Fluorine-containing positive electrode material, preparation method and application

Abstract

This invention discloses a fluorine-containing cathode material, its preparation method, and its application. The fluorine-containing cathode material includes a bulk material and a fluorine-containing lithium cobalt compound coated on the bulk material. The chemical formula of the fluorine-containing cathode material is Li. 1+x (Ni (1‑c‑d) Co d Mn c ) 1‑b‑e M b M′ e F y O 2‑y In this invention, the fluoride in the fluorinated coating layer reacts with lithium in the bulk material of the fluorinated cathode material to form a fluorinated cobalt lithium compound. Since the conductivity of the fluorinated compound is very low, coating with the fluorinated cobalt lithium compound significantly increases the impedance of the fluorinated cathode material in the battery, increasing the battery's internal resistance and sacrificing battery capacity. By simultaneously coating with the fluorinated coating layer and replenishing lithium, the conductivity of the fluorinated cathode material is significantly improved, thereby achieving the goal of increasing the capacity of the fluorinated cathode material and improving cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials technology, and more specifically, to fluorine-containing cathode materials, preparation methods, and applications. Background Technology

[0002] With technological advancements, new demands have been placed on the energy density and safety performance of lithium-ion batteries. Cathode materials, as a crucial component of lithium batteries, face even greater challenges. One method to improve energy density is to increase compaction density, but current compaction density is nearing its limit, leaving little room for further improvement. Another approach is to increase the charging cutoff voltage of lithium batteries, indirectly enhancing their energy density, which has become an important research direction in the industry.

[0003] As the cutoff voltage of lithium batteries increases, battery performance deteriorates significantly. This is primarily because the increased voltage leads to greater lithium insertion / extraction, resulting in increased volume deformation and stress accumulation. Furthermore, the layered cathode material surface is more prone to reactions with the electrolyte. These reactions manifest primarily in trace amounts of water in the electrolyte, residual alkali on the layered material surface, and the formation and deposition of inert substances from reactions within the electrolyte on the cathode material surface. These inert substances lack electrochemical activity, leading to a reduction in active material during cycling. The thickened battery interface also increases electronic conductivity and charge transfer resistance, further worsening cycle performance. Therefore, reducing side reactions at the cathode material interface is a necessary condition for improving the cutoff voltage.

[0004] Coating is a commonly used modification method for lithium-ion battery cathode materials. By forming a coating layer on the surface of the cathode material, the surface of the cathode material can be protected during cycling, reducing lithium loss caused by SEI film formation. However, the choice of coating components, as well as the uniformity of mixing, coating method, sintering temperature, and aeration, greatly affect the coating effect. Conventional coatings include electrochemically inert coatings, such as lithium-free stable oxides, fluorides, and fluoroates, which can coat the surface structure of lithium cobalt oxide, but there is a risk of reduced capacity. Electrochemically active coatings, such as lithium-containing cathodes, solid electrolytes, and conductive polymers, can coat the surface structure of lithium cobalt oxide, but there is a risk of cycle degradation.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide fluorine-containing cathode materials, preparation methods, and applications, thereby improving the capacity and cycle performance of cathode materials and suppressing gas generation.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a fluorine-containing cathode material, comprising a bulk material and a fluorine-containing coating layer coated on the bulk material, wherein the fluorine-containing coating layer comprises a fluorine-containing lithium cobalt compound, and the fluorine-containing cathode material has the chemical formula Li. 1+x (Ni (1-c-d) Co d Mn c ) 1-b-e M b M′ e F y O 2-y ;

[0009] in,

[0010] M is at least one of Ba, Ti, V, Nb, Cu, B, S, Sc, Ga, Zn, Mo, Si, and Sb;

[0011] M′ is at least one of La, Zr, Mg, Sr, Al, Y, W;

[0012] 0 <x≤0.2,0<b≤0.1,0≤c≤1,0<d≤1,0≤e≤0.2,0<y≤0.1。

[0013] In an optional implementation, 0.0005 <y≤0.005。

[0014] Secondly, the present invention provides a method for preparing the fluorine-containing cathode material described in the foregoing embodiments, comprising:

[0015] The bulk material is prepared by calcining and crushing a mixture of a lithium source, a precursor, a compound containing M, and a compound containing M′ to obtain the bulk material.

[0016] A coating layer is prepared to allow the fluorine-containing slurry to adhere to the surface of the bulk material, followed by sintering and pulverization to obtain the fluorine-containing cathode material.

[0017] In an optional embodiment, the fluorinated component in the fluorinated slurry includes at least two of aluminum fluoride, magnesium fluoride, zirconium fluoride, lithium fluoride, yttrium fluoride, lanthanum fluoride, strontium fluoride, and tungsten fluoride.

[0018] And / or, the mass ratio of fluorine-containing components to water in the fluorine-containing slurry is 1:(5-50);

[0019] And / or, the particle size of the fluorinated component in the fluorinated slurry is 0.001 μm to 20 μm.

[0020] In an optional embodiment, the fluorinated component in the fluorinated slurry includes a first fluorinated component and a second fluorinated component, wherein the first fluorinated component is lithium fluoride, and the second fluorinated component is at least one selected from aluminum fluoride, magnesium fluoride, zirconium fluoride, yttrium fluoride, lanthanum fluoride, strontium fluoride, and tungsten fluoride.

