Patent Description:
In recent years, with the advancement of technology and the rise of environmental awareness, the demand for reusable secondary batteries has increased gradually. Secondary batteries are used in common devices, such as smart phones, laptops, digital cameras, electric cars, etc. However, these devices are required to have certain level of performance to comply with the trend of miniaturization and increasingly complex functional requirements.

Among different types of secondary batteries, lithium ion battery is a popular and potential choice with its high energy density, high working voltage and long cycle life. However, the surface of the cathode material of the lithium ion battery easily reacts with the electrolyte during charging and discharging. The reaction between the cathode material and the electrolyte results in a decrease in battery characteristics such as the working voltage and the cycle life, and the battery performance is adversely affected.

Therefore, there is a need to provide a cathode material for a secondary battery, and more particularly to a particle structure of cathode material and a preparation method thereof for improving a working voltage and a cycle life of a battery formed thereby. <CIT> discloses cathode material and its method for preparation. The cathode material comprises a core comprising a Li(Ni-Co-Mn)O2 with a coating layer on the core. Said coating layer includes sulfur. In general, it is also disclosed, that the coating layer may further include at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), aluminum (Al), silicon (Si), tin (Sn), lead (Pb), manganese (Mn), iron (Fe), chromium (Cr), nickel (Ni), zinc (Zn), zirconium (Zr), thallium (Tl), and nitrogen (N).

An object of the present disclosure is to provide a particle structure of cathode material and a preparation method thereof for improving a working voltage and a cycle life of a battery formed thereby. The particle structure of cathode material includes at least two coating layers, and each of the different coating layers has different element composition. Preferably but not exclusively, the at least two coating layers are a first coating layer as an inner coating layer and a second coating layer as an outer coating layer. Since the first coating layer contains potassium and aluminum, it is conducive to the migration of lithium ions. Moreover, the second coating layer contains sulfur, so that the reaction between the cathode material and the electrolyte during charging and discharging is avoided. Accordingly, the purpose of improving the battery performances, such as the cycle life, the capacity and the stability, is achieved.

Another object of the present disclosure is to provide a particle structure of cathode material and a preparation method thereof for improving a working voltage and a cycle life of a battery formed thereby. Preferably but not exclusively, a metal salt and a lithium ion compound are mixed and added to a precursor, and a mixture is formed. The metal salt includes potassium, aluminum and sulfur. The precursor includes nickel, cobalt and manganese. After that, the mixture is subjected to a heat treatment, and the particle structure of cathode material is formed. The particle structure of cathode material has at least two coating layers. Thicknesses and compositions of the at least two coating layers are obtained through analysis results of an X-ray photoelectron spectroscopy (XPS) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS). With at least two coating layers having different compositions, such as potassium, aluminum and sulfur, respectively, the migration of lithium ions is improved, and the reaction between the cathode material and the electrolyte during charging and discharging is avoided.

Another object of the present disclosure is to provide a particle structure of cathode material and a preparation method thereof for improving a working voltage and a cycle life of a battery formed thereby. Preferably but not exclusively, a potassium alum in a specific ratio range is added into a precursor, and a mixture is formed. The mixture is subjected to two heat treatment steps, and the particle structure of cathode material is formed to have at least two coating layers. The particle structure of cathode material has low cation disorder degree and orderly layered structure. Moreover, the preparation method of the particle structure of cathode material is simple and low costing. It is helpful of enhancing the product competitiveness of the battery formed by the particle structure of cathode material.

In accordance with an aspect of the present disclosure, a particle structure of cathode material is provided. The particle structure of cathode material includes a core, a first coating layer and a second coating layer. The first coating layer is coated on the core, and the second coating layer is coated on the first coating layer. The core includes potassium and aluminum. The first coating layer includes potassium and aluminum, and a potassium content of the first coating layer is higher than a potassium content of the core. The second coating layer includes sulfur. With the potassium and the aluminum contained in the core and the first coating layer, the migration of lithium ions is improved. Moreover, with the sulfur contained in the second coating layer, the reaction between the particle structure of cathode material and the electrolyte is avoided. Accordingly, the cycle life and the stability of the battery formed by the particle structure of cathode material are improved.

According to the claimed invention, the core includes a Li-M-O based material, wherein M comprises nickel, cobalt and manganese.

