Aluminum ion battery system of Al-Cu-Mg ternary eutectic negative electrode material

Abstract

The invention discloses an aluminum ion battery system of an Al-Cu-Mg ternary eutectic negative electrode material, and belongs to the technical field of batteries, the negative electrode of the battery system is the Al-Cu-Mg ternary eutectic material, the positive electrode material is a graphite-based material, and the negative electrode material is an Al-Cu-Mg ternary eutectic material. And the electrolyte is aluminum chloride and triethylamine hydrochloride. The ternary eutectic negative electrode with a unique structure has relatively high conductivity, maintains the stability of the aluminum charge-discharge process, solves the problem that dendritic crystals are easy to appear in the circulation of a pure aluminum negative electrode, can stably circulate for more than 2500 times at a high rate of 10C, and keeps the capacity at 75mAh g <-1 >.

Description

Technical Field

[0001] The invention relates to an ionic liquid system aluminum ion battery using an Al-Cu-Mg ternary eutectic alloy as a negative electrode material, belonging to the technical field of batteries. Background Art

[0002] With the adjustment of energy structures, the demand for high-performance energy storage devices is increasing. Lithium-ion batteries, as a commercially available energy storage system, have dominated the energy storage market. However, with the increasing production and widespread application of lithium-ion batteries, their shortcomings have gradually become apparent. Limited lithium reserves and uneven geographical distribution have led to rising costs for lithium-ion batteries. Furthermore, unresolved issues such as the poor safety of organic electrolytes and long charging times have seriously hampered their application. Consequently, researchers have shifted their focus to other resource-rich and high-performance alternative battery technologies, such as magnesium-ion batteries, aluminum-ion batteries, sodium-ion batteries, and potassium-ion batteries. Among various metal anode materials, aluminum has the lowest price and is the most abundant metal element in the Earth's crust. Its electrochemical equivalent and gravimetric specific capacity are slightly higher and lower than those of lithium, respectively. Therefore, aluminum-ion batteries have naturally become a major focus of current development and research.

[0003] Aqueous aluminum ion batteries have a narrow electrochemical window, and the hydrogen / oxygen evolution reactions that occur during charge and discharge affect the battery's cycle stability. The gas generated inside the sealed battery can easily cause safety issues. Ionic liquid-based aluminum ion batteries have significantly improved their service life and offer advantages such as high safety, long life, rapid charge and discharge, and a wide electrochemical window. Therefore, ionic liquid-based aluminum ion batteries have a very broad development prospect. However, the commonly used aluminum chloride / 1-ethyl-3-methylimidazolium chloride ionic liquid is expensive and highly corrosive. Using aluminum chloride / triethylamine hydrochloride ionic liquid instead of aluminum chloride / 1-ethyl-3-methylimidazolium chloride ionic liquid is relatively less corrosive and inexpensive, costing only one-eighth the price of aluminum chloride / 1-ethyl-3-methylimidazolium chloride ionic liquid.

[0004] Pure aluminum is the most widely used anode in ionic liquid aluminum-ion batteries. A passive oxide layer easily forms on the surface of pure aluminum, resulting in uneven current density on the electrode surface, affecting metal deposition, accelerating dendrite growth, and also affecting stripping / electroplating performance. The Al-Cu-Mg ternary eutectic presented in this article is composed of lamellar Al and Al2CuMg, and a small amount of rod-shaped Al and Al2Cu. Al serves as the active material layer, providing an Al source, while the intermetallic compounds Al2Cu and Al2CuMg phase guide and promote the deposition and dissolution of aluminum. The Al-Cu-Mg ternary eutectic alloy material can inhibit the formation of passive oxides and has good cycle stability, stripping / electroplating performance, and rate performance. At a high rate of 10C, the capacity retention rate exceeds 90% after 2500 cycles, indicating that the alloy anode has great application potential in improving the electrochemical performance of ionic liquid aluminum-ion batteries. Summary of the Invention

[0005] The purpose of the present invention is to improve the storage capacity, cycle stability and rate performance of aluminum ion batteries. This article provides a method for preparing an Al-Mg-Cu ternary eutectic alloy negative electrode and its application in non-aqueous ionic liquid aluminum ion batteries.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The Al-Cu-Mg ternary eutectic electrode is used as the negative electrode of a non-aqueous aluminum ion battery, the positive electrode material is a graphite-based material, and the electrolyte is an ionic liquid formed by mixing aluminum chloride and triethylamine hydrochloride at room temperature.

[0008] The positive electrode is prepared by uniformly stirring the graphite positive electrode active material, a conductive agent, and a binder in an organic solvent to form a slurry, dropping the slurry onto a molybdenum sheet, and then drying in a vacuum drying oven to produce the positive electrode. Based on the total mass of the graphite positive electrode active material, the conductive agent, and the binder being 100%, the added mass percentage of the graphite positive electrode active material is preferably 70-90%; the added mass percentage of the conductive agent is preferably 5-15%; and the added mass percentage of the binder is preferably 5-15%. The mass ratio of the organic solvent to the graphite positive electrode active material is preferably 5:1-10:1.

