Composite solid electrolyte, preparation method thereof, negative electrode and lithium ion battery

Abstract

The application discloses a composite solid electrolyte and a preparation method thereof, a negative electrode and a lithium ion battery, and relates to the technical field of lithium ion batteries. The composite solid electrolyte comprises a solid electrolyte framework and a silicon monoxide film, and the silicon monoxide film is formed on the solid electrolyte framework; wherein the solid electrolyte framework comprises electrolyte nanofibers and a conductive agent, the conductive agent is adhered to the electrolyte nanofibers, and the silicon monoxide film is formed on one side of the electrolyte nanofibers where the conductive agent is located. The composite solid electrolyte introduces the electrolyte nanofibers and the silicon monoxide film, the electrolyte nanofibers can improve the high-temperature safety performance of the lithium ion battery, the silicon monoxide film can improve the energy density of the lithium ion battery, and the safety and the energy density of the lithium ion battery are considered; meanwhile, the electrolyte nanofibers and the conductive agent are combined to form the solid electrolyte framework, the ion conductivity between the solid electrolyte framework and the silicon monoxide film is improved, and therefore, the ion conductivity of the composite solid electrolyte is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a composite solid electrolyte, a preparation method thereof, a negative electrode and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries have become the main energy storage devices for portable electronic products, unmanned aerial vehicles and electric vehicles due to their high power density, long cycle life and low self-discharge. However, in recent years, the safety hazards caused by organic electrolytes with low boiling point and low flash point have increased with the increase of the application scale of the batteries, which has seriously restricted the development of high specific energy lithium ion batteries. Therefore, with the increasing requirements for the safety and high energy density of lithium ion batteries, people have gradually paid attention to all-solid-state electrolytes.

[0003] At present, common solid-state electrolytes mainly include polymer solid-state electrolytes and inorganic solid-state electrolytes. The polymer solid-state electrolyte has good flexibility, stable interface and easy operability, but its ionic conductivity is low, only 10 -7 ~ 10 -6 S·cm -1 The inorganic solid-state electrolyte has high flame retardancy and high room temperature ionic conductivity, but there is a serious interface problem between the inorganic solid-state electrolyte and the active material, which makes it difficult to be commercialized. It can be seen that the above two kinds of solid-state electrolytes have different defects and are not optimal. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a composite solid electrolyte, a preparation method thereof, a negative electrode and a lithium ion battery.

[0005] The composite solid electrolyte disclosed by the present application comprises a solid electrolyte framework and a silicon monoxide film, and the silicon monoxide film is formed on the solid electrolyte framework.

[0006] The solid electrolyte framework comprises electrolyte nanofibers and a conductive agent, the conductive agent is adhered to the electrolyte nanofibers, and the silicon monoxide film is formed on the side of the electrolyte nanofibers where the conductive agent is located.

[0007] According to an embodiment of the present application, the electrolyte nanofibers are yttria-doped zirconia, and the electrolyte nanofibers are vertically oriented.

[0008] According to an embodiment of the present application, the conductive agent is one or more of carbon nanotubes, superconducting carbon black, acetylene black and graphene.

[0009] According to an embodiment of the present application, the thickness of the electrolyte nanofibers is 5-100u, and the thickness of the silicon monoxide film is 3-50u.

[0010] The preparation method of the composite solid electrolyte comprises the following steps:

[0011] S1. Nanofiber precursor is prepared by electrospinning, and electrolyte nanofiber is obtained by calcination;

[0012] S2. The gelatin aqueous solution is added to the electrolyte nanofiber, and nanofiber mixed solution is obtained by ultrasonic oscillation;

[0013] S3. After the nanofiber mixed solution is subjected to electric field orientation, the conductive agent is added to the nanofiber mixed solution, and nanofiber skeleton solution is obtained by standing;

[0014] S4. After the nanofiber skeleton solution is cooled, it is soaked in a glutaraldehyde solution to obtain a solid electrolyte precursor;

[0015] S5. The solid electrolyte precursor is calcined to obtain a solid electrolyte skeleton;

[0016] S6. A silicon monoxide film is formed on the solid electrolyte skeleton to obtain a composite solid electrolyte.

