BATTERY ELECTROLE

Abstract

In one example, a battery comprises a positive electrode and a negative electrode, where the negative electrode contains active material flakes with hydroxylated edges surrounding non-hydroxylated planes. Hydroxylated metal oxide nanoparticles are chemisorbed onto the hydroxylated edges, selectively coating these areas. The metal oxide nanoparticles can be tungsten, niobium, or aluminum.

Description

AREA OF TECHNOLOGY

[0001] This disclosure concerns electrodes for lithium-ion batteries. GENERAL STATE OF THE ART

[0002] Fast charging capability is a key factor in practical lithium-ion battery applications, driving ongoing research. Coating anodes can increase the charging speed of lithium-ion batteries. However, current coating methods such as mixing or impregnation lack distribution control, potentially resulting in random coating across graphite surfaces or only on outer particle areas. SUMMARY

[0003] A battery comprises a positive electrode and a negative electrode, the active material flakes defining hydroxylated edges surrounding non-hydroxylated planes, and hydroxylated metal oxide nanoparticles chemisorbed onto the hydroxylated edges, selectively coating them. The active material flakes can be graphite-based. The metal oxide nanoparticles can be selected from a group including oxides of tungsten, niobium, and aluminum. The metal oxide nanoparticles can be covalently bonded to the hydroxylated edges of the negative electrode. The metal oxide nanoparticles can have an average particle size between 5 nm and 100 nm. The metal oxide nanoparticles can form a uniform coating layer on the hydroxylated edges of the active material flakes. The ring coating can have a thickness between 20 nm and 200 nm.

[0004] An electrode assembly comprises a current collector and a graphite-based active material layer. Active material flakes define hydroxylated edges surrounding non-hydroxylated planes, and metal oxide nanoparticles are chemically bonded to the hydroxylated edges of the active material flakes, forming a selective coating around the hydroxylated edges. The metal oxide nanoparticles can be amorphous metal oxides. The metal oxide nanoparticles can be selected from a group that includes oxides of tungsten, niobium, and aluminum. The non-hydroxylated planes of the graphite-based active material layer can be essentially free of metal oxide nanoparticles. The metal oxide nanoparticles can be covalently bonded to the hydroxylated edges of the graphite-based active material layer. The metal oxide nanoparticles can have an average particle size between 5 nm and 100 nm.The metal oxide nanoparticles can form a continuous layer on the end faces of the graphite-based active material layer.

[0005] A method for forming an electrode material involves applying a hydroxide to a graphite-based active material to form a hydroxide-treated graphite-based active material with hydroxyl groups at edge sites; dispersing the hydroxide-treated graphite-based active material in a nonpolar solvent with a metal chloride precursor to form a graphite-based active material solution; adding a metal chloride precursor solution to the graphite-based active material solution; and calcining the resulting material taken from the graphite-based active material solution to deposit chlorine and form amorphous metal oxide nanoparticles selectively anchored at the edges of the graphite-based active material. The method may further include drying the hydroxide-treated graphite-based active material under vacuum to remove water prior to dispersion in the nonpolar solvent.The nonpolar solvent can be a hydrocarbon solvent. The metal chloride precursor can be selected from a group including tungsten hexachloride, niobium pentachloride, and aluminum trichloride. Calcination can be carried out at 150 °C. The process can further involve removing the resulting material using vacuum filtration prior to calcination. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a conventional electrode coating; Fig. Figures 2-3 are images of selective coatings on electrode edges; Fig. Figure 4 is a schematic representation of the selective coating on electrode edges; and Fig. Figure 5 is a flowchart of a process for forming a ring-coated electrode. DETAILED DESCRIPTION

[0006] According to the present disclosure, embodiments of electrode structures, manufacturing processes, and battery systems are described herein. These embodiments illustrate innovative techniques for improving the performance of lithium-ion batteries by modifying graphite-based active material flakes with hydroxylated edges and integrating metal oxide nanoparticles, such as those selected from oxides of tungsten, niobium, or aluminum, which chemisorb to the hydroxylated edges.

[0007] The figures and descriptions provided are exemplary and may not represent every possible variation or configuration. Certain elements may be enlarged or reduced to highlight specific features of the electrode assemblies and their formation processes. Accordingly, the disclosed structural and functional details are not intended to limit the scope of the invention, but rather to provide guidance for those skilled in the art to implement various embodiments of the claimed subject matter.