[0009] Preferably, the electrolyte is an ionic liquid formed by mixing aluminum chloride and triethylamine hydrochloride at room temperature, and is prepared by mixing aluminum chloride / triethylamine hydrochloride in a ratio of 1.2:1 to 1.8:1. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 XRD pattern of the prepared Al-Cu-Mg ternary eutectic alloy anode

[0011] Figure 2 The Al-Cu-Mg ternary eutectic alloy negative electrode symmetric battery is at 0.5 mA cm -2 Time-voltage curves at different current densities.

[0012] Figure 3 The asymmetric battery with Al-Cu-Mg ternary eutectic alloy as negative electrode was deposited at a current of 0.5 mA cm -2 , the stripping / plating curve of the 50th cycle with a deposition time of 0.5h and a stripping cutoff potential of 0.8V.

[0013] Figure 4 The Al-Cu-Mg ternary eutectic alloy negative electrode and graphite positive electrode full battery at 3720mA g -1 (10C) charge and discharge curves at current density.

[0014] Figure 5 The Al-Cu-Mg ternary eutectic alloy negative electrode and graphite positive electrode full battery at 3720mA g -1 (10C) Cycle-efficiency diagram at different current densities.

[0015] Figure 6 This is the SEM image of the Al-Cu-Mg ternary eutectic alloy negative electrode before cycling. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further explained and illustrated in the following by means of specific embodiments.

[0017] Example 1

[0018] Preparation of Al-Cu-Mg ternary eutectic anode:

[0019] 1) Weigh pure aluminum ingots, pure copper ingots, and pure magnesium ingots according to a ratio of 61.6% Al, 30.4% copper, and 8% magnesium, and remove the surface oxide layer;

[0020] 2) Put the three metals into the melting furnace together;

[0021] 3) Heat to 1200°C, ensure the metal is completely melted and keep warm for 5 minutes;

[0022] 4) Using circulating water in the mold to cool the high-temperature liquid metal to room temperature at a cooling rate of 300k / s;

[0023] 5) Cut the completely cooled metal block into 1mm thick slices on an EDM CNC cutting machine and grind to remove impurities and oxide layer on the surface.

[0024] Preparation of the positive electrode: The graphite positive electrode material, the conductive additive and the adhesive are dissolved in an organic solvent solution to prepare a slurry, the slurry is dropped onto the molybdenum sheet current collector, and vacuum dried; further, the mass ratio of the battery positive electrode material to the conductive additive and the adhesive is 8:1:1.

[0025] The conductive additive, which can be acetylene black, is added during the production of battery positive electrode materials to improve physical contact between active electrode particles or between active electrode particles and the carbon cloth current collector, thereby reducing ohmic resistance. Polyvinylidene fluoride (PVDF) is a commonly used binder in electrode production. It is used to enhance adhesion between active materials, between active materials and conductive agents, and between active materials and current collectors (where the active material is graphite), mitigating active material loss during charge and discharge cycles.

[0026] Preparation of electrolyte: Aluminum chloride / triethylamine hydrochloride were mixed in a molar ratio of 1.5:1 to prepare an ionic liquid electrolyte.

[0027] The Al-Cu-Mg ternary eutectic negative electrode and the glass fiber separator were placed in a battery mold, and aluminum chloride / triethylamine hydrochloride electrolyte was dripped into the battery to form a symmetrical battery. -2 The current density was used for constant current charge and discharge test (voltage-time curve), and the overpotential did not exceed 70mV.

[0028] The Al-Cu-Mg ternary eutectic negative electrode, molybdenum sheet, and glass fiber separator were placed in a battery mold, and aluminum chloride / triethylamine hydrochloride electrolyte was dripped into it to assemble an asymmetric battery with a deposition current of 0.5 mA cm -2 , the deposition time is 0.5h, the stripping cutoff potential is 0.8V for stripping / electroplating test, and the stripping electroplating efficiency is greater than 98%.

[0029] The Al-Cu-Mg ternary eutectic negative electrode, graphite positive electrode and glass fiber separator were placed in a battery mold, and aluminum chloride / triethylamine hydrochloride electrolyte was dripped into the battery mold. The rechargeable aluminum ion full battery with aluminum chloride / triethylamine hydrochloride ionic liquid as electrolyte was assembled into an ionic liquid system at 3720 mA g -1 The constant current charge and discharge test was carried out under the current density of 0.3-2.35V. The residual specific capacity was 75mAh g after 2500 charge and discharge cycles. -1 .

