CN116315055A - Solid-state battery cell, preparation method thereof and solid-state lithium ion battery - Google Patents

Abstract

The invention provides a solid-state battery cell, a preparation method thereof and a solid-state lithium ion battery, wherein the solid-state battery cell comprises a positive electrode layer and a solid electrolyte layer which are arranged in a laminated manner; the solid electrolyte layer includes a first sulfide electrolyte; the positive electrode layer contains a positive electrode active material and a second electrolyte; the first sulfide electrolyte has the molecular formula of Li _a1 M _b1 PS _c1 X _d1 The molecular formula of the second sulfide electrolyte is Li _a2 M _b2 PS _c2 X _d2 Wherein b1: b2 is 1:1 to 1:2, wherein X is selected from halogen, and M is selected from at least one of Na and K. The battery core can improve the cycle performance and the capacity of the solid-state lithium ion battery by improving the interface compatibility of the positive electrode layer and the solid electrolyte layer and improving the transmission rate of lithium ionsRetention rate.

Description

Solid-state battery cell, preparation method thereof and solid-state lithium ion battery

Technical Field

The invention belongs to the field of solid-state batteries, and particularly relates to a solid-state battery cell, a preparation method thereof and a solid-state lithium ion battery.

Background

A solid-state lithium battery is a lithium ion battery that uses a solid electrolyte instead of a liquid electrolyte. Because of the fixity of the solid electrolyte, the solid lithium battery has the advantages of high energy density, high safety and the like, and is widely applied to the fields of new energy automobiles and the like. The interfacial contact between the electrolyte layer and the positive electrode layer directly affects the overall performance of the solid-state lithium battery. In the cycle of the battery, the interface contact is deteriorated and the cycle performance of the battery is deteriorated due to the volume expansion of the positive electrode active material particles during charge and discharge. The main means for improving the interface contact between the positive electrode layer and the electrolyte layer at the present stage is to apply external pressure to the positive electrode layer, such as cold pressing, hot pressing, rolling and the like. However, because the positive electrode layer and the electrolyte layer are made of different materials, a large potential difference exists between the positive electrode layer and the electrolyte layer, so that the interface impedance is increased, and finally, the cycle performance of the solid-state lithium battery is poor and the capacity retention rate is not high.

Disclosure of Invention

The invention provides a solid-state battery core, which improves the cycle performance and the capacity retention rate of a solid-state lithium ion battery by improving the interface compatibility of a positive electrode layer and a solid electrolyte layer and improving the transmission rate of lithium ions.

The invention provides a preparation method of a solid-state battery cell, which can prepare the solid-state battery cell and has the advantages of simple preparation method, low cost and the like.

The invention provides a solid-state lithium ion battery which has excellent cycle performance, capacity retention rate and the like due to the inclusion of the solid-state battery cell.

In a first aspect of the present invention, there is provided a solid-state battery cell including a positive electrode layer and a solid-state electrolyte layer stacked;

the solid electrolyte layer includes a first sulfide electrolyte; the positive electrode layer contains a positive electrode active material and a second electrolyte;

the first sulfide electrolyte has the molecular formula of Li _a1 M _b1 PS _c1 X _d1 The molecular formula of the second sulfide electrolyte is Li _a2 M _b2 PS _c2 X _d2 Wherein b1: b2 is 1:1 to 1:2, X is selected from halogen, M is selected from at least one of Na and K.

The solid-state battery cell is characterized in that a1 is 5.5-6.5, b1 is 0.001-0.1, c1 is 4.5-5.5, and d1 is 0.9-1.6; and/or the number of the groups of groups,

a2 is 5.5-6.5, b2 is 0.001-0.1, c2 is 4.5-5.5, d2 is 0.9-1.6.

The solid-state battery cell as described above, wherein a mass ratio of the sum of the mass of the positive electrode active material and the second sulfide electrolyte to the mass of the first sulfide electrolyte is (1 to 6): 30.

the solid-state battery cell as described above, wherein in the positive electrode layer, the mass ratio of the positive electrode active material to the second sulfide electrolyte is (6:4) to (9.5:0.5).

