Lithium oxide cathode and lithium-ion battery comprising the same

Abstract

A lithium oxide cathode for a lithium-ion battery includes: a current collector; and a cathode material layer disposited onto the current collector and comprising a cathode material, a first metal oxide deposited on the cathode material, and a second metal oxide deposited on the first metal oxide, wherein the cathode material is a lithium oxide based cathode material, the first metal oxide comprises Al2O3, and the second metal oxide comprises TiO2, V2O5, ZrO2, ZnO or a combination thereof.

Description

[Technical Field]

[0001] This invention relates to a lithium oxide cathode and a lithium-ion battery comprising the same. More specifically, this invention relates to a lithium-rich layered oxide (LLO) cathode and a lithium-ion battery comprising the same. [Previous Technology]

[0002] In recent years, the popularity of electric vehicles (EVs) and hybrid electric vehicles (HEVs) has increased significantly, leading to the widespread use of rechargeable lithium-ion batteries (LIBs) in public transportation. With the increasing demand for transportation, researching rechargeable lithium-ion batteries to extend their lifespan and enhance their energy storage capacity has become an important research topic. Fundamentally, the energy storage capacity of a lithium-ion battery depends on the difference in lithium chemical potential and the reversible capacity between the positive and negative electrodes. However, compared to the negative electrode, the positive electrode used in contemporary mass-produced lithium-ion batteries typically has a lower capacity. Over the past few decades, various positive electrode materials have been developed for practical applications, including LiCoO2 and LiMnO2, layered LiNi1-xCoxO2, spinel-structured LiMn2O4 and LiNi0.5Mn1.5O4, and olivine-structured LiFePO4. However, the overall energy storage capacity of these batteries often faces limitations.

[0003] Achieving greater energy storage capacity and the ability to output more power in LIBs is crucial. Therefore, there is an urgent need to provide a new cathode material with higher specific capacity. [Summary of the Invention]

[0004] One embodiment of the present invention is to provide a lithium oxide positive electrode for a lithium-ion battery, comprising: a current collector; and a positive electrode material layer disposed on the current collector and comprising a positive electrode material, a first metal oxide deposited on the positive electrode material, and a second metal oxide deposited on the first metal oxide; wherein the positive electrode material is a lithium oxide positive electrode material, the first metal oxide comprises Al2O3 and the second metal oxide comprises TiO2, V2O5, ZrO2, ZnO or a combination thereof.

[0005] Another aspect of the present invention is to provide a lithium-ion battery, comprising: a lithium oxide positive electrode as described above; a negative electrode disposed opposite to the lithium oxide positive electrode; a separator disposed between the lithium oxide positive electrode and the negative electrode; and an electrolyte disposed between the lithium oxide positive electrode and the negative electrode.

[0006] Details of one or more embodiments of the present invention are set forth in the following description. Other features, objects, and advantages of the present invention will be apparent from the description and the claims.

Implementation Method

[0007] The following details a lithium oxide cathode for lithium-ion batteries, comprising: a current collector; and a cathode material layer disposed on the current collector and comprising a cathode material, a first metal oxide deposited on the cathode material, and a second metal oxide deposited on the first metal oxide; wherein the cathode material is a lithium oxide cathode material, the first metal oxide comprises Al2O3 and the second metal oxide comprises TiO2, V2O5, ZrO2, ZnO or a combination thereof.

[0008] The following also discloses in detail a lithium-ion battery comprising: a lithium oxide positive electrode as described above; a negative electrode disposed opposite to the lithium oxide positive electrode; a separator disposed between the lithium oxide positive electrode and the negative electrode; and an electrolyte disposed between the lithium oxide positive electrode and the negative electrode.

[0009] In one embodiment, the current collector is aluminum foil, but the invention is not limited thereto. The current collector used in the electrodes of the present invention can be any other known current collector used in the art, such as copper foil.

[0010] In one embodiment, the negative electrode is a lithium metal negative electrode. However, the invention is not limited thereto, and any other known negative electrode may be used in the invention.

[0011] In one embodiment, the separator may be a polypropylene separator, a polyethylene separator, or a combination thereof. However, the invention is not limited thereto, and any other known separator may be used in the invention.

[0012] In one embodiment, the first metal oxide may comprise Al2O3, and the second metal oxide may comprise TiO2, V2O5, ZrO2, ZnO, or a combination thereof. In one embodiment, the first metal oxide may comprise Al2O3, and the second metal oxide may comprise TiO2, V2O5, ZrO2, or ZnO. In one embodiment, the first metal oxide may comprise Al2O3, and the second metal oxide may comprise TiO2.

[0013] In one embodiment, the first metal oxide and the second metal oxide can be formed by atomic layer deposition (ALD). In one embodiment, the Al2O3 of the first metal oxide is formed by ALD, and the TiO2 of the second metal oxide is also formed by ALD.