[0030] Example 2

[0031] Preparation of Al-Cu-Mg ternary eutectic anode:

[0032] 1) Weigh pure aluminum ingots, pure copper ingots, and pure magnesium ingots according to a ratio of 61.6% Al, 30.4% copper, and 8% magnesium, and remove the surface oxide layer;

[0033] 2) Put the three metals into the melting furnace together;

[0034] 3) Heat to 1200°C, ensure the metal is completely melted and keep warm for 5 minutes;

[0035] 4) Using circulating water in the mold to cool the high-temperature liquid metal to room temperature at a cooling rate of 300k / s;

[0036] 5) Cut the completely cooled metal block into 1mm thick slices on an EDM CNC cutting machine and grind to remove impurities and oxide layer on the surface.

[0037] Other details are as in Example 1.

[0038] Al-Cu-Mg ternary eutectic anode-graphite cathode full cell at 3720 mA g -1 Cross-current charge and discharge tests were conducted at a current density of 0.3-2.35V. The remaining specific capacity after 2500 charge and discharge cycles was 76.8mAh g -1 The strengthening phases s-Al2CuMg and θ-Al2Cu in the Al-Cu-Mg ternary eutectic negative electrode act together as a rigid support framework, which can disperse the stress of the aluminum negative electrode, synergistically stabilize the electrode structure, and form a stable solid / electrolyte interface. The α-Al phase acts as an active material to provide the active material Al required for aluminum stripping / electroplating. 3+ The intermetallic compounds Al2Cu phase and Al2CuMg phase form galvanic pairs with α-Al, providing a stronger driving force for the stripping / electroplating of aluminum.

[0039] At a current density of 5 C, the C / / Al-Cu-Mg full battery can stably cycle for more than 1,600 cycles, with a specific capacity stable at around 78 mAh / g, a coulombic efficiency close to 100%, and exhibits excellent rate performance. EIS test results show that the C / Al-Cu-Mg full battery has a relatively small interface impedance, verifying that the addition of magnesium can optimize the electrode interface performance and form a stable solid / electrolyte interface.

[0040] The above is only an exemplary embodiment of the present disclosure and is not intended to limit the scope of the present disclosure. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. Those skilled in the art will easily think of other embodiments of the present disclosure after considering the specification and practicing the disclosure herein. Considering that these embodiments can be combined with each other in various combinations or arrangements, the description and examples are to be regarded as exemplary only. The scope of this application should be determined with reference to the appended claims and the full scope of equivalents to which these claims are entitled, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. An aluminum ion battery system with an Al-Cu-Mg ternary eutectic negative electrode material, characterized by: The negative electrode is Al-Cu-Mg ternary eutectic material, the positive electrode material is graphite-based material, the electrolyte is aluminum chloride and triethylamine hydrochloride, the current collector is molybdenum sheet, the diaphragm is glass fiber filter paper, and the battery shell is Swagelok battery shell.

2. The aluminum ion battery system of the Al-Cu-Mg ternary eutectic negative electrode material according to claim 1, characterized in that: Calculated by mass percentage, the Al-Cu-Mg ternary eutectic negative electrode material is 61.6% Al, 30.4% Cu, and 8% Mg.

3. The Al-Cu-Mg ternary eutectic negative electrode material according to claim 2, characterized in that: The microstructure is composed of lamellar eutectic structures of α-Al and Al2CuMg, and a small amount of rod-shaped α-Al and Al2Cu.

4. The aluminum ion battery system of the Al-Cu-Mg ternary eutectic negative electrode material according to claim 1, characterized in that: The graphite-based positive electrode material is obtained by uniformly dispersing graphite, a conductive agent, and a binder in an organic solvent to form a slurry, which is then dripped onto a molybdenum sheet and finally dried; wherein the mass percentage of graphite is 70-90%, the mass percentage of the conductive agent is 5-15%, and the mass percentage of the binder is 5-15%.

5. The aluminum ion battery system of the Al-Cu-Mg ternary eutectic negative electrode material according to claim 1, characterized in that: The electrolyte is prepared by mixing anhydrous aluminum chloride and triethylamine hydrochloride in a molar ratio of 1.2:1 to 1.8:

1. The preparation method is to slowly add anhydrous aluminum chloride to triethylamine hydrochloride in portions and continuously stir; the system temperature is controlled below 50°C during the entire process, and the formed ionic liquid electrolyte is allowed to stand in a glove box for 12 hours before use.

6. The aluminum ion battery system of the Al-Cu-Mg ternary eutectic negative electrode material according to claim 1, characterized in that: The assembly steps of aluminum ion batteries are as follows: (1) Graphite, conductive agent, and binder are weighed and mixed in proportion to make an active material slurry, which is evenly added dropwise onto the positive electrode current collector and dried to form a sheet-like positive electrode with a thickness of 0.8-1.5 mm; (2) ultrasonically clean the negative electrode with anhydrous ethanol and then dry it; (3) Assembling the positive electrode, negative electrode, electrolyte, separator and battery shell in a glove box to obtain an aluminum ion battery; (4) After the aluminum ion battery is assembled, it must be left to stand for at least 8 hours before use.

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