The solid-state battery cell as described above, wherein the molecular formula of the positive electrode active material is Li _x Na _y Ni _e Co _f Mn _g O _z ，

Wherein e+f+g=1, e is more than or equal to 0.1 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 0.3, and g is more than or equal to 0.5 and less than or equal to 0.9; x+y is more than 1 and less than or equal to 1.5, x is more than or equal to 1 and less than or equal to 1.5, y is more than 0 and less than or equal to 0.5; z is more than or equal to 2 and less than or equal to 2.5.

The solid-state battery cell further comprises a negative electrode layer, and the positive electrode layer, the solid-state electrolyte layer and the negative electrode layer are sequentially stacked.

The solid-state battery cell as described above, wherein the material of the negative electrode layer comprises indium or a lithium-indium alloy.

In a second aspect of the present invention, there is provided a method for preparing a solid-state battery cell as described above, comprising the steps of:

pressing a raw material at least comprising a first sulfide electrolyte to obtain a solid electrolyte layer;

placing a raw material at least comprising a positive electrode active material and a second electrolyte on one side of the solid electrolyte layer to obtain an intermediate;

and performing compression molding treatment on the intermediate to obtain the solid-state battery cell.

The preparation method comprises the following steps before the compression molding treatment: the material of the negative electrode layer is placed on the other side of the solid electrolyte layer.

A production method as described above, wherein the first sulfide electrolyte and the second sulfide electrolyte are each independently produced by a method comprising: sintering a raw material comprising lithium sulfide, phosphorus sulfide, a halogen compound and an alkali metal compound;

wherein the alkali metal compound is selected from a compound of Na and/or a compound of K; the sintering treatment temperature is 510-560 ℃ and the sintering treatment time is 3-8 h.

In a third aspect of the invention, a solid state lithium ion battery is provided, comprising a solid state cell as described above.

The implementation of the invention has at least the following beneficial effects:

in the solid-state battery cell, the lithium ion transmission rate of the first sulfide electrolyte and the second sulfide electrolyte is larger than that of the positive electrode active material, the transmission rate of lithium ions is improved by introducing the first sulfide electrolyte and the second sulfide electrolyte, and meanwhile, the first sulfide electrolyte and the second sulfide electrolyte have the same element composition, so that the interfacial compatibility between the positive electrode layer and the solid-state electrolyte layer is improved. Therefore, the invention improves the cycle performance and the capacity retention rate of the solid lithium ion battery by improving the interface compatibility of the positive electrode layer and the solid electrolyte layer and the transmission rate of lithium ions.

Drawings

FIG. 1 is an SEM image of a first magnification of the sulfide electrolyte of example 1 according to the invention;

fig. 2 is an SEM image of the sulfide electrolyte of example 1 in the present invention at a second magnification.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In a first aspect of the present invention, there is provided a solid-state battery cell including a positive electrode layer and a solid-state electrolyte layer stacked; the solid electrolyte layer comprises a first sulfide electrolyte; the positive electrode layer contains a positive electrode active material and a second electrolyte; the first sulfide electrolyte has the formula of Li _a1 M _b1 PS _c1 X _d1 The molecular formula of the second electrolyte is Li _a2 M _b2 PS _c2 X _d2 Wherein b1: b2 is 1:1 to 1:2, X is selected from halogen, M is selected from at least one of Na and K.

The solid-state battery cell of the invention comprises a positive electrode layer and a solid-state electrolyte layer. Wherein the positive electrode layer is used for providing an active material, such as a lithium-containing compound. The solid electrolyte layer is capable of conducting lithium ions, especially when the solid state battery cell is a battery constituent unit, between the positive electrode layer and the negative electrode layer.

The present invention is not limited to the manner of disposing the positive electrode layer, as long as the positive electrode layer and the solid electrolyte layer are ensured to be disposed in a stacked manner. For example, the positive electrode layer may be provided on one side of the solid electrolyte layer by being stacked alone, or may be adhered to one side of the solid electrolyte layer. At this time, the positive electrode layer of the present invention has an interface in contact with the solid electrolyte layer.

