Battery negative electrode material

Abstract

A negative electrode material applied to a lithium battery or a sodium battery is provided. The negative electrode material is composed of a first chemical element, a second chemical element and a third chemical element with an atomic ratio of x, 1x, and 2, wherein 0<x<1, the first chemical element is selected from the group consisting of molybdenum (Mo), chromium (Cr), tungsten (W), manganese (Mn), technetium (Tc) and rhenium (Re), the second chemical element is selected from the group consisting of Mo, Cr and W, the third chemical element is selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te), and the first chemical element is different from the second chemical element.

Claims

1. A negative electrode material, applied to a lithium battery or a sodium battery, the negative electrode material is composed of a first chemical element, a second chemical element and a third chemical element with an atomic ratio of x, 1x, and 2, wherein 0.5x<1, the first chemical element is selected from the group consisting of manganese (Mn), technetium (Tc) and rhenium (Re), the second chemical element is Cr, the third chemical element is selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te).

2. The negative electrode material of claim 1, wherein the first chemical element is Mn.

3. The negative electrode material of claim 1, wherein the third chemical element is S.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which:

(2) FIG. 1 is a diagram showing the first three charge/discharge curves of a lithium battery using MoS.sub.2 as the negative electrode material;

(3) FIG. 2 is a diagram showing cycle versus coulombic efficiency of a lithium battery using MoS.sub.2 as the negative electrode material;

(4) FIG. 3 is a diagram showing the first three charge/discharge curves of a sodium battery using MoS.sub.2 as the negative electrode material;

(5) FIG. 4 is a diagram showing cycle versus coulombic efficiency of a sodium battery using MoS.sub.2 as the negative electrode material;

(6) FIG. 5 is a diagram showing the first three charge/discharge curves of a lithium battery using the negative electrode material provided in accordance with a first preferred embodiment of the present invention;

(7) FIG. 6 is a diagram showing cycle versus coulombic efficiency of a lithium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention;

(8) FIG. 7 is a diagram showing the first three charge/discharge curves of a lithium battery using the negative electrode material provided in accordance with a second preferred embodiment of the present invention;

(9) FIG. 8 is a diagram showing cycle versus coulombic efficiency of a lithium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention;

(10) FIG. 9 is a comparison diagram showing the first three cycles of the lithium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention;

(11) FIG. 10 is a comparison diagram showing the first three cycles of the lithium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention;

(12) FIG. 11 is a diagram showing the first three charge/discharge curves of a sodium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention;

(13) FIG. 12 is a diagram showing cycle versus coulombic efficiency of a sodium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention;

(14) FIG. 13 is a diagram showing the first three charge/discharge curves of a sodium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention;

(15) FIG. 14 is a diagram showing cycle versus coulombic efficiency of a sodium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention;

(16) FIG. 15 is a comparison diagram showing the first three cycles of the sodium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention; and

(17) FIG. 16 is a comparison diagram showing the first three charge cycles of the sodium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(18) Please refer to FIG. 5 and FIG. 6, wherein FIG. 5 is a diagram showing the first three charge/discharge curves of a lithium battery using the negative electrode material provided in accordance with a first preferred embodiment of the present invention; and FIG. 6 is a diagram showing cycle versus coulombic efficiency of a lithium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention.

(19) As shown, a negative electrode material is provided in accordance with a preferred embodiment of the present invention. The negative electrode material can be applied to a lithium battery or a sodium battery, and is composed of a first chemical element, a second chemical element, and a third chemical element with an atomic ratio of x, 1-x, and 2, wherein 0<x<1. The first chemical element is selected from the group consisting of molybdenum (Mo), chromium (Cr), tungsten (W), manganese (Mn), technetium (Tc), and rhenium (Re). The second chemical element is selected from the group consisting of Mo, Cr, and W. The third chemical element is selected from the group consisting of sulfur (S), selenium (Se), and tellurium (Te). The first chemical element is different from the second chemical element.

(20) In addition, the negative electrode material provided in accordance with the present invention may be fabricated by using hydrothermal method, sol-gel method, solid state reaction method, high energy ball milling process, or co-sedimentation. In the present embodiment, the negative electrode material is fabricated by using hydrothermal method with the temperature ranged between 25 C. to 300 C. for 1 hour to 7 days. As a preferred embodiment, the hydrothermal method is proceeded at 200 C. for 3 days.

(21) In the first preferred embodiment of the present invention, the first chemical element is Cr, the second chemical element is Mo, the third chemical element is S, and x is 0.5. The negative electrode material can be represented by the chemical formula Cr.sub.0.5Mo.sub.0.5S.sub.2. In the other embodiments, the first chemical element can be the group 6B element Mo or W, the second chemical element can be the group 6B element Cr or W, and the third chemical element can be the group 6A element Se or Te.

