CN105304877A - Sulfur-series anode material, preparation method thereof and battery - Google Patents

Abstract

The present invention provides a chalcogenide cathode material, the chemical formula is shown in formula (I) or formula (II): S _1-x M _x (I); S _1-x M _x /C (II); wherein, 0 <x<1; M is any one or more of Se, Te, I, P, Bi, Sn. Compared with the existing sulfur cathode materials, the material provided by the invention can effectively solve the problems of dissolution of intermediate products in the cycle process of sulfur electrode materials, and obtain excellent electrochemical performance. At the same time, this type of material can be used in the electrolyte of conventional lithium-ion batteries, which further solves the compatibility problem of this material with other high-performance lithium-ion battery electrode materials to assemble full batteries.

Description

Chalcogenide cathode material, preparation method thereof, and battery

technical field

The invention relates to the technical field of materials, in particular to a chalcogenide cathode material, a preparation method thereof and a battery.

Background technique

Lithium-ion battery is a secondary rechargeable battery that mainly relies on lithium ions to move between positive and negative electrodes to work. During the charge and discharge process, Li ⁺ intercalates and deintercalates back and forth between the two electrodes: during charging, Li ⁺ deintercalates from the positive electrode, intercalates through the electrolyte into the negative electrode, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. Due to its high volume specific energy and mass specific energy, rechargeable and non-polluting, it has been widely used in modern digital products such as mobile phones and notebook computers.

However, due to the limitations of the specific capacity and energy density of traditional positive electrode materials, such as LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ and other materials, the specific capacity is less than 200mAhg ^-1 , making the energy density of commercial lithium-ion secondary batteries only is 150-200Whkg ^-1 , it is difficult to be further improved, and it has been unable to meet the growing demand for high energy storage power supply. Therefore, it is particularly important to develop new lithium-ion battery electrode materials with high energy density.

The theoretical specific capacity of the elemental sulfur cathode material is 1672mAhg ^-1 , which is more than eight times that of the traditional cathode material. The energy density of a lithium-sulfur battery composed of elemental sulfur as the cathode material and metal lithium as the anode material can reach 2600Whkg ^-1 . Therefore, Lithium-sulfur batteries have become a new generation of high-energy battery systems that researchers are competing to develop. However, the practical application of lithium-sulfur batteries still faces many problems, such as the poor conductivity between sulfur and the discharge product lithium sulfide, and the volume change of 79% during the charge and discharge process. Among them, the polysulfides generated during the cycle are easily soluble in the electrolyte, causing the shuttle effect, leading to the loss of active electrode materials and low Coulombic efficiency, which are the most important factors limiting the performance of lithium-sulfur batteries. Therefore, improving the lithium storage performance of sulfur cathode materials and inhibiting the dissolution of polysulfide intermediates, especially in the electrolyte of conventional lithium-ion batteries, are the primary problems to be solved urgently.

Traditional methods mainly use various substrate materials such as carbon materials to confine sulfur to improve the lithium storage performance of sulfur cathode materials. For example, the Canadian Nazar research group used ordered mesoporous carbon CMK-3 with double pore diameters as the substrate material. When the sulfur loading was 70wt%, the specific capacity was maintained at 1000mAhg-1 after 20 cycles at a current density of 0.168mAhg-1 ( Literature 1, Nat. Mater., 2009, 8, 500-506). But this method can only slow down rather than avoid the dissolution process of polysulfides, and cannot fundamentally solve the problem.

On the other hand, by using a material with a stronger chemical interaction with the sulfur cathode material as the substrate, the dissolution and shuttling effect of polysulfides can be greatly reduced, thereby improving the cycle stability of the battery. For example, doping porous carbon materials with nitrogen can increase the electronegativity of the carbon material surface and increase the adsorption of easily soluble Li ₂ S _x . Nitrogen doping of porous carbon substrates can improve the lithium storage performance of sulfur cathodes (Document 2, Angew. Chem., 2015, 127, 4399-4403; Document 3, Advanced Materials, 2014, 26, 6100-6105).

At present, how to further improve the electrochemical performance of sulfur cathode materials is an urgent problem to be solved in this field.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a chalcogenide cathode material, a preparation method thereof, and a battery.

