Modified layered oxide positive electrode material, preparation method, application and battery

Abstract

The invention discloses a modified layered oxide positive electrode material, a preparation method, application and a battery. The preparation method comprises the following steps: a method I: carrying out mixed reaction on a mixed solution containing a layered oxide positive electrode material and a lithium ion conductor salt, carrying out solid-liquid separation, and calcining; or, the method II comprises the following steps: carrying out solvothermal reaction on the mixed solution containing the layered oxide positive electrode material and the lithium ion conductor salt, and then calcining, or the third method comprises the following steps: carrying out mixed reaction on a mixed solution containing the layered oxide positive electrode material and the lithium ion conductor salt, evaporating the solvent to dryness, and calcining. The modified layered oxide positive electrode material prepared by the invention has excellent electrochemical performance, especially has relatively good long-cycle stability, the coating layer has relatively good uniformity and compactness, and the preparation method is simple and low in cost.

Description

Technical Field

[0001] This invention specifically relates to a modified layered oxide cathode material, its preparation method, applications, and batteries. Background Technology

[0002] With the increasing demand for efficient and clean alternative energy, lithium-ion batteries have attracted significant attention due to their high energy density. Layered oxide cathode materials, with their high specific capacity and high energy density, have become a research hotspot in lithium-ion battery cathode materials. Traditional layered oxide cathode materials generally exhibit a polycrystalline structure, where numerous nanoscale primary particles aggregate to form micron-sized secondary particles. While this structure is beneficial for increasing compaction density, it contains numerous grain boundaries, which can trigger a series of adverse effects during charge and discharge. Structural instability caused by grain boundary defects, cycle capacity decay, and interfacial side reactions still severely limit their practical application.

[0003] Single-crystal materials refer to cathode particles composed of independent single grains with sizes in the micrometer range. These grains do not contain the numerous grain boundaries common in polycrystalline materials, thus effectively avoiding crack propagation and particle pulverization caused by grain boundary mismatch and stress concentration between grains during charging and discharging. However, despite the many advantages exhibited by single-crystal cathode materials, they still face a series of technical challenges that need to be overcome. Due to the larger size of single-crystal particles, the lithium-ion diffusion path within them is significantly longer compared to nanoscale polycrystalline primary particles. In actual cycling, this easily leads to uneven lithium concentration distribution within the crystal, inducing local stress accumulation and forming uneven lattice strain. Furthermore, under high-voltage operating conditions, layered structures often undergo drastic anisotropic lattice expansion and contraction, thereby inducing microcracks within the single-crystal particles. These microcracks not only weaken structural integrity but also accelerate electrolyte penetration and side reactions, ultimately leading to severe degradation of the material surface and interface, and rapid capacity decay. Finally, although single-crystal materials theoretically possess a more stable structure, structural reconstruction inevitably occurs on their surfaces during synthesis and electrochemical cycling, especially under high voltage or overcharge conditions. This can easily lead to phase transitions induced by Li / TM cation exchange, forming irreversible structures such as spinel or rock salt phases. These surface structural transformations are typically accompanied by the formation of electrochemically inert phases, further increasing interfacial impedance and reducing overall battery performance.

[0004] Therefore, although high-voltage single-crystal layered oxide cathode materials have demonstrated significant advantages in improving the cycle life and thermal stability of lithium-ion batteries due to their excellent structural stability and high compaction density, their surface chemical stability still faces considerable challenges. Surface coating modification strategies have been widely used to mitigate interfacial side reactions and improve material stability and electrochemical performance. However, while surface coating can improve the cycle life and high-temperature performance of cathode materials to some extent, traditional surface coating methods (such as mechanical ball milling combined with solid-state sintering) rely on physical mixing, leading to weakened interfacial bonding between the coating layer and the substrate. Subsequent heat treatment easily results in discontinuous modification layers with uneven thickness and island-like distribution. Such coating layers are prone to peeling during long-term electrochemical cycling, not only weakening the modification effect but also significantly increasing interfacial impedance. Therefore, developing coating layers with uniform structure, controllable thickness, and high compatibility with high-voltage layered oxides is of great significance for improving the electrochemical performance of high-voltage layered oxide materials. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of existing high-voltage layered oxide cathode materials, such as complex coating processes, uncontrollable coating, and poor uniformity and density of the coating layer. This invention provides a modified layered oxide cathode material, its preparation method, applications, and batteries. The modified layered oxide cathode material prepared by this invention exhibits excellent electrochemical performance, especially good long-cycle stability, and the coating layer has good uniformity and density. Furthermore, the preparation method is simple and low-cost.

