CN111244528A

CN111244528A - Lithium-sulfur battery cell, lithium-sulfur battery and preparation method thereof

Info

Publication number: CN111244528A
Application number: CN202010056945.0A
Authority: CN
Inventors: 彭祖铃; 王涛
Original assignee: China Aviation Lithium Battery Research Institute Co Ltd
Current assignee: China Aviation Lithium Battery Research Institute Co Ltd
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2020-06-05

Abstract

Provided is a lithium sulfur battery cell comprising: a composite negative electrode including a first electrolyte layer, a negative electrode sheet, and a second electrolyte layer laminated in this order; a positive plate; the composite negative electrode is a continuous Z-shaped folding layer, an accommodating layer is formed between every two adjacent folding layers, and the positive plate is accommodated in the accommodating layer. The battery core can ensure that each unit of the battery structure is stressed more uniformly and has better consistency, and the chemical reaction of the lithium-sulfur battery in the charging and discharging process is ensured to be carried out smoothly. The method can protect the lithium cathode and improve the yield and assembly efficiency of the battery.

Description

Lithium-sulfur battery cell, lithium-sulfur battery and preparation method thereof

Technical Field

The invention belongs to the field of chemical power sources, and particularly relates to a lithium-sulfur battery cell, a lithium-sulfur battery and a preparation method thereof.

Background

Common methods for assembling the battery core of the lithium-sulfur battery are a laminated type and a winding type. The lamination formula technology is simple relatively, the flexible operation, generally earlier with just, the negative pole piece is cut into certain size according to the design requirement mould, adopt the repeated layer upon layer of lamination machine to form, lamination formula is relatively lower to the homogeneity requirement of pole piece, can promote the pole piece uniformity through pole piece screening process again before the lamination, the disability rate is relatively lower, and the lamination formula can realize that thickness is great, the assembly of the relatively poor pole piece of pliability, but the shortcoming of lamination formula is that efficiency is relatively lower, and electric core inner structure inseparable battery internal resistance is big partially.

The winding method is that the tabs are firstly die-cut from the positive electrode and the negative electrode, then the tabs are overlapped in parallel, and the tabs are wound on a winding frame to form a flat cylindrical structure according to a certain direction. The winding type battery cell has compact structure, low internal resistance and high power density, but the method has high requirements on electrode uniformity and pole piece flexibility, the winding effect of the pole piece with larger thickness is poor, in addition, the positive pole, the negative pole and the diaphragm simultaneously wind tension adjusting rollers, the machine adjusting time is very long, and the rejection rate is also very high.

Because the positive and negative electrode volume expansion of the lithium-sulfur battery is large, and the electrode conductivity is poor, if the single lamination type assembly is adopted, the compactness and the uniformity of the battery core are difficult to ensure, the internal resistance of the battery core is large, the improvement of the electrical property is not facilitated, and the assembly efficiency is greatly reduced. However, the thickness of the positive and negative pole pieces of the lithium-sulfur battery with high energy density is generally larger, and the capacity exertion of the positive pole material is difficult to ensure if a pure winding mode is adopted.

Disclosure of Invention

In order to overcome the defects, the invention provides a lithium-sulfur battery cell and a preparation method thereof.

The invention provides a lithium-sulfur battery cell, comprising: a composite negative electrode including a first electrolyte layer, a negative electrode sheet, and a second electrolyte layer laminated in this order; a positive plate; the composite negative electrode is a continuous Z-shaped folding layer, an accommodating layer is formed between every two adjacent folding layers, and the positive plate is accommodated in the accommodating layer.

According to an embodiment of the present invention, the first electrolyte layer and the second electrolyte layer are solid or gel state electrolytes.

According to another embodiment of the present invention, the first electrolyte layer and the second electrolyte layer include a separator and a solid or gel electrolyte supported on both surfaces of the separator.

According to another embodiment of the present invention, the first electrolyte layer and/or the second electrolyte layer has an extension portion exceeding the length of the negative electrode sheet at one end in the length direction of the negative electrode sheet, and the extension portion surrounds the continuous zigzag folded layer at least once.

