively improving the energy density of lithium secondary batteries, while also ensuring a low self-discharge rate of lithium secondary batteries, thereby ensuring that lithium secondary batteries have both high energy density, long cycle life, and high safety.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium secondary batteries, and relates to a lithium compensator for lithium secondary batteries, a preparation method thereof, and related electrical equipment, and in particular to a lithium compensator for lithium secondary batteries, a preparation method thereof, and a lithium secondary battery, a battery module, a battery pack, and a device comprising the lithium compensator. Background Art

[0002] Lithium secondary batteries have the advantages of high energy density, long cycle life and no memory effect, and are widely used in many consumer electronic products. In recent years, with the continuous development of electric vehicles and energy storage systems, the requirements for the energy density of lithium secondary batteries are also increasing.

[0003] Generally, the method of improving the energy density of lithium secondary batteries is mainly to improve it by adopting high gram capacity active materials, high active material filling rate, reducing active lithium consumption and other ways. However, the above improvement methods often have the problems of high cost, complex process, or poor processability, which is not conducive to large-scale commercial application and brings huge safety hazards to actual production. At the same time, it has a certain impact on the safety performance of lithium secondary batteries.

[0004] Therefore, developing a method that can effectively improve the energy density of lithium secondary batteries and ensure the good safety performance of lithium secondary batteries, while achieving high safety and low cost of the processing technology has become a technical problem that urgently needs to be solved for lithium secondary batteries. Summary of the invention

[0005] On the one hand, some embodiments of the present application provide a lithium compensator for a lithium secondary battery, wherein the lithium compensator contains a compound L, wherein the molecular formula of the compound L is Li x Ni a Cu 1-a-b M b O2, wherein 1≤x≤2, 0<a<1, 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn.

[0006] Among them, the XRD spectrum of the lithium compensator contains a first diffraction peak with a diffraction angle 2θ of 42° to 44° and a second diffraction peak with a diffraction angle 2θ of 25° to 27°, the diffraction intensity of the first diffraction peak is I1, the diffraction intensity of the second diffraction peak is I2, and satisfies: I1 / I2<0.1%.

[0007] The first diffraction peak corresponds to the diffraction peak of nickel oxide at the (200) crystal plane, and the second diffraction peak corresponds to the diffraction peak of the compound L at the (100) crystal plane.

[0008] Wherein, based on the total weight of the lithium compensator, the content of free lithium in the lithium compensator is ≤5wt%, optionally ≤3wt%, optionally ≤1wt%.

[0009] Wherein, the free lithium includes Li2CO3 and LiOH.

[0010] Wherein, the pH of the lithium compensator is recorded as pH L , and satisfy 11≤pH L ≤13; optional, 11.5≤pH L ≤12.5.

[0011] Wherein, the water content of the lithium compensator is not higher than 800 ppm. Optionally, the water content of the lithium compensator is not higher than 300 ppm.

[0012] Wherein, the volume average particle size D of the lithium compensator is v 50 is 2 μm to 10 μm, and optionally, the volume average particle size D of the lithium compensator is v 50 is 3μm~6μm.

[0013] Wherein, in the molecular formula of the compound L, 0.1≤a≤0.9; optionally, 0.2≤a≤0.6; further optionally, 0.2≤a≤0.4.

[0014] Wherein, the compound L is selected from Li2Ni 0.1 Cu 0.9 O2、Li2Ni 0.2 Cu 0.8 O2、Li2Ni 0.3 Cu 0.7 O2、Li2Ni 0.4 Cu 0.6 O2、Li2Ni 0.5 Cu 0.5 O2、Li2Ni 0.6 Cu 0.4 O2、Li2Ni 0.7 Cu 0.3 O2、Li2Ni 0.8 Cu 0.2 O2、Li2Ni 0.9 Cu 0.1 O2, or Li2Ni 0.4 Cu 0.55 Mg 0.05 O2.

[0015] Wherein, the lithium compensator also includes a coating layer located on at least a portion of the surface of the compound L, and the material of the coating layer is selected from one or more of metal fluorides, oxides, and phosphates; optionally, the metal fluoride is selected from AlF3; the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, and B2O3; the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, and Ni3(PO4)2.

[0016] In a second aspect, some embodiments of the present application also provide a method for preparing the above-mentioned lithium compensating agent for lithium secondary batteries, comprising the following steps:

[0017] S1: weighing a lithium source, a nickel source, a copper source and an M source, mixing and then ball milling, wherein the molar stoichiometric ratio of Li, Ni, Cu and M elements is c:a:(1-ab):b, and 2≤c≤3, 0<a<1, 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn; and

[0018] S2: Sintering the ball-milled mixture to obtain the lithium compensator.

[0019] Among them, in S1, 2.1≤c≤2.7, 0.1≤a≤0.9; optionally, 2.2≤c≤2.6, 0.2≤a≤0.6; further optionally, 0.2≤a≤0.4.

[0020] Wherein, in S2, the sintering process satisfies at least one of the following conditions:

[0021] (1) The heating rate is 1°C / min to 10°C / min; optionally, the heating rate is 3°C / min to 5°C / min;

[0022] (2) The sintering temperature is 600° C. to 800° C.; optionally, the sintering temperature is 650° C. to 750° C.;

[0023] (3) The insulation time is 5 h to 20 h; optionally, the insulation time is 6 h to 10 h.

[0024] Optionally, the method further comprises the following steps:

[0025] S3: The sintered product obtained in S2 is crushed and classified to obtain an average particle size D v 50 is a classified product of 2 μm to 10 μm, and optionally, the volume average particle size D of the classified product v 50 is 3μm~6μm.

[0026] Optionally, the method further comprises the following steps:

[0027] S4: washing the product after classification in S3 with anhydrous ethanol or isopropanol, the washing time is 0 to 2 hours, and optionally 0.2 hours to 1.5 hours; and

[0028] S5: drying or infrared heating the washed product under vacuum or inert atmosphere, optionally, the inert atmosphere includes nitrogen or argon, the drying or infrared heating temperature is 100°C to 200°C, and the drying or infrared heating time is 2h to 12h.

[0029] Optionally, the method further comprises the following steps:

[0030] S6: ball-milling and coating the lithium compensator with a coating material, wherein the coating material is selected from one or more of metal fluorides, oxides, and phosphates.

[0031] Among them, the metal fluoride is selected from AlF3; the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, B2O3; the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, Ni3(PO4)2.

[0032] Wherein, during the preparation process, the ambient humidity is not higher than 45%; optionally, the ambient humidity is not higher than 30%; further optionally, the ambient humidity is not higher than 10%.

[0033] Wherein, the lithium source is selected from one or more of Li2O, Li2CO3, Li2C2O4, CH3COOLi, LiOH·H2O, and LiOH; the nickel source is selected from one or more of Ni2CO3, Ni(OH)2, NiO, NiSO4, Ni(CH3COO)2, and NiC2O4; the copper source is selected from one or more of Cu2(OH)2CO3, Cu(OH)2, CuO, CuSO4, CuC2O4, and Cu(CH3COO)2; the M source is selected from one or more of ZnO, SnO, MgO, FeO, MnO, ZnF2, SnF2, MgF2, FeF2, and MnF2.

[0034] In a third aspect, some embodiments of the present application further provide a lithium secondary battery, wherein the lithium secondary battery contains a lithium compensator, and the lithium compensator is the lithium compensator described above.

[0035] Optionally, the positive electrode of the lithium secondary battery contains a lithium compensator, and based on the total mass of the positive electrode active material, the mass proportion of the lithium compensator is 0.1wt% to 10wt%. Further optionally, the mass proportion of the lithium compensator is 2wt% to 8wt%.