[0021] In an optional embodiment, the step of preparing the bulk material satisfies at least one of the following (a) to (e):

[0022] (a) The lithium source is at least one of lithium hydroxide, lithium carbonate and lithium oxalate;

[0023] (b) The precursor is an oxide, hydroxide, carbonate or hydroxy oxide containing at least one of nickel, cobalt and manganese;

[0024] (c) The M-containing compound is at least one of an M-containing oxide, hydroxide, acetate, and carbonate; the M′-containing compound is at least one of an M′-containing oxide, hydroxide, acetate, and carbonate.

[0025] (d) The calcination step is performed at a temperature of 850℃~1100℃ for 6h~12h.

[0026] (e) The crushing step is carried out in a micro-nano pulverizer with a crushing power of 140W to 160W, a crushing time of 14min to 16min, and a crushing atmosphere of air.

[0027] In an optional embodiment, in the step of preparing the coating layer, the fluorinated slurry is sprayed onto the bulk material and then sintered.

[0028] And / or, the sintering temperature is 300℃~900℃, and the sintering time is 3h~8h.

[0029] Thirdly, the present invention provides a positive electrode sheet, comprising the positive electrode material described in the foregoing embodiments or the positive electrode material prepared by any one of the methods described in the foregoing embodiments.

[0030] Fourthly, the present invention provides a lithium-ion battery, including the positive electrode sheet described in the foregoing embodiments.

[0031] Fifthly, the present invention provides an electrical device including the lithium-ion battery described in the foregoing embodiments.

[0032] The present invention has the following beneficial effects:

[0033] In this invention, the fluoride in the fluorinated coating layer reacts with lithium in the bulk material of the fluorinated cathode material to form a fluorinated cobalt lithium compound. Since the conductivity of the fluorinated compound is very low, coating with the fluorinated cobalt lithium compound significantly increases the impedance of the fluorinated cathode material in the battery, increasing the battery's internal resistance and sacrificing battery capacity. By simultaneously coating with the fluorinated coating layer and adding lithium, the conductivity of the fluorinated cathode material is significantly improved, thereby achieving the goal of increasing the capacity of the fluorinated cathode material and improving its cycle performance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a SEM image of the fluorine-containing cathode material of Example 1 of the present invention;

[0036] Figure 2 This is a SEM image of the fluorine-containing cathode material in Example 5 of the present invention;

[0037] Figure 3 This is a SEM image of the uncoated positive electrode material in Comparative Example 9 of this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] This invention provides a fluorine-containing cathode material, comprising a bulk material and a fluorine-containing coating layer covering the bulk material, wherein the fluorine-containing coating layer comprises a fluorine-containing lithium cobalt compound, and the fluorine-containing cathode material has the chemical formula Li. 1+x (Ni (1-c-d) Co d Mn c ) 1-b-e M b M′ e F y O 2-y ;

[0040] in,

[0041] M is at least one of Ba, Ti, V, Nb, Cu, B, S, Sc, Ga, Zn, Mo, Si, and Sb;

[0042] M' is at least one of La, Zr, Mg, Sr, Al, Y, W;

[0043] 0 < x ≤ 0.2, 0 < b ≤ 0.1, 0 ≤ c ≤ 1, 0 < d ≤ 1, 0 ≤ e ≤ 0.2, 0 < y ≤ 0.1.

[0044] In the embodiments of the present invention, the doping elements M and M' need to be doped in small amounts. Among them, b can be 0.02, 0.04, 0.05, 0.08, 0.1 or any value satisfying 0 < b ≤ 0.1, e can be 0, 0.05, 0.1, 0.15, 0.2 or any value satisfying 0 ≤ e ≤ 0.2, and y can be 0.02, 0.04, 0.05, 0.08, 0.1 or any value satisfying 0 < y ≤ 0.1. By introducing a fluorine-containing coating layer while doping elements, the synergistic effect of various elements is beneficial to suppressing the interfacial side reactions of the fluorine-containing cathode material at high voltages and improving the interfacial stability of the fluorine-containing cathode material.

[0045] In the embodiments of the present invention, x can be 0.05, 0.1, 0.15, 0.2 or any value satisfying 0 < x ≤ 0.2. When the fluorine-containing cathode material is supplemented with lithium while introducing the fluorine-containing coating layer, fluorine occupies the oxygen position, improving the interfacial stability of the fluorine-containing cathode material such as high delithiated lithium cobaltate, reducing the grain boundary dislocations and internal stresses in the high delithiated state, and further reducing the interfacial charge transfer impedance between the fluorine-containing cathode material and the electrolyte. Therefore, it is beneficial to the electrochemical stability of the fluorine-containing cathode material and solves the problems such as cycling and capacity faced in the development of high-voltage materials.

[0046] In the present invention, the fluoride in the fluorine-containing coating layer reacts with lithium in the bulk material of the fluorine-containing cathode material to form a fluorine-containing cobalt-lithium compound. Since the conductivity of the fluorine-containing compound is very low, coating with the fluorine-containing cobalt-lithium compound will significantly increase the impedance of the fluorine-containing cathode material in the battery, increase the internal resistance of the battery, and sacrifice the battery capacity. Supplying lithium while coating with the fluorine-containing coating layer significantly improves the conductivity of the fluorine-containing cathode material, achieving the purpose of increasing the capacity of the fluorine-containing cathode material and improving the cycling performance.

