Lithium nickel manganese oxide positive electrode material and preparation method thereof, positive plate, lithium ion battery and power utilization device

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a lithium nickel manganese oxide positive electrode material and a preparation method thereof, a positive plate, a lithium ion battery and a power utilization device. The concentration of unpaired electrons in the lithium nickel manganese oxide positive electrode material is 10 a.u. 2 to 8000 a.u. 2. The positive electrode material is relatively good in electron transmission performance and relatively high in structural stability, and when the positive electrode material is applied to the lithium ion battery, Mn dissolution is less, so that the lithium ion battery has excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to lithium nickel manganese oxide cathode materials and their preparation methods, cathode sheets, lithium-ion batteries, and electrical devices. Background Technology

[0002] The positive electrode active material is a key component of a battery, determining its energy density and cycle life. Spinel-type lithium nickel manganese oxide (LiMO) has advantages such as low production cost, simple synthesis process, high operating voltage, good thermal stability, and excellent rate performance and low-temperature performance. Mn leaching is one of the main obstacles to its widespread application; on the one hand, Mn leaching from the surface of lithium nickel manganese oxide... 3+ A disproportionation reaction occurs to generate Mn. 2+ Dissolution into the electrolyte leads to rapid capacity decay. Furthermore, oxygen vacancies exacerbate structural damage during lithium-ion insertion / extraction, resulting in accelerated Mn dissolution. Therefore, the relevant technologies for lithium nickel manganese oxide cathode materials still require further improvement. Summary of the Invention

[0003] This application aims to at least partially solve one of the related technical problems. To this end, this application proposes a lithium nickel manganese oxide cathode material and its preparation method, cathode sheet, lithium-ion battery, and power device. The lithium nickel manganese oxide cathode material has better electron transport properties and stronger structural stability, and can reduce Mn dissolution.

[0004] A first aspect of this application provides a lithium nickel manganese oxide cathode material. According to an embodiment of this application, the concentration of unpaired electrons in this lithium nickel manganese oxide cathode material is 10 a.u. 2 ~8000a.u. 2 Preferably, it is 10a.u. 2 ~7500a.u. 2 This lithium nickel manganese oxide cathode material exhibits good electron transport properties and strong structural stability. Applying this cathode material to lithium-ion batteries can reduce Mn dissolution, resulting in excellent high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance.

[0005] According to an embodiment of this application, the lithium nickel manganese oxide cathode material satisfies: 1.96 ≤ g = hv / μ B B0≤1.99, preferably 1.965≤g≤1.988; where g represents the g-factor of the electron paramagnetic resonance spectrum of the lithium nickel manganese oxide cathode material; h represents Planck's constant in J·s; v represents the microwave frequency in GHz; μ B This represents the Bohr magneton, with units of A·m. 2 / J;B0 represents the applied magnetic field strength, in G.

[0006] According to embodiments of this application, the lithium nickel manganese oxide cathode material satisfies: 80% ≤ E = C 4.2V / C0×100%≤95%, preferably 82%≤E≤94%; where E represents the capacity contribution rate of Ni in the lithium nickel manganese oxide cathode material, C 4.2V C0 represents the discharge capacity of the battery using the lithium nickel manganese oxide cathode material at 4.2V during the first week of room temperature testing under conditions of 3.5V~4.95V and 0.1C / 0.1C.

[0007] According to embodiments of this application, the lithium nickel manganese oxide cathode material comprises the compound shown in Formula 1: LiNi 0.5 Mn 1.5-α M1 α M2 β O 4-θ A θ Formula 1 Where 0.01≤α≤0.05, 0.01≤β≤0.2, 0.01≤θ≤0.1 The M1 element includes at least one of B, Nb, and W; The M2 element includes at least one of Al, Y, Co, Mg, Zn, Cr, Fe, Cu, and Ti; Element A includes at least one of F, Cl, Br, S, and P.

[0008] According to embodiments of this application, the above-mentioned lithium nickel manganese oxide cathode material satisfies at least one of the following conditions: The lithium nickel manganese oxide cathode material is a single-crystal lithium nickel manganese oxide cathode material; The lithium nickel manganese oxide cathode material D 50 The size is 3μm to 10μm, preferably 4μm to 9μm; The compaction density (PD) of the lithium nickel manganese oxide cathode material is greater than 2.9 g / cm³. 3 ; The Mn leaching amount of the lithium nickel manganese oxide cathode material is ≤50ppm.

[0009] A second aspect of this application provides a method for preparing the lithium nickel manganese oxide cathode material described in the first aspect, comprising: The nickel-manganese precursor, lithium source, first additive, and second additive are mixed to obtain a mixture. The mixture is subjected to a single-stage sintering process to obtain a lithium nickel manganese oxide matrix.

