Device and method for doping nitrogen atoms on surface carbon layer of lithium manganese iron phosphate positive electrode material

Abstract

The invention discloses a device and a method for doping nitrogen atoms on a surface carbon layer of a lithium manganese iron phosphate positive electrode material. The device comprises a base, a motor base is arranged on the base, a motor is arranged on the motor base, a closed generating device and a built-in automatic rotating quartz glass cavity are supported on the base, an air inlet pipe is arranged on one side of the closed generating device, an exhaust pipe is arranged on one side of the bottom of the closed generating device, an exhaust valve is arranged on the exhaust pipe, and a vacuum pump is connected to the exhaust valve. A feeding pipe is arranged on the right side of the closed generating device, an output shaft of the motor is connected with a built-in automatic rotating quartz glass cavity through a connecting device, and the stirring device is rotationally arranged in a shell of the closed generating device. The surface carbon layer of the lithium manganese iron phosphate positive electrode material powder is doped with nitrogen atoms, and the aluminum foil is coated with the lithium manganese iron phosphate positive electrode material powder by using a coating method, so that the electronic conductivity of the lithium manganese iron phosphate positive electrode material pole piece is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and more particularly, to an apparatus and method for doping nitrogen atoms in a carbon layer on the surface of a lithium iron manganese phosphate cathode material. Background Art

[0002] In recent years, industries such as mobile consumer electronics and electric vehicles have developed rapidly, and there is an urgent need to develop new energy batteries with high energy density and high safety and stability to improve the long-range and long-term stable operation capabilities of these devices. Therefore, lithium-ion batteries are generally considered to be one of the most promising candidate batteries for large-scale energy storage applications. However, due to the bottleneck of low electronic conductivity in currently known cathode materials, the fast charging performance of lithium-ion batteries is relatively low. High-performance cathode materials can improve the energy density, cycle life, and rate performance of lithium-ion batteries. Therefore, it is particularly important to develop high-performance cathode materials.

[0003] Various types of cathode materials, including polyanion-based and layered materials, have been widely used as cathode materials for lithium-ion batteries. As a key component of lithium-ion batteries. Among them, polyanion-based cathode materials have become a research hotspot due to their good air stability, but their low electronic conductivity has become a limiting factor. The current strategy is to coat a carbon layer on the surface to improve the electronic conductivity, but an overly thick carbon layer affects the lithium-ion transport performance. Therefore, how to improve the electronic conductivity without increasing the carbon layer thickness has become the key to solving the problem. Lithium iron manganese phosphate has a theoretical specific capacity of 170 mAh / g and a higher voltage platform (4.1 V vs. Li / Li + ) and its crystal structure type is orthorhombic olivine structure. Therefore, lithium iron manganese phosphate also has good cycleability and stability. However, the electronic conductivity of lithium iron manganese phosphate is low, less than 10 -10 S / cm, resulting in poor fast charging performance.

[0004] To improve the electronic conductivity of the lithium iron manganese phosphate cathode material, doping nitrogen elements on the surface of its carbon layer has become the main method to improve its conductivity. Researchers have proposed many solutions to this, usually including: chemical nitrogen doping and high-temperature nitrogen doping. However, chemical nitrogen doping may cause the dissolution of manganese ions and iron ions due to the reaction in solution, thus affecting the structural stability of the material, and may also introduce new impurities. High-temperature nitrogen doping requires several hours of heating and cooling, which is very time-consuming. On the other hand, high temperature also brings the risk of lithium volatilization.

[0005] In addition, the reaction cavity of the existing low-temperature plasma reaction device has a relatively single function. To achieve better treatment effects, manual material turning is usually required, which is time-consuming and laborious. Therefore, there is an urgent need for a simple, feasible, and fast generating device and method to perform nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials, thereby paving the way for the development of high-energy-density lithium-ion batteries. Summary of the Invention

[0006] The present invention provides a generating device and method for rapidly performing nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials by glow discharge plasma, which solves the problems in the prior art that when performing nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials, the plasma generating device is difficult to automatically turn materials, manual material turning is time-consuming, laborious, and uneven, the processing capacity is small, and the processing method is complex.

[0007] The method of the present invention uses glow discharge plasma to rapidly perform nitrogen atom doping treatment on the surface carbon layer of lithium iron phosphate manganese cathode materials, improves the electronic conductivity of the electrodes of lithium iron phosphate manganese cathode materials, reduces the interfacial impedance of lithium iron phosphate manganese cathode materials, and enhances the fast charging performance of lithium metal ion batteries.