[0036] Wherein, the positive electrode active material includes at least one of the compounds represented by formula (I) to formula (III):

[0037] Li 1+x1 Ni a1 Co b1 M' 1-a1-b1 O 2-y1 A y1 (I);

[0038] Li 1+x2 Mn a2 M” 2-a2 O 4-d A' d (II);

[0039] LiFe (1-x3-y3) Mn x3 M"' y3 PO4 (III).

[0040] Wherein, in the formula (I), -0.1≤x1≤0.2, 0<a1<1, 0≤b1≤1, 0<a1+b1<1, 0≤y1<0.2, M' is one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, and A includes one or more of S, N, F, Cl, Br and I; optionally, 0.5≤a1<1, 0<b1<0.5, 0.7≤a1+b1<1, 0≤y<0.1, M is one or both of Mn and Al, and A is one or both of S or F.

[0041] Wherein, in the formula (II), -0.1≤x2≤0.2, 0<a2≤2, 0≤d<1, M" includes one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, and A' includes one or more of S, N, F, Cl, Br and I.

[0042] Wherein, in the formula (III), 0≤x3≤1, 0≤y3≤0.1, and M″′ is selected from one or more transition metal elements and non-transition metal elements except Fe and Mn.

[0043] Optionally, the positive electrode active material includes at least the compound represented by formula (III).

[0044] Optionally, when the positive electrode active material contains a compound represented by formula (I), the pH of the compound represented by formula (I) is recorded as pH c The pH of the lithium compensator is denoted as pH L , and satisfies: pH c ≤pH L .

[0045] Optional, pH L ≤1.5×pH c ; Optional, pH L ≤1.1×pH c .

[0046] In a fourth aspect, some embodiments of the present application further provide a battery module, comprising the lithium secondary battery as described above.

[0047] In a fifth aspect, some embodiments of the present application also provide a battery pack, comprising the lithium secondary battery described above in the present application, or the battery module described above in the present application.

[0048] In a sixth aspect, some embodiments of the present application also provide a device, comprising a lithium secondary battery as described above, or a battery module as described above, or a battery pack as described above; wherein the lithium secondary battery, the battery module, or the battery pack can be used as a power source for the device or an energy storage unit for the device.

[0049] When the lithium compensator of the present application is used in a lithium secondary battery, its processing technology is simple and the requirements for process environment conditions are low. Moreover, during the long-term use of the lithium secondary battery, the lithium compensator can maintain its own stability and low metal dissolution, effectively improving the energy density of the lithium secondary battery, while also ensuring a low self-discharge rate of the lithium secondary battery, thereby ensuring that the lithium secondary battery has both high energy density, long cycle life and high safety.

[0050] The battery module, battery pack and device including the lithium compensator of the present application also have the same advantages as the lithium secondary battery containing the lithium compensator. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A three-dimensional view of a lithium secondary battery according to an embodiment of the present application is shown.

[0052] Figure 2 Shows Figure 1 An exploded view of a lithium secondary battery is shown.

[0053] Figure 3 A three-dimensional view of a battery module according to an embodiment of the present application is shown.

[0054] Figure 4 A three-dimensional view of a battery pack according to yet another embodiment of the present application is shown.

[0055] Figure 5 Shows Figure 4 Exploded view of the battery pack shown.

[0056] Figure 6A schematic diagram showing a lithium secondary battery as a power supply device according to an embodiment of the present application is shown.

[0057] Figure 7 The XRD pattern of the lithium compensating agent according to Example 1 of the present application is shown.

[0058] Figure 8 The particle size distribution diagram of the lithium compensating agent according to Example 1 of the present application is shown.

[0059] Fig. 9 A capacity variation curve of the lithium secondary battery during charge and discharge according to Example 1 of the present application is shown.

[0060] Among them, the reference numerals are: 1 battery pack, 2 upper box, 3 lower box, 4 battery module, 5 battery cell, 51 shell, 52 electrode assembly, 53 top cover assembly. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the present application clearer, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art should understand that these embodiments are only used to illustrate the technical solution of the present application and are not limiting.

[0062] The lithium compensating agent for a lithium secondary battery and a preparation method thereof according to the present application, as well as a lithium secondary battery, a battery module, a battery pack and a device including the lithium compensating agent will be described in detail below.

[0063] In order to improve the energy density of lithium secondary batteries, it is usually necessary to perform "pre-lithiation" on the negative electrode, positive electrode or separator to replenish the lithium ions consumed by the formation of the SEI film during the first charging process. It is known that setting metal lithium powder or lithium belt at the negative electrode of the lithium secondary battery is a relatively common method of lithium replenishment. Its advantage is that the specific capacity of metal lithium is high and the amount used is small. However, this method requires the use of special equipment and preparation technology, which has high cost, complex preparation process, harsh production environment, poor practicality, and is not conducive to large-scale commercial application. Most importantly, metal lithium powder or lithium belt, as an active metal, reacts violently with moisture in the air, which brings huge safety hazards to actual production.

[0064] In lithium secondary batteries, using lithium-rich metal oxides as lithium compensators is also a way to increase battery energy density. However, when using lithium-rich metal oxides, the capacity of the secondary battery in the long-term cycle process is not stable, and the improvement of the cycle life and energy density of the lithium secondary battery is limited, which greatly limits the application of lithium-rich metal oxides. Moreover, during the charge and discharge process of lithium secondary batteries containing lithium-rich metal oxides, the secondary battery is prone to self-discharge or internal short circuit problems. Therefore, how to improve the energy density of the secondary battery while ensuring that the battery has good electrochemical performance and high safety is a technical problem that needs to be solved urgently for current lithium secondary batteries.

[0065] Lithium compensator

[0066] According to the first aspect of the present application, the lithium compensator for lithium secondary battery contains a compound L, wherein the molecular formula of the compound L is Li x Ni a Cu 1-a-b M b O2, wherein 1≤x≤2, 0<a<1, 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn.

[0067] Among them, the XRD spectrum of the lithium compensator contains a first diffraction peak with a diffraction angle 2θ of 42° to 44° and a second diffraction peak with a diffraction angle 2θ of 25° to 27°, the diffraction intensity of the first diffraction peak is I1, the diffraction intensity of the second diffraction peak is I2, and satisfies: I1 / I2<0.1%.

[0068] The first diffraction peak corresponds to the diffraction peak of nickel oxide at the (200) crystal plane, and the second diffraction peak corresponds to the diffraction peak of the compound L at the (100) crystal plane.

[0069] As is well known in the art, generally, for perfectly crystallized nickel oxide, the strongest diffraction peak is the diffraction peak corresponding to the (200) crystal plane, and the diffraction peak is located at a diffraction angle 2θ of 43.2°. 0.5 Cu 0.5 O2, the strongest diffraction peak is the diffraction peak corresponding to the (100) crystal plane, and the above diffraction peak is located at a diffraction angle 2θ of 26.0°. x Ni a Cu 1-a-b M b O2), since the content of doping element M in compound L is small (0≤b<0.1), it has almost no significant effect on the crystal structure of compound L. Therefore, the peak position of XRD diffraction pattern of compound L is similar to that of pure LiNi 0.5 Cu 0.5The peak position of O2 is almost exactly the same. It should be pointed out that due to the size of the material grains and the error of the testing instrument, the peak position in its XRD spectrum will shift slightly, usually within ±1°.

[0070] In the present application, the test method of the XRD spectrum of the lithium compensator can be measured using instruments and methods known in the art. As an example, the following method can be used for testing: select an X-ray diffractometer of the model Bruker D8 Discover, use Cu as the target material, and perform XRD testing on the lithium compensator sample at a voltage of 40kV within a diffraction angle 2θ range of 15° to 75°. Among them, the preparation of the lithium compensator sample to be tested can be carried out by the following method: select 0.5g to 1g of lithium compensator for grinding, compact it on the surface of a glass slide, obtain the lithium compensator sample to be tested, and then perform the above test.