[0017] According to an embodiment of the present application, the feed liquid ratio of the electrolyte nanofiber to the gelatin aqueous solution is (5-100) g:(10-100) mL.

[0018] According to an embodiment of the present application, the mass ratio of the conductive agent to the electrolyte nanofiber is (1-5):(5-10).

[0019] According to an embodiment of the present application, the feed liquid ratio of the glutaraldehyde solution to the electrolyte nanofiber is (50-200) mL:(5-100) g.

[0020] The negative electrode comprises a current collector, an active material layer and the composite solid electrolyte as described above, the active material layer is arranged on the current collector, the composite solid electrolyte is arranged on the active material layer, and the silicon monoxide film of the composite solid electrolyte faces the active material layer.

[0021] The lithium ion battery comprises a positive electrode, a separator and an electrolyte, and further comprises the negative electrode as described above.

[0022] Compared with the prior art, the composite solid electrolyte, the preparation method thereof, the negative electrode and the lithium ion battery have the following advantages:

[0023] The composite solid electrolyte of the present application introduces electrolyte nanofibers and silicon monoxide films, the electrolyte nanofibers can improve the high-temperature safety performance of the lithium ion battery, the silicon monoxide films can improve the energy density of the lithium ion battery, and the safety and energy density of the lithium ion battery are considered; at the same time, the electrolyte nanofibers and the conductive agent are compounded to form a solid electrolyte skeleton, which can improve the ion conductivity between the electrolyte nanofibers and the silicon monoxide films, thereby ensuring the ion conductivity of the composite solid electrolyte.

[0024] In addition, the electrolyte nanofibers in the composite solid electrolyte of the present application are arranged in a vertical orientation to form the shortest path for lithium ion transmission, thereby improving the transmission capacity of lithium ions. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings described herein are intended to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their description serve to explain the present application. They are not intended to be an improper limitation on the present application. In the drawings:

[0026] Figure 1 It is a structural schematic diagram of the composite solid electrolyte in Example One;

[0027] Figure 2 It is a partial structural schematic diagram of the anode in Example Three;

[0028] Figure 3 It is a partial structural schematic diagram of the lithium ion battery in Example Four.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] 1, solid electrolyte skeleton; 11, electrolyte nanofiber; 12, conductive agent; 2, silicon monoxide film;

[0031] 01, composite solid electrolyte; 02, active material layer;

[0032] 001, anode; 002, separator. DETAILED DESCRIPTION

[0033] The following will disclose multiple embodiments of the present application through figures. For clear description, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit the present application. That is, in some embodiments of the present application, these practical details are unnecessary. In addition, for the purpose of simplifying the figures, some conventional structures and components will be drawn in a simple schematic manner in the figures.

[0034] In addition, the technical solutions among the various embodiments can be combined with each other, but it must be based on that a person skilled in the art can realize, when the combination of the technical solutions appears contradictory or cannot be realized, it should be considered that the combination of the technical solutions does not exist, and is not within the protection scope required by the present application.

[0035] Embodiment one

[0036] The present embodiment provides a composite solid electrolyte, referring to Figure 1 The composite solid electrolyte 01 comprises a solid electrolyte framework 1 and a silicon monoxide film 2, and the silicon monoxide film 2 is formed on the solid electrolyte framework 1. The solid electrolyte framework 1 comprises electrolyte nanofibers 11 and a conductive agent 12, the conductive agent 12 is adhered to the electrolyte nanofibers 11, and the silicon monoxide film 2 is formed on the side of the electrolyte nanofibers 11 where the conductive agent 12 is located.

[0037] The composite solid electrolyte introduces electrolyte nanofibers and a silicon monoxide film, the electrolyte nanofibers can improve the high-temperature safety performance of the lithium ion battery, the silicon monoxide film can improve the energy density of the lithium ion battery, and the safety and energy density of the lithium ion battery are considered; at the same time, the electrolyte nanofibers and the conductive agent are combined to form a solid electrolyte framework, which can improve the ion conductivity between the silicon monoxide film, thereby ensuring the ion conductivity of the composite solid electrolyte.

[0038] In this example, the electrolyte nanofibers 11 are yttria-doped zirconia. At the same time, the electrolyte nanofibers 11 are arranged in a vertical orientation, thereby forming the shortest path for lithium ion transmission, thereby improving the transmission capacity of lithium ions.

