WO2021248766A1

WO2021248766A1 - Composite polymer solid-state electrolyte material and preparation method therefor and application thereof

Info

Publication number: WO2021248766A1
Application number: PCT/CN2020/121426
Authority: WO
Inventors: 朱敏; 刘雨轩; 胡仁宗; 刘军
Original assignee: 华南理工大学
Priority date: 2020-06-10
Filing date: 2020-10-16
Publication date: 2021-12-16
Also published as: JP2023528991A; CN111883823A; JP7450299B2; CN111883823B

Abstract

The present invention relates to the technical field of solid-state electrolyte materials, and disclosed are a composite polymer solid-state electrolyte material and a preparation method therefor and an application thereof. The composite polymer solid-state electrolyte material is prepared from the following components: a polymer electrolyte, a lithium salt, a filler, and an organic solvent, wherein the filler is a lithium alloy, the general formula of the lithium alloy is Li_xM, M is a metal or non-metal element, x is greater than or equal to 1, and the lithium alloy is more than one of Li_xM. Further disclosed is the preparation method for the composite polymer solid-state electrolyte material. The ionic conductivity of the composite polymer electrolyte of the present invention is about one order of magnitude higher than that of a pure polymer electrolyte; the solid-state electrolyte has excellent cycling stability and can replace diaphragms and electrolytic solutions in existing lithium batteries. The composite polymer solid-state electrolyte of the present invention is applied to the field of ion conductors or lithium ion batteries.

Description

Composite polymer solid electrolyte material and preparation method and application thereof

Technical field

The invention belongs to the technical field of solid electrolyte materials, and specifically relates to a composite polymer solid electrolyte material and a preparation method and application thereof.

Background technique

Commercialized lithium-ion batteries are difficult to meet the requirements of high energy density, high safety and long life for power batteries and large-scale energy storage. The traditional liquid electrolyte is flammable and easy to leak during use, and has insufficient stability outside the battery operating temperature. Solid electrolytes have high mechanical properties, will not leak, and still have good stability at high temperatures. Therefore, the use of solid electrolytes to replace traditional liquid electrolytes is the key to the development of high-safety and high-energy density lithium batteries.

For polymer electrolytes, its soft and easy to bend characteristics ensure good contact between the electrode and the electrolyte interface; at the same time, compared with inorganic solid electrolytes, this characteristic makes polymer electrolytes more excellent processability This is very beneficial to the industrial production of polymer electrolytes. However, it is difficult for a single-component solid electrolyte to meet one or more conditions such as high ionic conductivity, low interfacial impedance, high stability, and easy large-scale preparation. For example, the first discovered and widely studied polymer electrolyte polyethylene oxide is limited by its semi-crystalline properties. In semi-crystalline polyethylene oxide, ion flow only occurs in the amorphous region of its matrix, which results in its room temperature ionic conductivity of only 10 ^-6 to 10 ^-8 S·cm ^-1 , which is far from satisfying practical applications. Therefore, the composite electrolyte is considered to be a compromise solution for realizing the application of solid electrolytes, which is used to realize the complementary advantages between the electrolyte components and improve the electrochemical performance of the composite electrolyte. Studies have shown that in composite polymer electrolytes with inorganic fillers, the high-speed channel for lithium ion transmission at the interface between the inorganic filler and polymer is critical to the improvement of the ion conductivity of the composite polymer electrolyte. Therefore, the design has The interface of high-speed lithium ion transfer is an effective way to solve the low ion conductivity of the polymer matrix.

Existing fillers used for composite in composite polymer solid electrolytes mainly include nano-ceramic fillers, such as published patent applications CN 105655635A, patent CN 102709597A; ionic liquids, such as published patent CN 104538670A; organic micro-nano porous particles , Such as CN 106654363A, etc. The increase in the ion conductivity of the polymer electrolyte by the addition of these fillers can be summarized as reducing the crystallinity of the polymer, and at the same time, the filler interacts with the polymer matrix to form a lithium ion transmission channel.