(22) As shown in FIG. 5, the lithium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as the negative electrode material is charged at 0.1 C and then discharged during the first charge/discharge cycle. In this cycle, the charge capacity is 1116 mAh/g, the discharge capacity is 718 mAh/g, and thus the coulombic efficiency is 64.3%. Then, the lithium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material is also charged at 0.1 C and then discharged during the second charge/discharge cycle. In this cycle, the charge capacity is 766 mAh/g, the discharge capacity is 748 mAh/g, and thus the coulombic efficiency is 97.6%. As shown in FIG. 6, after 30 charge/discharge cycles at 0.1 C, the lithium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material may have a charge capacity and a discharge capacity close to 800 mAh/g.

(23) Please refer to FIG. 7 and FIG. 8, wherein FIG. 7 is a diagram showing the first three charge/discharge curves of a lithium battery using the negative electrode material provided in accordance with a second preferred embodiment of the present invention; and FIG. 8 is a diagram showing cycle versus coulombic efficiency of a lithium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention.

(24) As shown, in the second preferred embodiment of the present invention, the first chemical element is Mn, the second chemical element is Mo, the third chemical element is S, and x is 0.02. The negative electrode material can be represented by the chemical formula Mn.sub.0.02Mo.sub.0.98S.sub.2. In the other embodiments, the first chemical element can be the group 7B element Tc or Re, the second chemical element can be the group 6B element Cr or W, and the third chemical element can be the group 6A element Se or Te.

(25) As shown in FIG. 7, the lithium battery with Mn.sub.0.02Mo.sub.0.98S.sub.2 as negative electrode material is charged at 0.1 C and then discharged during the first charge/discharge cycle. In this cycle, the charge capacity is 1068 mAh/g, the discharge capacity is 798 mAh/g, and thus the coulombic efficiency is 74.7%. Then, the lithium battery with Mn.sub.0.02Mo.sub.0.98S.sub.2 as negative electrode material is also charged at 0.1 C and then discharged during the second charge/discharge cycle. In this cycle, the charge capacity is 813 mAh/g, the discharge capacity is 775 mAh/g, and thus the coulombic efficiency is 95.2%. As shown in FIG. 8, after 30 cycles at 0.1 C, the lithium battery with Mn.sub.0.02Mo.sub.0.98S.sub.2 as negative electrode material may have a charge capacity and a discharge capacity close to 600 mAh/g.

(26) Please refer to FIG. 5 to FIG. 10, wherein FIG. 9 is a comparison diagram showing the first three discharge cycles of the lithium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention; and FIG. 10 is a comparison diagram showing the first three charge cycles of the lithium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention.

(27) As shown, after replacing a portion of Mo element in the conventional MoS.sub.2 material by using the other 6B group elements or the 7B group elements, a substantial effect to the battery performance can be induced. It is noted that the charge/discharge capacity of the lithium battery using the negative electrode material provided in the first preferred embodiment of the present invention, i.e. Cr.sub.0.5Mo.sub.0.5S.sub.2, is higher than the lithium battery using MoS.sub.2 as the negative electrode material, therefore, cycle life of the lithium battery using Cr.sub.0.5Mo.sub.0.5S.sub.2 as the negative electrode material is greater than the lithium battery using MoS.sub.2 as the negative electrode material.

(28) Please refer to FIG. 11 and FIG. 12, wherein FIG. 11 is a diagram showing the first three charge/discharge curves of a sodium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention; and FIG. 12 is a diagram showing the charge/discharge cycle versus coulombic efficiency of a sodium battery using the negative electrode material provided in accordance with the first preferred embodiment of the present invention.

(29) As shown in FIG. 11, the sodium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material is charged at 0.1 C and then discharged during the first charge/discharge cycle. In this cycle, the charge capacity is 438 mAh/g, the discharge capacity is 350 mAh/g, and thus the coulombic efficiency is 79.8%. Then, the lithium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material is also charged at 0.1 C and then discharged during the second charge/discharge cycle. In this cycle, the charge capacity is 338 mAh/g, the discharge capacity is 318 mAh/g, and thus the coulombic efficiency is 94%. As shown in FIG. 12, after 10 charge/discharge cycles at 0.1 C, the sodium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material may have a charge capacity and a discharge capacity close to 350 mAh/g.

(30) Please refer to FIG. 13 and FIG. 14, wherein FIG. 13 is a diagram showing the first three charge/discharge curves of a sodium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention; and FIG. 14 is a diagram showing the charge/discharge cycle versus coulombic efficiency of a sodium battery using the negative electrode material provided in accordance with the second preferred embodiment of the present invention.