[0047] In some embodiments, 0.0005 < y ≤ 0.005, specifically, it can be 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005 or any value between 0.0005 < y ≤ 0.005. Introducing a small amount of fluorine to replace oxygen inhibits the oxygen charge compensation under high delithiation, can reduce the interfacial side reactions, improve the stability, improve the gas generation, and improve the cycling; introducing more fluorine leads to the growth of crystal orientation and the deterioration of electrical properties such as capacity, and the total amount of fluorine introduced needs to be controlled;

[0048] The embodiments of the present invention also provide a preparation method for the fluorine-containing cathode material described in the foregoing embodiments, including:

[0049] The bulk material is prepared by calcining and crushing a mixture of a lithium source, a precursor, a compound containing M, and a compound containing M′ to obtain the bulk material.

[0050] A coating layer is prepared to allow the fluorine-containing slurry to adhere to the surface of the bulk material, followed by sintering and pulverization to obtain the fluorine-containing cathode material.

[0051] In this embodiment of the invention, a bulk material is first prepared. In preparing the bulk material, a compound containing M and / or M′ is added to achieve bulk doping of M and / or M′ elements. This improves the electronic conductivity and charge transfer capability of the fluorine-containing cathode material and suppresses the irreversible phase transition of the fluorine-containing cathode material under high pressure. Next, a fluorine-containing slurry is coated onto the surface of the bulk material, and after sintering, a fluorine-containing cathode material is obtained. It should be noted that the fluorine-containing component in the fluorine-containing slurry contains not only fluorine but also metal ions such as M′. Therefore, when preparing the bulk material, the amount of M′ can be appropriately reduced to obtain a fluorine-containing cathode material that meets the specified chemical formula after coating.

[0052] In some embodiments, the fluorinated slurry contains at least two of the following fluorinated components: aluminum fluoride, magnesium fluoride, zirconium fluoride, lithium fluoride, yttrium fluoride, lanthanum fluoride, strontium fluoride, and tungsten fluoride. In addition to fluorine, the fluorinated components also contain aluminum, magnesium, zirconium, lithium, yttrium, lanthanum, strontium, and tungsten, which is beneficial to improving the performance of the fluorinated cathode material.

[0053] In some embodiments, the mass ratio of the fluorinated component to water in the fluorinated slurry is 1:(5-50), specifically, it can be any value between 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, or 1:(5-50). An appropriate concentration of fluorinated slurry is beneficial for the relatively uniform distribution of fluorine on the surface of the substrate material. If the concentration of the fluorinated slurry is too low, the subsequent water removal operation will consume too much energy; if the concentration of the fluorinated slurry is too high, the uniformity of fluorine distribution will decrease. The fluorinated slurry is obtained by adding fluorinated component powder to water, such as deionized water, in a certain proportion, followed by stirring until homogeneous. The stirring time can be from 10 min to 300 min.

[0054] In some embodiments, the particle size of the fluorinated component in the fluorinated slurry is 0.001 μm to 20 μm, specifically, it can be any value between 0.001 μm, 0.01 μm, 0.1 μm, 1 μm, 5 μm, 10 μm, 20 μm, or 0.001 μm to 20 μm. The particle size of the fluorinated component affects the performance of the fluorinated cathode material; when the particle size of the fluorinated component is within the above range, the fluorinated cathode material exhibits better performance.

[0055] In some embodiments, the fluorinated slurry contains a first fluorinated component and a second fluorinated component, wherein the first fluorinated component is lithium fluoride, and the second fluorinated component is at least one selected from aluminum fluoride, magnesium fluoride, zirconium fluoride, yttrium fluoride, lanthanum fluoride, strontium fluoride, and tungsten fluoride.

[0056] Using highly active lithium replenishing agents such as lithium carbonate and lithium hydroxide for lithium replenishment and coating can easily damage the interface, leading to deterioration in cycle and storage performance. Furthermore, these highly active lithium replenishing agents are prone to volatility, resulting in uneven lithium replenishment and hindering the improvement of lithium replenishment efficiency. In this embodiment of the invention, lithium fluoride is used as the lithium replenishing agent. Lithium fluoride has better stability and a superior lithium replenishment effect, while also introducing stable fluorine elements, which is beneficial for improving cycle gas production. By using a first fluorine-containing component and a second fluorine-containing component, other metal elements such as aluminum, magnesium, zirconium, lithium, yttrium, lanthanum, strontium, and tungsten are added simultaneously for lithium and fluorine replenishment, allowing for the control of total fluorine and other coating element amounts, which is beneficial for improving the overall performance of the battery.

[0057] In some embodiments, the lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium oxalate, with a wide range of raw material options and low cost.

[0058] In some embodiments, the precursor is an oxide, hydroxide, carbonate, or hydroxyoxide containing at least one of nickel, cobalt, and manganese, which facilitates preparation.

[0059] In some embodiments, the M-containing compound is at least one of an M-containing oxide, hydroxide, acetate, and carbonate; the M′-containing compound is at least one of an M′-containing oxide, hydroxide, acetate, and carbonate, with a wide range of raw material options and low cost.

[0060] In some embodiments, the calcination step is performed at a temperature of 850°C to 1100°C, specifically at 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, or any value between 850°C and 1100°C, for a time of 6 hours to 12 hours, specifically at 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or any value between 6 hours and 12 hours. At a temperature of 850°C to 1100°C, M or M′ elements can be effectively doped into the bulk material, which is beneficial to the electrochemical capacity of the bulk material.

[0061] In some embodiments, the crushing step is carried out in a micro-nano pulverizer with a crushing power of 140W to 160W, a crushing time of 14min to 16min, and an air atmosphere. The crushing yields bulk material powder with a particle size of less than 200μm.