However, in the composite electrolyte prepared by the fillers that have been disclosed, the interface interaction between the filler and the polymer electrolyte is weak, which makes the transfer rate of lithium ions in these interface transmission channels low. Therefore, these fillers have a lower ion conductivity of the polymer matrix. The lifting effect is limited. On the other hand, the existing composite polymer electrolyte materials lack the control of the microstructure and the design of the ion rapid transfer channel for the compounding of the filler. These factors all lead to the unsatisfactory performance of the currently prepared composite polymer electrolyte materials in practical applications.

Summary of the invention

Based on the problems of the existing polymer electrolyte, the present invention is to provide a composite polymer solid electrolyte material and a preparation method thereof. The composite polymer solid electrolyte material of the present invention has better ionic conductivity in a larger temperature range.

Another object of the present invention is to provide the application of the composite polymer solid electrolyte material. The composite polymer solid electrolyte material is applied in a lithium battery and used as a solid electrolyte of a lithium battery.

The purpose of the present invention is achieved through the following technical solutions:

A composite polymer solid electrolyte material prepared from the following components:

Polymer electrolyte, lithium salt, filler and organic solvent; the filler is a lithium alloy; the lithium salt is a lithium salt used in a lithium ion battery.

The lithium salt is preferably at least one of lithium perchlorate, lithium hexafluorophosphate or lithium bistrifluoromethanesulfonimide;

The general formula of the lithium alloy is Li _x M, where M is a metal or non-metal element, x≥1, and x is the atomic ratio of Li/M; the lithium alloy is one or more _{of Li x M.}

M in the lithium alloy is preferably Si, Ge or Sn.

The lithium alloy is more preferably one or more of Li ₂₁ Si ₅ , Li ₂₁ Ge ₅ , and Li ₂₁ Sn ₅ .

The organic solvent includes at least one of 1,3-dioxolane or 2-methyl-1,3-dioxolane.

The organic solvent also includes an auxiliary solvent, and the auxiliary solvent is an ether or ester organic solvent, specifically ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate or dimethylformamide ( DMF) more than one kind.

The mass of the filler accounts for 1%-30% of the total mass of the polymer electrolyte, the lithium salt and the filler. The mass ratio of the polymer electrolyte to the lithium salt is 1:0.1 to 1:0.8.

The polymer electrolyte is one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polycarbonate, polyvinylidene fluoride and copolymers thereof.

The volume-to-mass ratio of the organic solvent to the polymer electrolyte is (15-30) mL:1g.

The composite polymer solid electrolyte material is in the shape of a membrane, and the thickness of the membrane is 25-200 microns.

The preparation method of the composite polymer solid electrolyte material includes the following steps:

1) Mix the filler, polymer electrolyte and lithium salt uniformly in an organic solvent to obtain a mixture;

2) The mixture is formed into a film to obtain a composite polymer electrolyte material.

The organic solvent is a main solvent and an auxiliary solvent; the main solvent is one or more of 1,3-dioxolane or 2-methyl-1,3-dioxolane; the auxiliary solvent is an ether Or ester organic solvents, specifically one or more of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate or dimethylformamide. The auxiliary solvent adjusts the viscosity.

The volume-to-mass ratio of the organic solvent to the polymer electrolyte is (15-30) mL:1g. The volume ratio of the auxiliary solvent to the main solvent is 0.1:1 to 5:1.

The film formation specifically refers to pouring the mixture on a substrate, drying at 60°C to 100°C for 6 hours to 24 hours in an anhydrous and oxygen-free environment, and peeling off to obtain a film material.

The solid electrolyte has an ionic conductivity greater than 3×10 ^{-5 S/cm at 30°C.}

The above-mentioned composite polymer solid electrolyte is applied to the field of ion conductor or lithium ion battery.

A lithium ion battery includes a positive electrode, a negative electrode, and a solid electrolyte placed between the positive and negative electrodes. The solid electrolyte is the above-mentioned composite polymer solid electrolyte.