[0071] In the present application, the lithium compensator contains a molecular formula of Li x Ni a Cu 1-a-b M b O2 compound L, and when the ratio of the peak intensity of the first diffraction peak at a diffraction angle 2θ of 42° to 44° and the second diffraction peak at a diffraction angle 2θ of 25° to 27° in its XRD spectrum is I1 / I2<0.1%, the lithium compensator can exert a higher gram capacity and has good electrochemical stability. When the above lithium compensator is applied to a lithium secondary battery, on the one hand, it can effectively improve the energy density of the lithium secondary battery, and on the other hand, during the long-term charge and discharge process of the lithium secondary battery, it can effectively improve the self-discharge problem of the battery.

[0072] In one embodiment of the present application, I1 / I2 < 0.05%. Optionally, I1 / I2 < 0.01%. Further optionally, I1 / I2 < 0.005%. Specifically, the value of I1 / I2 can be 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, 0.005%, or its value is within the range obtained by combining any two of the above values.

[0073] In one embodiment of the present application, based on the total weight of the lithium compensator, the content of free lithium in the lithium compensator is ≤5wt%. Optionally, the content of free lithium in the lithium compensator is ≤1wt%. The free lithium (also known as "residual lithium") described herein refers to lithium-containing oxides, hydroxides and / or carbonates on the surface of compound L. In the present application, when there is free lithium in the lithium compensator, due to the presence of these small amounts of free lithium, the hydrofluoric acid produced by the decomposition of the electrolyte will be neutralized, weakening the corrosion effect on the positive electrode active material or lithium compensator in the battery; however, when the relative content of free lithium is too high, it will react with the electrolyte, which will reduce the cycle life of the secondary battery and increase the self-discharge rate of the secondary battery during storage. In one embodiment of the present application, for example, including but not limited to, the content of free lithium in the lithium compensator does not exceed 5wt%, 3wt%, 1wt%, 0.8wt%, 0.5wt% or 0.3wt% of the total weight of the lithium compensator, or its value is within the range obtained by combining any two of the above values.

[0074] In the present application, the test method for the free lithium content in the lithium compensator is well known in the art. As an example, the test can be performed by the following method: 30 g of lithium compensator is added to 100 mL of deionized water and stirred at a speed of 200 rpm for 30 min, and the free lithium in the sample to be tested is titrated with a standard hydrochloric acid solution, and a composite pH electrode is used as an indicator electrode to determine the titration end point by means of a sudden jump caused by a potential change.

[0075] In one embodiment of the present application, the free lithium includes Li2CO3 and LiOH.

[0076] In one embodiment of the present application, the pH of the lithium compensator is denoted as pH L , and satisfy 11≤pH L ≤13. Optional, 11.5≤pH L ≤12.5. In the present application, when the pH value of the lithium compensator is controlled within the above range, the proportion of active lithium in the lithium compensator can be effectively increased, and the chemical coagulation phenomenon of the positive electrode slurry during the processing can be effectively avoided, which is beneficial to manufacturing production. In a specific embodiment of the present application, the pH value of the lithium compensator is L For example, it can be 11, 11.5, 12, 12.5, etc., or all ranges and sub-ranges consisting of these values, including but not limited to 11-12.5, 11.5-12, etc.

[0077] In this application, the lithium compensator pH LThe test method is well known in the art. As an example, the following method can be used for testing: select a Mettler pH meter of model S220, take 5g of lithium compensator and add it to 45g of CO2-free water (mass ratio of powder to solvent = 1:9), then stir at a speed of 200 rpm for 30min, and let it stand for 1.5h. After the pH meter is calibrated, the solution containing the lithium compensator can be tested.

[0078] In one embodiment of the present application, the water content of the lithium compensator is ≤800ppm. In another embodiment of the present application, the water content of the lithium compensator is ≤300ppm. The water in the lithium compensator will react with the electrolyte to generate HF, which causes metal dissolution and also increases the self-discharge of the lithium secondary battery during use, causing the self-discharge rate of the lithium secondary battery to increase. In a specific embodiment of the present application, the water content of the lithium compensator can be, for example, 800ppm, 500ppm, 300ppm, 200ppm, 100ppm, etc., or all ranges and sub-ranges composed of these values. For example, including but not limited to, 100ppm~800ppm, 100ppm~500ppm, 100ppm~300ppm, 100ppm~200ppm, etc.

[0079] In the present application, the test method of the water content of the lithium compensator is well known in the art. As an example, the following method can be used for testing: a coulometric moisture meter of model 831 is selected, 10 g of lithium compensator is heated at 170° C. in an 874 fully automatic Karl Fischer sample heater, and a dry gas at a flow rate of 40 mL / min is purged into the titration cup to titrate the water content, and the titration time is 400 s.

[0080] In one embodiment of the present application, the volume average particle size D of the lithium compensator is v 50 is 2 μm to 10 μm. In another embodiment of the present application, the volume average particle size D of the lithium compensator is v 50 is 3μm to 6μm. The smaller the particle size of the lithium compensator, the higher the specific surface area, the greater the activity, and the larger the area in contact with the electrolyte, so that the capacity of the lithium secondary battery in the cycle is higher. However, if the particle size is too small, the powder is easy to agglomerate, affecting the gram capacity. In one embodiment of the present application, the volume average particle size D of the lithium compensator is v 50 may be, for example, 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, etc., or all ranges and sub-ranges consisting of these values, including but not limited to 1-10, 2-10, 1-8, 2-8, 1-6, 2-6, 1-5, 2-5, 5-8, 5-10, etc.

[0081] In this application, the volume average particle size D of the lithium compensator vThe test method of D 50 is well known in the art. As an example, the following method can be used for testing: referring to GB / T 19077-2016 particle size distribution laser diffraction method, a laser particle size analyzer (such as Mastersizer 2000E from Malvern, UK) is used for determination. v 50 represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%.

[0082] In one embodiment of the present application, the molecular formula of the compound L is 0<a<1. In another embodiment of the present application, the molecular formula of the compound L is 0.1≤a≤0.9. Optionally, 0.2≤a≤0.6, and further optionally, 0.2≤a≤0.4. In another embodiment of the present application, for the compound L, a is 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6.

[0083] In one embodiment of the present application, the molecular formula of the compound L is 0≤b<0.1. In another embodiment of the present application, the molecular formula of the compound L is 0≤b≤0.05. In another embodiment of the present application, for the compound L, b=0 or 0.05. In another embodiment of the present application, for the compound L, b=0.05.

[0084] In the present application, when the relative molar ratio a and (1-ab) of the Ni element to the Cu element in the compound L is within the above range, it is beneficial to synthesize the compound L with higher crystallinity at a lower temperature, effectively reducing the production cost; at the same time, it can also ensure that the lithium compensator containing it has a higher gram capacity and charge and discharge platform, which is beneficial to improve the energy density of the lithium secondary battery.

[0085] In one embodiment of the present application, for the compound L, M is selected from one or more of Zn, Sn, Mg, Fe and Mn. In another embodiment of the present application, for the compound L, M is selected from Mg. When the compound L is doped with the above M element, the sintering temperature of the compound L can be reduced and the crystallinity of the compound L can be improved.

[0086] In one embodiment of the present application, the molecular formula of the compound L is Li x Ni a Cu 1-a O2, wherein x and a are as described above.

[0087] In one embodiment of the present application, the compound L includes, but is not limited to, Li2Ni 0.1 Cu 0.9 O2、Li2Ni 0.2 Cu 0.8 O2、Li2Ni 0.3Cu 0.7 O2、Li2Ni 0.4 Cu 0.6 O2、Li2Ni 0.5 Cu 0.5 O2、Li2Ni 0.6 Cu 0.4 O2、Li2Ni 0.7 Cu 0.3 O2、Li2Ni 0.8 Cu 0.2 O2、Li2Ni 0.9 Cu 0.1 O2, or Li2Ni 0.4 Cu 0.55 Mg 0.05 O2.