[0039] In this example, the conductive agent 12 is one or more of carbon nanotubes, superconducting carbon black, acetylene black and graphene.

[0040] In this example, the thickness of the electrolyte nanofibers 11 is 5-100u, and the thickness of the silicon monoxide film 2 is 3-50u.

[0041] Embodiment two

[0042] The present embodiment provides a preparation method of a composite solid electrolyte, which can be used to prepare the composite solid electrolyte described in embodiment one.

[0043] The preparation method of the composite solid electrolyte comprises the following steps:

[0044] S1. A nanofiber precursor is prepared by electrospinning, and electrolyte nanofibers are obtained by calcination;

[0045] S2. The gelatin aqueous solution is added to the electrolyte nanofibers, and a nanofiber mixed solution is obtained by ultrasonic oscillation;

[0046] S3. After the nanofiber mixed solution is oriented by an electric field, a conductive agent is added to the nanofiber mixed solution, and the solution is left to stand to obtain a nanofiber skeleton solution;

[0047] S4. After the nanofiber skeleton solution is cooled, the solution is soaked in a glutaraldehyde solution to obtain a solid electrolyte precursor;

[0048] S5. The solid electrolyte precursor is calcined to obtain a solid electrolyte skeleton;

[0049] S6. A silicon monoxide film is formed on the solid electrolyte skeleton to obtain a composite solid electrolyte.

[0050] In this example, in step S1, after the nanofiber precursor is prepared, the nanofiber precursor is calcined at 300-1200°C for 0.5-10h.

[0051] In this example, in step S2, the ratio of the electrolyte nanofiber to the gelatin aqueous solution is (5-100)g:(10-100)mL, and the concentration of the gelatin aqueous solution is 1%.

[0052] In this example, in step S3, the mass ratio of the conductive agent to the electrolyte nanofiber is (1-5):(5-10). The electrolyte nanofiber in the nanofiber mixed solution is oriented and arranged vertically to the substrate by an electric field orientation method. After the conductive agent is added to the nanofiber mixed solution oriented by the electric field, the solution is left to stand for 12-48h to allow the conductive agent to sink to the bottom of the electrolyte nanofiber.

[0053] In this example, in step S4, the ratio of the glutaraldehyde solution to the electrolyte nanofiber is (50-200)mL:(5-100)g. After the nanofiber skeleton solution is cooled to 5-15°C, the solution is soaked in a glutaraldehyde solution with a concentration of 25% to form chemical crosslinking.

[0054] In this example, in step S5, the solid electrolyte precursor is calcined at 300-1000°C for 0.5-10h.

[0055] In this example, in step S6, the silicon monoxide film is formed by chemical vapor deposition or magnetron sputtering.

[0056] Example Three

[0057] This example provides a negative electrode, referring to Figure 2 The negative electrode 001 includes a current collector (not shown in the figure), an active material layer 02, and a composite solid electrolyte 01 as described in Example One. The active material layer 02 is arranged on the current collector, the composite solid electrolyte 01 is arranged on the active material layer 02, and the silicon monoxide film of the composite solid electrolyte 01 faces the active material layer 02.

[0058] In this example, the active material layer 02 is made of artificial graphite or fast-charging graphite.

[0059] Example Four

[0060] This example provides a lithium ion battery, see Figure 3 , the lithium ion battery comprises a positive electrode (not shown in the figure), a separator 002 and an electrolyte (not shown in the figure), and further comprises the negative electrode 001 described in Example Three. Among them, the negative electrode 001 is arranged on the separator 002, and the composite solid electrolyte 01 is located between the active material layer of the negative electrode 001 and the separator 002.

[0061] In this example, the positive electrode is one or more of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide, lithium manganate and lithium nickelate, the electrolyte is lithium hexafluorophosphate electrolyte, and the isolation film is PP / PE film. Among them, the concentration of lithium hexafluorophosphate electrolyte is 1mol / L, which includes lithium hexafluorophosphate and an organic solvent, and the organic solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.

[0062] In order to further illustrate the invention, seven samples of lithium ion batteries are provided in this application, which are described one by one as follows.