In an embodiment, the Li-M-O based material is a lithium nickel manganese cobalt oxide.

In an embodiment, the particle structure of cathode material has a particle size ranged from <NUM> to <NUM>.

In an embodiment, the particle structure of cathode material has a potassium content ranged from <NUM> mol% to <NUM> mol% and an aluminum content ranged from <NUM> mol% to <NUM> mol%.

In an embodiment, the first coating layer has a first thickness, and the second coating layer has a second thickness. The first thickness is greater than the second thickness.

In an embodiment, the first thickness is ranged from <NUM> to <NUM>. The second thickness is ranged from <NUM> to <NUM>. The first thickness and the second thickness are obtained through analysis results of an X-ray photoelectron spectroscopy and a time-of-flight secondary ion mass spectrometer.

In accordance with another aspect of the present disclosure, a preparation method of a particle structure of cathode material is provided. The preparation method includes steps of: (a) providing a precursor configured to form a core, wherein the precursor includes at least nickel, cobalt and manganese; (b) providing a metal salt and a lithium ion compound, wherein the metal salt includes at least potassium, aluminum and sulfur; (c) mixing the metal salt, the lithium ion compound and the precursor to form a mixture; and (d) subjecting the mixture to a heat treatment step to form the particle structure of cathode material, wherein the particle structure of cathode material includes the core, a first coating layer and a second coating layer, wherein the core includes potassium and aluminum, wherein the first coating layer is coated on the core, and the second coating layer is coated on the first coating, wherein the first coating layer includes potassium and aluminum, and a potassium content of the first coating layer is higher than a potassium content of the core, wherein the second coating layer includes sulfur.

In an embodiment, the core includes a Li-M-O based material. M is one selected from the group consisting of nickel, cobalt, manganese, magnesium, titanium, aluminum, tin, chromium, vanadium, molybdenum and a combination thereof.

In an embodiment, the precursor is formed by a co-precipitation of a first solution and a second solution. The first solution includes at least nickel, cobalt and manganese. The second solution includes at least oxalic acid.

In an embodiment, the step (b) further includes a step: (b1) dissolving the metal salt and the lithium ion compound in a water to form a third solution.

In an embodiment, the metal salt has a weight percentage relative to the precursor, and the weight percentage is ranged from <NUM> wt% to <NUM> wt%.

In an embodiment, the heat treatment step includes a temperature-holding step. The temperature-holding step has a temperature greater than or equal to <NUM>.

In an embodiment, the heat treatment step further includes a first heat treatment step and a second heat treatment step. A maximum temperature of the second heat treatment step is greater than a maximum temperature of the first heat treatment step.

In an embodiment, the metal salt is a potassium alum.

The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of the disclosure are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.

Refer to <FIG> is a schematic view illustrating a particle structure of cathode material according to an embodiment of the present disclosure. The particle structure of cathode material <NUM> includes a core <NUM>, a first coating layer <NUM> and a second coating layer <NUM>. The first coating layer <NUM> is coated on the core <NUM>, and the second coating layer <NUM> is coated on the first coating layer <NUM>. The core <NUM> includes potassium and aluminum. The first coating layer <NUM> includes potassium and aluminum, and a potassium content of the first coating layer <NUM> is higher than a potassium content of the core <NUM>. The second coating layer <NUM> includes sulfur. Notably, with the potassium and the aluminum contained in the core <NUM> and the first coating layer <NUM>, the migration of lithium ions is improved. On the other hand, with the sulfur contained in the second coating layer <NUM>, the reaction between the particle structure of cathode material <NUM> and the electrolyte during charging and discharging is avoided. Thus, the cycle life and the stability of the battery formed by the particle structure of cathode material <NUM> are improved.