[0010] The above-mentioned method for preparing lithium nickel manganese oxide cathode materials is simple and controllable, has low production cost, and can achieve large-scale production.

[0011] According to an embodiment of this application, the single-stage sintering includes sequential single-stage sintering, double-stage sintering, and triple-stage sintering, and satisfies at least one of the following conditions: The sintering temperature T1 of the first section is 450℃~550℃; The heating rate v1 of the sintering section is 2℃ / min~4℃ / min; The holding time t1 for the first sintering stage is 2h~4h; The temperature T2 for the two-stage sintering is 900℃~1000℃, preferably 930℃~980℃; The heating rate v2 of the two-stage sintering is 2℃ / min~4℃ / min; The holding time t2 for the two-stage sintering is 6h~12h; The sintering temperature T3 for the three stages is 500℃~700℃. The cooling rate v3 of the three-stage sintering is 1℃ / min~4℃ / min; The holding time t3 for the three-stage sintering is 2h~4h; The atmosphere for the first stage of sintering is air.

[0012] According to embodiments of this application, the above method satisfies at least one of the following conditions: The nickel-manganese precursor includes at least one of nickel-manganese hydroxide, nickel-manganese oxide, and nickel-manganese carbonate; The lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium chloride; The molar ratio of the transition metal element in the nickel-manganese precursor to the lithium element in the lithium source is 2:(1.02~1.10). The amount of the first additive is 0.01 wt% to 1 wt% of the total mass of the nickel-manganese precursor and the lithium source; The amount of the second additive is 0.05wt% to 2wt% of the total mass of the nickel-manganese precursor and the lithium source; The first additive includes at least one of boron-containing compounds, niobium oxide, and tungsten oxide; The second additive includes at least one of aluminum oxide, yttrium oxide, cobalt oxide, zinc oxide, titanium oxide, chromium oxide, aluminum fluoride, magnesium fluoride, lanthanum fluoride, copper sulfide, aluminum chloride, and phosphorus-containing compounds; preferably, the phosphorus-containing compounds include at least one of aluminum phosphate, lithium phosphate, titanium phosphate, and lithium aluminum titanium phosphate.

[0013] A third aspect of this application provides a positive electrode sheet comprising the lithium nickel manganese oxide positive electrode material described in the first aspect. This positive electrode sheet includes all the features and advantages of the lithium nickel manganese oxide positive electrode material described above, which will not be repeated here.

[0014] A fourth aspect of this application provides a lithium-ion battery comprising the lithium nickel manganese oxide cathode material described in the first aspect or the cathode sheet described in the third aspect. This lithium-ion battery exhibits excellent high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance.

[0015] A fifth aspect of this application provides an electrical device comprising the lithium nickel manganese oxide cathode material described in the first aspect, the cathode sheet described in the third aspect, or the lithium-ion battery described in the fourth aspect. This electrical device incorporates all the features and advantages of the aforementioned lithium nickel manganese oxide cathode material, cathode sheet, or lithium-ion battery, which will not be elaborated upon here. Attached Figure Description

[0016] Figure 1 These are the oxygen vacancy test curves of the lithium nickel manganese oxide cathode materials of Example 1 and Comparative Example 1 of this application.

[0017] Figure 2 This is the charge-discharge curve of the battery using lithium nickel manganese oxide cathode material in Example 1 of this application. Detailed Implementation

[0018] Embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting it.

[0019] In a first aspect, this application proposes a lithium nickel manganese oxide cathode material having an unpaired electron concentration of 10 a.u. 2 ~8000a.u. 2 For example, 10a.u. 2 ~7500a.u. 2 More specifically, the concentration of unpaired electrons in lithium nickel manganese oxide cathode materials can be 10 a.u. 2 50a.u. 2 100a.u. 2 500a.u. 2 1000a.u. 2 5000a.u. 2 8000a.u. 2 Or a range between either or both.

[0020] In this paper, the concentration of unpaired electrons can be characterized using EPR (Electron Paramagnetic Resonance Spectroscopy), a spectroscopic technique used to study substances containing unpaired electrons (such as free radicals, transition metal ions, and defect centers). Its basic principle is based on the energy level splitting of electron spins in an applied magnetic field, and the magnetic characteristics of the sample are detected through microwave absorption. The concentration of unpaired electrons reflects the number of oxygen vacancies.

[0021] During the synthesis of lithium nickel manganese oxide, high-temperature sintering inevitably leads to lattice oxygen loss, resulting in hole formation and changes in the redox state of nickel and manganese ions, thus generating unpaired electrons. The unpaired electrons at a suitable concentration in this application can be delocalized and enter the conduction band, improving the conductivity of the cathode material. Simultaneously, excessive concentration of unpaired electrons avoids an excessive number of oxygen vacancies, which could lead to poor electron transport and lattice collapse during cycling, shortening the material's lifespan. Within the aforementioned unpaired electron concentration range, the cathode material exhibits good electron transport performance, reduces Mn dissolution, maintains crystal structure stability, and improves the high-temperature cycle life, high-temperature storage performance, and low-temperature discharge performance of the cathode material.

