Cathode active material for a lithium battery and lithium battery comprising the same

Abstract

The present invention relates to a cathode active material developed for high-energy lithium batteries. The cathode active material comprises lithium nickel manganese cobalt oxide (NMC) powder and a metal coating on the lithium nickel manganese cobalt oxide powder. The lithium nickel manganese cobalt oxide powder comprises a nickel content of 90 wt% or more and has an average secondary particle size ranging from 8 to 10 µm. The metal coating on the lithium nickel manganese cobalt oxide powder can be selected from a group consisting of zirconium, strontium, and a combination thereof. The invention also relates to a lithium battery that comprises the aforementioned cathode active material. The lithium battery according to the present invention demonstrates superior energy density and long-term stability.

Description

[0001] CATHODE ACTIVE MATERIAL FOR A LITHIUM BATTERY AND

[0002] LITHIUM BATTERY COMPRISING THE SAME

[0003] TECHNICAL FIELD

[0004] The present invention relates to a cathode active material developed to enhance the energy density and long-term stability of high-energy lithium batteries. More specifically, this invention focuses on an improvement of the cathode active material developed for high-energy lithium batteries, with an emphasis on preserving capacity retention even when higher nickel content is present. Additionally, the invention is applicable to lithium batteries that utilize the cathode active material of this invention.

[0005] BACKGROUND OF THE INVENTION

[0006] Rechargeable lithium-ion batteries (LIBs) serve as indispensable energy reservoirs in various domains, notably in the automotive sector, such as electric automobiles (EVs). An essential aspect of LIBs development for long-range EVs is to increase energy while maintaining high stability. Among the cathode materials available for LIBs, layered lithium transition metal oxides, specifically Li[NixMnyCoi-x-y]O2 (NMC), hold promise for EVs due to their advantageous characteristics. These materials offer high capacity derived from nickel, improved thermal stability attributed to manganese, and enhanced rate capability from cobalt. Commercially available NMC cathodes, such as LiNio.5Mno.3Coo.2O2 (NMC532), LiNio.6Mno.2Coo.2O2 (NMC622), and those with higher nickel content, like LiNio.sMno.1Coo.1O2 (NMC811), are widely used in EVs.

[0007] To achieve higher energy, LiNi0.9Mn0.05Co0.05O2 has emerged as a promising cathode material for long-range EVs. Nevertheless, nickel-rich layered cathodes have not yet been fully developed for practical applications due to several intrinsic drawbacks. First, the Ni2+and Ni3+ions in the layered structure are oxidized to form highly reactive Ni4+, which can react with the electrolyte at the electrolyte-cathode material interfaces, increasing charge transfer resistance and further generating gas evolution in the cell. Second, the homologous ionic radii of Ni2+and Li+lead to cation mixing between Li and transition metal slabs. Finally, anisotropic volume changes during the charge and discharge process result in secondary particle cracking, leading to rapid capacity fading. However, while higher nickel content in cathode materials can yield higher energy, it also presents significant challenges that need to be addressed. Some research focuses on addressing the intrinsic properties of the cathode active materials, as mentioned above, through various strategies such as coating and doping techniques. Furthermore, material properties like particle size and particle size distribution (PSD) significantly impact battery performance. For example, Sheu et al. explored the effects of diverse PSDs of LiCoCh on electrochemical performance and found that a smaller PSD improved cycling stability. Similarly, Nara et al. investigated the influence of broad and narrow PSDs of LiNii / 3Mm / 3Coi / 3O2 through sieving and designed an equivalent circuit for each PSD. Their findings confirmed that the secondary particle size distribution of the active cathode material affected Li-ion diffusion and the equivalent circuit, charge transfer resistance of the narrow PSD cell exhibiting fewer series circuits.

[0008] Below are examples of patent documents related to cathode active materials with high nickel content for lithium battery.

[0009] EP 3584862 Al discloses improvements in battery characteristics for all-solid lithium- ion batteries. The document describes a positive electrode active material comprising particles and the coated layers. The particles are represented by the following composition: LiaNibCocMndOe, in which: 1.0 < a < 1.05; 0.8 < b < 0.9; 1.8 < e < 2.2; and b + c + d = 1; wherein the coated layers are represented by LiNbCL, and wherein a specific surface area and a particle diameter of the positive electrode active material satisfy the following relationship: Y < 3.5 x X1, in which X is the particle diameter (pm) of the active material; and Y is the specific surface area (m2 / g).

[0010] US 2019 / 0190019 Al discloses a composite cathode active material for a lithium ion battery, which includes a nickel-rich lithium-nickel-based compound with a nickel content ranging from 50 to 100 mol % based on the total content of transition metals. The compound is coated with a film that contains a rare earth metal hydroxide and is applied to the surface of the nickel-rich lithium-nickel-based compound. The rare earth metal-containing salt in the coating comprises at least one element selected from yttrium, cerium, lanthanum, europium, gadolinium, scandium, and terbium.

[0011] EP 3836259 B 1 discloses a method for preparing a positive electrode active material for a secondary battery, which involves the following steps: preparing a lithium composite transition metal oxide including nickel, cobalt, and manganese, with nickel constituting 60 mol% or more of the total transition metal content; dry mixing and heat-treating the lithium composite transition metal oxide, a fluorine coating source, and a boron coating source to create a coating layer on the particle surface of the lithium composite transition metal oxide.

[0012] It is evident that the development of nickel-rich cathode active materials has become a prevailing trend in improving the performance of lithium-ion batteries. Nonetheless, the need to enhance capacity retention while increasing the nickel content persists. Specifically, there is a significant need for an extensively investigation into the impact of nickel content on the performance of NMC cathode materials.

[0013] SUMMARY OF THE INVENTION

[0014] An objective of the present invention is to provide a cathode active material for lithium batteries and the lithium batteries that incorporate this material. The cathode active material has been developed to improve energy density and long-term stability, especially for high-energy lithium batteries, making it particularly advantageous for cathode materials with a high nickel content.

[0015] In an aspect, the present invention relates to a cathode active material for a lithium battery, especially, the cathode active material which has a Formula:

[0016] LiNiaMnbCocZrdSreO2 where 0.9 < a < 1.0; 0 < b < 0.1; 0 < c < 0.1; 0 < d < 0.01; 0 < e < 0.01; and the sum of a, b, c, d, and e is 1.

