Application and method of magnetic field-controlled secondary battery transition metal-based positive electrode materials and interface layers

Abstract

The purpose of the present invention is to provide a fixed magnetic field for reducing the mixing degree of transition metal ions and active ions in transition metal-based positive electrode materials of secondary batteries, maintaining the structural stability of transition metal-based positive electrode materials of secondary batteries, changing CEI film components, and improving the density and uniformity of CEI films, as well as a method for regulating the transition metal-based positive electrode materials and CEI films of secondary batteries by magnetic fields. A fixed magnetic field is introduced during the battery charging process, the magnetic field lines of the fixed magnetic field are fixed at an angle with the positive electrode of the battery, and the active substances in the battery are fully utilized by adjusting the magnetic field strength and the period of magnetic field application, thereby improving the coulomb efficiency of the battery during the first charge and discharge process. The present invention is aimed at the existing transition metal-based positive electrode secondary battery system, and can realize an efficient, simple, and low-cost regulation process, with high repeatability and strong operability, reducing the loss of irreversible capacity of the battery and improving the overall energy density of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of battery application technology, and specifically relates to an application and method of a fixed magnetic field for promoting the formation of a CEI film at the interface between a transition metal-based positive electrode material and an electrode electrolyte of a secondary battery, improving the density and uniformity of the CEI film, and maintaining the structural stability of the transition metal-based positive electrode material of the secondary battery. Background Art

[0002] In today's society, petrochemical energy, which is limited in resources, is gradually depleting. In order to cope with the excessive global carbon emissions and promote the transformation of green energy structure and form, the development of renewable clean energy is imperative. Secondary batteries have attracted extensive attention and research from all over the world due to their high energy density, high power density, long cycle life, no memory effect, and no pollution. As a substitute for traditional chemical energy, they are gradually used in daily life.

[0003] The secondary battery systems that have been developed and utilized in industry are mostly lithium cobalt oxide / graphite batteries, but with the national energy layout and expansion, their energy density can no longer meet the actual production needs. The capacity of secondary battery active materials is closely related to the structure of their positive electrode materials and the stability of the positive electrode and electrolyte interface layer (CEI). At present, the positive electrode material structure is improved by surface modification, regulation of electrolyte components, regulation of preparation conditions and other factors to construct CEI membranes to improve the long cycle performance of batteries and reduce the loss of irreversible capacity of batteries. However, these technical means are limited to improving the transfer properties of some active substances and delaying the rate of battery decay, but it is difficult to prevent irreversible side reactions between electrodes and electrolytes, resulting in a significant reduction in available active substances, and have little effect on the actual capacity and coulomb efficiency. At present, there is still a lot of room for improvement in the research and development of transition metal-based positive electrode materials for secondary batteries. Therefore, designing and developing a simple and effective method to improve the regulation of high specific energy battery materials is crucial to improving the cycle stability, energy density and power density of secondary batteries.

[0004] Among many positive electrode materials, transition metal layered oxides are considered to be one of the most promising high-energy-density positive electrode materials, but there are still some practical problems and challenges that need to be overcome. Taking lithium nickel cobalt manganese oxide (ternary positive electrode material) as an example, its capacity is improved with the continuous increase of nickel content, and the increase of nickel content is accompanied by the dissolution and migration of transition metals, resulting in a chaotic arrangement of metal ions, which in turn causes a reduction in lithium ion deintercalation sites and the generation of lattice stress, leading to the rupture of the bulk structure of the material, and the infiltration of electrolyte to cause interface side reactions. In addition, when the nickel ion content exceeds 80%, the thermodynamic stability of the material will decrease, causing a series of problems such as gas production and thermal runaway.

[0005] How to make transition metal layered oxides maintain their layered structure, build a dense and stable electrode electrolyte interface (CEI), enable the battery to achieve higher active material utilization, and exert more capacity advantages is the key to further commercialization of secondary batteries. Summary of the invention

[0006] In view of the current problems of unstable structure of positive electrode materials in the charge and discharge process of secondary batteries, many side reactions of electrode electrolytes leading to thick and uneven CEI interface layer, low utilization rate of active materials and poor performance of finished batteries, the present invention provides an application of a magnetic field in a secondary battery, and a method for regulating positive electrode materials and CEI films through a magnetic field; the purpose is to provide a simple and efficient process solution for improving the actual performance of high energy density and high power density battery systems.

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide an application of a fixed magnetic field in a secondary battery for improving the battery's initial coulombic efficiency, cycle stability, charge and discharge capacity, and rate performance.

[0008] Another object of the present invention is to provide a secondary battery transition metal-based positive electrode material under constant magnetic field regulation and a method for stabilizing the electrode-electrolyte interface layer thereof.

[0009] The "secondary battery" in the present invention refers to a battery whose positive electrode material contains active ions that can reversibly migrate. The active ions in the electrolyte and the electrons in the external circuit migrate between the positive and negative electrodes. The reversibility of the chemical reaction is utilized to continuously utilize and activate the active substances in the battery. In the control method, the secondary battery includes a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0010] The electrode electrolyte interface layer in the present invention, namely the CEI film, refers to the Li + The electrolyte HOMO energy level is higher than that of the positive electrode material, and the solvent molecules on the surface of the positive electrode lose electrons and react with lithium ions to produce a corresponding oxidation reaction. The reactant film formed on the surface where the positive electrode material contacts the electrolyte is called a CEI film (Cathode Electrolyte Interface). Generally, the CEI film is an electronic insulating layer and an ion conductive layer, which will block the solvent molecules from continuing to lose electrons and react, thereby preventing further corrosion of the positive electrode material and the electrolyte. However, due to the high content of intrinsic organic matter in the electrolyte, the organic components in the CEI film are easily dissolved in the electrolyte, and it is difficult to prevent the corrosion of the positive electrode material. The present invention regulates the energy levels of the positive electrode material and the electrolyte through a magnetic field, promotes the formation of inorganic components in the CEI film, and forms a dense and uniform CEI film through the magnetohydrodynamic effect synergistically generated by the magnetic field and the electric field to effectively solve this problem.

[0011] A fixed magnetic field is used to regulate the transition metal-based positive electrode and CEI film of the secondary battery. Relying on the effects of magnetic force, magnetization, magnetohydrodynamics and spin electronic effects, the magnetic field is used as a non-contact energy transfer method. By regulating the spin state of high-valent transition metal cations, the positive electrode reaction process of the battery is changed, the electrolyte redox potential is changed, and then the electrode / electrolyte interface side reactions are affected, and a more dense and stable electrode / electrolyte interface layer is generated, so as to achieve higher lithium ion utilization and good cycle stability of the battery.

[0012] To achieve the above objectives and other related objectives, the technical solution of the present invention is as follows:

[0013] The first aspect of the present invention provides an application of a fixed magnetic field during the charging process of a secondary battery for reducing the mixing degree of transition metal ions / active ions in the transition metal-based positive electrode material of the secondary battery to maintain the structural stability of the transition metal-based positive electrode material of the secondary battery, increase the inorganic content in the CEI membrane, and improve the density and uniformity of the CEI membrane.

[0014] "The degree of mixing of transition metal ions and active ions in transition metal-based positive electrode materials for secondary batteries" refers to the occupancy of transition metal ions in the positive electrode materials for the original sites of active ions. Transition metal ions refer to high-valent ions in the positive electrode materials that participate in electrochemical reactions and have different spin configurations, such as nickel ions in ternary materials. Active ions refer to ions that serve as energy carriers in the battery, such as lithium, sodium, and potassium ions. The degree of mixing of transition metal ions and active ions is an important indicator for measuring the structural stability of positive electrode materials and thus fully exerting their electrochemical performance.

[0015] "Maintaining the structural stability of the transition metal-based positive electrode material of the secondary battery" means that the structure of the transition metal-based positive electrode material of the secondary battery can be maintained stable under the action of the magnetic field. For materials that are not regulated by the magnetic field, due to the intrinsic properties of the positive electrode material, a large volume change (about 10%) occurs during the cycle process, which will inevitably produce intergranular stress, causing the positive electrode material structure to collapse and the particles to break during the cycle. In the process of magnetic field regulation, the transition metal-containing material has a certain response to the magnetic lines of force, and the orbital angular momentum of the electron will spiral around the direction of the magnetic field, and a magnetic moment with the same direction as the external magnetic field will appear, showing paramagnetic properties. This magnetic moment is generated under the induction of the external magnetic field. Therefore, the lattice stress of the positive electrode material during the charging process is offset by the magnetic moment, which can inhibit the generation of intergranular cracks and alleviate the volume change of the transition metal positive electrode (only 2%, see Example 1 and Comparative Example 1 for details), and has the function of repairing its original structure.

[0016] In the present invention, the applicant has found through a large number of experimental studies that, taking the nickel cobalt manganese oxide lithium positive electrode material (NCM) as an example, the intensity ratio of the (003) crystal plane and the (104) crystal plane after cycling can be used to judge the Ni content in the NCM after cycling. 2+ / Li + The degree of site occupation and mixed arrangement, the higher the degree of mixed arrangement, the fewer lithium ion deintercalation sites, the more unfavorable for the capacity. 2+ / Li + Mixed arrangement (mixed arrangement rate is reduced from 8.459% to 4.848%, see Example 1 and Comparative Example 1 for details), inhibiting the migration of transition metal elements to the alkali metal layer, the magnetic field stabilizes the arrangement of transition metals Ni and Li, maintains the original layered structure, and reduces the Ni 2+ / Li + The deterioration of the crystal structure caused by the mixing.