According to another embodiment of the present invention, the number of the accommodating layers is 2 or more.

The invention also provides a lithium-sulfur battery, which comprises the lithium-sulfur battery cell.

The invention also provides a preparation method of the lithium-sulfur battery cell, which comprises the following steps: forming a first electrolyte layer and a second electrolyte layer; sequentially laminating the first electrolyte layer, the negative electrode and the second electrolyte layer to form a composite negative electrode; and folding the composite negative electrode in a Z shape, forming accommodating layers between adjacent folding layers, arranging a positive plate between the accommodating layers, and repeating the steps to form the battery core.

According to an embodiment of the present invention, forming the first electrolyte layer and the second electrolyte layer includes: vacuum drying the high-molecular conductive polymer, the lithium salt and the inorganic ceramic component to constant weight, and mixing the three components with a solvent to form slurry; the first electrolyte layer and the second electrolyte layer are formed by the slurry.

According to another embodiment of the present invention, forming the first electrolyte layer and the second electrolyte layer includes: mixing a high-molecular conductive polymer, lithium salt 2, an inorganic ceramic component and a solvent to form slurry; the slurry is applied to a separator, and then the solvent is removed to obtain the electrolyte layer.

According to another embodiment of the present invention, the first electrolyte layer and/or the second electrolyte layer has an extension portion exceeding the length of the negative electrode tab at one end in the length direction of the negative electrode tab, and the method further includes, after the positive electrode tab is disposed, surrounding the battery cell for at least one circle with the extension portion.

In the cell preparation method, the negative lithium belt is of a continuous structure, so that only one cutting is needed, the damage of a pole piece caused by multiple cutting in the prior art is reduced, and the yield and the assembly efficiency of the battery are greatly improved.

According to the cell preparation method, the two sides of the negative electrode lithium strip are coated with the solid electrolyte in advance and then laminated, or the electrolyte layer and the negative electrode lithium strip are tightly attached and wound at the same frequency, so that the contact between the lithium strip and air in the cell processing process can be reduced, and the lithium negative electrode is protected.

Compared with the traditional pure winding mode, the semi-lamination and semi-winding mode can ensure that each unit of the battery structure is stressed more uniformly and has better consistency, and ensures that the chemical reaction in the charging and discharging processes of the lithium-sulfur battery is carried out smoothly.

Drawings

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

Fig. 1 is a schematic diagram of a lithium sulfur battery cell according to the present invention.

Fig. 2 is a schematic diagram of another lithium sulfur battery cell of the present invention.

FIG. 3 is a schematic diagram of a lithium sulfur battery cell of yet another embodiment of the present invention

Fig. 4 is a schematic diagram of a composite negative electrode forming the lithium sulfur battery cell of fig. 2.

Fig. 5 is a schematic diagram of a composite negative electrode forming the lithium sulfur battery cell of fig. 3.

Fig. 6 is a schematic diagram of a lithium sulfur battery cell of example 1.

Fig. 7 is a schematic diagram of a lithium sulfur battery cell of example 2.

Fig. 8 is a graph comparing the cycle performance of lithium sulfur battery cells prepared in examples 1,2 and comparative example 1.

Wherein the reference numerals are as follows:

1-composite negative electrode; 10-negative pole piece; 11-a first electrolyte layer; 12-a second electrolyte layer; 111, 121-extensions; 20-positive plate; 30,31, 32-reel.

Detailed Description

The present invention will be described in detail with reference to the following embodiments.

It is noted that in the drawings, the sizes of layers and regions may be exaggerated for clarity of illustration.

The terms "first" and "second," and the like, in this patent are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance. The terms "upper", "lower", "left", "right", etc. are also relative terms to each other, and should not be construed as limiting.

As shown in fig. 1, the lithium-sulfur battery cell of the present invention includes a composite negative electrode 1 and a positive electrode sheet 20, wherein the composite negative electrode 1 is a continuous zigzag folded layer, an accommodating layer is formed between adjacent folded layers, and the positive electrode sheet 20 is accommodated in the accommodating layer. The composite anode 1 includes a first electrolyte layer 11, an anode sheet 10, and a second electrolyte layer 12 laminated in this order.