[0017] The cathode active material comprises lithium nickel manganese cobalt oxide (NMC) powder and a metal coating on the lithium nickel manganese cobalt oxide powder. The lithium nickel manganese cobalt oxide powder comprises a nickel content of 90 wt% or more and has an average secondary particle size ranging from 8 to 10 pm, preferably from 8.5 to 9.5 pm with uniform particle size distribution. The metal coating on the lithium nickel manganese cobalt oxide powder can be selected from a group consisting of zirconium, strontium, and combination thereof.

[0018] Preferably, the metal coating on the lithium nickel manganese cobalt oxide powder has a zirconium content ranging from 0.001-0.01 wt%, more preferably 0.001-0.006 wt%, and a strontium content ranging from 0.001-0.01 wt%, more preferably 0.001-0.004 wt%.

[0019] The present invention can contribute to advancing the understanding of the relationship between nickel content, particle size uniformity, and battery performance, providing valuable insights for the design and optimization of cathode materials for next-generation lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Fig. 1 shows top-view FESEM images with different magnifications of NMC90 powder (Figs.l(a)-l(c)) and NMC80 powder (Figs. l(e)-l(g)), and the particle size distribution of NMC90 (Fig. 1(d)) and NMC80 (Fig. 1(h)).

[0021] Fig. 2 shows primary particle size distribution of NMC90 powder (Fig. 2(a)) and NMC80 powder (Fig. 2(b)).

[0022] Fig. 3 shows SEM-EDX element mapping images of NMC90 powder, where Fig. 3(a) for all overlaying elements, Fig. 3(b) for Ni, Fig. 3(c) for Co, and Fig. 3(d) for Mn, and FESEM image of NMC90 powder at top view (Fig. 3(e)).

[0023] Fig. 4 shows SEM-EDX element mapping images of NMC80 powder, where Fig. 4(a) for all overlaying elements, Fig. 4(b) for Ni, Fig. 4(c) for Co, and Fig. 4(d) for Mn, and FESEM image of NMC80 powder at top view (Fig. 4(e)).

[0024] Fig. 5 shows Rietveld refinement of NMC90 powder (Fig. 5(a)) and NMC80 powder (Fig. 5(b)).

[0025] Fig. 6 shows top-view FESEM images of:

[0026] NMC90 electrode at low-magnification (Fig. 6(a)), high-magnification (Fig. 6(b)), and

[0027] NMC80 electrode at low-magnification (Fig. 6(e)), high-magnification (Fig. 6(f)), and cross-sectional FESEM images of NMC90 electrode at low -magnification (Fig. 6(c)), high-magnification (Fig. 6(d)), and NMC80 electrode at low-magnification (Fig. 6(g)), high-magnification (Fig. 6(h)).

[0028] Fig. 7 shows cross-sectional SEM images of NMC90 powder at low-magnification (Fig. 7(a)), high-magnification (Fig. 7(b)), and SEM-EDX analysis of NMC90 powder (Fig. 7(c)).

[0029] Fig. 8 shows STEM image of NMC90 powder (Fig. 8(a)) and EDX line-scan overall region (Fig. 8(b)), and expansion region Fig. 8(c)).

[0030] Fig. 9 shows XPS depth profile of NMC90 powder in Zr 3d5 / 2 region (Fig. 9(a)) and Sr 3d5 / 2 region (Fig. 9(b)).

[0031] Fig. 10 shows voltage profiles in half-cell coin cell configuration at 0.1C within the voltage range of 3.0-4.3 V of NMC90 and NMC80.

[0032] Fig. 11 shows Galvanostatic intermittent titration technique (GITT) curves vs. time of NMC90 (Fig. 11(a)) and NMC80 (Fig. 11(b)), the relationship of the cell voltage and r1 / 2for the titration curves of NMC90 (Fig. 11(c)) and NMC80 (Fig. 11(d)). Fig. 12 shows the lithium diffusivity from GITT measurement of NMC90 and NMC80 during charging and discharging as a function of the cell potential with various setting parameters of VM and A, whereby,

[0033] Fig. 12(a): VM from crystallographic and A from surface area of the electrode,

[0034] Fig. 12(b): VM from true density of the active material and A from surface area of the electrode,

[0035] Fig. 12(c): VM from crystallographic and A from surface area of the active material,

[0036] Fig. 12(d): VM from true density of the active material and A from surface area of the active material,

[0037] Fig. 12(e): VM from true density of the electrode and A from surface area of the electrode, and

[0038] Fig. 12(f): VM from true density of the electrode and A from surface area of the active material.

[0039] Fig. 13 shows electrochemical performance in cylindrical configuration, whereby,

[0040] Fig. 13(a): discharge capacity based on active cathode material at various current density from 0.1C to 5.0C,

[0041] Fig. 13(b): potential drop from rate capability of NMC90 and NMC80 cells,

[0042] Fig. 13(c): capacity retention for stability performance, and

[0043] Fig. 13(d): accumulated energy density based on the active material level for long-term cycling performance.

[0044] Fig. 14 shows rate capability in cylindrical configuration at various current density from 0.1C to 5.0C within the voltage range of 3.0-4.2 V; voltage profiles at each C-rates of NMC90 (Fig. 14(a)) and NMC80 (Fig. 14(b)), and discharge capacity based on cell (Fig. 14(c)).

[0045] Fig. 15 shows long-term cycling performance with the window potential of 3.0-4.2V at 0.5C CCCV-charge and 1.0C CC-discharge; discharge capacity based on cell (Fig. 15(a)) and active cathode material (Fig. 15(b)), voltage profiles of NMC90 (Fig. 15(c)) and NMC80 (Fig. 15(d)), voltage differential of charge and discharge curves (Fig. 15(e)), and accumulated energy density based on the cell level (Fig. 15(f)).

[0046] Fig. 16 shows voltage profiles at check-up step (0.1C) for long-term cycling with cycle numbers of the 3rd, 56th, 109th, 212th, and 515thcycles of NMC90 (Figs. 16(a) and 16(c)) and NMC80 (Figs. 16 (b) and 16(d)). Fig. 17 shows dQ / dV plots at 0.1C within the potential range of 3.0-4.2 V for long-term cycling performance of NMC90 (Figs. 17(a) and 17(c)), and NMC80 (Figs. 17(b) and 17(d)).

[0047] Fig. 18 shows dQ / dV plots at 0.1C within the voltage range of 3.0-4.3 V in half-cell coin cell of NMC80 (Fig. 18(a)) and NMC90 (Fig. 18(b)) and the lithium diffusivity from GITT measurement of NMC90 and NMC80 before and after 1,000 cycles at 0.1C (Fig. 18(c)).