[0088] In one embodiment of the present application, the lithium compensator further includes a coating located on at least a portion of the surface of the compound L, and the coating is selected from one or more of metal fluorides, oxides, and phosphates. Optionally, the metal fluoride is selected from AlF3; the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, and B2O3; the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, and Ni3(PO4)2.

[0089] In the present application, when the compound L is further coated with the above-mentioned substance, the water content and pH content on the surface of the lithium compensator can be further reduced, thereby improving the processability and electrochemical stability of the lithium compensator.

[0090] Preparation of lithium compensating agent

[0091] According to the second aspect of the present application, the method for preparing the lithium compensating agent for a lithium secondary battery comprises the following steps:

[0092] S1: weighing a lithium source, a nickel source, a copper source and an M source, mixing and then ball milling; wherein the molar stoichiometric ratio of Li, Ni, Cu and M elements is c:a:(1-ab):b, 2≤c≤3, 0<a<1, 0≤b<0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn; and

[0093] S2: Sintering the ball-milled mixture to obtain a lithium compensator.

[0094] Among them, in S1, 2.1≤c≤2.7, 0.1≤a≤0.9; optionally, 2.2≤c≤2.6, 0.2≤a≤0.6; further optionally, 0.2≤a≤0.4.

[0095] Wherein, in S2, the sintering process satisfies at least one of the following conditions:

[0096] (1) The heating rate is 1°C / min to 10°C / min. Optionally, the heating rate is 3°C / min to 5°C / min;

[0097] (2) The sintering temperature is 600°C to 800°C. Optionally, the sintering temperature is 650°C to 750°C;

[0098] (3) The heat preservation time is 5 hours to 20 hours. Optionally, the heat preservation time is 6 hours to 10 hours.

[0099] Optionally, the method further comprises S3: crushing and classifying the sintered product obtained in S2 to obtain an average particle size D v 50 is a classified product with a particle size of 2 μm to 10 μm. Optionally, the volume average particle size D v 50 is 3μm~6μm.

[0100] Optionally, the method further comprises S4: washing the product classified in S3 with anhydrous ethanol or isopropanol for 0 to 2 hours. Optionally, the washing time is 0.2 hours to 1.5 hours.

[0101] Optionally, the method further comprises S5: drying or infrared heating the washed product under vacuum or inert atmosphere. Optionally, the inert atmosphere comprises nitrogen or argon, the drying or infrared heating temperature is 100° C. to 200° C., and the drying or infrared heating time is 2 h to 12 h.

[0102] Optionally, the method further comprises S6: ball-milling and coating the target lithium compensator with a coating material, wherein the coating material is selected from one or more of metal fluorides, oxides, and phosphates.

[0103] In a specific embodiment of the present application, the metal fluoride is selected from AlF3.

[0104] In a specific embodiment of the present application, the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, and B2O3.

[0105] In a specific embodiment of the present application, the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, and Ni3(PO4)2.

[0106] In a specific embodiment of the present application, the lithium source is selected from one or more of Li2O, Li2CO3, Li2C2O4, CH3COOLi, LiOH·H2O, and LiOH.

[0107] In a specific embodiment of the present application, the nickel source is selected from one or more of Ni2CO3, Ni(OH)2, NiO, NiSO4, Ni(CH3COO)2, and NiC2O4.

[0108] In a specific embodiment of the present application, the copper source is selected from one or more of Cu2(OH)2CO3, Cu(OH)2, CuO, CuSO4, CuC2O4, and Cu(CH3COO)2.

[0109] In a specific embodiment of the present application, the M source is selected from one or more of ZnO, SnO, MgO, FeO, MnO, ZnF2, SnF2, MgF2, FeF2, and MnF2.

[0110] Optionally, during the above preparation process, the ambient humidity is not higher than 45%. Optionally, the ambient humidity is not higher than 30%. Further, optionally, the ambient humidity is not higher than 10%.

[0111] Lithium secondary battery

[0112] According to the third aspect of the present application, the lithium secondary battery contains the lithium compensator as described above. Optionally, the lithium compensator is contained in the positive electrode of the lithium secondary battery, and the mass proportion of the lithium compensator is 0.1wt% to 10wt% based on the total mass of the positive electrode active material; further optionally, the mass proportion of the lithium compensator is 2wt% to 8wt%.

[0113] Figure 1 shows a three-dimensional view of a lithium secondary battery according to an embodiment of the present application, Figure 2 yes Figure 1 An exploded view of a lithium secondary battery is shown. Figure 1 and Figure 2 According to the present application, the lithium secondary battery 5 (hereinafter referred to as the battery cell 5) includes a housing 51, an electrode assembly 52, and a top cover assembly 53. The electrode assembly 52 is accommodated in the housing 51, and the number of the electrode assembly 52 is not limited, and can be one or more.

[0114] It should be noted that Figure 1 The battery cell 5 shown is a can-type battery, but the present application is not limited thereto. The battery cell 5 may be a pouch-type battery, that is, the housing 51 is replaced by a metal plastic film and the top cover assembly 53 is eliminated.

[0115] In one embodiment of the present application, the positive electrode comprises a positive electrode active material capable of releasing and accepting lithium ions and the lithium compensator described above. The positive electrode active material comprises at least one of the compounds represented by formula (I) to formula (III):

[0116] Li1+x1 Ni a1 Co b1 M' 1-a1-b1 O 2-y1 A y1 (I);

[0117] Li 1+x2 Mn a2 M” 2-a2 O 4-d A' d (II);

[0118] LiFe (1-x3-y3) Mn x3 M"' y3 PO4 (III);

[0119] Wherein, in the above formula (I), -0.1≤x1≤0.2, 0<a1<1, 0≤b1≤1, 0<a1+b1<1, 0≤y1<0.2, M' is one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, and A includes one or more of S, N, F, Cl, Br and I; optionally, 0.5≤a1<1, 0<b1<0.5, 0.7≤a1+b1<1, 0≤y<0.1, M is one or both of Mn and Al, and A is one or both of S or F.

[0120] In the above formula (II), -0.1≤x2≤0.2, 0<a2≤2, 0≤d<1, M" includes one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, and A' includes one or more of S, N, F, Cl, Br and I.

[0121] In formula (III), 0≤x3≤1, 0≤y3≤0.1, and M″′ is selected from one or more transition metal elements other than Fe and Mn and non-transition metal elements.

[0122] Optionally, the positive electrode active material includes at least the compound represented by formula (III).

[0123] In one embodiment of the present application, the positive electrode active material is selected from LiFePO4, Li3V2(PO4)3, LiFe y Mn 1- y PO4、LiNi 0.8 Co 0.15 Al 0.05 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Co0.2 Mn 0.3 O2, LiMnO2, LiMn2O4, LiCoO2, LiMnPO4, LiNiO2, wherein 0<y<1. In one specific embodiment of the present application, the positive electrode active material is LiFePO4. In another specific embodiment of the present application, the positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2 (i.e. NCM811).

[0124] In one embodiment of the present application, when the positive electrode active material contains the compound represented by formula (I), the pH of the compound represented by formula (I) is recorded as pH. The pH of the lithium compensator is recorded as pH L , and satisfies: pH c ≤pH L . Optional, pH L ≤1.5×pH c . Optionally, pH L ≤1.1×pH c When the pH of the ternary positive electrode active material and the lithium compensator satisfies the above relationship, the lithium compensator and the ternary positive electrode active material can stably coexist in the positive electrode slurry, which improves the processability of the lithium compensator in the lithium secondary battery and the uniformity of the distribution of the components in the positive electrode sheet. Therefore, it is conducive to large-scale mass production. At the same time, the battery has the advantages of high energy density and low self-discharge rate.

[0125] In this application, the pH of the ternary positive electrode active material c The test method is well known in the art. As an example, the pH value of the lithium compensator can be used. L The same test method was used for determination.