[0017] The inorganic content in the CEI membrane refers to the content of Li 2 CO 3 The content of inorganic compounds such as LiF and LiF. Since the organic components in the CEI membrane are easily dissolved in the electrolyte, causing further corrosion of the positive electrode material, the mechanical properties and conductive properties of the electrode-electrolyte interface layer can be improved by increasing the content of inorganic components in the CEI membrane.

[0018] "Improving the density and uniformity of the CEI film" means that under the action of the magnetic field, the ions on the positive electrode surface are synergistically regulated by the Lorentz force and the electric field, producing a magnetofluid effect and forming a particle flow that surrounds the deposition. This surrounding deposition is beneficial to the full reaction of the solvent molecules and electrode materials on the positive electrode surface to form a dense and uniform CEI film.

[0019] In the present invention, the applicant has found through a large number of experimental studies that, taking nickel cobalt manganese oxide lithium positive electrode material (NCM) as an example, it is found by X-ray photoelectron spectroscopy analysis that a CEI film (more than 64%, see Example 1 for details) containing more inorganic substances (especially lithium fluoride) is formed on the surface of the positive electrode material after magnetic field regulation. The combination of transition metals and oxygen on the surface of NCM after magnetic field regulation is reduced, which effectively inhibits the dissolution of transition metals and reduces the coordination of transition metals and lattice oxygen. Accordingly, it can be seen through layer-by-layer sputtering that the inner layer of CEI is a mixture of organic and inorganic substances. Such a layer of CEI formed by hybridization of a small amount of organic and rich inorganic substances has the function of stabilizing the surface and bulk structure of the material, preventing further side reactions of the electrolyte and the electrode, and avoiding deterioration of battery performance.

[0020] As a further improvement of the technical solution, the charging process of the secondary battery is completed in a fixed magnetic field. The magnetic lines of force of the fixed magnetic field enter from the positive pole of the battery and exit from the negative pole of the battery. The angle between the magnetic lines of force and the positive pole of the battery is fixed, and the fixed angle range is 45° to 135°. The fixed magnetic field is used to change the electrode reaction process of the battery during the charging process, the electrolyte decomposition potential, the electrode and electrolyte interface reaction and the interface film composition.

[0021] Another aspect of the present invention provides a method for regulating the transition metal-based positive electrode material and CEI film of a secondary battery under a fixed magnetic field. The battery charging process is completed in the fixed magnetic field, and the magnetic field is used to change the transition metal extranuclear electron spin configuration, electrolyte decomposition potential, electrode / electrolyte interface reaction and interface film composition through a non-contact energy transmission method. The setting conditions of the secondary battery charging process include the timing of applying the fixed magnetic field, the angle between the magnetic field and the positive electrode of the battery, and the magnetic field strength.

[0022] As a further improvement of the technical solution, the positive electrode material of the secondary battery includes one or more combinations of transition metal elements such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc.

[0023] As a further improvement of the technical solution, the positive electrode material of the secondary battery includes one or more of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium-rich lithium manganese oxide, lithium vanadium phosphate, lithium manganese phosphate, and lithium cobalt phosphate.

[0024] As a further improvement of the technical solution, in the control method, the period of applying the magnetic field is: the charging process of the secondary battery; more preferably, the period of applying the magnetic field is: the first charging process of the secondary battery.

[0025] As a further improvement of the technical solution, in this control method, the magnetic lines of force of the fixed magnetic field enter from the positive pole of the battery and exit from the negative pole of the battery; the angle between the magnetic lines of force and the electrodes of the battery is fixed, and the optional range is 45° to 135°; preferably, it is 60° to 120°; preferably, it is 80° to 100°, and more preferably, it is 85° to 95°.

[0026] As a further improvement of the technical solution, in the control method, the magnetic field strength of the fixed magnetic field is 20 to 1000 mT, preferably 80 to 640 mT; more preferably, 320 to 400 mT.

[0027] As a further improvement of the technical solution, in the control method, the secondary battery includes a soft-pack type laminated battery or a square shell type laminated battery.

[0028] As a further improvement of the technical solution, in the control method, the secondary battery includes a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0029] As a further improvement of the technical solution, in this method, the positive electrode material of the lithium-ion battery includes one or more of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium-rich lithium manganese oxide, lithium vanadium phosphate, lithium manganese phosphate, lithium iron manganese phosphate, and lithium cobalt phosphate;

[0030] As a further improvement of the technical solution, in the regulation method, the positive electrode material of the sodium ion battery includes one or more of sodium cobaltate, sodium manganate, sodium nickelate, sodium vanadate, sodium manganese phosphate, sodium iron phosphate, sodium vanadium phosphate, sodium nickel iron manganate, sodium-rich sodium manganate, and Prussian blue.

[0031] Preferably, the positive electrode material of the potassium ion battery includes one or more of potassium vanadium phosphate, potassium manganate, potassium nickelate, potassium cobaltate, potassium vanadate, potassium nickel iron manganate, potassium ferrocyanide, and potassium ferromanganate.

[0032] As a further improvement of the technical solution, in the control method, the electrolyte of the secondary battery includes one or more of an ester electrolyte system, an ether electrolyte system, an ionic liquid electrolyte system, and an aqueous electrolyte system.

[0033] Another aspect of the present invention is to provide a secondary battery with a method for regulating the transition metal-based positive electrode material and CEI film of the secondary battery by the magnetic field as described above. The battery charging process is completed in a fixed magnetic field, and the fixed magnetic field is used to change the electrode reaction process, electrolyte decomposition potential, electrode / electrolyte interface reaction and interface film composition of the battery during the charging process.

[0034] As a further improvement of the technical solution, the period during which the magnetic field is applied is: the charging process of the secondary battery, which charging process can be a full charging process or a partial charging process; more preferably, the period during which the magnetic field is applied is: the first charging process of the secondary battery.

[0035] As a further improvement of the technical solution, the angle between the magnetic lines of force of the fixed magnetic field and the electrodes of the battery is fixed, and the angle range is 45° to 135°; preferably, 60° to 120°; preferably, 80° to 100°, and more preferably, 85° to 95°.

[0036] As a further improvement of the technical solution, the magnetic field strength of the fixed magnetic field is 20 to 1000 mT, preferably 80 to 640 mT; more preferably, 320 to 400 mT.

[0037] As a further improvement of the technical solution, the secondary battery includes a soft-pack type laminated battery or a square-shell type laminated battery.

[0038] As a further improvement of the technical solution, the positive electrode material of the secondary battery includes one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, and Cd.

[0039] As a further improvement of the technical solution, the secondary battery includes a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0040] As a further improvement of the technical solution, the positive electrode material of the lithium-ion battery includes one or more of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium-rich lithium manganese oxide, lithium vanadium phosphate, lithium manganese phosphate, lithium iron manganese phosphate, and lithium cobalt phosphate;

[0041] As a further improvement of the technical solution, the positive electrode material of the sodium ion battery includes one or more of sodium cobaltate, sodium manganate, sodium nickelate, sodium vanadate, sodium manganese phosphate, sodium iron phosphate, sodium vanadium phosphate, sodium nickel iron manganate, sodium-rich sodium manganate, and Prussian blue.

[0042] Preferably, the positive electrode material of the potassium ion battery includes one or more of potassium vanadium phosphate, potassium manganate, potassium nickelate, potassium cobaltate, potassium vanadate, potassium nickel iron manganate, potassium ferrocyanide, and potassium ferromanganate.

[0043] As a further improvement of the technical solution, the electrolyte of the secondary battery includes one or more of an ester electrolyte system, an ether electrolyte system, an ionic liquid electrolyte system, and an aqueous electrolyte system.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The fixed magnetic field of the present invention regulates the transition metal-based positive electrode material and CEI film of the secondary battery, improves the positive electrode material structure and CEI film composition, changes the battery reaction process, promotes the main reaction kinetics of the battery positive electrode, and effectively inhibits the side reaction between the electrode active substance and the electrolyte, thereby improving the cycle stability of the battery.

[0046] 2. The magnetic field-assisted secondary battery of the present invention changes the spin configuration of the electrons outside the nucleus of high-valent ions through the action of an external magnetic field, thereby regulating the redox potential of the electrolyte, affecting the composition of the electrode-electrolyte interface layer, effectively stabilizing the crystal structure of the active substance during the cycle, and maintaining the integrity of the microscopic and macroscopic structures.

[0047] 3. The present invention introduces a non-contact energy transmission method during the battery charging process and regulates the positive electrode material and the CEI film through the magnetic field to obtain a battery with high energy density, high power density and long cycle life. Compared with the existing technology, the overall performance of the battery is improved on the basis of the original process, and the synergy of the process method and product performance is achieved.

[0048] 4. The magnetic field of the present invention regulates the positive electrode material and CEI film, and utilizes the magnetism, magnetization, magnetohydrodynamic effect, and spin electronic effect of the magnetic field to effectively improve battery performance. It can be used as a control method for a new type of high energy density and high power density battery system, and has good universality and industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1This is the first cycle charge and discharge curve of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite under magnetic field control in Example 1.

[0050] Figure 2 This is the long cycle curve of charge and discharge of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite under magnetic field control in Example 1.

[0051] Figure 3 This is the rate curve of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite under magnetic field control in Example 1.

[0052] Figure 4 The scanning electron microscope (SEM) images of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite in Example 1 and Comparative Example 1 after 100 cycles of charge and discharge.