[0006] This invention targets layered oxide lithium-ion battery cathode materials (such as LiCoO2 and LiNi) under high voltage. x Co γ Mn 1-x- y O2, LiNi x Co γ Al 1-x-y The key challenges facing O2 include severe oxygen evolution, unfavorable structural phase transitions, and electrode / electrolyte interface instability. These challenges are addressed by mixing or solvothermally reacting lithium-ion conductor salt solutions with the cathode material to construct a coherent double-coated structure on the cathode material, consisting of a subsurface perovskite reconstruction layer and an outer surface lithium-ion conductor layer. Specifically, this involves mixing layered oxide cathode materials with a lithium-ion conductor layer in solution. 0 High-valence transition metal ions with electronic configurations (such as La) 3+ Ti 4+ (etc.) and anions (such as F) - PO4 2-The mixture of lithium-ion conductor salts, due to the presence of numerous unsaturated bonds (such as metal-oxygen bonds) and defect sites (such as surface hydroxyl groups and lattice vacancies) on the surface of the layered oxide cathode material, exhibits strong chemical activity. Therefore, when d in the solution... 0 When high-valence transition metal ions with specific electronic configurations approach, they can be adsorbed onto the material surface through coordination or electrostatic attraction. On the other hand, existing metal ions on the material surface may undergo topological exchange with the adsorbed high-valence metal ions, forming a TMCoO composition on the subsurface after annealing. 3-δ (TM is d) 0 In perovskite structures of high-valence transition metals (such as La, Gd, or Yb), topological exchange processes drive atomic-level substitution between ions in the coating layer and those on the substrate surface, resulting in a strong chemical bond and a tightly bound interface with lattice coherence between the coating layer and the substrate. Conversely, anions in lithium-ion conductor salts can combine with lithium ions to form lithium fluoride, lithium phosphate, etc. These substances, along with the lithium-ion conductor salt, coat the outer surface of the cathode material, forming a lithium-ion conductor coating layer. This perovskite + lithium-ion conductor dual coating layer exhibits high lithium-ion conductivity and low oxygen-ion conductivity, effectively stabilizing high-valence oxygen and significantly improving the electrochemical performance of layered oxide cathode materials under high voltage.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0008] This invention provides a method for preparing a modified layered oxide cathode material, comprising the following steps:

[0009] Method 1: Mix and react a mixture containing layered oxide cathode material and lithium-ion conductor salt, separate the solid and liquid phases, and then calcine the mixture to obtain the modified layered oxide cathode material.

[0010] Alternatively, Method 2: After subjecting the mixture containing layered oxide cathode material and lithium-ion conductor salt to a solvothermal reaction, it is then calcined to obtain the modified layered oxide cathode material.

[0011] Alternatively, method three: mix and react a mixture containing layered oxide cathode material and lithium-ion conductor salt, then evaporate the solvent and calcine to obtain the modified layered oxide cathode material.

[0012] In this invention, the layered oxide cathode material is preferably one or more of lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), and nickel cobalt aluminum ternary cathode material (NCA), and more preferably one or more of single-crystal lithium nickel cobalt manganese oxide, single-crystal lithium cobalt oxide, and single-crystal nickel cobalt aluminum ternary cathode material.

[0013] The chemical formula of the lithium nickel cobalt manganese oxide can be LiNi. x Coy Mn 1-x-y O2, where 0 < x < 1 and 0 < y < 1. In the chemical formula of the lithium nickel cobalt manganese oxide, preferably, 0.8 ≤ x < 1.

[0014] Among them, the chemical formula of the nickel cobalt aluminum ternary cathode material can be LiNi a Co b Al 1-a-b O2, where 0 < a < 1 and 0 < b < 1. In the chemical formula of the nickel cobalt aluminum ternary cathode material, preferably, 0.8 ≤ a < 1.

[0015] Among them, the single crystal lithium nickel cobalt manganese oxide and the single crystal lithium cobalt oxide can be prepared by themselves or obtained from conventional commercial sources.

[0016] In some specific embodiments, the layered oxide cathode material is a single crystal high nickel ternary cathode material LiNi 0.92 Co 0.05 Mn 0.03 O2 or single crystal lithium cobalt oxide.

[0017] In the present invention, the chemical formula of the lithium ion conductor salt can be Li a [M(PO4) y F z , where M is a high-valence metal ion with a d0 configuration, 0 ≤ y ≤ 2, 0 ≤ z ≤ 6, and y and z cannot be 0 at the same time.

