Li—Sn—O—S compound, manufacturing method therefor and use thereof as electrolyte material of Li-ion batteries, and Li—Sn—O—S hybrid electrolyte

Abstract

A LiSnOS compound, a manufacturing method therefor and use thereof as an electrolyte material of Li-ion batteries, and a LiSnOS hybrid electrolyte are provided. The LiSnOS compound of the present invention is laminated SnOS embedded with lithium ions. The LiSnOS compound is represented by the formula Li.sub.3x[Li.sub.xSn.sub.1x(O,S).sub.2], where x>0. The manufacturing method for a LiSnOS compound includes the following steps of: (S1000) providing a SnOS compound; (S2000) adding a lithium source into the SnOS compound to form a LiSnOS precursor; and (S3000) performing calcination on the LiSnOS precursor in a vulcanization condition.

Claims

1. A LiSnOS compound, wherein the LiSnOS compound is laminated SnOS embedded with lithium ions; wherein the LiSnOS compound is represented by the following formula (I):
Li.sub.3x[Li.sub.xSn.sub.1-x(O,S).sub.2],Formula (I) wherein x>0.

2. The LiSnOS compound according to claim 1, wherein the LiSnOS compound is represented by Li[Li.sub.1/3Sn.sub.2/3(O,S).sub.2].

3. The LiSnOS compound according to claim 1, wherein the LiSnOS compound is represented by Li.sub.2Sn(O,S).sub.3.

4. A LiSnOS hybrid electrolyte, comprising: the LiSnOS compound according to claim 1; and a gel polymer electrolyte.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flowchart of a manufacturing method for a LiSnOS compound according to an embodiment of the present invention;

(2) FIG. 2 is a schematic structural diagram of test batteries; and

(3) FIG. 3A, FIG. 3B, FIG. 3C and FIG. 3D are diagrams of charging and discharging test results of batteries manufactured by using 0, 10%, 30% and 50% of the LiSnOS compound respectively.

DETAILED DESCRIPTION

(4) A LiSnOS compound of the present invention is laminated SnOS(SnOS) embedded with lithium ions.

(5) In an embodiment of the present invention, the LiSnOS compound is represented by the following formula (I):
Li.sub.3x[Li.sub.xSn.sub.1x(O,S).sub.2],Formula (I)

(6) where x>0.

(7) In an embodiment of the present invention, the LiSnOS compound is represented by Li[Li.sub.1/3Sn.sub.2/3(O,S).sub.2].

(8) In another embodiment of the present invention, the LiSnOS compound is represented by Li.sub.2Sn(O,S).sub.3.

(9) More specifically, when the Li-to-Sn molar ratio is 2, the lithium conductivity is the best, and a Li[Li.sub.1/3Sn.sub.2/3(O,S).sub.2] compound is formed by [Li.sub.1/3Sn.sub.2/3(O,S).sub.2] octahedral layers which are filled with Li.sup.+ layers.

(10) The LiSnOS hybrid electrolyte of the present invention contains the LiSnOS compound and the gel polymer electrolyte. In other words, the LiSnOS compound can be used as an electrolyte material.

(11) The gel polymer electrolyte contains but is not limited to polyacrylonitrile and polyvinylidene fluoride as substrates.

(12) In the schematic flowchart shown in FIG. 1, the manufacturing method for a LiSnOS compound according to an embodiment of the present invention includes the following steps.

(13) In step (S1000), a SnOS compound is provided. More specifically, a sulfur oxide (SnOS) is prepared by using an aqueous phase synthesis method. Metal cations, sulfur anions and oxygen ions are used and precipitated, and the method includes the following steps of: (1) taking and adding 5.6 g of tin (II) chloride (98%, Alfa Aesar, USA) into 500 ml of deionized water to form a white tin (II) chloride solution and stirring the solution uniformly for 30 minutes; (2) adding 1.87 g of thioacetamide (99+%, Sigma-Aldrich, USA) into the aqueous solution, stirring the solution for 30 minutes and then raising the temperature of the solution to 95 C.; (3) adding 0.3 ml of hydrazine (N.sub.2H.sub.4.H.sub.2O) (Sigma-Aldrich, USA); (4) 3 hours later after the reaction is completed at 95 C., conducting standing for precipitation; (5) conducting washing with high-purity alcohol, centrifugation and collection and finally removing a solvent through a vacuum condenser to obtain a product.

(14) In step (S2000), a lithium source is added into the SnOS compound to form a LiSnOS precursor. More specifically, in an embodiment, lithium nitrate (Sigma-Aldrich, USA) which is easier to store is used, and nitrate radical produces gas of nitrogen oxides so as to leave the powder during calcination treatment. Before the calcination treatment, the LiSnOS precursor is prepared according to the Li-to-Sn molar ratios of 1:1, 1.5:1, 1.8:1, 2:1, 2.2:1 and 3:1 separately, and materials are mixed and placed in an oven (Channel, VO-30L, Taiwan) for 12 hr to remove water molecules from the air adsorbed by LiNO.sub.3. However, in different embodiments, the lithium source including lithium such as lithium acetate, lithium carbonate, and lithium metal can be used.