[0062] In some embodiments, during the preparation of the coating layer step, the fluorinated slurry is sprayed onto the base material and then sintered. To improve the uniformity of the coating, the device holding the base material is rolled or stirred during the spraying process.

[0063] In some embodiments, the preparation of the coating layer can also be carried out using a solid-state method, in which the fluorinated component and the bulk material are uniformly mixed so that the fluorinated component adheres to the surface of the bulk material, and then sintered. It should be noted that in the solid-state method, only a small amount of water or alcohol needs to be added to the fluorinated slurry for dispersion.

[0064] In some embodiments, the sintering temperature is 300℃ to 900℃, specifically 300℃, 500℃, 700℃, 900℃, or any value between 300℃ and 900℃, and the sintering time is 3h to 8h, specifically 3h, 4h, 5h, 6h, 7h, 8h, or any value between 3h and 8h. Coating sintering at a temperature of 300 to 900℃ can effectively coat the M′ element onto the material surface. In the method for preparing the fluorine-containing cathode material, the calcination can be carried out in an oxygen atmosphere.

[0065] The present invention also provides a positive electrode sheet, comprising the positive electrode material described in the foregoing embodiments or the positive electrode material prepared by any one of the methods described in the foregoing embodiments.

[0066] In the positive electrode sheet of the present invention, the positive electrode film layer typically comprises the aforementioned positive electrode material, as well as optionally a binder and optionally a conductive agent, and is typically formed by coating a positive electrode slurry and then drying and cold pressing it. The positive electrode slurry is typically formed by dispersing the aforementioned positive electrode material, optionally a conductive agent, and optionally a binder in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP).

[0067] In some optional embodiments, the positive electrode film may contain 70 wt% to 97 wt% of positive electrode material, based on the total weight of the positive electrode film. Optionally, the weight percentage of the positive electrode material in the positive electrode film is 85% to 97%, 90% to 97%, or 95% to 97%. By adjusting the proportion of positive electrode material in the positive electrode film, the energy density and cycle life of the lithium-ion battery can be further improved.

[0068] In some embodiments, the binder for the positive electrode film may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and modified polymers thereof.

[0069] Conductive agents can improve the electronic conductivity of the positive electrode film. In some optional embodiments, the positive electrode film may contain 2 wt% to 20 wt% of conductive agent based on the total weight of the positive electrode film. Optionally, the conductive agent may account for 2% to 10% or 2% to 5% of the weight of the positive electrode film.

[0070] In some embodiments, the conductive agent of the positive electrode film may include one or more of superconducting carbon, carbon black (such as SuperP, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0071] It should be noted that the composition or parameters of each positive electrode film layer given in this invention refer to the composition or parameter range of the single-sided film layer of the positive electrode current collector. When the positive electrode film layer is disposed on two opposite surfaces of the positive electrode current collector, if the composition or parameters of the positive electrode film layer on either surface satisfy this invention, it is considered to fall within the protection scope of this invention.

[0072] The present invention provides a lithium-ion battery, including the positive electrode sheet described in the foregoing embodiments, and further including a negative electrode sheet, an electrolyte and a separator.

[0073] [Negative electrode plate]

[0074] The negative electrode sheet of the present invention includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0075] As an example, the negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is laminated on either or both of the two opposite surfaces of the negative electrode current collector.

[0076] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0077] In the negative electrode sheet of this invention, the negative electrode film layer typically comprises a negative electrode active material and optionally a binder, optionally a conductive agent, and other optional additives. It is usually formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optionally a conductive agent, optionally a binder, and optionally additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0078] In some embodiments, the negative electrode active material may include one or more of artificial graphite, natural graphite, silicon-based materials, and tin-based materials. Optionally, the negative electrode active material includes one or more of artificial graphite and natural graphite. Optionally, the negative electrode active material includes artificial graphite.

[0079] In some embodiments, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., SuperP, acetylene black, Ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments, the adhesive may include one or more of styrene-butadiene rubber (SBR), waterborne acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0081] In some embodiments, other optional additives include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0082] [Electrolytes]

[0083] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This invention does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be selected from electrolyte solutions. The electrolyte solution includes an electrolyte salt and a solvent.

[0084] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate 2 (LiPO2F), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0085] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0086] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0087] [Isolation membrane]

[0088] A separator is disposed between the positive and negative electrode plates, serving as a separator. The lithium-ion battery of this invention does not have particular limitations on the type of separator; any known porous separator used in lithium-ion batteries can be selected. For example, the separator can be selected from glass fiber film, non-woven fabric film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and one or more multilayer composite films comprising one or more of these materials.

[0089] Positive electrode, negative electrode, and separator can be stacked or wound to form an electrode assembly, with the separator positioned between the positive and negative electrode to provide isolation. The electrode assembly is then placed in an outer package, filled with electrolyte, and sealed to obtain a lithium-ion battery.

[0090] The outer packaging of a lithium-ion battery is used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of a lithium-ion battery can also be a pouch, such as a pouch. The material of the pouch can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0091] This invention does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0092] In some embodiments, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0093] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0094] The present invention provides an electrical device, including the lithium-ion battery described in the foregoing embodiments.

[0095] This invention also provides an electrical device, comprising at least one of the lithium-ion battery, battery module, or battery pack described in this invention. The lithium-ion battery, battery module, or battery pack can be used as a power source for the device or as an energy storage unit. The device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. The device can select the lithium-ion battery, battery module, or battery pack according to its usage requirements.

