Preparation method and application of tetragonal NaV2O5H2O nanosheet-like powder

Abstract

A preparation method of a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder includes steps of: (Step 1) simultaneously adding NaVO.sub.3 and Na.sub.2S.9H.sub.2O into deionized water, and then magnetically stirring, and obtaining a black turbid solution; (Step 2) sealing after putting the black turbid solution into an inner lining of a reaction kettle, fixing the sealed inner lining in an outer lining of the reaction kettle, placing the reaction kettle into a homogeneous reactor, and then performing a hydrothermal reaction; and (Step 3) after completing the hydrothermal reaction, naturally cooling the reaction kettle to the room temperature, and then alternately cleaning through water and alcohol, and then collecting a product, drying the product, and finally obtaining the tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder with a thickness in a range of 30-60 nm and a single crystal structure grown along a (002) crystal orientation.

Claims

1. A preparation method of a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder used as an anode material of a lithium ion battery, wherein: the tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder has a thickness in a range of 30-60 nm and a layer spacing of 7.71 Å, and is a single crystal layered structure grown along a (002) crystal orientation; when the tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder acts as the anode material of the lithium ion battery, at a current density of 100, 200, 500, 1000 and 2000 mAg.sup.−1, a capacity reaches 348, 285, 209, 167 and 130 mAhg.sup.−1, respectively; at the current density of 100 and 200 mAg.sup.−1, a first discharge capacity reaches 859 and 633 mAhg.sup.−1, respectively; and after 480 and 600 cycles, the capacity reaches 483 and 320 mAhg.sup.−1, respectively; and after 1000 cycles at the current density of 1000 mAg.sup.−1, the capacity reaches 129 mAhg.sup.−1; the preparation method comprises the steps of: (Step 1) simultaneously adding 0.8-1.2 g of NaVO.sub.3 and 0.5-3.5 g of Na.sub.2S.9H.sub.2O into 55-65 ml of deionized water, and then magnetically stirring, and obtaining a black turbid solution; (Step 2) sealing after putting the black turbid solution into an inner lining of a reaction kettle according to a filling ratio in a range of 55-65%, fixing the sealed inner lining in an outer lining of the reaction kettle, placing the reaction kettle into a homogeneous reactor, and then heating under a rotational speed in a range of 5-15 r/min from a room temperature to 150-200° C., and then performing a hydrothermal reaction; and (Step 3) after completing the hydrothermal reaction, naturally cooling the reaction kettle to the room temperature, and then alternately cleaning through water and alcohol, and then collecting a product, and drying the product at 40-80° C., thereby obtaining the tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder.

2. The preparation method according to claim 1, wherein in the step of (Step 1), the magnetic stirring is performed for 55-65 min under a rotational speed in a range of 800-1000 r/min.

3. The preparation method according to claim 2, wherein in the step of (Step 2), the hydrothermal reaction is performed for 1-36 h.

4. The preparation method according to claim 3, wherein in the step of (Step 3), the alternate cleaning is performed by suction filtration or centrifugation for 3-6 times, and the collecting is performed by suction filtration or centrifugation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is an XRD (X-ray diffraction) pattern of a product when a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:1, a hydrothermal reaction is performed at 180° C. for 1 h, 3 h, 6 h, 12 h, 24 h and 36 h, respectively.

[0029] FIG. 2 is an XRD pattern of a product when a hydrothermal reaction is performed at 180° C. for 24 h, and a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:0.5, 1:1.0, 1:1.5, 1:2.0 and 1:3.5, respectively.

[0030] FIG. 3 is an XRD pattern of a product when a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:1, a hydrothermal reaction is performed for 24 h at 120° C., 150° C., 180° C. and 200° C., respectively.

[0031] FIG. 4 is a low-magnification SEM (scanning electron microscopy) graph of a product prepared by a first embodiment of the present invention.

[0032] FIG. 5 is a high-magnification SEM graph of the product prepared by the first embodiment of the present invention.

[0033] FIG. 6 is an ultrahigh-magnification SEM graph of the product prepared by the first embodiment of the present invention.

[0034] FIG. 7 is a low-magnification TEM (transmission electron micrograph) of the product prepared by the first embodiment of the present invention.

[0035] FIG. 8 is a diffraction dot-matrix pattern of the product prepared by the first embodiment of the present invention.

[0036] FIG. 9 is a magnification performance chart when the product prepared by the first embodiment of the present invention acts as an anode material of a lithium ion battery.

[0037] FIG. 10 is a cycle performance chart when the product prepared by the first embodiment of the present invention acts as the anode material of the lithium ion battery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038] The present invention is further described with accompanying drawings in detail as follows.

