CN108963388A - A kind of method improving lithium-air battery energy density and output power and the lithium-air battery based on this method - Google Patents

Abstract

The invention provides a method for improving the energy density and output power of a lithium-air battery and a lithium-air battery based on the method. The method is based on the structure of the traditional lithium-air battery, adding lithium intercalation electrode materials to the air electrode to form an air/lithium intercalation hybrid electrode. The lithium intercalation material used has the function of an ORR catalyst, and has high-rate lithium intercalation characteristics, and has the characteristic that the working voltage is lower than the ORR reaction voltage. During the discharge process, the energy density of the lithium-air battery is increased through the ORR catalysis of the lithium-intercalation electrode material, and the output power of the battery is increased through the high-rate lithium-intercalation characteristics of the lithium-intercalation electrode material. In addition, after high-power discharge, the lithium intercalation material can be restored to its original state through a spontaneous oxidation reaction, ensuring that the power of the battery can be regenerated without charging. The present invention has great application value in the field of energy storage power supply requiring high specific energy and high power, especially in the field of electric vehicles.

Description

A method for improving the energy density and output power of lithium-air batteries and based on the method lithium-air battery

technical field

The invention belongs to the field of lithium-air batteries, and in particular relates to improving the energy density and output power of lithium-air batteries.

Background technique

In recent years, with the rapid development of industries such as portable electronic devices, smart grid connection and new energy vehicles, chemical energy storage power supplies, especially lithium-ion batteries, have been widely used. At present, the development of high specific energy-high power energy storage power supply has become the focus of the scientific and industrial circles, especially in the field of electric vehicles. However, even the best lithium-ion batteries currently have an energy density of only 250-300Wh kg ^-1 , which still cannot meet the needs of the future market. It is crucial to develop new batteries beyond lithium-ion batteries. An alternative way is to develop lithium oxygen (air) gas. The theoretical energy density of lithium-oxygen (air) air batteries is as high as ~3500Wh kg ^-1 , which is almost 10 times higher than that of lithium-ion batteries with the highest energy density at present. It has shown great application value and has been extensively studied all over the world. With the unremitting efforts of a large number of scientific researchers, a single lithium-air battery with an energy density of 500-800Wh kg ^-1 has been prepared. For example, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has publicly reported a lithium-air battery with an energy density as high as 523Wh kg ^-1 .

However, lithium-air batteries suffer from low energy efficiency, poor charge transfer capability for ORR and OER, and low practical energy density. In order to solve these problems, a widely used method is to prepare highly efficient ORR and OER catalysts, by lowering the reaction energy barrier and changing the reaction microscopic process, thereby reducing the polarization during the charge and discharge process. This method can effectively improve the energy density of the battery. However, the ORR reaction is essentially a slow process, and lithium-air batteries are difficult to discharge at high currents, so they cannot provide high power output. Correspondingly, as a lithium-based battery, a lithium-ion battery can achieve high power output through high-rate electrode materials. For example, LiFePO ₄ and LiMn ₂ O ₄ are widely used. However, their operating voltage (>3.5V) is higher than that of the ORR reaction (<2.9V), and when applied to lithium-air batteries, they always preferentially participate in the reaction and cannot achieve high power output when needed role. Therefore, this type of material is not suitable for application in lithium-air batteries.

Contents of the invention

The object of the present invention is to address the deficiencies in the prior art, to provide a method for improving the energy density and output power of lithium-air batteries and a lithium-air battery based on the method, so as to further increase the energy density of lithium-air batteries and improve the performance of lithium-air batteries. high power output capability.

The idea of the present invention is as follows: on the basis of the traditional lithium-air battery structure, a lithium intercalation electrode material is added to the air electrode (active material with ORR reaction) to form an air/lithium intercalation hybrid electrode. The lithium intercalation material used has the function of an ORR catalyst, and has high-rate lithium intercalation characteristics, and has the characteristic that the working voltage is lower than the ORR reaction voltage. During the discharge process, the energy density of the lithium-air battery is increased through the ORR catalysis of the lithium-intercalation electrode material, and the output power of the battery is increased through the high-rate lithium-intercalation characteristics of the lithium-intercalation electrode material. In addition, after high-power discharge, the lithium intercalation material can be restored to its original state through a spontaneous oxidation reaction, ensuring that the power of the battery can be regenerated without charging. The invention has great application value in the field of energy storage power supply requiring high specific energy and high power, especially in the field of electric vehicles.