[0096] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0097] Example 1

[0098] This embodiment provides a method for preparing a fluorine-containing cathode material, including the following steps:

[0099] S1. Preparation of modified lithium cobalt oxide powder:

[0100] Lithium carbonate, cobalt tetroxide, titanium dioxide, and aluminum oxide were mixed evenly and then sintered at 1030℃ for 10 hours. The resulting product was pulverized to obtain modified lithium cobalt oxide powder. The amounts of lithium carbonate, cobalt tetroxide, titanium dioxide, and aluminum oxide were 0.5 mol, 0.327 mol, 0.0035 mol, and 0.01 mol, respectively.

[0101] S2. Preparation of fluorinated slurry:

[0102] Aluminum fluoride, lithium fluoride and deionized water are mixed uniformly at a mass ratio of 1:50 to obtain a fluorinated slurry, wherein the total mass of aluminum fluoride and lithium fluoride accounts for 0.04% of the mass of modified lithium cobalt oxide, and the molar ratio of aluminum to lithium is 1:1.

[0103] S3. Preparation of fluorine-containing cathode materials:

[0104] Modified lithium cobalt oxide powder was placed in a drum rotating at 1300 r / min, and a fluorinated slurry was sprayed onto the modified lithium cobalt oxide powder. The mixing time was 9 min. Then, the mixture was placed in a box furnace and sintered at 450℃ for 4 h. The resulting blocky product was pulverized and passed through a 400-mesh sieve to obtain the fluorinated cathode material. SEM images are shown below. Figure 1 As shown, its structural formula is: Li 1.0004 Co 0.98 Ti 0.0035 Al 0.0204 O 1.9986 F 0.0014 .

[0105] Example 2

[0106] This embodiment provides a method for preparing a fluorine-containing cathode material, including the following steps:

[0107] S1. Preparation of modified nickel-cobalt-manganese powder:

[0108] Lithium carbonate, nickel cobalt manganese hydroxide, titanium dioxide, and aluminum oxide were mixed evenly and then sintered at 950°C for 8 hours. The resulting product was crushed to obtain modified nickel cobalt manganese powder. The chemical formula of the nickel cobalt manganese hydroxide is Ni. 0.6 Mn 0.2 Co 0.2 (OH)2; wherein the amounts of lithium carbonate, nickel cobalt manganese hydroxide, titanium dioxide, and aluminum oxide are 0.5 mol, 1.0 mol, 0.003 mol, and 0.005 mol, respectively;

[0109] S2. Preparation of fluorinated slurry:

[0110] Lithium fluoride, aluminum fluoride, and magnesium fluoride are mixed evenly, wherein the total mass of magnesium fluoride and aluminum fluoride accounts for 0.04% of the mass of the modified nickel cobalt manganese powder, and the molar ratio of magnesium to aluminum is 1:1. The mass of lithium fluoride accounts for 0.03% of the mass of the modified nickel cobalt manganese powder. Fluorine-containing compound powder is added to deionized water, and the mass ratio of fluorine-containing compound powder to deionized water is 1:15. The mixture is stirred evenly to obtain a fluorine-containing slurry.

[0111] S3 is used to prepare fluorine-containing cathode materials:

[0112] Modified nickel-cobalt-manganese powder was placed in a drum rotating at 1300 r / min, and a fluorinated slurry was sprayed onto the modified nickel-cobalt-manganese powder. The mixing time was 9 min. Then, the mixture was placed in a box furnace and sintered at 300℃ for 8 h. The resulting blocky product was pulverized and passed through a 400-mesh sieve to obtain the fluorinated cathode material, whose structural formula is: Li 1.002 Ni 0.599 Co 0.199 Mn 0.199 Ti 0.003 Al 0.0102 Mg 0.0002 O 1.999 F 0.001 .

[0113] Example 3

[0114] This embodiment provides a method for preparing a fluorine-containing cathode material, including the following steps:

[0115] S1. Preparation of modified lithium cobalt oxide powder:

[0116] Lithium carbonate, cobalt tetroxide, titanium dioxide, and aluminum oxide were mixed evenly and then sintered at 800℃ for 12 hours. The resulting product was crushed to obtain modified lithium cobalt oxide powder, wherein the amounts of lithium carbonate, cobalt tetroxide, titanium dioxide, and aluminum oxide were 0.5 mol, 0.327 mol, 0.004 mol, and 0.008 mol, respectively.

[0117] S2. Preparation of fluorinated slurry:

[0118] Lithium fluoride, aluminum fluoride, and zirconium fluoride are mixed evenly, wherein the total mass of zirconium fluoride and aluminum fluoride accounts for 0.04% of the mass of modified lithium cobalt oxide powder, and the zirconium-aluminum molar ratio is 1:1. The mass of lithium fluoride accounts for 0.03% of the mass of modified lithium cobalt oxide powder. Fluorine-containing compound powder is added to deionized water, and the mass ratio of fluorine-containing compound powder to deionized water is 1:50. The mixture is stirred evenly to obtain fluorine-containing slurry.

[0119] S3. Preparation of fluorine-containing cathode materials:

[0120] Modified lithium cobalt oxide powder was placed in a drum rotating at 1300 r / min, and a fluorinated slurry was sprayed onto the modified lithium cobalt oxide powder. The mixing time was 12 min. Then, the mixture was placed in a box furnace and sintered at 800℃ for 3 h. The resulting blocky product was pulverized and passed through a 400-mesh sieve to obtain the fluorinated cathode material, whose structural formula is: Li 1.002 Co 0.98 Ti 0.004 Al 0.01612 Zr 0.0001 2O 1.9991 F 0.0009 .