[0063] Sample One

[0064] The lithium ion battery provided by Sample One includes a positive electrode, a negative electrode, a separator, an electrolyte and a composite solid electrolyte, wherein the positive electrode is lithium cobaltate, the negative electrode is fast-charging graphite, the electrolyte is lithium hexafluorophosphate electrolyte, and the isolation film is PP / PE film.

[0065] Among them, the composite solid electrolyte used in Sample One includes a solid electrolyte framework and a silicon monoxide film, and the silicon monoxide film is formed on the solid electrolyte framework. The solid electrolyte framework includes electrolyte nanofibers and a conductive agent, the conductive agent adheres to the electrolyte nanofibers, and the silicon monoxide film is formed on the side of the electrolyte nanofibers where the conductive agent is located. The electrolyte nanofiber is yttrium-doped zirconium dioxide, and the electrolyte nanofiber is arranged in vertical orientation; the conductive agent is a carbon tube; the thickness of the electrolyte nanofiber is 5u, and the thickness of the silicon monoxide film is 5u.

[0066] The preparation method of the lithium ion battery includes two preparation processes, one is to prepare the composite solid electrolyte, the second is to prepare the negative electrode by using the prepared composite solid electrolyte, and the third is to prepare the lithium ion battery by using the prepared negative electrode. The specific preparation method is as follows:

[0067] (1) Preparation of composite solid electrolyte

[0068] S1. Nanofiber precursor is prepared by electrospinning, and is calcined at 500℃ for 2h to obtain electrolyte nanofiber;

[0069] S2. 20 mL of a 1% gelatin aqueous solution was added to 10 g of electrolyte nanofibers, and a nanofiber mixed solution was obtained after ultrasonic oscillation;

[0070] S3. After the nanofiber mixed solution was subjected to electric field orientation, the electrolyte nanofibers in the nanofiber mixed solution were arranged in a vertical direction to the substrate, and then 2 g of a conductive agent was added to the nanofiber mixed solution and left to stand for 48 h, so that the conductive agent sank to the bottom of the electrolyte nanofibers, and a nanofiber skeleton solution was obtained;

[0071] S4. After the nanofiber skeleton solution was cooled to 10°C, it was soaked in 100 mL of a 25% glutaraldehyde solution to form chemical crosslinking, and a solid-state electrolyte precursor was obtained;

[0072] S5. The solid-state electrolyte precursor was calcined at 300°C for 0.5 h to obtain a solid-state electrolyte skeleton;

[0073] S6. A silicon monoxide film was formed on the solid-state electrolyte skeleton by chemical vapor deposition to obtain a composite solid-state electrolyte.

[0074] (2) Preparation of the negative electrode

[0075] The active material was coated on the current collector to form an active material layer, and then the composite solid-state electrolyte was placed on the active material layer to obtain the negative electrode. The silicon monoxide film of the composite solid-state electrolyte faces the active material layer.

[0076] (3) Preparation of the lithium ion battery

[0077] The positive electrode, the negative electrode, and the separator were stacked in sequence and then rolled into an electric core, the electric core was placed in a shell, electrolyte was injected into the shell, and then the shell was sealed to obtain the lithium ion battery. The composite solid-state electrolyte is located between the active material layer of the negative electrode and the separator.

[0078] Sample two

[0079] The main difference between sample two and sample one is that:

[0080] The thickness of the electrolyte nanofibers in the composite solid-state electrolyte is 10 u;

[0081] In the preparation of the composite solid-state electrolyte, the amount of the 1% gelatin aqueous solution is 40 mL, the amount of the electrolyte nanofibers is 20 g, and the amount of the conductive agent is 4 g.

[0082] Sample three

[0083] The main difference between sample three and sample one is that:

[0084] The thickness of the electrolyte nanofibers in the composite solid-state electrolyte is 15 u;

[0085] In the preparation of the composite solid electrolyte, the amount of the 1% gelatin aqueous solution is 60 mL, the amount of the electrolyte nanofiber is 30 g, and the amount of the conductive agent is 6 g.

[0086] Sample four

[0087] The main difference between sample four and sample one is that:

[0088] The thickness of the electrolyte nanofiber in the composite solid electrolyte is 20u;

[0089] In the preparation of the composite solid electrolyte, the amount of the 1% gelatin aqueous solution is 80 mL, the amount of the electrolyte nanofiber is 40 g, and the amount of the conductive agent is 8 g.