[0126] In this article, there is no specific limitation on the conductive agent used for the positive electrode, and it can be appropriately selected according to actual needs, such as the conductive agent commonly used for the positive electrode in the art, as long as the technical solution of the present application can be achieved. In one embodiment of the present application, the conductive agent is carbon black.

[0127] In this article, there is no specific limitation on the binder used for the positive electrode, and it can be appropriately selected according to actual needs, such as the binder commonly used for the positive electrode in the art, as long as the technical solution of the present application can be achieved. In one embodiment of the present application, the binder is one or more of polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na).

[0128] In this article, there is no specific limitation on the negative electrode used for the lithium secondary battery, and it can be appropriately selected according to actual needs. It can be those negative electrodes commonly used in lithium secondary batteries, as long as the technical solution of the present application can be realized. As an example, in one embodiment of the present application, the negative electrode contains a negative electrode active material that can accept and release lithium ions. The negative electrode active material is selected from soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide compounds, silicon carbon composites, lithium titanate, metals that can form alloys with lithium, etc. Optionally, the negative electrode active material can be selected from negative electrode active materials with high gram capacity such as silicon, silicon oxide compounds, silicon carbon composites, etc.

[0129] In this article, the material of the separator used for the lithium secondary battery is not limited and can be selected according to actual needs. In one embodiment of the present application, the separator is a polyethylene film (PE). In another embodiment of the present application, the separator is a 12 μm polyethylene film (PE).

[0130] In specific applications, the positive electrode is usually further processed into a positive electrode sheet, and the structure and preparation method of the positive electrode sheet are known in the art. For example, the positive electrode active material, conductive agent, binder, lithium compensating agent, etc. are mixed evenly in an organic solvent, applied on a positive electrode collector (such as Al foil), dried, and cold pressed to obtain a positive electrode sheet.

[0131] Similarly, in specific applications, the negative electrode is usually further processed into a negative electrode sheet, and the structure and preparation method of the negative electrode sheet are known in the art. For example, the negative electrode active material, conductive agent, binder, thickener, etc. are mixed evenly in a solvent, applied to a negative electrode collector (such as Cu foil), dried, and cold pressed to obtain a negative electrode sheet.

[0132] The negative electrode active material, conductive agent, binder, thickener, solvent, etc. used for the negative electrode are all conventional reagents used for lithium secondary batteries and will not be described in detail here.

[0133] In this article, there is no specific limitation on the electrolyte used for lithium secondary batteries, and it can be appropriately selected according to actual needs, such as the electrolyte commonly used in lithium secondary batteries in the art, as long as the technical solution of the present application can be realized. In one embodiment of the present application, the electrolyte can be one of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) or any combination thereof, for example, the two can be mixed in any ratio such as 1:9, 2:8, 3:7, 4:6, etc. by mass ratio.

[0134] Battery Module

[0135] A battery module according to a fourth aspect of the present application includes the lithium secondary battery described above in the present application.

[0136] Figure 3 FIG. 2 shows a perspective view of a battery module according to an embodiment of the present application. Figure 3 The battery module of the present application may be a battery module 4, which includes a plurality of battery cells 5, and the plurality of battery cells 5 are arranged in a longitudinal direction.

[0137] The battery module 4 can be used as a power source or an energy storage device. The number of battery cells 5 in the battery module 4 can be adjusted according to the application and capacity of the battery module 4.

[0138] Battery Pack

[0139] The battery pack according to the fifth aspect of the present application includes the lithium secondary battery described above in the present application, or the battery module described above in the present application.

[0140] Figure 4 shows a three-dimensional view of a battery pack according to another embodiment of the present application, Figure 5 yes Figure 4 Exploded view of the battery pack shown. Figure 4 and Figure 5 The battery pack 1 of the present application includes an upper box body 2, a lower box body 3 and a battery module 4. The upper box body 2 and the lower box body 3 are assembled together to form a space for accommodating the battery module 4. The battery module 4 is placed in the space of the upper box body 2 and the lower box body 3 assembled together.

[0141] The output pole of the battery module 4 passes through one or both of the upper box body 2 and the lower box body 3 to supply power to the outside or charge from the outside.

[0142] It should be noted that the number and arrangement of the battery modules 4 used in the battery pack 1 can be determined according to actual needs. The battery pack 1 can be used as a power source or an energy storage device.

[0143] Device

[0144] The device according to the sixth aspect of the present application comprises the lithium secondary battery described above in the present application, or the battery module described above in the present application, or the battery pack described above in the present application. The lithium secondary battery, the battery module, or the battery pack can be used as a power source for the device described in the present application or an energy storage unit for the device.

[0145] Figure 6 FIG. 1 shows a schematic diagram of a lithium secondary battery as a power supply device according to an embodiment of the present application. Figure 6In the embodiment, the device using the battery cell 5 is an electric vehicle. Of course, the device using the battery cell 5 is not limited thereto, and can be any electric vehicle other than an electric vehicle (e.g., an electric bus, an electric tram, an electric bicycle, an electric motorcycle, an electric scooter, an electric golf cart, an electric truck), an electric ship, an electric tool, a consumer electronic product, and an energy storage system.

[0146] The electric vehicle may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Of course, depending on the actual use form, the device provided in the sixth aspect of the present application may include the battery module described in the fourth aspect of the present application or the battery pack described in the fifth aspect of the present application.

[0147] Example

[0148] The technical solution of the present application will be further explained below in conjunction with specific embodiments. Obviously, the exemplary embodiments below are only used for illustration and cannot constitute a limitation on the technical solution of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present application.

[0149] Example 1

[0150] 1. Prepare the lithium compensator according to the following steps:

[0151] S1: Weigh Li2O, NiO and CuO powders, wherein the molar ratio of Li, Ni and Cu elements is 2.05:0.4:0.6, and mix them evenly by ball milling;

[0152] S2: Then, the temperature was raised to 680°C at a heating rate of 3°C / min under a nitrogen atmosphere, and the temperature was naturally lowered after being kept for 10 hours;

[0153] S3: crush and classify the product to obtain D v 50 Fractionation product of about 5 μm;

[0154] S4: Wash with anhydrous ethanol for 0.5 h, and finally bake in a forced air oven at 160° C. for 12 h to obtain a lithium compensator, the composition and parameters of which are shown in Table 1 below.

[0155] 2. Preparation of positive electrode

[0156] The carbon-coated positive electrode active material LiFePO4 (LFP), the lithium compensator prepared above, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are uniformly mixed in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 94:2:3:1, wherein the pH value of the carbon-coated positive electrode active material LiFePO4 (LFP) is 8.9, to obtain a positive electrode slurry, and the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through drying, cold pressing, slitting, cutting and other processes.

[0157] 3. Preparation of negative electrode sheet

[0158] The negative electrode active material graphite, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed uniformly in a proper amount of solvent deionized water at a mass ratio of 96:1.5:1.5:1.0 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through drying, cold pressing, slitting, cutting and other processes.

[0159] 4. Isolation film

[0160] The isolation membrane is made of polyethylene (PE) film.

[0161] 5. Preparation of Electrolyte

[0162] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 30:70 to obtain an organic solvent, fully dried electrolyte salt LiPF6 is dissolved in the mixed solvent, the concentration of the electrolyte salt is 1.3 mol / L, and then 6% fluoroethylene carbonate (FEC) is added as an additive, and the electrolyte is obtained after mixing evenly. The concentration of the electrolyte salt is the concentration calculated based on the total volume of the electrolyte, and the content of the additive is the weight percentage calculated based on the total weight of the electrolyte.

[0163] 6. Preparation of lithium secondary batteries

[0164] The positive electrode sheet, separator and negative electrode sheet prepared above are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium secondary battery. After vacuum packaging, standing, formation, shaping and other processes, a lithium secondary battery is obtained.

