Solid-state lithium-ion batteries with composite polymer electrolytes

Abstract

The present invention relates to a solid lithium-ion battery of a composite polymer electrolyte, which is characterized in that: a positive electrode material, a negative electrode material, and a composite polymer electrolyte on the upper and lower surfaces of the negative electrode material are placed and packaged in sequence; the composite polymer electrolyte includes a polymer electrolyte matrix, a lithium salt, an inorganic compound, and a lithium ion conductive matrix, and the mixed liquid obtained by uniformly mixing them constitutes a solid composite polymer electrolyte membrane. Beneficial effects: The composite polymer electrolyte in the present invention will form a network structure through physical cross-linking, and this network structure maintains stability under certain conditions. The composite polymer electrolyte prepared by the present invention can spontaneously form a film and has high safety. Compared with other composite polymer electrolytes, the raw materials used in this method are easy to obtain, the production process can be produced on existing lithium battery production equipment, and the materials used have good electrochemical stability.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a composite polymer electrolyte solid-state lithium ion battery and a preparation method thereof. Background Art

[0002] Compared with other secondary batteries, lithium-ion batteries have the advantages of higher energy density, high output voltage and long life, and are widely used in the fields of electronic products and automobiles. With the depletion of traditional fossil energy, environmental pollution and the increasing greenhouse effect, the development of green energy is imminent. At present, the electrolytes of lithium-ion batteries are mostly liquid electrolytes, which may leak, burn, decompose or even explode during use, seriously affecting personal and property safety. As electronic devices and electric vehicles have higher requirements for the energy density and rate performance of lithium-ion batteries, the safety performance of lithium batteries becomes particularly important.

[0003] Compared with liquid electrolytes, composite polymer electrolytes have the advantages of light weight, good viscoelasticity and good film-forming properties, which can overcome the above shortcomings of liquid electrolytes and improve the safety of lithium-ion batteries. The composite polymer electrolyte matrix that is currently widely studied is polyethylene oxide, which is compounded with lithium salts to form a composite polymer electrolyte. However, polyethylene oxide is easy to crystallize at room temperature, and more chain segments are in the crystal region at room temperature and cannot participate in lithium ion transfer; therefore, the prepared composite polymer electrolyte has low ionic conductivity and weak mechanical properties, which limits its use. Generally, crystallization can be inhibited by blending, copolymerization, cross-linking, and hyperbranched structures to improve its room temperature conductivity. Among them, cross-linked and hyperbranched structure electrolytes are more complicated to prepare and have higher costs, which cannot meet the requirements of lithium battery companies. The blending and copolymerization methods are simple, which can not only improve the ionic conductivity of the composite polymer electrolyte, ensure the safety performance of the lithium-ion battery, but also reduce the production cost. In view of the above advantages, it is necessary to provide a preparation method and lithium-ion battery of a composite polymer electrolyte with excellent electrochemical properties and low price. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned technology and provide a composite polymer electrolyte solid-state lithium ion battery. The composite polymer electrolyte can form a network structure through physical cross-linking, and the network structure remains stable under certain conditions; the prepared composite polymer electrolyte can spontaneously form a film and has high safety.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a solid-state lithium-ion battery with a composite polymer electrolyte, characterized in that: it includes a positive electrode material, a negative electrode material and a composite polymer electrolyte on the upper and lower surfaces of the negative electrode material placed and packaged in sequence; the composite polymer electrolyte includes a polymer electrolyte matrix, a lithium salt, an inorganic compound and a lithium ion conductive matrix, and the mixed liquid obtained by uniformly mixing them constitutes a solid composite polymer electrolyte membrane.

[0006] The polymer electrolyte matrix is ​​one or more of PVDF, modified substances and branched polyacrylate compounds, and the polymer electrolyte matrix forms a network structure through physical cross-linking of branched structures; the amount of the polymer electrolyte matrix is ​​10%-80% of the mass of the composite polymer electrolyte.

[0007] The lithium salt of the composite polymer electrolyte is one or more of lithium bis(trifluoromethylsulfonimide), lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium trifluoromethylsulfonate; the amount of the lithium salt is 5% to 80% of the mass of the composite polymer electrolyte.