[0018] Among them, in the chemical formula of the lithium ion conductor salt, the value of a can be determined according to the sum of the valences of each ion being 0 when the types of metal M, the values of y and z are determined. Preferably, 0.5 ≤ a ≤ 4, more preferably, 1 ≤ a ≤ 3. For example, a is 1, 2 or 3.

[0019] Among them, in the chemical formula of the lithium ion conductor salt, M is preferably one or more of 4+ Ti 3+ La 3+ Yb 3+ Gd.

[0020] Among them, in the chemical formula of the lithium ion conductor salt, y is, for example, 1 or 2.

[0021] Among them, in the chemical formula of the lithium ion conductor salt, z is, for example, 1, 2, 3, 4, 5 or 6.

[0022] In this invention, the lithium-ion conductor salt preferably includes one or more of lithium hexafluorotitanate (Li2TiF6), lithium hexafluorolanthanum oxide (Li3LaF6), lithium titanium phosphate (Li2Ti(PO4)2), lithium lanthanum phosphate (Li3La(PO4)2), lithium lanthanum fluorophosphate, lithium titanium fluorophosphate, lithium ytterbium phosphate (Li3Yb(PO4)2), and lithium gadolinium phosphate (Li3Gd(PO4)2).

[0023] In this invention, in the mixture containing layered oxide cathode material and lithium-ion conductor salt, the percentage of lithium-ion conductor salt in the molar amount of layered oxide cathode material can be 0.05%-2%, preferably 0.1%-0.5%, for example 0.15%, 0.2%, 0.25%, 0.3% or 0.4%.

[0024] In this invention, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is preferably one or more of dimethyl carbonate, N,N-dimethylformamide, isopropanol, anhydrous ethanol and deionized water.

[0025] In Method 1, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is preferably one or more of dimethyl carbonate, anhydrous ethanol, and deionized water.

[0026] In Method 2, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is preferably deionized water and / or anhydrous ethanol.

[0027] In Method 3, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is preferably dimethyl carbonate.

[0028] In this invention, in the mixture containing layered oxide cathode material and lithium-ion conductor salt, the mass ratio of the layered oxide cathode material to the volume of the solvent in the mixture can be 0.02-0.8 g / mL, for example 0.03 g / mL, 0.05 g / mL, 0.06 g / mL, 0.1 g / mL, 0.2 g / mL, 0.4 g / mL, 0.5 g / mL or 0.6 g / mL.

[0029] In some specific embodiments, when the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, the mixture containing the layered oxide cathode material and the lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material.

[0030] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material.

[0031] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate and / or lithium lanthanum phosphate.

[0032] More preferably, when the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a dimethyl carbonate mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid phases, and subsequently calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate and / or lithium lanthanum phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.15%, 0.2%, 0.25%, 0.3%, or 0.4%.

[0033] In one specific embodiment, when the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is 0.2% lithium lanthanum phosphate or 0.2% lithium titanium phosphate.

[0034] In some specific embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, the mixture containing the layered oxide cathode material and lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material.

[0035] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; the solvent in the mixture is anhydrous ethanol and / or deionized water.

[0036] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid phases, and finally calcined to obtain the modified layered oxide cathode material; wherein the solvent in the mixture is anhydrous ethanol and / or deionized water; and the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate.

[0037] More preferably, when the layered oxide cathode material is single-crystal lithium cobalt oxide, the mixture containing the layered oxide cathode material and the lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid phases, and finally calcined to obtain the modified layered oxide cathode material; wherein, the solvent in the mixture is anhydrous ethanol and / or deionized water; the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate and lithium lanthanum phosphate, lithium ytterbium phosphate and lithium gadolinium phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3% or 0.4%.

[0038] In one specific embodiment, when the layered oxide cathode material is single-crystal lithium cobalt oxide, an anhydrous ethanol mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is 0.3% lithium hexafluorotitanate, 0.3% lithium hexafluorolanthanum oxide, 0.3% lithium lanthanum phosphate, 0.3% lithium ytterbium phosphate, or 0.3% lithium gadolinium phosphate.

[0039] In some specific embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, the mixture containing the layered oxide cathode material and the lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material.

[0040] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate.

[0041] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3%, or 0.4%.

[0042] In one specific embodiment, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material; wherein, the solvent in the mixture is deionized water; and the lithium-ion conductor salt is 0.3% lithium hexafluorolanthanum oxide or 0.3% lithium lanthanum phosphate.