[0008] Unless expressly stated otherwise, all disclosed numerical values, measurements, percentages, and similar quantitative parameters are to be interpreted as preceded by "approximately." This includes any figures relating to porosity, particle size, coating thickness, and calcination temperatures. The use of "approximately" accounts for variations due to measurement techniques, manufacturing conditions, material properties, and inherent performance fluctuations of the electrode structures and battery systems. For example, a range of "5 to 100 nm" for nanoparticle size should be interpreted as "approximately 5 to approximately 100 nm," which includes minor variations that do not materially affect the performance or functionality of the electrode assembly or battery system as a whole.

[0009] Anode coating processes, such as mixing and impregnation, have limitations, as previously mentioned. Mixing, for example, might involve combining graphite particles with coating materials, often in the form of polymer binders or conductive additives. This mixture is then applied to the graphite surface, which is subsequently calendered to achieve a dense, cohesive anode layer. While mixing can be straightforward and allows for relatively simple processing, it tends to result in an uneven distribution of the coating material. This occurs because the particles are dispersed rather randomly, with minimal control over where the coating adheres, leading to inconsistencies, particularly at the micro level. Consequently, some graphite particles may remain completely uncoated, while others may have thick, irregular layers.

[0010] Impregnation takes a different approach, introducing coating solutions into an existing anode structure, often by capillary action or immersion, allowing the coating material to penetrate the porous electrode. This is typically achieved using a liquid solution containing conductive or protective materials, such as carbon-based additives or metal particles, introduced under vacuum or by slow infiltration. However, coating materials can be concentrated on the outer surfaces of the graphite particles or near pore openings.

[0011] A coating strategy is presented that utilizes surface reactions to achieve selective coating at graphite edges. This method exploits the presence of surface hydroxyl groups at graphite edges, which are not present at the base plane. These hydroxyl groups can react with moisture-sensitive metal precursors, enabling the selective anchoring of metal compounds to graphite edges. To enhance this process, the surface hydroxyl density can be increased by treating graphite with a hydroxide base, such as potassium hydroxide. This treatment leads to the formation of numerous hydroxyl groups at the edges of graphite particles. The treated graphite is then dispersed in a nonpolar solvent, which can be a liquid hydrocarbon.This step maintains an anhydrous system, restricting hydroxyl groups to graphite edges, and enables effective dispersion of graphite due to the nonpolar nature of its basal plane.

[0012] The choice of metal precursors includes moisture-sensitive compounds such as tungsten hexachloride, niobium pentachloride, or aluminum trichloride. These metals, in their oxide forms, can enhance the fast-charging capabilities of anodes. Due to their covalent bonding, these metal chlorides can be dissolved in the same nonpolar solvent as graphite. The coating process involves the gradual addition of the solution containing the metal precursor to the graphite solution. In this controlled environment, the moisture-sensitive precursors readily react with the hydroxyl groups on graphite edges, forming a homogeneous metal oxychloride coating, particularly at these points. A final step involves a mild calcination process in air, which oxidizes the metal chloride, resulting in an amorphous metal oxide coating layer on the graphite edges.

[0013] This approach offers several advantages over conventional coating methods. Unlike impregnation or mixing processes, which result in a random distribution of coating materials on graphite surfaces, this reaction-based approach ensures that coating occurs only at graphite edges where hydroxyl groups are present. This selectivity maximizes the synergy between graphite and fast-charging materials. By avoiding coating at the base plane, this method prevents the decrease in packing density that typically occurs with conventional coating methods. This preservation of base plane properties helps maintain the energy density of the anode. The solution-based nature of this reaction allows precursor molecules to access internal graphite edges, ensuring a more thorough and uniform coating across the graphite particles.

[0014] Fig. Figure 1 is a schematic representation of a conventional electrode coating strategy. The active material graphite flakes are layered on top of each other, with the coating material applied irregularly. In this conventional approach, the application of the coating material leads to an uneven distribution across the graphite flakes.

[0015] Fig. Figures 2-3 show transmission electron microscopy images of graphite particles selectively coated with tungsten trioxide at their edges. Fig. Figure 2 shows a wider view at a scale of 100 nm. In this image, the layered structure of graphite particles is visible. The edges of these graphite layers appear somewhat darker and more pronounced, likely indicating the presence of the tungsten trioxide coating. The coating is selectively applied to the edges and corners of the graphite layers, in accordance with the selective edge coating strategy. Fig. Figure 3 is a higher magnification view at a scale of 20 nm, allowing a closer examination of the edge coating. In this image, the selective nature of the coating becomes clearer. The edges of the graphite plates are clearly visible and exhibit a significantly darker contrast compared to the flat surfaces. This darker area along the edges represents the tungsten trioxide coating.