[0048] Fig. 19 shows the cumulative capacities obtained from the Atlung Method for Intercalant Diffusion (AMID) before cycling of NMC90 (Fig. 19(a)) and NMC80 (Fig. 19(b)) and after cycling of NMC90 (Fig. 19(c)) and NMC80 (Fig. 19(d)) for 3.0-4.3 V with C-rates from 5C to C / 160 in half-cell coin cell configuration.

[0049] Fig. 20 shows primary particle radius distribution of NMC90 powder (Fig. 20(a)) and NMC80 powder (Fig. 20(b)) and Li+diffusion coefficient of NMC90 and NMC80 with various primary particle sizes before cycling (Fig. 20(c)) and after cycling (Fig. 20(d)).

[0050] Fig. 21 shows example of the Nyquist plot with equivalent circuit for capacitance measurement (Fig. 21(a) where dot line is impedance data and solid line is EIS fitting curve) and specific capacitance of NMC80 and NMC90 cells for 10 cycles (Fig. 21(b)).

[0051] Fig. 22 shows the structural change from refinement results for (left) NMC90-graphite and (right) NMC80-graphite were operated in pouch cells; voltage profiles (Figs. 22(a) and 22(e)), lattice parameter c (Figs. 22(b) and 22(f)), lattice parameter a (Figs. 22(c) and 22(g)), and unit cell volume during cycling (Figs. 22(d) and 22(h)).

[0052] Fig. 23(a) shows the voltage profile of NMC90-graphite cell during the step formation and the first cycle with the upper cutoff voltage of 4.5V in 18650 cylindrical configuration and Fig. 23(b) shows the corresponding gas evolution as a function of time of NMC90-graphite cell detected by in situ DEMS measurement.

[0053] Fig. 24(a) shows the voltage profile of NMC80-graphite cell during the step formation and the first cycle with the upper cutoff voltage of 4.6V in 18650 cylindrical configuration and Fig. 24(b) shows the corresponding gas evolution as a function of time of NMC80-graphite cell detected by in situ DEMS measurement.

[0054] Fig. 25 shows temperature profiles from impact test following UN38.3 standard of

[0055] NMC90. DETAILED DESCRIPTION

[0056] The features of the present invention will now be described in more detail through an illustrative embodiment. It should be noted that this example is provided for illustrative purposes and should not be interpreted as limiting the scope of the invention.

[0057] Unless otherwise specified, the aspects depicted herein shall also encompass their application to other aspects of the present invention.

[0058] Unless otherwise indicated, technical and scientific terms used herein have meanings that are commonly understood by a person skilled in the relevant field.

[0059] The term "about" or “approximate”, as used throughout the present invention, indicates that the values presented or disclosed herein may exhibit slight variations or deviations. These variations or deviations may arise from errors in the equipment or methods employed to determine such values.

[0060] The terms "consist(s) of," "consisting of," "consisted of," "comprise(s)," "comprising," "comprised," "has / have / having," "include(s)," "including," and "included" used herein are open-ended verbs. For instance, any methods that "consist of," "comprise," "have," or "include" one or more components or steps are not limited solely to those mentioned components or steps but also encompass additional components or steps not explicitly stated.

[0061] The terms "a," "an," and "the," when used to refer to a singular form, are intended to encompass the plural form of the noun, unless otherwise specified.

[0062] Any tools, devices, methods, materials, or chemicals mentioned herein, unless specified otherwise, refer to the tools, devices, methods, materials, or chemicals generally used or practiced by a person skilled in the relevant field unless explicitly designated as special or exclusive tools, devices, methods, or chemicals for the present invention.

[0063] While higher nickel mole ratios are traditionally associated with greater energy capacities, they often come at the cost of stability. The investigation of the inventors of this invention reveals an inventive finding: particle size uniformity plays a more crucial role in determining battery performance than nickel content alone. Notably, the cathode active material of the present invention excels in terms of energy density and long-term stability, primarily due to its improved particle uniformity. Furthermore, enhanced particle size uniformity can alleviate rate capability limitations, even in the presence of higher nickel content. A cathode active material in the present invention comprises a lithium nickel manganese cobalt oxide (NMC) powder and a metal coating on the lithium nickel manganese cobalt oxide powder. Preferably, the NMC powder comprises a nickel content of 90 wt% or more and has an average secondary particle size ranging from 8 to 10 pm. The metal coating on the NMC powder is selected from a group consisting of zirconium, strontium, and a combination thereof.

[0064] The cathode active material is described by the Formula:

[0065] LiNiaMnbCocZrdSreCh where 0.9 < a < 1.0; 0 < b < 0.1; 0 < c < 0.1; 0 < d < 0.01; 0 < e < 0.01; and the sum of a, b, c, d, and e is 1.

[0066] According to a preferred embodiment, the lithium nickel manganese cobalt oxide powder has the average secondary particle size ranging from 8.5 to 9.5 pm and exhibits uniform particle size distribution. More preferably, the lithium nickel manganese cobalt oxide powder has the average secondary particle size ranging from 8.7 to 9.5 pm.

[0067] For the present invention, enhancing the electrical performance of the battery is achievable by reducing the secondary particle size of the lithium nickel manganese cobalt oxide powder within the said specified range. This reduction shortens the distance for lithium-ion diffusion, leading to improved high-rate capability. Moreover, the cathode active material with a narrow particle size distribution offers a larger surface area of reactive material per unit volume. As a result, even at high discharge rates, the energy density of the battery remains comparable to that of the cathode active material with a wide particle size distribution.

[0068] According to a preferred embodiment, the lithium nickel manganese cobalt oxide powder has an average primary particle size ranging from 0.4 to 0.6 pm, preferably 0.45 to 0.55 pm.

[0069] The metal coating on the lithium nickel manganese cobalt oxide powder may be a metal oxide compound, preferably, the compound which is selected from zirconium oxide, strontium oxide, and a combination thereof. Preferably, a combination of zirconium oxide and strontium oxide. More preferably, the metal coating on the lithium nickel manganese cobalt oxide powder comprises zirconium and strontium.

[0070] With respect to the metal oxide coating on the cathode active material, this invention ensures that the metal oxide does not alter the structure of the active material and has minimal impact on the electrochemical reactions within the system. Moreover, the metal oxide coating on the lithium nickel manganese cobalt oxide powder serves to protect the active material from direct contact with the electrolyte, thereby preventing undesirable parasitic reactions. Consequently, the battery incorporating this cathode active material exhibits long-term stability.