[0008] To achieve the above invention purpose, the technical solution of the present invention is as follows: A generating device for rapidly performing nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials by glow discharge plasma, characterized in that: it includes a base, a motor base is arranged on one side of the base, a motor is arranged on the motor base, a closed generating cavity is supported on the other side of the base, an air inlet pipe is arranged on one side of the closed generating cavity, an inlet / outlet material pipe is arranged on the right side of the closed generating cavity, an exhaust valve is arranged under the inlet / outlet material pipe, a vacuum pump is connected to the right side of the exhaust valve, a glow plasma excitation electrode is arranged inside the closed generating cavity, a rotatable quartz glass cavity is arranged below the excitation electrode, and the output shaft of the motor is connected to the quartz glass cavity.

[0009] A further technical solution is the generating device for rapidly performing nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials by glow discharge plasma, characterized in that: the closed generating cavity includes a horizontally placed excitation electrode arranged in parallel, and the rotating glass cavity is horizontally placed.

[0010] A further technical solution is the generating device for rapidly performing nitrogen atom doping on the surface carbon layer of lithium iron phosphate manganese cathode materials by glow discharge plasma, characterized in that: the excitation electrode and the rotating glass cavity are both horizontally placed along the radial direction.

[0011] A further technical solution is an apparatus for rapidly doping nitrogen atoms into the surface carbon layer of a lithium iron manganese phosphate cathode material by glow discharge plasma, characterized in that: the closed reaction chamber is made of stainless steel, the excitation electrode is made of metal titanium, and the rotating quartz glass chamber is made of quartz stone.

[0012] A further technical solution is that the method for doping nitrogen atoms into the surface carbon layer of the lithium iron manganese phosphate cathode material by the said apparatus comprises the following steps:

[0013] S1. Add the lithium iron manganese phosphate cathode material powder into the rotatable quartz glass chamber through the feed port pipe, evacuate it with a vacuum pump, and introduce high-purity nitrogen into the shell to remove the air in the chamber;

[0014] S2. Turn on the motor to adjust the rotation speed, and the rotation speed range of the electrode is 20 r / min to 200 r / min; after the pressure in the plasma chamber is stable, turn on the high-voltage DC power supply to adjust the voltage and current to stably generate a plasma atmosphere, the voltage range is 30 V to 300 V, and the current is 0.5 A to 2 A, and perform nitrogen atom doping on the surface carbon layer of the lithium iron manganese phosphate cathode material in this atmosphere, and obtain the lithium iron manganese phosphate cathode material with nitrogen atom doped on the surface carbon layer at the discharge pipe;

[0015] S3. Coat it on the aluminum foil by the coating method to obtain the required lithium iron manganese phosphate cathode material electrode with nitrogen atom doped on the surface carbon layer.

[0016] A further technical solution is that the said lithium iron manganese phosphate cathode material electrode is applied to a lithium metal ion battery.

[0017] A further technical solution is that the rotatable quartz glass chamber is made of quartz stone with a thickness of 3 - 6 mm.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] 1. By using glow discharge plasma modification treatment on the lithium iron manganese phosphate cathode powder, nitrogen element doping can be carried out on the surface carbon layer, and it is coated into a positive electrode sheet, so that the electronic conductivity of the said lithium iron manganese phosphate positive electrode sheet is improved, the interfacial impedance is reduced, the polarization of the battery is reduced, and the cycle life of the lithium iron manganese phosphate battery using the above can be extended, and the performance is excellent; it can also make the finally obtained activated lithium iron manganese phosphate positive electrode sheet have better electrochemical performance.

[0020] 2. Automatically turning the quartz glass cavity by a motor drives the materials to be more uniform, making the nitrogen element doping of the lithium iron manganese phosphate cathode more uniform. The process flow is simple, reducing energy consumption and equipment investment. Any process link of the present invention basically does not generate "three wastes", which conforms to the concept of green industry and is environmentally friendly.

[0021] 3. The modified lithium iron manganese phosphate cathode has high electronic conductivity and increased ionic conductivity. The agglomeration phenomenon of the lithium iron manganese phosphate cathode powder is improved. When applied to a lithium metal battery, it can reduce the interfacial impedance, reduce the battery polarization, extend the battery cycle life, and improve the battery electrochemical performance. Brief Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, where:

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] Figure 2 It is an X-ray diffraction pattern (XPS) of the glow discharge plasma unmodified lithium iron manganese phosphate cathode powder obtained in Embodiment 7 of the present invention.

[0025] Figure 3 It is an X-ray diffraction pattern (XPS) of the glow discharge plasma modified lithium iron manganese phosphate cathode powder obtained in Embodiment 7 of the present invention.