The first electrolyte layer 11 and the second electrolyte layer 12 are solid or gel state electrolytes, or are solid or gel state electrolytes supported on both surfaces of the separator.

In the lithium sulfur cell structure of the present invention, the first electrolyte layer 11 and/or the second electrolyte layer 12 have

extensions

111 and 121, respectively, on one side of the negative electrode tab 10 in the length direction, which exceed the length of the negative electrode tab. Fig. 2 shows a schematic view of a cell in which both the first electrolyte layer 11 and the second electrolyte layer 12 comprise extensions. As shown in fig. 2, the folded structure consisting of the continuous negative electrode forming the zigzag folded layer and the plurality of positive electrode sheets therein surrounded by the extending

portions

111 and 121 makes the obtained cell more compact, and the extending portions preferably surround the folded structure at least once. Fig. 3 shows a schematic view of a cell in which one of the first electrolyte layer 11 and the second electrolyte layer 12 includes an extension. As shown in fig. 3, the first electrolyte layer 11 has an extended portion 111 exceeding the length of the negative electrode sheet 10 on one side in the length direction thereof, and the extended portion 111 surrounds the folded structure at least once.

The formation process of the lithium battery cell of the present invention is explained with reference to the composite negative electrode 1 shown in fig. 4 or 5. The process of forming a cell according to the present invention is explained in the case where the electrolyte layer includes the extension portion. It will be understood by those skilled in the art that the lithium sulfur cell is formed without the electrolyte layer including the extension portion in a manner similar to that described below and will not be described in detail herein. First, the composite negative electrode 1 is formed, and the process of forming the composite negative electrode 1 will be explained by taking the negative electrode sheet 10 as an example using a lithium ribbon. Vacuum drying the high molecular conductive polymer, lithium salt and inorganic ceramic components to constant weight, and dryingThe first electrolyte layer 11 and the second electrolyte layer 12 are formed by uniformly mixing the above-mentioned components with a solvent to form a slurry, and then coating both surfaces of the separator with the above-mentioned slurry. Alternatively, the slurry is applied or cast to form a thin slurry layer on the substrate, and the solvent is removed to form the electrolyte layer. The resulting electrolyte layer is then peeled off from the substrate to obtain the first electrolyte layer 11 and the second electrolyte layer 12. The high-molecular conductive polymer, the lithium salt and the ceramic components can be dried in vacuum at 100-105 ℃ to constant weight so as to remove moisture in the raw materials and prevent the moisture in the raw materials from being brought into the slurry and further into the finished battery to influence the performance of the battery. The polymer can be selected from one or more of polyethylene oxide (PEO), polymethyl methacrylate (PMMA), Polyacrylonitrile (PAN), polyurethane homopolymer or its copolymer. The lithium salt may be selected from lithium hexafluorophosphate (LiPF)₆) Lithium bistrifluoromethylsulfonyl imide (LiTFSI), lithium perchlorate (LiClO)₄) One or more of them. The inorganic ceramic may be selected from Li₇La₃Zr₂O₁₂(LLZO), Lanthanum Lithium Titanate (LLTO), Li₁₀GeP₂S₁₂(LGPS). The mass ratio of the polymer, the ceramic and the lithium salt can be specifically selected according to actual conditions. Preferred polymers are: ceramic: lithium salt 5:3:2 (mass ratio). The solvent can be selected from low-toxicity or non-toxic organic solvent. For example, the solvent is selected from one or more of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), Dimethylsulfoxide (DMSO). The concentration of the prepared slurry can be 5 wt% -80 wt% (the total mass fraction of the polymer, the ceramic and the lithium salt), and the prepared slurry can be uniformly coated on a substrate and can be coated by adopting common modes such as blade coating, roller coating or spraying. The coating thickness may be 10 to 200 μm, and then dried (for example, dried under vacuum at 60 to 100 ℃ C. to a constant weight) to obtain the first electrolyte layer 11 and the second electrolyte layer 12 after peeling from the substrate. The obtained first electrolyte layer 11, the lithium negative strip 10 and the second electrolyte layer 12 are sequentially laminated to form the composite negative electrode 1 with a sandwich structure of the first electrolyte layer 11/the negative strip 10/the second electrolyte layer 12. The electrolyte layers 11 and 12 may be formed as a solid electrolyte or a semi-solid gel. When the first electrolyte layer 11 is formed ofWhen the second electrolyte layer 12 is composed of a separator and electrolytes carried on both surfaces of the separator, the first electrolyte layer 11 and the second electrolyte layer 12 are formed as follows. The types and formulations of the polymer, ceramic and lithium salt are as described above. The solvent may be chosen to be non-reactive, low or non-toxic with respect to the membrane, such as polyvinylidene fluoride (PVDF), ethanol, acetonitrile or water. The diaphragm can be a diaphragm commonly used for lithium ion batteries, such as a polyolefin microporous diaphragm and the like, and the thickness of the diaphragm is 6-20 μm, preferably 6-10 μm. The slurry can be coated on the surface of the diaphragm by adopting a common mode of knife coating, roll coating or spray coating, and the thickness of single-side coating can be 10-200 μm, and is preferably 20-30 μm. Finally, the solvent is removed to obtain the first electrolyte layer 11 and the second electrolyte layer 12 in which the solid or gel state electrolyte is supported on the surface of the separator.