The solid electrolyte layer comprises a first sulfide electrolyte, the positive electrode layer comprises a positive electrode active material, a second sulfide electrolyte, wherein the first sulfideThe molecular formula of the electrolyte is Li _a1 M _b1 PS _c1 X _d1 The molecular formula of the second electrolyte is Li _a2 M _b2 PS _c2 X _d2 . The first sulfide electrolyte has the same elemental composition as the second sulfide electrolyte. The positive electrode layer and the solid electrolyte layer contain sulfide electrolyte with the same element composition, so that the positive electrode layer and the solid electrolyte layer have good interface compatibility.

Wherein M is selected from at least one of Na and K, and X is selected from halogen, such as fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and the like. b1: b2 is 1:1 to 1:2, for example 1:1. and 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2 or any two thereof.

According to the molecular formulas of the first sulfide electrolyte and the second sulfide electrolyte, compared with the conventional sulfide electrolyte only containing Li, P, S, X, the first sulfide electrolyte and the second sulfide electrolyte adopt Na and K to replace part of Li sites in the conventional sulfide electrolyte, because of Na ⁺ 、K ⁺ The ionic radius of the lithium ion battery is larger than Li, the tortuosity of lithium ion transmission is reduced, the path of lithium ion transmission is increased, and the lithium ion transmission rate is improved. Wherein, the higher the content of sodium and potassium, the higher the lithium ion transmission rate.

In addition to the positive electrode active material in the positive electrode layer being used to provide an active material, the second sulfide electrolyte can utilize the remaining Li sites as an active material release capacity, at which time the positive electrode active material and the second sulfide electrolyte together provide an active material release capacity, and in addition, the second sulfide electrolyte can also efficiently conduct lithium ions, at which time the second sulfide electrolyte together with the first sulfide electrolyte can increase the rate of lithium ion transport. Therefore, the solid-state battery cell with the structure can ensure that the positive electrode layer and the solid-state electrolyte layer have good interface compatibility, and can enable the lithium ions to be smoothly inserted and extracted in the positive electrode layer, so that the transmission rate of the lithium ions is improved.

Further, when 1:1 < b1 is satisfied: and b2 is less than or equal to 1:2, so that the M content of the second sulfide electrolyte is greater than that of the first sulfide electrolyte, the lithium ion transmission rate of the positive electrode layer is further improved, the lithium ion transmission rates of the positive electrode layer and the solid electrolyte layer are matched, and the cycle performance and the capacity retention rate of the battery are further improved.

According to the research of the invention, the solid-state battery cell is applied to a solid-state lithium ion battery, and the solid-state lithium ion battery has excellent cycle performance, capacity retention rate and the like. On one hand, sulfide electrolytes with the same element composition are respectively contained in the positive electrode layer and the solid electrolyte layer, so that the positive electrode layer and the solid electrolyte layer have good interface compatibility, the interface impedance of the positive electrode layer and the solid electrolyte layer is greatly reduced, and the cycle performance and the capacity retention rate of the solid lithium ion battery are improved; on the other hand, the first sulfide electrolyte and the second sulfide electrolyte adopt Na and K to replace part of Li sites in the conventional sulfide electrolyte, so that the first sulfide electrolyte and the second sulfide electrolyte have higher ion conductivity and are characterized by Na ⁺ 、K ⁺ The ionic radius of the electrolyte is larger than Li, the tortuosity of lithium ion transmission is reduced, and the lithium ion transmission path is increased, so that the lithium ion transmission rate is improved, the problem of interface contact deterioration caused by volume expansion of the positive electrode layer in the circulating process is avoided, and in addition, the second electrolyte can also be used as the release capacity of an active material. Therefore, the solid-state battery cell provided by the invention can improve the cycle performance and the capacity retention rate of the solid-state lithium ion battery by improving the interface compatibility of the positive electrode layer and the solid electrolyte layer, improving the ionic conductivity of sulfide electrolyte, improving the transmission rate of lithium ions, improving the capacity and the like.

