Patent Application
20220006123
The present disclosure belongs to the technical field of batteries, and in particular to a metal-sulfur battery.
With the advent of the 21st century, the energy problem is becoming more and more serious, and the environmental pollution continues to deteriorate. In order to achieve sustainable development, the utilization and development of new energy and renewable energy has become a hot research topic all over the world. Water energy, wind energy, hydrogen energy, nuclear energy, tidal energy and solar energy have been vigorously developed and utilized all over the world. The improvement of the performance of energy storage devices can effectively promote the popularization of new energy applications. Among many energy storage devices, electrochemical energy storage battery has become one of the important research directions in the world because of advantages of high energy density, good energy conversion efficiency, less pollution and convenient combination and movement.
Among all kinds of electrochemical energy storage batteries, the theoretical energy density of elemental sulfur or sulfur-based composite/metal battery is as high as 2600 Wh·Kg−1, the actual energy density can reach 300 Wh·kg−1 at present, which may increase to around 600 Wh·kg−1 in the next few years. It is considered as one of the most promising secondary lithium battery systems at present. Alkali metal lithium, sodium or potassium is used as negative electrode, which is very likely to cause lithium, sodium or potassium to form a coating on the surface of the negative electrode due to poor dynamic conditions of the negative electrode during low-temperature charging or high-rate charging. With the growth of the coating, metal dendrites will eventually form. When the metal dendrites accumulate to a certain extent, they will contact the separator, which will cause extrusion and needling on the separator, and eventually lead to mechanical failure of the separator and short circuit between the positive and negative electrodes. The generation of metal dendrites is an important factor affecting the safety performance of batteries.
The existing method for solving the metal dendrites mainly utilizes a plurality of nano technologies to modify the lithium metal current collectors, including carbon ball structures, three-dimensional metal current collectors and the like, but due to relatively complicated process, the cost cannot be further reduced, and the performance is not remarkably improved, thus large-scale production cannot be realized; Secondly, the artificial SEI film generally has the problem of low lithium ion conductivity, which does not meet the current demand for rapid charge and discharge. In recent years, a method for inhibiting the growth of lithium dendrites by effectively regulating the electrolyte has attracted much attention, which mainly solves the problem of uneven space charge distribution caused by low-concentration lithium salts by increasing the concentration of lithium salts in the electrolyte or partly increasing the concentration lithium salts, thereby uniformizing lithium metal deposition and inhibiting the growth of lithium dendrites and the generation of dead lithium. Adding film-forming additives to electrolyte with conventional lithium salt concentration is also an effective means to inhibit lithium dendrites. The above-mentioned existing technical means still can not solve the problem of metal dendrites of metal-sulfur battery.
In addition, when elemental sulfur is used as positive electrode material of lithium ion battery, the dissolution of the intermediate product lithium polysulfide (Li2Sn, 3≤n≤8) in the electrolyte leads to the problems of low coulombic efficiency of the battery and low utilization rate of active substances.
The disclosure provides a metal-sulfur battery aiming at the short circuit problem caused by lithium dendrites grown on the metal lithium of negative electrode in the existing metal-sulfur battery.
The technical solution of the present disclosure to solve the technical problems is as follows:
On one hand, the disclosure provides a metal-sulfur battery, comprising a positive electrode material, a negative electrode material and an electrolyte, the positive electrode material comprises one of elemental sulfur and S-based compound; the electrolyte comprises a solvent and an electrolyte salt; and the electrolyte salt comprises one or more salts represented by structural formulas 1-3:
wherein, R1 is selected from S or Se; R2 is selected from C, Si, Ge or Sn; M1 is selected from N, B, P, As, Sb or Bi; M2 is selected from Li, Na, K, Ru, Cs, Fr, Al, Mg, Zn, Be, Ca, Sr, Ba or Ra; R3 is selected from a carbon chain or an aromatic ring with part or all of hydrogen substituted by other elements or groups.
According to the metal-sulfur battery provided by the present disclosure, the inventor has unexpectedly found that when one or more electrolyte salts represented by structural formulas 1-3 are applied to the electrolyte of metal-sulfur battery, the effect of inhibiting the growth of metal dendrites on negative electrode is more than expected, and the battery cycle stability performance, the rate performance, the coulombic efficiency, and the safety performance of the metal-sulfur battery are effectively improved. By contrast, in conventional lithium battery systems such as lithium cobaltate/graphite, the electrolyte containing the compounds represented by the above structural formulas 1-3 does not show the above beneficial effects.