Based on the above ideas, the method for improving the energy density and output power of lithium-air batteries provided by the present invention is: additionally adding lithium-intercalating electrode materials to the air electrode of lithium-air batteries to form an air/lithium-intercalating hybrid positive electrode, the lithium-intercalating type The electrode material has three characteristics: ORR catalytic activity, high rate lithium intercalation characteristics and working voltage lower than ORR reaction voltage.

In the above solution, further, the lithium intercalation electrode material is one of TiO ₂ , TiS ₂ , LiTi ₂ (PO ₄ ) ₃ , Li ₂ Ti ₃ O ₇ , Li ₄ Ti ₅ O ₁₂ , and TiP ₂ O ₇ .

In the above scheme, further, the method of adding lithium intercalation electrode material to the air electrode of lithium air battery is: mechanically mix the active material of ORR reaction and lithium intercalation electrode material, and coat it on the foamed nickel or carbon paper current collector , forming an air/lithium intercalation hybrid electrode; or coating the active material of the ORR reaction and the lithium intercalation electrode material on both sides of the nickel foam or carbon paper current collector to form an air/lithium intercalation hybrid electrode, and in the battery seal When combining, the ORR reactive material is close to the air side, and the lithium intercalation electrode material is close to the separator side.

In the above solution, further, the active material of the ORR reaction is one of graphene, SP carbon, KB carbon, carbon nanotube and carbon fiber.

The lithium-air battery with air/lithium intercalation hybrid electrode as the positive electrode produced by the above method is composed of air/lithium intercalation hybrid positive electrode, negative electrode, diaphragm, and electrolyte assembly; the internal environment of the battery is pure oxygen environment, or contains oxygen. An inert gas environment, or the positive electrode is in an oxygen-containing environment. When the air/lithium intercalation hybrid positive electrode is made by coating the ORR reactive material and the lithium intercalation electrode material on both sides of the foamed nickel or carbon paper collector respectively, in the assembled battery, the ORR reactive active The side of the material faces the air, and the side of the lithium-intercalated electrode material faces the separator.

In the lithium-air battery above, the negative electrode is lithium metal, or a lithium intercalation electrode material such as graphite, or a lithium alloy material such as silicon.

For the above lithium-air battery, the electrolyte is one of 1mol L ^-1 LiTFSI-DME, 1mol L ^-1 LiTFSI-TEGDME, and 1mol L ^-1 LiTFSI-DMSO.

For the above-mentioned lithium-air battery, the diaphragm is a glass fiber diaphragm, or a polymer diaphragm used in a lithium-ion battery.

The above-mentioned lithium-air battery has an operating voltage range of 1.0-4.5V.

According to the concept of the present invention, when the lithium-air battery only needs to utilize the high power characteristics of the lithium intercalation material, and in order to avoid the passivation of the lithium intercalation material by the ORR reaction product, the lithium intercalation electrode material is coated on the surface of the aluminum foil or nickel foam current collector , used as a separate high-power cathode. When assembling the battery, the high-power positive electrode and the air positive electrode of the lithium-air battery are respectively placed on both sides of the negative electrode of the battery to form a lithium-air battery structure with one negative electrode and two positive electrodes. The lithium intercalation electrode material, the air electrode ORR active material, the negative electrode material, the electrolyte and the diaphragm are the materials listed above. During the working process of the battery, the air positive electrode provides high energy output, and the lithium intercalated material positive electrode provides high power output.