The principle of the present invention is: the present invention utilizes the reaction of a lithium alloy with an organic solvent to open the ring of the 1,3 dioxolane-based cyclic solvent, and form an organic layer on the surface of the lithium alloy that can realize the rapid transfer of lithium ions. Floor. At the same time, the organic layer is uniformly dispersed in the lithium salt-containing polymer electrolyte along with the lithium alloy, and interacts with the lithium salt-containing polymer matrix, so that a large number of ion rapid transmission channels are formed in the polymer matrix. The promotion of has a key role. At the same time, after the nano-scale lithium alloy filler interacts with the polymer matrix, the regular crystalline segments around it are broken, which increases the proportion of amorphous regions in the polymer matrix. Since the migration of lithium ions in the polymer electrolyte is mainly contributed by the amorphous region in the polymer, the improvement of the amorphous region can further enhance the ability of the composite polymer electrolyte to transfer lithium ions.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention constructs a lithium-rich solid electrolyte interface similar to the liquid battery system between the polymer solid electrolyte and the filler. These interfaces constructed in the polymer electrolyte provide a fast channel for the migration of the lithium ion battery, so that the polymer The ionic conductivity of the electrolyte has been greatly improved. The composite polymer solid electrolyte of the present invention can replace the diaphragm and electrolyte in a traditional battery to realize the circulation of an all-solid lithium battery at room temperature. At the same time, because the traditional liquid electrolyte is replaced, the lithium battery using the solid electrolyte does not need to be equipped with an additional temperature control system.

(2) The preparation method of the present invention has universal applicability. The main material polymer electrolyte and lithium salt have a wide range of choices and are cheap and easy to obtain. This method can be used to prepare composite polymer solid electrolytes under different combinations of polymer electrolytes and lithium salts, and the prepared solid electrolytes have relatively high advantages. Good cycle stability.

Description of the drawings

Figure 1 is a high-resolution scanning electron micrograph of a cross-section of the composite polymer electrolyte material prepared in Example 1;

2 is a graph showing the temperature dependence of the electrical conductivity of polymer electrolytes composited with different lithium alloys and other inorganic fillers prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3;

3 is a graph showing the relationship between the electrical conductivity of the composite polymer electrolytes prepared in Examples 1, 4, and 5 and Comparative Example 1 as a function of Li ₂₁ Si _{5 filler content;}

4 is a charge-discharge cycle performance diagram of a lithium symmetric battery using the composite polymer electrolyte prepared in Example 6;

5 is a graph showing the cycle performance of an all-solid-state lithium metal battery assembled using composite polymer electrolytes, lithium iron phosphate positive electrodes and lithium metal negative electrodes prepared in Examples 1 and 7.

detailed description

Hereinafter, the present invention will be further described in detail with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1

Polymer electrolyte: Polyethylene oxide (PEO) powder, purchased from Aladdin Company, with an average molecular weight of 600,000.

Lithium salt: Lithium bistrifluoromethanesulfonimide (LiTFSI), purchased from Aladdin Company.

Lithium alloy: lithium silicon alloy Li ₂₁ Si ₅ , self-made by thermal reaction method, self-made method will be explained in the specific process.

Organic solvents: 1,3 dioxolane (DOL) and ethylene glycol dimethyl ether (DME), purchased from Macklin.

Preparation of lithium-silicon alloy Li ₂₁ Si _5:

Under the protection of argon atmosphere, mix the lithium particles and silicon powder in a ratio of 21:5 (about 0.52g of lithium particles and about 0.48g of silicon powder) on a heating table and heat them to 200°C to melt the lithium particles. After the liquid lithium is stirred, the lithium-silicon alloy powder can be formed. In order to further improve the purity of the lithium-silicon alloy Li ₂₁ Si ₅ and reduce the particle size of the lithium-silicon alloy, the powder is put into a ball milling tank, and the lithium-silicon alloy powder is refined by vibrating ball milling, in which the grinding ball is mixed with The powder ratio is 50:1, the ball milling time is 20h, the rotation speed is 1000rpm, and the Li ₂₁ Si ₅ lithium-silicon alloy powder (particle size 200-300nm) is prepared.