The present invention provides a sulfur-based cathode material, the chemical formula of which is shown in formula (I) or formula (II):

S _1-x M _x (I);

S _1-x M _x /C(Ⅱ);

Among them, 0<x<1;

M is any one or more of Se, Te, I, P, Bi, Sn.

Preferably, in the positive electrode material, the molar content of S is greater than 90%.

The present invention also provides a method for preparing the above-mentioned chalcogenide cathode material, comprising:

Mix sulfur powder with M and carbon substrate, and carry out co-melting reaction under sealed conditions to obtain sulfur-based positive electrode materials;

The M is any one or more of selenium powder, antimony powder, iodine, red phosphorus, bismuth, tin;

The added amount of the carbon substrate is 0%-80% of the total mass of raw materials.

Preferably, the carbon substrate is any one or more of graphene, porous carbon material, carbon nanotube and CMK-3.

Preferably, the molar ratio of the sulfur powder to M is (70:30)˜(99.6:0.4).

Preferably, the molar ratio of the sulfur powder to M is (9-99):1.

Preferably, the temperature of the co-melting reaction is 60° C. to 500° C., and the time is 30 minutes to 120 hours.

Preferably, the mixing is ball milling.

The present invention also provides a battery, which uses the above-mentioned sulfur-based positive electrode material or the sulfur-based positive electrode material prepared by the above-mentioned preparation method as the positive electrode material.

The present invention provides a chalcogenide cathode material, the chemical formula is shown in formula (I) or formula (II): S _1-x M _x (I); S _1-x M _x /C (II); wherein, 0 <x<1; M is any one or more of Se, Te, I, P, Bi, Sn. Compared with the existing sulfur cathode materials, the material provided by the invention can effectively solve the problems of dissolution of intermediate products in the cycle process of sulfur electrode materials, and obtain excellent electrochemical performance. At the same time, this type of material can be used in the electrolyte of conventional lithium-ion batteries, which further solves the compatibility problem of this material with other high-performance lithium-ion battery electrode materials to assemble full batteries. Among them, the S _1-x M _x /C material prepared by the present invention, when used in the positive electrode of a lithium battery, exhibits a specific capacity and energy density much higher than that of a commercial lithium battery positive electrode material. At the same time, the material can be further applied to sodium batteries. The experimental results show that the S _{1-x Sex} /C material prepared by the present invention is applied to lithium-sulfur batteries, and its lithium storage capacity can be as high as 1050mAh/g in common ester electrolytes, and it has a long cycle life. The capacity remains at 953mAh/g after 500 cycles.

The present invention also provides a method for preparing the above-mentioned sulfur-based positive electrode material, comprising: mixing sulfur powder with M and a carbon substrate, and carrying out a fusion reaction under sealed conditions to obtain a sulfur-based positive electrode material; the M is selenium powder, Any one or more of antimony powder, iodine, red phosphorus, bismuth, and tin; the amount of the carbon substrate added is 0% to 80% of the total mass of raw materials. The present invention directly uses elemental sulfur as a raw material to carry out co-melting reaction, the raw material is cheap and easy to obtain, greatly reduces the reaction cost, and has wide universality, the required temperature is low, the preparation process is environmentally friendly, the yield is high, and it is beneficial to scale-up Production; at the same time, the fusion of one or more elements can be realized.

Description of drawings

Fig. 1 is the x-ray diffraction spectrum of the Si _- xSex/C ( _x =0.1) material prepared in Example 1 of the present invention at different temperatures;

Fig. 2 is the scanning electron micrograph of embodiment 1 of the present invention;

Fig. 3 is the transmission electron microscope figure of embodiment 1 of the present invention;

Fig. 4 is the x-ray diffraction spectrum of the Si _- xSex ( _x =0.1) material prepared in Example 2 of the present invention at different temperatures;

Fig. 5 is the X-ray diffraction spectrum at 260°C of the S _1-x Se _x /C (x=0.2) material prepared in Example 3 of the present invention;

Fig. 6 is the lithium-sulfur battery charge-discharge curve diagram of the Si _- xSex/C ( _x =0.1) material obtained in Example 9;