[0165] Example 2

[0166] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that the synthesis temperature in the preparation step S2 of the lithium compensator of this embodiment is 670° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0167] Example 3

[0168] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that the synthesis temperature in the preparation step S2 of the lithium compensator of this embodiment is 660° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0169] Example 4

[0170] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that the synthesis temperature in the preparation step S2 of the lithium compensator of this embodiment is 640° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0171] Example 5

[0172] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that magnesium oxide is further added in the preparation step S1 of the lithium compensator of this embodiment, wherein the molar ratio of Li, Ni, Cu, and Mg is 2.05:0.4:0.55:0.05; and the synthesis temperature in step S2 is 670° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0173] Example 6

[0174] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that the positive electrode active material in the positive electrode sheet of this embodiment is LiNi 0.5 Co 0.2 Mn 0.3 O2. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0175] Example 7

[0176] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.05:0.1:0.9. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0177] Example 8

[0178] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.05:0.2:0.8. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0179] Example 9

[0180] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.05:0.6:0.4. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0181] Example 10

[0182] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.05:0.9:0.1. The composition and parameters of the lithium compensator are shown in Table 1 below.

[0183] Comparative Example 1

[0184] The lithium secondary battery of Comparative Example 1 (corresponding to D1 in Table 1) was prepared according to the method of Example 1, except that no lithium compensating agent was added to the positive electrode sheet of this comparative example.

[0185] Comparative Example 2

[0186] The lithium secondary battery of Comparative Example 2 (corresponding to D2 in Table 1) was prepared according to the method of Example 6, except that no lithium compensating agent was added to the positive electrode sheet of this comparative example.

[0187] Comparative Example 3

[0188] The lithium secondary battery of Comparative Example 3 (corresponding to D3 in Table 1) was prepared according to the method of Example 1, except that the synthesis temperature in the preparation step S2 of the lithium compensator of this comparative example was 820° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0189] Comparative Example 4

[0190] The lithium secondary battery of Comparative Example 4 (corresponding to D4 in Table 1) was prepared according to the method of Example 6, except that the synthesis temperature in the preparation step S2 of the lithium compensator in this comparative example was 850° C. The composition and parameters of the prepared lithium compensator are shown in Table 1 below.

[0191] Parameter characterization of positive electrode active materials and lithium compensators

[0192] 1.XRD analysis

[0193] A Bruker D8 Discover X-ray diffractometer was used, and Cu was used as the target material. At a voltage of 40 kV, the lithium compensator sample was subjected to XRD analysis within a diffraction angle 2θ range of 15° to 75°. The lithium compensator sample was prepared by the following method: 0.5 g of the lithium compensator prepared in each of the above embodiments and comparative examples was selected for grinding, compacted on the surface of a glass slide, to obtain a lithium compensator sample, and then subjected to XRD analysis.

[0194] Figure 7 The XRD spectrum of the lithium compensator according to Example 1 of the present application is shown. The XRD spectrum of the lithium compensator of other embodiments of the present application is basically the same as that of the lithium compensator, and is not provided herein. Figure 7 It can be seen that there is a first diffraction peak (diffraction intensity is I1) at a 2θ angle of 43.2° in the XRD spectrum, which corresponds to the diffraction peak of perfectly crystallized nickel oxide on the (200) crystal plane; there is a second diffraction peak (diffraction intensity is I2) at a 2θ angle of 26.0° in the XRD spectrum, which corresponds to the diffraction peak of compound L on the (100) crystal plane, I1 / I2=0.01%.

[0195] 2. Measurement of free lithium content in lithium compensator

[0196] Take 30g of the lithium compensating agent prepared in each of the above embodiments and add it to 100mL of deionized water and stir it at a speed of 200 rpm for 30min. Titrate the free lithium in the sample to be tested with a standard hydrochloric acid solution, use a composite pH electrode as an indicator electrode, determine the titration end point by the jump caused by the potential change, and then calculate the free lithium content.

[0197] 3. Measurement of pH value of lithium compensator and positive electrode active material

[0198] A Mettler acidometer model S220 was used, 5 g of the sample to be tested was added to 45 g of CO2-free water (mass ratio of powder to solvent = 1:9), then stirred at 200 rpm for 30 min and allowed to stand for 1.5 h. The pH value of the sample solution to be tested was measured after the pH meter was calibrated.

[0199] 4. Measurement of water content of lithium compensator

[0200] A Coulometric titrator of model 831 was selected, 10 g of lithium compensator was heated at 170°C in a fully automatic Karl Fischer sample heater of model 874, and dry gas was purged into the titration cup at a flow rate of 40 mL / min to titrate the water content. The titration time was 400 s.

[0201] 5. Volume average particle size D of lithium compensator v 50 Measurements

[0202] The particle size distribution laser diffraction method according to GB / T 19077-2016 is measured using a laser particle size analyzer (e.g., Mastersizer 2000E, Malvern, UK).

[0203] Figure 8 The particle size distribution diagram of the lithium compensator according to Example 1 of the present application is shown. It can be seen that the D v 50 is 5μm.

[0204] 6. Measurement of the content of each element in lithium compensator

[0205] The ICP method was used to measure the plasma emission spectrometer model ICAP7400 from Thermo Fisher Scientific, USA. The specific method and principle are: 2g of lithium compensator is gasified in high-energy plasma and then ionized. In this process, all elements have their specific spectral lines, and then the electron multiplier is used for measurement to quantitatively analyze the chemical composition elements in the lithium compensator.

[0206] Performance test of lithium secondary battery

[0207] 1. Cycle performance test of lithium secondary batteries

[0208] At 25°C, the lithium secondary batteries of the above embodiments and comparative examples are charged at a constant current of 1C to a charge cut-off voltage (LFP positive electrode: 3.65V, NCM523 positive electrode: 4.25V), then charged at a constant voltage to a current ≤ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 1C to a discharge cut-off voltage (LFP positive electrode: 2.5V, NCM523 positive electrode: 2.8V), left to stand for 5 minutes, which is a charge and discharge cycle. According to this method, the battery is tested for cyclic charge and discharge until the battery capacity decays to 80%. The number of cycles at this time is the cycle performance of the battery at 25°C. See Tables 1 and 2 below for the results.

[0209] 2. Storage self-discharge test of lithium secondary batteries

[0210] At 25°C, the lithium secondary batteries of the above embodiments and comparative examples were charged to 50% of the power at a constant current rate of 1C, then stored at room temperature for 1 month, and then discharged at a constant current rate of 1C to the discharge cut-off voltage (LFP positive electrode: 2.5V, NCM523 positive electrode: 2.8V), and left to stand for 5 minutes. This is a one-month storage self-discharge test. The difference between the discharge amount before storage and the discharge amount after one month of storage / the discharge amount before storage = the monthly self-discharge rate of the battery. The results are shown in Tables 1 and 2 below. Fig. 9 A capacity variation curve of the lithium secondary battery during charge and discharge according to Example 1 of the present application is shown.

[0211] Table 1

[0212]

[0213] It can be seen from Table 1 above that, compared with Comparative Examples 1 and 2 in which no lithium compensator is used, the cycle life of the lithium secondary battery containing the lithium compensator of the present application at 25°C is significantly improved, and the monthly self-discharge rate of storage at 25°C is also low. In Comparative Examples 3 and 4, although an appropriate amount of lithium compensator is added to the positive electrode, since the I1 / I2 of the lithium compensator is higher than 0.1%, it indicates that its crystallinity is low and the surface impurity content is too high. Therefore, although the cycle performance of the lithium secondary battery of Comparative Examples 1 and 2 without lithium compensator is improved, the self-discharge rate of the battery is still high, which makes the battery prone to capacity decay during long-term storage.

[0214] Embodiment 11

[0215] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.12:0.4:0.6. The composition and parameters of the prepared lithium compensator are shown in Table 2 below.

[0216] Example 12

[0217] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.2:0.4:0.6. The composition and parameters of the prepared lithium compensator are shown in Table 2 below.