Optionally, the content of the electrolyte salt is 0.01M˜10M.
Optionally, in structural formulas 1-3, R3 is selected from a saturated carbon chain containing 1-4 carbons, an unsaturated carbon chain containing 1-4 carbons or an aromatic ring, with part or all of hydrogen substituted by a halogen element or a halogenated hydrocarbyl group.
Optionally, the electrolyte salt comprises one or more of the following compounds:
Optionally, the positive electrode material is a sulfur/carbon composite. Preferably, the positive electrode material is a ketjen black/sulfur composite.
Optionally, the electrolyte further comprises a nitrate, and the mass percentage of the nitrate is 0.1%-5% based on the mass of the electrolyte being 100%.
Optionally, the negative electrode material comprises one or more of elemental lithium, elemental sodium, elemental potassium, elemental aluminum and elemental magnesium.
Optionally, the metal-sulfur battery comprises a separator interposed between the positive electrode material and the negative electrode material.
Optionally, the metal-sulfur battery is a lithium-sulfur battery.
Optionally, the solvent is selected from one or more of a fluorinated solvent, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene sulfite and methyl propionate.
According to the metal-sulfur battery provided by the present disclosure, the inventors have unexpectedly found that for a metal-sulfur battery using one or more of a fluorinated solvent, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene sulfite, and methyl propionate as a solvent, the addition of one or more electrolyte salts represented by structural formulas 1-3 can inhibit the dissolution of sulfur in positive electrode material of the metal-sulfur battery during charging and discharging.
Optionally, the fluorinated solvent comprises one or more of fluoroethylene carbonate, 3,3,3-fluoroethyl methyl carbonate and 1,1,2,2-tetrafluoroethyl-2′,2′,2′-trifluoroethyl ether.
Optionally, the electrolyte salt further comprises one or more of LiPF6, LiBF4, LiBOB, LiClO4, LiCF3SO3, LiDFOB, LiN(SO2CF3)2 and LiN(SO2F)2.
In order to make the technical problems to be solved, technical solutions and beneficial effects provided by the present disclosure clearer, the present disclosure will be further described in detail with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, not intended to limit the present disclosure.
An embodiment of the present disclosure provides a metal-sulfur battery, including a positive electrode material, a negative electrode material and an electrolyte, the positive electrode material comprises one of elemental sulfur and S-based compound; the electrolyte comprises a solvent and an electrolyte salt; and the electrolyte salt comprises one or more salts represented by structural formulas 1-3:
wherein, R1 is selected from S or Se; R2 is selected from C, Si, Ge or Sn; M1 is selected from N, B, P, As, Sb or Bi; M2 is selected from Li, Na, K, Ru, Cs, Fr, Al, Mg, Zn, Be, Ca, Sr, Ba or Ra; R3 is selected from a carbon chain or an aromatic ring with part or all of hydrogen substituted by other elements or groups.
One or more electrolyte salts represented by structural formulas 1-3 are applied to the electrolyte of metal-sulfur battery, the effect of inhibiting the growth of metal dendrites on negative electrode is more than expected, and the battery cycle stability performance, the rate performance, the coulombic efficiency, and the safety performance of the metal-sulfur battery are effectively improved.
In some embodiments, the content of the electrolyte salt is 0.01M˜10M, preferably 0.1M˜5M.
In a more preferred embodiment, the content of the electrolyte salt is 0.1M˜2M.
In some embodiments, in structural formulas 1-3, R3 is selected from a saturated carbon chain containing 1-4 carbons, an unsaturated carbon chain containing 1-4 carbons or an aromatic ring, with part or all of hydrogen substituted by a halogen element or a halogenated hydrocarbyl group
In some embodiments, the electrolyte salt includes one or more of the following compounds:
In some embodiments, the solvent includes one or more of ethylene glycol dimethyl ether (DME), dimethyl carbonate (DMC), 1,3-dioxolane (DOL), vinylene carbonate (VC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), propylene sulfite (PS) and methyl propionate (PA).
Preferably, the positive electrode material is a sulfur/carbon composite. More preferably, it is a ketjen black/sulfur composite.
In a more preferred embodiment, the solvent is a mixture of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME).
Specifically, in the solvent, the mass ratio of 1,3-dioxolane (DOL) to ethylene glycol dimethyl ether (DME) is 0.1˜10. In a more preferred embodiment, the mass ratio of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) is 1:1.