[0043] In some specific embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, the mixture containing the layered oxide cathode material and the lithium-ion conductor salt is mixed and reacted, and then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material.

[0044] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and lithium-ion conductor salt is mixed and reacted, and then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material.

[0045] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a dimethyl carbonate mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, and then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate.

[0046] In some preferred embodiments, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a dimethyl carbonate mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, followed by solvent evaporation and calcination to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3%, or 0.4%.

[0047] In one specific embodiment, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, and then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material; wherein, the lithium-ion conductor salt is 0.3% lithium titanium phosphate.

[0048] In this invention, the method for preparing the mixture containing layered oxide cathode material and lithium-ion conductor salt preferably includes the following steps: adding a solvent to the mixture of layered oxide cathode material and lithium-ion conductor salt.

[0049] In Method 1 and / or Method 3, the mixing reaction refers to reacting the mixture in a mixed state. The mixing method may be stirring and / or ultrasound. The stirring speed may be 100-800 rpm, for example, 200 rpm, 300 rpm, or 400 rpm.

[0050] In Method 1, preferably, the mixture is subjected to a mixing reaction in a closed state, for example, by sealing the mixture with a sealing film before the mixing reaction. The temperature of the mixing reaction can be 20-80℃, for example, 25℃, 30℃ or 50℃; the time of the mixing reaction can be 0.5-24h, for example, 1h, 2h, 3h, 4h or 8h.

[0051] In Method 1, the solid-liquid separation method can be conventional in the art, such as vacuum filtration. After the solid-liquid separation, the separated solids generally need to be dried. The drying is generally carried out in an oven. The drying temperature can be 80-120℃, for example, 100℃.

[0052] In Method 2, the temperature of the solvothermal reaction can be 120-200℃, for example, 140℃, 150℃, 160℃, or 170℃. The time of the solvothermal reaction can be 1-24h, for example, 2h, 4h, 5h, or 8h. After the solvothermal reaction is completed, solid-liquid separation and drying are generally required.

[0053] In Method 3, preferably, the mixture is subjected to a mixing reaction in a closed state, for example, by sealing the mixture with a sealing film before the mixing reaction. The temperature of the mixing reaction can be 20-90℃, for example, 30℃, 50℃, 60℃, or 80℃; the time of the mixing reaction can be 0.5-24h, for example, 2h, 3h, 4h, or 8h. The solvent evaporation is generally carried out by leaving the mixture in an open state, for example, by performing the mixing reaction in a closed state and then continuing to evaporate the solvent in an open state.

[0054] In this invention, the calcination atmosphere is generally an oxygen atmosphere or an air atmosphere. When the calcination atmosphere is an oxygen atmosphere, the oxygen flow rate can be 40-100 mL / min, for example, 50 mL / min, 60 mL / min, or 70 mL / min. The calcination equipment can be conventional in the art, such as a tube furnace. The calcination temperature can be 400-1000℃, preferably 500-900℃, for example, 600℃, 700℃, or 800℃. The calcination time can be 2-12 hours, for example, 4 hours, 5 hours, 6 hours, or 8 hours.

[0055] In this invention, after the calcination is completed, the modified layered oxide cathode material is generally required to be dry-ground and then stored in a vacuum environment.

[0056] The present invention also provides a modified layered oxide cathode material prepared by the preparation method described above.

[0057] In this invention, the modified layered oxide cathode material preferably comprises a layered oxide cathode material and a first coating layer and a second coating layer sequentially coated on its surface; wherein, the first coating layer is composed of metal ions originally present on the surface of the layered oxide cathode material and d... 0 The perovskite layer is formed by ion exchange of high-valence transition metal ions with electronic configuration; the second coating layer includes a lithium-ion conductor salt.

[0058] The perovskite layer may be composed of TMCoO. 3-δ TM refers to d 0 High-valence transition metals with electronic configurations, such as La, Gd, or Yb.

[0059] Preferably, the second coating layer further includes LiF and / or Li3PO4.

[0060] The present invention also provides an application of the modified layered oxide cathode material as described above in lithium-ion batteries.

[0061] The present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode comprises a current collector and a modified layered oxide positive electrode material as described above.

[0062] In this invention, according to conventional practice in the art, the current collector is generally aluminum foil.

[0063] In this invention, the method for preparing the positive electrode sheet preferably includes the following steps: uniformly coating the surface of the current collector with a slurry containing the modified layered oxide positive electrode material, conductive carbon black and polyvinylidene fluoride, and then drying it.