[0071] According to an embodiment, the metal coating on the lithium nickel manganese cobalt oxide powder has a zirconium content ranging from 0.001-0.01 wt%, preferably from 0.001- 0.006 wt% and a strontium content ranging from 0.001-0.01 wt%, preferably from 0.001-0.004 wt%.

[0072] The presence of the metal coating, whether on the particle surface or within the particles, enhances particle strength. Consequently, the lithium battery, as described in this invention, showcases superior long-term stability due to the metal coating's ability to prevent particle cracking resulting from prolonged battery cycles.

[0073] In another aspect, the present invention encompasses a cathode for a lithium battery comprising the aforementioned cathode active material, and a lithium battery that employs this cathode material. The lithium battery featuring this cathode active material demonstrates high energy and long-term durability.

[0074] To provide a more comprehensive understanding of the present invention, examples of the cathode active material will be described in detail. However, it is important to emphasize that the scope of the present invention is not limited by these examples, and the accompanying illustrations are purely for illustrative purposes, not intended to impose any restrictions on the invention.

[0075] Examples

[0076] 1. Preparation and characterization

[0077] 1.1 Preparation of Li-ion cells

[0078] Chemicals and materials

[0079] The commercial LiNio.sCoo.1Mno.1O2 (S8-2922120301, Gelon LIB group, China) and LiNi0.9Co0.05Mn0.05O2 (DUJ90-2023010602, Gelon LIB, China) were used as active cathode materials. Carbon black (Super P, Gelon LIB group, China) and poly vinylidene fluoride (PVDF, Gelon LIB group, China) were utilized as conductive additives and binders at the cathode side, respectively. N-methyl pyrrolidinone (NMP, Gelon LIB group, China) as a solvent for the cathode coating.

[0080] 18650 cylindrical cell fabrication

[0081] For electrode preparation in an 18650 cylindrical configuration, all the processes were performed in a dry room (dew point of -40°C). The NMC80 and NMC90 cathode slurry were prepared by mixing the active material, carbon black, and PVDF binder with a weight ratio of 95.2:2.4:2.4 in NMP and stirred overnight. For the anode electrode, graphite, carbon black, and carboxymethyl cellulose (CMC) / styrene-butadiene rubber (SBR) with a weight ratio of 95.3:1.0:1.2:2.5 were mixed in water and stirred overnight. The homogenous cathode and anode slurry was coated on Al and Cu foil, respectively, using a roll-to-roll automatic coating machine and dried in the vacuum oven at 120°C overnight. The cathode and anode thicknesses are ca. 165 and 228 pm, respectively. The active mass loading at positive and negative electrodes was ca. 32.5 and 22.5 mg / cm2, respectively. The positive and negative electrodes were pressed at 6 and 2 tons, respectively. Then, the electrodes were processed through slitting, cutting, and winding with a tri-layer polypropylene / polyethylene / polypropylene (PP / PE / PP) used as a separator. After winding, the jelly rolls were put into the case and welded with the cap. Finally, the electrolyte with 5.4 g of IM LiPFe in the mixture of 30 wt% fluoroethylene carbonate (FEC, Gelon LIB group) and 70 wt% of commercial electrolyte EJN02 (Gelon LIB group) was injected into the cell. The N / P ratio, the capacity ratio of the negative to positive electrodes, was 1.25.

[0082] 1.2 Characterization of Li-ion cells

[0083] Physicochemical characterization

[0084] Field-emission scanning electron microscopy (FESEM, JOEL JSM-7610F, Japan) with Energy-dispersive X-ray spectroscopy (EDX) characterized the materials' morphology, elemental distribution, and composition. The elemental composition was investigated by Wavelength-Dispersive X-ray Fluorescence Spectrometer (WDXRF, Bruker S8 Tiger). The crystallographic structure of the materials was analyzed by X-ray diffraction (XRD, Bruker New D8 Advance diffractometer, Germany) at the 29 of 10° - 90° through Cu Ka1.54056 A and the XRD Rietveld refinement analysis was studied by Rietica 4.0. The surface area of cathode active material and electrode were measured from the amount of N2 adsorbed via Brunauer-Emmett- Teller analysis (BET, 3Flex, Micromeritics Instrument Crop.).

[0085] Galvanostatic intermittent titration technique

[0086] The galvanostatic intermittent titration technique (GITT) measurement was investigated in a half-cell coin cell configuration. The cathode electrode composition is the same as in the cylindrical configuration. The electrode was punched into a coin shape, 1.13 cm2, with an active mass loading of 15-18 mg cm'2. NMC80 and NMC90 electrodes were fabricated in a CR-2032 coin cell in an Ar- filled glove box (MBRAUN UNILAB, Germany). For GITT measurement, the cells applied the current density at 0.1C for 10 min during the charge and discharge process with a relaxation time of 30 min. The lithium-ion coefficient was calculated following Equation (1). where Dsis the chemical diffusion coefficient, r is the duration time of the current pulse, ms is the mass of active material, MB is the molecular weight of active material, VM is the molar volume of active material, A is the contact area, AESis the steady-state voltage change, and AETis the voltage change during a constant current pulse. This equation assumes that VM does not change during the electrochemical evaluation. For A, the contact area can be calculated from the surface area of the active material and the cathode electrode by BET. For VM, the molar volume can calculate in three routes; i) from the true density of active material, ii) from the true density of the electrode, and iii) from crystallographic (lattice constant a and c) of active material, which is calculated by XRD Rietveld refinement technique.

[0087] 1.3 Electrical performance

[0088] The electrochemical performance, including rate capability and stability, was studied by galvanostatic charge / discharge (GCD) using the battery tester (Neware, Gelon, Hong Kong). For the formation protocol, the cells were charged by a multi-step constant current (MSCC) 5 (C / 40, C / 20, C / 15, C / 12.5 followed by a constant-current (CC) discharge for 2 cycles with a voltage range of 3.0 - 4.3 V. Then, the cell was tested at 0.1C using constant-current and constant-voltage (CCCV) charging and CC discharging between 3.0 - 4.2 V for capacity determination.