A method for preparing a composite polymer electrolyte material includes the following steps:

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weighed according to the proportion of 5% of the total mass of the _{lithium silicon alloy Li 21} Si ₅ Take 74mg of Li ₂₁ Si ₅ powder; add PEO, LiTFSI and Li ₂₁ Si ₅ powder to the above-mentioned DOL and DME mixed organic solvent, continue to stir for 12 hours, then pour it on a clean PTFE board, and then at 60 ℃ After drying for 12 hours at a temperature of, a PEO-based composite polymer electrolyte _{added with a lithium-silicon alloy Li 21} Si _{5 is obtained.}

The cross-sectional morphology of the composite polymer electrolyte prepared in Example 1, that is, the high-resolution scanning electron micrograph, is shown in FIG. 1.

The composite polymer electrolyte prepared in Example 1 was sandwiched between two stainless steel substrates with polished surfaces to form a blocking electrode. Using electrochemical work to perform AC impedance analysis on the composite material in the blocking electrode at different temperatures in a thermostat, the ionic conductivity corresponding to different temperatures can be obtained. The relationship between the electrical conductivity and temperature of the composite polymer electrolyte prepared in Example 1 in a wide temperature range is shown in Fig. 2 and Fig. 3.

The composite polymer electrolyte prepared in Example 1 was assembled with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode to form an all-solid-state lithium metal battery. The cycle performance at 45° C. and 0.2 C is shown in FIG. 5. Its capacity is 140.5 mAh g-1 after 100 cycles at 30°C and 0.2C, and its capacity is 110.8 mAh g-1 after 200 cycles at 45°C and 0.5C.

Example 2

Lithium alloy: lithium germanium alloy Li ₂₁ Ge ₅ , self-made by the thermal reaction method, the self-made method is similar to the Li ₂₁ Si ₅ method in Example 1, and the silicon powder is replaced with Ge.

Measure 10mL each of DOL and DME and mix them uniformly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weighed according to the proportion of 5% of the total mass of the _{lithium germanium alloy Li 21} Ge ₅ Take 74mg of Li ₂₁ Ge ₅ powder; add PEO, LiTFSI and Li ₂₁ Ge ₅ powder to the above-mentioned DOL and DME mixed organic solvent, continue to stir for 12 hours, then pour it on a clean PTFE board, and then at 60 ℃ After drying for 12 hours at a temperature of, a PEO-based composite polymer electrolyte _{added with lithium germanium alloy Li 21} Ge _{5 is obtained.}

The method for testing the ionic conductivity versus temperature curve in Example 1 is the same. The relationship between the conductivity and temperature of the composite polymer electrolyte prepared in Example 2 in a wide temperature range is shown in FIG. 2.

Example 3

Lithium alloy: lithium tin alloy Li ₂₁ Sn ₅ , self-made by thermal reaction method, self-made method is the _{same as the above Li 21} Si ₅ method, silicon powder is replaced with Sn.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weighed according to the proportion of 5% of the total mass of the _{lithium tin alloy Li 21} Sn ₅ Take 74mg of Li ₂₁ Sn ₅ powder; add PEO, LiTFSI and Li ₂₁ Sn ₅ powder to the above-mentioned DOL and DME mixed organic solvent, continue to stir for 12 hours, then pour it on a clean PTFE board, and then at 60 ℃ After drying for 12 hours at a temperature of, a PEO-based composite polymer electrolyte _{added with lithium tin alloy Li 21} Sn _{5 is obtained.}

The method for testing the ionic conductivity versus temperature curve in Example 1 is the same. The relationship between the conductivity and temperature of the composite polymer electrolyte prepared in Example 3 in a wide temperature range is shown in FIG. 2.

Example 4

Lithium alloy: lithium-silicon alloy Li ₂₁ Si ₅ , self-made by thermal reaction method, self-made method is the same as in Example 1.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weighed according to the ratio of 10% of the total mass of the _{lithium silicon alloy Li 21} Si ₅ Take _{155 mg of Li 21} Si ₅ powder; add PEO, LiTFSI and Li ₂₁ Si ₅ powder to the above-mentioned DOL and DME mixed organic solvent, continue to stir for 12 hours, then pour it on a clean PTFE board, and then at 60 ℃ After drying for 12 hours at a temperature of, a PEO-based composite polymer electrolyte _{added with a lithium-silicon alloy Li 21} Si _{5 is obtained.}

The method of testing the ionic conductivity versus temperature curve in Example 1 is the same. The conductivity of the composite polymer electrolyte prepared in Example 4 in a wide temperature range is shown in FIG. 3.

