CN103078082B - A high-capacity V2O5 thin-film cathode material for lithium-ion batteries - Google Patents

Abstract

A high-capacity V ₂ O ₅ thin film positive electrode material for lithium-ion batteries, which is prepared by the following methods: (1) Preparation of V ₂ O ₅ sol: using powder V ₂ O ₅ as raw material, stirring with H ₂ O ₂ Prepare V ₂ O ₅ sols by mixing; (2) Prepare sols with different concentrations: prepare the above-mentioned V ₂ O ₅ sols into sols with concentrations ranging from 0.002mol/L to 0.016mol/L; (3) Pretreat the Pt substrate : Submerge the Pt sheet in hydrogen peroxide for 10 minutes, then rinse it with deionized water and air dry; (4) Preparation of V ₂ O ₅ thin film electrode: Use a pipette to take 10 μL of V ₂ O ₅ sol at the desired concentration , spread on a Pt sheet, air-dried naturally, placed in a muffle furnace at 500°C for 2h, and cooled naturally to room temperature to obtain a V ₂ O ₅ thin film electrode. The V ₂ O ₅ thin film material of the invention has a special microscopic appearance and can increase the specific capacity of the lithium ion battery.

Description

A high-capacity V2O5 thin-film cathode material for lithium-ion batteries

technical field

The invention belongs to the field of electrode materials, in particular to a high-capacity V ₂ O ₅ thin film cathode material for lithium ion batteries.

Background technique

Lithium-ion battery is a new battery developed on the basis of lithium battery in the last century. It has the advantages of high voltage, large specific energy, and long cycle life. It has been widely used in various daily small portable power supplies. It may be applied in the field of high-power electrical appliances in the future. In recent years, with the emergence of high-performance anode systems, the research on electrolytes has also made great progress. Relatively speaking, the research on cathode materials for lithium-ion batteries lags behind, which limits the further improvement of the overall performance of lithium-ion batteries. At present, the positive electrode materials that have been studied more mainly include layered structure LiMO ₂ (where: M=Ni, Co, Mn, etc.), including the mixture of multiple systems, but the problems of low specific capacity and cyclability have yet to be resolved. Spinel-type LiMn ₂ O ₄ has the advantages of good safety performance and easy synthesis. It is also a cathode material for lithium-ion batteries that has been studied more at present. However, there is a John-Teller effect in the process of charging and discharging, and the structure is distorted, which reduces the spinel. The symmetry of the structure leads to poor cycle performance. LiMPO ₄ with an olivine crystal structure (where: M=Fe, Mn, Ni, Co, etc.) has the advantages of good thermal stability and high safety performance, and its stability in the charged state exceeds that of transition metal oxides with a layered structure. It is especially suitable for power battery materials, but there is an irreversible capacity problem caused by low conductivity. On the one hand, the improvement method is: by changing the synthesis method to prepare powder materials with fine particles and high purity; on the other hand By doping metal powder or metal ions to improve its conductivity and increase the reversible capacity.

In triclinic V ₂ O ₅ , VO ₄ tetragonal pyramid units are combined into chains through oxygen bridges, and the chains are connected through another oxygen bridge to form a complex chain, thus forming a chain parallel to the [001] plane. The layered arrangement is very suitable for the deintercalation of lithium ions, but in practical applications, there are still problems such as low ion transmission rate, low conductivity, poor charge-discharge cycle performance, low specific capacity and energy density, which limit its application in lithium-ion batteries. field applications.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art, solve the problem of small capacity of lithium-ion batteries and serious attenuation of specific capacity, and provide a high-capacity V ₂ O ₅ thin film positive electrode material for lithium-ion batteries.

The present invention relates to a high-capacity V ₂ O ₅ thin-film cathode material for lithium-ion batteries, which is characterized in that the material is prepared by the following method: (1) Preparation of vanadium pentoxide sol: take 3mL of 30% hydrogen peroxide (H ₂ O ₂ ) solution was placed in a 25 mL beaker, and then accurately weighed 0.146 g of vanadium pentoxide (V ₂ O ₅ ) powder was put into the beaker, and stirred slowly at room temperature to make V ₂ O ₅ Dissolve the powder completely, then add 2 mL of deionized water and continue to stir until a stable reddish-brown sol is formed; (2) Prepare sols with different concentrations: Dilute the above V ₂ O ₅ sols to 50mL-400ml respectively to obtain a concentration range of: 0.002 mol/L to 0.016 mol/L V ₂ O ₅ sol; (3) Pretreatment of Pt substrate: completely immerse the Pt sheet to be treated in hydrogen peroxide for 10 minutes, then rinse with deionized water, and air dry ; (4) Preparation of V ₂ O ₅ thin film electrode: Measure 10 μL of V ₂ O ₅ sol with the desired concentration with a pipette, spread it on the pretreated Pt sheet, air-dry it naturally at room temperature, and place it in a 500°C Calcined in a muffle furnace for 2 hours, and cooled naturally to room temperature to obtain a V ₂ O ₅ thin film electrode.