[0014] In one embodiment, the thickness of the first metal oxide may be in the range of 0.5 nm to 5 nm, for example 0.5 nm to 4.5 nm, 0.5 nm to 4 nm, 0.5 nm to 3.5 nm, 0.5 nm to 3 nm, 1 nm to 3 nm, 1 nm to 2.5 nm, 1.5 nm to 3 nm or 1.5 nm to 2.5 nm.

[0015] In one embodiment, the thickness of the second metal oxide may be in the range of 0.5 nm to 5 nm, for example 1 nm to 5 nm, 1 nm to 4.5 nm, 1 nm to 4 nm, 1.5 nm to 4 nm or 1.5 nm to 3.5 nm.

[0016] In one embodiment, the sum of the thicknesses of the first metal oxide and the second metal oxide can be from 1 nm to 10 nm, for example, 1 nm to 9 nm, 1 nm to 8 nm, 1 nm to 7 nm, 2 nm to 7 nm, 2 nm to 6 nm, 3 nm to 6 nm, or 3 nm to 5 nm. In one embodiment, the sum of the thicknesses of the first metal oxide and the second metal oxide can be about 3 nm. In one embodiment, the sum of the thicknesses of the first metal oxide and the second metal oxide can be about 4 nm. In one embodiment, the sum of the thicknesses of the first metal oxide and the second metal oxide can be about 5 nm.

[0017] In one embodiment, the ratio of the thickness of the first metal oxide to the thickness of the second metal oxide is not particularly limited, and may be, for example, 1:5 to 5:1, 1:4 to 4:1, 1:3 to 3:1, 1:2 to 2:1, or 1:1.5 to 1.5:1. In one embodiment, the ratio of the thickness of the first metal oxide to the thickness of the second metal oxide may be approximately 1:1. In one embodiment, the ratio of the thickness of the first metal oxide to the thickness of the second metal oxide may be approximately 1:2.

[0018] In one embodiment, the positive electrode material may have the chemical formula LiaNibCocMndO2, wherein 0.9 ≤ a ≤ 1.1, 0.3 ≤ b ≤ 0.5, 0.01 ≤ c ≤ 0.5 and 0.3 ≤ d ≤ 0.6.

[0019] In one embodiment, the positive electrode material may have the chemical formula LiaNbCcMndO2, wherein 0.9 ≤ a ≤ 1.1, 0.3 ≤ b ≤ 0.5, 0.01 ≤ c ≤ 0.15, and 0.4 ≤ d ≤ 0.6. In one embodiment, the positive electrode material may be Li1.08Ni0.34Co0.08Mn0.5O2.

[0020] In one embodiment, the positive electrode material may have the chemical formula Li1Ni1 / 3Co1 / 3Mn1 / 3O2, wherein 0.9 ≤ a ≤ 1.1, 0.3 ≤ b ≤ 0.5, 0.3 ≤ c ≤ 0.5 and 0.3 ≤ d ≤ 0.5. In one embodiment, the positive electrode material may be Li1Ni1 / 3Co1 / 3Mn1 / 3O2.

[0021] In one embodiment, the cathode material may have the chemical formula LixNiyMnzO4, wherein 0.9 ≤ x ≤ 1.1, 0.3 ≤ y ≤ 0.8, and 1.2 ≤ z ≤ 1.7. In one embodiment, the cathode material may be LiNi0.5Mn1.5O4.

[0022] In one embodiment, the positive electrode material may further comprise a conductive additive. The conductive additive may be any known conductive additive used in the art, such as metal particles, conductive metal oxides, carbon black (e.g., conductive carbon or acetylene black), carbon nanotubes, graphite, carbon nanofibers, other conductive materials, or combinations thereof, but the invention is not limited thereto.

[0023] In one embodiment, the content of the conductive additive may be from 1 wt% to 10 wt% based on the total weight of the positive electrode material, for example, 1 wt% to 9 wt%, 2 wt% to 9 wt%, 2 wt% to 8 wt%, 3 wt% to 8 wt%, 3 wt% to 7 wt%, 4 wt% to 7 wt%, or 4 wt% to 6 wt%. In one embodiment, the content of the conductive additive is approximately 4 wt% based on the total weight of the positive electrode material. However, the present invention is not limited thereto, and the content of the conductive additive may be adjusted as needed.

[0024] In one embodiment, the positive electrode material may further comprise an adhesive. The adhesive may be any adhesive used in the art, such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex (SBR), sodium carboxymethyl cellulose (CMC), other adhesives or combinations thereof, but the invention is not limited thereto.

[0025] In one embodiment, the binder content may be 3 wt% to 10 wt% based on the total weight of the cathode material, for example, 3 wt% to 9 wt%, 3 wt% to 8 wt%, 3 wt% to 7 wt%, 4 wt% to 7 wt%, or 4 wt% to 6 wt%. In one embodiment, the binder content is approximately 5 wt% based on the total weight of the cathode material. However, the invention is not limited thereto, and the binder content may be adjusted as needed.