(15) In step (S3000), calcination is performed on the LiSnOS precursor in a vulcanization condition. More specifically, reaction precursor powder is heated at a rate of 10 C./min under 1 atm argon, the temperature is kept at 300 C. for half an hour, and then calcination is performed under a vulcanization condition at 500 C., 550 C. or 600 C. for 3 hours for a reaction to synthesize LiSnOS compound powder. The vulcanization condition refers to a condition of providing sulfur source vapor, and the adopted sulfur source includes one or a mixture of elemental sulfur and sulfide (hydrogen sulfide, tin sulfide, stannous sulfide and copper sulfide).

(16) When the Li-to-Sn molar ratios of the LiSnOS precursor after calcination at 550 C. are 1:1, 1.5:1, 1.8:1, 2:1, 2.2:1 and 3:1, the ionic conductivities at room temperature are 2.71*10.sup.5, 3.90*10.sup.5, 1.17*10.sup.4, 1.92*10.sup.4, 1.13*10.sup.4 and 5.98*10.sup.5 Scm.sup.1, respectively.

(17) When the Li-to-Sn molar ratio of the LiSnOS precursor is 2:1, the ionic conductivity of the LiSnOS precursor obtained after calcination at 500 C., 550 C. or 600 C. at room temperature is 2.71*10.sup.5, 1.92*10.sup.4 and 1.09*10.sup.5 Scm.sup.1, respectively.

(18) Manufacturing of the Test Batteries

(19) Granular polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) (Aldrich, USA) is weighed and added into a solution, acetone is added, the temperature is raised to 60 C., and stirring is conducted to make PVDF-HFP completely dissolved; a lithium salt (LiClO.sub.4) (99.99%, Aldrich, USA) and sulfolane (99%, Aldrich, USA) are added and uniformly stirred for 2 hr, and after the solution is completely transparent and free of particles, the synthesized LiSnOS compound powder is added, where the LiSnOS compound powder is obtained from the precursor in the laboratory according to a formula that the Li-to-Sn molar ratio is 2:1 and calcination is conducted at 550 C., and the synthesized LiSnOS compound powder contains ceramic powder at the weight ratios of 10%, 30% and 50%; stirring is continued for 4 hr to completely mix the powder and the solution, and then the mixture is applied on a Teflon mold; the mold is placed in an oven at 60 C. to form a hybrid membrane after acetone is volatilized, and then the membrane is placed in a glove box, so that adsorption of moisture in the atmosphere is avoided, and the internal ions of the gel electrolyte membrane reach equilibrium for about 4 hours. Finally, the batteries adopt LiSnOS-550 (that is, the calcination temperature is 550 C.)/polymer for constituting the hybrid electrolyte, the manufactured button type solid lithium batteries adopt LiCoO.sub.2 as the positive electrode and the Li metal as the negative electrode, and the structure is shown in FIG. 2.

(20) The manufactured test batteries are subjected to a charging and discharging test and an efficiency test by cyclic voltammetry (CV), and results are shown in FIG. 3A to FIG. 3D. It can be seen from the test results that under charging and discharging loop experiments for 30 times, the two groups of test batteries of 0% LiSnOS-550 or pure gel PVDF-HFP and 30% LiSnOS-550/gel PVDF-HFP have good efficiency. As shown in FIG. 3C, the Li-ion battery prepared by using the hybrid electrolyte of 30% Li.sub.2SnOS-550/polymer has better discharging capacity of 134.6 mAh/g and coulombic efficiency of up to 95% under charging and discharging loop experiments for 30 times; as shown in FIG. 3A, the discharging capacity of the Li-ion battery prepared by using the hybrid electrolyte of 30% Li.sub.2SnOS-550/polymer is higher than that of the Li-ion battery made by pure gel PVDF-HFP, and the discharging capacity of the Li-ion battery made by pure gel PVDF-HFP is 129.6 mAh/g.

(21) From the above, it can be known that the LiSnOS electrolyte of the present invention is easy to prepare, and used chemicals have low risks. In addition, the LiSnOS electrolyte has no moisture-sensitive problems of sulfides and has the stability of oxides and better lithium conductivity than oxides, and the powder has the flame-stopping capability for polymer combustion when applied to the gel polymer.

(22) Although the above description and figures have revealed the preferred embodiments of the present invention, it is necessary to understand that various additions, many modifications and substitutions can be used in the preferred embodiments of the present invention without departing from the spirit and scope of the principle of the present invention as defined in the claims attached. One of ordinary skill in the art of the present invention should understand that modifications of various forms, structures, arrangements, ratios, materials, elements and components can be made on the present invention. Therefore, the embodiments disclosed herein are used for illustrating the present invention rather than limiting the present invention. The scope of the present invention should be defined by the claims attached, covers legal equivalents thereof and is not limited to the foregoing description.

SYMBOL DESCRIPTION

(23) 100 Negative electrode shell 200 Elastic sheet 300 Gasket/lithium sheet 400 LiSnOS compound ingot 500 Positive electrode shell S1000 Step S2000 Step S3000 Step