[0121] Example 4

[0122] This embodiment provides a method for preparing a fluorine-containing cathode material, including the following steps:

[0123] S1. Preparation of modified lithium cobalt oxide powder:

[0124] Lithium carbonate, cobalt tetroxide, titanium dioxide, aluminum oxide, and lithium fluoride were mixed evenly and then sintered at 1030°C for 10 hours. The resulting product was crushed to obtain modified lithium cobalt oxide powder, wherein the amounts of lithium carbonate, cobalt tetroxide, titanium dioxide, aluminum oxide, and lithium fluoride were 0.5 mol, 0.334 mol, 0.002 mol, 0.012 mol, and 0.003 mol, respectively.

[0125] S2. Preparation of fluorinated slurry:

[0126] Lithium fluoride, aluminum fluoride, and yttrium fluoride are mixed evenly, wherein the total mass of yttrium fluoride, aluminum fluoride, and lithium fluoride accounts for 0.03% of the mass of modified lithium cobalt oxide powder, and the molar ratio of yttrium:aluminum:lithium is 1:1:1. Fluorine compound powder is added to deionized water, and the mass ratio of fluorine compound powder to deionized water is 1:5. The mixture is stirred evenly to obtain a fluorine-containing slurry.

[0127] S3. Preparation of fluorine-containing cathode materials:

[0128] Modified lithium cobalt oxide powder was placed in a drum rotating at 1200 r / min, and a fluorinated slurry was sprayed onto the modified lithium cobalt oxide powder. The mixing time was 9 min. Then, the mixture was placed in a box furnace and sintered at 450℃ for 7 h. The resulting blocky product was pulverized and sieved through a 400-mesh sieve to obtain the fluorinated cathode material, whose structural formula is: Li 1.0031 Co 1.002 Ti 0.002 Al 0.0241 Y 0.00015 F 0.0041 O 1.9959 .

[0129] Example 5

[0130] This embodiment provides a method for preparing a fluorine-containing cathode material, including the following steps:

[0131] S1. Preparation of modified lithium cobalt oxide powder:

[0132] Lithium carbonate, cobalt tetroxide, titanium dioxide, aluminum oxide, and lithium fluoride were mixed evenly and then sintered at 1025℃ for 10 hours. The resulting product was crushed to obtain modified lithium cobalt oxide powder, wherein the amounts of lithium carbonate, cobalt tetroxide, titanium dioxide, aluminum oxide, and lithium fluoride were 0.5 mol, 0.33 mol, 0.001 mol, 0.01 mol, and 0.002 mol, respectively.

[0133] S2. Preparation of fluorinated slurry:

[0134] S1: Mix lithium fluoride, lanthanum fluoride, and aluminum fluoride evenly, wherein the total mass of lanthanum fluoride, aluminum fluoride, and lithium fluoride accounts for 0.055% of the mass of modified lithium cobalt oxide powder, and the molar ratio of lanthanum:aluminum:lithium is 1:1:1. Add the resulting fluorinated compound powder to deionized water, wherein the mass ratio of fluorinated compound powder to deionized water is 1:5, and stir evenly to obtain fluorinated slurry.

[0135] S3. Preparation of fluorine-containing cathode materials:

[0136] Modified lithium cobalt oxide powder was placed in a drum rotating at 1100 r / min, and a fluorinated slurry was sprayed onto the modified lithium cobalt oxide powder. The mixing time was 9 min. Then, the mixture was placed in a box furnace and sintered at 450℃ for 7 h. The resulting blocky product was pulverized and sieved through a 400-mesh sieve to obtain the fluorinated cathode material. SEM images are shown below. Figure 2 As shown, its structural formula is: Li 1.002 Co 0.99 Ti 0.001 Al 0.0202 La 0.00018 F 0.00323 O 1.9967 .

[0137] Example 6

[0138] The main difference between this embodiment and Embodiment 5 is that lithium fluoride is replaced with magnesium fluoride in the preparation of the modified lithium cobalt oxide cathode material, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0139] Example 7

[0140] The main difference between this embodiment and Embodiment 5 is that lithium fluoride is replaced with yttrium fluoride in the preparation of the modified lithium cobalt oxide cathode material, and the total fluorine doping is increased by 2 times.

[0141] Example 8

[0142] The main difference between this embodiment and Example 5 is that lithium fluoride is replaced with lanthanum fluoride in the preparation of the modified lithium cobalt oxide cathode material, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0143] Example 9

[0144] The main difference between this embodiment and Example 5 is that lithium fluoride is replaced with an equimolar amount of zirconium oxide in the preparation of the fluorinated slurry.

[0145] Example 10

[0146] The main difference between this embodiment and Embodiment 5 is that lithium fluoride is replaced with magnesium fluoride in the preparation of the fluorinated slurry, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0147] Example 11

[0148] The main difference between this embodiment and Embodiment 5 is that lithium fluoride is replaced with zirconium fluoride in the preparation of the fluorinated slurry, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0149] Example 12

[0150] The main difference between this embodiment and Embodiment 5 is that aluminum fluoride is replaced with strontium fluoride in the preparation of the fluorinated slurry, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0151] Example 13

[0152] The main difference between this embodiment and Embodiment 5 is that aluminum fluoride is replaced with tungsten fluoride in the preparation of the fluorinated slurry, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0153] Example 14

[0154] The main difference between this embodiment and Example 5 is that aluminum fluoride is replaced with magnesium fluoride + aluminum fluoride in a molar ratio of 1:1 in the preparation of the fluorinated slurry, while keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0155] Comparative Example 1

[0156] The main difference between this comparative example and Example 1 is that lithium fluoride is not added in the preparation of the fluorinated slurry.