[0022] According to an embodiment of this application, the lithium nickel manganese oxide cathode material satisfies: 1.96 ≤ g = hv / μ B B0≤1.99, specifically 1.965≤g≤1.988. More specifically, g can be 1.96, 1.97, 1.98, 1.99, or any two of them; where g represents the g-factor of the electron paramagnetic resonance spectrum of the lithium nickel manganese oxide cathode material, h represents Planck's constant in J·s, v represents the microwave frequency in GHz, and μ represents the value of g. B B0 represents the Bohr magneton, with units of A·m² / J; B0 represents the applied magnetic field strength, with units of G.

[0023] In this paper, the g-factor reflects the coupling relationship between the magnetic moment and angular momentum of unpaired electrons under the influence of an applied magnetic field, or in other words, the local environment in which the electrons reside. It is a measure of the degree of electron energy level splitting in the magnetic field, i.e., the strength of the effect of oxygen vacancies in the cathode material under the applied test magnetic field. A shift in the g-value indicates that the electrons originally bound in the cathode material lattice are affected by the change in the magnetic environment brought about by oxygen vacancies. A g-factor within the above range indicates that the cathode material has a suitable concentration of oxygen vacancies. An appropriate concentration of oxygen vacancies can improve the electron transport performance of the cathode material, enhance the structural stability of the cathode material, reduce Mn dissolution, and improve the overall electrical performance.

[0024] According to embodiments of this application, the lithium nickel manganese oxide cathode material satisfies: 80% ≤ E = C 4.2V / C0×100%≤95%, specifically, 82%≤E≤94%. More specifically, E can be 80%, 85%, 90%, 95%, or any two of these ranges, where E represents the Ni capacity contribution rate in the lithium nickel manganese oxide cathode material, and C 4.2V The term C0 represents the discharge capacity of a battery using the aforementioned lithium nickel manganese oxide cathode material at 4.2V during the first week of room temperature testing under conditions of 3.5V~4.95V and 0.1C / 0.1C. Within this range, the cathode material maintains a high capacity while also maintaining or improving its rate performance.

[0025] In this article, the Ni capacity contribution rate refers to the amount of manganese ions (Ni) in the material. 3+ The E value represents the percentage of charge capacity contributed by Ni during redox reactions during charging and discharging. A higher E value indicates that Ni... 3+ The greater the contribution of redox reactions to the total capacity, the higher the electrochemical activity of Ni in the cathode material.

[0026] According to embodiments of this application, the lithium nickel manganese oxide cathode material comprises the compound shown in Formula 1: LiNi 0.5 Mn 1.5-α M1 α M2 β O 4-θ A θ Formula 1 Where 0.01≤α≤0.05, 0.01≤β≤0.2, 0.01≤θ≤0.1 The M1 element includes at least one of B, Nb, and W; The M2 element includes at least one of Al, Y, Co, Mg, Zn, Cr, Fe, Cu, and Ti; Element A includes at least one of F, Cl, Br, S, and P.

[0027] Lithium nickel manganese oxide (NMO) cathode materials with the above-described structure can achieve several improvements. First, cation doping occupies transition metal sites, stabilizing the crystal structure. Second, high-valence elements such as W and Nb adjust the valence state of the transition metals, while trivalent elements like Y occupy these sites, stabilizing the structure. Third, anion doping occupies oxygen sites, repairing oxygen vacancies and further stabilizing the spinel structure of the NMO cathode material. This enhances both the high-temperature cycling and low-temperature discharge performance of the cathode material. Furthermore, NMO cathode materials with the aforementioned chemical formula can stabilize the crystal structure and reduce Mn dissolution, oxygen vacancies, and buffer internal stress during cycling. These two aspects work synergistically to significantly reduce internal resistance and improve the battery's high-temperature cycling and low-temperature discharge performance.

[0028] According to embodiments of this application, the lithium nickel manganese oxide cathode material is a single-crystal lithium nickel manganese oxide cathode material. Single-crystal lithium nickel manganese oxide cathode materials can reduce the generation of intergranular cracks, thereby effectively maintaining the integrity of electron and ion conduction pathways and reducing the risk of side reactions, thus exhibiting excellent cycle performance.

