BATTERY ELECTROLE

Abstract

A battery is presented that includes a positive electrode assembly and a negative electrode assembly, each with a porous matrix of graphite-based active material and lithiophilic nanoparticles occupying pores defined by the porous matrix. The negative electrode assembly can be formed by loading nickel nanoparticles into graphite, hydrogenating the negative electrode assembly to create porosity within it, and electroplating the negative electrode assembly with silver to replace the nickel nanoparticles.

Description

AREA OF TECHNOLOGY

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

[0002] In lithium-ion batteries, the low equilibrium potential of a graphite anode results in limited overvoltage tolerance. This can make the graphite anode susceptible to the formation of metallic lithium if the potential drops below a threshold during charging, potentially causing lithium plating under high-current charging conditions and at higher states of charge. Several approaches have been proposed to address the challenges of preventing lithium plating and improving reaction kinetics; however, scalable processes applicable to the production of graphite electrodes for fast-charging lithium-ion batteries remain lacking. SUMMARY

[0003] A battery comprises a positive electrode assembly and a negative electrode assembly, each with a porous matrix of graphite-based active material and lithiophilic nanoparticles occupying pores defined by the porous matrix. The lithiophilic nanoparticles may be silver nanoparticles. The lithiophilic nanoparticles may be configured to form a solid solution with lithium within the negative electrode assembly. The porous graphite-based active material matrix may have an increased edge surface area compared to non-porous graphite-based active material. The lithiophilic nanoparticles may be present in a range of 0.1 to 10 wt% of the negative electrode assembly. The porous matrix may have a porosity of 10 to 50%. The lithiophilic nanoparticles may have an average diameter between 5 and 100 nanometers.

[0004] An electrode assembly comprises a current collector and a graphite-based active material layer, wherein electrocatalytic nanoparticles are distributed between particles of the graphite-based active material layer deposited on the current collector. The graphite-based active material layer may have a porous structure. The electrocatalytic nanoparticles may be silver nanoparticles. The electrocatalytic nanoparticles may be present on surfaces of the graphite-based active material and within pores of the graphite-based active material. The graphite-based active material layer may have a thickness of 50 to 200 micrometers. The electrode assembly may be a negative electrode assembly. The current collector may be a copper foil.

[0005] One method for forming an electrode involves loading nickel nanoparticles into a graphite active material to form a nickel-loaded graphite active material, hydrogenating the nickel-loaded graphite active material to form a porous graphite active material, and electroplating the porous graphite active material with a silver salt solution to exchange nickel nanoparticles for silver nanoparticles to form an electrode. Hydrogenation can be performed in a temperature range of 600 to 900 degrees Celsius. Electroplating can be performed at room temperature. The method may include controlling the radius of the silver nanoparticles by adjusting the amount of silver salt. In other configurations, the method may involve depositing the formed electrode onto a current collector. The porous graphite active material may have an increased surface area compared to the nickel-loaded graphite active material. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of graphite edge activation; Fig. Figure 2 is a schematic representation of lithium diffusion in edge-activated graphite; Fig. Figure 3 is a diagram of the specific capacity and Coulomb efficiency for pure graphite compared to graphite electrodes with added silver; Fig. Figure 4 is a schematic representation of an electrode undergoing electroplating; Fig. Figure 5 is a schematic representation of a reduction reaction in an electrode; and Fig. Figure 6 is a flowchart of a process for forming an electrode with nitrate additive. DETAILED DESCRIPTION

[0006] According to this disclosure, detailed embodiments of the electrode structures, fabrication processes, and battery systems are disclosed in this document. These embodiments are representative of the innovative approach to improving the performance of lithium-ion batteries by modifying graphite active material surfaces with lithiophilic and electrocatalytic nanoparticles, in particular silver nanoparticles. The figures and descriptions provided are for illustrative purposes only and may not represent all possible variations or configurations. Certain features may be enlarged or reduced in size to highlight specific aspects of the electrode assemblies and their fabrication processes.Thus, the disclosed specific structural and functional details are not intended to limit the scope of the invention, but rather to provide a basic basis for the person skilled in the art to implement different embodiments of the claimed subject matter.