[0026] Figure 4 It is an electrochemical impedance spectroscopy (EIS) of the lithium iron manganese phosphate cathode sheet prepared from the glow discharge plasma modified and unmodified lithium iron manganese phosphate cathode powders obtained in Embodiment 7 of the present invention.

[0027] Figure 5 It is a voltage-capacity diagram of the lithium iron manganese phosphate cathode sheet prepared from the glow discharge plasma modified and unmodified lithium iron manganese phosphate cathode powders obtained in Embodiment 7 of the present invention.

[0028] Figure 6 It is an electronic conductivity diagram of the glow discharge plasma modified and unmodified lithium iron manganese phosphate cathode powders obtained in Embodiment 7 of the present invention.

[0029] Description of the Reference Numerals:

[0030] 1 - Base, 2 - Motor base, 3 - Motor, 4 - Output shaft, 5 - Inlet pipe, 6 - Inlet pipe, 7 - Excitation electrode, 8 - Closed generating cavity, 9 - Inlet / outlet pipe, 10 - Inlet / outlet pipe, 11 - Vacuum pump. Detailed implementation mode

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further details the invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Embodiment 1

[0033] A generating device for rapidly doping nitrogen atoms into the surface carbon layer of lithium iron phosphate manganese cathode material by glow discharge plasma, characterized in that: it includes a base (1), a motor base (2) is arranged on one side of the base (1), a motor (3) is arranged on the motor base (2), a closed generating cavity (8) is supported on the other side of the base (1), an inlet pipe (5) is arranged on one side of the closed generating cavity (8), an inlet / outlet pipe (9) is arranged on the right side of the closed generating cavity (8), an exhaust valve (10) is arranged under the inlet / outlet pipe (9), a vacuum pump (11) is connected to the right side of the exhaust valve (10), an excitation electrode (7) for glow plasma is arranged inside the closed generating cavity (8), and a rotatable quartz glass cavity (6) is arranged under the excitation electrode (7), and the output shaft (4) of the motor (3) is connected to the quartz glass cavity (6). The generating device for rapidly doping nitrogen atoms into the surface carbon layer of lithium iron phosphate manganese cathode material by glow discharge plasma is characterized in that: the closed generating cavity (8) includes a horizontally placed excitation electrode (7) arranged in parallel, and the rotating glass cavity (6) is horizontally placed. The generating device for rapidly doping nitrogen atoms into the surface carbon layer of lithium iron phosphate manganese cathode material by glow discharge plasma is characterized in that: the excitation electrode (7) and the rotating glass cavity (6) are both horizontally placed along the radial direction. The generating device for rapidly doping nitrogen atoms into the surface carbon layer of lithium iron phosphate manganese cathode material by glow discharge plasma is characterized in that: the closed generating cavity (8) is made of stainless steel, the excitation electrode (7) is made of metal titanium, and the rotating quartz glass cavity (6) is made of quartz.

[0034] Its usage steps are as follows:

[0035] S1. Add lithium iron phosphate manganese cathode material powder into the rotatable quartz glass cavity (6) through the inlet / outlet pipe (9), and use the vacuum pump (11) to evacuate, and introduce high-purity nitrogen into the shell to remove the air in the cavity;

[0036] S2. Turn on the motor (3) and adjust the rotation speed. The rotation speed range of the electrode is 20 r / min to 200 r / min. After the air pressure in the plasma cavity stabilizes, turn on the high-voltage DC power supply to adjust the voltage and current to stably generate a plasma atmosphere. The voltage range is 30 V to 300 V, and the current is 0.5 A to 2 A. Then, perform nitrogen atom doping on the surface carbon layer of the lithium iron phosphate manganese cathode material under this atmosphere, and obtain the lithium iron phosphate manganese cathode material with nitrogen atom-doped surface carbon layer at the discharge pipe (9).

[0037] S3. Coat it on the aluminum foil by the coating method to obtain the required lithium iron phosphate manganese cathode electrode with nitrogen atom-doped surface carbon layer.

[0038] Example 2

[0039] (1) Take 500 g of lithium iron phosphate manganese cathode powder with 200 meshes and put the above lithium iron phosphate manganese cathode powder into the rotatable quartz glass cavity (6) of the generating device through the feed pipe (9).

[0040] (2) Introduce high-purity nitrogen into the cavity, turn on the vacuum pump (11), and evacuate the air in the cavity. Turn on the motor and adjust the motor rotation speed to 50 r / min.

[0041] (3) After the air pressure in the plasma cavity stabilizes, turn on the high-voltage DC power supply. The working voltage is 100 V, and the working current is 2 A to stably generate a plasma atmosphere. Then, perform nitrogen atom doping on the surface carbon layer of the lithium iron phosphate manganese cathode material under this atmosphere, and obtain the lithium iron phosphate manganese cathode material with nitrogen atom-doped surface carbon layer at the discharge pipe (9).