The working mechanism of the lithium-air battery based on the mixed positive electrode of the present invention: when discharging with a small current, since the working voltage of the ORR reaction is higher than that of the lithium-intercalated electrode material, the ORR plays the role of energy output preferentially, thereby ensuring The characteristics of high specific energy of lithium-air batteries. At the same time, since the lithium intercalation material acts as an ORR catalyst, the ORR discharge voltage and discharge capacity can be increased, further increasing the energy density of the battery. When discharging at high current, the voltage drops rapidly to the working voltage range of Li-intercalation electrode materials due to the slow kinetics of ORR which cannot meet the high power output. At this time, the lithium intercalation material will provide high power output through its excellent high power performance. When the high power output is completed, in addition to the ORR reaction continuing to provide energy output, since there is a voltage difference between the lithium intercalation electrode material and the ORR reaction, it can be restored to the initial state through the spontaneous oxidation reaction with _O2 , ensuring recycling of the material. All lithium-air batteries prepared by using the above-mentioned working mechanism belong to the protection category of this patent.

Compared with the prior art, the present invention has the following beneficial effects:

1. On the basis of the high specific energy characteristics of the lithium-air battery, the present invention integrates the electrode material (lithium-intercalated electrode material) with high rate characteristics in the lithium-ion battery into the lithium-air battery system, aiming at the deficiency of its power performance, A lithium-air battery with both high specific energy and high power performance has been prepared, which can be used in the field of high specific energy-high power energy storage power supply, especially in the field of electric vehicles.

2. Based on the idea of the present invention, lithium is used as the negative electrode material, 1mol L ^-1 LiTFSI-TEGDME is used as the electrolyte, SP carbon is used as the active material for ORR reaction, and bronze-type TiO ₂ (TiO ₂ (B)) is used as the high-rate intercalation As a lithium material, a lithium-air battery with an O ₂ /TiO ₂ (B) hybrid positive electrode is constructed. The energy-power diagram obtained from the test is shown in Figure 1. It can be seen that the lithium-air battery with O ₂ /TiO ₂ (B) hybrid cathode not only has higher energy density than the traditional O ₂ (SP) cathode-based lithium-air battery, but also greatly improves the power density.

Description of drawings

Figure 1 is a lithium-air battery with O ₂ (SP)/TiO ₂ (B) hybrid positive electrode, a lithium-air battery with a traditional O ₂ (SP) positive electrode, and a lithium-ion battery with TiO ₂ (B) positive electrode, 3 The energy-power comparison diagram of the battery.

Figure 2(a) is a lithium-air battery with a conventional O ₂ (SP) positive electrode, (b) is a lithium-air battery with an O ₂ (SP)/TiO ₂ (B) mixed positive electrode, constant current at different current densities discharge curve.

3 is a schematic diagram of the lithium-air battery described in Example 1.

Detailed ways

The description of the present invention will be further described below through specific embodiments. The following examples are the experimental results of the selectivity of three different battery structures based on the idea of the present invention, but the scope of the claims of the present invention is not limited thereto. According to the basic features and theoretical basis of the present invention defined in the claims, any improved forms made by those skilled in the art all belong to the scope of the claims of the present invention.

Example 1

The negative electrode is lithium metal, the ORR active material is SP carbon, the high rate lithium intercalation electrode material is TiO ₂ (B), and the electrolyte is 1mol L ^-1 LiTFSI-TEGDME. SP carbon and TiO ₂ (B) are coated on both sides of the positive current collector, respectively. SP carbon is closer to the air side, and TiO ₂ (B) is closer to the separator side.

Preparation of SP electrode: The active material SP carbon and the binder PVDF are mixed according to the mass ratio of 90:10, ground evenly in an agate mortar, then an appropriate amount of NMP is dropped into a slurry, and then put into an ultrasonic disperser Disperse for 1h. The obtained mixed slurry was coated on the surface of nickel foam, and then dried in a vacuum oven at 120° C. for 10 h to obtain the SP positive electrode.

Preparation of TiO ₂ (B) electrode: mix the active material TiO ₂ (B), conductive agent SP carbon, and binder PVDF according to the mass ratio of 80:10:10, grind them evenly in an agate mortar, and then drop Add an appropriate amount of NMP to make a slurry, and then put it into an ultrasonic disperser to disperse for 1 hour. The obtained mixed slurry is coated on the surface of the nickel foam, and then dried in a vacuum oven at 120° C. for 10 hours to obtain the required TiO ₂ (B) positive electrode.