The folding process starts with the composite negative electrode 1 being folded in a zigzag manner from the flush side of the composite negative electrode 1 (i.e., the side away from the extension 111/112, i.e., the right side of the composite negative electrode 1 shown in fig. 4 and 5), the accommodating layer is formed between adjacent folding layers, the plurality of positive electrode sheets 20 are respectively and correspondingly clamped between adjacent folding layers (i.e., the positive electrode sheets 20 are accommodated in the accommodating layer), and the folding is completed until the negative electrode sheets 10 are completely folded. Specifically, the positive electrode sheet 20 is first placed on the upper surface of the composite negative electrode 1 flush with the right side of the composite negative electrode 1, and then folded 180 degrees along the left edge of the positive electrode sheet 20 into two symmetrical parts of upper and lower edges (this step is hereinafter referred to as "step one" for convenience of description). Keeping the composite negative electrode 1 and the positive electrode sheet 20 to be tightly attached to each other, and obtaining a folding structure containing 1 positive electrode sheet 20 and 2 negative electrode sheets 10. And continuously placing the other positive plate 20 on the upper surface of the folded composite negative electrode 1 and keeping the two positive plates close to each other, keeping the second positive plate 20 completely aligned with the first positive plate 20, aligning the composite negative electrode 1 along the right edge of the second positive plate 20 again, folding the two positive plates by 180 degrees, keeping the lower surface of each folded composite negative electrode 1 closely attached to the upper surface of each positive plate 20, and obtaining a folded structure containing 2 positive plates 20 and 3 negative plates 10 (for convenience of description, the step is hereinafter referred to as "step two"). And then, when placing the odd-numbered positive plate 20, stacking according to the first step, and when placing the even-numbered positive plate 20, stacking according to the second step. And after the last positive plate 20 is laminated, continuously folding the composite negative electrode 1 along the corresponding edge of the positive plate 20 in half, completely covering the positive plate 20, aligning the tail end of the negative plate 10 with the corresponding side of the positive plate, and winding the folding structure 1 by using the extension parts, namely the

extension parts

111 and 121 in fig. 4 or the extension part 121 in fig. 5, for at least one circle to firmly wrap the folding structure, so as to finally obtain the semi-laminated semi-winding lithium-sulfur battery cell containing a plurality of positive plates 20. The cell in which the composite negative electrode 1 shown in fig. 4 is formed in the above manner is shown in fig. 2, and the cell in which the composite negative electrode 1 shown in fig. 5 is formed in the above manner is shown in fig. 3.