[0026] When the lithium oxide cathode of the present invention is used in a lithium-ion battery, the lithium-ion battery exhibits increased discharge capacity, enhanced capacity retention, reduced voltage decay, lower surface film interfacial resistance, and improved interfacial charge transfer resistance, thereby contributing to improved stability. Therefore, the lithium oxide cathode of the present invention has good potential for improving the electrochemical performance of lithium-rich layered oxide cathodes in lithium-ion batteries.

[0027] Different embodiments of the present invention are provided in the following description. These embodiments are intended to explain the technical content of the present invention, but are not intended to limit the scope of the present invention. The features described in the embodiments can be applied to other embodiments through appropriate modifications, substitutions, combinations, or separations.

[0028] It should be noted that in this specification, when a component is described as having a certain element, it means that the component may have one or more of the elements, and does not mean that the component has only one of the elements, unless otherwise stated.

[0029] Furthermore, in this specification, ordinal numbers, such as "first" or "second," are used to distinguish multiple elements with the same name and do not indicate an inherent hierarchy, rank, execution order, or manufacturing order among the elements, unless otherwise stated. A "first" element and a "second" element may coexist in the same component, or they may coexist in different components. The presence of an element with a higher ordinal number does not necessarily imply the presence of an element with a lower ordinal number.

[0030] Furthermore, in this specification, terms such as “top,” “bottom,” “left,” “right,” “front,” “back,” or “middle,” and terms such as “above,” “over,” “below,” “below,” or “between” are used to describe the relative positions between multiple elements, and the described relative positions may be interpreted as including their translation, rotation, or reflection.

[0031] Furthermore, in this specification, when an element is described as being arranged "on" another element, it does not necessarily mean that the element is in contact with the other element, unless otherwise stated. Such an interpretation also applies to other situations similar to "on".

[0032] Furthermore, in this specification, unless otherwise stated, a value may be interpreted as covering a range within ±10% of the value, and in particular, a range within ±5% of the value; unless otherwise stated, a range may be interpreted as consisting of multiple subranges defined by the smaller endpoint, the smaller quartile, the median, the larger quartile, and the larger endpoint.

[0033] Example

[0034] AS200 electrode preparation

[0035] Using 1000 mL of an aqueous solution containing transition metal nitrates (0.34 M Ni(NO3)2, 0.5 M M Mn(NO3)2, and 0.08 M Co(NO3)2) as the starting material, the cathode material Li1.08Ni0.34Co0.08Mn0.5O2 was synthesized via spray pyrolysis. The resulting dry powder can be used as a precursor material. To produce Li1.08[Ni0.34Co0.08Mn0.5]O2, the precursor was ball-milled with Li2CO3, maintaining a Li:(Ni+Co+Mn) molar ratio of 1.08:1.00. Subsequently, the mixture was heated at 910°C for 10 hours under an oxygen flow, with the temperature gradually increased at a rate of 5°C / min. This process ultimately produced a stoichiometric cathode material, designated AS200.

[0036] NCM333 Electrode Preparation

[0037] The cathode material NCM333 was synthesized by spray pyrolysis using 1000 mL of an aqueous solution containing transition metal nitrates (0.33 M Ni(NO3)2, 0.33 M Mn(NO3)2, and 0.33 M Co(NO3)2) as the starting material. The resulting dry powder can be used as a precursor material. To produce NCM333, the precursor was ball-milled together with Li2CO3. Subsequently, the mixture was heated at 880°C for 6 hours under an oxygen flow, with the temperature gradually increased at a rate of 5°C / min. This process ultimately produced a stoichiometric spherical cathode material.

[0038] LNMO electrode preparation

[0039] CH3COOLi·2H2O, nickel(II) acetate tetrahydrate Ni(CH3COO)2·4H2O, and manganese(II) acetate tetrahydrate Mn(CH3COO)2·4H2O were mixed in a stoichiometric ratio of 1.05:1:1. Then, they were dissolved separately in distilled water with continuous stirring to obtain solution A. Next, an appropriate amount of adipic acid C6H10O4 was dissolved in 100 ml of distilled water as a chelating agent to obtain solution B. After the two solutions were prepared, they were mixed and then stirred at 120°C until the solvent was completely evaporated. The resulting powder was collected and dried at 100°C for 24 hours to completely remove residual solvent from the precursor powder. The received powder was pre-calcined in air at 420°C for 12 hours to remove organic residues. The resulting powder was then ground in a mortar to obtain a fine powder. The prepared LNMO was then calcined at 900°C for 10 hours in air and allowed to cool naturally to room temperature.