Example 5

Lithium alloy: Li-silicon alloy Li ₂₁ Si ₅ , self-made by the thermal reaction method, and the self-made method is the same as in Example 1.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weighed according to the ratio of 15% of the total mass of _{lithium silicon alloy Li 21} Si ₅ Take 247mg of Li ₂₁ Si ₅ powder; add PEO, LiTFSI and Li ₂₁ Si ₅ powder to the above-mentioned DOL and DME mixed organic solvent, continue to stir for 12 hours, then pour it on a clean PTFE board, and then at 60 ℃ After drying for 12 hours at a temperature of, a PEO-based composite polymer electrolyte _{added with a lithium-silicon alloy Li 21} Si _{5 is obtained.}

The method of testing the ionic conductivity versus temperature curve in Example 1 is the same. The conductivity of the composite polymer electrolyte prepared in Example 5 in a wide temperature range is shown in FIG. 3.

Example 6

Lithium alloy: a mixed lithium alloy of lithium silicon alloy Li ₂₁ Si ₅ and lithium germanium alloy Li ₂₁ Ge ₅ , self-made by the thermal reaction method, and the self-made method is the same as in Example 1.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; according to Li ₂₁ Si ₅ and Li ₂₁ Ge ₅ each accounted for 2.5% of the total mass of the powder _{Weigh 37mg each of Li 21} Si ₅ and Li ₂₁ Ge ₅ powders in the ratio of, add PEO, LiTFSI, Li ₂₁ Si ₅ and Li ₂₁ Ge ₅ powders to the above-mentioned mixed organic solvent of DOL and DME, continue to stir for 12h, then pour them On a clean polytetrafluoroethylene board, and then dried at a temperature of 60°C for 12 hours, a PEO-based composite polymer electrolyte mixed with a lithium-silicon alloy and a lithium-germanium alloy was obtained.

The composite polymer electrolyte prepared in Example 6 and lithium metal were assembled to form a lithium symmetric battery, and its cycle performance under the conditions of ^{30° C. and 0.1 mAcm -2 is shown in FIG. 4.} The composite polymer electrolyte prepared in Example 6 was assembled with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode to form an all-solid-state lithium metal battery. The first discharge capacity was 143.2mAh g ^-1 at 45°C and 0.2C. After 50 cycles Its capacity is 131.6 mAh g ^-1 , and the capacity retention rate is 92%.

Example 7

Lithium salt: Lithium perchlorate (LiClO ₄ ), purchased from Aladdin Company.

Organic solvents: 2-methyl-1,3-dioxolane and ethylene carbonate, purchased from Macklin Company.

Measure 15mL of 2-methyl-1,3-dioxolane and 5mL of ethylene carbonate and mix well; According to _{the mass ratio of PEO:LiClO 4} of 1:0.4, weigh 1g of PEO and _{0.4g of LiClO 4} ; press lithium silicon The alloy Li ₂₁ Si ₅ accounts for 5% of the total mass of the powder. Weigh _{74 mg of Li 21} Si ₅ powder; add PEO, LiClO ₄ and Li ₂₁ Si ₅ powder to the above 2-methyl-1,3-dioxolane and In the mixed organic solvent of ethylene carbonate, the mixture was continuously stirred for 12 hours and then poured on a clean polytetrafluoroethylene board, and then dried at a temperature of 60°C for 12 hours to obtain PEO _{with lithium-silicon alloy Li 21} Si _{5 added.} Based composite polymer electrolyte.

The composite polymer electrolyte prepared in Example 7 was assembled with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode to form an all-solid-state lithium metal battery. The cycle performance at 45° C. and 0.2 C is shown in FIG. 5.

Example 8

Polymer electrolyte: Polypropylene carbonate (PPC) powder, purchased from Macklin Company, with an average molecular weight of 50,000.

Organic solvents: 1,3-dioxolane and dimethylformamide, purchased from Macklin Company.