First Embodiment

[0039] Step 1: Simultaneously add 1.0 g of NaVO.sub.3 and 1.0 g of Na.sub.2S.9H.sub.2O into 60 ml of deionized water, and then magnetically stir at a rotational speed of 1000 r/min for 55 min, and obtain a black turbid solution;

[0040] Step 2: Seal after putting the black turbid solution into an inner lining of a reaction kettle according to a filling ratio of 60%, fix the sealed inner lining in an outer lining of the reaction kettle, place the reaction kettle into a homogeneous reactor, and then heat under a rotational speed of 10 r/min from a room temperature to 180° C., and then perform a hydrothermal reaction for 24 h; and

[0041] Step 3: After completing the hydrothermal reaction, naturally cool the reaction kettle to the room temperature, and then alternately clean for three times through water and alcohol by suction filtration, and then collect a product by suction filtration, dry the product at 60° C., and finally obtain a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder.

Second Embodiment

[0042] According to the second embodiment of the present invention, the hydrothermal reaction is performed for 1 h, and other conditions in the second embodiment are same as those in the first embodiment.

Third Embodiment

[0043] According to the third embodiment of the present invention, the hydrothermal reaction is performed for 3 h, and other conditions in the third embodiment are same as those in the first embodiment.

Fourth Embodiment

[0044] According to the fourth embodiment of the present invention, the hydrothermal reaction is performed for 6 h, and other conditions in the fourth embodiment are same as those in the first embodiment.

Fifth Embodiment

[0045] According to the fifth embodiment of the present invention, the hydrothermal reaction is performed for 12 h, and other conditions in the fifth embodiment are same as those in the first embodiment.

Sixth Embodiment

[0046] According to the sixth embodiment of the present invention, the hydrothermal reaction is performed for 36 h, and other conditions in the sixth embodiment are same as those in the first embodiment.

Seventh Embodiment

[0047] According to the seventh embodiment of the present invention, a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:0.5, and other conditions in the seventh embodiment are same as those in the first embodiment.

Eighth Embodiment

[0048] According to the eighth embodiment of the present invention, a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:1.5, and other conditions in the eighth embodiment are same as those in the first embodiment.

Ninth Embodiment

[0049] According to the ninth embodiment of the present invention, a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:2.0, and other conditions in the ninth embodiment are same as those in the first embodiment.

Tenth Embodiment

[0050] According to the tenth embodiment of the present invention, a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:3.5, and other conditions in the tenth embodiment are same as those in the first embodiment.

Eleventh Embodiment

[0051] According to the eleventh embodiment of the present invention, the hydrothermal reaction is performed at 120° C., and other conditions in the eleventh embodiment are same as those in the first embodiment.

Twelfth Embodiment

[0052] According to the twelfth embodiment of the present invention, the hydrothermal reaction is performed at 150° C., and other conditions in the twelfth embodiment are same as those in the first embodiment.

Thirteenth Embodiment

[0053] According to the thirteenth embodiment of the present invention, the hydrothermal reaction is performed at 200° C., and other conditions in the thirteenth embodiment are same as those in the first embodiment.

[0054] FIG. 1 is an XRD (X-ray diffraction) pattern of a product when a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:1, a hydrothermal reaction is performed at 180° C. for 1 h, 3 h, 6 h, 12 h, 24 h and 36 h, respectively. It can be seen from FIG. 1 that a pure phase NaV.sub.2O.sub.5.H.sub.2O is able to be synthesized in a reaction time interval of 1 to 36 h.

[0055] FIG. 2 is an XRD pattern of a product when a hydrothermal reaction is performed at 180° C. for 24 h, and a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:0.5, 1:1.0, 1:1.5, 1:2.0 and 1:3.5, respectively. It can be seen from FIG. 2 that a pure phase NaV.sub.2O.sub.5.H.sub.2O is able to be synthesized in a mass interval of 1:0.5-1:3.5. However, when the mass ratio is decreased below 1:0 or increased above 1:3.5, a clear solution is obtained and no product is generated. Therefore, too high or too low mass ratio is adverse to the synthesis of NaV.sub.2O.sub.5.H.sub.2O.

[0056] FIG. 3 is an XRD pattern of a product when a mass ratio of NaVO.sub.3 to Na.sub.2S.9H.sub.2O is 1:1, a hydrothermal reaction is performed for 24 h at 120° C., 150° C., 180° C. and 200° C., respectively. It can be seen from FIG. 3 that a pure phase NaV.sub.2O.sub.5.H.sub.2O is able to be synthesized in a reaction temperature interval of 150-200° C. However, when the reaction temperature is decreased to 120° C., miscellaneous phase occurs in the synthesized product.