[0007] Unless expressly stated otherwise, all numerical values, measurements, percentages, weights, and similar quantitative parameters disclosed in this document are to be understood as being preceded by the term "approximately." This stipulation applies even if the term "approximately" is not explicitly used. The intention is to include variations resulting from standard measurement techniques, manufacturing processes, material properties, and the inherent variability in the performance of electrode structures and battery systems. For example, where reference is made to a porosity of "10 to 50 percent," this range should be interpreted as "approximately 10 to approximately 50 percent," taking into account variations that do not materially alter the functionality or performance of the electrode assemblies or the battery system as a whole.

[0008] The present disclosure relates to an approach for increasing the performance of lithium-ion batteries, addressing in particular the challenges associated with fast charging and battery lifespan. This approach involves modifying graphite active material surfaces with lithiophilic materials, especially silver nanoparticles. The approach can include a two-step process: first, creating a porous structure on the graphite surface, and second, incorporating silver nanoparticles onto this modified surface.

[0009] The process begins with the loading of nickel nanoparticles onto the graphite surface. A hydrogenation step then induces a porous structure through a reaction of nickel with carbon in graphite and hydrogen gas to produce nickel and methane. This reaction increases the edge-plane area, resulting in higher rate capability and enhanced fast-charging properties. Subsequently, the nickel nanoparticles are exchanged for silver nanoparticles via an electroplating process in a silver salt solution. This exchange is driven by the difference in reduction potentials, with nickel ions accepting two electrons at negative 0.26 volts to form nickel metal, while silver ions accepting one electron at 0.80 volts to form silver metal. The resulting silver nanoparticles can be present both on the graphite surface and within the pores generated during the hydrogenation step.

[0010] The increased edge surface area and porosity facilitate lithium incorporation. Silver nanoparticles can form a solid solution with lithium, inhibiting the lithium plating process that contributes to lithium loss and dendrite formation. Additionally, silver nanoparticles exhibit higher electronic conductivity than conventional carbon additives, thus enhancing the overall electrochemical reaction kinetics. The combination of a porous graphite structure and silver nanoparticles can lead to increased fast-charging capabilities compared to unmodified graphite or graphite with silver nanoparticles but no structural modification. The overall processes for producing this modified graphite material can be scaled, making them suitable for industrial applications.The two-stage approach allows control over the graphite structure and the silver nanoparticle distribution, enabling optimization for specific battery requirements.

[0011] Fig. Figure 1 is a schematic representation illustrating a two-step process for modifying graphite particles to create electrode materials. The process begins with unmodified graphite, represented by a solid black circle. In the first step, referred to as "nickel loading," the graphite surface is coated with nickel particles, resulting in nickel-loaded graphite. The second step comprises two sub-steps: Step 1 involves the introduction of hydrogen gas, and Step 2 involves the addition of silver. This process converts the nickel-loaded graphite into silver-loaded graphite, replacing the nickel on the graphite surface with silver particles. This modification process aims to enhance the properties of graphite for use as an electrode material, potentially improving its performance in energy storage applications.

[0012] Fig. Figure 2 shows the structure of graphite with introduced edges for use in lithium-ion battery electrodes. The image shows a cross-section of a modified graphite particle. The particle retains its overall circular shape but is characterized by numerous circular cavities distributed throughout its graphite structure. These cavities represent the introduced edges within the graphite. The figure highlights several advantages of this structure, including reduced expansion and improved lithium-ion mass transport. The introduced edges create spaces within the graphite structure that can accommodate volume changes during lithium insertion and extraction, thereby reducing expansion stresses.Additionally, these edge points improve the mass transport of lithium ions within the graphite, potentially increasing the electrode's performance in terms of charging and discharging capabilities.

[0013] Fig. Figure 3 is a graph comparing the performance of pure graphite electrodes and graphite electrodes with added silver. The graph shows the specific capacity (milliampere-hours per gram) and the coulomb efficiency (percentage) for both electrode types. For each electrode material, the graph shows the three metrics: charge capacity (Chg), discharge capacity (DChg), and coulomb efficiency (CE). The pure graphite electrode exhibits a charge capacity of 310.18 mAh / g and a discharge capacity of 298.88 mAh / g with a coulomb efficiency of 96.36%. In comparison, the graphite electrode with added silver shows improved performance with a charge capacity of 319.20 mAh / g and a discharge capacity of 308.24 mAh / g, along with a higher coulomb efficiency of 96.57%.