[0053] Figure 5 X-ray diffraction spectra and lithium-nickel mixing degree analysis of lithium-ion batteries assembled with lithium nickel cobalt manganese oxide / graphite after 100 cycles of charge and discharge in Example 1 and Comparative Example 1.

[0054] Figure 6 X-ray photoelectron energy spectrum and component analysis of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite in Example 1 and Comparative Example 1 after 100 cycles of charge and discharge.

[0055] Figure 7 It is a schematic diagram of magnetic field regulation of the present invention and the morphology of the lithium nickel cobalt manganese oxide positive electrode and CEI film after magnetic field regulation. DETAILED DESCRIPTION

[0056] In view of the current problems of low coulombic efficiency, low utilization rate of active materials and poor performance of finished batteries in secondary batteries, the present invention provides an application of a fixed magnetic field for reducing the mixing degree of transition metal ions / active ions in transition metal-based positive electrode materials of secondary batteries to maintain the structural stability of transition metal-based positive electrode materials of secondary batteries, increase the inorganic content in CEI membranes, and improve the density and uniformity of CEI membranes.

[0057] According to certain embodiments of the present invention, the secondary battery charging process is completed in a fixed magnetic field, the magnetic lines of force of the fixed magnetic field penetrate into the positive pole of the battery and exit from the negative pole of the battery, the angle between the magnetic lines of force and the electrodes of the battery is fixed, and the fixed magnetic field is used to change the electrode reaction process of the battery during charging, the decomposition potential of the electrolyte, the interface reaction between the electrode and the electrolyte, and the composition of the interface film.

[0058] The present invention also discloses a method for regulating the effect of a magnetic field on a transition metal-based positive electrode material and a CEI film of a secondary battery. In the regulation method, the battery charging process is completed in a fixed magnetic field, and the fixed magnetic field is used to alleviate changes in the material structure, change the electrode reaction process of the positive electrode material during the charging process, the electrolyte decomposition potential, the electrode and electrolyte interface reaction, and the interface film composition.

[0059] According to some embodiments of the present invention, the period during which the magnetic field is applied is: the charging process of the secondary battery; more preferably, the period during which the magnetic field is applied is: the first charging process of the secondary battery.

[0060] During the charging process, lithium ions gradually escape from the transition metal positive electrode material. Due to the intrinsic properties of the positive electrode material, anisotropic volume changes will occur during the cycle (the rate of change is up to 10%), which will inevitably generate intergranular stress, causing the positive electrode material structure to collapse and particles to break during the cycle. The applicant of the present invention has found through extensive research that transition metal-containing materials have a certain response to magnetic lines of force during magnetic field regulation. The orbital angular momentum of electrons will precess around the direction of the magnetic field, and a magnetic moment with the same direction as the external magnetic field will appear, showing paramagnetic properties. This magnetic moment is generated under the induction of the external magnetic field. Therefore, the lattice stress of the positive electrode material during the charging process is offset by the action of the magnetic moment, which can inhibit the generation of intergranular cracks, alleviate the volume change of the transition metal positive electrode to a certain extent (only 2%), and has the function of repairing its original structure.

[0061] In addition, the present applicant has conducted a large number of experiments to verify that, taking the nickel cobalt manganese oxide lithium positive electrode material (NCM) as an example, the intensity ratio of the (003) crystal plane and the (104) crystal plane after the charging process cycle can be used to judge the Ni content in the NCM after the cycle. 2+ / Li + The degree of site occupation and mixed arrangement. The higher the degree of mixed arrangement, the fewer lithium ion deintercalation sites there are, which is more unfavorable for the capacity. The NCM treated with magnetic field effectively reduces the Ni 2+ / Li + Mixed arrangement (mixed arrangement rate is reduced from 8.459% to 4.848%, see Example 1 and Comparative Example 1 for details), inhibiting the migration of transition metal elements to the alkali metal layer, the magnetic field stabilizes the arrangement of transition metals Ni and Li, maintains the original layered structure, and reduces the Ni 2+ / Li + The deterioration of the crystal structure caused by the mixing.

[0062] At the same time, the applicant has found through a lot of research that the timing and period of applying the magnetic field are very important. During the battery charging process, lithium ions migrate from the positive electrode side to the negative electrode side through the positive electrode material and the electrolyte, and electrons are transferred through the external circuit, forming a dense and stable solid electrolyte interface layer with ions and solvent molecules at the electrode electrolyte interface. The magnetic field applied during the charging process promotes ion migration. It is preferred that during the first charging process of the battery, since the HOMO energy level of the electrolyte is higher than that of the positive electrode material, a solid electrolyte interface layer will be formed at the positive electrode interface to change the energy level to stabilize the electrode structure and avoid further side reactions between the active substance and the electrolyte. At this stage, the magnetic field is introduced. The same direction magnetic field can promote ion migration and regulate the electrolyte decomposition energy level, so that the electrode / electrolyte interface layer is more dense and stable, and the first coulomb efficiency and cycle stability of the battery are improved. If a magnetic field is applied during the discharge process of the battery, the direction of the magnetic field is opposite to the direction of ion migration in the battery, and the reverse magnetic field inhibits the migration of carriers, resulting in a decrease in the battery kinetic performance, which has an adverse effect on the formation of the solid electrolyte, causing the battery internal resistance to increase, polarization to intensify, and battery performance to deteriorate. If a magnetic field is applied during the entire charge and discharge process of the battery, the magnetic field in the forward and reverse directions will cause the ion diffusion and migration paths to be disordered, and the battery polarization will increase. If the magnetic field is applied for a long time, the electromagnetic energy will be converted into internal energy, causing the system temperature to rise, which is another major test for the stability of the electrode materials and electrolyte. If the magnetic field is continuously applied during the use of the battery, although it will promote the battery capacity to a certain extent, it will inevitably reduce the battery specific energy density and cannot be actually applied to electronic devices or energy storage systems.

[0063] In the present invention, the applicant has found through a large number of experimental studies that, taking nickel cobalt manganese oxide lithium positive electrode material (NCM) as an example, it is found by X-ray photoelectron spectroscopy analysis that a CEI film (more than 64%, see Example 1 for details) containing more inorganic substances (especially lithium fluoride) is formed on the surface of the positive electrode material after magnetic field regulation during the charging process. The combination of transition metals and oxygen on the surface of NCM after magnetic field regulation is reduced, which effectively inhibits the dissolution of transition metals and reduces the coordination of transition metals and lattice oxygen. Accordingly, it can be seen through layer-by-layer sputtering that the inner layer of CEI is a mixture of organic and inorganic substances. Such a layer of CEI formed by hybridization of a small amount of organic and rich inorganic substances has the function of stabilizing the surface and bulk structure of the material, preventing further side reactions of the electrolyte and the electrode, and avoiding deterioration of battery performance.

[0064] According to certain embodiments of the present invention, the magnetic lines of force of the fixed magnetic field are fixed at an angle with the positive pole of the battery, and the angle range is 45° to 135°; preferably, 60° to 120°; preferably, 80° to 100°, and more preferably, 85° to 95°. The present invention fixes the angle between the magnetic field and the electrode, and the magnetic lines of force penetrate from the positive pole of the electrode material and pass out from the negative pole. It is further preferred that the battery performance is optimal when the angle between the magnetic field and the electrode is 90°. At this time, the Lorentz force acts on the contact surface between the positive electrode material and the electrolyte to promote the formation of a dense and stable solid electrolyte interface layer CEI film, increase the mass transfer rate of the surface components of the positive electrode material, and improve the uniformity of the surface film formation, so as to form an electrolyte interface layer CEI film with uniform components, thickness, structure and high consistency. When the magnetic lines of force penetrate from the negative pole and pass out from the positive pole, the resistance to ion flow inside the battery is increased, causing ions close to the positive electrode surface to form convection, the electrolyte to generate eddy currents, the battery polarization to increase, and the cycle life to decrease. Different from the rotatable magnetic field in the prior art, the applicant has found through long-term and multiple in-depth experimental studies that maintaining the fixed relative position of the magnetic field lines and the electrodes to regulate the positive electrode material has the effective advantage of constructing a uniform and stable electrolyte interface layer CEI film on the surface of the positive electrode, solving the problem in the prior art that the CEI film is thick and uneven, easily corroded by the electrolyte, causing further side reactions, thereby deteriorating battery performance.

[0065] According to some embodiments of the present invention, the magnetic field strength of the fixed magnetic field is 20-1000 mT, preferably 80-640 mT; more preferably, 320-400 mT.

[0066] The present invention adopts a specific magnetic field strength. If the magnetic field strength is too large (>1T) or too small (<20mT), it will have an adverse effect on the charging and discharging and electrochemical performance of the transition metal-based positive electrode material of the secondary battery. According to a large amount of creative work, if the magnetic field strength is too large, the ion diffusion and migration paths in the positive electrode of the battery will be disordered, and the polarization of the positive electrode of the battery will increase. In addition, under strong magnetism, the electromagnetic energy is converted into internal energy, which increases the temperature of the system and requires a high stability window for the electrode material and the electrolyte; if the magnetic field is too small, the magnetic effect is weak, and the stability of the secondary battery is poor. The applicant has found through a large amount of research that the size of the magnetic field is set to 20-1000mT, preferably 80-640mT; more preferably 320-400mT. It can not only improve the stability of the positive electrode material of the high specific energy battery containing transition metal elements, but also maintain good ion diffusion performance and electrochemical performance, forming a dense and uniform CEI film without destroying the structural characteristics between the components in the electrolyte.