Preparation of O ₂ (SP)/TiO ₂ (B) mixed electrode: First, according to the preparation requirements of the above-mentioned SP electrode, the mixed slurry of the SP electrode is obtained, coated on one side of the nickel foam, and then in a vacuum drying oven, 120 °C for 10 h to obtain a positive electrode containing SP carbon on one side; then, according to the preparation requirements of the above-mentioned TiO ₂ (B) electrode, obtain a mixed slurry of TiO ₂ (B) electrode, which is coated on the other side of the positive electrode, that is, without The side containing SP carbon is then dried in a vacuum oven at 120°C for 10 hours to obtain a mixed electrode.

In the preparation of the above electrodes, the loading amount of each active material was 1 mg cm ^-2 , whether it was a single SP positive electrode and a single TiO ₂ (B) positive electrode, or both sides of the mixed positive electrode.

The prepared positive electrode, lithium negative electrode, separator glass fiber, electrolyte solution 1molL ^-1 LiTFSI-TEGDME are assembled in a glove box with oxygen content and water content <0.1ppm to complete the battery assembly.

The assembled battery was left to stand for more than 24 hours, and then oxygen with a purity of 99.99% was introduced into the battery at a pressure of 0.02 MPa. Under the condition that the current density is 0.05-6.00mA cm _cathode ^-2 and the discharge cut-off voltage is 1.0V, the discharge performance of the battery is tested.

The discharge curve obtained from the test is shown in Figure 2. It can be seen from the figure that the capacity of the O ₂ (SP)/TiO ₂ (B) hybrid cathode is significantly higher than that of the pure SP cathode when discharged at the same current density. For example, when discharged at 0.05mAcm _cathode ^-2 , the capacity of the hybrid electrode is 3.38mAh cm _cathode ^-2 , which is higher than the 2.00mAh cm _cathode ^-2 of the traditional SP cathode. In addition, it can also be seen from the figure that the rate performance of the hybrid cathode has been significantly improved. When the current density is higher than ^2.00 mA cm _cathode , the conventional SP cathode can hardly discharge. But the maximum current density of mixed electrode can reach 6.00mA cm _cathode ^-2 .

The energy-power data obtained from the test is shown in Figure 1. It can be seen from the figure that the highest power of the O ₂ (SP)/TiO ₂ (B) hybrid cathode is 11mW cm _cathode ^-2 , which is 2.75 times that of the traditional SP cathode ((4mW cm _cathode ^-2 ). The hybrid cathode The highest energy density is 8mWh cm _cathode ^-2 , which is higher than 5mWh cm _cathode ^-2 of the traditional SP positive electrode. The data fully confirm the feasibility of the present invention.

Example 2

The negative electrode is metallic lithium, the ORR active material is SP carbon, the high-rate lithium intercalation material is TiO ₂ (B), and the electrolyte is 1mol L ^-1 LiTFSI-TEGDME. SP carbon and TiO ₂ (B) were mechanically mixed and coated on the surface of nickel foam to prepare a hybrid cathode.

Preparation of the positive electrode: The active material SP carbon, the active material TiO ₂ (B), and the binder PVDF were mixed according to the mass ratio of 50:40:10, and were ground evenly in an agate mortar, and then an appropriate amount of NMP was added to form slurry, and then placed in an ultrasonic disperser to disperse for 1 h. The obtained mixed slurry was coated on the surface of nickel foam, and then dried in a vacuum oven at 120° C. for 10 h to obtain the desired mixed positive electrode.

The assembly of the battery, the test method and conditions of the battery are as described in Example 1.

The highest power density of the lithium-air battery assembled from the mixed positive electrode is 10mW cm _cathode ^-2 , and the highest energy density is 9mWh cm _cathode ^-2 .

Example 3

The negative pole is metal lithium, the ORR reaction active material is SP carbon, the high-power lithium intercalation material is TiO ₂ (B), and the electrolyte is 1mol L ^-1 LiTFSI-TEGDME. The electrode composed of SP carbon is used as the air positive electrode, and the electrode composed of TiO ₂ (B) is used as the high-power positive electrode, which are respectively placed on both sides of the lithium sheet.

The preparation of the SP electrode and the preparation of the TiO ₂ (B) electrode are as described in Example 1.