[0040] TiO2 / Al2O3 double-layer ALD coating

[0041] TiO2 / Al2O3 bilayer films were deposited on AS200, NCM 333, or LNMO electrodes using a BENEQ TFS 500 atomic layer deposition (ALD) system. First, AS200, NCM 333, or LNMO electrodes were prepared by mixing conductive carbon (KS6 and Super P) and polyvinylidene fluoride (PVDF) in a weight ratio of 91:2:2:5. Subsequently, N-methyl-2-pyrrolidone (NMP) was introduced to prepare a uniform, black, and viscous slurry. This slurry was uniformly coated onto aluminum foil using a doctor blade and then dried under vacuum at 110°C for 24 hours. Next, the AS200, NCM 333, or LNMO electrodes were placed in an ALD reactor and operated at a reference pressure of approximately 1 mTorr. Here, at a temperature of 110°C, using an ALD cycle with trimethylaluminum (TMA) and H2O as precursors, a 1.5 nm (and / or 2.5 nm) thick Al2O3 film was first deposited onto an AS200 electrode or an NCM333 electrode, and a 1.7 nm thick Al2O3 film was first deposited onto an LNMO electrode. Subsequently, maintaining the deposition temperature at 110°C, using an ALD cycle with titanium tetrachloride (TiCl4) and H2O as precursors, a 1.5 nm (and / or 2.5 nm and / or 3.4 nm) thick TiO2 layer was deposited on top of the Al2O3 layer. Precise control was achieved by setting the precursor dosages of Al2O3 and TiO2 in the ALD process, setting the purge time to 0.3 seconds and 0.4 seconds respectively, and applying a 2-second N2 purge between each pulse. Furthermore, the growth rates of each Al2O3 and TiO2 layer were maintained at 1 Å / cycle and 1.5 Å / cycle, respectively. This refined deposition process resulted in TiO2 / Al2O3 bilayer films with thicknesses of 3 nm and 5 nm on AS200 and NCM333 electrodes, respectively, denoted as TAA-3 and TAA-5, and a TiO2 / Al2O3 bilayer film with a thickness of 5 nm on the LNMO electrode, denoted as TiO2 / Al2O3 2:1.

[0042] Lithium-ion battery assembly and measurement

[0043] The CR2032 coin cell was carefully assembled in an argon-filled glove box (Vigor). All materials used in the assembly process were pre-dried in a vacuum furnace at 110°C. For the half-cell, the following components were used: a positive electrode with a diameter of Ø13 mm, a lithium metal negative electrode with a diameter of Ø15 mm, and a polypropylene separator from Celgard Co., Japan. The separator was immersed in a standard electrolyte solution consisting of 200 μL of 1.0 M LiPF6 solution (in a 1:1 weight ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) (supplied by Formosa Co., Taiwan)). To evaluate the electrochemical performance, the CR2032 coin cell was used, with lithium metal as the counter and reference electrode. Cyclic voltammetry was performed at room temperature using a PARSTAT MC 200 electrochemical workstation at a scan rate of 0.1 mV s⁻¹, with the measurement range set between 2.2 V and 4.6 V. Using the Think Power battery testing system, a constant current was applied at a rate of 0.1C at room temperature, and charge and discharge curves were obtained by cycling Li+ / Li at a constant current between 2.2V and 4.6V. Electrochemical impedance spectroscopy (EIS) was performed on CR2032 coin cells using the same workstation, with an applied AC voltage amplitude of 10mV. The measurement covered a frequency range from 100kHz to 0.1Hz. The relaxation time distribution (DRT) was calculated using DRT tools based on the Gaussian discretization method, with a regularization parameter of 10⁻⁴ and a full width at half maximum (FWHM) of 0.5. Further analysis was performed using the Impedance Spectroscopy Genetic Programming (ISGP) program.

[0044] Microstructure analysis was performed using a high-resolution transmission electron microscope (TEM, JEOL JEM-2100F). To protect the integrity of the TiO2 / Al2O3 coating during sample preparation and subsequent processing, a platinum conductive layer was employed. This conductive layer was created through initial electron beam deposition followed by ion beam-assisted deposition using a SEIKO SMI3050SE dual-beam focused ion beam (FIB) instrument. After applying the protective layer, the TEM sample was carefully prepared using a gallium focused ion beam milling technique.

[0045] Result

[0046] Figure 1 is a cross-sectional view of the lithium-ion battery of the present invention. The lithium-ion battery of the present invention includes: a lithium oxide positive electrode 1, comprising a current collector 11 and a positive electrode material layer 12 disposed on the current collector 11; a negative electrode 2, disposed opposite to the lithium oxide positive electrode 1; a separator 3, disposed between the lithium oxide positive electrode 1 and the negative electrode 2; and an electrolyte, disposed between the lithium oxide positive electrode 1 and the negative electrode 2.

[0047] In the lithium half-cell prepared above, the current collector 11 is aluminum foil, the negative electrode 2 is lithium metal negative electrode, the separator is polypropylene separator, and the electrolyte is an electrolyte solution containing LiPF6.