[0067] According to some embodiments of the present invention, the secondary battery includes a soft-pack type laminated battery or a square-shell type laminated battery.

[0068] The magnetic field-assisted control method is applied to laminated batteries. Unlike cylindrical (wound) batteries with positive and negative electrodes wrapped around them, the surface of the laminated battery pole piece is flat and will not be bent or deformed at the edge by the winding tension. The magnetic field can act on the positive electrode material in a directional manner, and the direction of the magnetic field lines on the positive electrode material will not be changed due to the pole piece wrapping, ensuring that the magnetic field orientation and the angle with the electrode are constant, thereby achieving the improvement effect on all positive electrode materials during the charging process. When charging, the wound battery itself can be regarded as a coil. The magnetic field generated by the internal circular current movement offsets the external magnetic field, causing lithium ion migration disorder and interfering with the normal charging of the battery.

[0069] According to some embodiments of the present invention, the secondary battery electrode material includes one or more transition metal elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0070] In the transition metal-based cathode materials of secondary batteries, there are many single electrons in the electronic configuration of high-valent transition metal elements, which are easy to lose, so these metals have variable valence states, and some (such as iron, cobalt, and nickel) contain multiple stable metal ions. Due to the existence of empty d orbitals, transition metals can easily form complexes. Metal elements use hybrid orbitals to accept electrons to achieve a stable state of 16 or 18 electrons. Under the action of an external magnetic field, due to the presence of transition metal elements, the electrons on the d orbitals will be rearranged. After the rearrangement, the electrons are completely paired or there are still single electrons. The active substances show corresponding paramagnetism and diamagnetic properties, and the response to the magnetic field is stronger, and the electrochemical activity is higher.

[0071] According to certain embodiments of the present invention, in the process of magnetic field assisted regulation, when the secondary battery is a lithium ion battery, the positive electrode material of the lithium ion battery includes but is not limited to one or more of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium-rich lithium manganese oxide, lithium vanadium phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and lithium cobalt phosphate.

[0072] In lithium-ion batteries, positive electrode materials containing nickel, manganese, cobalt, iron, and vanadium show different cis- and anti-magnetism under magnetic field regulation. Due to the influence of the magnetic field on the extranuclear electron configuration of transition metal elements, the active substances exhibit a more stable thermodynamic state under certain conditions.

[0073] According to certain embodiments of the present invention, in the magnetic field-assisted control method, when the secondary battery is a sodium ion battery, the positive electrode of the sodium ion battery includes but is not limited to one or more of sodium cobaltate, sodium manganate, sodium nickelate, sodium vanadate, sodium manganese phosphate, sodium iron phosphate, sodium vanadium phosphate, sodium nickel iron manganate, sodium-rich sodium manganate, and Prussian blue.

[0074] According to certain embodiments of the present invention, in the magnetic field-assisted control method, when the secondary battery is a potassium ion battery, the positive electrode material includes one or more of potassium vanadium phosphate, potassium manganate, potassium nickelate, potassium cobaltate, potassium vanadate, potassium nickel iron manganate, potassium ferrocyanide, and potassium ferromanganate.

[0075] In sodium and potassium ion batteries, positive electrode materials containing nickel, manganese, cobalt, iron, and vanadium will also respond to magnetic signals, showing corresponding magnetism and thermodynamic stability. Potassium ion radius Larger than the radius of lithium ions Sodium and potassium ions will encounter greater obstacles when migrating in the electrolyte and active material phases. The introduction of a magnetic field has a significant effect on improving the ion diffusion rate.

[0076] Preferably, in the magnetic field-assisted regulation method, the positive electrode material of the lithium-ion battery used for magnetic field-assisted regulation is lithium nickel cobalt manganese oxide, whose chemical formula is LiMO 2 , where M is one or more of the transition metal elements Ni, Co, and Mn, and the chemical formula is LiNi x Co y Mn z O 2 , where 0.01 <x<1,0.01<y<1,0.01<z<1,x+y+z=1。

[0077] The ternary positive electrode containing nickel, manganese and cobalt is still one of the most promising materials for the development of high-energy-density batteries. The magnetic field enables the battery to obtain a higher utilization rate of active materials during the first cycle of charging, inhibiting the Li + / Ni 2+ The key to further commercialization of secondary batteries is to mix and match them to give full play to their capacity advantages.

[0078] Further preferably, in the magnetic field-assisted control method, the selected battery positive electrode material is a ternary material LiNi x Co y Mn z O 2 , further preferably, a high-nickel positive electrode material with x>0.6, the direction of the magnetic lines of force is perpendicular to the direction of the battery, and further preferably, the magnetic lines of force penetrate from the positive electrode and exit from the negative electrode, the magnetic field strength is 80-640mT, and the timing and period of applying the magnetic field is the first charging process of the secondary battery.

[0079] When the angle between the magnetic field and the electrode is 90°, the battery performance is optimal. At this time, the Lorentz force is used to form a dense and stable solid electrolyte interface layer CEI film on the contact surface between the positive electrode material and the electrolyte, which improves the uniformity of the surface film formation, and can form an electrolyte interface layer CEI film with uniform composition, thickness, structure and high consistency. Further preferably, the magnitude of the magnetic field is set to 320-400mT, which can not only improve the structural stability of the high specific energy positive electrode material containing transition metal elements, but also maintain good ion diffusion performance and electrochemical performance, and does not destroy the characteristics between the components in the electrolyte. Further preferably, the timing and period of applying the magnetic field is the first charging process of the secondary battery. By utilizing the influence of the magnetic field on the first cycle charging process of the battery, the positive electrode active material is fully activated, and a uniform and stable electrode electrolyte interface layer CEI film is formed on the positive electrode surface. In particular, for active materials that reach the electrode reaction potential, the electrode reaction process is accelerated under the drive of the magnetic field, and the utilization efficiency of the active material is improved.

[0080] According to certain embodiments of the present invention, according to the above-mentioned control method, in the secondary battery assisted by magnetic field control, the electrolyte of the secondary battery includes but is not limited to one or more of an ester electrolyte system, an ether electrolyte system, a solid electrolyte system, and an aqueous electrolyte system.

[0081] By introducing a magnetic field, the spin configuration of the extranuclear electrons of each component of the electrolyte is regulated, thereby changing the HOMO (highest occupied orbital) and LUMO (lowest unoccupied orbital) energy levels of each component, changing its redox activity, and forming an electrode-electrolyte interface layer on the electrode surface at different potentials. At the same time, the change in redox activity also effectively broadens the electrochemical window of the electrolyte, especially for esters, ethers, solid-state, and aqueous electrolytes, so that the electrolyte can be used at higher potentials and the battery can unleash more energy.

[0082] The present invention provides a method for regulating the secondary battery transition metal-based positive electrode material and CEI film by using a magnetic field. Through the action of the magnetic field, the spin configuration of the extranuclear electrons of the high-valent transition metal in the positive electrode material is changed, thereby changing the charge transfer rate. 2 Chinese Ni 3+ The d electron configuration is t 2g 6 e g 1 , due to e g The orbital points to the coordinated oxygen and forms a σ bond with the 2p orbital of oxygen. The overlap between the full and empty d orbital bands of Ni-Ni is low, and the spin electronic effect of the magnetic field pushes Ni 3+ t 2g The orbital forms a π bond with the oxygen 2p orbital, increasing the overlap between the full and empty d orbital bands of Ni-Ni in the layer, that is, increasing the Ni 4+ / 3+The mixed valence charge transfer capacity, so its electrochemical polarization is reduced, and the high rate performance will be improved to a certain extent. For ternary materials, the Ni content increases, and the charge transfer process is the control step of the electrochemical reaction. Under the assistance of the magnetic field, the charge transfer resistance is reduced, the transfer activity is increased, and the electrochemical extraction and embedding reaction speed is accelerated, thereby improving the electrochemical performance. The rate performance of the positive electrode material directly affects the application of lithium-ion batteries in high-power electrical appliances.

[0083] In the process of magnetic field-assisted regulation, the magnetic field has a certain effect of eliminating the lattice stress of the positive electrode material. The magnetic field can alleviate the volume change of NCM and has the advantage of maintaining (repairing) its original structure. In the absence of a magnetic field, a large number of cracks will appear on the surface of the NCM811 positive electrode due to the existence of intercrystalline stress, which will cause the material structure to collapse and rupture during the cycle.

[0084] The present invention utilizes a magnetic field-assisted secondary battery regulation method, and utilizes the effect of the magnetic field to regulate the HOMO and LUMO energy levels of each component in the electrolyte system. During the battery charging process, a CEI interface layer with a dense structure and uniform components is preferentially formed on the positive electrode side, thereby achieving the effect of avoiding further side reactions between the positive electrode material and the electrolyte.

[0085] The present invention also provides a secondary battery obtained under the control of a fixed magnetic field, wherein the battery charging process is completed in a fixed magnetic field, and the fixed magnetic field is used to alleviate the change of material structure, change the electrode reaction process of the battery positive electrode material during the charging process, the electrolyte decomposition potential, the electrode / electrolyte interface reaction and the interface CEI film composition, and the secondary battery obtained by the control method is as described above. By introducing a non-contact energy transmission method, the magnetic force, magnetization, magnetohydrodynamic effect, and spintronic effect of the magnetic field are utilized to promote the formation of the CEI film at the interface between the transition metal-based positive electrode material of the secondary battery and the electrode electrolyte, maintain the structural stability of the transition metal-based positive electrode material of the secondary battery, and improve the compactness and uniformity of the CEI film, thereby improving the first coulomb efficiency, cycle stability, charge and discharge capacity, and rate performance of the secondary battery.