[0029] According to embodiments of this application, the D of the lithium nickel manganese oxide cathode material 50 The thickness ranges from 3μm to 10μm, specifically 4μm to 9μm. More specifically, the D... 50 The thickness ranges from 3 μm, 7 μm, 9 μm, 10 μm, or any two thereof. Within this range, the cathode material exhibits a higher compaction density, thereby increasing the energy density of the cathode material.

[0030] In this article, D 50 This indicates that particles with a diameter smaller than or larger than this value account for 50% of the total particle volume. This can be tested using a laser particle size analyzer.

[0031] According to an embodiment of this application, the compaction density PD of the lithium nickel manganese oxide cathode material is > 2.9 g / cm³. 3 Within the aforementioned compaction density range, this cathode material exhibits a high energy density.

[0032] According to embodiments of this application, the Mn leaching amount of the lithium nickel manganese oxide cathode material is ≤50ppm. This cathode material exhibits low Mn leaching and good cycle performance.

[0033] A second aspect of this application provides a method for preparing the lithium nickel manganese oxide cathode material described in the first aspect, comprising: S10: Mix the nickel-manganese precursor, lithium source, first additive and second additive to obtain a mixture.

[0034] In this step, the nickel-manganese precursor, lithium source, first additive, and second additive are mixed in a certain proportion to obtain a homogeneous mixture.

[0035] According to embodiments of this application, the nickel-manganese precursor comprises at least one of nickel-manganese hydroxide, nickel-manganese oxide, and nickel-manganese carbonate. These substances provide nickel and manganese elements at a low cost.

[0036] According to embodiments of this application, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium chloride. The above-mentioned lithium source can provide lithium elemental, and its cost is relatively low.

[0037] According to embodiments of this application, the molar ratio of the transition metal element in the nickel-manganese precursor to the lithium element in the lithium source is 2:(1.02~1.10), specifically 2:1.02, 2:1.03, 2:1.04, 2:1.05, 2:1.06, 2:1.07, 2:1.08, 2:1.09, 2:1.10, or any range between two of these. Within the above range, a lithium nickel manganese oxide cathode material with excellent comprehensive performance can be obtained.

[0038] According to embodiments of this application, the D of the nickel-manganese precursor 50 The surface area is 3.0 μm to 10.0 μm. Within this range, a suitable atomic diffusion path and specific surface area for the reaction can be provided, which helps to promote the subsequent sintering reaction.

[0039] According to embodiments of this application, the first additive includes at least one selected from boron-containing compounds, niobium oxide, and tungsten oxide. These substances can provide doped cations, thereby stabilizing the crystal structure of the lithium nickel manganese oxide cathode material.

[0040] According to an embodiment of this application, the amount of the first additive is 0.01 wt% to 1 wt% of the total mass of the nickel-manganese precursor and the lithium source, specifically such as 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, or any range between two of these. Within the above range, sufficient doped cations can be provided, thereby stabilizing the crystal structure of the lithium nickel manganese oxide cathode material.

[0041] According to embodiments of this application, the second additive includes at least one selected from aluminum oxide, yttrium oxide, cobalt oxide, zinc oxide, titanium oxide, chromium oxide, aluminum fluoride, magnesium fluoride, lanthanum fluoride, copper sulfide, aluminum chloride, and a phosphorus-containing compound. As an example, the phosphorus-containing compound includes at least one selected from aluminum phosphate, lithium phosphate, titanium phosphate, and lithium aluminum titanium phosphate. These substances can provide doped cations and anions, thereby stabilizing the crystal structure of the lithium nickel manganese oxide cathode material.

[0042] According to embodiments of this application, the amount of the second additive is 0.05 wt% to 2 wt% of the total mass of the nickel-manganese precursor and the lithium source, specifically such as 0.05 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, or any range thereof. Within the above range, sufficient doped cations and anions can be provided, thereby stabilizing the crystal structure of the lithium nickel manganese oxide cathode material.

[0043] S20: The mixture is subjected to a single-stage sintering process to obtain lithium nickel manganese oxide cathode material.

[0044] In this step, the atoms of each element in the mixture undergo contact diffusion and reaction during the initial sintering process to form crystal nuclei. As sintering continues, the crystal nuclei grow continuously, resulting in a lithium nickel manganese oxide cathode material with a complete crystal structure.

[0045] According to embodiments of this application, the segmented sintering includes sequentially performing a first-stage sintering, a second-stage sintering, and a third-stage sintering. Thus, by progressively improving the crystallinity of the material through segmented sintering, it is beneficial to obtain cathode materials with high structural stability, while also helping to suppress high-temperature damage to the structure; it also facilitates control over the particle size and morphology of the cathode material, thereby obtaining cathode materials with better overall performance.

[0046] In some embodiments, the sintering temperature T1 is 450℃~550℃, specifically 450℃, 480℃, 500℃, 520℃, 550℃, or any range between two of these. This temperature is conducive to the initial formation of the crystal structure and the fusion growth of single crystal particles.

