CN111484247A - Glass positive electrode material and preparation method and application thereof - Google Patents

Abstract

The invention provides a glass anode material and a preparation method and application thereof, wherein the glass anode material comprises glass powder and a binder in a mass ratio of 6-10: 1; the glass powder comprises V with the mass ratio of 10-20: 0.5-5: 0.1-4₂O₅、Li₃PO₄And CaC₂. The invention adopts CaC₂As strong reducing agent and conductive agent, L i₃PO₄And a lithium source and a phosphorus source are introduced, so that the glass cathode material has better conductivity. In addition, the assembled lithium ion battery has high reversible specific capacity and strong battery cycling stability. Results of the experimentShows that: the positive electrode V4+/V is 58-62%; the first discharge capacity of the battery is 285-292 mAh/g (0.1C); the discharge capacity after 100 cycles at 0.1 ℃ is 274-281 mAh/g (0.1C); the circulation efficiency is more than 95%.

Description

A kind of glass cathode material, preparation method and application thereof

technical field

The invention belongs to the technical field of battery positive electrode materials, and in particular relates to a glass positive electrode material and a preparation method and application thereof.

Background technique

Energy and environment are the material basis for human survival, and they are also the two major problems facing the current era. The core of energy research is to develop new energy materials to improve energy efficiency and energy storage capacity. As a clean energy source, lithium-ion batteries are widely used in cutting-edge technology fields such as artificial intelligence, electric vehicles, and drones. However, the current energy density, stability and rate performance of lithium-ion batteries are far from meeting the needs of rapid technological development. Problems such as the explosion of mobile phone batteries, the safety hazards of new energy vehicles, and the short battery life of drones plague the further promotion and application of new technologies. The cathode material is the core part of the lithium-ion battery. The ideal cathode material should have the characteristics of high energy density, good charge-discharge cycle performance, safety and stability, low cost, and environmental friendliness.

Due to the advantages of large specific capacity, wide use potential, and high energy density, lithium-ion batteries (LIBs) have developed extremely rapidly, and products have been put into large-scale use in daily life. The cathode materials of lithium-ion batteries are mainly cobalt, manganese, nickel, etc. and their composite oxides. Commercial applications have demonstrated high potential and stability of these materials, but low specific capacity (205 mAh/g). In addition, as the earliest commercial cathode material, the theoretical specific capacity of lithium cobalt oxide (LiCoO ₂ ) is 273mAh/g, but the actual specific capacity is only about 140mAh/g, and it also has the defects of high price and high toxicity; although lithium nickelate The specific capacity of (LiNiO ₂ ) can reach 150mAh/g, which is slightly higher than that of LiCoO ₂ . However, during the synthesis of LiNiO ₂ , the lack of lithium is prone to occur, and it is difficult to synthesize LiNiO ₂ that meets the standard chemical composition; it is similar to LiCoO ₂ . Compared with lithium manganate (LiMnO ₄ ), the price is low, but the theoretical specific capacity is low (148mAh/g), and the cycle performance is poor; the theoretical specific capacity of lithium iron phosphate (LiFeO ₄ ) can reach 170mAh/g, but the electrical conductivity Poor, low energy density. The theoretical specific capacity of the negative electrode graphite is 372mAh/g, and the actual specific capacity is 360mAh/g. The positive electrode material limits the specific capacity of lithium-ion batteries. At present, these factors restrict the improvement of the performance of lithium-ion batteries, and it is urgent to research and develop new high-performance cathode materials to meet the application of energy storage devices.

Among cathode materials, _V2O5 is a _promising material due to its high capacity, stable crystal structure, and low cost. However, low electronic conductivity, small Li-ion diffusion coefficient, poor rate capability and cycling stability hinder the practical application of _V2O5 in _LIBs .

The V ₂ O ₅ crystal material has some defects that are not conducive to electrochemical performance due to its own properties, such as the slow diffusion of lithium ions in the crystal material, resulting in a low rate performance of the electrode material. The main means to improve the defect is the bulk structure. Transformation, C doping, mixing of other systems, valence bond transformation, crystal state transformation, etc.