The V ₂ O ₅ electrode material prepared by this method has a special morphology, has two stable charging and discharging platforms, exhibits high lithium intercalation capacity and good cycle performance, and has broad application prospects. In addition, the method does not involve the use of conductive agents and adhesives in the electrode manufacturing process, and the electrode material is directly spread on the electrode substrate in one step. The manufacturing process is simple, the operation is simple, the process is easy to control, and it is environmentally friendly.

The V ₂ O ₅ thin film electrode material prepared by the present invention adopts a three-electrode system, with 1 mol/L LiClO ₄ /PC as the electrolyte, the V ₂ O ₅ thin film electrode as the working electrode, the Pt sheet as the auxiliary electrode, and the Ag/AgCl As a reference electrode, the cyclic voltammetry and constant current charge and discharge tests show that this V ₂ O ₅ film has two obvious charge and discharge platforms, and the cycle performance is good. When the charge and discharge current density is 400mA/g, its initial The discharge specific capacity can reach 714mAh/g, while the V ₂ O ₅ positive electrode material for lithium-ion batteries reported in the existing literature has a discharge specific capacity of only ~377mAh/g. Therefore, it is different from the existing V ₂ O ₅ Compared with positive electrode materials, the V ₂ O ₅ thin film positive electrode material provided by the present invention can effectively solve the problem of low specific capacity of lithium ion batteries, and significantly improve the application value of V ₂ O ₅ as lithium ion battery positive electrode materials.

Description of drawings

Figure 1 is the SEM of the V ₂ O ₅ thin film cathode material with a sol concentration of 0.008mol/L;

Figure 2 is the cyclic voltammetry curve of the V ₂ O ₅ thin film cathode material with a sol concentration of 0.008mol/L at a scan rate of 0.01V/s;

Figure 3 is the constant current charge and discharge capacity curve of the V ₂ O ₅ thin film cathode material with a sol concentration of 0.008mol/L under the condition of a mass current density of 400mA/g;

Figure 4 is the charge and discharge curves of the V ₂ O ₅ thin film positive electrode material with a sol concentration of 0.008mol/L at different current densities;

Figure 5 is the discharge capacity decay curve of the V ₂ O ₅ thin film cathode material at different current densities with a sol concentration of 0.008mol/L;

Figure 6 is a comparison of the initial charge and discharge capacities of several V ₂ O ₅ thin film cathode materials with a sol concentration of 0.008mol/L;

Figure 7 is the galvanostatic charge and discharge capacity curve of the V ₂ O ₅ film with a sol concentration of 0.016mol/L under the condition of a mass current density of 400mA/g;

Figure 8 is the galvanostatic charge-discharge capacity curve of a V ₂ O ₅ film with a sol concentration of 0.0054mol/L under the condition of a mass current density of 400mA/g;

Figure 9 is the galvanostatic charge and discharge capacity curve of the V ₂ O ₅ thin film with a sol concentration of 0.004mol/L under the condition of a mass current density of 400mA/g;

Figure 10 is the galvanostatic charge and discharge capacity curve of the V ₂ O ₅ thin film with a sol concentration of 0.0032mol/L under the condition of a mass current density of 400mA/g;

Fig. 11 is the galvanostatic charge and discharge capacity curve of the V ₂ O ₅ thin film with a sol concentration of 0.002 mol/L under the condition of a mass current density of 400 mA/g.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention is further described as follows:

Example 1

A kind of preparation method of high-capacity V ₂ O ₅ thin film cathode material for lithium ion battery is as follows:

(1) Preparation of vanadium pentoxide sol: Take 3mL of 30% hydrogen peroxide (H ₂ O ₂ ) solution and place it in a 25 mL beaker, and then accurately weigh 0.146 g of vanadium pentoxide (V ₂ O ₅ ) powder Put it into a beaker, stir fully and slowly at room temperature to completely dissolve the V ₂ O ₅ powder, then add 2 mL of deionized water and continue stirring until a stable red-brown sol is formed;