[0064] The weight ratio of the modified layered oxide cathode material, the conductive carbon black, and the polyvinylidene fluoride can be conventional in the art, preferably (70-90):(5:15):(5-15), for example 80:10:10.

[0065] The solvent in the slurry can be conventional in the art, such as N-methylpyrrolidone. The mass ratio of the solvent to the solid powder in the slurry can be (2-5):1, for example, 2.5:1.

[0066] The drying temperature can be 80-150℃, for example, 100℃, 110℃ or 120℃. The drying time can be 6-24h, for example, 8h, 10h, 12h or 18h.

[0067] In this invention, the areal density of the modified layered oxide cathode material on the cathode sheet can be 2.5-3.0 mg / cm³. 2 For example, 2.8 mg / cm 2 .

[0068] In this invention, the negative electrode sheet can be conventional in the art, such as a lithium metal sheet or a graphite negative electrode.

[0069] In this invention, the electrolyte can be conventional in the art, such as a mixed solution of 1M lithium hexafluorophosphate, ethylene carbonate, and diethyl carbonate, wherein the volume ratio of ethylene carbonate to diethyl carbonate is 1:1. The separator can be conventional in the art, such as a polypropylene separator.

[0070] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0071] The reagents and raw materials used in this invention are all commercially available.

[0072] The positive and progressive effects of this invention are as follows:

[0073] The modified layered oxide cathode material prepared by this invention has excellent electrochemical performance, especially good long-cycle stability, and the coating layer has good uniformity and density. Moreover, the preparation method is simple and low cost. Attached Figure Description

[0074] Figure 1 Cyclic performance test graphs of the materials prepared in Example 1 and the materials in Comparative Example 1;

[0075] Figure 2 The graphs show the cyclic performance test results of the materials prepared in Example 2 and the materials in Comparative Example 1.

[0076] Figure 3The graphs show the cyclic performance test results of the materials prepared in Example 3 and the materials in Comparative Example 2.

[0077] Figure 4 The graphs show the cyclic performance test results of the materials prepared in Example 4 and the materials in Comparative Example 2.

[0078] Figure 5 The graphs show the cyclic performance test results of the materials prepared in Example 5 and the materials in Comparative Example 2.

[0079] Figure 6 The graph shows the cycle performance test results of the material prepared in Example 8 and the material in Comparative Example 2 at a cutoff voltage of 4.6V.

[0080] Figure 7 The graph shows the cycle performance test results of the materials prepared in Example 8 and the materials in Comparative Example 2 at a cutoff voltage of 4.65V.

[0081] Figure 8 The graph shows the cycle performance test results of the material prepared in Example 9 and the material in Comparative Example 2 at a cutoff voltage of 4.65V.

[0082] Figure 9 The graph shows the cycle performance test results of the material prepared in Example 10 and the material in Comparative Example 2 at a cutoff voltage of 4.6V.

[0083] Figure 10 The graph shows the cycle performance test results of the material prepared in Example 10 and the material in Comparative Example 2 at a cutoff voltage of 4.65V.

[0084] Figure 11 The graph shows the cycle performance test results of the material prepared in Example 11 and the material in Comparative Example 2 at a cutoff voltage of 4.6V.

[0085] Figure 12 The graph shows the cycle performance test results of the material prepared in Example 11 and the material in Comparative Example 2 at a cutoff voltage of 4.65V.

[0086] Figure 13 The graph shows the cycle performance test results of the material prepared in Example 12 and the material in Comparative Example 2 at a cutoff voltage of 4.6V.

[0087] Figure 14 The graph shows the cycle performance test results of the material in Comparative Example 1 at a cutoff voltage of 4.4V.

[0088] Figure 15 The graph shows the cycle performance test results of the material in Comparative Example 2 at a cutoff voltage of 4.6V.

[0089] Figure 16 The graph shows the cycle performance test results of the material in Comparative Example 2 at a cutoff voltage of 4.65V. Detailed Implementation

[0090] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0091] The active material used in Examples 1-2 is LiNi, a single-crystal high-nickel ternary cathode material purchased from BAK Battery. 0.92 Co 0.05 Mn 0.03 O2.