[0218] Example 13

[0219] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.4:0.4:0.6. The composition and parameters of the prepared lithium compensator are shown in Table 2 below.

[0220] Embodiment 14

[0221] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S1 of the lithium compensator of this embodiment, the molar ratio of Li, Ni and Cu is 2.5:0.4:0.6. The composition and parameters of the prepared lithium compensator are shown in Table 2 below.

[0222] Table 2

[0223]

[0224] In the present application, the total amount of free lithium in the lithium compensator is adjusted by changing the relative content of the Li element and other elements in the preparation step S1 of preparing the lithium compensator. It can be seen from Table 2 above that when the total amount of free lithium in the lithium compensator is controlled within the above range, the active lithium content and utilization rate in the lithium compensator can be effectively increased, thereby facilitating the improvement of the capacity performance characteristics of the lithium compensator; at the same time, the above lithium compensator has a high electrochemical stability during the charge and discharge process of the battery, which can further reduce the self-discharge rate of the battery.

[0225] Embodiment 15

[0226] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 2 hours. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0227] Example 16

[0228] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 1 hour. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0229] Embodiment 17

[0230] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 0.8h. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0231] Embodiment 18

[0232] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 0.2h. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0233] Embodiment 19

[0234] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 0.1h. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0235] Embodiment 20

[0236] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the washing time of anhydrous ethanol is 0 hours. The composition and parameters of the prepared lithium compensator are shown in Table 3 below.

[0237] Table 3

[0238]

[0239] In the present application, after washing the lithium compensator with anhydrous ethanol for a certain period of time, the residual lithium precipitated on the surface of the lithium compensator during the preparation process can be taken away by the detergent, thereby adjusting its pH value. It can be seen from Table 3 above that when the pH value of the lithium compensator is controlled within the above range, the active lithium retention rate inside the lithium compensator is high, which is conducive to further improving the gram capacity of the lithium compensator.

[0240] Examples 21 to 27

[0241] The lithium secondary battery of the present application is prepared according to the method of embodiment 1, except that in the preparation step S3 of the lithium compensating agent of embodiments 18 to 23, the average particle size D of the product after pulverization and classification is v The composition and parameters of the prepared lithium compensator are shown in Table 4 below.

[0242] Table 4

[0243]

[0244] In this application, the final particle size distribution of the lithium compensator can be controlled by the grading setting of the crushing equipment. It can be seen from Table 4 above that when the volume average particle size of the lithium compensator is within the above range, it can avoid excessive loss of lithium compensator during the crushing process and low yield; at the same time, the surface area of ​​the lithium compensator is controlled, the stability of the lithium compensator in the positive electrode slurry and the active lithium deintercalation rate in the battery are improved, thereby improving the volatilization of the lithium compensator capacity and the dynamics of the battery.

[0245] Embodiment 28

[0246] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the drying time after washing is 10 hours. The composition and parameters of the prepared lithium compensator are shown in Table 5 below.

[0247] Embodiment 29

[0248] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that in the preparation step S4 of the lithium compensator of this embodiment, the drying time after washing is 8 hours. The composition and parameters of the prepared lithium compensator are shown in Table 5 below.

[0249] Embodiment 30

[0250] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that the drying time after washing in step S4 of preparing the lithium compensator of this embodiment is 6 hours. The composition and parameters of the prepared lithium compensator are shown in Table 5 below.

[0251] Embodiment 31

[0252] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that the drying time after washing in step S4 of preparing the lithium compensator of this embodiment is 2 hours. The composition and parameters of the prepared lithium compensator are shown in Table 5 below.

[0253] Embodiment 32

[0254] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that the drying time after washing in step S4 of preparing the lithium compensator of this embodiment is 1 hour. The composition and parameters of the prepared lithium compensator are shown in Table 5 below.

[0255] Table 5

[0256]

[0257] In the present application, the water content of the lithium compensator is controlled by controlling the drying time after washing. When the water content of the lithium compensator is within the above range, the cycle life of the lithium secondary battery is good and the self-discharge rate is low. Preferably, the water content of the lithium compensator is controlled to be no more than 500ppm.

[0258] Embodiments 33 to 35

[0259] The lithium secondary battery of this embodiment is prepared according to the method of embodiment 1, except that the positive electrode active material of this embodiment uses materials with different pH values. The composition and parameters of the prepared positive electrode active material and lithium compensating agent are shown in Table 6 below.

[0260] Table 6

[0261]

[0262] In the present application, when the positive electrode active material is lithium nickel cobalt manganese metal oxide, when the lithium compensator is applied to the positive electrode sheet of the ternary positive electrode active material with different pH values, it can be found that: when the pH of the lithium compensator and the ternary positive electrode active material meets the pH L ≤1.5×pH c When further meeting pH L ≤1.1×pH c At the same time, the capacity of the lithium compensator in the battery can be further improved, the cycle life of the battery is extended, and the storage self-discharge rate is effectively reduced.

[0263] Those skilled in the art should understand that the above-mentioned embodiments are only some specific embodiments for implementing the present application, and in actual applications, various changes and modifications may be made thereto in form and details, all of which fall within the scope of protection of the present application.

Claims

1. A lithium compensator for a lithium secondary battery, wherein: The lithium compensator contains compound L, and the molecular formula of compound L is Li x Ni a Cu 1-a-b M b O2, where 1 ≤ x ≤ 2, 0 < a < 1, 0 ≤ b < 0.1, and M is selected from one or more of Zn, Sn, Mg, Fe, and Mn; Among them, in the XRD pattern of the lithium compensator, there is a first diffraction peak at a diffraction angle 2θ of 42° to 44°, and a second diffraction peak at a diffraction angle 2θ of 25° to 27°. The diffraction intensity of the first diffraction peak is I1, and the diffraction intensity of the second diffraction peak is I2, and it satisfies: I1 / I2 < 0.1%. Among them, the first diffraction peak corresponds to the diffraction peak of nickel oxide on the (200) crystal plane, and the second diffraction peak corresponds to the diffraction peak of the compound L on the (100) crystal plane; Among them, based on the total weight of the lithium compensator, the content of free lithium in the lithium compensator is 0.3 wt% to 5 wt%.

2. The lithium compensating agent according to claim 1, wherein Based on the total weight of the lithium compensator, the content of free lithium in the lithium compensator is 0.3 wt% to 1 wt%.

3. The lithium compensating agent according to claim 2, wherein: The free lithium includes Li2CO3 and LiOH.

4. The lithium compensating agent according to any one of claims 1 to 3, wherein: The pH of the lithium compensator is denoted as pH L , and satisfy 11≤pH L ≤13.

5. The lithium compensating agent according to claim 4, wherein 11.5≤pH L ≤12.5。 6. The lithium compensating agent according to any one of claims 1 to 3, wherein: The water content of the lithium compensator is not higher than 800 ppm.

7. The lithium compensating agent according to claim 6, wherein: The water content of the lithium compensator is not higher than 300 ppm.

8. The lithium compensating agent according to any one of claims 1 to 3, wherein: The volume average particle size D of the lithium compensator v 50 is 2μm~10μm.

9. The lithium compensating agent according to claim 8, wherein: The volume average particle size D of the lithium compensator v 50 is 3μm~6μm.

10. The lithium compensating agent according to any one of claims 1 to 3, wherein: In the molecular formula of the compound L, 0.1 ≤ a ≤ 0.

9.

11. The lithium compensating agent according to claim 10, wherein: In the molecular formula of the compound L, 0.2 ≤ a ≤ 0.

6.

12. The lithium compensating agent according to claim 11, wherein: In the molecular formula of the compound L, 0.2 ≤ a ≤ 0.

4.