(2) Prepare a V ₂ O ₅ sol with a concentration of 0.008 mol/L: Dilute the above V ₂ O ₅ sol to 100ml to obtain a V ₂ O ₅ sol with a concentration of 0.008 mol/L;

(3) Pretreatment of the Pt substrate: completely immerse the Pt sheet to be treated in hydrogen peroxide for 10 minutes, then rinse it with deionized water, and let it dry naturally;

(4) Preparation of V ₂ O ₅ thin film electrode: Use a pipette to measure 10 μL of V ₂ O ₅ sol at the desired concentration, spread it on the pretreated Pt sheet, air-dry it naturally at room temperature, and place it in a 500° C. Calcined in a Furnace for 2 hours, then cooled naturally to room temperature to obtain a V ₂ O ₅ thin film electrode.

A three-electrode system was used for the test, V ₂ O ₅ film electrode was used as the working electrode, Ag/AgCl was used as the reference electrode, and the pretreated Pt sheet was used as the counter electrode for cyclic voltammetry and constant current charge-discharge tests.

The scanning electron image (SEM) of the V ₂ O ₅ film electrode prepared in this example is shown in Figure 1. It can be seen from the figure that the V ₂ O ₅ film is composed of particles with a sheet-like structure and has a uniform and good compactness.

The cyclic voltammetry curve of the V ₂ O ₅ thin film electrode prepared in this example is shown in FIG. 2 , the scanning voltage range is -0.2V~0.6V vs. Ag/AgCl, and the scanning speed is 0.01V/s. It can be seen from the figure that there are two pairs of obvious redox peaks in the cyclic voltammetry curve of the V ₂ O ₅ film, indicating that the intercalation process of Li ⁺ ions on the V ₂ O ₅ film electrode is carried out in two steps, and There is no irreversible phase transition, which is beneficial to improve the performance of lithium-ion batteries. The V ₂ O ₅ film has an oxidation peak at 0.14V and 0.34V respectively, corresponding to the Li ⁺ ion extraction process on the V ₂ O ₅ film electrode; a reduction peak appears at -0.04V and 0.19V respectively , corresponding to the intercalation process of Li ⁺ ions on the V ₂ O ₅ film electrode, and the potential difference of the first pair of oxidation/reduction peaks is 0.18V, and the potential difference of the second pair of oxidation/reduction peaks is 0.15V, indicating that V ₂ O ₅ thin film electrode material has good reversibility.

The constant current charge and discharge capacity curve of the V ₂ O ₅ thin film electrode prepared in this example is shown in Figure 3. The charge and discharge current is 5.84*10 ^-6 A (mass current density: 400mA/g), and the charge and discharge voltage range is -0.1~0.5V vs. Ag/AgCl, as can be seen from the figure, on the charge and discharge curve, there are two stable discharge voltage platforms, the curve is full, and the downward trend of the curve suddenly increases when the discharge termination voltage is approaching. , which indicates that the material has good discharge performance.

The charge and discharge curves of the V ₂ O ₅ thin film electrode prepared in this example under different current densities are shown in Figure 4. It can be seen from the figure that when the current density is 400mA/g, the discharge voltage platform is the most stable and the discharge capacity is the largest , and with the increase of charge and discharge current density, the discharge capacity of V ₂ O ₅ thin film electrode decreased, but the change was not significant, indicating that the material can be charged and discharged at high current density.

The discharge capacity decay curves of the V ₂ O ₅ thin film electrode prepared in this example at different current densities are shown in Figure 5. It can be seen from the figure that with the increase of the discharge current density, the discharge capacity of the V ₂ O ₅ thin film electrode The discharge capacity decay rate did not change much. After 10 cycles, the _decay rates _were 14.49%, 15.07%, 22.81%, and 25.47%. Increased, still has good cycle performance.

Figure 6 is a comparison of the initial charge and discharge capacities of several V ₂ O ₅ thin film samples with a concentration of 0.008mol/L under the same conditions. The charge and discharge current density is 400mA/g, and the average initial discharge capacity is 703.56mAh/g , it can be seen from the figure that the stability and reproducibility of the material properties are good.