Measure 5mL of 1,3-dioxolane and 5mL of dimethylformamide and mix well; according to the mass ratio of PPC:LiTFSI of 1:0.2, weigh PPC 1g and LiTFSI 0.2g; according to the lithium silicon alloy Li ₂₁ Si ₅ _{Weigh out 63 mg of Li 21} Si ₅ powder in a proportion of 5% of the total mass of the powder; add PPC, LiTFSI and Li ₂₁ Si ₅ powder to the above-mentioned mixed organic solvent of 1,3-dioxolane and propylene carbonate, and continue to stir After 12 hours, it was poured on a clean polytetrafluoroethylene board, and then dried at a temperature of 60°C for 12 hours to obtain a PCC-based composite polymer electrolyte _{added with a lithium-silicon alloy Li 21} Si _5.

The composite polymer electrolyte prepared in Example 8 was assembled with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode to form an all-solid-state lithium metal battery. The first discharge capacity was 132.5mAh g ^-1 at 30°C and 0.2C. After 50 cycles Its capacity is 110 mAh g ^-1 , and the capacity retention rate is 83%.

Example 9

Polymer electrolyte: polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) powder, purchased from Macklin Company, containing 12% hexafluoropropylene.

Organic solvents: 1,3-dioxolane 5mL, dimethylformamide 5mL, purchased from Macklin Company.

Measure 5 mL of 1,3-dioxolane and 5 mL of dimethylformamide; according to the mass ratio of PVDF-HFP:LiTFSI of 1:0.3, weigh 1g of PVDF-HFP and 0.3g of LiTFSI; according to the lithium silicon alloy Li ₂₁ Si ₅ accounts for 5% of the total mass of the powder. Weigh _{68 mg of Li 21} Si ₅ powder; add PVDF-HFP, LiTFSI and Li ₂₁ Si ₅ powder to the above mixed solvent, continue to stir for 12 hours, and then pour it on a clean poly Si The vinyl fluoride board was dried at 60°C for 12 hours to obtain a PVDF-HFP-based composite polymer electrolyte _{added with lithium-silicon alloy Li 21} Si _5.

The composite polymer electrolyte prepared in Example 9 was assembled with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode to form an all-solid-state lithium metal battery. The first discharge capacity was 140.3mAh g ^-1 at 30°C and 0.2C. After 50 cycles Its capacity is 124.3 mAh g ^-1 , and the capacity retention rate is 88.5%.

Comparative example 1

A method for preparing a polymer electrolyte material includes the following steps:

Measure 10mL each of DOL and DME and mix them uniformly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO, and 0.4g of LiTFSI. Add the powder of PEO and LiTFSI to the above-mentioned mixed organic solvent of DOL and DME, and continue to stir for 12h Then it was poured on a clean polytetrafluoroethylene board, and then dried at a temperature of 60° C. for 12 hours to obtain a PEO-based polymer electrolyte.

The method for testing the ionic conductivity versus temperature curve in Example 1 is the same. The relationship between the conductivity and temperature of the composite polymer electrolyte prepared in Comparative Example 1 in a wide temperature range is shown in Figs. 2 and 3.

Comparative example 2

Filler: pure silicon powder, powder particle size 1μm, purchased from Aladdin Company. The powder was processed using the same ball milling process as in Example 1.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh PEO 1g and LiTFSI 0.4g; weigh 74mg of silicon powder based on the proportion of silicon powder to 5% of the total mass of the powder; Add PEO, LiTFSI and silicon powder to the above-mentioned mixed organic solvent of DOL and DME, continue to stir for 12h, pour it on a clean PTFE board, and then dry it at 60℃ for 12h, that is, the added PEO-based composite polymer electrolyte of silicon powder.

The method of testing the ionic conductivity versus temperature curve in Example 1 is the same. The relationship between the conductivity and temperature of the composite polymer electrolyte prepared in Comparative Example 2 in a wide temperature range is shown in FIG. 2.

Comparative example 3

Filler: Silica powder, powder particle size 1μm, purchased from Aladdin Company. The powder was processed using the same ball milling process as in Example 1.