Refer to <FIG> are SEM images of the particle structure of cathode material according to an embodiment of the present disclosure. In the embodiment, the core <NUM> includes a Li-M-O based material. M is one selected from the group consisting of nickel, cobalt, manganese, magnesium, titanium, aluminum, tin, chromium, vanadium, molybdenum and a combination thereof. Preferably but not exclusively, the Li-M-O based material is a lithium nickel manganese cobalt oxide, and the chemical formula of the lithium nickel manganese cobalt oxide is LiNixCoyMnzO<NUM> (x+y+z=<NUM>, <NUM><x<<NUM>, <NUM><y<<NUM>, <NUM><z<<NUM>). Preferably but not exclusively, the Li-M-O based material is a lithium nickel manganese cobalt oxide with higher nickel content. For example, a lithium nickel manganese cobalt oxide with higher nickel content has an <NUM>:<NUM>:<NUM> molar ratio among nickel, cobalt and manganese, and the chemical formula of the lithium nickel manganese cobalt oxide is LiNi<NUM>Co<NUM>Mn<NUM>O<NUM>. Scanning the particle structure of cathode material <NUM> through a scanning electron microscopy (SEM), and the images are produced as shown in <FIG>. From the images, it can be seen that the particle structure of cathode material <NUM> has a particle size ranged from <NUM> to <NUM>. In the embodiment, the particle structure of cathode material <NUM> has a potassium content ranged from <NUM> mol% to <NUM> mol% and an aluminum content ranged from <NUM> mol% to <NUM> mol%.

In the embodiment, the first coating layer <NUM> has a first thickness H1, and the second coating layer <NUM> has a second thickness H2. The first thickness H1 is greater than the second thickness H2. The first thickness H1 is ranged from <NUM> to <NUM>. The second thickness H2 is ranged from <NUM> to <NUM>. Preferably but not exclusively, the first thickness H1 and the second thickness H2 are obtained through a surface analysis of an X-ray photoelectron spectroscopy (XPS) and a depth profiling analysis of a time-of-flight secondary ion mass spectrometer (TOF-SIMS). It is noted that any instrument that can perform surface analysis and depth profiling analysis, such as an Auger electron spectroscopy (AES), is suitable for obtaining the thicknesses, and the present disclosure is not limited thereto.

Refer to <FIG> is a flow chart of a preparation method of the particle structure of cathode material according to an embodiment of the present disclosure. In accordance with the particle structure of cathode material <NUM> of the present disclosure, a preparation method of the particle structure of cathode material <NUM> is provided. Firstly, a precursor for forming a core <NUM> is provided, as shown in step S1. Preferably but not exclusively, the precursor includes at least nickel, cobalt and manganese for preparing a lithium nickel manganese cobalt oxide material. In the embodiment, the precursor is formed by a co-precipitation of a first solution and a second solution. The first solution includes at least nickel, cobalt and manganese. Preferably but not exclusively, the first solution is mixed by a nickel sulfate (NiSO<NUM>) solution, a cobalt sulfate (CoSO<NUM>) solution, and a manganese sulfate (MnSO<NUM>) solution. The second solution includes at least oxalic acid (H<NUM>C<NUM>O<NUM>). Preferably but not exclusively, the second solution is mixed by an oxalic acid solution, a sodium hydroxide solution and ammonia solution.

Secondly, a metal salt and a lithium ion compound are provided, as shown in step S2. In the embodiment, the metal salt includes at least potassium, aluminum and sulfur. Preferably but not exclusively, the metal salt is a potassium alum (KAl(SO<NUM>)<NUM>·<NUM><NUM>O), and the lithium ion compound is a lithium hydroxide monohydrate (LiOH·H<NUM>O).

After that, the metal salt, the lithium ion compound and the precursor are mixed, and a mixture is formed. In the embodiment, a third solution is formed by dissolving the metal salt and the lithium ion compound in a water before being mixed with the precursor, so as to improve the uniformity of the mixture. In the embodiment, the metal salt has a weight percentage relative to the precursor, and the weight percentage is ranged from <NUM> wt% to <NUM> wt%.

Finally, the mixture is subjected to a heat treatment step, such as calcination, and the particle structure of cathode material <NUM> is formed. In the embodiment, the heat treatment step further includes a temperature-holding step and a cooling step. The temperature-holding step has a temperature greater than or equal to <NUM>. Preferably but not exclusively, holding the temperature at <NUM> facilitates the formation of an orderly layered structure of the particle structure of cathode material <NUM>. The cooling step facilitates the reduction of the oxygen vacancies in the particle structure of cathode material <NUM>. Thus, the battery performance is improved. In the embodiment, the heat treatment step further includes a first heat treatment step and a second heat treatment step. A maximum temperature of the second heat treatment step is greater than a maximum temperature of the first heat treatment step. Preferably but not exclusively, the maximum temperature of the first heat treatment step is <NUM>, and the maximum temperature of the second heat treatment step is <NUM>. With two-step high-temperature calcination, cation disorder degree of the particle structure of cathode material <NUM> is further reduced, and a better orderly layered structure is formed. Thus, the battery performance is further improved.