Fig. 7 is the lithium-sulfur battery electrochemical cycle stability diagram of the Si _- xSex/C ( _x =0.1) material obtained in Example 9;

Fig. 8 is the lithium-sulfur battery electrochemical rate performance diagram of the Si _- xSex/C ( _x =0.1) material obtained in Example 9;

Fig. 9 is a sodium-sulfur battery electrochemical cycle stability diagram of the S _1-x Se _x /C (x=0.1) material obtained in Example 9;

Fig. 10 is the electrochemical rate performance diagram of the sodium-sulfur battery of the Si _- xSex/C ( _x =0.1) material obtained in Example 9;

Fig. 11 is a lithium-sulfur battery charge and discharge curve of the S _1-x P _xy I _y /CMK-3 (x=0.07, y=0.02) material obtained in Example 9;

Fig. 12 is the electrochemical cycle stability diagram of the lithium-sulfur battery of the S _1-x P _xy I _y /CMK-3 (x=0.07, y=0.02) material obtained in Example 9;

Fig. 13 is the lithium-sulfur battery charge-discharge curve diagram of the Si _- xBix/C ( _x =0.03) material obtained in Example 9;

Fig. 14 is a diagram of the electrochemical cycle stability of the lithium-sulfur battery of the S _1-x Bi _x /C (x=0.03) material obtained in Example 9.

detailed description

The present invention provides a chalcogenide cathode material, the chemical formula is shown in formula (I) or formula (II): S _1-x M _x (I); S _1-x M _x /C (II); wherein, 0 <x<1; M is any one or more of Se, Te, I, P, Bi, Sn.

Compared with the existing sulfur cathode materials, the material provided by the invention can effectively solve the problems of dissolution of intermediate products in the cycle process of sulfur electrode materials, and obtain excellent electrochemical performance. At the same time, this type of material can be used in the electrolyte of conventional lithium-ion batteries, which further solves the compatibility problem of this material with other high-performance lithium-ion battery electrode materials to assemble full batteries. When the S _1-x M _x /C material prepared by the invention is used in the positive electrode of lithium battery, it shows a specific capacity and energy density much higher than that of the positive electrode material of commercial lithium battery. At the same time, the material can be further applied to sodium batteries. The experimental results show that the S _{1-x Sex} /C material prepared by the present invention is applied to lithium-sulfur batteries, and its lithium storage capacity can be as high as 1050mAh/g in common ester electrolytes, and it has a long cycle life. The capacity remains at 953mAh/g after 500 cycles.

Preferably, in the positive electrode material of the present invention, the molar content of S is greater than 90%. In the present invention, the molar content of S refers to the molar ratio of S to the total amount of S and M in the material.

The anode material provided by the present invention, in addition to the Se element, also introduces P, I, Te, Bi, Sn elements, wherein P, I and Te all have lower toxicity and are relatively friendly to the environment, and at the same time, P has a relatively low toxicity. The low molecular weight can effectively reduce the influence of the introduction of heteroatoms on the energy density of the material; the introduction of I can increase the voltage platform.

The present invention also provides a method for preparing the above-mentioned chalcogenide cathode material, comprising:

Mix sulfur powder with M and carbon substrate, and carry out co-melting reaction under sealed conditions to obtain sulfur-based positive electrode materials;

The M is any one or more of selenium powder, antimony powder, iodine, red phosphorus, bismuth, tin;

The added amount of the carbon substrate is 0% to 80% of the total mass of raw materials, more preferably 0% to 70% of the total mass of raw materials. In some specific embodiments of the present invention, the added amount of the carbon substrate is 40% to 70% of the total mass of raw materials.

Wherein, the molar ratio of the sulfur powder to M is preferably (70:30)-(99.6:0.4), more preferably (9-99):1.

In the present invention, the carbon substrate is preferably any one or more of graphene, porous carbon material, carbon nanotube and CMK-3.

The present invention has no special restrictions on the above-mentioned sulfur powder, selenium powder, antimony powder, iodine, red phosphorus, bismuth, tin, graphene, porous carbon material, carbon nanotubes and CMK-3, which can be commercially available. Among them, the porous carbon material can also be prepared by thermal decomposition of transition metal complexes.