V ₂ O ₅ -P ₂ O ₅ , V ₂ O ₅ -Li ₂ OP ₂ O ₅ are used as vanadium phosphorous glass as cathode materials for lithium ion batteries, but have poor electrical conductivity, and a conductive agent is required to prepare the slurry, and the reversible specific capacity and rate performance Difference. At the same time, the reducing atmosphere hydrogen has poor ability to reduce V5+, and the adjustable V4+/V ratio range is small. When quenched in air, the partially reduced V4+ will be oxidized to V5+, which affects the electrochemical performance of lithium-ion batteries.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a glass positive electrode material, a preparation method and application thereof, and the glass positive electrode material has high conductivity.

The invention provides a glass positive electrode material, comprising glass powder and a binder in a mass ratio of 6-10:1;

The glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 10-20:0.5-5:0.1-4.

Preferably, the glass powder comprises V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:3.474:0.8;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:2.235:1.6;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 18.23:3.474:2.4;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:3.474:3.2;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 16.87:3.474:4.0.

The present invention provides a method for preparing the glass positive electrode material according to the above technical solution, comprising the following steps:

Mix CaC ₂ , V ₂ O ₅ and Li ₃ PO ₄ , under the protection of argon, heat up to 700-800°C, hold for 10-30min; continue to heat up to 900-1400°C, hold for 10-30min, quench, cool down, Grinding to obtain glass powder;

The glass powder and the binder with a mass ratio of 6-10:1 are mixed, dropped into a solvent for ball milling, coated on aluminum foil, and dried to obtain a glass positive electrode material.

Preferably, the temperature is raised to 700-800°C at 5-15°C/min.

Preferably, the temperature is raised to 900-1400°C at 5-15°C/min.

The present invention provides a lithium ion battery, comprising the glass positive electrode material described in the above technical solution.

The invention provides a glass positive electrode material, comprising glass powder and a binder in a mass ratio of 6-10:1; the glass powder includes V ₂ O in a mass ratio of 10-20:0.5-5:0.1-4 _5. Li ₃ PO ₄ and CaC ₂ . In the present invention, CaC ₂ is used as a strong reducing agent and a conductive agent, and Li ₃ PO ₄ is introduced into a lithium source and a phosphorus source, so that the glass positive electrode material has better conductivity. In addition, the assembled lithium-ion battery has high reversible specific capacity and strong battery cycle stability. The experimental results show that the positive electrode V4+/V is 58-62%; the first discharge capacity of the battery is 285-292mAh/g (0.1C); the discharge capacity after 100 cycles at 0.1C is 274-281mAh/g (0.1C); The efficiency is above 95%.

Description of drawings

Fig. 1 is the XRD spectrum of the glass powder prepared in Example 1 of the present invention;

Fig. 2 is the IR image of the glass powder prepared in Example 1 of the present invention;

3 is an XPS (V2p) diagram of the glass powder prepared in Example 1 of the present invention;

4 is a DTA diagram of the glass powder prepared in Example 1 of the present invention.

Detailed ways

The invention provides a glass positive electrode material, comprising glass powder and a binder in a mass ratio of 6-10:1;

The glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 10-20:0.5-5:0.1-4.

The glass positive electrode material provided by the present invention includes glass powder, and the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 10-20:0.5-5:0.1-4. In the present invention, the CaC ₂ is used as a strong reducing agent and a conductive agent, and Li ₃ PO ₄ is introduced into a lithium source and a phosphorus source, so that the glass material as a positive electrode material has higher conductivity. It also has high reversible specific capacity and strong battery cycle stability.

In a specific embodiment of the present invention, the glass powder preferably includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:3.474:0.8;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:2.235:1.6;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 18.23:3.474:2.4;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 12.74:3.474:3.2;

Or the glass powder includes V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ in a mass ratio of 16.87:3.474:4.0.