Example 2

A kind of high-capacity _V2O5 thin-film cathode material preparation method specific steps _for lithium-ion batteries, the same as embodiment 1, wherein:

In step (2), this embodiment is to prepare a V ₂ O ₅ sol with a concentration of 0.016 mol/L: the above-mentioned V ₂ O ₅ sol is fixed to 50ml to obtain a V ₂ O ₅ sol with a concentration of 0.016 mol/L .

The galvanostatic charge and discharge capacity curves of the V ₂ O ₅ thin film cathode material prepared from the V ₂ O ₅ sol with a concentration of 0.016 mol/L at a mass current density of 400 mA/g are shown in Figure 7 .

Example 3

A kind of high-capacity _V2O5 thin-film cathode material preparation method specific steps _for lithium-ion batteries, the same as embodiment 1, wherein:

In step (2), this embodiment is to prepare a V ₂ O ₅ sol with a concentration of 0.0054 mol/L: the above-mentioned V ₂ O ₅ sol is fixed to 150ml to obtain a V ₂ O ₅ sol with a concentration of 0.0054 mol/L .

Figure 8 shows the galvanostatic charge and discharge capacity curves of the V ₂ O ₅ thin film cathode material prepared from the V ₂ O ₅ sol with a concentration of 0.0054 mol/L at a mass current density of 400 mA/g.

Example 4

A kind of high-capacity _V2O5 thin-film cathode material preparation method specific steps _for lithium-ion batteries, the same as embodiment 1, wherein:

In step (2), this embodiment is to prepare a V ₂ O ₅ sol with a concentration of 0.004 mol/L: the above-mentioned V ₂ O ₅ sol is fixed to 200ml to obtain a V ₂ O ₅ sol with a concentration of 0.004 mol/L .

The galvanostatic charge and discharge capacity curves of the V ₂ O ₅ thin film cathode material prepared from the V ₂ O ₅ sol with a concentration of 0.004 mol/L at a mass current density of 400 mA/g are shown in Figure 9 .

Example 5

A kind of high-capacity _V2O5 thin-film cathode material preparation method specific steps _for lithium-ion batteries, the same as embodiment 1, wherein:

In step (2), this embodiment is to prepare a V ₂ O ₅ sol with a concentration of 0.0032 mol/L: the above-mentioned V ₂ O ₅ sol is fixed to 250ml to obtain a V ₂ O ₅ sol with a concentration of 0.0032 mol/L .

Figure 10 shows the galvanostatic charge and discharge capacity curves of the V ₂ O ₅ thin film cathode material prepared from the V ₂ O ₅ sol with a concentration of 0.0032 mol/L under the condition of a mass current density of 400 mA/g.

Example 6

A kind of high-capacity _V2O5 thin-film cathode material preparation method specific steps _for lithium-ion batteries, the same as embodiment 1, wherein:

In step (2), this example is to prepare a V ₂ O ₅ sol with a concentration of 0.002 mol/L: set the volume of the above V ₂ O ₅ sol to 400ml to obtain a V ₂ O ₅ sol with a concentration of 0.002 mol/L .

The galvanostatic charge and discharge capacity curves of the V ₂ O ₅ thin film cathode material prepared from the V ₂ O ₅ sol with a concentration of 0.002 mol/L at a mass current density of 400 mA/g are shown in Figure 11 .

Claims (1)

1. A high-capacity V ₂ O ₅ thin-film electrode for lithium-ion batteries, which is prepared by the following method: (1) Preparation of V ₂ O ₅ sol: Take 3mL of 30% hydrogen peroxide solution in a 25mL beaker, then put 0.146g of V ₂ O ₅ powder into the beaker, stir fully and slowly at room temperature to completely dissolve the V ₂ O ₅ powder , then add 2mL deionized water and continue to stir until a stable reddish-brown sol is formed; (2) Preparation of sols with different concentrations: Dilute the above-mentioned V ₂ O ₅ sols to 50mL-400ml respectively to obtain V ₂ O ₅ sols with a concentration range of 0.002mol/L to 0.016mol/L; (3) Pretreatment of the Pt substrate: immerse the Pt sheet in hydrogen peroxide for 10 minutes, then rinse it with deionized water, and dry it naturally; (4) Preparation of V ₂ O ₅ thin film electrode: Take 10 μL of V ₂ O ₅ sol with the desired concentration with a pipette, spread it on the pretreated Pt sheet, dry it naturally, and place it in a muffle furnace at 500°C for calcination After 2 hours, cool naturally to room temperature to obtain a V ₂ O ₅ thin film electrode.