[0157] Comparative Example 2

[0158] The main difference between this comparative example and Example 2 is that lithium fluoride is not added in the preparation of the fluorinated slurry, thus keeping the molar amount of fluorine in the modified lithium cobalt oxide cathode material unchanged.

[0159] Comparative Example 3

[0160] The main difference between this comparative example and Example 1 is that titanium oxide and aluminum oxide are not added in the preparation of the modified lithium cobalt oxide cathode material, while the amounts of other raw materials remain unchanged.

[0161] Comparative Example 4

[0162] The main difference between this comparative example and Example 1 is that aluminum fluoride is not added in the preparation of the fluorinated slurry, while the amounts of other raw materials remain unchanged.

[0163] Comparative Example 5

[0164] The main difference between this comparative example and Example 5 is that lanthanum fluoride + alumina is not added in the preparation of the fluorinated slurry, while the amounts of other raw materials remain unchanged.

[0165] Comparative Example 6

[0166] The main difference between this comparative example and Example 5 is that lithium fluoride is not added in the preparation of the fluorinated slurry, while the amounts of other raw materials remain unchanged.

[0167] Comparative Example 7

[0168] The main difference between this comparative example and Example 5 is that the fluoride in the preparation of the fluorinated slurry is replaced by an oxide, while the total molar amount of lanthanum aluminum lithium remains unchanged.

[0169] Comparative Example 8

[0170] The main difference between this comparative example and Example 5 is that the fluoride content in the preparation of modified lithium cobalt oxide powder is increased by 1 time, while the fluoride content in the preparation of fluorine-containing slurry is increased by 2 times.

[0171] Comparative Example 9

[0172] The main difference between this comparative example and Example 1 is that steps S2 and S3 are omitted, and the SEM image of the cathode material is obtained as follows: Figure 3 As shown.

[0173] Example of effect 1

[0174] This embodiment provides a lithium battery. The fluorinated positive electrode materials obtained in the examples and comparative examples are used to prepare lithium batteries. The preparation method of the lithium battery is as follows: Fluorinated positive electrode material, polyvinylidene fluoride, and conductive carbon black are mixed evenly, wherein the mass ratio of fluorinated positive electrode material, polyvinylidene fluoride, and conductive carbon black is fluorinated positive electrode material: polyvinylidene fluoride: conductive carbon black = 90:5:5. NMP (N-methylpyrrolidone) is added to the resulting mixture, and the mixture is stirred to form a slurry. The slurry is coated onto aluminum foil and dried at 80°C to form a positive electrode sheet. The obtained positive electrode sheet, graphite, electrolyte, and separator are used as raw materials to wind and form a soft-pack battery.

[0175] The performance of the obtained pouch battery was tested using the following method:

[0176] (1) 45°C Cycle Test: At 45°C, the pouch cells prepared in Examples 1, 3-14, and Comparative Examples 1, 3-9 were charged with a constant current (CC) at a 1C rate until the voltage reached 4.48V (relative to Li), and the current was cut off at a 0.05C rate while maintaining the voltage at 4.48V in constant voltage mode (CV). The cells were then discharged with a constant current (CC) at a 1C rate until the discharge voltage reached 3.0V (relative to Li), and this cycle was repeated. Cycle capacity retention = (discharge capacity of the Nth cycle / discharge capacity of the first cycle) × 100%, where the test was stopped when the retention rate reached 80%. A 5-minute holding time was set after each charge / discharge cycle throughout the entire charge / discharge cycle.

[0177] In Example 2 and Comparative Example 2, the test voltage was 2.8–4.4 V. At 45°C, the pouch cell was charged with a constant current (CC) at a 1C rate until the voltage reached 4.40 V (relative to Li), and the current was cut off at a 0.05C rate while maintaining the voltage at 4.40 V in constant voltage mode (CV). The cell was then discharged with a constant current (CC) at a 1C rate until the discharge voltage reached 2.8 V (relative to Li), and this cycle was repeated. Cycle capacity retention was calculated as (discharge capacity of the Nth cycle / discharge capacity of the first cycle) × 100%, where the test was stopped when the retention reached 80%. A 5-minute hold-up time was set after each charge / discharge cycle throughout the entire charge / discharge cycle.

[0178] (2) Capacity test: The rate capacity of Examples 1, 3-14 and Comparative Examples 1 and 3-9 was tested at 25°C under the charge and discharge conditions of 4.48V / 0.2C; the rate capacity of Examples 2 and Comparative Examples 2 was tested under the charge and discharge conditions of 4.40V / 0.2C.

[0179] (3) Gas generation test: The cells are taken out at intervals in a cabinet at 70°C to measure the change in cell volume.

[0180] The test results are shown in Tables 1-3.