First, mix the sulfur powder with M and the carbon base, the mixing can be a mixing method well known to those skilled in the art, in some specific embodiments, it is ball milling, preferably adding deionized water wet ball milling, the ball milling The time is preferably 1h to 72h, more preferably 5h to 24h.

The ball-milled material is sealed in a reactor for co-melting reaction. In the present invention, the temperature of the co-melting reaction is preferably 60°C-500°C, more preferably 150°C-400°C; the time is preferably 30min-120h, more preferably 5h-24h.

In some embodiments of the invention, the reaction is carried out in an autoclave.

The S _1-x M _x /C product prepared by the present invention is mainly used in electrochemical energy storage, and the prepared product is made into a lithium battery pole piece, and as a positive electrode material, it can be assembled with a lithium sheet electrode to form a lithium-sulfur battery. It can also be assembled with sodium sheet electrodes to form a sodium-sulfur battery, and further commercial negative electrode materials such as graphite negative electrodes can be used to assemble full batteries. When this material is used as a cathode material for lithium-sulfur batteries, it exhibits high lithium storage capacity, high Coulombic efficiency, and long cycle stability in commercial ester electrolytes.

The present invention also provides a battery, which uses the above-mentioned sulfur-based positive electrode material or the sulfur-based positive electrode material prepared by the above-mentioned preparation method as the positive electrode material.

Preferably in the present invention, the battery is a lithium-sulfur battery or a sodium-sulfur battery.

In order to further illustrate the present invention, the chalcogenide positive electrode material and its preparation method and a battery provided by the present invention will be described in detail below with reference to examples.

Example 1 A S _1-x Se _x /C (x=0.1) material was prepared using a porous carbon material as a substrate.

Take 5 grams of sulfur powder, 1.2 grams of selenium powder and 4 grams of porous carbon, mix them by wet ball milling for 24 hours, seal them in a 10mL reaction kettle, place them under a resistance crucible furnace, react at 220°C for 10 hours, and then cool naturally to Room temperature; S _1-x Se _x /C (x=0.1) material can be obtained after opening the kettle.

The prepared S ₁ -x Se _x /C (x=0.1) material was analyzed by X-ray powder diffractometer, and Fig. 1 shows the Si _1-x Se _x /C (x = 0.1) X-ray diffraction spectra of materials at different temperatures. It can be seen from Figure 1 that in the X-ray diffraction spectrum, there are only clearly visible amorphous diffraction peaks in the range of 2θ in the range of 10° to 80°, which proves that the material has an amorphous phase structure.

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the results are shown in Fig. 2 and Fig. 3, wherein, Fig. 2 is the scanning electron microscope figure of embodiment 1 of the present invention, Fig. 3 is the transmission electron microscope figure of embodiment 1 of the present invention, by Fig. 2 and Figure 3, it can be seen that the S _1- x Sex /C ( _x =0.1) material prepared by the present invention is a nanoporous structure with a size of about 30nm, and the pores are evenly distributed in the range of several nanometers (<10nm).

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content to the selenium content of the material was about 9:1, that is, the molar content of S was 90%.

Example 2

Take 5 grams of sulfur powder and 1.2 grams of selenium powder, mix them by wet ball milling for 24 hours, seal them in a 10mL reaction kettle, place them under a resistance crucible furnace, react at 200°C for 10 hours, and then cool naturally to room temperature; The S _1-x Se _x (x=0.1) material can be obtained.

The X-ray diffraction analysis of the prepared S _1-x Se _x (x=0.1) material was carried out by using an X-ray powder diffractometer, and the results are shown in Figure 4. Figure 4 shows the Si _-x Se _x (x =0.1) X-ray diffraction spectra of materials at different temperatures. It can be seen from Figure 4 that after the temperature is greater than 110°C, the XRD of the product corresponds to a structure similar to monoclinic sulfur.

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the result shows, the S _1-x Se _x (x=0.1) material that the present invention prepares is the nano-porous structure of size about 200nm, and hole is evenly distributed in several nanometers (<10nm ) range.