[0092] Example 1

[0093] Coating by stirring and filtration: A certain amount of active material was taken, and lithium titanium phosphate (Li₂Ti(PO₄)₂) was added as a dopant at 0.2% of the molar amount of the active material. The mixed powder (measured as 2g of active material) was placed in a beaker, and 60ml of dimethyl carbonate solvent was added. After sealing with a wax film, the mixture was stirred directly at 200rpm. After stirring at room temperature for about 3 hours, the suspension was rinsed with dimethyl carbonate using a vacuum filtration device. After rinsing, the filter paper was removed and dried in an oven at 100℃. After drying, the powder on the filter paper was collected in a ceramic crucible, placed in a tube furnace, and calcined at 700℃ for 5 hours under an oxygen atmosphere at a flow rate of 60mL / min. After sintering, the finished powder was removed, dry-ground in a mortar, and then placed into sample tubes. The samples were stored under vacuum for subsequent testing and synthesis.

[0094] Example 2

[0095] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the metal salt was replaced with 0.2% lithium lanthanum phosphate (Li3La(PO4)2).

[0096] The active material used in Examples 3-12 is a single-crystal lithium cobalt oxide material purchased from Xiamen Tungsten New Energy.

[0097] Examples 3-7

[0098] Compared with Example 1, except that the active material, metal salt, metal salt doping amount and solvent are replaced with the parameters in Table 1, all other operations and conditions are the same as in Example 1.

[0099] Table 1

[0100] Active substances Metal salt type and doping amount solvent Example 3 Single-crystal lithium cobalt oxide materials 0.3% Lithium Hexafluorotitanate Anhydrous ethanol Example 4 Single-crystal lithium cobalt oxide materials 0.3% Lithium hexafluorolanthanum oxide Deionized water Example 5 Single-crystal lithium cobalt oxide materials 0.3% Lithium Lanthanum Phosphate Deionized water Example 6 Single-crystal lithium cobalt oxide materials 0.3% lithium ytterbium phosphate Deionized water Example 7 Single-crystal lithium cobalt oxide materials 0.3% lithium gadolinium phosphate Deionized water

[0101] Example 8

[0102] Solvent-thermal synthesis: A certain amount of active material, single-crystal lithium cobalt oxide, was taken, and lithium hexafluorotitanate, a metal salt with a doping amount of 0.3% of the active material molar amount, was added. 35 ml of anhydrous ethanol was added to the mixed powder (measured as 2 g of active material), and the mixture was stirred at 200 rpm for 5 min at room temperature. The mixture was then transferred to a sealed reactor and reacted at 160℃ for 5 hours. After the reaction, the resulting suspension was rinsed with the same solvent using a vacuum filter. After rinsing, the filter paper was removed and dried in an oven at 100℃. After drying, the powder on the filter paper was collected in a ceramic crucible, placed in a tube furnace, and calcined at 700℃ for 5 h under an oxygen atmosphere at a flow rate of 60 mL / min. After sintering, the finished powder was removed, dry-ground in a mortar, and then placed into sample tubes. The samples were stored under vacuum for subsequent testing and synthesis.

[0103] Example 9

[0104] Compared with Example 6, the operation and conditions were the same as in Example 6, except that the metal salt was replaced with 0.3% lithium titanium phosphate.

[0105] Example 10

[0106] Compared with Example 6, the operation and conditions were the same as in Example 6, except that the metal salt was replaced with 0.3% lithium hexafluorolanthanum oxide and the solvent anhydrous ethanol was replaced with deionized water.

[0107] Example 11

[0108] Compared with Example 6, the operation and conditions were the same as in Example 6, except that the metal salt was replaced with 0.3% lithium lanthanum phosphate and the solvent anhydrous ethanol was replaced with deionized water.

[0109] Example 12

[0110] Coating by stirring and evaporation: A certain amount of active material was taken, and lithium titanium phosphate metal salt was added as a dopant at 0.3% of the molar amount of the active material. The mixed powder (measured as 2g of active material) was placed in a beaker, and 60mL of dimethyl carbonate solvent was added. After sealing with a wax film, the mixture was directly stirred at 200rpm at 80℃ for 3 hours. After sealing and stirring, the sealing film was opened and stirring was continued until the solvent was evaporated. After all the solvent evaporated, the powder was collected in a ceramic crucible and placed in a tube furnace. An oxygen atmosphere was introduced at a flow rate of 60mL / min, and calcination was carried out in this oxygen atmosphere at a temperature of 700℃ for 5 hours. After sintering, the finished powder was taken out, dry-ground in a mortar, and then placed into sample tubes. The samples were stored in a vacuum environment for subsequent testing and synthesis.