[0048] Figure 2 is a schematic diagram of the cathode material layer of the lithium oxide cathode of the present invention. The cathode material layer of the lithium oxide cathode of the present invention includes a cathode material 121, a first metal oxide 122 deposited on the cathode material 121, and a second metal oxide 123 deposited on the first metal oxide 122. In addition, the cathode material also includes conductive carbon and PVDF as a binder.

[0049] More specifically, as shown in FIG2, the first metal oxide 122 exists in particulate form and is formed and deposited on the cathode material 121 through ALD. The second metal oxide 123 exists in particulate form and is formed and deposited on the first metal oxide 122 through ALD. Furthermore, the particle diameter of the first metal oxide 122 is larger than the particle diameter of the second metal oxide 123, and the particles of the second metal oxide 123 are deposited not only on the particles of the first metal oxide 122, but also between two adjacent particles of the first metal oxide 122.

[0050] Example 1 – TAA-3 / AS200 Electrode

[0051] As shown in Figure 2, the positive electrode material 121 comprises Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200. The first metal oxide 122 is a 1.5 nm thick Al2O3 film. The second metal oxide 123 is a 1.5 nm thick TiO2 film.

[0052] Example 2 – TAA-5 / AS200 Electrode

[0053] As shown in Figure 2, the positive electrode material 121 comprises Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200. The first metal oxide 122 is a 2.5 nm thick Al2O3 film. The second metal oxide 123 is a 2.5 nm thick TiO2 film.

[0054] Comparative Example 1 – AS200 Electrode

[0055] The electrode of this comparative example is similar to that of Example 1, wherein the positive electrode material 121 contains Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200, but the first metal oxide 122 and the second metal oxide 123 are not formed.

[0056] Comparative Example 2 – 3nm TiO2 / AS200 electrode

[0057] The electrode of this comparative example is similar to that of Example 1, wherein the positive electrode material 121 contains Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200, and the second metal oxide 123 is a 3nm thick TiO2 film, but the first metal oxide 122 is not formed.

[0058] Comparative Example 3 – 5nm TiO2 / AS200 electrode

[0059] The electrode of this comparative example is similar to that of Example 1, wherein the positive electrode material 121 contains Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200, and the second metal oxide 123 is a 5nm thick TiO2 film, but the first metal oxide 122 is not formed.

[0060] Comparative Example 4 – 3nm Al2O3 / AS200 electrode

[0061] The electrode of this comparative example is similar to that of Example 1, wherein the positive electrode material 121 contains Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200, and the first metal oxide 122 is a 3nm thick Al2O3 film, but the second metal oxide 123 is not formed.

[0062] Comparative Example 5 – Al2O3 / AS200 electrode at 5 nm

[0063] The electrode of this comparative example is similar to that of Example 1, wherein the positive electrode material 121 contains Li1.08Ni0.34Co0.08Mn0.5O2, abbreviated as AS200, and the first metal oxide 122 is a 5nm thick Al2O3 film, but the second metal oxide 123 is not formed.

[0064] Figures 3A and 3B show TEM images of the cathode material layers of Examples 1 and 2, respectively. Upon inspection, it can be observed that the surfaces of both samples have well-defined boundaries and no lattice fringes. The preferred structural design involves using island-like Al2O3 as the bottom layer, and then depositing TiO2 on top. This arrangement facilitates the gradual merging of the two layers, resulting in a smooth surface, as shown in Figures 3A and 3B.

[0065] Figure 4A shows the initial charge capacities of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes at 0.1C (216 mAh g⁻¹, 239 mAh g⁻¹, and 216 mAh g⁻¹, respectively). The slight decrease in capacity of the TAA-5 / AS200 electrode can be attributed to the insulating properties of the coating. The initial charge / discharge curves of all three samples show a slope region (3.9 V–4.36 V) related to lithium-ion extraction and Ni²⁺ oxidation to Ni⁺⁴. It is known that when the voltage is maintained above 4.5 V for an extended period, lithium ions will be extracted from AS200, leading to the formation of Li₂MnO₃. This will result in a significant loss of battery capacity and the generation of MnO₂ impurities. Applying a TiO₂ / Al₂O₃ bilayer to AS200 can improve the discharge capacity. As shown in Figure 4B, the TAA-3 / AS200 and TAA-5 / AS200 electrodes exhibit higher specific discharge capacities of 188 mAh g⁻¹ and 182 mAh g⁻¹, respectively, compared to the original sample (176 mAh g⁻¹). Figure 4C shows the cycling performance of these samples after 200 charge-discharge cycles at a current density of 0.1C. Notably, all the TiO₂ / Al₂O₃ bilayer coated AS200 electrodes exhibited better specific discharge capacity and enhanced capacity retention compared to the original sample. Particularly noteworthy are the results for the TAA-3 / AS200 sample, which exhibited excellent capacity retention (approximately 86%) and a specific discharge capacity of 162 mAh g⁻¹, surpassing the performance of the original sample (approximately 72% and 143 mAh g⁻¹, respectively).