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content to the selenium content of the material was about 9:1.

Example 3

Take 5 grams of sulfur powder, 2.4 grams of selenium powder, and 6 grams of porous carbon, mix them by wet ball milling for 24 hours, seal them in a 10mL reaction kettle, place them under a resistance crucible furnace, react at 200°C for 10 hours, and then cool naturally to Room temperature; S _1-x Se _x /C (x=0.2) material can be obtained after opening the kettle.

The prepared S _1-x Se _x /C (x=0.2) material was analyzed by X-ray powder diffractometer, the results are shown in Figure 5, and Figure 5 shows the S _1-x Se _x prepared in Example 3 of the present invention /C (x=0.2) X-ray diffraction spectra of materials at different temperatures. It can be seen from Figure 5 that the material has an amorphous phase structure.

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the result shows, the S _1-x Se _x /C (x=0.2) material that the present invention prepares is the nanoporous structure of size about 30nm, and hole is evenly distributed in several nanometers ( <10nm) range.

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content to the selenium content of the material was about 4:1.

Example 4

Take 5 grams of sulfur powder, 1.9 grams of antimony powder, and 4 grams of porous carbon, mix them by wet ball milling for 24 hours, seal them in a 10mL reaction kettle, place them under a resistance crucible furnace, react at 300°C for 10 hours, and then cool naturally to Room temperature; S _{1- x Tex /C (x} =0.1) material can be obtained after opening the kettle.

The X-ray diffraction analysis of the prepared S _{1- x Tex /C (x} =0.1) material was carried out by X-ray powder diffractometer, and the result showed that the material had an amorphous phase structure.

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the result shows, the S _{1- x Tex/C (x} =0.1) material prepared by the present invention is the nano-porous structure of size about 30nm, and hole is evenly distributed in several nanometers ( <10nm) range.

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content to the antimony content of the material was about 9:1.

Example 5

Take 5 grams of sulfur powder, 0.6 grams of selenium powder, 0.95 grams of antimony powder, and 4 grams of porous carbon, mix them by wet ball milling for 24 hours, seal them in a 10 mL reaction kettle, place them under a resistance crucible furnace, and react at 350 ° C for 10 hours , and then naturally cooled to room temperature; the S _1-x Sexy Te _y /C (x=0.1, _y= 0.05) material can be obtained after opening the kettle.

The prepared S _1-x Sexy Te _y /C (x=0.1, _y= 0.05) material was analyzed by X-ray powder diffractometer, and the results showed that the material had an amorphous phase structure.

The structure of the material was detected by scanning electron microscopy and transmission electron microscopy, and the results showed that the S _1-x Sexy Te _y /C (x=0.1, _y= 0.05) material prepared by the present invention is a nanoporous structure with a size of about 30nm, and the pores are uniform Distributed in the range of a few nanometers (<10nm).

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content of the material to the total content of selenium and antimony was about 9:1.

Example 6

Mix 5 grams of sulfur powder, 1.2 grams of selenium powder and 1 gram of graphene, disperse the slurry to 100 mg/mL with water, mix it by wet ball milling for 24 hours, seal it in a 10 mL reaction kettle, and place it under a resistance crucible furnace , reacted at 200°C for 10h, and then naturally cooled to room temperature; the S _1-x Se _x /G (x=0.1) material can be obtained after opening the kettle.

The X-ray diffraction analysis of the prepared S _1-x Se _x /G (x=0.1) material was carried out by X-ray powder diffractometer, and the result showed that the material had an amorphous phase structure.

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the result shows, the S _1-x Se _x /G (x=0.1) material that the present invention prepares is the nano-porous structure of size about 50nm, and hole is evenly distributed in several nanometers ( <10nm) range.

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content to the selenium content of the material was about 9:1.

Example 7

Take 5 grams of sulfur powder, 0.25 grams of red phosphorus powder, 0.41 grams of elemental iodine and 1 gram of CMK-3, mix them by wet ball milling for 24 hours, seal them in a 10mL reactor, place them under a resistance crucible furnace, and heat them at 280°C React for 10 h, then cool down to room temperature naturally; after opening the kettle, the material S _1-x P _{xyI y} /CMK-3 (x=0.07, y=0.02) can be obtained.