[0047] In some embodiments, the heating rate v1 of the sintering stage is 2°C / min to 4°C / min, specifically 2°C / min, 3°C / min, 4°C / min, or any range between two of them. This allows for the gentle and complete decomposition of the atoms of each element in the precursor, and enables sufficient contact and diffusion between the lithium source, precursor, and additives, promoting a uniform reaction.

[0048] In some embodiments, the holding time t1 for the sintering stage is 2h to 4h, specifically 2h, 3h, 4h, or any combination thereof. Within this time range, the initial formation of the crystal structure can be achieved, allowing the reaction to proceed fully without wasting time.

[0049] In some embodiments, the two-stage sintering temperature T2 is 900℃~1000℃, specifically 930℃~980℃. As an example, the two-stage sintering temperature T2 can more specifically be 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, or any range between two of these. Within the above temperature range, sufficient driving force is provided to allow for sufficient atomic diffusion, improve the integrity of the crystal structure, and facilitate the obtaining of lithium nickel manganese oxide with high crystallinity.

[0050] In some embodiments, the heating rate v2 of the two-stage sintering is 2℃ / min to 4℃ / min, specifically 2℃ / min, 3℃ / min, 4℃ / min, or any range between two of them. This heating rate allows for a more uniform temperature increase, which is beneficial for obtaining lithium nickel manganese oxide cathode materials with higher structural integrity and stability.

[0051] In some embodiments, the holding time t2 for the two-stage sintering is 6h to 12h, specifically 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any range between two of these. Within this time range, the basic integrity of the crystal structure can be formed, allowing the reaction to proceed fully without wasting time.

[0052] In some embodiments, the sintering temperature T3 of the three stages is 500℃~700℃, specifically 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, 700℃, or any two of these ranges. Within the above temperature range, the proportion of ordered / disordered structures in the material can be controlled to obtain a nickel-manganese spinel material with a small degree of disorder, thereby improving the overall performance of the cathode material.

[0053] In some embodiments, the cooling rate v3 of the three-stage sintering is 1℃ / min to 4℃ / min, specifically 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or any range between two of these. This cooling rate allows the temperature to decrease uniformly and slowly, which is beneficial for further improving the structural integrity and stability of the cathode material.

[0054] In some embodiments, the holding time t3 for the three-stage sintering is 2h to 4h, specifically 2h, 3h, 4h, or any two of these ranges. Within this time range, the crystal structure can be further perfected.

[0055] According to an embodiment of this application, the atmosphere for the primary segmented sintering is air. This provides an oxygen-containing environment while reducing the probability of oxygen vacancies forming in lithium nickel manganese oxide.

[0056] According to the embodiments of this application, after obtaining the lithium nickel manganese oxide cathode material, the process may further include: after naturally cooling to room temperature, crushing the lithium nickel manganese oxide cathode material (using at least one of a mechanical crusher, colloid mill, or air jet mill), the particle size of the crushed particles being 3µm to 10µm, and finally sieving through a 400-mesh sieve to obtain the lithium nickel manganese oxide cathode material.

[0057] A third aspect of this application provides a positive electrode sheet comprising the lithium nickel manganese oxide positive electrode material described in the first aspect. This positive electrode sheet includes all the features and advantages of the lithium nickel manganese oxide positive electrode material described above, which will not be repeated here.

[0058] According to an embodiment of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector. The positive active material layer includes the lithium nickel manganese oxide positive electrode material, positive conductive agent, and positive binder described above.

[0059] According to embodiments of this application, the positive current collector can be a metal current collector or a composite current collector. Metal current collectors include at least one of aluminum foil current collectors and carbon-coated aluminum foil current collectors; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0060] According to embodiments of this application, the positive electrode binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. As a specific example, this application uses polyvinylidene fluoride.

[0061] According to embodiments of this application, the positive electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As a specific example, this application uses carbon black.

[0062] A fourth aspect of this application provides a lithium-ion battery comprising the lithium nickel manganese oxide cathode material described in the first aspect or the cathode sheet described in the third aspect. This lithium-ion battery exhibits low internal resistance, excellent high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance.

[0063] According to an embodiment of this application, the lithium-ion battery further includes a negative electrode, an electrolyte, and a separator. The separator is disposed between adjacent positive and negative electrodes. The positive electrode, negative electrode, and separator are all immersed in the electrolyte. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive and negative electrodes. The electrolyte plays the role of conducting ions between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes and mainly plays the role of preventing short circuits between the positive and negative electrodes, while allowing active ions to pass through.

[0064] According to an embodiment of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located at least on one side of the negative electrode sheet. The negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0065] According to an embodiment of this application, the negative current collector includes copper foil.