In the above manner, the solid electrolyte layers 11 and 12 are formed in advance with the negative electrode sheet 10 into the composite negative electrode 1, and a cell is formed by folding the composite negative electrode 1. Alternatively, the composite negative electrode is not formed in advance, but the first electrolyte layer 11, the negative electrode sheet 10 and the second electrolyte layer 12 are independent from each other, and the first electrolyte layer 11, the negative electrode sheet 10 and the second electrolyte layer 12 are wound at the same frequency in the folding process to form the composite negative electrode 1. Since the first electrolyte layer 11 and the second electrolyte layer 12 are each independently subjected to a tensile force in the assembly process, a certain tensile strength is required for the electrolyte layers 11 and 12. In order to improve the tensile strength of the electrolyte layers 11 and 12, a solid electrolyte may be formed on the surface of the separator to increase the tensile strength.

Specifically, first, a conductive polymer, an inorganic ceramic, a lithium salt, and a solvent are uniformly mixed to form a slurry. Wherein the polymer, inorganic ceramic and lithium salt may be the same as those mentioned above. The solvent may be chosen to be non-reactive, low or non-toxic with respect to the membrane, such as polyvinylidene fluoride (PVDF), ethanol, acetonitrile or water. The diaphragm can be a diaphragm commonly used for lithium ion batteries, such as a polyolefin microporous diaphragm and the like, and the thickness of the diaphragm is 6-20 μm, preferably 6-10 μm. The slurry can be coated on the surface of the separator by a conventional manner such as knife coating, roll coating or spray coating, and the coating thickness can be 10-200 μm, preferably 20-30 μm. Finally, the solvent is removed to obtain the first electrolyte layer 11 and the second electrolyte layer 12 in which the solid or gel state electrolyte is supported on the surface of the separator.

In the folding process, referring to fig. 6 and 7, first, the first electrolyte layer 11/the metallic lithium tape (negative plate 10)/the second electrolyte layer 12 are horizontally placed at the same time, the negative plate 10 is located between the solid electrolyte layers 11 and 12, the

reels

30,31 and 32 respectively drive the negative plate 10, the first electrolyte layer 11 and the second electrolyte layer 12 in the assembling process, the negative plate 10 and the

solid electrolytes

11 and 12 are always tightly attached, and the composite negative electrode 1 is formed by winding with the same frequency. Then, the positive electrode sheet 20 is placed on the upper surface of the composite negative electrode 1 of the accommodating layer formed between the adjacent folded layers in a flush manner with the right side of the composite negative electrode 1, and the first electrolyte layer 11/the negative electrode sheet 10/the second electrolyte layer 12 are folded into two symmetrical parts along the left edge of the first positive electrode sheet 20 by 180 degrees (for convenience of description, this step is hereinafter referred to as "step one"). The first electrolyte layer 11/the negative electrode plate 10/the second electrolyte layer 12 and the positive electrode plate 20 are kept in close contact with each other, and a folded structure containing 1 positive electrode plate 20 and two negative electrode plates 10 is obtained. The second positive plate 20 is placed on the upper surface of the folded upper-layer composite negative electrode 1 and kept close to the upper surface, the second positive plate 20 is kept completely aligned with the first positive plate 20, the first electrolyte layer 11/the negative plate 10/the second electrolyte layer 12 are aligned along the right edge of the second positive plate 20 again, 180-degree folding is carried out, the lower surface of each folded first electrolyte layer 11/the negative plate 10/the second electrolyte layer 12 is kept close to the upper surface of each positive plate 20, and a folded structure containing 2 positive plates 20 and 3 negative plates 10 is obtained (for convenience of description, the step is hereinafter referred to as "step two"). And then, when placing the odd-numbered positive plate 20, stacking according to the first step, and when placing the even-numbered positive plate 20, stacking according to the second step. After the last positive plate 20 is laminated, the first electrolyte layer 11/the negative plate 10/the second electrolyte layer 12 are folded in half along the edge of the positive plate 20 to completely cover the positive plate 20. As shown in fig. 6, the lithium metal negative electrode sheet 10 is cut along the right edge of the positive electrode sheet 20, the uncut first electrolyte layer 11 forms an extension portion 111, the uncut second electrolyte layer 12 forms an extension portion 121, and the folded structure is wound at least one circle by the