[0086] The secondary battery with a magnetic field-assisted regulated cathode material according to the present invention has a magnetic field application period during the regulation process as follows: the charging process of the secondary battery; more preferably, the magnetic field application period is: the first charging process of the secondary battery. By utilizing the influence of the magnetic field on the first charging process of the battery cathode material, the cathode active material can be fully activated, and a uniform and stable cathode electrolyte interface (CEI) film can be formed on the cathode surface. Especially for the active material at the electrode reaction potential, the electrode reaction process is accelerated under the drive of the magnetic field, and the utilization efficiency of the active material is improved. The deflection angle between the magnetic field orientation and the cathode material is fixed, ranging from 45° to 135°, and the magnetic field intensity is 20 to 1000 mT. Preferably, the fixed magnetic field is removed after the first charging process of the battery, and the orientation is that the magnetic field is perpendicular to the battery placement direction, with the magnetic field lines penetrating from the positive electrode of the battery and exiting from the negative electrode of the battery, and the magnetic field intensity is 320 to 640 mT. When the angle between the magnetic field and the electrode is 90°, the battery performance is optimal. At this time, a dense and stable solid electrolyte interface layer is formed on the contact surface between the cathode material and the electrolyte through the action of the Lorentz force, improving the uniformity of film formation on the surface, and an electrolyte interface layer (CEI) film with uniform composition, thickness, structure, and high consistency can be formed. Further preferably, the magnitude of the magnetic field is set to 320 to 400 mT, which can not only improve the stability of the high specific energy battery cathode material containing transition metal elements, but also maintain good ion diffusion performance and electrochemical performance, form a dense and uniform CEI film, and do not破坏 the structural characteristics between the components in the electrolyte.

[0087] According to certain embodiments of the present invention, the battery with a magnetic field-assisted regulated cathode material and CEI film of the present invention is a secondary battery, preferably a lithium-ion, sodium-ion, or potassium-ion battery.

[0088] In a lithium-ion battery, the cathode material is one or more of lithium nickelate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium-rich manganate, lithium vanadium phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and lithium cobalt phosphate, preferably lithium nickel cobalt manganate; the chemical formula of lithium nickel cobalt manganate is LiNi x Co y Mn z O 2 , where 0.01 < x < 1, 0.01 < y < 1, 0.01 < z < 1, and x + y + z = 1. A high-nickel cathode material with x = 0.8 is preferred; in a lithium-ion battery, the cathode material containing nickel, manganese, cobalt, iron, and vanadium shows different paramagnetic and diamagnetic properties under magnetic field regulation, and due to the influence of the magnetic field on the nuclear outer electron configuration of transition metal elements, the active material shows a more stable thermodynamic state under certain conditions. The ternary cathode with a high nickel (x > 0.6) content is still one of the most promising materials for developing high specific energy batteries. Through magnetic field regulation, the battery can obtain a higher utilization rate of the cathode active material during the first charging cycle, and inhibit the Li + / Ni 2+The key to further commercialization of secondary batteries is to mix and match them to give full play to their capacity advantages. In addition, when the transition metal elements in secondary batteries are under the action of an external magnetic field, the orbital angular momentum of the electrons rotates around the magnetic field, and the same magnetic moment as the external magnetic field appears. Therefore, the positive electrode materials containing transition metals will respond more obviously to the magnetic field.

[0089] In sodium ion batteries, the positive electrode materials include but are not limited to one or more of sodium cobaltate, sodium manganate, sodium nickelate, sodium vanadate, sodium manganese phosphate, sodium iron phosphate, sodium vanadium phosphate, sodium nickel iron manganate, sodium-rich sodium manganate, and Prussian blue; in potassium ion batteries, the positive electrode materials include but are not limited to one or more of potassium vanadium phosphate, potassium manganate, potassium nickelate, potassium cobaltate, potassium vanadate, potassium nickel iron manganate, potassium ferrocyanide, and potassium ferromanganate.

[0090] In sodium and potassium ion batteries, positive electrode materials containing nickel, manganese, cobalt, iron, and vanadium will also respond to magnetic signals, showing corresponding magnetism and thermodynamic stability. Potassium ion radius Larger than the radius of lithium ions Sodium and potassium ions will encounter greater obstacles when migrating in the electrolyte and active material phases. The introduction of a magnetic field has a significant effect on improving the ion diffusion rate.

[0091] In order to better understand the present invention, the present invention is further described below in conjunction with the examples. The reagents and instruments described in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0092] Example 1 A method for magnetic field regulation of a positive electrode and CEI film of a nickel-cobalt-manganese-oxide lithium battery and a nickel-cobalt-manganese-oxide lithium battery regulated by a magnetic field

[0093] A method for magnetic field regulation of transition metal-based positive electrode materials for secondary batteries, wherein a fixed magnetic field is applied during the first charging process of the battery and then removed, the direction of the magnetic field is perpendicular to the direction of the electrode, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, the magnetic field intensity is 320mT,; the positive and negative active materials of the battery are respectively selected from LiNi 0.8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte.

[0094] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0095] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the battery during the first charging process. The direction of the magnetic field is perpendicular to the direction in which the battery is placed (the angle between the magnetic field and the electrode is 90°). The magnetic force lines penetrate from the positive direction and exit from the negative direction. The magnetic field strength is 320mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 3.0-4.3V. The battery is charged to 4.3V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 3.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0096] First coulombic efficiency = discharge capacity / charge capacity.

[0097] Discharge specific capacity = discharge capacity / mass.

[0098] Cycle test: remove the external magnetic field, cycle the above capacity test process, perform constant current charge and discharge at 200 mA / g, and obtain the n-time capacity retention rate = n-th discharge capacity / first discharge capacity.

[0099] Figure 1 The first cycle charge and discharge curve of the lithium-ion battery assembled with nickel cobalt manganese oxide / graphite under the magnetic field control is shown in FIG. Figure 1 It can be seen that its first cycle charge capacity is 253.5mAh / g, the first cycle discharge capacity is 216.7mAh / g, the first coulomb efficiency is 85.5%, and the energy density is 232Wh / kg. Compared with comparative example 1 (no magnetic field is applied, see below for details), magnetic field regulation improves the first cycle charge and discharge capacity of the nickel cobalt manganese oxide lithium battery, improves the first coulomb efficiency, makes full use of the active substances in the positive and negative electrode materials, and obtains a higher energy density.

[0100] Figure 2 This is a long cycle curve of 300 cycles of charge and discharge of the lithium ion battery assembled by nickel cobalt manganese oxide / graphite under magnetic field control in Example 1. Compared with Comparative Example 1, the cycle life of the nickel cobalt manganese oxide battery is improved, indicating that the chemical stability of the positive electrode material is improved under the action of the magnetic field.

[0101] Figure 3 The rate curves of 0.1C, 0.5C, 1C, 2C, and 3C of the lithium-ion battery assembled by nickel cobalt manganese oxide / graphite under magnetic field control in Example 1. Compared with Comparative Example 1, the rate performance of the nickel cobalt manganese oxide battery is improved, and the battery polarization is significantly improved under high current charge and discharge.

[0102] Figure 4The SEM images of the lithium-ion battery assembled with nickel cobalt manganese oxide / graphite in Example 1 and Comparative Example 1 after 100 cycles of charge and discharge, wherein the SEM instrument is Hitachi S-4800 of Japan. (a), (b), and (c) are the surface morphologies of the NCM811 positive electrode material after 300 cycles after magnetic field-assisted regulation. Compared with the material without magnetic field regulation, the generation of intergranular cracks is significantly suppressed, indicating that the magnetic field has a certain effect of eliminating the lattice stress of the positive electrode material during the magnetic field regulation process. Through magnetic field regulation, the particle size measurement and comparison in the SEM before and after the cycle can be analyzed to obtain that the volume change rate of NCM is about 2%, which alleviates the particle expansion caused by anisotropic stress and has the advantage of maintaining (repairing) its original structure. Figures (d), (e), and (f) show the surface morphologies of the NCM811 cathode material after 300 cycles in the absence of a magnetic field. Due to the intrinsic properties of the NCM811 cathode material, a large volume change (about 10%) will occur during the cycle, further leading to a large number of cracks on the surface. This is because the lattice stress generated during the cycle causes the collapse and rupture of the material structure.

[0103] Figure 5 The X-ray diffraction spectra and the degree of mixing of the lithium-ion battery assembled with lithium nickel cobalt manganese oxide / graphite in Example 1 (magnetization treatment) and Comparative Example 1 (control group) after 100 cycles of charge and discharge are shown in Figure 1. The X-ray diffractometer used is from Bruker AXS Co., Ltd., Germany. Compared with Comparative Example 1, the XRD pattern after the cycle shows that the intensity ratio of the (003) crystal plane and the (104) crystal plane can be used to judge the Ni content in the NCM after the cycle. 2+ / Li + The degree of mixing, the NCM treated by magnetic field effectively reduced the Ni 2+ / Li + After XRD refinement, the degree of lithium-nickel mixing was reduced from 9.840% to 5.712% after magnetic field regulation, which was significantly better than that of the positive electrode material without magnetic field regulation. This shows that magnetic field regulation effectively inhibits the migration of transition metal elements to the alkali metal layer, and the magnetic field stabilizes the arrangement of transition metal Ni and Li, maintains the original layered structure, and reduces the Ni 2+ / Li + The deterioration of the crystal structure caused by the mixing.