Measure 10mL each of DOL and DME and mix them evenly; according to the mass ratio of PEO:LiTFSI of 1:0.4, weigh 1g of PEO and 0.4g of LiTFSI; weigh the dioxide according to the proportion of silica powder to 5% of the total mass of the powder Silicon powder 74mg; add PEO, LiTFSI and silicon powder to the above-mentioned mixed organic solvent of DOL and DME, keep stirring for 12h, pour it on a clean PTFE board, and then dry it at 60℃ for 12h, that is The PEO-based composite polymer electrolyte added with silica powder was obtained.

The method of testing the ionic conductivity versus temperature curve in Example 1 is the same. The relationship between the conductivity and temperature of the composite polymer electrolyte prepared in Comparative Example 3 in a wide temperature range is shown in FIG. 2.

Figure 1 is a cross-sectional high-resolution scanning electron micrograph of the composite polymer electrolyte material prepared in Example 1; Figure 2 is a different lithium alloy and other inorganic materials prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, and 3 The electrical conductivity of the filler composite polymer electrolyte versus temperature; Figure 3 shows the electrical conductivity of the composite polymer electrolyte prepared in Examples 1, 4, 5 and Comparative Example 1 as a function of the Li ₂₁ Si ₅ filler content Graph; Figure 4 is a graph showing the charge-discharge cycle performance of a lithium symmetrical battery prepared using the composite polymer electrolyte prepared in Example 6; Cycle performance graph of all solid-state lithium metal battery assembled with metal anode.

The above embodiments show the effect of the lithium alloy composite technology route used in the present invention on polymer-based solid electrolytes from four aspects: different polymer solid electrolyte substrates, different lithium salts, different lithium alloy fillers, and different organic solvent components. The improvement of electrochemical performance has a wide range of universality and effectiveness. At the same time, it is confirmed that the method of using lithium alloys to construct a lithium-rich artificial solid electrolyte interface is important for realizing the rapid transfer of lithium ions in the polymer electrolyte, and finally realizing the polymer The improvement of electrolyte ionic conductivity is unique.

specific:

Figure 2 compares the variation curves of the ionic conductivity of polymer solid electrolytes with different lithium alloy fillers as a function of temperature. It can be seen from the figure that, compared to Comparative Example 1, the ion conductivity of the polymer solid electrolyte composited with a variety of lithium alloy fillers is significantly improved at different temperatures. For example, at 30°C, the ionic conductivity of the composite polymer electrolytes of Examples 1, 2, and 3 are 3.92×10 ^-5 S cm ^-1 , 2.72×10 ^-5 S cm ^-1 , and 1.80×10 ^-5 S, respectively cm ^-1 , which are several times higher than the ionic conductivity of Comparative Example 1 at 6.89×10 ^-6 S cm ^-1. This shows that different lithium alloy fillers have universal applicability for the modification of polymer solid electrolytes. Comparing Example 1 with Comparative Examples 2, 3, it can be seen that the ionic conductivity of Example 1 is higher than that of Comparative Examples 2 and 3 (7.55×10 ^-6 S cm ^-1 and 9.42×10 respectively). ^-6 S cm ^-1 ) is several times higher, which indicates that the polymer solid electrolyte composited with lithium alloy fillers has a significant advantage in improving ionic conductivity compared with other fillers. This difference and particularity comes from the lithium-rich artificial solid electrolyte interface formed by the interaction between the lithium alloy and the polymer electrolyte.

As a preference, the test results of the full battery assembled in Example 1 show that the composite polymer electrolyte has high ionic conductivity and can achieve long-cycle stability with a higher capacity under the test conditions given in Example 1. sex.

Examples 1, 4, and 5 compare the ionic conductivity of polymer electrolytes composited with different lithium alloy contents at different temperatures with Comparative Example 1, as shown in FIG. 3. It can be seen that the lithium alloy composite polymer electrolyte has a significant effect on improving its ionic conductivity within a wide range of lithium alloy content filling.