The prepared SP electrode and TiO ₂ (B) electrode, negative electrode lithium, separator glass fiber, and electrolyte solution 1mol L ^-1 LiTFSI-TEGDME were assembled in a glove box with oxygen content and water content <0.1ppm. The battery is composed of two positive electrodes, SP electrode and TiO ₂ (B) electrode, respectively placed on both sides of the common negative electrode lithium. Wherein, the SP cathode-diaphragm-lithium constitutes a lithium-air battery-like structure, and the TiO ₂ (B) cathode-diaphragm-lithium constitutes a lithium-ion battery-like structure.

The assembled battery was left to stand for more than 24 hours. Before the test, on the side of the air electrode, oxygen with a purity of 99.99% was introduced at a pressure of 0.02MPa. When testing, connect the two positive poles together as a common positive pole. The test is carried out under the condition that the current density is 0.05-6.00mA cm _cathode ^-2 and the discharge cut-off voltage is 1.0V.

The highest power density of the obtained lithium-air battery is 12mW cm cathode ^-2 , and the highest energy density is _{7mWhcm cathode} ^-2 .

Claims (9)

1. a kind of method for improving lithium-air battery energy density and output power, it is characterised in that in air electrode of lithium air battery It is middle that embedding lithium type electrode material is added, air/embedding lithium mixed type anode is formed, the embedding lithium type electrode material has ORR catalysis and lives Property, the embedding lithium characteristic of high magnification and operating voltage be lower than 3 kinds of characteristics of ORR operating voltage.

2. according to raising lithium-air battery energy density described in claim 1 and the method for output power, it is characterised in that described embedding Lithium type electrode material is TiO₂、TiS₂、LiTi₂(PO₄)₃、Li₂Ti₃O₇、Li₄Ti₅O₁₂、TiP₂O₇One of.

3. the method according to claim 1 or claim 2 for improving lithium-air battery energy density and output power, which is characterized in that The method of embedding lithium type electrode material is added in air electrode of lithium air battery are as follows: by the active material of ORR reaction and embedding lithium type electricity The mixing of pole material mechanical, and be coated on nickel foam or carbon paper collector, form air/embedding lithium mixed type electrode；Or it is ORR is anti- The active material and embedding lithium type electrode material answered are respectively coated in nickel foam or carbon paper collector two sides, and it is mixed to form air/embedding lithium Mould assembly electrode, and make ORR reactivity material close to air side in battery assembly, embedding lithium type electrode material is close to diaphragm Side.

4. improving the method for lithium-air battery energy density and output power according to claim 3, it is characterised in that described The active material of ORR reaction is one of graphene, SP carbon, KB carbon, carbon nanotube and carbon fiber.

5. a kind of method for improving lithium-air battery energy density and output power, is characterized in that, applied with embedding lithium type electrode material It is overlying on aluminium foil or foamed nickel current collector surface, is used alone as high power anode；It is when assembled battery, high power anode and lithium is empty The air cathode of battery is respectively placed in battery cathode two sides, forms the lithium-air battery structure of a cathode, two anodes.

6. air/embedding lithium mixed type electrode with the production of claim 1 the method is the lithium-air battery of anode, feature exists In battery is made of air/embedding lithium mixed type anode, cathode, diaphragm, electrolyte assembling, and cell internal environment is pure oxygen compression ring Border, or include the inert gas environment of oxygen, or anode is in the environment containing oxygen；When the air/embedding Lithium mixed type anode is respectively coated using ORR reactivity material and embedding lithium type electrode material in nickel foam or carbon paper collector two When the method production of side, in the battery of assembling, the material side of reactivity containing ORR contains embedding lithium type electrode material side towards air Towards diaphragm.

7. lithium-air battery according to claim 6, it is characterised in that the cathode is lithium metal or embedding lithium type electrode material The alloying material of material or lithium.

8. lithium-air battery according to claim 6, it is characterised in that the electrolyte is 1mol L^-1LiTFSI-DME、 1mol L^-1LiTFSI-TEGDME、1mol L^-1One of LiTFSI-DMSO.

9. lithium-air battery according to claim 6, it is characterised in that the diaphragm is fibreglass diaphragm or lithium-ion electric The polymer separators that pond uses.