[0089] 1.4 Atlung Method for Intercalant Diffusion technique

[0090] The fresh and cycled cathode electrodes with one side coating were coupled with a Ei chip in the CR-2032 coin cell. For the first cycle, the cells were tested with the window potential of 3.0-4.3V at C / 20. Then charged to 4.3 V vs. Li+ / Li at C / 40 following discharge at 5C, 3C, 2C, 162 1C, C / 2.5, C / 5, C / 10, C / 20, C / 40, C / 80, and C / 160, resting at OCV for 15 minutes at each C-rate from 4.3 to 3.0V. Finally, the cells were charged at C / 40 to 4.3V. The lithium-ion coefficient was calculated following Equation (2) based on spherical particles. where A = 3, B = 5, a cot(ai) = 1, r is average spherical primary particle radius obtained from SEM, n is effective rate, 3600n is effective discharge time (in seconds) for each n, cmax is the maximum obtainable capacity, c / cmax is the fractional capacity achieved at each rate, and Dcis the Li chemical diffusion coefficient. Dcis conducted after fitting through the Atlung equation.

[0091] 1.5 Capacitance measurement

[0092] The cells were tested in the CR-2032 coin cell. For the conditioning step, the cells were using CC charge at 0.1C for 1 h, then were deep-discharged at 0.1C to 2.5V vs. Li+ / Li in CV mode for 6 h, followed by potential-controlled EIS (PEIS) from 100 kHz to 100 mHz with an amplitude of 15 mV for 10 points per decade. For the next cycle, the cells were charged at 0.5C to 4.3V in CC mode and discharged to 2.5V in CV mode for 6 h, followed by PEIS, repeating these steps for 9 cycles.

[0093] 1.6 In operando X-ray diffraction of pouch cells

[0094] The cathode structural change in the crystal lattice level during the charging and discharging process was studied through XRD (Bruker New D8 Advance diffractometer, Germany) collaborated Metrohm Autolab electrochemical workstation (PGSTAT 302 N) in a single-layer pouch cell configuration. The Rietveld refinement analysis was studied by TOPAS software, version 5.0 (Bruker AXS). This experiment was investigated at the current density of 10 mA with a window potential of 3.0-4.3 V and collected the diffraction patterns every 6 minutes at the 29 of 7° - 55° with the Mo Karadiation.

[0095] 1.7 In situ differential electrochemical mass spectrometry of jelly -roll cylindrical cells

[0096] A differential electrochemical mass spectrometer (DEMs, Hiden, HPR-40, UK) with QGA professional software was applied to study the gas evolution in the cell. The working pressure was < 5xl0-8Torr with 70 eV for the ionization of all species and an emission current of 500 / / A. The jelly -roll cells were set in the test tube with the excess electrolyte and enclosed with a septum, where the samples were tested in an Ar-filled glovebox. This experiment investigated the formation step and the first cycle with abuse at high voltage (up to 4.6V).

[0097] 1.8 Safety testing of large-scale cylindrical cells

[0098] The safety analyses were tested in the cylindrical cells after the formation step following the UN38.3 standard on Guangdong Bell Experiment Equipment's (China) tester. Five cells were 200 charged at 4.2V (100%SOC) for altitude, thermal, shock, and short circuit tests, which tested the same cells for all conditions. In addition, five cells were charged at 50%SOC (3.6 V) for the impact test. 2. Experimental results

[0099] 2.1 Study on physicochemical properties

[0100] The investigation of NMC80 and NMC90 powders' morphology was distinguished through Field Emission Scanning Electron Microscope (FESEM), as illustrated in Fig. 1. Both powders presented secondary particles, which are the result of the aggregation of numerous primary particles, as illustrated in Figs. 1(b) and 1(f). Primary particle sizes in NMC80 and NMC90 were similar, approximately 500+50 nm, which was confirmed by the primary particle size distribution in Fig. 2. NMC80 powder displayed varying particle sizes compared to NMC90 powder, which had uniform particle sizes, as shown in low magnification FESEM images in Figure 1(a) and 1(e). This was confirmed by particle size distribution curves in Figs. 1(d) and 1(h), where NMC90 powder demonstrated a narrow distribution with an average particle size of 9.1 ± 0.4 pm. In contrast, NMC80 powder had a wide distribution with an average particle size of 13.6 ± 3.7 pm. Note, all particle size and distribution were determined using ImageJ software. The elemental composition of NMC90 and NMC80 powder was analyzed using FESEM-EDX, as illustrated in Figs. 3 and 4, respectively. The detailed elemental compositions from FESEM- EDX are given in Table 1.

[0101] Table 1: Elemental composition of NMC80 and NMC90 powders

[0102] Elemental composition (wt%)

[0103] Element > NMC80 powder NMC90 powder

[0104] Co 10.7 5.2

[0105] Mn 9.0 4.7

[0106] > where NMC80 powder includes 80.3% Ni, 9.0% Mn, and 10.7% Co, while NMC90 powder consists of 90.1% Ni, 4.7% Mn, and 5.2% Co. The structural material of both samples was carried out through X-Ray Diffraction (XRD) and Rietveld refinement (see Fig. 5 and Table 2). The XRD patterns of NMC80 and NMC90, in Figs. 5(a) and 5(b), respectively, represent the R-3m space group with hexagonal crystallographic patterns. The refinement results are given in

[0107] Table 2. Table 2: Rietveld refinement results of XRD patterns of NMC80 and NMC90 powder

[0108] Parameters NMC80 NMC90

[0109] Lattice constant a (A) 2.8722(0) 2.8751(0)

[0110] Lattice constant c (A) 14.2051(0) 14.2029(0)

[0111] V (A3) 101.4855(7) 101.6748(6) n Ni in Li sites 1.78% 1.24%

[0112] RB 0.75 1.30

[0113] Rwp2.05 2.74

[0114] Table 2 reveal cation mixing for NMC90 and NMC80 with percentages of 1.24% and 1.78%, respectively, which are acceptable due to being less than 5%. BET surface area, pore volume, and pore size of NMC80 and NMC90 electrodes are also listed in Table 3.

[0115] Table 3: BET surface area, pore volume, and pore size of NMC80 and NMC90 electrodes

[0116] BET

[0117] Sample -

[0118] Surface area Pore volume Pore size

[0119] (m2 / g) (cm3 / g) (nm)

[0120] NMC80 powder 0.2876 0.001082 8.8497

[0121] NMC90 powder 0.2678 0.001195 9.3782

[0122] NMC80 electrode 1.0883 0.003249 11.9419

[0123] NMC90 electrode 1.0347 0.002563 9.9088

[0124] The automatic roll-to-roll coating machine was employed for negative and positive electrode production in 18650 cylindrical configuration cells. Fig. 6 displays the top-view and cross sectional FESEM images of NMC90 and NMC80 electrodes, which showed well -packed NMC particles on the electrode with CB and PVDF. Notably, NMC90 particles exhibited well-ordered arrangement and uniform particle size compared to NMC80. Both electrodes' pore volume and surface area were analyzed using BET surface area analysis, presented in Table 3. The NMC80 electrode had a larger pore volume than the NMC90 electrode (0.0032 and 0.0026 cm3g-1, respectively), and had a higher surface area (1.0883 and 1.0347 m2g-1), indicating that the non-uniform particle size resulted in more void space between particles in the electrode.