[0181] Table 1

[0182] 0.2C rate capacity 45% cycle retention Gas production volume change Example 1 187.3 600 laps 80% 60 days 3.1% Example 3 186.8 550 laps 80% 60 days 3.7% Example 4 186.6 570 laps 80% 60 days 3.6% Comparative Example 1 182.6 580 laps 80% 60 days 3.1% Comparative Example 3 186.1 420 laps 80% 60 days 6.5% Comparative Example 4 186.1 460 laps 80% 60 days 8.5% Comparative Example 9 186.6 230 out of 80% 60 days 20%

[0183] Analysis of Table 1 shows that Examples 1, 3, and 4, using a combination of lithium-containing fluorides and other elemental fluorides, improve the capacity, cycle life, and gas production of the fluorinated cathode material. Comparative Example 1, lacking lithium-containing fluoride coating, suffers from lower capacity due to lithium deficiency compared to Example 1. Comparative Example 3, lacking alumina and titanium oxide doping, exhibits structural instability and poor cycle performance. Comparative Example 3, lacking other fluoride coatings, also shows poor cycle performance and gas production. Nano-sized cobalt-lithium fluoride compounds delay or inhibit the oxygen reduction reaction between the electrolyte and the cathode material surface, reducing Co dissolution and improving the surface structural stability of cathode materials (such as lithium cobalt oxide) under high voltage and long-cycle conditions, thus improving cycle and gas production performance. Lithium-containing fluorides supplement lithium and enhance capacity. Comparative Example 9, without coating, shows significant deterioration in cycle life and gas production.

[0184] Table 2

[0185] 0.2C rate capacity 45℃ cycle retention rate Gas production volume change Example 2 198 600 days 80% 60 days 2.1% Comparative Example 2 191 570 days / 80% 60 days 2.7%

[0186] Analysis of Table 2 and comparison of Example 2 and Comparative Example 2 show that the capacity improvement after lithium supplementation is very significant when using NCM substrate.

[0187] Table 3

[0188]

[0189]

[0190] In Examples 5-6 / 8, adjusting the lithium-containing fluoride dopant to a lithium-free fluoride dopant resulted in minimal capacity changes, indicating that lithium-containing fluorides are suitable for coating to improve capacity. In Example 7, doubling the fluoride dopant resulted in capacity deterioration, indicating that adding more fluorine worsens capacity. In Examples 9-11, replacing the lithium-containing fluoride with a lithium-free fluoride reduced capacity. Examples 12-14 show that changing other fluorides has little impact on overall performance. Comparative Example 5 shows that coating without lanthanum fluoride or aluminum fluoride resulted in slight deterioration in gas production during cycling. Comparative Examples 6-8 show that low capacity without lithium replenishment, deterioration in gas production and cycling without fluoride addition, and significant performance degradation with large amounts of fluoride addition.

[0191] In summary, the embodiments of the present invention introduce fluorine-containing cathode materials to replace oxygen, and fluorine has a good binding ability with cobalt, which inhibits the release of oxygen and greatly improves the phase transition resistance of fluorine-containing cathode materials; the introduction of fluorine and lithium improves cycle life and increases capacity, thereby improving the structural stability of delithiated lithium cobalt oxide under the premise that the total fluorine content is controllable; the large amount of fluorine introduced changes the crystal structure, leading to crystal orientation growth and weakened stability.

[0192] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluorine-containing cathode material, characterized in that, The cathode material comprises a bulk material and a fluorinated coating layer covering the bulk material, wherein the fluorinated coating layer comprises a fluorinated cobalt lithium compound, and the chemical formula of the fluorinated cathode material is Li. 1+x (Ni) (1-c-d) Co d Mn c ) 1-b-e M b M′ e F y O 2-y ; in, M is at least one of Ba, Ti, V, Nb, Cu, B, S, Sc, Ga, Zn, Mo, Si, and Sb; M′ is at least one of La, Zr, Mg, Sr, Al, Y, and W; 0 <x≤0.2,0<b≤0.1,0≤c≤1,0<d≤1,0≤e≤0.2,0.0005<y≤0.005; The preparation method of the fluorine-containing cathode material includes: The bulk material is prepared by calcining and crushing a mixture of a lithium source, a precursor, a compound containing M, and a compound containing M′ to obtain the bulk material. A coating layer is prepared by adhering a fluorine-containing slurry to the surface of the base material, followed by sintering and pulverization to obtain the fluorine-containing cathode material; in the step of preparing the coating layer, the fluorine-containing slurry is sprayed onto the base material, followed by sintering. The fluorinated slurry contains a first fluorinated component and a second fluorinated component. The first fluorinated component is lithium fluoride, and the second fluorinated component is at least one of aluminum fluoride, magnesium fluoride, zirconium fluoride, yttrium fluoride, lanthanum fluoride, strontium fluoride, and tungsten fluoride. The mass ratio of the fluorinated component to water in the fluorinated slurry is 1:(5~50), and the particle size of the fluorinated component in the fluorinated slurry is 0.001μm~20μm.

2. The fluorine-containing cathode material according to claim 1, characterized in that, The step of preparing the bulk material satisfies at least one of the following (a) to (e): (a) The lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium oxalate; (b) The precursor is an oxide, hydroxide, carbonate or hydroxy oxide containing at least one of nickel, cobalt and manganese; (c) The M-containing compound is at least one of an M-containing oxide, hydroxide, acetate, and carbonate; the M′-containing compound is at least one of an M′-containing oxide, hydroxide, acetate, and carbonate. (d) The calcination step is performed at a temperature of 850℃~1100℃ for 6h~12h; (e) The crushing step is carried out in a micro-nano pulverizer with a crushing power of 140W~160W, a crushing time of 14 min~16 min, and a crushing atmosphere of air.

3. The fluorine-containing cathode material according to claim 1, characterized in that, The sintering temperature is 300℃~900℃, and the sintering time is 3h~8h.

4. A positive electrode sheet, characterized in that, Includes the cathode material as described in any one of claims 1-3.

5. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 4.

6. An electrical-related device, characterized in that, Including the lithium-ion battery as described in claim 5.

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