[0042] (4) Prepare the lithium iron phosphate manganese cathode electrode sheet by the traditional coating method to obtain the required lithium iron phosphate manganese cathode electrode.

[0043] Example 3

[0044] (1) Take 500 g of lithium iron phosphate manganese cathode powder with 200 meshes and put the above lithium iron phosphate manganese cathode powder into the rotatable quartz glass cavity (6) of the generating device through the feed pipe (9).

[0045] (2) Introduce high-purity nitrogen into the cavity, turn on the vacuum pump (11), and evacuate the air in the cavity. Turn on the motor and adjust the motor rotation speed to 100 r / min.

[0046] (3) After the air pressure in the plasma cavity stabilizes, turn on the high-voltage DC power supply. The working voltage is 100 V, and the working current is 3 A to stably generate a plasma atmosphere. Then, perform nitrogen atom doping on the surface carbon layer of the lithium iron phosphate manganese cathode material under this atmosphere, and obtain the lithium iron phosphate manganese cathode material with nitrogen atom-doped surface carbon layer at the discharge pipe (9).

[0047] (4) Prepare the lithium iron manganese phosphate cathode electrode sheet by using the traditional coating method, that is, obtain the required lithium iron manganese phosphate cathode electrode.

[0048] Example 5

[0049] (1) Take 500 g of lithium iron manganese phosphate cathode powder with 200 mesh, and put the above lithium iron manganese phosphate cathode powder into the rotatable quartz glass cavity (6) of the generating device through the feed pipe (9).

[0050] (2) Introduce high-purity nitrogen into the cavity, and turn on the vacuum pump (11) to remove the air in the cavity; turn on the motor and adjust the motor speed to 150 r / min.

[0051] (3) After the pressure in the plasma cavity is stable, turn on the high-voltage DC power supply, with a working voltage of 200 V and a working current of 2 A, stably generate a plasma atmosphere, and perform nitrogen atom doping on the surface carbon layer of the lithium iron manganese phosphate cathode material in this atmosphere, and obtain the lithium iron manganese phosphate cathode material with nitrogen atom doping on the surface carbon layer at the discharge pipe (9).

[0052] (4) Prepare the lithium iron manganese phosphate cathode electrode sheet by using the traditional coating method, that is, obtain the required lithium iron manganese phosphate cathode electrode.

[0053] Example 6

[0054] (1) Take 500 g of lithium iron manganese phosphate cathode powder with 200 mesh, and put the above lithium iron manganese phosphate cathode powder into the rotatable quartz glass cavity (6) of the generating device through the feed pipe (9).

[0055] (2) Introduce high-purity nitrogen into the cavity, and turn on the vacuum pump (11) to remove the air in the cavity; turn on the motor and adjust the motor speed to 300 r / min.

[0056] (3) After the pressure in the plasma cavity is stable, turn on the high-voltage DC power supply, with a working voltage of 200 V and a working current of 2.5 A, stably generate a plasma atmosphere, and perform nitrogen atom doping on the surface carbon layer of the lithium iron manganese phosphate cathode material in this atmosphere, and obtain the lithium iron manganese phosphate cathode material with nitrogen atom doping on the surface carbon layer at the discharge pipe (9).

[0057] (4) Prepare the lithium iron manganese phosphate cathode electrode sheet by using the traditional coating method, that is, obtain the required lithium iron manganese phosphate cathode electrode.

[0058] Example 7

[0059] (1) Take 500 g of lithium iron manganese phosphate cathode powder with 200 mesh, and put the above lithium iron manganese phosphate cathode powder into the rotatable quartz glass cavity (6) of the generating device through the feed pipe (9).

[0060] (2) Introduce high-purity nitrogen gas into the cavity, and turn on the vacuum pump (11) to exhaust the air in the cavity; turn on the motor and adjust the motor speed to 50 r / min.

[0061] (3) After the air pressure in the plasma cavity is stabilized, turn on the high-voltage DC power supply. The working voltage is 300 V and the working current is 1 A to stably generate a plasma atmosphere. Under this atmosphere, nitrogen atom doping is carried out on the surface carbon layer of the lithium iron phosphate manganese cathode material, and the lithium iron phosphate manganese cathode material with nitrogen atom doping on the surface carbon layer is obtained at the discharge pipe (9).

[0062] (4) Prepare the lithium iron phosphate manganese cathode electrode sheet by the traditional coating method, that is, the required lithium iron phosphate manganese cathode electrode is obtained.