In the present invention, the mass ratio of the glass powder and the binder is 6-10:1, preferably 7-9:1; in a specific embodiment, the mass ratio of the glass powder and the binder is 8:1 . The binder is preferably selected from polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

The present invention provides a method for preparing the glass positive electrode material according to the above technical solution, comprising the following steps:

Mix CaC ₂ , V ₂ O ₅ and Li ₃ PO ₄ , under the protection of argon, heat up to 700-800°C, hold for 10-30min; continue to heat up to 900-1400°C, hold for 10-30min, quench, cool down, Grinding to obtain glass powder;

The glass powder and the binder with a mass ratio of 6-10:1 are mixed, dropped into a solvent for ball milling, coated on aluminum foil, and dried to obtain a glass positive electrode material.

The method provided by the invention has simple process and low cost.

In the present invention, the temperature is preferably raised to 700 to 800°C at 5°C/min; more preferably, the temperature is raised to 700°C to 800°C at 5°C/min. In the present invention, the temperature is preferably raised to 900-1400°C at 5-15°C/min; more preferably, the temperature is raised to 900-1400°C at 15°C/min. In a specific embodiment, the present invention is heated to 700° C. at 5° C./min, and kept for 30 minutes;

The present invention provides a lithium ion battery, comprising the glass positive electrode material described in the above technical solution.

In the present invention, no additional conductive agent is added, the glass powder is directly mixed with the binder, the solvent is added dropwise, and the slurry is ball _- milled. / Dimethyl carbonate (volume ratio 1:1) electrolyte, Celgard 2025 as the separator, lithium sheet as the counter electrode, and assembled into a CR2032 coin cell in a glove box. The charge-discharge performance of the comparative lithium-ion battery at different current densities in the voltage range of 2.0-4.2V was tested on an electrochemical workstation. The solvent is N-methylpyrrolidone.

In order to further illustrate the present invention, a glass positive electrode material provided by the present invention and its preparation method and application are described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present invention.

Comparative Example 1

The dried V ₂ O ₅ powder and P ₂ O ₅ powder were mixed in a stoichiometric ratio and melted in a hydrogen atmosphere to prepare a 80V ₂ O ₅ ·20P ₂ O ₅ glass sample. The mixture was placed in a quartz crucible after stirring and homogeneous mixing. Glass melting was carried out using a tube furnace. Heating at 800°C for 5 minutes gave a vanadium phosphorous glass sample melt. The molten glass was poured onto an iron plate and subsequently annealed in a muffle furnace at 250°C for 2 hours and then cooled with the furnace. Grind the preformed glass into powder with an agate mortar. The electrode is made of active material (vanadium phosphorus glass), carbon black and polytetrafluoroethylene (PTFE) binder mixed in a mass ratio of 8:1.5:0.5. The weighed vanadium phosphorus glass powder and carbon black were put into an agate mortar and ground for 30 minutes to obtain a homogeneous mixture. Then, polytetrafluoroethylene was added to the prepared mixture and vigorously mixed to obtain a uniform film. The prepared cathode film was punched into a circular sheet with a circular cutter with a diameter of 8 mm, and then uniformly pasted on an aluminum mesh. Then, use CR2032 coin cell (316L stainless steel, polypropylene gasket) as cathode, 1mol/L LiPF ₆ as ethylene carbonate/dimethyl carbonate (volume ratio 1:1) electrolyte, Celgard 2025 as separator, lithium sheet For the counter electrode, a CR2032 type coin cell was assembled in a glove box. The charge-discharge performance of the comparative lithium-ion battery at different current densities in the voltage range of 2.0-4.2V was tested on an electrochemical workstation. The test data showed a specific capacity of 270mAh g ^-1 for the first time, and a capacity retention rate of about 90% after 100 cycles. Furthermore, after 300 cycles, a specific capacity of 220mAh g- ¹ can be provided at a high current density of 85mAg ^-1 , which is equivalent to 80% capacity retention.

Example 1

12.74g V ₂ O ₅ , 3.474 g Li ₃ PO ₄ , and 0.8 g CaC ₂ were mixed, stirred and ground evenly, and the obtained mixed raw materials were transferred to an alumina crucible. Melt in a tubular heating furnace under argon protection, heat up to 700°C at a heating rate of 5°C/min, and hold for 30 minutes; raise the temperature to 1000°C at a heating rate of 15°C/min, and hold for 30 minutes; under argon protection It was quenched at room temperature and ground to obtain glass powder.