[0066] According to embodiments of this application, the negative electrode active material may include carbon-based materials (such as artificial graphite), silicon-based materials, tin-based materials, etc.

[0067] According to embodiments of this application, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0068] According to embodiments of this application, the negative electrode conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0069] According to embodiments of this application, the diaphragm includes polyethylene diaphragm, polypropylene diaphragm, polyethylene / polypropylene composite diaphragm, etc.

[0070] A fifth aspect of this application provides an electrical device comprising the lithium nickel manganese oxide cathode material described in the first aspect, the cathode sheet described in the third aspect, or the lithium-ion battery described in the fourth aspect. This electrical device incorporates all the features and advantages of the aforementioned lithium nickel manganese oxide cathode material, cathode sheet, or lithium-ion battery, which will not be elaborated upon here.

[0071] It is understood that there are no particular restrictions on the specific type of electrical device; it can be any device that uses a lithium-ion battery as a power source or energy storage unit. For example, electrical devices include, but are not limited to, electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (such as mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0072] It is understandable that, in addition to the lithium-ion battery mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0073] The embodiments of this application are described in detail below.

[0074] Example 1 Preparation of cathode materials: (1) Preparation of lithium nickel manganese oxide matrix: according to the nickel manganese precursor (Ni:Mn=25:75, D 50 A nickel-manganese oxide (NiMC) precursor (4.0 μm) was mixed with lithium carbonate at a transition metal element to lithium element molar ratio of 2:1.05. Based on the total mass of the nickel-manganese precursor and lithium carbonate, 0.5% wt niobium oxide, 1.0% wt yttrium oxide, and 0.5% wt aluminum phosphate were added. The mixture of lithium carbonate, nickel-manganese precursor, niobium oxide, yttrium oxide, and aluminum phosphate was then mixed in a high-speed mixer. The mixture was sintered in air at a heating rate of 3 °C / min to 500 °C for 3 hours, followed by a second-stage sintering at 3 °C / min to 950 °C for 8 hours, and finally a third-stage sintering at 3 °C / min to 600 °C for 2 hours. After cooling, the mixture was crushed and sieved to obtain the lithium nickel manganese oxide cathode material. The chemical formula is LiNi. 0.5 Mn 1.467 Nb 0.007 Y 0.018 Al 0.008 O 3.992 P 0.008 .

[0075] Battery fabrication: LiNi 0.5 Mn 1.467 Nb 0.007 Y 0.018 Al 0.008 O 3.992 P 0.008A slurry was prepared by thoroughly mixing positive electrode active material, conductive carbon black, and polyvinylidene fluoride (PVDF) with an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:3:2. This slurry was then coated onto aluminum foil and dried in a vacuum drying oven at 120°C for 12 hours. After drying, the foil was pressed into a positive electrode sheet with a diameter of 11 mm and a thickness of 3.2 mm using a pressure of 100 MPa. The areal density of the positive electrode sheet was 133.5 g / m³. 2 A lithium metal sheet with a diameter of 11 mm and a thickness of 1 mm was used as the negative electrode. A polypropylene microporous membrane (Celgard 2325) with a thickness of 25 μm was used as the separator. The electrolyte was a mixture of equal volumes of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC). Assembly was carried out in a glove box under an argon atmosphere, where the water and oxygen content was <5 ppm. After assembling the positive electrode, separator, negative electrode, and electrolyte into a CR2025 coin cell, the cell was allowed to stand for 6 hours.

[0076] The specific parameters of Examples 2-13 and Comparative Examples 1-8 are shown in Table 1. All other parameters are the same as those of Example 1.

[0077] Table 1

[0078] Note: In Table 1, the dosage of the first additive refers to the mass ratio of the first additive to the total mass of the nickel-manganese precursor and the lithium source; the dosage of the second additive refers to the mass ratio of the first additive to the total mass of the nickel-manganese precursor and the lithium source. In Example 1, the dosage of the second additive "1.0+0.5" means that Y2O3 is 1.0% of the total mass of the nickel-manganese precursor and the lithium source, and AlPO4 is 0.5% of the total mass of the nickel-manganese precursor and the lithium source. Other similar descriptions have the same meaning.

[0079] Test method: (1) Mn dissolution: First, the material was prepared into a coin cell, then charged to 4.95V, the electrode was disassembled and cleaned with DMC solution. Then the electrode was cut into a certain size, weighed and recorded. Then it was placed in a 10mL dry open glass bottle, the bottle mouth was sealed with a tight-fitting film, and then 5g of electrolyte was accurately weighed in a glove box and added to the glass bottle. Place the glass bottle in a 60℃ electric thermostatic drying oven for 7 days. After the specified storage time, use a syringe with a 0.45µm needle filter to draw about 2mL of the clear upper electrolyte solution, ensuring that there is no black positive electrode material in the electrolyte. Transfer it to a 50mL beaker, digest and make up to volume, and use ICP to measure the Mn content in the solution.