[0111] Comparative Example 1

[0112] Uncoated single-crystal high-nickel ternary cathode material LiNi 0.92 Co 0.05 Mn 0.03 O2(Ni92).

[0113] Comparative Example 2

[0114] Uncoated single-crystal lithium cobalt oxide material (LCO-XW).

[0115] Effect Example

[0116] Electrochemical performance testing

[0117] Synthesis and preparation of lithium-ion battery cathode sheets: Modified layered oxide cathode material, superconducting carbon black (SuperP), and polyvinylidene fluoride (PVDF) powder were mixed at a mass ratio of 80:10:10. After uniform mixing, N-methylpyrrolidone (NMP) liquid with a mass of 2.5 times the total solid weight was added. The above solution was mixed in a vortex mixer at room temperature for 1 hour to ensure uniform mixing of the slurry. The mixed slurry was uniformly coated onto aluminum foil, and after drying, it was formed into circular electrode sheets with a diameter of 12 mm using a circular punch. The electrodes were then dried in a vacuum oven at 110°C for 12 hours to remove residual solvent. The areal density of the active material on the electrode sheet was 2.8 mg / cm³. 2 After the prepared electrodes are dried, they are quickly transferred to a glove box for subsequent battery assembly.

[0118] Assembly of button-type lithium-ion batteries: Assembly is performed in a glove box under an argon atmosphere, where both moisture and oxygen concentrations must be below 0.1 ppm. Before assembly, all components, including the battery casing, separator, and electrode plates, must be dried in a vacuum environment and then transferred to the glove box. The positive electrode uses the lithium battery electrode plate prepared as described above, the negative electrode is a lithium metal sheet, and the separator is a polypropylene film cut from a thin film. The electrolyte is 1M lithium hexafluorophosphate dissolved in a 1:1 volume ratio ethylene carbonate / diethyl carbonate mixed solution. The battery assembly sequence is: negative electrode casing, negative electrode plate, separator, addition of electrolyte, positive electrode plate, positive electrode casing, and sealing with a fixed pressure using an electric button-type battery sealing machine. During assembly, the separator must be fully immersed in electrolyte, completely covering the electrode plates while effectively isolating the positive and negative electrodes. The positive and negative electrodes must be aligned to ensure stability. The assembled battery needs to be left to stand for 8 hours before testing can begin. The test results are shown in Table 2 and... Figures 1-16 .

[0119] Table 2

[0120]

[0121] Note: The discharge capacities for the 1st, 100th, 300th, and 500th cycles in Table 2 are all measured at 1C after rate testing (i.e., sequentially cycling at 0.1C for 1 cycle, 1C for 5 cycles, 2C for 5 cycles, 5C for 5 cycles, 10C for 5 cycles, 20C for 5 cycles, and 50C for 5 cycles). For Comparative Example 1 and Examples 1-2, 1C = 200 mAg. -1 Example 3-12, 1C = 280mAg -1 .

[0122] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified layered oxide cathode material, characterized in that, Includes the following steps: Method 1: Mix and react a mixture containing layered oxide cathode material and lithium-ion conductor salt, separate the solid and liquid phases, and then calcine the mixture to obtain the modified layered oxide cathode material. Alternatively, Method 2: After subjecting the mixture containing layered oxide cathode material and lithium-ion conductor salt to a solvothermal reaction, it is then calcined to obtain the modified layered oxide cathode material. Alternatively, method three: mix and react a mixture containing layered oxide cathode material and lithium-ion conductor salt, then evaporate the solvent and calcine to obtain the modified layered oxide cathode material.

2. The method for preparing the modified layered oxide cathode material as described in claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The layered oxide cathode material is one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide and nickel cobalt aluminum ternary cathode material, preferably one or more of single crystal lithium nickel cobalt manganese oxide, single crystal lithium cobalt oxide and single crystal nickel cobalt aluminum ternary cathode material; (2) The lithium-ion conductor salt includes one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium lanthanum fluorophosphate, lithium titanium fluorophosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate; (3) The chemical formula of the lithium-ion conductor salt is Li a [M(PO4) y F z ], where M is a high-valence metal ion with d0 configuration, 0≤y≤2, 0≤z≤6, and y and z cannot be 0 at the same time; (4) In the mixture containing layered oxide cathode material and lithium-ion conductor salt, the percentage of lithium-ion conductor salt in the molar amount of layered oxide cathode material is 0.05%-2%, preferably 0.1%-0.5%, for example 0.15%, 0.2%, 0.25%, 0.3% or 0.4%; (5) In the mixture containing layered oxide cathode material and lithium-ion conductor salt, the solvent is one or more of dimethyl carbonate, N,N-dimethylformamide, isopropanol, anhydrous ethanol and deionized water; (6) In the mixture containing layered oxide cathode material and lithium-ion conductor salt, the mass ratio of the layered oxide cathode material to the volume of the solvent in the mixture is 0.02-0.8 g / mL, for example 0.03 g / mL, 0.05 g / mL, 0.06 g / mL, 0.1 g / mL, 0.2 g / mL, 0.4 g / mL, 0.5 g / mL or 0.6 g / mL.