extension portions

111 and 121 to firmly wrap the folded structure, so as to obtain the half-lamination half-winding lithium-sulfur battery cell containing the plurality of positive electrode sheets 20 as shown in fig. 2. Or as shown in fig. 7, cutting off the first electrolyte layer 11 and the lithium metal negative electrode sheet 10 along the right edge of the positive electrode sheet 20, forming an extension portion 121 on the uncut second electrolyte layer 12, and winding the folded structure at least one circle by using the extension portion 121 to firmly wrap the folded structure, thereby finally obtaining the semi-laminated semi-wound lithium-sulfur battery cell containing the plurality of positive electrode sheets 20 as shown in fig. 3.

The battery cell is formed by the semi-lamination and semi-winding mode, and the negative pole pieces are in a continuous structure, so that the battery cell can be suitable for any number of positive pole pieces, namely more than 2 positive pole pieces are suitable for the battery cell structure.

Example 1

Preparation of positive electrode sheet 20

Uniformly mixing elemental sulfur and porous carbon in a mass ratio of 4:6, and then preserving heat at 155 ℃ for 2h to obtain the C/S compound. Then preparing anode material slurry by using the C/S compound, the acetylene black and the PVDF according to the mass ratio of 8:1:1, then coating the anode material slurry on two sides of the aluminum-coated foil, wherein the thickness of a single-side slurry layer is 65 mu m, and cutting the slurry into a regular shape after drying to prepare the anode plate 20.

Preparation of composite negative electrode 1

The PEO, the LLTO and the LiTFSI are dried in vacuum at the temperature of 100-105 ℃ to constant weight, and then evenly mixed with acetonitrile according to the mass ratio of 5:3:2 to form slurry. The resulting slurry was uniformly applied to a 9 μm PE separator by blade coating, and the thickness was 10 μm on one side. And (3) drying the mixture in vacuum at the temperature of 60-100 ℃ to constant weight to obtain the composite negative electrode 1 of the first electrolyte layer 11/the metallic lithium negative electrode sheet 10/the second electrolyte layer 12 shown in the figure 4.

Assembled into an electrical core

And assembling the composite negative electrode 1 and the 20 positive electrode sheets 20 into a battery core. Firstly, the composite negative electrode 1 is folded in a zigzag manner, the positive electrode sheets 20 are respectively and correspondingly clamped between adjacent folding layers (accommodated in the accommodating layers), and after the negative electrode sheets 10 are completely folded, the folding structure is wound by the extending

parts

111 and 121 for one circle to obtain the battery core with the structure shown in fig. 2.

Example 2

Preparation of positive electrode sheet 20

The positive electrode sheet 20 was formed in the same manner as in example 1.

Preparation of electrolyte layers 11 and 12

The PEO, the LLTO and the LiTFSI are dried in vacuum at the temperature of 100-105 ℃ to constant weight, and then evenly mixed with acetonitrile according to the mass ratio of 5:3:2 to form slurry. The resulting slurry was uniformly coated onto a 6 μm thick PE separator with a blade coating thickness of 10 μm. The solvent was removed to obtain first electrolyte layer 11 and second electrolyte layer 12 in which solid electrolytes were supported on the separator.

Assembled into an electrical core

Assembled into a cell in the manner shown in fig. 5. Namely, the negative electrode plate 10 and the

solid electrolytes

11 and 12 are always kept in close fit, and the composite negative electrode 1 is formed by winding at the same frequency. Folding compound negative pole 1 according to the zigzag, simultaneously with 20 positive plates 20 respectively corresponding centre gripping between adjacent folded layers, fold to the whole folding back that accomplishes of negative pole piece 10, cut off first electrolyte layer 11 and metal lithium negative pole piece 10 along positive plate 20 right side edge, second electrolyte layer 12 that does not cut off forms extension 121, utilize extension 121 to twine the beta structure at least half the round and half firmly wraps up the beta structure, finally obtain the semi-lamination half-winding formula lithium sulphur battery electric core that contains multi-disc positive plate 20 as shown in figure 7.