Example 6 uses two lithium alloy composite polymer electrolytes. After being assembled with lithium metal to form a symmetric battery, the symmetric battery remains stable within 500 cycles under set conditions, as shown in Figure 4, which proves that one or The polymer electrolyte compounded by a variety of lithium alloy fillers can realize the cycle of the battery and remain stable during the cycle. At the same time, the all-solid-state lithium metal battery of this embodiment can also maintain good cycle stability.

Comparing the test results of Example 7 and the results of Example 1, it can be seen that the combination of different lithium salts and different solvents mentioned in the content of the invention can assemble an all-solid-state lithium metal battery with excellent cycle performance, indicating that the lithium alloy The composite polymer electrolyte solution has universal applicability to different lithium salts and different solvents in the preparation process, as shown in Figure 5.

From the test results of Examples 8 and 9, it can be seen that the technical route of the lithium alloy composite polymer electrolyte is applicable to different polymer electrolyte materials, and the all-solid-state lithium metal battery prepared by it has better performance under the given test conditions. High capacity and better cycle stability.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, etc. made without departing from the spirit and principle of the present invention Simplified, all should be equivalent replacement methods, and they are all included in the protection scope of the present invention.

Claims

A composite polymer solid electrolyte material, which is characterized in that it is prepared from the following components:

Polymer electrolyte, lithium salt, filler and organic solvent; the filler is a lithium alloy; the lithium salt is a lithium salt used in a lithium ion battery;

The organic solvent includes more than one of 1,3-dioxolane or 2-methyl-1,3-dioxolane;

The general formula of the lithium alloy is Li x M, where M is a metal or non-metal element, x≥1, and x is the atomic ratio of Li/M; the lithium alloy is one or more of Li x M.
The composite polymer solid electrolyte material according to claim 1, wherein:

In the lithium alloy, M is Si, Ge or Sn.
The composite polymer solid electrolyte material according to claim 2, wherein the lithium alloy is at least one of Li 21 Si 5 , Li 21 Ge 5 , and Li 21 Sn 5 .
The composite polymer solid electrolyte material according to claim 1, wherein the lithium salt is one or more of lithium perchlorate, lithium hexafluorophosphate or lithium bistrifluoromethanesulfonimide;

The polymer electrolyte is at least one of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polycarbonate, polyvinylidene fluoride and their copolymers.
The composite polymer solid electrolyte material according to claim 1, wherein the mass of the filler accounts for 1%-30% of the total mass of the polymer electrolyte, the lithium salt and the filler;

The mass ratio of the polymer electrolyte to the lithium salt is 1:0.1 to 1:0.8;

The organic solvent also includes an auxiliary solvent, and the auxiliary solvent is an ether or ester organic solvent,

The volume-to-mass ratio of the organic solvent to the polymer electrolyte is (15-30) mL:1g.
The composite polymer solid electrolyte material according to claim 5, wherein the auxiliary solvent is one of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate or dimethylformamide above.
The method for preparing a composite polymer solid electrolyte material according to any one of claims 1 to 6, characterized in that it comprises the following steps:

1) Mix the filler, polymer electrolyte and lithium salt uniformly in an organic solvent to obtain a mixture;

2) The mixture is formed into a film to obtain a composite polymer electrolyte material.
The method for preparing a composite polymer solid electrolyte material according to claim 7, wherein the organic solvent is a main solvent and an auxiliary solvent; the main solvent is 1,3-dioxolane or 2-methyl- One or more of 1,3-dioxolane; the auxiliary solvent is an ether or ester organic solvent; the volume ratio of the auxiliary solvent to the main solvent is 0.1:1 to 5:1;

The film formation specifically refers to pouring the mixture on a substrate, drying at 60°C to 100°C for 6 hours to 24 hours in an anhydrous and oxygen-free environment, and peeling off to obtain a film material.
The application of the composite polymer solid electrolyte material according to any one of claims 1 to 6, wherein the composite polymer solid electrolyte is used in the field of ion conductors or lithium ion batteries.
A lithium ion battery, characterized in that it comprises a positive electrode, a negative electrode and a solid electrolyte placed between the positive and negative electrodes, and the solid electrolyte is the composite polymer solid electrolyte material according to any one of claims 1 to 6.