Mix the glass powder and the binder polytetrafluoroethylene in a ratio of 8:1, and then drop an appropriate amount of solvent N-methylpyrrolidone for ball milling. The obtained slurry is coated on aluminum foil and dried, and then the aluminum foil is used as the positive electrode, 1mol/L LiPF ₆ is ethylene carbonate/dimethyl carbonate (volume ratio 1:1) electrolyte, Celgard 2025 is used as separator, lithium sheet is used as counter electrode, and a CR2032 coin cell is assembled in a glove box. The charge-discharge performance of the comparative lithium-ion battery at different current densities in the voltage range of 2.0-4.2V was tested on an electrochemical workstation.

Examples 2 to 5

According to the technological process of embodiment 1, the difference is that the raw material consumption is different, see Table 2.

Table 1 Raw materials used in the preparation of glass positive electrode materials in Examples 1 to 5

The performance test results of the present invention to the lithium ion batteries assembled with the glass materials prepared in Examples 1 to 5 are shown in Table 2:

Table 2 Performance test results of batteries assembled with glass positive electrodes prepared in Examples 1 to 5 of the present invention

It can be seen from the above embodiments that the present invention provides a glass positive electrode material, comprising glass powder and a binder in a mass ratio of 6-10:1; the glass powder includes a mass ratio of 10-20:0.5-5:0.1 ~4 of V ₂ O ₅ , Li ₃ PO ₄ and CaC ₂ . In the present invention, CaC ₂ is used as a strong reducing agent and a conductive agent, and Li ₃ PO ₄ is introduced into a lithium source and a phosphorus source, so that the glass positive electrode material has better conductivity. In addition, the assembled lithium-ion battery has high reversible specific capacity and strong battery cycle stability. The experimental results show that the positive electrode V4+/V is 58-62%; the initial discharge capacity of the battery is 285-292mAh/g (0.1C); the discharge capacity after 100 cycles at 0.1C is 274-281mAh/g (0.1C); The efficiency is above 95%.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (6)

1. The glass cathode material comprises glass powder and a binder in a mass ratio of 6-10: 1;

the glass powder comprises V with the mass ratio of 10-20: 0.5-5: 0.1-4₂O₅、Li₃PO₄And CaC₂。

2. The glass positive electrode material according to claim 1, wherein the glass isThe powder comprises 12.74 mass ratio: 3.474: v of 0.8₂O₅、Li₃PO₄And CaC₂；

Or the glass powder comprises 12.74: 2.235: v of 1.6₂O₅、Li₃PO₄And CaC₂；

Or the glass powder comprises the following components in a mass ratio of 18.23: 3.474: v of 2.4₂O₅、Li₃PO₄And CaC₂；

Or the glass powder comprises the following components in a mass ratio of 12.74: 3.474: v of 3.2₂O₅、Li₃PO₄And CaC₂；

Or the glass powder comprises the following components in a mass ratio of 16.87: 3.474: v of 4.0₂O₅、Li₃PO₄And CaC₂。

3. A method for producing a glass positive electrode material according to any one of claims 1 to 2, comprising the steps of:

mixing CaC₂、V₂O₅And L i₃PO₄Mixing, heating to 700-800 ℃ under the protection of argon, and keeping the temperature for 10-30 min; continuing to heat to 900-1400 ℃, preserving heat for 10-30 min, quenching, cooling and grinding to obtain glass powder;

mixing the following components in a mass ratio of 6-10: 1, mixing the glass powder and the binder, dripping a solvent, ball-milling, coating on an aluminum foil, and drying to obtain the glass cathode material.

4. The method according to claim 3, wherein the temperature is raised to 700-800 ℃ at a rate of 5-15 ℃/min.

5. The method according to claim 3, wherein the temperature is raised to 900 to 1400 ℃ at a rate of 5 to 15 ℃/min.

6. A lithium ion battery comprising the glass positive electrode material according to any one of claims 1 to 5.

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