[0016] Fig. Figure 4 is a schematic representation of an electrode assembly 10 with selective edge coating. Active material flakes 12, which may be graphite-based, are arranged horizontally. Each active material flake 12 has hydroxylated edges 14 forming a continuous perimeter around each active material flake 12 and non-hydroxylated planes 16. Hydroxylated metal oxide nanoparticles 18 are chemisorbed onto these hydroxylated edges 14, forming a uniform coating layer 20. This coating layer 20 creates a selectively coated ring-like structure around each active material flake 12, demonstrating a well-controlled deposition process that specifically targets the edge regions. The non-hydroxylated planes 16 remain uncoated. Within the coating layer 20, the hydroxylated metal oxide nanoparticles 18 are uniformly distributed along all hydroxylated edges 14 of the active material flakes 12.The hydroxylated metal oxide nanoparticles 18 bind covalently to the hydroxylated edges 14 due to the presence of reactive hydroxyl groups at these sites. The thickness of the coating layer 20 can be uniform around all edges and is typically in the range between 20 nanometers (nm) and 200 nm. The metal oxide nanoparticles 18 themselves have an average particle size between 5 nm and 100 nm.

[0017] Fig.Figure 5 is a flowchart of a process 22 for forming a selectively coated electrode. In a pretreatment step 24, hydroxide, such as potassium hydroxide, is used to increase the density of hydroxyl groups at graphite edges. The graphite is then dried under vacuum to remove water. In the dispersion step 26, graphite is dispersed in a nonpolar solvent such as heptane or toluene. Separately, a moisture-sensitive metal chloride precursor, such as tungsten hexachloride, niobium pentachloride, or aluminum trichloride, is dispersed in the same type of solvent. The addition step 28 involves the gradual addition of the precursor solution to the graphite solution with vigorous stirring, followed by vacuum filtration to remove the sample. Finally, in the calcination step 30, the sample is gently heated to 150 °Celsius to remove chlorine and form amorphous metal oxide at the graphite edges.This process 22 leads to a selective coating with metal oxide nanoparticles on the edges of graphite particles, thereby creating a ring-coated electrode structure.

[0018] While specific embodiments of the electrode structures, methods for forming such structures, and the resulting battery systems have been described in detail, it is not intended that these examples exhaustively cover all possible configurations. The terminology used in this description is intended to describe, not limit, the scope of the invention. Modifications and variations may be made without departing from the basic concepts of the invention described herein. Moreover, the features and elements of the various disclosed embodiments may be combined in unique ways to create additional embodiments within the scope of the claimed subject matter, even if these combinations are not expressly described in this description.

[0019] According to the present invention, a battery is provided comprising: a positive electrode; and a negative electrode comprising active material flakes defining hydroxylated edges surrounding non-hydroxylated planes, and hydroxylated metal oxide nanoparticles chemisorbed onto the hydroxylated edges and selectively coating the hydroxylated edges.

[0020] According to one embodiment, the active material flakes are graphite-based.

[0021] According to one embodiment, the metal oxide nanoparticles are selected from a group comprising oxides of tungsten, niobium and aluminum.

[0022] According to one embodiment, the metal oxide nanoparticles are covalently bonded to the hydroxylated edges of the negative electrode.

[0023] According to one embodiment, the metal oxide nanoparticles have a mean particle size between 5 nm and 100 nm.

[0024] According to one embodiment, the metal oxide nanoparticles form a uniform coating layer on the hydroxylated edges of the active material flakes.

[0025] According to one embodiment, the coating has a thickness between 20 nm and 200 nm.

[0026] According to the present invention, an electrode assembly is provided comprising: a current collector; and a graphite-based active material layer, wherein active material flakes define non-hydroxylated planes surrounding hydroxylated edges, and metal oxide nanoparticles are chemically bonded to the hydroxylated edges of the active material flakes and selectively coat the hydroxylated edges.

[0027] According to one embodiment, the metal oxide nanoparticles are amorphous metal oxides.

[0028] According to one embodiment, the metal oxide nanoparticles are selected from a group comprising oxides of tungsten, niobium and aluminum.