In one embodiment, a1 is 5.5 to 6.5, b1 is 0.001 to 0.1, c1 is 4.5 to 5.5, and d1 is 0.9 to 1.6; and/or a2 is 5.5 to 6.5, b2 is 0.001 to 0.1, c2 is 4.5 to 5.5, and d2 is 0.9 to 1.6. By defining the element content in the first sulfide electrolyte and the second sulfide electrolyte, the structural stability of the first sulfide electrolyte and the second sulfide electrolyte is advantageously improved, thereby further improving the interfacial compatibility between the positive electrode layer and the solid electrolyte layer and the lithium ion transport rate.

The mass proportion of the active ingredients in the positive electrode layer and the solid electrolyte layer is reasonably adjusted, so that the cycling performance and the capacity retention rate of the solid lithium ion battery are further improved. In some embodiments, the mass ratio of the sum of the masses of the positive electrode active material, the second sulfide electrolyte to the first sulfide electrolyte is (1-6): 30. when the solid electrolyte layer contains only the first sulfide electrolyte and the positive electrode layer contains only the positive electrode active material and the second sulfide electrolyte, the mass ratio of the positive electrode layer to the solid electrolyte layer is (1 to 6): 30, for example 1: 30. 2: 30. 3: 30. 4: 30. 5: 30. 6:30 or any two thereof.

The mass ratio of the positive electrode active material and the second electrolyte in the positive electrode layer is not limited, so long as the positive electrode layer is ensured to contain the positive electrode active material and the second electrolyte. The capacity and lithium ion transfer rate are further improved by adjusting the positive electrode active material and the second electrolyte. In some embodiments, the mass ratio of positive electrode active material to second sulfide electrolyte in the positive electrode layer is (6:4) - (9.5:0.5), for example 6: 4. 7: 3. 8: 2. 9: 1. 9.5:0.5 or any two thereof.

The present invention is not limited to the specific molecular formula of the positive electrode active material, and may be a positive electrode active material conventional in the art. In some embodiments, the positive electrode active material has the formula Li _x Na _y Ni _e Co _f Mn _g O _z ，

Wherein e+f+g=1, e is more than or equal to 0.1 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 0.3, and g is more than or equal to 0.5 and less than or equal to 0.9; x+y is more than 1 and less than or equal to 1.5, x is more than or equal to 1 and less than or equal to 1.5, y is more than 0 and less than or equal to 0.5; z is more than or equal to 2 and less than or equal to 2.5. The inventors have studied that the use of the positive electrode active material of this molecular formula in combination with the above second electrolyte can further improve the capacity and cycle performance of the battery.

The solid-state battery cell also comprises a negative electrode layer, wherein the positive electrode layer, the solid-state electrolyte layer and the negative electrode layer are sequentially laminated. The solid electrolyte layer has two opposite sides in the lamination direction, the positive electrode layer is positioned on one side of the solid electrolyte layer, and the solid electrolyte layer is positioned on the other side of the solid electrolyte layer. The invention is not limited to the arrangement mode of the anode layer, and the anode layer, the solid electrolyte layer and the anode layer are ensured to be sequentially laminated. For example, the negative electrode layer may be provided separately on the other side of the solid electrolyte layer, or may be bonded to the other side of the solid electrolyte layer.

The invention is not limited to a particular material of the negative electrode layer, for example, in some embodiments, the material of the negative electrode layer includes indium or a lithium-indium alloy. The materials of these negative electrode layers have higher lithium storage capacities than conventional graphite negative electrodes, and thus use in solid state lithium ion batteries enables higher energy densities.

The negative electrode layer may be composed of an indium foil alone or a laminate of a lithium foil and an indium foil. When the negative electrode layer is formed by stacking lithium foil and indium foil, the indium foil is attached to the other side of the solid electrolyte layer, and the lithium foil is positioned on one side of the indium foil away from the solid electrolyte layer.