[0104] Figure 6The X-ray photoelectron energy spectrum and component analysis of the lithium ion battery assembled by nickel cobalt manganese oxide / graphite in Example 1 (magnetic field control) and Comparative Example 1 (control group) after 100 cycles of charge and discharge. Through XPS characterization and analysis of CEI on the outer surface of NCM after cycling, a CEI film containing more inorganic components (LiF content exceeds 64%) is formed on the electrode surface after magnetic field control, and the increase in the content of inorganic LiF in the CEI film helps to improve the mechanical properties of the interface layer, and plays an isolating role in the contact corrosion of the electrode and the electrolyte in subsequent cycles. The combination of transition metal and oxygen on the surface of NCM after magnetic field control is reduced, which effectively inhibits the dissolution of transition metals and reduces the coordination of transition metals and lattice oxygen. Accordingly, it can be seen from XPS layer-by-layer sputtering that the inner layer of the CEI film is a mixture of organic and inorganic substances. Such a layer of CEI film formed by hybridization with less organic components and more inorganic components has the function of stabilizing the surface and bulk structure of the material, improving the compactness of the CEI film, and playing a role in uniform film formation.

[0105] Figure 7 It is a schematic diagram of the positive electrode and CEI film of the secondary battery regulated by a fixed magnetic field in Example 1. The direction of the magnetic field is perpendicular to the direction of the electrode, and the magnetic lines of force penetrate from the positive electrode direction and pass out from the negative electrode direction. Compared with Comparative Example 2 (reverse magnetic field, see below for details) and Comparative Example 5 (rotating magnetic field, see below for details), the battery performance is significantly improved. At this time, a dense and stable solid electrolyte interface layer CEI film is formed on the contact surface of the electrode material and the electrolyte through the Lorentz force, which improves the uniformity of the surface film formation, and can form an electrolyte interface layer CEI film with uniform composition, thickness, structure and high consistency. When the magnetic lines of force penetrate from the negative electrode and the positive electrode, the resistance to ion flow inside the battery is increased, causing ions close to the electrode surface to form convection, the electrolyte generates eddy currents, the battery polarization increases, and the cycle life is reduced. Keeping the relative position of the magnetic field lines and the electrodes fixed, and constructing a uniform and stable electrolyte interface layer on the surface of the positive and negative electrodes, can solve the problems of low initial efficiency of batteries and low utilization rate of active substances in the prior art.

[0106] Example 2 A method for magnetic field regulation of a positive electrode and CEI membrane of a lithium manganese phosphate battery and a lithium manganese phosphate battery regulated by a magnetic field

[0107] A method for magnetic field regulation of positive electrode materials of lithium manganese phosphate batteries, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the direction of the magnetic field is perpendicular to the direction of the electrode, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 100mT; the positive and negative active materials of the battery are respectively selected from LiMnPO 4 (lithium manganese phosphate) and natural graphite, the electrolyte is 1mol / L LiPF 6 -EC / DEC ester electrolyte.

[0108] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0109] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the battery during the first charging process. The direction of the magnetic field is perpendicular to the direction in which the battery is placed. The magnetic force lines penetrate from the negative pole direction and exit from the positive pole direction. The magnetic field strength is 100mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 3.0-4.3V. The battery is charged to 4.3V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 3.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0110] Example 3 A method for magnetic field regulation of lithium vanadium phosphate battery positive electrode and CEI membrane and lithium vanadium phosphate battery after magnetic field regulation

[0111] A method for magnetic field regulation of positive electrode materials of lithium vanadium phosphate batteries, wherein a fixed magnetic field is applied during the first charging process of the battery and then removed, the direction of the magnetic field is perpendicular to the direction of the electrode, the magnetic lines of force penetrate from the positive electrode direction and pass out from the negative electrode direction, the magnetic field strength is 120mT, and the positive and negative active materials of the battery are respectively selected from Li 3 V 2 (PO 4 ) 3 (lithium vanadium phosphate) and MCMB (mesophase carbon microspheres), the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte.

[0112] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0113] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with horizontal magnetic lines of force. A fixed magnetic field is applied to the first charging process of the battery. The direction of the magnetic field is perpendicular to the direction of the battery. The magnetic lines of force penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 120mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0114] Example 4 A method for magnetic field regulation of a positive electrode and CEI film of a lithium nickel-acid battery and a lithium nickel-acid battery regulated by a magnetic field

[0115] A method for magnetic field regulation of positive electrode materials of lithium nickel-acid battery, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 60°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field intensity is 320mT; the positive and negative active materials of the battery are respectively LiNiO 2 (lithium nickel oxide) and SiC (silicon carbide), and the electrolyte is 1mol / L LiFSI-EC / DEC / DMC ester electrolyte.

[0116] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0117] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 60°. The magnetic force lines penetrate from the negative pole direction and exit from the positive pole direction. The magnetic field strength is 320mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0118] Example 5 A method for regulating the positive electrode and CEI film of a lithium manganese oxide battery by a magnetic field and a lithium manganese oxide battery after magnetic field regulation

[0119] A method for regulating the positive electrode material of a lithium manganese oxide battery by a magnetic field, wherein a fixed magnetic field is applied to the battery during the first charging process and then removed, the angle between the magnetic field direction and the electrode is 60°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 360mT; the positive and negative active materials of the battery are respectively selected from LiMn 2 O 4 (LiMnO) and SnO 2 (tin dioxide), the electrolyte is 1mol / L LiPF 6 -EC / DMC-5% FEC ester electrolyte.

[0120] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0121] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 60°. The magnetic force lines penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 360mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0122] Example 6 A method for magnetic field regulation of a positive electrode and CEI film of a lithium nickel manganese oxide battery and a lithium nickel manganese oxide battery regulated by a magnetic field

[0123] A method for magnetic field regulation of positive electrode materials of lithium nickel manganese oxide batteries, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 60°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 380mT; the positive and negative active materials of the battery are respectively LiMnNiO 2 (lithium nickel manganese oxide) and P / C (phosphorus carbon composite), and the electrolyte is 1 mol / L LiTFSI-EC / EMC / DMC ester electrolyte.

[0124] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0125] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 60°. The magnetic force lines penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 380mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0126] Example 7 A method for magnetic field regulation of a positive electrode and CEI film of a lithium cobalt phosphate battery and a lithium cobalt phosphate battery regulated by a magnetic field

[0127] A method for magnetic field regulation of cobalt phosphate lithium battery positive electrode material, the fixed magnetic field is applied to the first charging process of the battery, and then removed, the magnetic field direction and the electrode angle is 50 degrees, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, the magnetic field strength is 220mT; the positive and negative active materials of the battery are respectively LiCoPO 4 (lithium cobalt phosphate) and CoO (cobalt oxide), the electrolyte is 1 mol / L LiPF 6 -EC / DMC-5% FEC ester electrolyte.

[0128] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0129] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in a magnetic field with an angle of 50° between the magnetic field direction and the electrode. The fixed magnetic field is applied to the first charging process of the battery. The magnetic lines of force penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 220mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 3.0-4.5V. The battery is charged to 4.5V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 3.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0130] Example 8 A method for magnetic field regulation of a positive electrode and CEI film of a nickel-cobalt-manganese-oxide lithium battery and a nickel-cobalt-manganese-oxide lithium battery regulated by a magnetic field

[0131] A method for magnetic field regulation of positive electrode materials of nickel cobalt lithium manganese oxide batteries, wherein a fixed magnetic field is applied to the entire charge and discharge process of the battery and then removed, the direction of the magnetic field is perpendicular to the direction of the electrode, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field intensity is 320mT; the positive and negative active materials of the battery are respectively selected from LiNi 0.8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte.

[0132] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0133] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C, the above battery is placed in an electromagnetic field with the magnetic force lines horizontal, and a fixed magnetic field is applied to the entire charge and discharge process of the battery. The magnetic field direction is perpendicular to the battery placement direction, and the magnetic force lines penetrate from the positive pole direction and pass out from the negative pole direction. The magnetic field strength is 320mT. At the same time, constant current charging and discharging is adopted, and the voltage control range is 3.0~4.3V. The battery is charged to 4.3V at a constant current of 20mA / g to obtain the charging capacity, and then left to stand for 1min, and discharged to 3.0V at a constant current of 20mA / g to obtain the discharge capacity. The battery charging and discharging process is completed by three cycles.

[0134] Example 9 A method for magnetic field regulation of a positive electrode and CEI film of a nickel-cobalt-manganese-oxide lithium battery and a nickel-cobalt-manganese-oxide lithium battery regulated by a magnetic field

[0135] A method for magnetic field regulation of positive electrode materials of nickel cobalt lithium manganese oxide batteries, wherein a fixed magnetic field is applied to the entire charging process of the battery, the direction of the magnetic field is perpendicular to the direction of the electrode, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 320mT; the positive and negative active materials of the battery are respectively selected from LiNi 0.8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte.

[0136] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0137] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C, the above battery is placed in an electromagnetic field with the magnetic force lines horizontal, and a fixed magnetic field is applied to the entire charging process of the battery. The magnetic field direction is perpendicular to the battery placement direction, and the magnetic force lines penetrate from the positive pole direction and pass out from the negative pole direction. The magnetic field strength is 320mT. At the same time, constant current charging and discharging is adopted, and the voltage control range is 3.0~4.3V. The battery is charged to 4.3V at a constant current of 20mA / g to obtain the charging capacity, and then left to stand for 1min, and discharged to 3.0V at a constant current of 20mA / g to obtain the discharge capacity. The battery charging and discharging process is completed by three cycles.