The following examples illustrate the preparation method and efficacy of the present disclosure.

A first solution and a second solution are mixed for co-precipitation, and a precursor is formed. The first solution is a solution including metal ions, which is mixed by a <NUM> nickel sulfate hexahydrate (NiSO<NUM>·<NUM><NUM>O) solution, a <NUM> cobalt sulfate heptahydrate (CoSO<NUM>·<NUM><NUM>O) solution and a <NUM> hydrated manganese sulfate (MnSO<NUM>·H<NUM>O) solution. The second solution is a solution including oxalic acid, which is mixed by a <NUM> oxalic acid (H<NUM>C<NUM>O<NUM>) solution, a <NUM> sodium hydroxide (NaOH) solution and a <NUM> ammonia (NH<NUM>OH) solution. Preferably but not exclusively, the precursor is Ni<NUM>Co<NUM>Mn<NUM>C<NUM>O<NUM>·<NUM><NUM>O.

A metal salt and a lithium ion compound are dissolved in a water, and a third solution is formed. The metal salt includes at least potassium, aluminum and sulfur, Preferably but not exclusively, the metal salt is a potassium alum (KAl(SO<NUM>)<NUM>·<NUM><NUM>O). The lithium ion compound is a lithium hydroxide monohydrate (LiOH·H<NUM>O). The weight percentage of the potassium alum relative to the precursor is <NUM> wt%.

Refer to <FIG>. <FIG> is a time-temperature curve of a first heat treatment step according to an embodiment of the present disclosure. <FIG> is a time-temperature curve of a second heat treatment step according to an embodiment of the present disclosure. The third solution and the precursor are mixed, and a mixture is formed. The mixture is ground and subjected to a first calcination. Time-temperature curve of the first calcination is shown in <FIG>. Firstly, the mixture is heated from room temperature (<NUM>), and a heating rate is maintained at <NUM>/min for <NUM> hour and <NUM> minutes to reach <NUM> to remove residual moisture on the surface of the mixture. Secondly, the heating rate is maintained at <NUM>/min for <NUM> hours, and the mixture is heated to <NUM> to remove the water of crystallization in the hydrate. Thirdly, the heating rate is maintained at <NUM>/min for <NUM> hours, and the mixture is heated to <NUM> to pyrolyze the oxalate and oxidize the mixture. Fourthly, the heating rate is maintained at <NUM>/min for <NUM> hours and <NUM> minutes, and the mixture is heated to <NUM> to melt the lithium hydroxide. Fifthly, the heating rate is maintained at <NUM>/min for <NUM> hour and <NUM> minutes, and the mixture is heated to <NUM>°Cto allow lithium ions to be doped into the crystal lattice. Finally, the mixture is maintained at <NUM> for <NUM> hours to arrange the crystal lattice into a layered structure. After being subjected to the first calcination, the mixture is taken out, ground, sieved and subjected to a second calcination. Time-temperature curve of the second calcination is shown in <FIG>. Firstly, the mixture is heated from room temperature (<NUM>), and a heating rate is maintained at <NUM>/min for <NUM> hours and <NUM> minutes to reach <NUM>. Secondly, the mixture is maintained at <NUM> for <NUM> hours to arrange the crystal lattice into a better layered structure. Finally, the heating rate is maintained at -<NUM>/min for <NUM> hours to reach <NUM> to reduce the oxygen vacancies in the crystal lattice. The mixture that has been subjected to the second calcination is taken out, ground and sieved, and a particle structure of cathode material <NUM> with multiple coating layers of different elements is formed. With two-step high-temperature calcination, cation disorder degree of the particle structure of cathode material <NUM> is reduced, and the orderly layered structure is formed.

Preferably but not exclusively, a preparation method of the example <NUM> is similar to that of the example <NUM>. However, in the preparation method of the example <NUM>, the weight percentage of the potassium alum relative to the precursor is <NUM> wt%.