[0080] (2) Concentration of unpaired electrons / g factor: The concentration of unpaired electrons in the cathode material powder was tested using an ESR5000 (Bruker). A certain amount of powder was placed in a sample tube and placed in a preheated device for testing. The scanning interval and other parameters were set for testing. After the test was completed, clicking "Find Zero Crossing" directly read the zero crossover point of the spectral peak, i.e., the g value. Data processing: Import the measured data into the software and select the "Baseline (subtract automatic)" function for baseline processing; then use the "Integration" function to perform the first integration on the selected spectral range to obtain the absorption curve A(B); on the first integration curve (A(B)) obtained in the previous step, perform the integration operation again to read the concentration value of unpaired electrons.

[0081] (3) D 50 The particle size distribution was obtained using a Marvern Mastersizer 3000 laser particle size analyzer. (4) BET: Measured using a Tristar 3020 surface area analyzer from Micromeritics. (5) Total alkali: The test was performed using a Metrohm OMNIS Sample Robot potentiometric titrator. 5.0000±0.0500g of sample was weighed into a 150mL beaker and the sample mass Msample was recorded. 95.00±0.500g of ultrapure water was added and the water mass M(H2O) was recorded. Magnetic stirring was used at 450rpm for 5min. The mixture was filtered using an aqueous membrane filter, and 80.000±0.500g of the filtrate was weighed and placed on the sample tray for testing. The OMNIS software was opened, and the sample mass Msample, water mass M(H2O), filtrate mass Mfiltrate, tray number, and tag number were entered in the sample list. "Sequence determination" was selected to begin the determination. After the test was completed, the total alkali data generated by the software was recorded.

[0082] (6) Electrochemical performance test: Coin cell half-cells were used for testing. The test voltage was 3.5V-4.95V. The cells were charged to 4.95V using constant current and constant voltage charging and discharged to 3.5V using constant current discharging.

[0083] (6-1) 0.1C discharge capacity: At room temperature of 25℃, charge and discharge at a current of 0.1C for 1 week, and record the discharge capacity C0 of the first week; E calculation method: At room temperature (25℃), charge and discharge at 0.1C for one cycle, record the discharge capacity of 4.2V in the first cycle, and use C... 4.2V This means that E=C 4.2V / C0×100%; (6-2) Low-temperature discharge duration test: After activation at 0.1C for one cycle (4.95V cutoff) at room temperature (25℃), charge to 30% SOC at 0.5C. Then transfer to a -20℃ low-temperature cabinet and let stand for 1.5h. Discharge to 3.5V at 0.5C. The time taken is the low-temperature discharge duration. (6-3) -20℃ Low Temperature Capacity Retention Rate Test: The button cell was activated by charging and discharging at 0.1C for 1 week at 25℃. In the second week, it was charged and discharged at 1C and the capacity was recorded as B1. In the third week, it was fully charged at 1C and then transferred to a -20℃ constant temperature chamber for 3 hours. It was then discharged at 1C and the capacity was recorded as B2. The -20℃ low temperature capacity retention rate is B2 / B1×100%.

[0084] (6-4) High temperature cycle test: The battery is placed in a 45℃ high temperature test chamber. The battery is activated by 0.1C charge and discharge in the first week, and 1C charge and discharge is used from the second week to the 80th week. The cycle retention rate after 80 weeks is calculated, which is the cycle retention rate at 45℃.

[0085] (6-5) Storage impedance test: DCR impedance before cycling and DCR impedance after cycling: Before the battery is fully charged, test its impedance at 50% SOC, which is the initial impedance; after the battery is fully charged after the high temperature cycle test, test its impedance at 50% SOC again, which is the final impedance. The impedance growth rate is % = (final impedance - initial impedance) / initial impedance × 100%.

[0086] Table 2

[0087] Table 3

[0088] The data above shows that the concentration of unpaired electrons is 10 a.u. 2 ~8000a.u. 2 Batteries using lithium nickel manganese oxide cathode material have higher capacity, higher high-temperature cycle retention, excellent low-temperature capacity performance, and lower impedance.

[0089] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0090] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0091] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A lithium nickel manganese oxide cathode material, characterized in that, The concentration of unpaired electrons in the lithium nickel manganese oxide cathode material is 10 a.u. 2 ~8000a.u. 2 Preferably, it is 10a.u. 2 ~7500a.u. 2 .