[0029] According to one embodiment, non-hydroxylated layers of the graphite-based active material layer are free of metal oxide nanoparticles.

[0030] According to one embodiment, the metal oxide nanoparticles are covalently bonded to the hydroxylated edges of the graphite-based active material layer.

[0031] According to one embodiment, the metal oxide nanoparticles have a mean particle size between 5 nm and 100 nm.

[0032] According to one embodiment, the metal oxide nanoparticles form a continuous layer at the hydroxylated edges of the graphite-based active material layer.

[0033] According to the present invention, a method for forming an electrode material comprises: applying a hydroxide to a graphite-based active material to form a hydroxide-treated graphite-based active material with hydroxyl groups at edge sites; dispersing the hydroxide-treated graphite-based active material in a nonpolar solvent with a metal chloride precursor to form a graphite-based active material solution; adding a metal chloride precursor solution to the graphite-based active material solution; and calcining the resulting material taken from the graphite-based active material solution to deposit chlorine and form amorphous metal oxide nanoparticles selectively anchored at edge sites of the graphite-based active material.

[0034] In one aspect of the invention, the process involves drying the hydroxide-treated graphite-based active material in a vacuum to remove water prior to dispersion in the nonpolar solvent.

[0035] In one aspect of the invention, the nonpolar solvent is a hydrocarbon solvent.

[0036] In one aspect of the invention, the metal chloride precursor is selected from a group comprising tungsten hexachloride, niobium pentachloride and aluminium trichloride.

[0037] In one aspect of the invention, calcination is carried out at 150 °C.

[0038] In one aspect of the invention, the method involves extracting the resulting material using vacuum filtration prior to calcination.

Claims

[1] Battery, comprising: a positive electrode; and a negative electrode, comprising active material flakes that define hydroxylated edges surrounding non-hydroxylated planes, and hydroxylated metal oxide nanoparticles that are chemisorbed onto the hydroxylated edges and selectively coat the hydroxylated edges. [2] Battery according to claim 1, wherein the active material flakes are graphite-based. [3] Battery according to claim 1, wherein the metal oxide nanoparticles are selected from a group comprising oxides of tungsten, niobium and aluminium. [4] Battery according to claim 1, wherein the metal oxide nanoparticles are covalently bonded to the hydroxylated edges of the negative electrode. [5] Battery according to claim 1, wherein the metal oxide nanoparticles have an average particle size between 5 nm and 100 nm. [6] Battery according to claim 1, wherein the metal oxide nanoparticles form a uniform coating layer on the hydroxylated edges of the active material flakes. [7] Battery according to claim 6, wherein the coating has a thickness between 20 nm and 200 nm. [8] Electrode assembly comprising: a current collector; and a graphite-based active material layer, wherein active material flakes define non-hydroxylated planes surrounding hydroxylated edges and metal oxide nanoparticles are chemically bonded to the hydroxylated edges of the active material flakes and selectively coat the hydroxylated edges. [9] Electrode assembly according to claim 8, wherein the metal oxide nanoparticles are amorphous metal oxides. [10] Electrode assembly according to claim 8, wherein the metal oxide nanoparticles are selected from a group comprising oxides of tungsten, niobium and aluminium. [11] Electrode assembly according to claim 8, wherein non-hydroxylated planes of the graphite-based active material layer are free of metal oxide nanoparticles. [12] Electrode assembly according to claim 8, wherein the metal oxide nanoparticles are covalently bonded to the hydroxylated edges of the graphite-based active material layer. [13] Electrode assembly according to claim 8, wherein the metal oxide nanoparticles have a mean particle size between 5 nm and 100 nm. [14] Electrode assembly according to claim 8, wherein the metal oxide nanoparticles form a continuous layer at the hydroxylated edges of the graphite-based active material layer. [15] Method for forming an electrode material, comprising: Applying a hydroxide to a graphite-based active material to form a hydroxide-treated graphite-based active material with hydroxyl groups at edge locations; Dispersing the hydroxide-treated graphite-based active material in a non-polar solvent with a metal chloride precursor to form a graphite-based active material solution; Adding a metal chloride precursor solution to the graphite-based active material solution; and Calcining of the resulting material extracted from the graphite-based active material solution to deposit chlorine and form amorphous metal oxide nanoparticles selectively anchored at edge sites of the graphite-based active material.

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