(31) As shown in FIG. 13, the sodium battery with Mn.sub.0.02Mo.sub.0.98S.sub.2 as negative electrode material is charged at 0.1 C and then discharged during the first charge/discharge cycle. In this cycle, the charge capacity is 734 mAh/g, the discharge capacity is 644 mAh/g, and thus the coulombic efficiency is 87.81%. Then, the sodium battery with Mn.sub.0.02Mo.sub.0.98S.sub.2 as negative electrode material is also charged at 0.1 C and then discharged during the second charge/discharge cycle. In this cycle, the charge capacity is 530 mAh/g, the discharge capacity is 503 mAh/g, and thus the coulombic efficiency is 94.9%. As shown in FIG. 14, after 10 charge/discharge cycles at 0.1 C, the sodium battery with Cr.sub.0.5Mo.sub.0.5S.sub.2 as negative electrode material may have a charge capacity and a discharge capacity close to 500 mAh/g.

(32) Please refer to FIG. 11 to FIG. 16, wherein FIG. 15 is a comparison diagram showing the first three discharge cycles of the sodium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention; and FIG. 16 is a comparison diagram showing the first three charge cycles of the sodium batteries using MoS.sub.2, the negative electrode material in accordance with the first preferred embodiment of the present invention, and the negative electrode material the second preferred embodiment of the present invention.

(33) As shown, after replacing a portion of Mo element in the conventional MoS.sub.2 material by using the other 6B group elements or the 7B group elements, a substantial effect on the battery performance can be induced. It is noted that charge/discharge capacity of the sodium battery using the negative electrode material provided in the second preferred embodiment of the present invention, i.e. Mn.sub.0.02Mo.sub.0.98S.sub.2, is higher than the sodium battery using MoS.sub.2 as the negative electrode material.

(34) In addition, because the price of Cr, which is about 2,900 USD per ton (in July 2017), and the price of Mn, which is about 1,900 USD per ton (in July 2017), are much lower than the price of Mo, which is about 16,000 USD per ton. Thus, material cost can be significantly reduced by using the negative electrode material provided in the present invention to replace the conventional MoS.sub.2 material.

(35) In addition, according to the experimental result, after replacing a portion of Mo element in the conventional MoS.sub.2 material by using the other 6B group elements or the 7B group elements, the lithium battery and the sodium battery still possess a certain level of battery capacity and long-term stability. Moreover, the lithium battery using Cr.sub.0.5Mo.sub.0.5S.sub.2 as the negative electrode material may have a higher cycle life, and the sodium battery using Mn.sub.0.02Mo.sub.0.98S.sub.2 as the negative electrode material may have a higher charge/discharge capacity.

(36) In addition, the atomic mass of Cr, i.e. 52, and the atomic mass of Mn, i.e. 54.94, are much smaller than the atomic mass of Mo, i.e. 95.94. Therefore, the negative electrode materials provided in accordance with the first embodiment and the second embodiment of the present invention are lighter than MoS.sub.2 such that the overall weight of the lithium battery and the sodium battery can be reduced.

(37) In conclusion, the negative electrode material provided in accordance with the first preferred embodiment of the present invention is composed of Cr, Mo, and S with the atomic ratio of 0.5, 0.5 and 2. The negative electrode material provided in accordance with the second preferred embodiment of the present invention is composed of Mn, Mo, and S with the atomic ratio of 0.02, 0.98, and 2. The lithium battery and the sodium battery using the negative electrode materials provided in the first preferred embodiment and the second preferred embodiment of the present invention may retain a certain level of battery capacity.

(38) In compared with the conventional technology using MoS.sub.2 as the negative electrode material, the lithium battery using the negative electrode material (e.g. Cr.sub.0.5Mo.sub.0.5S.sub.2) provided in accordance with the first preferred embodiment of the present invention has a longer cycle life. In addition, in compared with the conventional technology using MoS.sub.2 as the negative electrode material, the sodium battery using the negative electrode material (e.g. Mn.sub.0.02Mo.sub.0.98S.sub.2) provided in accordance with the second preferred embodiment of the present invention has a greater charge/discharge capacity.

(39) In addition, because the price of Cr and Mn are lower than the price of Mo, it would be cheaper to use the compound Cr.sub.0.5Mo.sub.0.5S.sub.2 or Mn.sub.0.02Mo.sub.0.98S.sub.2 as the negative electrode material in compared with MoS.sub.2. In addition, because Cr and Mn are lighter than Mo, the weight of the negative electrode can also be reduced.

(40) While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.