Preferably but not exclusively, potassium alum is not added in a preparation method of the comparative example.

Refer to <FIG> are XPS spectra of the example <NUM> and the example <NUM> of the present disclosure. <FIG> are obtained by performing surface analysis on the example <NUM> and the example <NUM> with XPS. As shown in <FIG>, <FIG> and <FIG>, there are obvious peaks in the binding energy range of potassium, aluminum and sulfur, respectively. It can be seen that potassium, aluminum and sulfur, which are the constituent elements of the potassium alum (KAl(SO<NUM>)<NUM>· <NUM><NUM>O), exist in the particle structure of cathode material <NUM>.

Refer to <FIG> and <FIG>. <FIG> is a TOF-SIMS depth profile of potassium in the example <NUM> and the example <NUM> of the present disclosure. <FIG> is a TOF-SIMS depth profile of aluminum in the example <NUM> and the example <NUM> of the present disclosure. <FIG> and <FIG> are obtained by performing depth profiling analyses on the example <NUM> and the example <NUM> with TOF-SIMS. As shown in <FIG> and <FIG>, there are signals of potassium and aluminum within a sputter depth of <NUM>, respectively. However, there is no obvious signal of sulfur. Combined with the XPS analysis results above, it can be seen that sulfur is present in the surface of the particle structure of cathode material <NUM> at a depth of about <NUM> to <NUM>, and potassium and aluminum are doped into the particle structure of cathode material <NUM>. As shown in <FIG>, the doping concentration of potassium in the particle structure of cathode material <NUM> near the surface is higher than that in the interior, and the part with the higher doping concentration of potassium has a thickness between <NUM> and <NUM>. As shown in <FIG>, the doping concentration of aluminum is approximately the same at different depths of the particle structure of cathode material <NUM>.

Refer to <FIG> and <FIG>. <FIG> and <FIG> are charge-discharge characteristic diagrams obtained by performing a test on the comparative example, the example <NUM>, the example <NUM> and the example <NUM> at charge and discharge rates (C-rates) of <NUM>. 5C, 1C, 2C, 5C and <NUM>. 1C in sequence for <NUM> cycles, respectively. The test is performed with a button battery formed by the particle structure of cathode material <NUM>. The electrode of the button battery is formed by mixing the particle structure of cathode material <NUM>, a conductive carbon black and a polyvinylidene fluoride (PVDF) in a ratio of <NUM>:<NUM>:<NUM>. Preferably but not exclusively, the electrolyte includes <NUM> lithium hexafluorophosphate (LiPF<NUM>) solution, ethylene carbonate (EC), dimethyl carbonate (DMC), and <NUM> wt% fluoroethylene carbonate (FEC). The test temperature is room temperature (<NUM>), and the test voltage range is <NUM>. 8V to <NUM>. 3V As shown in the diagrams, the capacity and the capacity retention of the example <NUM>, the example <NUM> and the example <NUM> are obviously higher than those of the comparative example without addition potassium alum. The example <NUM> with <NUM> wt% potassium alum has the best performance.

Refer to <FIG> and <FIG>. <FIG> and <FIG> are charge-discharge characteristic diagrams obtained by performing a test on the comparative example, the example <NUM>, the example <NUM> and the example <NUM> at a C-rate of <NUM>. 3C, a voltage range of <NUM>. 8V to <NUM>. 3V and a room temperature (<NUM>). The following table <NUM> shows the testing results. The test is performed with a button battery made of the particle structure of cathode material <NUM>. The composition of the button battery is the same as above, and is not redundantly described herein. As shown in <FIG>, the capacities of the example <NUM>, the example <NUM> and the example <NUM> are higher than that of the comparative example at a high cycle number. Especially the example <NUM> has the best performance. As shown in <FIG>, capacity retentions of the example <NUM>, the example <NUM> and the example <NUM> are higher than the comparative example at a high cycle number. Especially the example <NUM> has the best performance. As shown in table <NUM> below, the capacity of the comparative example after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. In contrast, the capacity of the example <NUM> after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. It can be concluded from the above results that the particle structure of cathode material <NUM> of the present disclosure facilitates the migration of lithium ions with an inner coating layer including potassium and aluminum, and avoid the reaction between the cathode material and the electrolyte with an outer coating layer including sulfur. Accordingly, the purpose of improving cycle life, capacity and stability of battery is achieved.