2. The lithium nickel manganese oxide cathode material according to claim 1, characterized in that, satisfy: 1.96≤g=hv / μ B B0≤1.99, preferably 1.965≤g≤1.988; Where g represents the g-factor of the electron paramagnetic resonance spectrum of the lithium nickel manganese oxide cathode material; h represents Planck's constant in J·s; v represents the microwave frequency in GHz; μ B This represents the Bohr magneton, with units of A·m. 2 / J;B0 represents the applied magnetic field strength, in G.

3. The lithium nickel manganese oxide cathode material according to claim 1, characterized in that, satisfy: 80%≤E=C 4.2V / C0×100%≤95%, preferably 82%≤E≤94%; Where E represents the capacity contribution rate of Ni in the lithium nickel manganese oxide cathode material, and C 4.2V C0 represents the discharge capacity of the battery using the lithium nickel manganese oxide cathode material at 4.2V during the first week of room temperature testing under conditions of 3.5V~4.95V and 0.1C / 0.1C.

4. The lithium nickel manganese oxide cathode material according to any one of claims 1 to 3, characterized in that, Including the compounds shown in Formula 1: LiNi 0.5 Mn 1.5-α M1 α M2 β O 4-θ A θ Formula 1 Where 0.01≤α≤0.05, 0.01≤β≤0.2, 0.01≤θ≤0.1 The M1 element includes at least one of B, Nb, and W; The M2 element includes at least one of Al, Y, Co, Mg, Zn, Cr, Fe, Cu, and Ti; Element A includes at least one of F, Cl, Br, S, and P.

5. The lithium nickel manganese oxide cathode material according to any one of claims 1 to 4, characterized in that, At least one of the following conditions must be met: The lithium nickel manganese oxide cathode material is a single-crystal lithium nickel manganese oxide cathode material; The lithium nickel manganese oxide cathode material D 50 The size is 3μm to 10μm, preferably 4μm to 9μm; The compaction density (PD) of the lithium nickel manganese oxide cathode material is greater than 2.9 g / cm³. 3 ; The Mn leaching amount of the lithium nickel manganese oxide cathode material is ≤50ppm.

6. A method for preparing the lithium nickel manganese oxide cathode material according to any one of claims 1 to 5, characterized in that, include: The nickel-manganese precursor, lithium source, first additive, and second additive are mixed to obtain a mixture. The mixture is subjected to a single-stage sintering process to obtain lithium nickel manganese oxide cathode material.

7. The method according to claim 6, characterized in that, The single-stage sintering includes sequential single-stage sintering, double-stage sintering, and triple-stage sintering, and satisfies at least one of the following conditions: The sintering temperature T1 of the first section is 450℃~550℃; The heating rate v1 of the sintering section is 2℃ / min~4℃ / min; The holding time t1 for the first sintering stage is 2h~4h; The temperature T2 for the two-stage sintering is 900℃~1000℃, preferably 930℃~980℃; The heating rate v2 of the two-stage sintering is 2℃ / min~4℃ / min; The holding time t2 for the two-stage sintering is 6h~12h; The sintering temperature T3 for the three stages is 500℃~700℃; The cooling rate v3 of the three-stage sintering is 1℃ / min~4℃ / min; The holding time t3 for the three-stage sintering is 2h~4h; The atmosphere for the first stage of sintering is air.

8. The method according to claim 6, characterized in that, At least one of the following conditions must be met: The nickel-manganese precursor includes at least one of nickel-manganese hydroxide, nickel-manganese oxide, and nickel-manganese carbonate; The lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium chloride; The molar ratio of the transition metal element in the nickel-manganese precursor to the lithium element in the lithium source is 2:(1.02~1.10). The amount of the first additive is 0.01 wt% to 1 wt% of the total mass of the nickel-manganese precursor and the lithium source; The amount of the second additive is 0.05wt% to 2wt% of the total mass of the nickel-manganese precursor and the lithium source; The first additive includes at least one of boron-containing compounds, niobium oxide, and tungsten oxide; The second additive includes at least one of aluminum oxide, yttrium oxide, cobalt oxide, zinc oxide, titanium oxide, chromium oxide, aluminum fluoride, magnesium fluoride, lanthanum fluoride, copper sulfide, aluminum chloride, and phosphorus-containing compounds; preferably, the phosphorus-containing compounds include at least one of aluminum phosphate, lithium phosphate, titanium phosphate, and lithium aluminum titanium phosphate.

9. A positive electrode plate, characterized in that, The lithium nickel manganese oxide cathode material includes any one of claims 1 to 5.

10. A lithium-ion battery, characterized in that, The cathode material includes any one of claims 1 to 5 or the cathode sheet as described in claim 9.

11. An electrical appliance, characterized in that, The lithium nickel manganese oxide cathode material according to any one of claims 1 to 5, the cathode sheet according to claim 9, or the lithium-ion battery according to claim 10.

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