[0014] The addition of silver to the graphite electrode leads to a noticeable increase in both the charging and discharging capacities. The charging capacity improves by approximately 9 mAh / g, while the discharging capacity increases by about 9.4 mAh / g. This suggests that the silver additive enhances the electrode's ability to store and release charge. The Coulomb efficiency, a measure of the electrode's charging efficiency, also shows a slight improvement of 0.21 percentage points with the addition of silver. This indicates that the graphite electrode with added silver has a slightly better charge-discharge cycle efficiency compared to the electrode made of pure graphite.

[0015] The improved performance observed with the graphite electrode containing silver can be attributed to several factors. The presence of silver may increase the overall conductivity of the electrode, thus facilitating easier electron transfer during charging and discharging processes.

[0016] Additionally, silver can create more active sites for charge storage or improve the structural stability of the graphite during cycling. The higher Coulomb efficiency suggests that the silver additive can also help reduce irreversible capacity losses during charge-discharge cycles. As shown by the diagram in Fig. As shown in Figure 3, the graphite electrode with added silver exhibits superior performance compared to pure graphite in terms of both capacity and efficiency.

[0017] Fig. Figure 4 is a schematic representation of the electroplating process in a battery electrode structure. The pre-galvanized electrode 10 has a positive electrode assembly 12 and a negative electrode assembly 16, separated by a separator 14. Within the negative electrode assembly 16, cavities 18 and nickel nanoparticles 20 are visible. These cavities 18 and nickel nanoparticles 20 are part of the initial structure of the graphite-based active material layer of the negative electrode assembly 16. A microscopic image of the pre-galvanized electrode 10 shows the porous structure of the negative electrode assembly 16 with nickel nanoparticles 20 distributed within it. The electroplated electrode 22 is shown after the electroplating process. The overall structure of the electroplated electrode 22 remains unchanged, but modifications occur within the negative electrode assembly 16.The nickel nanoparticles 20 were replaced with silver nanoparticles 24 in the cavities 18. The microscopic image, corresponding to the galvanized electrode 22, shows the presence of the silver nanoparticles 24. The silver nanoparticles 24 are distributed throughout the entire assembly 16 of the negative electrode.

[0018] Fig. Figure 5 is a schematic representation of an electrolysis cell setup 26 for electroplating graphite electrodes with silver nanoparticles. A power supply 28 provides the electrical energy required to drive the electroplating process. A graphite electrode 30, serving as the working electrode, is connected by a circuit 32 that allows the flow of electrons 34. The electrons 34 flow from the graphite electrode 30 to a counter electrode 36. Negative and positive terminals 38, 40 of the power supply 28 establish the potential difference that drives the electrochemical reaction. In the electrolysis cell setup 26, silver ions from a silver nitrate solution in the electrolyte are reduced at the surface of the graphite electrode 30, forming silver nanoparticles, while simultaneously oxidizing and exchanging the previously deposited nickel nanoparticles.This galvanic exchange process leads to the formation of silver nanoparticles on the surface and within the pores of the graphite electrode 30.

[0019] Fig.Figure 6 is a flowchart of a process for forming an electrode 42. The first step 44 involves loading nickel nanoparticles into a graphite active material to form a nickel-loaded graphite active material. In this first step, the graphite substrate is prepared with nickel nanoparticles, which will serve as a precursor for the subsequent modifications. The second step 46 involves hydrogenating the nickel-loaded graphite active material to form a porous graphite active material. This hydrogenation process may involve exposing the nickel-loaded graphite to hydrogen gas under specific conditions, resulting in the creation of a porous structure within the graphite. This increases the surface area and creates additional sites for the final modification.The third step, 48, involves electroplating the porous graphite active material with a silver salt solution to exchange nickel nanoparticles for silver nanoparticles, thereby forming the electrode. This electroplating process replaces the nickel nanoparticles with silver nanoparticles.

[0020] While the specific embodiments of the electrode structures, methods for forming such structures, and the resulting battery systems have been described in detail, these embodiments are not exhaustive for all possible configurations. The formulations used in this description are for descriptive purposes and are not intended to limit the scope of protection of the invention. Modifications and variations may occur without deviating from the core concepts of the invention described in this document. Furthermore, the features and elements of different disclosed embodiments may be combined in novel ways to form additional embodiments within the scope of the claimed subject matter, even if such combinations are not expressly described in this document.

[0021] According to the present invention, a battery is provided comprising: a positive electrode assembly and a negative electrode assembly with a porous matrix of graphite-based active material and lithiophilic nanoparticles occupying pores defined by the porous matrix.

[0022] According to one embodiment, the lithiophilic nanoparticles are silver nanoparticles.