The solid-state battery cell can also comprise a negative electrode current collector, wherein the negative electrode current collector is positioned on the surface of the negative electrode layer far away from the solid-state electrolyte layer, and the negative electrode current collector plays a role in supporting the negative electrode layer. Thus, the electrochemical performance of the solid-state lithium ion battery is ensured, and the structural stability of the battery is improved. The negative electrode current collector may be copper foil or the like.

The thickness of the positive electrode layer, the solid electrolyte layer and the negative electrode layer in the solid-state battery cell is not limited, and can be specifically adjusted according to actual needs.

The invention also comprises a tab, wherein the tab is used for being connected with an external circuit. Specifically, a negative electrode tab may be led out from one side of the negative electrode layer, and a positive electrode tab may be led out from one side of the positive electrode layer.

In a second aspect of the present invention, there is provided a method for preparing a solid-state battery cell according to the first aspect, including the steps of:

pressing a raw material at least comprising a first sulfide electrolyte to obtain a solid electrolyte layer;

placing a raw material at least comprising a positive electrode active material and a second electrolyte on one side of a solid electrolyte layer to obtain an intermediate;

and performing compression molding treatment on the intermediate to obtain the solid-state battery cell.

The specific processes of the pressing treatment and the compression molding treatment are not limited excessively, and the raw materials can form a positive electrode layer and a solid electrolyte layer which are stacked after the pressing treatment and the compression molding treatment.

The press forming treatment is preceded by the following steps: and placing the material of the negative electrode layer on the other side of the solid electrolyte layer, wherein at the moment, the raw materials at least comprising the positive electrode active material and the second electrolyte are positioned on one side of the solid electrolyte layer, and carrying out integrated pressing treatment on the materials to obtain a solid-state battery cell, so that the positive electrode layer, the solid-state electrolyte layer and the negative electrode layer are sequentially laminated in the solid-state battery cell.

The specific materials of the negative electrode layer are not limited too much. In one embodiment, an indium foil is attached to the other side of the solid electrolyte layer, a lithium foil is placed on the side, away from the solid electrolyte layer, of the indium foil, a negative electrode current collector is placed on the side, away from the solid electrolyte layer, of the lithium foil, and then integrated compression molding treatment is performed, wherein the negative electrode layer comprises a laminated lithium foil and indium foil, and the positive electrode layer, the solid electrolyte layer, the negative electrode layer and the negative electrode current collector are sequentially laminated.

The present invention is not limited to the preparation process of the first sulfide electrolyte and the second sulfide electrolyte, and a doping method conventional in the art may be used. For example, a compound containing the above elements may be mixed as a raw material and directly added for synthesis, or a conventional sulfide electrolyte may be synthesized and then subjected to doping or coating treatment. In some embodiments, the first sulfide electrolyte, the second sulfide electrolyte are each independently prepared by a method comprising: sintering a raw material comprising lithium sulfide, phosphorus sulfide, a halogen compound and an alkali metal compound, wherein the alkali metal compound is selected from a compound of Na and/or a compound of K; the sintering treatment temperature is 510-560 ℃ and the sintering treatment time is 3-8 h. Preferably at a sintering temperature of 530℃for a period of 6 hours.

In a third aspect of the present invention, a solid-state lithium ion battery is provided, which includes the solid-state battery cell of the first aspect or the solid-state battery cell manufactured by the manufacturing method provided by the second aspect. The solid-state battery cell can be directly used as a solid-state lithium ion battery after being assembled, and the quality of the solid-state battery cell directly determines the quality of the solid-state lithium ion battery. Because the battery provided by the invention adopts the solid-state battery core, the solid-state lithium ion battery has excellent performances in the aspects of cycle performance, capacity retention rate and the like.

The invention is further illustrated by the following examples.