[0138] Example 10 A method for magnetic field regulation of sodium vanadium phosphate battery positive electrode and CEI membrane and a sodium vanadium phosphate battery regulated by magnetic field

[0139] A method for magnetic field regulation of positive electrode materials of sodium vanadium phosphate battery, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 100°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 160mT; the positive and negative active materials of the battery are respectively selected from Na 3 V 2 (PO 4 ) 3 (sodium vanadium phosphate) and hard carbon, the electrolyte is 1 mol / L NaClO 4 -EC / DEC ester electrolyte.

[0140] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0141] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in a magnetic field with an angle of 100° between the magnetic field direction and the electrode. A fixed magnetic field is applied to the first charging process of the battery. The magnetic lines of force penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 160mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0142] Example 11 A method for regulating the positive electrode and CEI membrane of a sodium vanadate battery by a magnetic field and a sodium vanadate battery after magnetic field regulation

[0143] A method for magnetic field regulation of positive electrode materials of sodium vanadate batteries, wherein a fixed magnetic field is applied during the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 70°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 320mT; the positive and negative active materials of the battery are respectively selected from NaV 6 O 15 (sodium vanadate) and graphite, the electrolyte is 1mol / LNaClO 4 -EC / DMC-5% FEC ester electrolyte.

[0144] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0145] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 70°. The magnetic force lines penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 320mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 1.5-4.0V. The battery is charged to 4.0V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 1.5V at a constant current of 20mA / g to obtain the discharge capacity.

[0146] Example 12 A method for magnetic field regulation of a potassium ferrocyanide battery positive electrode and a CEI membrane and a potassium ferrocyanide battery regulated by a magnetic field

[0147] A method for magnetic field regulation of positive electrode materials of potassium ferrocyanide battery, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 70°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 400mT; the positive and negative active materials of the battery are selected from K 4 Fe(CN) 6 (potassium ferrocyanide) and graphite, the electrolyte is 1mol / LKPF 6-EC / PC-5% FEC ester electrolyte.

[0148] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0149] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 70°. The magnetic force lines penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 400mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0150] Example 13 A method for magnetic field regulation of potassium vanadium phosphate battery positive electrode and CEI membrane and potassium vanadium phosphate battery after magnetic field regulation

[0151] A method for magnetic field regulation of positive electrode materials of potassium vanadium phosphate battery, wherein a fixed magnetic field is applied to the first charging process of the battery and then removed, the angle between the magnetic field direction and the electrode is 70°, the magnetic field lines penetrate from the positive electrode direction and pass out from the negative electrode direction, and the magnetic field strength is 240mT; the positive and negative active materials of the battery are selected from K 3 V 2 (PO 4 ) 3 (potassium vanadium phosphate) and graphite, the electrolyte is 1mol / LKPF 6 -EC / DEC ester electrolyte.

[0152] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0153] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with the magnetic force lines horizontal in the direction. A fixed magnetic field is applied to the first charging process of the battery. The angle between the magnetic field direction and the electrode is 70°. The magnetic force lines penetrate from the negative pole direction and exit from the positive pole direction. The magnetic field strength is 240mT. Constant current charging and discharging is adopted at the same time. The voltage control range is 2.0-3.8V. The battery is charged to 3.8V at a constant current of 20mA / g to obtain the charging capacity. After standing for 1 minute, the battery is discharged to 2.0V at a constant current of 20mA / g to obtain the discharge capacity.

[0154] Comparative Example 1: Nickel-cobalt-manganese-oxide lithium battery test

[0155] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte, constant current charging and discharging, voltage control range of 3.0~4.3V, constant current charging to 4.3V at 20mA / g, charging capacity, standing for 1min, constant current discharging to 3.0V at 20mA / g, discharging capacity. The difference from Example 1 is that the charging process is carried out without an external magnetic field.

[0156] Comparative Example 2: A nickel-cobalt-manganese-oxide lithium battery under reverse magnetic field control

[0157] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte, apply a fixed magnetic field to the first charging process of the battery, then remove it, the direction of the magnetic field is perpendicular to the direction of the battery placement, the magnetic field lines penetrate from the negative pole direction and pass out from the positive pole direction, the magnetic field strength is 320mT, apply a fixed magnetic field to the first charging process of the battery; adopt constant current charging and discharging, the voltage control range is 3.0~4.3V, charge to 4.3V with a constant current of 20mA / g, obtain the charging capacity, stand for 1min, discharge to 3.0V with a constant current of 20mA / g, and obtain the discharge capacity. The difference from Example 1 is that the battery charging is carried out under a reverse magnetic field.

[0158] Comparative Example 3: A lithium-sulfur battery under magnetic field control

[0159] A magnetic field-controlled lithium-sulfur battery applies a fixed magnetic field during the first charging process of the battery and then removes it. The direction of the magnetic field is perpendicular to the placement direction of the battery. The magnetic lines of force penetrate from the positive electrode direction and exit from the negative electrode direction. The magnetic field strength is 320mT. The positive and negative active materials of the battery are SPAN (sulfurized polyacrylonitrile) and metallic lithium respectively, and the electrolyte is 1mol / LLiTFSI-DOL / DME ether electrolyte.

[0160] Assemble 5 identical soft-pack batteries and test the electrochemical performance according to the following steps to obtain the average value.

[0161] Capacity test: When tested with the Blue Electric test system, the temperature is 25°C. The above-mentioned battery is placed in an electromagnetic field with horizontal magnetic lines of force. The direction of the magnetic field is perpendicular to the direction of the battery placement. The magnetic lines of force penetrate from the positive pole direction and exit from the negative pole direction. The magnetic field strength is 320mT. A fixed magnetic field is applied to the first charging process of the battery. At the same time, constant current charging and discharging is adopted. The voltage control range is 1.7~2.8V. The battery is discharged to 1.7V at a constant current of 160mA / g to obtain the discharge capacity. After standing for 1 minute, the battery is charged to 2.8V at a constant current of 160mA / g to obtain the charging capacity.

[0162] Comparative Example 4 Lithium-Sulfur Battery Test

[0163] The positive and negative active materials of the battery are SPAN (sulfurized polyacrylonitrile) and metallic lithium, respectively, and the electrolyte is 1mol / LLiTFSI-DOL / DME ether electrolyte. Constant current charging and discharging is used, and the voltage control range is 1.7-2.8V. The discharge capacity is obtained by discharging at a constant current of 160mA / g to 1.7V, and then standing for 1min, and charging at a constant current of 160mA / g to 2.8V to obtain the charging capacity. The difference from Comparative Example 3 is that the charging process is carried out without an external magnetic field.

[0164] Comparative Example 5: A nickel-cobalt-manganese-oxide lithium battery under the control of a rotating magnetic field

[0165] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte, constant current charging and discharging, voltage control range of 3.0~4.3V, constant current charging to 4.3V at 20mA / g, charging capacity, standing for 1min, constant current discharging to 3.0V at 20mA / g, discharge capacity. A fixed magnetic field is applied to the first charging process of the battery, then removed, the magnetic field is applied to both sides of the positive and negative electrodes, the angle with the electrode is 0~360°, and the intensity is 320mT; the difference from Example 1 is that charging is carried out under a rotating magnetic field.

[0166] Comparative Example 6: A nickel-cobalt-manganese-oxide lithium battery under strong magnetic field control

[0167] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6-EC / DEC ester electrolyte, constant current charging and discharging, voltage control range of 3.0~4.3V, constant current charging to 4.3V at 20mA / g, charging capacity, standing for 1min, constant current discharging to 3.0V at 20mA / g, discharging capacity. A fixed magnetic field is applied to the first charging process of the battery, and then removed, the direction of the magnetic field is perpendicular to the direction of battery placement, the magnetic lines of force penetrate from the positive pole direction and pass out from the negative pole direction, and the magnetic field strength is 1200mT; the difference from Example 1 is that charging is carried out under a strong magnetic field (1200mT).

[0168] Comparative Example 7: A nickel-cobalt-manganese-oxide lithium battery under weak magnetic field control

[0169] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte, constant current charging and discharging, voltage control range of 3.0~4.3V, constant current charging to 4.3V at 20mA / g, charging capacity, standing for 1min, constant current discharging to 3.0V at 20mA / g, discharge capacity. Apply a fixed magnetic field to the battery and remove it after charging once, the direction of the magnetic field is perpendicular to the direction of battery placement, the magnetic field lines penetrate from the positive pole direction and pass out from the negative pole direction, and the magnetic field strength is 10mT; the difference from Example 1 is that the charging process is carried out under a weak magnetic field.

[0170] Comparative Example 8: A nickel-cobalt-manganese-oxide lithium battery under magnetic field control

[0171] The positive and negative active materials of the battery are LiNi0. 8 Co 0.1 Mn 0.1 O 2 (lithium nickel cobalt manganese oxide) and artificial graphite, the electrolyte is 1 mol / L LiPF 6 -EC / DEC ester electrolyte, using constant current charging and discharging, the voltage control range is 3.0~4.3V, charging to 4.3V with a constant current of 20mA / g, obtaining the charging capacity, standing for 1min, discharging to 3.0V with a constant current of 20mA / g, obtaining the discharge capacity. A fixed magnetic field is applied to the discharge process of the battery after one charge, and then removed. The direction of the magnetic field is perpendicular to the direction of the battery placement, and the magnetic lines of force penetrate from the positive pole direction and pass out from the negative pole direction. The magnetic field strength is 320mT; the difference from Example 1 is that the magnetic field is applied to the discharge process of the battery after one charge.