[0066] Figure 4D shows that the TAA series electrodes exhibit significantly better C-rate performance than the AS200. At a rate of 0.5C, the performance of all samples is comparable. However, at 1C, the TAA-3 / AS200 and TAA-5 / AS200 electrodes achieve capacities of 149 mAh g⁻¹ and 156 mAh g⁻¹, respectively, significantly exceeding the 39 mAh g⁻¹ measured for AS200 at 1C. This enhanced rate capability is attributed to the Li transport facilitated by the ALD deposition layer. Reversible Li⁺ ion insertion into LLOs typically occurs via a two-dimensional pathway. The ALD layer acts as a Li⁺ ion channel, providing additional insertion sites for Li⁺ ions in the LLO, ultimately increasing battery capacity and supporting higher energy densities.

[0067] Furthermore, the rate performance of the monolayer samples (TiO2 / AS200 and Al2O3 / AS200, Comparative Examples 2 to 5) has been verified, as shown in Figures 5A and 5B. In comparison, the TAA-coated samples exhibit better results, which may be attributed to fewer surface defects (e.g., pores) on the electrode surface. In addition, the cycling performance of the TAA-coated samples after 100 charge-discharge cycles at a current density of 1C was also confirmed, as shown in Figure 6. The capacity retention after cycling for the AS200 electrode, TAA-3 electrode, and TAA-5 electrode were 52.5%, 70.6%, and 90.4%, respectively.

[0068] Figures 7A to 7C show the relationship between voltage and normalized capacity of the studied electrodes after multiple cycles at a rate of 0.1C. The TAA series electrodes exhibit better stability, as can be seen from their resistance to voltage decay observed in the evolution of their discharge curves over 200 cycles. Although all electrodes exhibit significant voltage decay over long cycles, the AS200 electrode experiences increasingly severe decay with continued cycling. Specifically, the midpoint discharge voltage (MPV) of the AS200 electrode decreased by 760 mV, while the MPV of the TAA-3 / AS200 and TAA-5 / AS200 electrodes decreased by only 390 mV and 530 mV, respectively.

[0069] To better understand the observed voltage decay, we analyzed the dQ / dV plots of samples with different cycles, as shown in Figures 7D to 7F. During the initial discharge cycle, all samples exhibited a distinct reduction peak, occurring between 3.7V and 4.4V. This peak corresponds to the reduction of Ni4+ to Ni3+ / Ni2+, Co4+ / Co3+, and On- / O2-. As the charge-discharge cycle progressed to 150 cycles, these reduction peaks only slightly weakened and shifted to lower potentials. Surprisingly, in the AS200 electrode, all reduction peaks almost disappeared after 150 cycles, with a strong peak appearing at 3V. This peak is related to the reduction of Mn4+ to Mn3+ in the layered oxide with a spinel structure. In contrast, in the TAA-3 / AS200 and TAA-5 / AS200 electrodes, the shift in reduction peaks was less pronounced, stopping at approximately 3.4V. This corresponds to the reduction of Mn4+ to Mn3+ in the layered structure. Furthermore, a minor peak at approximately 2.8 V was observed in all samples, which is associated with the reduction of Mn4+ in the layered oxides exhibiting stronger spinel characteristics. These results indicate that the transformation from the layered phase to the spinel phase is strictly suppressed during cycling in the TAA series samples, resulting in reduced voltage decay and capacity loss.

[0070] To gain a deeper understanding of the interfacial characteristics between the electrode and electrolyte, we performed electrochemical impedance spectroscopy (EIS) measurements at MPV (3.8V) in the frequency range of 100 kHz to 0.1 Hz after three cycles of activation at 0.1 C. The results are shown in Figures 8A to 8C. All electrodes exhibited compressed semicircles in the high-frequency region and sloping lines in the low-frequency region, indicating that the electrochemical process is mainly affected by charge transfer and Li+ ion diffusion at the electrode / electrolyte interface. Furthermore, the charge transfer resistance in the high-frequency semicircles of the TAA series electrodes was significantly reduced compared to the AS200 electrode. However, after 100 cycles, although the total impedance of the cells using the TAA series electrodes increased significantly, they were still much smaller than the total impedance of the cells using the AS200 electrode. To further understand the observations, we performed relaxation time distribution (DRT) analysis based on the impedance response. The DRT derived from all impedance data is plotted in Figures 8D to 8F. These graphs reveal three distinct characteristics near the 103 Hz (P1), 10 Hz (P2), and 1 Hz (P3) frequency regions. P1 can be attributed to the surface film resistance resulting from lithium-ion migration across the electrode surface, P2 to the charge transfer resistance at the electrode / electrolyte interface, and P3 to charge transfer and solid-state diffusion at the active material / current collector interface. Comparing the graphs of all samples, it is evident that characteristics P1 and P2 in the AS200 electrode are brighter than those in the TAA series electrodes, indicating higher surface film resistance and interfacial charge transfer resistance in the AS200 electrode. The relatively small impedance variation observed in the TAA series electrodes is attributed to the TiO2 / Al2O3 bilayer coating's ability to mitigate changes at the electrode / electrolyte interface during cycling. The slightly higher resistance of the coating material is related to the smaller contact area between the active material and the electrolyte after the TiO2 / Al2O3 bilayer coating. Therefore, the TAA series electrodes exhibit less structural change, less grain coarsening, and smaller impedance fluctuations during cycling. These characteristics demonstrate that the TiO2 / Al2O3 bilayer coating can effectively mitigate discharge voltage decay.