Example 1

Na is mixed with ₂ S、Li ₂ S、P ₂ S ₅ Carrying out high-energy ball milling mixing treatment on LiCl according to the mol ratio of 0.1:4.9:1:2 to obtain a mixture; wherein the ball milling rotating speed is 450r, the ball milling time is 6h, the intermittent ball milling is carried out, the mixture is sintered in argon atmosphere, and the sulfide electrolyte Li is obtained after crushing _5.9 Na _0.1 PS ₅ Cl, the sulfide electrolyte being used as a first sulfide electrolyte and a second sulfide electrolyte; wherein the sintering treatment temperature is 530 ℃, the sintering treatment time is 6 hours, and the heating rate is 5 ℃/min;

cold-press molding 0.15g of the first sulfide electrolyte in a battery mold to obtain a solid electrolyte layer; 0.01g of positive electrode layer material was placed on one side of the electrolyte layer (positive electrode layer material comprising positive electrode active material, second electrolyte in a mass ratio of 8:2), the positive electrode active material having the formula of Li _1.2 Na _0.05 Ni _0.325 Co _0.1 Mn _0.575 O _2.25 ；

And (3) making the indium foil close to the other side of the solid electrolyte layer, placing the lithium foil on one side of the indium foil far away from the solid electrolyte layer, placing the negative electrode current collector on one side of the lithium foil far away from the solid electrolyte layer, and then performing integrated compression molding treatment, wherein the pressure maintaining time is more than or equal to 20min, so as to obtain the solid battery core.

Example 2

Substantially the same as the production method of example 1, except that the first sulfide electrolyte was produced by the following method: na is mixed with ₂ S、Li ₂ S、P ₂ S ₅ Carrying out high-energy ball milling mixing treatment on LiCl according to the mol ratio of 0.05:4.95:1:2 to obtain a mixture; wherein the ball milling rotating speed is 450r, the ball milling time is 6h, the intermittent ball milling is carried out, the mixture is sintered in argon atmosphere, and the sulfide electrolyte Li is obtained after crushing _5.95 Na _0.05 PS ₅ Cl, the sulfide electrolyte being used as a first sulfide electrolyte and a second sulfide electrolyte; wherein the sintering treatment temperature is 535 ℃, the sintering treatment time is 6 hours, and the heating rate is 5 ℃/min;

the sulfide electrolyte of this example was used as the first sulfide electrolyte, the sulfide electrolyte of example 1 was used as the second sulfide electrolyte, and the solid-state battery cell was prepared under the same conditions.

Example 3

The preparation method of the sulfide electrolyte of this example was substantially identical to that of example 1, except that the following sulfide electrolyte was used as the first sulfide electrolyte and the second sulfide electrolyte, and the specific preparation method of the sulfide electrolyte of this example was as follows: will K ₂ S、Li ₂ S、P ₂ S ₅ Carrying out high-energy ball milling mixing treatment on LiCl according to the mol ratio of 0.03:4.97:1:2 to obtain a mixture; wherein the ball milling rotating speed is 450r, the ball milling time is 6h, the intermittent ball milling is carried out, the mixture is sintered in argon atmosphere, and the sulfide electrolyte Li is obtained after crushing _5.97 K _0.03 PS ₅ Cl; wherein the sintering treatment temperature is 525 ℃, the sintering treatment time is 6 hours, and the heating rate is 5 ℃/min;

the sulfide electrolyte of this example was used as the first electrolyte and the second electrolyte, and the other conditions were unchanged, to prepare a solid-state battery cell.

Example 4

This example is substantially identical to the preparation method of example 2, except that in the positive electrode layer, the mass ratio of the positive electrode active material and the second electrolyte is 9:1, a step of; and (5) keeping other conditions unchanged, and preparing the solid-state battery cell.

Example 5

The preparation method of this example is basically identical to that of example 1, except that the negative electrode material of this example is only indium foil, and other conditions are unchanged, so as to prepare the solid-state battery cell.

Example 6

The electrolyte obtained in example 1 was used as a second electrolyte; the electrolyte obtained in example 2 is a first sulfide electrolyte, b1 in this example: b2 =1:2; and (5) preparing the solid-state battery cell under other unchanged conditions.