The X-ray diffraction analysis of the prepared S _1-x P _{xyI y} /CMK-3 (x=0.07, y=0.02) material was carried out by X-ray powder diffractometer, and the result showed that the material had an amorphous phase structure.

The structure of the material was detected by scanning electron microscopy and transmission electron microscopy, and the results showed that the S _1-x P _xy I _y /CMK-3 (x=0.07, y=0.02) material prepared by the present invention is a nanoporous structure with a size of about 40nm. The pores are uniformly distributed in the range of a few nanometers (<10nm).

The composition of the material was analyzed by atomic absorption spectroscopy, and the results showed that the molar ratio of the sulfur content of the material to the total content of phosphorus and iodine was about 93:7.

Example 8

Take 5 grams of sulfur powder, 1 gram of bismuth powder and 4 grams of porous carbon, mix them by wet ball milling for 24 hours, seal them in a 10mL reaction kettle, place them under a resistance crucible furnace, react at 280°C for 10 hours, and then cool naturally to room temperature; the S _1-x Bi _x /C (x=0.03) material can be obtained after opening the kettle.

The X-ray diffraction analysis of the prepared S _1-x Bi _x /C (x=0.03) material was carried out by X-ray powder diffractometer, and the results showed that there were no other peaks except the diffraction peak of Bi ₂ S ₃ .

Adopt scanning electron microscope and transmission electron microscope to detect material structure, the result shows, the Si _-x Bi _x /C (x=0.03) material prepared by the present invention is the nanoporous structure of size about 40nm, and hole is evenly distributed in several nanometers ( <10nm) range.

Example 9

The S _1-x Se _x /C (x=0.1) material prepared in Example 1, the S _1-x P _{xyI y} /CMK-3 prepared in Example 7, and the S _1-x Bi prepared in Example 8 were respectively _X /C material is made into CR2016 button battery electrode sheet, and the electrode sheet adopts 70wt% of the sulfur-based positive electrode material prepared in the corresponding embodiment, 10wt% of sodium alginate, 20% of conductive carbon black, and water to mix. The substrate of the film is metal aluminum foil.

A lithium sheet was used as the counter electrode, a polyolefin porous membrane (Celgard2500) was used as the separator, and a mixed solution of LiPF ₆ ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1) was used as the electrolyte. A CR2016 lithium-sulfur battery was installed in a glove box with an argon atmosphere.

Using sodium sheet as the counter electrode, polyolefin porous membrane (Celgard2500) as the separator, and a mixed solution of NaPF ₆ ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte, in A CR2016 sodium-sulfur battery was installed in a glove box with an argon atmosphere.

The electrochemical performance of the lithium-sulfur battery and the sodium-sulfur battery assembled by S _1-x Se _x /C (x=0.1) was tested. The performance results of the lithium-sulfur battery are shown in Figures 6 to 8, and Figure 6 is prepared in Example 9. The charge and discharge curves of lithium-sulfur batteries at a current density of 0.2Ag ^-1 , where curve a is the charge and discharge curve of the first cycle, curve b is the charge and discharge curve of the second cycle, and curve c is the charge and discharge curve of the third cycle Charge-discharge curve diagram, curve d is the charge-discharge curve diagram of the fourth circle, and curve e is the charge-discharge curve diagram of the fifth circle; Fig. 7 is the lithium-sulfur battery prepared in Example 9 electrochemically at a current density of 0.5Ag ^-1 Cycle stability diagram, Figure 8 is the electrochemical rate performance diagram of the lithium-sulfur battery prepared in Example 9, as can be seen from Figure 6, when the current density is 0.2Ag ^-1 , the first-cycle coulombic efficiency of the lithium-sulfur battery is 55%, The Coulombic efficiency then remained above 99.5%. In Figure 7, after pre-cycling at a low current density of 0.2Ag- ¹ , the reversible specific capacity of the lithium-sulfur battery can still be maintained at 953mAhg- ¹ after 500 cycles at a current density of 0.5Ag ^-1 , showing excellent cycle stability. In the rate performance test in Figure 8, the assembled lithium-sulfur battery still has a specific capacity of 572mAhg ^-1 at a current density of 20Ag ^-1 , indicating that it has excellent rate performance.