<FIG> and <FIG> are charge-discharge characteristic diagrams obtained by performing a test on the comparative example, the example <NUM>, the example <NUM> and the example <NUM> at a C-rate of <NUM>. 5C, a voltage range of <NUM>. 8V to <NUM>. 3V and a temperature of <NUM>. The following table <NUM> shows the testing results. The test is performed with a button battery made of the particle structure of cathode material <NUM>. The composition of the button battery is the same as above, and is not redundantly described herein. As shown in <FIG>, the capacities of the example <NUM>, the example <NUM> and the example <NUM> are similar, but all of them are obviously higher than the capacity of the comparative example at a low cycle number. Especially the example <NUM> has the best performance at a higher cycle number. It is noted that the capacities of the example <NUM>, the example <NUM> and the example <NUM> are higher than that of the comparative example at different cycle numbers. As shown in <FIG>, capacity retentions of the example <NUM>, the example <NUM> and the example <NUM> are higher than the comparative example at a high cycle number. Especially the example <NUM> has the best performance. As shown in table <NUM> below, the capacity of the comparative example after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. In contrast, the capacity of the example <NUM> after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. It can be concluded from the above results that the particle structure of cathode material <NUM> of the present disclosure facilitates the migration of lithium ions with an inner coating layer including potassium and aluminum, and avoid the reaction between the cathode material and the electrolyte with an outer coating layer including sulfur. Accordingly, the purpose of improving cycle life, capacity and stability of battery is achieved.

<FIG> and <FIG> are charge-discharge characteristic diagrams obtained by performing a test on the comparative example, the example <NUM>, the example <NUM> and the example <NUM> at a C-rate of <NUM>. 3C, a voltage range of <NUM>. 8V to <NUM>. 5V and a room temperature (<NUM>). The following table <NUM> shows the testing results. The test is performed with a button battery made of the particle structure of cathode material <NUM>. The composition of the button battery is the same as above, and is not redundantly described herein. As shown in <FIG>, the capacities of the example <NUM>, the example <NUM> and the example <NUM> are higher than that of the comparative example at a high cycle number. Especially the example <NUM> has the best performance. As shown in <FIG>, capacity retentions of the example <NUM>, the example <NUM> and the example <NUM> are obviously higher than the comparative example at a high cycle number. Especially the example <NUM> has the best performance.

As shown in table <NUM> below, the capacity of the comparative example after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. In contrast, the capacity of the example <NUM> after <NUM> cycles is <NUM> mAh/g, and the capacity retention is <NUM>%. It can be concluded from the above results that the particle structure of cathode material <NUM> of the present disclosure facilitates the migration of lithium ions with an inner coating layer including potassium and aluminum, and avoid the reaction between the cathode material and the electrolyte with an outer coating layer including sulfur. Accordingly, the purpose of improving cycle life, capacity and stability of battery is achieved.

Claim 1:
A preparation method of a particle structure of cathode material (<NUM>), characterized by comprising steps of:
(a) providing a precursor configured to form a core (<NUM>), wherein the precursor comprises at least nickel, cobalt and manganese;
(b) providing a metal salt and a lithium ion compound, wherein the metal salt comprises at least potassium, aluminum and sulfur;
(c) mixing the metal salt, the lithium ion compound and the precursor to form a mixture; and
(d) subjecting the mixture to a heat treatment step to form the particle structure of cathode material (<NUM>), wherein the particle structure of cathode material (<NUM>) comprises the core (<NUM>), a first coating layer (<NUM>) and a second coating layer (<NUM>), wherein the core (<NUM>) comprises potassium, aluminum and a Li-M-O based material, wherein M comprises nickel, cobalt, and manganese, wherein the first coating layer (<NUM>) is coated on the core (<NUM>), and the second coating layer (<NUM>) is coated on the first coating layer (<NUM>), wherein the first coating layer (<NUM>) comprises potassium and aluminum, and a potassium content of the first coating layer (<NUM>) is higher than a potassium content of the core (<NUM>), wherein the second coating layer (<NUM>) comprises sulfur.