[0125] Notably, the active materials for electrode fabrication are commercial grade. It was found additional material coating on NMC90 powder, including Zr and Sr elements, with 0.59 and 0.31 wt%, respectively, as presented in Table 4.

[0126] Fig. 7 displays a cross-sectional SEM image of NMC90 powder with EDX-SEM element mapping for six points. Sr and Zr can be detected at the surface of the NMC90 particle (see Table 5). From the EDX-TEM line scan in Fig. 8, Sr and Zr elements can be found only on the surface of the NMC90 particle. Additionally, XPS depth profiling results of NMC90 powder in Zr 3d5 / 2 and Sr 3d5 / 2 regions agree with EDX-SEM element mapping, EDX-TEM line scan, and WDXRF results. Both elements are found on the surface, as illustrated in Fig. 9. Regardless, this coating has a trace amount without additional elements doping in the NMC structure.

[0127] Table 4: WDXRF results of NMC90 powder

[0128] XRF%

[0129] Element

[0130] NMC 90 powder

[0131] Ni 90.070

[0132] Co 4.759

[0133] Mn 4.269

[0134] Zr 0.593

[0135] Sr 0.309 Table 5: Elemental composition of NMC90 at each point from SEM-EDX analysis

[0136] Elemental composition at each point (At. %)

[0137] Element

[0138] 1 2 3 4 5 6

[0139] Ni 89.4 90.1 90.2 90.1 90.3 90.6

[0140] Co 5.0 5.0 5.1 4.7 5.1 5.1

[0141] Mn 4.6 4.9 4.7 4.7 4.6 4.4

[0142] Zr 0.8 - - 0.5 - -

[0143] Sr 0.2 - - - - -

[0144] 2.2 Study on electrochemical properties

[0145] To assess the practical capacity of the cells, electrochemical performances were first conducted in a half-cell coin cell configuration (CR2032). The potential profiles of NMC80 and NMC90 were examined in the potential range of 3.0-4.3 V vs. Li / Li+at 0.1C, and their specific discharge capacities were 185.3 and 213.8 mAh g1, respectively (see in Fig. 10). GITT measurement was then studied to investigate the Li diffusivity of the cathode materials, and both samples exhibited a linear relationship between potential and r1 / 2, as presented in Fig. 11. The lithium diffusivity of NMC80 and NMC90 during charging and discharging at 0.1C with the upper cutoff voltage at 4.3V vs. Li / Li+was presented in Fig. 12. As a result, the particle size distribution did not affect lithium-ion diffusion at slow current density. The diffusivity of the materials will further ascribe in the next section of the rate capability test and GITT results after stability test.

[0146] Full-cell tests were performed on both samples in 18650-cylindrical configuration with the n / p ratio of 1.25 to demonstrate practical applications. The electrochemical performances for both samples were conducted following a formation step and capacity determination protocol (see detailed in the experimental section). The cells underwent electrochemical performances, including rate capability and stability tests with a cutoff voltage between 3.0 to 4.2 V. The testing protocol for the rate capability test involved fixed CCCV charging at 0.5C and various CC discharging at 0.1, 0.25, 0.5, 0.75, 1.0, 2.0, 3.0, 4.0, and 5.0C, followed by turning back to 0.1C. The specific discharge capacity of both samples was measured and plotted in Fig. 13(a). The NMC90 / graphite cell presented larger discharge capacity at all C-rates, especially at high C-rates, such as 4.0 and 5.0C, higher than 1.5 and 50 times the NMC80 cell, respectively. The discharge profiles of NMC90 and NMC80 at each C-rates were also shown in Figs. 14(a)-14(b). In addition, the discharge capacity based on the cell for both samples was presented in Fig. 14(c). The NMC90 cell provided a lower potential drop than NMC80 at the same current density, especially at 5.0C, suggesting that the uniform particles mitigated the internal resistance (IR) of the cell, as presented in Fig. 13(b) and listed in Table 6.

[0147] Table 6: IR drop from rate capability at various current density from 0.1C to 5.0C within the voltage range of 3.0-4.2 V of NMC90 and NMC80 cells

[0148] IR drop (V)

[0149] NMC90 NMC80

[0150] 0.1C 0.0191 0.0284

[0151] 0.25C 0.0377 0.0631

[0152] 0.5C 0.0746 0.1196

[0153] 0.75C 0.1152 0.1937

[0154] 1.0C 0.1348 0.2572

[0155] 2.0C 0.2743 0.3908

[0156] 3.0C 0.3986 0.5055

[0157] 4.0C 0.5474 0.6640

[0158] 5.0C 0.7151 0.9495

[0159] 0.1C (switch back) 0.0185 0.0213

[0160] The rate capability results imply that the uniform particle size of NMC90 can provide a better Li+diffusion pathway leading to outstanding discharge capacity even at a high C-rate and reducing IR drop in the battery. To evaluate the stability of the battery, an asymmetric protocol was used, which involved CCCV charging at 0.5C and CC discharging at 1.0C within a potential window of 3.0-4.2 V. Long-term cycling performance was assessed by including a check-up protocol with CCCV charging and CC discharging at 0.1C. Fig. 13(c) shows that NMC80 and NMC90 cells exhibited capacity retentions of 53.9% and 73.6%, respectively, after 1,000 cycles at 1.0C.