[0023] According to one embodiment, the lithiophilic nanoparticles are configured to form a solid solution containing lithium in the negative electrode assembly.

[0024] According to one embodiment, the porous matrix of graphite-based active material has an increased edge surface area compared to non-porous graphite-based active material.

[0025] According to one embodiment, the lithiophilic nanoparticles are present in a range of 0.1 to 10 weight percent of the negative electrode assembly.

[0026] According to one embodiment, the porous matrix has a porosity of 10 to 50 percent.

[0027] According to one embodiment, the lithiophilic nanoparticles have an average diameter between 5 and 100 nanometers.

[0028] According to one embodiment, an electrode assembly is provided comprising: a current collector; and a graphite-based active material layer, wherein electrocatalytic nanoparticles are distributed between particles of the graphite-based active material layer deposited on the current collector.

[0029] According to one embodiment, the graphite-based active material layer has a porous structure.

[0030] According to one embodiment, the electrocatalytic nanoparticles are silver nanoparticles.

[0031] According to one embodiment, the electrocatalytic nanoparticles are present both on surfaces of the graphite-based active material layer and within pores of the graphite-based active material layer.

[0032] According to one embodiment, the graphite-based active material layer has a thickness of 50 to 200 micrometers.

[0033] According to one embodiment, the electrode assembly is a negative electrode assembly.

[0034] According to one embodiment, the current collector is a copper foil.

[0035] According to the present invention, a method for forming an electrode comprises: loading nickel nanoparticles into a graphite active material to form a nickel-loaded graphite active material; hydrogenating the nickel-loaded graphite active material to form a porous graphite active material; and electroplating the porous graphite active material with a silver salt solution to exchange nickel nanoparticles for silver nanoparticles to form the electrode.

[0036] In one aspect of the invention, hydrogenation is carried out in a temperature range of 600 to 900 degrees Celsius.

[0037] In one aspect of the invention, electroplating is carried out at room temperature.

[0038] In one aspect of the invention, the method involves controlling the radius of the silver nanoparticles by adjusting the amount of silver salt.

[0039] In one aspect of the invention, the method involves depositing the formed electrode onto a current collector.

[0040] In one aspect of the invention, the porous graphite active material has an increased surface area compared to the nickel-loaded graphite active material.

Claims

[1] Battery, comprising: a positive electrode assembly; and a negative electrode assembly with a porous matrix of graphite-based active material and lithiophilic nanoparticles occupying pores defined by the porous matrix. [2] Battery according to claim 1, wherein the lithiophilic nanoparticles are silver nanoparticles. [3] Battery according to claim 1, wherein the lithiophilic nanoparticles are configured to form a solid solution with lithium in the negative electrode assembly. [4] Battery according to claim 1, wherein the porous matrix of graphite-based active material has an increased edge surface area compared to non-porous graphite-based active material. [5] Battery according to claim 1, wherein the lithiophilic nanoparticles are present in a range of 0.1 to 10 weight percent of the negative electrode assembly. [6] Battery according to claim 1, wherein the porous matrix has a porosity of 10 to 50 percent. [7] Battery according to claim 1, wherein the lithiophilic nanoparticles have an average diameter between 5 and 100 nanometers. [8] Electrode assembly comprising: a power collector; and a graphite-based active material layer, wherein electrocatalytic nanoparticles are distributed between particles of the graphite-based active material layer deposited on the current collector. [9] Electrode assembly according to claim 8, wherein the graphite-based active material layer has a porous structure. [10] Electrode assembly according to claim 8, wherein the electrocatalytic nanoparticles are silver nanoparticles. [11] Electrode assembly according to claim 8, wherein the electrocatalytic nanoparticles are present both on surfaces of the graphite-based active material layer and within pores of the graphite-based active material layer. [12] Electrode assembly according to claim 8, wherein the graphite-based active material layer has a thickness of 50 to 200 micrometers. [13] Electrode assembly according to claim 8, wherein the electrode assembly is an assembly of a negative electrode. [14] Electrode assembly according to claim 8, wherein the current collector is a copper foil. [15] Method for forming an electrode, comprising: Loading nickel nanoparticles into a graphite active material to form a nickel-loaded graphite active material; Hydrogenation of the nickel-loaded graphite active material to form a porous graphite active material; and Electroplating the porous graphite active material with a silver salt solution to exchange nickel nanoparticles with silver nanoparticles to form the electrode.

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