13. The lithium compensating agent according to any one of claims 1 to 3, wherein: The compound is Li2Ni 0.1 With 0.9 O2、Li2Ni 0.2 With 0.8 O2、Li2Ni 0.3 With 0.7 O2、Li2Ni 0.4 With 0.6 O2、Li2Ni 0.5 With 0.5 O2、Li2Ni 0.6 With 0.4 O2、Li2Ni 0.7 With 0.3 O2、Li2Ni 0.8 With 0.2 O2、Li2Ni 0.9 With 0.1 O2, or Li2Ni 0.4 With 0.55 Mg 0.05 O2.

14. The lithium compensating agent according to any one of claims 1 to 3, wherein: The lithium compensator further includes a coating located on at least a part of the surface of the compound L, and the coating is selected from one or more of metal fluorides, oxides, and phosphates.

15. The lithium compensating agent according to claim 14, wherein: The metal fluoride is selected from AlF3; the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, and B2O3; the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, and Ni3(PO4)2.

16. A method for preparing the lithium compensator according to any one of claims 1-15, comprising the following steps: S1: Weigh a lithium source, a nickel source, a copper source, and an M source, mix them and then perform ball milling. The molar stoichiometric ratio of Li, Ni, Cu, and M elements is c:a:(1-a-b):b, and 2 ≤ c ≤ 3, 0 < a < 1, 0 ≤ b < 0.

1. M is selected from one or several of Zn, Sn, Mg, Fe, and Mn; and S2: Sinter the ball-milled mixture to obtain the lithium compensator, and the sintering temperature is 600°C to 800°C.

17. The method according to claim 16, wherein: In S1, 2.1 ≤ c ≤ 2.7, 0.1 ≤ a ≤ 0.

9.

18. The method according to claim 17, wherein: In S1, 2.2 ≤ c ≤ 2.6, 0.2 ≤ a ≤ 0.

6.

19. The method according to claim 18, wherein: In S1, 0.2 ≤ a ≤ 0.

4.

20. The method according to claim 16, wherein: In S2, the sintering treatment satisfies at least one of the following conditions: (1) The heating rate is 1°C / min to 10°C / min; (2) The sintering temperature is 650°C to 750°C; (3) The holding time is 5 h to 20 h.

21. The method according to claim 20, wherein: The heating rate is 3°C / min to 5°C / min.

22. The method according to claim 20, wherein: The holding time is 6 h to 10 h.

23. The method according to claim 16, wherein: The method further includes the following steps: S3: The sintered product obtained in S2 is crushed and classified to obtain an average particle size D v 50 is a fractionated product of 2 μm to 10 μm.

24. The method according to claim 23, wherein: The volume average particle size D of the classified product v 50 is 3μm~6μm.

25. The method according to claim 23, wherein: The method further includes the following steps: S4: Wash the product classified by S3 with absolute ethanol or isopropanol, and the washing time is 0 to 2 h; and S5: Dry or perform infrared heating treatment on the product washed in S4 under vacuum or inert atmosphere.

26. The method according to claim 25, wherein: The inert atmosphere includes nitrogen or argon. The temperature of the drying or infrared heating treatment is 100°C to 200°C, and the time of the drying or infrared heating treatment is 2h to 12h.

27. The method according to claim 25, wherein: The washing time is 0.2h to 1.5h.

28. The method of claim 16, wherein: The method further includes the following steps: S6: Ball-milling and coating the lithium compensator with a coating material, where the coating material is selected from one or more of metal fluorides, oxides, and phosphates.

29. The method according to claim 28, wherein: The metal fluoride is selected from AlF3; the oxide is selected from one or more of V2O5, Al2O3, ZrO2, TiO2, ZnO, SiO2, and B2O3; the phosphate is selected from one or more of AlPO4, FePO4, Co3(PO4)2, and Ni3(PO4)2.

30. The method of claim 16, wherein: During the preparation process, the environmental humidity is not higher than 45%.

31. The method according to claim 30, wherein: The environmental humidity is not higher than 30%.

32. The method according to claim 31, wherein: The environmental humidity is not higher than 10%.

33. The method of claim 16, wherein: The lithium source is selected from one or more of Li2O, Li2CO3, Li2C2O4, CH3COOLi, LiOH·H2O, and LiOH; the nickel source is selected from one or more of Ni2CO3, Ni(OH)2, NiO, NiSO4, Ni(CH3COO)2, and NiC2O4; the copper source is selected from one or more of Cu2(OH)2CO3, Cu(OH)2, CuO, CuSO4, CuC2O4, and Cu(CH3COO)2; the M source is selected from one or more of ZnO, SnO, MgO, FeO, MnO, ZnF2, SnF2, MgF2, FeF2, and MnF2.

34. A lithium secondary battery, wherein: The lithium secondary battery contains a lithium compensator, and the lithium compensator is the lithium compensator according to any one of claims 1-15, or the lithium compensator prepared by the method according to any one of claims 16-33.

35. The lithium secondary battery according to claim 34, wherein: The lithium compensator is contained in the positive electrode of the lithium secondary battery, and based on the total mass of the positive electrode active material, the mass ratio of the lithium compensator is 0.1wt% to 10wt%.

36. The lithium secondary battery according to claim 35, wherein: The lithium compensator is contained in the positive electrode of the lithium secondary battery, and based on the total mass of the positive electrode active material, the mass ratio of the lithium compensator is 2wt% to 8wt%.

37. The lithium secondary battery according to any one of claims 35 to 36, wherein: The positive electrode active material includes at least one of the compounds shown in formulas (I) to (III): Li 1+x1 Ni a1 Co b1 M' 1-a1-b1 O 2-y1 A y1 (I); Li 1+x2 Mr a2 M" 2-a2 O 4-d A' d (II); LiFe (1-x3-y3) Mn x3 M”’ y3 PO4(III); Among them, in formula (I), -0.1 ≤ x1 ≤ 0.2, 0 < a1 < 1, 0 ≤ b1 ≤ 1, 0 < a1 + b1 < 1, 0 ≤ y1 < 0.2, M' is one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr, and Ce, and A includes one or more of S, N, F, Cl, Br, and I; Among them, in formula (II), -0.1 ≤ x2 ≤ 0.2, 0 < a2 ≤ 2, 0 ≤ d < 1, M'' includes one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr, and Ce, and A' includes one or more of S, N, F, Cl, Br, and I; Among them, in the formula (III), 0 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.1, and M''' is selected from one or more of transition metal elements other than Fe and Mn and non-transition metal elements.

38. The lithium secondary battery according to claim 37, wherein: 0.5 ≤ a1 < 1, 0 < b1 < 0.5, 0.7 ≤ a1 + b1 < 1, 0 ≤ y < 0.1, M is one or both of Mn and Al, and A is one or both of S and F.

39. The lithium secondary battery according to claim 37, wherein: The positive electrode active material includes at least the compound represented by the formula (III).

40. The lithium secondary battery according to claim 37, wherein: When the positive electrode active material contains the compound represented by formula (I), the pH of the compound represented by formula (I) is denoted as pH c The pH of the lithium compensator is denoted as pH L , and satisfies: pH c ≤pH L .

41. The lithium secondary battery according to claim 40, wherein: pH c ≤pH L And pH L ≤1.5×pH c .

42. The lithium secondary battery according to claim 41, wherein pH c ≤pH L And pH L ≤1.1×pH c .

43. A battery module includes the lithium secondary battery according to any one of claims 34-42.

44. A battery pack includes the lithium secondary battery according to any one of claims 34-42, or the battery module according to claim 43.

45. An electrical device, comprising the lithium secondary battery according to any one of claims 34 to 42, or the battery module according to claim 43, or the battery pack according to claim 44; wherein: The lithium secondary battery, the battery module, or the battery pack is used as a power source for the electrical device.

46. ​​An energy storage system, comprising the lithium secondary battery according to any one of claims 34 to 42, or the battery module according to claim 43, or the battery pack according to claim 44; wherein: The lithium secondary battery, the battery module, or the battery pack is used as an energy storage unit of the energy storage system.

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