Example 7

Substantially the same as the preparation method of example 2, except that the second sulfide electrolyte was prepared by the following method: na is mixed with ₂ S、Li ₂ S、P ₂ S ₅ Carrying out high-energy ball milling mixing treatment on LiCl according to the mol ratio of 0.075:4.925:1:2 to obtain a mixture; wherein the ball milling rotating speed is 450r, the ball milling time is 6h, the intermittent ball milling is carried out, the mixture is sintered in argon atmosphere, and the sulfide electrolyte Li is obtained after crushing _5.925 Na _0.075 PS ₅ Cl; wherein the sintering treatment temperature is 525 ℃, the sintering treatment time is 6 hours, and the heating rate is 5 ℃/min;

the sulfide electrolyte of this example was used as the second sulfide electrolyte, and the sulfide electrolyte of example 2 was used as the first sulfide electrolyte, under the same conditions, to prepare a solid-state battery.

Comparative example 1

Li is mixed with ₂ S、P ₂ S ₅ Mixing LiCl with high energy ball mill according to the mol ratio of 5:1:2 to obtain a mixture; wherein the ball milling rotating speed is 450r, the ball milling time is 6h, and the intermittent ball milling is performed; sintering the mixture in argon atmosphere, and crushing to obtain sulfide electrolyte, wherein the sulfide electrolyte is used as the first sulfide electrolyte and the second sulfide electrolyte in the embodiment; wherein the sintering treatment temperature is 530 ℃, the sintering treatment time is 6 hours, and the heating rate is 5 ℃/min;

cold-press molding 0.15g of the first sulfide electrolyte in a battery mold to obtain a solid electrolyte layer;

0.01g of positive electrode layer material was placed on one side of the electrolyte layer (positive electrode layer material comprising positive electrode active material, second electrolyte in a mass ratio of 8:2), the positive electrode active material having the formula of Li _1.2 Na _0.05 Ni _0.325 Co _0.1 Mn _0.575 O _2.25 The method comprises the steps of carrying out a first treatment on the surface of the And (3) making the indium foil close to the other side of the solid electrolyte layer, placing the lithium foil on one side of the indium foil far away from the solid electrolyte layer, placing the negative electrode current collector on one side of the lithium foil far away from the solid electrolyte layer, and then performing integrated compression molding treatment, wherein the pressure maintaining time is more than or equal to 20min, so as to obtain the solid battery core.

Test examples

The above method was repeated twice to obtain a solid-state battery cell, and the solid-state battery cell was assembled into a solid-state lithium ion battery, and the battery was subjected to a 0.05C first charge-discharge test, a 0.2C discharge test, and a 0.5C cycle performance test, the test results being shown in table 1.

TABLE 1

In table 1, first effect=first discharge capacity/first charge capacity

Fig. 1 and 2 are SEM images of sulfide electrolyte according to an embodiment of the present invention. As can be seen from table 1, the solid-state battery cells provided in examples 1 to 7 of the present invention were used in batteries, and the batteries of the examples were shown to have excellent cycle performance and capacity retention ratio, as compared with the comparative examples, with excellent 0.2C discharge capacity and capacity retention ratio. In addition, the batteries of examples 1 to 3 of the present invention had higher initial efficiency, 0.2C discharge capacity, and capacity retention ratio than the comparative examples. The inventor considers that sulfide electrolytes with the same element composition are respectively contained in the positive electrode layer and the solid electrolyte layer, so that the interfacial compatibility between the positive electrode layer and the solid electrolyte layer is improved; and the first sulfide electrolyte and the second sulfide electrolyte adopt Na and K to replace part of Li sites in the conventional sulfide electrolyte, so that the transmission rate of lithium ions is improved. According to examples 1-7, the cyclic performance and capacity retention rate of the battery can be further improved by controlling the content of M element.