Comparative example 1

The positive electrode sheet prepared in the manner of example 1, a 9 μm PE separator, and a lithium sheet negative electrode were sequentially stacked to form a laminate structure, and then folded in a zigzag manner to form a cell structure having the same size as in examples 1-2.

Performance detection

The battery cell prepared in the embodiment 1-2 is rolled under the pressure of 0.001-0.1MPa and then is kept stand for 48 hours at the temperature of 45 ℃. The electrochemical performance test is carried out by adopting a 5V,2Ah blue electro-chemical tester at the temperature of 45 ℃, the test voltage range is 2.8-1.0V, and the test current is 0.01C-1C, preferably 0.1C.

After the battery core prepared in comparative example 1 is assembled, vacuum drying is carried out for 48 hours at the temperature of 60 ℃. And injecting the electrolyte, wherein the injection ratio is E/S (equal to 3: 1). The electrolyte comprises the following components: 1mol of LiTFSI, DOL/DMF ═ 1:1 (volume ratio), 2 wt% lithium nitrate. Electrochemical performance was also measured using a blue electrochemical tester in the same manner as in examples 1-2.

Fig. 7 shows a graph comparing the cycle performance of the cell structures of examples 1-2 and comparative example 1. It can be seen from the figure that the cycle performance of the battery is significantly improved compared with the battery core formed by the existing lamination mode.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A lithium sulfur battery cell, comprising:

a composite negative electrode including a first electrolyte layer, a negative electrode sheet, and a second electrolyte layer laminated in this order;

a positive plate;

the composite negative electrode is a continuous Z-shaped folding layer, an accommodating layer is formed between every two adjacent folding layers, and the positive plate is accommodated in the accommodating layer.

2. The lithium sulfur battery cell of claim 1, wherein the first electrolyte layer and the second electrolyte layer are solid or gel state electrolytes.

3. The lithium sulfur battery cell of claim 1, wherein the first electrolyte layer and the second electrolyte layer comprise a separator and a solid or gel state electrolyte supported on both surfaces of the separator.

4. The lithium sulfur battery cell of claim 1, wherein the first electrolyte layer and/or the second electrolyte layer has an extension at one end of the negative electrode sheet in the length direction that exceeds the length of the negative electrode sheet, the extension surrounding the continuous zigzag folded layer for at least one revolution.

5. The lithium sulfur battery cell of claim 1, wherein the containment layer is 2 or more.

6. A lithium sulfur battery comprising the lithium sulfur battery cell of any of claims 1-5.

7. A method of making a lithium sulfur battery cell, comprising:

forming a first electrolyte layer and a second electrolyte layer; sequentially laminating the first electrolyte layer, the negative electrode and the second electrolyte layer to form a composite negative electrode;

and folding the composite negative electrode in a Z shape, forming accommodating layers between adjacent folding layers, arranging a positive plate between the accommodating layers, and repeating the steps to form the battery core.

8. The method of making a lithium sulfur battery cell of claim 7, wherein forming the first electrolyte layer and the second electrolyte layer comprises:

vacuum drying the high-molecular conductive polymer, the lithium salt and the inorganic ceramic component to constant weight, and mixing the three components with a solvent to form slurry;

the first electrolyte layer and the second electrolyte layer are formed by the slurry.

9. The method of making a lithium sulfur battery cell of claim 7, wherein forming the first electrolyte layer and the second electrolyte layer comprises:

mixing a high-molecular conductive polymer, a lithium salt, an inorganic ceramic component and a solvent to form slurry;

the slurry is applied to a separator, and then the solvent is removed to obtain the electrolyte layer.

10. The method of making a lithium sulfur battery cell of claim 7, wherein the first electrolyte layer and/or the second electrolyte layer has an extension at one end of the negative electrode tab in the length direction that exceeds the length of the negative electrode tab, the method further comprising, after the positive electrode tab is placed, surrounding the cell for at least one revolution with the extension.