3. The method for preparing the modified layered oxide cathode material as described in claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (1) In Method 1, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is one or more of dimethyl carbonate, anhydrous ethanol and deionized water. (2) In Method 2, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is deionized water and / or anhydrous ethanol; (3) In Method 3, the solvent in the mixture containing layered oxide cathode material and lithium-ion conductor salt is dimethyl carbonate.

4. The method for preparing the modified layered oxide cathode material as described in claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (1) In method one, the mixture is mixed in a closed state, for example, the mixture is sealed with a sealing film before being mixed. (2) In Method 1, the temperature of the mixing reaction is 20-80℃, for example 25℃, 30℃ or 50℃; (3) In Method 1, the mixing reaction time is 0.5-24h, for example 1h, 2h, 3h, 4h or 8h; (4) In Method 2, the temperature of the solvothermal reaction is 120-200℃, for example 140℃, 150℃, 160℃ or 170℃; (5) In Method 2, the time of the solvothermal reaction is 1-24h, for example 2h, 4h, 5h or 8h; (6) In method three, the mixture is mixed in a closed state, for example, the mixture is sealed with a sealing film before being mixed. (7) In method three, the temperature of the mixed reaction is 20-90°C, for example 30°C, 50°C, 60°C or 80°C; (8) In Method 3, the mixing reaction time is 0.5-24h, for example 2h, 3h, 4h or 8h.

5. The method for preparing the modified layered oxide cathode material as described in claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The calcination atmosphere is an oxygen atmosphere or an air atmosphere; (2) The calcination temperature is 400-1000℃, preferably 500-900℃, for example 600℃, 700℃ or 800℃; (3) The calcination time is 2-12h, for example 4h, 5h, 6h or 8h.

6. The method for preparing the modified layered oxide cathode material as described in claim 1, characterized in that, When the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate and / or lithium lanthanum phosphate. Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid phases, and subsequently calcined to obtain the modified layered oxide cathode material; wherein the solvent in the mixture is anhydrous ethanol and / or deionized water; and the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate. Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, and lithium lanthanum phosphate. Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, and then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate.

7. The method for preparing the modified layered oxide cathode material as described in claim 6, characterized in that, When the layered oxide cathode material is single-crystal lithium nickel cobalt manganese oxide, a mixture of dimethyl carbonate containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid components, and finally calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate and / or lithium lanthanum phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.15%, 0.2%, 0.25%, 0.3% or 0.4%; Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then separated into solid and liquid phases, and subsequently calcined to obtain the modified layered oxide cathode material; wherein the solvent in the mixture is anhydrous ethanol and / or deionized water; the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, lithium lanthanum phosphate, lithium ytterbium phosphate, and lithium gadolinium phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3%, or 0.4%; Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a mixture containing the layered oxide cathode material and a lithium-ion conductor salt is subjected to a solvothermal reaction and then calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is one or more of lithium hexafluorotitanate, lithium hexafluorolanthanum oxide, lithium titanium phosphate, and lithium lanthanum phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3%, or 0.4%; Alternatively, when the layered oxide cathode material is single-crystal lithium cobalt oxide, a dimethyl carbonate mixture containing the layered oxide cathode material and a lithium-ion conductor salt is mixed and reacted, then the solvent is evaporated and calcined to obtain the modified layered oxide cathode material; wherein the lithium-ion conductor salt is lithium titanium phosphate, and the percentage of the lithium-ion conductor salt in the molar amount of the layered oxide cathode material is 0.1%-0.5%, for example 0.2%, 0.25%, 0.3% or 0.4%.

8. A modified layered oxide cathode material prepared by a method according to any one of claims 1-7.

9. The application of the modified layered oxide cathode material as described in claim 8 in lithium-ion batteries.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode comprises a current collector and the modified layered oxide positive electrode material as described in claim 8.

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