Example 4 has excellent first charge-discharge capacity, first effect, 0.2C discharge capacity, but the capacity retention rate is slightly decreased, and the inventors studied that it is possible that the battery has a small current density under low-rate conditions as the mass ratio of the positive electrode active material and the second electrolyte increases, but the positive electrode layer is in good contact with the electrolyte layer, but the partial capacity loss is caused as the current density increases. Example 5 has higher first discharge capacity, 0.2C discharge capacity and capacity retention than comparative example 1, but the first discharge efficiency is slightly lower, and the inventors studied that it is possible that the first efficiency is lowered due to partial lithium loss caused by the use of indium foil alone for the negative electrode, as compared to the negative electrode prepared by compounding indium foil and lithium foil.

It should be noted that, the numerical values and the numerical ranges related to the embodiments of the present invention are approximate values, and may have a certain range of errors under the influence of the manufacturing process, and those errors may be considered to be negligible by those skilled in the art.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (11)

1. The solid-state battery cell is characterized by comprising a positive electrode layer and a solid electrolyte layer which are stacked;

the solid electrolyte layer includes a first sulfide electrolyte; the positive electrode layer contains a positive electrode active material and a second electrolyte;

the first sulfide electrolyte has the molecular formula of Li _a1 M _b1 PS _c1 X _d1 The molecular formula of the second sulfide electrolyte is Li _a2 M _b2 PS _c2 X _d2 Wherein b1: b2 is 1:1 to 1:2, X is selected from halogen, M is selected from at least one of Na and K.

2. The solid state battery of claim 1, wherein a1 is 5.5-6.5, b1 is 0.001-0.1, c1 is 4.5-5.5, d1 is 0.9-1.6; and/or the number of the groups of groups,

a2 is 5.5-6.5, b2 is 0.001-0.1, c2 is 4.5-5.5, d2 is 0.9-1.6.

3. The solid state battery of claim 1, wherein the mass ratio of the sum of the mass of the positive electrode active material, the second sulfide electrolyte to the mass of the first sulfide electrolyte is (1-6): 30.

4. the solid state battery of claim 1, wherein in the positive electrode layer, the mass ratio of the positive electrode active material to the second sulfide electrolyte is (6:4) - (9.5:0.5).

5. The solid state battery of claim 1, wherein the positive electrode active material has a molecular formula of Li _x Na _y Ni _e Co _f Mn _g O _z ，

Wherein e+f+g=1, e is more than or equal to 0.1 and less than or equal to 0.5, f is more than or equal to 0 and less than or equal to 0.3, and g is more than or equal to 0.5 and less than or equal to 0.9; x+y is more than 1 and less than or equal to 1.5, x is more than or equal to 1 and less than or equal to 1.5, y is more than 0 and less than or equal to 0.5; z is more than or equal to 2 and less than or equal to 2.5.

6. The solid state battery of any of claims 1-5, further comprising a negative electrode layer, wherein the positive electrode layer, the solid state electrolyte layer, and the negative electrode layer are stacked in that order.

7. The solid state cell of claim 6, wherein the material of the negative electrode layer comprises indium or a lithium-indium alloy.

8. A method for preparing a solid-state battery cell according to any one of claims 1 to 7, comprising the steps of:

pressing a raw material at least comprising a first sulfide electrolyte to obtain a solid electrolyte layer;

placing a raw material at least comprising a positive electrode active material and a second electrolyte on one side of the solid electrolyte layer to obtain an intermediate;

and performing compression molding treatment on the intermediate to obtain the solid-state battery cell.

9. The method of manufacturing according to claim 8, further comprising the step of, prior to the press forming process: the material of the negative electrode layer is placed on the other side of the solid electrolyte layer.

10. The method of producing according to claim 8, wherein the first sulfide electrolyte and the second sulfide electrolyte are each independently produced by a method comprising: sintering a raw material comprising lithium sulfide, phosphorus sulfide, a halogen compound and an alkali metal compound;

wherein the alkali metal compound is selected from a compound of Na and/or a compound of K; the sintering treatment temperature is 510-560 ℃ and the sintering treatment time is 3-8 h.

11. A solid state lithium ion battery comprising a solid state cell according to any one of claims 1-7.

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