In some embodiments, the electrolyte further includes a nitrate, and the mass percentage of the nitrate is 0.1%˜5% based on the mass of the electrolyte being 100%.
Through a large number of experiments, the inventors found that the nitrate and electrolyte salts represented by structural formulas 1-3 can be used together to improve the cycle performance of the battery more effectively.
In some embodiments, the negative electrode material comprises one or more of elemental lithium, elemental sodium, elemental potassium, elemental aluminum and elemental magnesium.
In a preferred embodiment, cations in the nitrate are selected from the same metal elements as the negative electrode material, and when the negative electrode material is selected from Li, the nitrate is selected from LiNO3; when the negative electrode material is selected from Na, the nitrate is selected from NaNO3; and when the negative electrode material is selected from K, the nitrate is selected from KNO3.
In a preferred embodiment, in structural formulas 1-3, M2 is selected from the same metal element as the negative electrode material, and when the negative electrode material is selected from Li, M2 is selected from Li+; when the negative electrode material is selected from Na, the M2 is selected from Na+; when the negative electrode material is selected from K, M2 is selected from K+.
In some embodiments, the metal-sulfur battery further includes a separator interposed between the positive electrode material and the negative electrode material.
The metal-sulfur battery provided by the embodiment of the present disclosure can effectively inhibit the growth of metal dendrites on the negative electrode because of containing the above electrolyte, and has better battery cycle stability, rate performance, coulombic efficiency and safety performance.
In a preferred embodiment, the metal-sulfur battery is a lithium-sulfur battery.
In some embodiments, the solvent is selected from one or more of a fluorinated solvent, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene sulfite and methyl propionate.
According to the metal-sulfur battery provided by the present disclosure, the inventors have unexpectedly found that for a metal-sulfur battery using one or more of a fluorinated solvent, ethylene glycol dimethyl ether, 1,3-dioxolane, propylene sulfite, and methyl propionate as a solvent, the addition of one or more electrolyte salts represented by structural formulas 1-3 can inhibit the dissolution of sulfur in positive electrode material of the metal-sulfur battery during charging and discharging.
In some embodiments, the solvent is selected from two of a fluorinated solvent, ethylene glycol dimethyl ether and 1,3-dioxolane. Preferably, the volume ratio between them is 1:2-2:1.
In some embodiments, the fluorinated solvent comprises one or more of fluoroethylene carbonate, 3,3,3-fluoroethyl methyl carbonate and 1,1,2,2-tetrafluoroethyl-2′,2′,2′-trifluoroethyl ether.
In some embodiments, the electrolyte salt further comprises one or more of LiPF6, LiBF4, LiBOB, LiClO4, LiCF3SO3, LiDFOB, LiN(SO2CF3)2 and LiN(SO2F)2.
The present disclosure will be further explained by the following embodiments.
The embodiment is used for explaining the metal-sulfur battery and the preparation method thereof disclosed by the disclosure, and includes the following steps:
Preparation of battery: Sulfur and Ketjen Black were mixed at a mass ratio of 1:3, and heated at 155° C. for 12 hours to obtain C/S composite with sulfur content of 66%. The composite was mixed with 10 wt % PVDF-NMP solution, and the mixed slurry was coated on aluminum foil, dried in vacuum at 60° C. for 12 hours, and then cut into wafers with a diameter of 12 mm, which were used as the positive electrode of button cell. The separator was celgard 2325, and the negative electrode was lithium sheet with a diameter of 16 mm and a thickness of 0.4 mm. The amount of electrolyte was 20 ul/mgS, and the electrolyte was selected from electrolyte A.
Electrolyte A: 1M lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide was dissolved in the solvent of DOL:DME=1:1, and then 1 wt % of LiNO3 was added as additive to obtain a battery electrolyte, labeled LiHFDF.
This comparative example is used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 1 except that:
the electrolyte is selected from electrolyte B.
Electrolyte B: 1M lithium bistrifluoromethanesulfonimide was dissolved in the solvent of DOL:DME=1:1, and then 1 wt % of LiNO3 was added as additive to obtain a battery electrolyte, labeled LiTFSI.
Embodiments 2-25 are used to illustrate the metal-sulfur battery and its preparation method disclosed in the present application, they were the same as Embodiment 1 except that: the adopted positive electrode material, negative electrode material, electrolyte solvent and electrolyte additive are shown in Embodiments 2-25 of Table 1.
Comparative example 2-17 are used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, they were the same as Embodiment 1 except that:
the adopted positive electrode material, negative electrode material, electrolyte solvent and electrolyte additive are shown in Comparative example 2-17 of Table 1.