[0071] The significant decrease in surface film impedance observed in the results indicates that the electrolyte decomposition in the TAA series electrodes is not too severe. This phenomenon is closely related to the protective shielding effect of the TiO2 / Al2O3 bilayer, which prevents direct contact between the AS200 active material and the electrolyte.

[0072] Example 3 – TiO2 / Al2O3 / NCM333 5nm

[0073] As shown in Figure 2, the positive electrode material 121 comprises Li1Ni1 / 3Co1 / 3Mn1 / 3O2, abbreviated as NCM333. The first metal oxide 122 is a 2.5 nm thick Al2O3 film. The second metal oxide 123 is a 2.5 nm thick TiO2 film.

[0074] Comparative Example 6 – NCM333 Electrode

[0075] The electrode of this comparative example is similar to that of Example 3, wherein the positive electrode material 121 contains Li1Ni1 / 3Co1 / 3Mn1 / 3O2, abbreviated as NCM333, but the first metal oxide 122 and the second metal oxide 123 are not formed.

[0076] Figure 9A shows the cycling performance of these samples from Example 3 and Comparative Example 6. Figure 9B shows the rate performance of these samples from Example 3 and Comparative Example 6. The results indicate that the sample from Example 3 has better C performance than the sample from Comparative Example 6. The capacitance retention capabilities of the samples from Example 3 and Comparative Example 6 after cycling are shown in Table 1 below.

[0077] Table 1 Comparative Example 6 NCM333 Example 3 TiO2 / Al2O3 / NCM333 5nm 3C 61.7% 65.7% 5C 40.6% 51.2% 10C 12.8% 23.9%

[0078] Example 4 – TiO2 / Al2O3 2:1 LNMO electrode

[0079] As shown in Figure 2, the positive electrode material 121 comprises LiNi0.5Mn1.5O4, abbreviated as LMNO. The first metal oxide 122 is a 1.7 nm thick Al2O3 film. The second metal oxide 123 is a 3.4 nm thick TiO2 film.

[0080] Comparative Example 7 – LMNO Electrode

[0081] The electrode of this comparative example is similar to that of Example 4, wherein the positive electrode material 121 contains LiNi0.5Mn1.5O4, abbreviated as LMNO, but does not form the first metal oxide 122 and the second metal oxide 123.

[0082] Figure 10 shows the cycling performance of these samples from Example 4 and Comparative Example 7. The results indicate that the sample from Example 4 has better C performance than the sample from Comparative Example 7.

[0083] In summary, the TiO2 / Al2O3 bilayer coating not only maintains the structural integrity of the cathode material but also significantly improves its electrochemical performance. The coated electrode exhibits excellent capacity retention, enhanced rate performance, and improved stability, making it a promising candidate material for high-performance lithium-ion batteries. These findings highlight the effectiveness of ALD coatings in optimizing the surface properties of electrode materials, paving the way for the development of advanced energy storage devices.

[0084] Although the present disclosure has been described in conjunction with its embodiments, it should be understood that many other possible modifications and variations may be made without departing from the spirit and scope of the present disclosure as claimed below. [Simplified Explanation of the Diagram]