[0057] FIG. 4 is a low-magnification SEM (scanning electron microscope) graph of the product prepared by the first embodiment. It can be seen from FIG. 4 that the NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder is formed by aggregates with various sizes which are assembled by nanosheets.

[0058] FIG. 5 is a high-magnification SEM graph of the product prepared by the first embodiment of the present invention. It can be seen from FIG. 5 that the NaV.sub.2O.sub.5.H.sub.2O aggregates are self-assembled from standing nanosheets.

[0059] FIG. 6 is an ultrahigh-magnification SEM graph of the product prepared by the first embodiment of the present invention. It can be seen from FIG. 6 that each of the NaV.sub.2O.sub.5.H.sub.2O nanosheets has a thickness in a range of 30-60 nm and a smooth surface.

[0060] FIG. 7 is a low-magnification TEM (transmission electron micrograph) of the product prepared by the first embodiment of the present invention. It can be seen from FIG. 7 that the nanosheets are transparent under a projection electron microscope, indicating that the nanosheets have a small thickness. Therefore, the nanosheets seen under scanning electron microscope are formed in a stacked manner of nano sub-sheets with a smaller thickness.

[0061] FIG. 8 is a diffraction dot-matrix pattern of the product prepared by the first embodiment of the present invention. It can be seen from FIG. 8 that NaV.sub.2O.sub.5.H.sub.2O has a tetragonal phase crystal structure, and simultaneously, the dot-matrix structure shows that the nanosheet is a single crystal structure.

[0062] FIG. 9 is a magnification performance chart when the product prepared by the first embodiment of the present invention acts as an anode material of a lithium ion battery. It can be seen from FIG. 9 that at a current density of 100, 200, 500, 1000 and 2000 mAg.sup.−1, a specific capacity can reach 348, 285, 209, 167 and 130 mAhg.sup.−1, respectively. After experiencing high magnification performance testing, when the current density returns to 100 mAg.sup.−1, the specific capacity can still reach 328 mAhg.sup.−1, and a capacity retention rate can reach 94%.

[0063] FIG. 10 is a cycle performance chart when the product prepared by the first embodiment of the present invention acts as the anode material of the lithium ion battery. It can be seen from FIG. 10 that at the current density of 100 and 200 mAg.sup.−1, a first discharge capacity can reach 859 and 633 mAhg.sup.−1, respectively; after 480 and 600 cycles, the specific capacity can still reach 483 and 320 mAhg.sup.−1, respectively; and after 1000 cycles at the current density of 1000 mAg.sup.−1, the specific capacity can still reach 129 mAhg.sup.−1.

Fourteenth Embodiment

[0064] Step 1: Simultaneously add 0.8 g of NaVO.sub.3 and 2 g of Na.sub.2S.9H.sub.2O into 65 ml of deionized water, and then magnetically stir at a rotational speed of 800 r/min for 65 min, and then obtain a black turbid solution;

[0065] Step 2: Seal after putting the black turbid solution into a reaction lining according to a filling ratio of 65%, fix the sealed reaction lining in a reaction kettle, place the reaction kettle into a homogeneous reactor, and then heat under a rotational speed of 5 r/min from a room temperature to 140° C., and then perform a hydrothermal reaction for 36 h; and

[0066] Step 3: After completing the hydrothermal reaction, naturally cool the reaction kettle to the room temperature, and then alternately clean for three times through water and alcohol by suction filtration, and then collect a product by suction filtration, dry the product at 40° C., and finally obtain a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder.

Fifteenth Embodiment

[0067] Step 1: Simultaneously add 1.2 g of NaVO.sub.3 and 1.0 g of Na.sub.2S.9H.sub.2O into 55 ml of deionized water, and then magnetically stir at a rotational speed of 900 r/min for 60 min, and then obtain a black turbid solution;

[0068] Step 2: Seal after putting the black turbid solution into a reaction lining according to a filling ratio of 55%, fix the sealed reaction lining in a reaction kettle, place the reaction kettle into a homogeneous reactor, and then heat under a rotational speed of 15 r/min from a room temperature to 190° C., and then perform a hydrothermal reaction for 1 h; and

[0069] Step 3: After completing the hydrothermal reaction, naturally cool the reaction kettle to the room temperature, and then alternately clean for five times through water and alcohol by suction filtration, and then collect a product by suction filtration, dry the product at 80° C., and finally obtain a tetragonal NaV.sub.2O.sub.5.H.sub.2O nanosheet-like powder.