[0063] Physical and electrochemical tests are carried out on the cathode with nitrogen atom doping on the surface carbon layer of the lithium iron phosphate manganese cathode material by photodischarge plasma. From Figure 2 and Figure 3 it can be seen that after plasma treatment, the peak of N1s in the fine spectrum of N1s becomes significantly stronger before and after treatment, confirming that nitrogen element is successfully doped into the surface carbon layer of lithium iron phosphate manganese by plasma treatment. By comparing Figure 4 the impedance, it can be obtained that compared with the untreated one, its impedance is significantly reduced after photodischarge plasma modification, and the total impedance is reduced from 123 Ω to about 50 Ω. From Figure 5 it can be seen that compared with the untreated one, the polarization level of the modified battery is significantly reduced. From Figure 6 it can be obtained that compared with the untreated one, for the lithium iron phosphate manganese cathode material, its electronic conductivity is significantly reduced, which is consistent with the result of the electrochemical impedance.

[0064] Although the present invention has been described herein with reference to several illustrative embodiments of the present invention, it should be understood that those skilled in the art can design many other modifications and embodiments that will fall within the scope of the disclosure of this application. More specifically, within the scope of the disclosure, drawings and claims of this application, various deformations and improvements can be made to the component parts or layouts. In addition to the deformations and improvements to the component parts or layouts, other uses will also be obvious to those skilled in the art.

Claims

1. A glow discharge plasma generating device for nitrogen atom doping of the surface carbon layer of lithium manganese iron phosphate positive electrode material, characterized in that: The invention comprises a base (1), wherein a motor base (2) is arranged on one side of the base (1), a motor (3) is arranged on the motor base (2), a closed generating chamber (8) is supported on the other side of the base (1), an air inlet pipe (5) is arranged on one side of the closed generating chamber (8), an inlet / outlet material pipe (9) is arranged on the right side of the closed generating chamber (8), an exhaust valve (10) is arranged below the inlet / outlet material pipe (9), a vacuum pump (11) is connected to the right side of the exhaust valve (10), a glow plasma excitation electrode (7) is arranged inside the closed generating chamber (8), a rotatable quartz glass chamber (6) is arranged below the excitation electrode (7), and an output shaft (4) of the motor (3) is connected to the quartz glass chamber (6).

2. A glow discharge plasma generating device for nitrogen atom doping of the surface carbon layer of lithium manganese iron phosphate positive electrode material according to claim 1, characterized in that: The closed generating cavity (8) comprises a parallel and horizontally placed excitation electrode (7), and the rotating glass cavity (6) is placed horizontally.

3. A glow discharge plasma generating device for nitrogen atom doping of the surface carbon layer of lithium manganese iron phosphate positive electrode material as claimed in claim 2, characterized in that: The exciting electrodes (7) and the rotating glass cavity (6) are both placed horizontally along the radial direction.

4. A glow discharge plasma generating device for nitrogen atom doping of the surface carbon layer of lithium manganese iron phosphate positive electrode material according to claim 1, characterized in that: The closed generating cavity (8) is made of stainless steel, the exciting electrode (7) is made of metal titanium, and the rotating quartz glass cavity (6) is made of quartz stone.

5. A method for nitrogen atom doping of the surface carbon layer of lithium manganese iron phosphate positive electrode material by glow discharge plasma, characterized in that: The following steps are involved: S1, adding lithium manganese iron phosphate positive electrode material powder into a rotatable quartz glass cavity (6) through a feed inlet pipe (9), and evacuating the cavity with a vacuum pump (11), introducing high-purity nitrogen into the shell, and removing the air in the cavity; S2, turning on the motor (3) to adjust the speed, the electrode speed range is 20r / min to 200r / min, after the gas pressure in the plasma chamber is stable, turning on the high-voltage DC power supply to adjust the voltage and current to stably generate a plasma atmosphere, the voltage range is 30V to 300V, the current is 0.5A to 2A, and in this atmosphere, the surface carbon layer of the lithium manganese iron phosphate positive electrode material is doped with nitrogen atoms, and the surface carbon layer of the lithium manganese iron phosphate positive electrode material with nitrogen atoms doped is obtained in the discharge pipe (9); S3, coating it on aluminum foil by a coating method, that is, obtaining the required surface carbon layer for nitrogen atom-doped lithium manganese iron phosphate positive electrode material electrode.

6. The method for nitrogen atom doping of the surface carbon layer of lithium iron manganese phosphate positive electrode material by glow discharge plasma according to claim 5, characterized in that: The lithium iron manganese phosphate positive electrode material electrode is applied to lithium metal ion batteries.

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