[0085] Figure 1 is a cross-sectional view of the lithium-ion battery of the present invention. Figure 2 is a schematic diagram of the positive electrode material layer of the lithium oxide cathode of the present invention. Figure 3A shows a TEM image of the positive electrode material layer of Example 1. Figure 3B shows a TEM image of the positive electrode material layer of Example 2. Figure 4A shows the initial charge / discharge curves of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes. Figure 4B shows the corresponding histograms of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes at a rate of 0.1C for the first charge, discharge, and irreversible capacity loss. Figure 4C shows the cycle performance of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes tested at a rate of 0.1C within a voltage range of 2.2V to 4.6V. Figure 4D shows the rate performance of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes from 0.1C to 10C rates during the period from 2.2V to 4.6V. Figure 5A shows the comparative rate performance of the AS200, 3 nm-TiO2 / AS200, 3 nm-Al2O3 / AS200, and TAA-3 electrodes at different C rates, in the potential range from 2.2V to 4.6V. Figure 5B shows the comparative rate performance of the AS200, 5 nm-TiO2 / AS200, 5 nm-Al2O3 / AS200, and TAA-5 electrodes at different C rates, in the potential range from 2.2V to 4.6V. Figure 6 shows a comparison of the cycling performance of the AS200, TAA-3, and TAA-5 electrodes at 1C, in the potential range from 2.2V to 4.6V. Figures 7A to 7C show the voltage-normalized capacitance curves for the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes, respectively. Figures 7D to 7F show the differential capacity (dQ / dV) plots for the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes, respectively. Figures 8A to 8C show the EIS spectra of the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes at 3.8V, with a frequency range from 100kHz to 0.1Hz, recorded after 0 to 100 cycles. Figures 8D to 8F show the DRT plots for the AS200, TAA-3 / AS200, and TAA-5 / AS200 electrodes, respectively. Figure 9A shows the cycling performance of NCM333 and TiO2 / Al2O3 / NCM333 5 nm electrodes tested at a rate of 0.1C over a voltage range of 3.0V to 4.95V.Figure 9B shows the rate performance of the NCM333 and TiO2 / Al2O3 / NCM333 5 nm electrodes from 0.1C to 10C rates during the period from 2.2V to 4.6V. Figure 10 shows the cycling performance of the LNMO and TiO2 / Al2O3 2:1 LNMO electrodes tested at 0.1C rates over a voltage range from 3.0V to 4.95V. [Biomaterial Storage]

[0087] None.

Claims

1. A lithium oxide positive electrode for a lithium-ion battery, comprising: a current collector; and a positive electrode material layer disposed on the current collector and comprising a positive electrode material, a first metal oxide deposited on the positive electrode material, and a second metal oxide deposited on the first metal oxide; wherein, The cathode material is a lithium monoxide cathode material, wherein the first metal oxide comprises Al2O3 and the second metal oxide comprises TiO2, V2O5, ZrO2, ZnO or a combination thereof.

2. The lithium oxide cathode as described in claim 1, wherein, The second metal oxide contains TiO2.

3. The lithium oxide cathode as described in claim 1, wherein, The thickness of the first metal oxide is 0.5 nm to 5 nm.

4. The lithium oxide cathode as described in claim 1, wherein, The thickness of the second metal oxide is 0.5 nm to 5 nm.

5. The lithium oxide cathode as described in claim 1, wherein, The lithium oxide cathode material is lithium nickel manganese cobalt oxide or lithium nickel manganese oxide.

6. The lithium oxide cathode as described in claim 1, wherein, The cathode material is Li1.08Ni0.34Co0.08Mn0.5O2.

7. The lithium oxide cathode as described in claim 1, wherein, The cathode material is Li1Ni1 / 3Co1 / 3Mn1 / 3O2.

8. The lithium oxide cathode as described in claim 1, wherein, The cathode material is LiNi0.5Mn1.5O4.

9. The lithium oxide cathode as described in claim 1, wherein, The cathode material also contains a conductive additive.

10. The lithium oxide cathode as described in claim 9, wherein, Based on the total weight of the cathode material, the content of the conductive additive is 1 wt% to 10 wt%.

11. A lithium-ion battery, comprising: a lithium monoxide positive electrode, comprising: a current collector; and a positive electrode material layer disposed on the current collector and comprising a positive electrode material, a first metal oxide deposited on the positive electrode material, and a second metal oxide deposited on the first metal oxide, wherein, The positive electrode material is a lithium monoxide positive electrode material, the first metal oxide contains Al2O3 and the second metal oxide contains TiO2, V2O5, ZrO2, ZnO or a combination thereof; a negative electrode is disposed opposite to the lithium oxide positive electrode; a separator is disposed between the lithium oxide positive electrode and the negative electrode; and an electrolyte is disposed between the lithium oxide positive electrode and the negative electrode.

12. The lithium-ion battery as described in claim 11, wherein, The second metal oxide contains TiO2.

13. The lithium-ion battery as described in claim 11, wherein, The thickness of the first metal oxide is 0.5 nm to 5 nm.

14. The lithium-ion battery as described in claim 11, wherein, The thickness of the second metal oxide is 0.5 nm to 5 nm.

15. The lithium-ion battery as described in claim 11, wherein, The lithium oxide cathode material is lithium nickel manganese cobalt oxide or lithium nickel manganese oxide.

16. The lithium-ion battery as described in claim 11, wherein, The cathode material is Li1.08Ni0.34Co0.08Mn0.5O2.

17. The lithium-ion battery as described in claim 11, wherein, The cathode material is Li1Ni1 / 3Co1 / 3Mn1 / 3O2.

18. The lithium-ion battery as described in claim 11, wherein, The cathode material is LiNi0.5Mn1.5O4.

19. The lithium-ion battery as described in claim 11, wherein, The cathode material also contains a conductive additive.

20. The lithium-ion battery as described in claim 19, wherein, Based on the total weight of the cathode material, the content of the conductive additive is 1 wt% to 10 wt%.

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