[0090] Sample five

[0091] The main difference between sample five and sample three is that the thickness of the silicon monoxide film in the composite solid electrolyte is 10u.

[0092] Sample six

[0093] The main difference between sample six and sample three is that the thickness of the silicon monoxide film in the composite solid electrolyte is 15u.

[0094] Sample seven

[0095] The main difference between sample seven and sample three is that the thickness of the silicon monoxide film in the composite solid electrolyte is 20u.

[0096] The main difference between the lithium ion batteries of samples one to four is the thickness of the electrolyte nanofiber, which is 5u, 10u, 15u, and 20u, respectively. The safety performance of the lithium ion batteries of samples one to four was tested, and the specific test results are as follows:

[0097] Table 1 Safety performance test results of samples one to four

[0098]

[0099] As can be seen from Table 1, as the thickness of the electrolyte nanofiber increases, the safety performance of the lithium ion battery is significantly improved. However, when the thickness of the electrolyte nanofiber increases to a certain extent, the safety performance of the lithium ion battery tends to be flat.

[0100] The main difference between the lithium ion batteries of sample three and samples five to seven is that the thickness of the silicon monoxide film is different, and the thickness of the silicon monoxide film in the lithium ion batteries of sample three, five to seven is 5u, 10u, 15u and 20u respectively. The capacity first effect test of the above-mentioned lithium ion batteries of sample three, five to seven is carried out, and the specific test results are as follows:

[0101] Table 2 Capacity first effect test results of sample three, five to seven

[0102] As can be seen from Table 2, as the thickness of the silicon monoxide film increases, the capacity of the battery also increases, and the first effect decreases.

[0103] The above only describes the embodiments of the present application and is not used to limit the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of claims of the present application.

Claims

1. A method for producing a composite solid electrolyte, characterized by, The method comprises the following steps: S1. preparing a nanofiber precursor by electrospinning, and obtaining electrolyte nanofibers after calcination; S2. adding a gelatin aqueous solution into the electrolyte nanofibers, and obtaining a nanofiber mixed solution after ultrasonic oscillation; S3. adding a conductive agent into the nanofiber mixed solution after electric field orientation, and obtaining a nanofiber skeleton solution after standing; S4. obtaining a solid electrolyte precursor after soaking the nanofiber skeleton solution in a glutaraldehyde solution after temperature reduction; S5. obtaining a solid electrolyte skeleton after calcination of the solid electrolyte precursor; S6. forming a silicon monoxide film on the solid electrolyte skeleton to obtain a composite solid electrolyte. The material-liquid ratio of the electrolyte nanofibers to the gelatin aqueous solution is (5-100) g:(10-100) mL; the mass ratio of the conductive agent to the electrolyte nanofibers is (1-5):(5-10); and the material-liquid ratio of the glutaraldehyde solution to the electrolyte nanofibers is (50-200) mL:(5-100) g. The composite solid electrolyte comprises a solid electrolyte skeleton and a silicon monoxide film formed on the solid electrolyte skeleton; the solid electrolyte skeleton comprises electrolyte nanofibers and a conductive agent adhered to the electrolyte nanofibers, and the silicon monoxide film is formed on the side of the electrolyte nanofibers where the conductive agent is located.

2. The method for producing a composite solid electrolyte according to claim 1, characterized by, The electrolyte nanofibers are yttria-doped zirconia, and the electrolyte nanofibers are vertically oriented.

3. The method for producing a composite solid electrolyte according to claim 1, characterized by, The conductive agent is one or more of carbon nanotubes, superconducting carbon black, acetylene black and graphene.

4. The method for producing a composite solid electrolyte according to claim 1, characterized by, The thickness of the electrolyte nanofibers is 5-100 u, and the thickness of the silicon monoxide film is 3-50 u.

5. A negative electrode characterized by comprising: The composite solid electrolyte is arranged on the active material layer, and the silicon monoxide film of the composite solid electrolyte faces the active material layer.

6. A lithium-ion battery, characterized by The battery comprises a positive electrode, a separator and an electrolyte, and further comprises the negative electrode of claim 5.

Images