[0161] At the cell level, NMC90 and NMC80 had discharge capacities of 1,448 and 1,054 mAh, respectively, after 1,000 cycles (Fig. 15(a)). At the active material level, NMC90 and NMC80 demonstrated specific capacities of 138.5 and 90.4 mAh g1after 1,000 cycles (Fig. 15(b)). The voltage profiles at the 1st, 500th, and 1000thcycles of NMC90 and NMC80 cells are presented in Figs. 15(c) and 15(d). The voltage differences between charge and discharge during cycling are displayed in Fig. 15(e). After 1,000 cycles, delta V in the case of NMC90 is 0.58 V, while delta V of NMC80 is 0.76 V. The NMC90 cell illustrates better stability performance with lower polarization than the NMC80 cell suggesting that the uniform particles cooperating with a surface coating enhance cell stability with lower kinetic hindrance, even with high nickel content in the layered oxide material. Furthermore, NMC90 delivers an accumulation energy density of 558 kWh kg-1NMC, 22% higher than NMC80, as depicted in Fig. 13(d). The accumulated energy density based on the cell level for both samples is shown in Fig. 15(f).

[0162] In addition, potential profiles of both samples during cycling were examined in the check-up steps, and the results are shown in Fig. 16. The NMC90 / graphite cell showed a capacity drop from 2,090 to 1,837 mAh (203 to 179 mAh g-1) from the 3rdto the 515thcycle, while the NMC80 / graphite cell decreased from 2,175 to 1,902 mAh (185 to 162 mAh g-1). The voltage differences between the charge and discharge curves at the check-up steps in Figs. 16(c)- 16(d) indicated that the NMC80 cell had slightly higher polarization than the NMC90 cell. To better understand this effect, the dQ / dV plots at 0.1C were examined, as shown in Fig. 17.

[0163] Both samples displayed identical phase transformation curves for NMC materials. Notably, at the Cf> to LiCxpeak, which corresponds to kinetic hindrance in the cell (Figs. 17(c)- 17(d)), the peak of NMC90 shifted to the right-hand side by O.O338V, which is less than the shift observed in NMC80 (0.0517 V). This finding suggests that the uniform particle of NMC90 can provide better Li+diffusion with lower kinetic limitation. Therefore, the results suggest that the particle size distribution of nickel-rich layered oxide cathode materials is a crucial part of the electrochemical performance, with the narrow distribution of NMC90 demonstrating higher energy density and better retention. All cells were disassembled after 1,000 cycles to examine the Li diffusivity via the GITT technique. Figs. 18(a)-18(b) illustrate dQ / dV plots of NMC80 and NMC90 cells, respectively, with three-phase transition regions, including Hl-M, M-H2, and H2-H3. The chemical diffusion coefficient of both samples before and after cycling is presented in Fig. 18(c). Both samples displayed lower lithium diffusivity than the cells before cycling, especially in the NMC80 cell, which is less than one order of magnitude.

[0164] Note that the GITT measurement has diverse parameters and assumptions based on dense planar electrodes for calculation. The Atlung method becomes an optional measurement for lithium diffusivity computation (see the detail in the experimental section). The cumulative capacities from 5C to C / 160 of NMC80 and NMC90 cells before and after cycling are shown in Fig. 19.

[0165] The primary particle radius distribution of NMC90 and NMC80 is depicted in Figs. 20(a)-20(b), respectively. Both samples exhibited an analogous average radius of 0.25 ± 0.03 pm. Di.i+values obtained from all ranges of particle radius are demonstrated in Figs. 20(c)-20(d). Before cycling, Du+ values of NMC80 and NMC90 cells were practically the same (DLi+,avg,NMC90 = 9.96 x 10’14cm2s and DLi+,avg,NMC80 = 9.86 x 10’14cm2s4). After 1,000 cycles, the lithium diffusion coefficient of NMC90 outperformed NMC80 with a higher order of magnitude (DLi+,avg,NMC90 = 1.49 x 1044cm2s4and DLi+,avg,NMC80 = 6.98 x 105cm2s4). Interestingly, lithium diffusivity from GITT and Atlung techniques exhibit the same trend suggesting that Du+ from the GITT method is still reliable even with their several assumptions. From the results, the narrow particle size distribution effectively improves the lithium-ion transport after long-term cycling.

[0166] The formation of secondary particle cracking upon cycling influences poor battery life span. Capacitance measurement was applied to investigate microcracking during cycling using in situ EIS without post-mortem of the cell (see in the experimental section). The cells were cycled for 10 cycles to collect the impedance data in each cycle for this analysis. Fig. 21(a) presents the example of the Nyquist plot with an equivalent circuit with a fitting curve for capacitance measurement. The specific capacitance of NMC80 and NMC90 is shown in Fig. 21(b). At the conditioning step, the capacitance of NMC80 and NMC90 is 0.120 and 0.110 F g4, respectively. After 10 cycles, NMC90 has a capacitance of 0.144 F g4. On the contrary, NMC80 exhibits a higher 43% capacitance (0.254 F g4), indicating that NMC80 has a larger surface area of particle cracking, leading to more electrolyte penetration to the active material and a consequence of further parasitic reaction.

[0167] 2.3 In Operando XRD

[0168] The change of cathode structure in crystal lattice level through full-cell pouch cells was studied through an in operando XRD measurement. After the formation step, the cells were operated at 10 mA with the upper cutoff voltage of 4.3V for 2 cycles. The Rietveld refinement was applied to compute lattice parameters during the charging and discharging. Fig. 22 presents the structural change from the refinement results, including a-axis and c-axis lattice parameters and unit cell volume for NMC90 and NMC80 cells. During the first charging, the a-axis value changes of NMC80 and NMC90 are 0.80 and 0.79%, respectively. Unit cell volume changes by 2.64 and 4.45% for NMC80 and NMC90, respectively, which also relate to the c lattice parameter.

[0169] For the lattice parameter along the a-axis, both samples display a reduction and expansion in the a-value during the discharge and charge processes, and the change in unit cell volume is identical in aspect to the a-lattice.

[0170] For the c-axis lattice parameter, both samples exhibit increasing c-values at the initial charging process because the oxidized transition metals enlarge interslab repulsion during lithium extraction from cathode material.

[0171] Towards the end of the charging process, a considerable amount of lithium ions exit the lithium layer, leading to a sudden reduction in the c-value, which reduces the electrostatic repulsion between the transition metal layers.

[0172] During discharging, the c-axis lattice parameter immediately enlarges and sluggishly lowers through lithiation at the cathode side. The c lattice value changes of NMC80 and NMC90 at the first charging process are 1.73 and 3.48%, respectively. The greater c-axis parameter change indicates a larger amount of lithium extraction from the lithium slab leading to higher capacity in the NMC90 cell. Previous studies have consistently found that excessive shrinkage in the c-direction negatively affects structural integrity and leads to significant capacity deterioration.