The embodiment is used to explain the metal-sulfur battery and the preparation method thereof disclosed by the disclosure, and includes the following steps:
(1) lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide (abbreviated as LiHFDF) was added into an aluminum can as lithium salt, wherein LiHFDF was purchased from TCI company, and the purity was 98%; then 3 mL solvent of DME:DOL=1:1 vol % was added into the aluminum can with a pipette, then the aluminum can was sealed and placed on a magnetic stirring table and stirred for 12 hours until lithium salt dissolved to obtain electrolyte, the magnetic stirring temperature was controlled at 30° C. for 12 h, the LiHFDF concentration was 1M, and 1% lithium nitrate was added, the whole preparation process of electrolyte was carried out in a glove box with argon atmosphere, and the water content was <1 ppm, oxygen content was <1 ppm;
(2) a 2025 button battery was prepared using the electrolyte obtained from step 1, the 2025 button battery was assembled using a copper foil with a diameter of 16 mm as counter electrode and a lithium metal sheet of 16 mm, and the separator of the 2025 button battery was PP2400, with a diameter of 19 mm.
Embodiment 27 is used to illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 26 except that:
In the first step, the solvent adopted was DMC:EC:DEC=1:1:1 vol %.
Embodiment 28 is used to illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 26 except that:
In the first step, the adopted lithium salts were LiHFDF and LiTFSI, and the concentration of LiHFDF was 0.2M, and the concentration of LiTFSI was 1M.
Comparative example 18 is used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 26 except that:
In the first step, LiTFSI was adopted as lithium salt to replace LiHFDF of Embodiment 26, and the concentration of LiTFSI was 1M.
Comparative example 19 is used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 27 except that:
In the first step, LiTFSI was adopted as lithium salt to replace LiHFDF of Embodiment 27, and the concentration of LiTFSI was 1M.
Comparative example 20 is used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 28 except that:
In the first step, the electrolyte did not include LiHFDF.
1. Test the cycle performance of the metal-sulfur batteries prepared by Embodiment 1 and Comparative example 1. The test results are shown in
It can be seen from
As can be seen from
2. Test the batteries prepared by Embodiment 20 and Comparative example 17 for 500 cycles at a current density of 0.5 C, and the results are shown in
It can be seen from
3. Test the batteries prepared by Embodiment 24 and Comparative example 17 for 500 cycles at current density of 0.5 C and 1 C, and the test results are shown in
It can be seen from
4. Test the cycle performance of the metal-sulfur batteries prepared by Embodiments 1-25 and Comparative examples 1-17, and the test results were shown in Table 1.
It can be seen from the test results in Table 1 that compared with other existing metal-sulfur batteries, the metal-sulfur battery provided by the present disclosure shows better cycle performance, can effectively inhibit the formation of metal dendrites, and reduce the capacity loss during the charging and discharging process of the battery.
5. Test the electrochemical cycle stability of the batteries prepared by Embodiments 26-28 and Comparative examples 18-20 using Xinwei battery testing system. The main test contents include the detection of coulombic efficiency, interface impedance EIS and charge-discharge curve of the lithium sheet half battery, and the test results are shown in
It can be seen from
It can be seen from
It can be seen from
Embodiments 29-36 are used to illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it was the same as Embodiment 1 except that:
the adopted positive electrode material, negative electrode material, electrolyte solvent and electrolyte additive are shown in Embodiments 29-36 of Table 2.
Comparative examples 21-24 are used to contrastively illustrate the metal-sulfur battery and its preparation method disclosed in the present application, it includes most of the steps of Embodiment 1, with the following differences:
the adopted positive electrode material, negative electrode material, electrolyte solvent and electrolyte additive are shown in Comparative example 21-24 of Table 2.
1. After the metal-sulfur batteries prepared by Embodiment 1 and Comparative example 1 were cycled for 5 times, the batteries were disassembled, and the pictures of battery pole piece and TEM and EDX of the battery materials were extracted and shown in
It can be seen by comparing the pictures in
2. The test results of Embodiment 29 and Comparative example 21 are shown in
3. The test results of Embodiment 30 and Comparative example 22 are shown in
4. The test results of Embodiment 31 and Comparative example 23 are shown in
5. The test results of Embodiment 32 and Comparative example 24 are shown in
6.
The above are only preferred embodiments of the present disclosure, and not intended to limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2019/108833 | 9/29/2019 | WO | 00 |