The performance of the sodium-sulfur battery assembled with S _1-x Se _x /C (x=0.1) is shown in Figures 9-10. Figure 9 shows the cycle performance of the assembled sodium-sulfur battery at a current density of 0.2Ag ^-1 . The Coulombic efficiency in the first cycle is about 52%. After 150 cycles, the reversible specific capacity remains at 937mAhg ^-1 . In the rate performance test in Figure 10, the assembled sodium-sulfur battery still has a specific capacity of 328mAhg ^-1 at a current density of 20Ag ^-1 , indicating that it has a good rate performance.

The performance of the lithium-sulfur battery assembled by S _1-x P _{xyI y} /CMK-3C is shown in Fig. 11-12. Among them, Fig. 11 is the lithium-sulfur battery charging and discharging curve of the S _1-x P _xy I _y /CMK-3 (x=0.07, y=0.02) material obtained in Example 9, and curve 1 is the first charging and discharging of the battery Curves, curves 2 and 3 correspond to the second and third charge-discharge curves respectively; Figure 12 is the electrochemical cycle stability diagram of the assembled lithium-sulfur battery at a current density of 0.2Ag ^-1 , as can be seen from Figure 12, the first circle Coulombic efficiency is about 63%, and the reversible specific capacity remains at 837mAhg ^-1 after 350 cycles.

The performance of Li-S batteries assembled by S _1-x Bi _x /C is shown in Fig. 13-14. Wherein, Fig. 13 is the charging and discharging curve diagram of the lithium-sulfur battery of the S _1-x Bi _x /C (x=0.03) material obtained in Example 9, curve 1 is the first charging and discharging curve of the battery, and curves 2 and 3 respectively correspond to In the second and third charge-discharge curves; Figure 14 is the electrochemical cycle stability diagram of the assembled lithium-sulfur battery at a current density of 0.2Ag ^-1 . It can be seen from Figure 14 that the first-cycle Coulombic efficiency is about 72%, and the cycle After 300 cycles, the reversible specific capacity remained at 885mAhg ^-1 .

It can be seen from the above examples that the battery prepared by using the chalcogenide cathode material provided by the present invention has excellent electrochemical performance.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (9)

1. a sulphur system positive electrode, chemical formula is such as formula shown in (I) or formula (II):

S _1-xM _x(I)；

S _1-xM _x/C(Ⅱ)；

Wherein, 0<x<1;

M be in Se, Te, I, P, Bi, Sn any one or multiple.

2. sulphur system according to claim 1 positive electrode, is characterized in that, in described positive electrode, the molar content of S is greater than 90%.

3. a preparation method for the sulphur system positive electrode described in any one of claim 1 or 2, comprising:

Sulphur powder is mixed with M, carbon substrate, under air-proof condition, melts reaction altogether, obtain sulphur system positive electrode;

Described M be in selenium powder, antimony powder, iodine, red phosphorus, bismuth, tin any one or multiple;

The addition of described carbon substrate is 0% ~ 80% of raw material gross mass.

4. preparation method according to claim 3, is characterized in that, described carbon substrate be in Graphene, porous carbon materials, carbon nano-tube and CMK-3 any one or multiple.

5. preparation method according to claim 3, is characterized in that, the mol ratio of described sulphur powder and M is (70:30) ~ (99.6:0.4).

6. preparation method according to claim 5, is characterized in that, the mol ratio of described sulphur powder and M is (9 ~ 99): 1.

7. preparation method according to claim 3, is characterized in that, described temperature of melting reaction is altogether 60 DEG C ~ 500 DEG C, and the time is 30min ~ 120h.

8. preparation method according to claim 3, is characterized in that, described in be mixed into ball milling mixing.

9. a battery, the sulphur system positive electrode prepared with the preparation method described in the sulphur system positive electrode described in any one in claim 1 ~ 2 or any one in claim 3 ~ 9 is for positive electrode.