[0173] However, NMC90 exhibits a greater change in c lattice value but outstanding electrochemical performances. These findings indicate that the anisotropic volume change does not solely dictate the electrochemical performance. Additional factors, including particle size distribution and surface treatment, play crucial roles in maintaining capacity retention. 2.4 Real-time gas detection of electrolyte decomposition products via a mass

[0174] Typically, nickel-rich layered oxide cathode materials confront the severe parasitic reactions from electrolyte composition under high voltage conditions during the charging process, directly affecting gas evolution in the cell and limiting lithium diffusion at the active material surface. In situ DEMs measurement was employed to investigate the gas evolution of the jelly-roll cells during the formation step to abusing at high voltage for the first cycle. The potential profile for the first two cycles of NMC90 and NMC80 cells are depicted in Figs. 23(a) and 24(a), respectively, in combination with the cumulative gas evolution in Figs. 23(b) and 24(b). At the beginning of the first charge, the H2 signal rapidly increases due to the reduction of FEC to form the SEI layer on the graphite electrode.

[0175] For the second cycle with abusing voltage up to 4.5V, the gas species, including H2, CO2, and CO, are found during this cycle, significantly increasing at a higher 4.3V which attribute to the decomposition of EC, DEC, and FEC. Notably, the generation of CO2 is a favorable occurrence resulting from the ring-opening of EC on the surface of the NMC cathode. Additionally, CO is produced through the reduction of DEC and EC electrolytes. During the second cycle at 4.5V, the NMC80 cell detects a CO2 signal 1.75 times higher than the NMC90 cell. This observation suggests that higher void space in the electrode with non-uniform particles influences electrolyte penetration into the cathode electrode. Consequently, this leads to more pronounced side reactions and a significant increase in gas evolution within the system.

[0176] Furthermore, the reduction of protic oxidation species in the electrolyte is crucial for the formation of H2. Moreover, the reduced form of residual H2O in the electrolyte at the graphite electrode also impacts H2 generation in the cell. DEMs results reveal that the NMC80 cell generates higher gases suggesting it occurs in more parasitic reactions than NMC90. This happening agrees with the capacitance result that NMC80 has a more elevated active material surface area upon cycling. The results obtained from DEMs demonstrate that a narrow particle size distribution and surface coating positively influence gas evolution during cycling and further prevent parasitic reactions, even at high voltage.

[0177] 2.5 Safety test

[0178] Maintaining transportation safety is crucial for Li-ion batteries, particularly in practical applications. In this invention, the UN38.3 standard is applied to address safety concerns (see experimental details). NMC90 cells successfully passed the safety evaluation for altitude, thermal, shock, and short circuit tests with a 90-100% passing rate without cell leakage, breakage, or fire, as shown in Table 7.

[0179] Table 7: Summary results of NMC90 after testing the safety test

[0180] Test name Passing rate (%)

[0181] Altitude test 100

[0182] Thermal test 90

[0183] Shock test 90

[0184] Short circuit test 90

[0185] Impact test 100

[0186] Moreover, neither sample experienced bursting in the impact test, resulting in a 100% passing rate. Furthermore, the heat curve of cell during impact testing indicated a maximum temperature below 110°C, suggesting the absence of active material decomposition, as depicted in Fig. 25. These results imply that the battery configuration employed in this invention standardizes safety quality and has the potential for further development and scalability in practical applications.

[0187] In summary, NMC80 materials display multiple secondary particle sizes (13.6+3.7 pm in diameter), whereas NMC90 powder exhibits uniform secondary particle sizes with a narrow distribution (9.1+0.4 pm in diameter). Both cells demonstrate electrochemical performance through a practical 18650 cylindrical lithium-ion battery. The NMC90 cell presents superior rate capability, delivering higher discharge capacity across all C-rates, especially at high C-rates (5.0C), where it outperforms the NMC80 cell by over 50 times. Regarding stability, the NMC90 / graphite cell exhibits significantly better retention of 73.6% after 1,000 cycles, with lower kinetic hindrance than the NMC80 / graphite cell (53.9% capacity retention), leading to a 22% increase in accumulated energy density. In addition, the NMC90 cell operates at high voltage with less gas evolution. Finally, the NMC90 sample passed the safety evaluation according to the UN38.3 standard. These results indicate that controlling particle size distribution contributes to exceptional battery performance by improving lithium-ion diffusivity. Consequently, the nickel-rich layered oxide material with uniform particle size holds promises as a cathode in lithium-ion batteries with high energy and long-term durability.

[0188] BEST MODE OF THE INVENTION

[0189] Best mode of the invention is as described in the detailed description of the invention.

Claims

WHAT IS CLAIMED IS:

1. A cathode active material for a lithium battery, comprising lithium nickel manganese cobalt oxide (NMC) powder and a metal coating on the lithium nickel manganese cobalt oxide powder, wherein the lithium nickel manganese cobalt oxide powder comprises a nickel content of 90 wt% or more and has an average secondary particle size ranging from 8 to 10 pm, and the metal coating on the lithium nickel manganese cobalt oxide powder is selected from a group consisting of zirconium, strontium, and a combination thereof.

2. The cathode active material according to claim 1, which has a Formula: LiNiaMnbCocZrdSreCh, where 0.9 < a < 1.0; 0 < b < 0.1; 0 < c < 0.1; 0 < d < 0.01; 0 < e < 0.01; and the sum of a, b, c, d, and e is 1.

3. The cathode active material according to claim 1, wherein the lithium nickel manganese cobalt oxide powder has the average secondary particle size ranging from 8.5 to 9.5 pm and exhibits uniform particle size distribution.

4. The cathode active material according to claim 1, wherein the lithium nickel manganese cobalt oxide powder has an average primary particle size ranging from 0.4 to 0.6 pm.

5. The cathode active material according to claim 1, wherein the metal coating on the lithium nickel manganese cobalt oxide powder is obtained from a compound selected from zirconium oxide, strontium oxide, and a combination thereof.

6. The cathode active material according to claim 1, wherein the metal coating on the lithium nickel manganese cobalt oxide powder has a zirconium content ranging from 0.001-0.01 wt% and a strontium content ranging from 0.001-0.01 wt%.

7. The cathode active material according to claim 6, wherein the metal coating on the lithium nickel manganese cobalt oxide powder has the zirconium content ranging from 0.001-0.006 wt% and the strontium content ranging from 0.001-0.004 wt%.

8. A cathode for a lithium battery comprising the cathode active material according to claim 1.

9. A lithium battery comprising the cathode active material according to claim 1.

Images