[0172] The composition and electrochemical performance of the secondary ion batteries in the embodiments and comparative examples disclosed in the present invention are tested, and the results are shown in Table 1.

[0173] Table 1

[0174]

[0175] By comparing the above-mentioned Example 1 with the comparative example 1, it can be seen that the present invention utilizes a magnetic field to regulate the charging process of the transition metal-based positive electrode material of the secondary battery, reduces the mixing degree of transition metal ions / active ions in the transition metal-based positive electrode material of the secondary battery to maintain the structural stability of the transition metal-based positive electrode material of the secondary battery, increases the inorganic content in the CEI film, and improves the density and uniformity of the CEI film, thereby improving the first coulombic efficiency of the battery, significantly improving the battery capacity retention rate, promoting the utilization rate of the positive electrode active material, and improving its cycle performance.

[0176] By comparing the above-mentioned Example 1 with Comparative Example 2, it can be seen that the magnetic lines of force in the present invention penetrate from the positive electrode and pass out from the negative electrode, which significantly improves the initial coulomb efficiency and capacity retention rate of the battery. The reason is that when the magnetic lines of force are in the same direction as the ion migration direction, the mass transfer process of ions on the electrode surface can be promoted. At the same time, due to the action of the Lorentz force, the ions can be uniformly deposited on the electrode surface to form a dense and stable solid electrolyte interface layer CEI film, improve the uniformity of the surface film formation, and form an electrolyte interface layer CEI film with uniform composition, thickness, structure and high consistency. When the magnetic lines of force penetrate from the negative electrode and pass out from the positive electrode, the resistance to ion flow inside the battery increases, causing ions close to the electrode surface to form convection, the electrolyte to generate eddy currents, the battery polarization to increase, and the cycle life to decrease.

[0177] By comparing the above-mentioned Example 1 with the comparative example 5, it can be seen that the fixed angle between the magnetic field and the electrode in the present invention significantly improves the electrochemical performance of the battery, including the initial coulombic efficiency and cycle stability, compared with the prior art solution in which the magnetic field is applied to both sides of the positive and negative electrodes in rotation. The reason is that, as mentioned above, the relative position of the magnetic field lines and the electrodes is kept fixed, and the magnetic field lines only enter from the positive electrode side and exit from the negative electrode side, which promotes ion migration and constructs a uniform and stable electrolyte interface layer on the electrode surface, thereby solving the problems of low initial efficiency of the battery and low utilization rate of active materials in the prior art.

[0178] By comparing the above comparative examples 3 and 4, it can be seen that for electrode materials that do not contain transition metal elements, the external magnetic field only changes the electrolyte decomposition and film formation potential, and has limited effect on the positive electrode material. The reason is that the magnetic field has a weak effect on the extranuclear electron configuration of the sulfide positive electrode, and has a certain improvement effect on the performance of the battery. On the contrary, magnetic field regulation has a significant effect in promoting the formation of the CEI film at the electrode electrolyte interface layer, maintaining the structural stability of the transition metal-based positive electrode material of the secondary battery, and improving the density and uniformity of the film, which has an outstanding contribution to the improvement of battery performance.

[0179] By comparing the above embodiment 1 with comparative examples 6 and 7, it can be seen that excessive or insufficient magnetic field strength has an adverse effect on the charging and electrochemical performance of the secondary battery. When the magnetic field strength is too large, the diffusion and migration paths of ions in the battery are disordered, and the polarization of the battery increases. In addition, under strong magnetism, the electromagnetic energy is converted into internal energy, which increases the temperature of the system and requires a high stability window for electrode materials and electrolytes. When the magnetic field is too small, the magnetic effect is weak, and the stability of the battery system without transition metals is poor. The applicant has found through a lot of research that the size of the magnetic field is set to 20-1000mT, preferably 80-640mT; more preferably 320-400mT. It can not only improve the stability of high-energy battery materials containing transition metal elements, but also maintain good ion diffusion performance and electrochemical performance, and does not destroy the structural characteristics between the components in the electrolyte.

[0180] Through the comparison of the above-mentioned Examples 1 to 13, it can be seen that the angle between the magnetic lines of force of the fixed magnetic field and the positive pole of the battery is 45° to 135°, which has a certain promoting effect on the improvement of battery performance, preferably, it is 60° to 120°; more preferably, when the angle between the magnetic lines of force and the positive pole of the battery is 80° to 100°, the battery performance is optimal. At this time, the Lorentz force is used to form a dense and stable solid electrolyte interface layer on the contact surface between the electrode material and the electrolyte, which improves the uniformity of the surface film formation and can form an electrolyte interface layer CEI film with uniform composition, thickness, structure and high consistency. Different from the rotatable magnetic field of the prior art, the applicant has found through long-term and multiple in-depth experimental studies that keeping the relative position of the magnetic field lines and the electrode fixed can improve the first efficiency of the battery in the prior art, improve the battery cycle stability, and increase the battery charge and discharge capacity.

[0181] By comparing the above-mentioned Examples 1, 8, and 9 with Comparative Example 8, it can be seen that the magnetic field auxiliary effect is best when the fixed magnetic field is applied to the first charging process of the positive electrode material charging and discharging process. This is because during the battery charging process, lithium ions migrate from the positive electrode side to the negative electrode side through the positive electrode material and the electrolyte to reach the negative electrode surface. At the same time, electrons are transferred through the external circuit, along the current collector, through the negative electrode material body phase, and reach the electrode electrolyte interface. They form a dense and stable solid electrolyte interface layer CEI film with ions and solvent molecules at the positive electrode electrolyte interface. The magnetic field applied during charging promotes ion migration. Comparative Example 8 uses a magnetic field applied during the discharge process. Since the direction of ion migration is opposite to the direction of the magnetic field, the resistance to ion flow inside the battery increases, causing ions close to the electrode surface to form convection, the electrolyte generates eddy currents, the battery polarization increases, the cycle life decreases, and the performance decreases. As shown in Example 8, the application of the entire battery charging process is second to the battery performance improvement. This is because the long-term application of the magnetic field converts electromagnetic energy into internal energy, which increases the system temperature and affects the stability of the positive electrode material and the electrolyte. As shown in Example 9, if a magnetic field is applied during the entire charge and discharge process of the battery positive electrode material, the battery performance is also improved to a certain extent. This is because during the discharge process, the magnetic field in the reverse direction will cause the ion diffusion and migration paths to be disordered, the battery polarization will increase, and the battery performance will be improved with the assistance of the forward magnetic field.

[0182] In summary, the present invention provides a fixed magnetic field for promoting the formation of a CEI film at the interface between a transition metal-based positive electrode material and an electrode electrolyte of a secondary battery, improving the compactness and uniformity of the CEI film, and maintaining the structural stability of a transition metal-based positive electrode material of a secondary battery. The angle between the magnetic lines of force of the fixed magnetic field and the positive electrode of the battery is fixed, and by adjusting the intensity of the magnetic field and the timing and period of applying the magnetic field, the active substances in the battery can be fully utilized, thereby improving the coulombic efficiency of the battery during the first charge and discharge process. The present invention is aimed at an existing secondary battery system, and can realize an efficient, simple, and low-cost process with high repeatability and strong operability, reduce the loss of irreversible capacity of the battery, and improve the overall energy density of the battery. It can be used as a new method with simple process and excellent performance, and has good application prospects.

[0183] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for regulating the effect of magnetic field on transition metal-based cathode materials and CEI films of secondary batteries, characterized in that: The charging process of the secondary battery is completed in a fixed magnetic field, the magnetic field lines of the fixed magnetic field are at a fixed angle with the positive electrode of the battery, and the fixed magnetic field is used to reduce the mixing degree of transition metal ions and active ions in the transition metal-based positive electrode material of the secondary battery, maintain the structural stability of the transition metal-based positive electrode material of the secondary battery, increase the inorganic content in the CEI film, and improve the density and uniformity of the CEI film; in, The secondary battery comprises a lithium ion battery; the positive electrode material of the lithium ion battery comprises LiNi x Co y Mn z O2, of which 0.01 <x<1,0.01<y<1,0.01<z<1,x+y+z=1; The magnetic field regulation is applied during: the first charging process of the secondary battery; The magnetic field lines of the fixed magnetic field penetrate from the positive electrode of the battery and pass out from the negative electrode of the battery; The magnetic field strength of the fixed magnetic field is 320-400 mT; The secondary battery includes a soft-pack type laminated battery or a square-shell type laminated battery.

2. The control method according to claim 1, characterized in that: The angle between the magnetic force lines and the positive pole of the battery is fixed at 45° to 135°.

3. The control method according to claim 1, characterized in that: The angle between the magnetic force lines and the positive pole of the battery is fixed at 60° to 120°.

4. The control method according to claim 1, characterized in that: The angle between the magnetic force lines and the positive pole of the battery is fixed at 80° to 100°.

5. The control method according to claim 1, characterized in that: The electrolyte of the secondary battery includes one or more of an ester electrolyte system, an ether electrolyte system, an ionic liquid electrolyte system, and an aqueous electrolyte system.

6. A secondary battery prepared by the method for regulating the magnetic field on the transition metal-based positive electrode material and CEI film of a secondary battery as described in any one of claims 1 to 5.

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