[0008] The inorganic compound of the composite polymer electrolyte includes one or more of nano silicon dioxide, nano titanium dioxide or nano aluminum oxide; the amount of the inorganic compound is 0.5%-80% of the mass of the composite polymer electrolyte.

[0009] The lithium ion conductive matrix of the composite polymer electrolyte is polyethylene glycol dimethyl ether; the amount of the lithium ion conductive matrix is ​​30-70% of the mass of the composite polymer electrolyte.

[0010] The inorganic nanoparticles of the composite polymer electrolyte have a particle size of 20-200 nm.

[0011] The composite polymer electrolyte is prepared by solution casting and doctor blade coating.

[0012] The active material in the positive electrode material is one or more of lithium iron phosphate, lithium cobalt oxide or sulfide.

[0013] The active material in the negative electrode material is one or more of metallic lithium, metallic lithium alloy, lithium titanate, graphite or silicon material.

[0014] Beneficial effects: The composite polymer electrolyte of the present invention forms a network structure through physical cross-linking, and the network structure maintains stability under certain conditions. The composite polymer electrolyte prepared by the present invention can spontaneously form a film and has high safety. Compared with other composite polymer electrolytes, the raw materials used in this method are easy to obtain, the production process can be produced on existing lithium battery production equipment, and the materials used have good electrochemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention;

[0016] Figure 2 It is a schematic diagram of the network structure of the polymer electrolyte matrix.

[0017] In the figure: 1. positive electrode material, 2. composite polymer electrolyte, 3. negative electrode material. DETAILED DESCRIPTION

[0018] The specific implementation of the present invention is described in detail below in conjunction with preferred embodiments.

[0019] As shown in the attached drawings for details, this embodiment provides a solid-state lithium-ion battery with a composite polymer electrolyte, comprising a positive electrode 1, a negative electrode material 3, and a composite polymer electrolyte 2 on the upper and lower surfaces of the negative electrode material, which are placed in sequence in two layers of combined packaging; the composite polymer electrolyte comprises a polymer electrolyte matrix, a lithium salt, an inorganic compound, and a lithium ion conductive matrix, and the mixed liquid obtained by uniformly mixing them constitutes a solid composite polymer electrolyte membrane.

[0020] See attached for details Figure 2 The polymer electrolyte matrix is ​​one or more of PVDF, modified substances and branched polyacrylate compounds, and the polymer electrolyte matrix forms a network structure through physical cross-linking of the branched structure; the amount of the polymer electrolyte matrix is ​​10%-80% of the mass of the composite polymer electrolyte.

[0021] The lithium salt of the composite polymer electrolyte is one or more of lithium bis(trifluoromethylsulfonimide), lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium trifluoromethylsulfonate; the amount of the lithium salt is 5% to 80% of the mass of the composite polymer electrolyte.

[0022] The inorganic compound of the composite polymer electrolyte includes one or more of nano silicon dioxide, nano titanium dioxide or nano aluminum oxide; the amount of the inorganic compound is 0.5%-80% of the mass of the composite polymer electrolyte.

[0023] The lithium ion conductive matrix of the composite polymer electrolyte is polyethylene glycol dimethyl ether; the amount of the lithium ion conductive matrix is ​​30-70% of the mass of the composite polymer electrolyte.

[0024] The inorganic nanoparticles of the composite polymer electrolyte have a particle size of 20-200 nm.

[0025] The composite polymer electrolyte is prepared by solution casting and doctor blade coating.

[0026] The active material in the positive electrode material is one or more of lithium iron phosphate, lithium cobalt oxide or sulfide.

[0027] The active material in the negative electrode material is one or more of metallic lithium, metallic lithium alloy, lithium titanate, graphite or silicon material.

[0028] Specific steps for preparing the present invention

[0029] 1) Dissolve polyethylene glycol dimethyl ether and lithium salt LiTFSI in acetonitrile, where the mass concentration of polyethylene glycol dimethyl ether is 10% and the mass concentration of LiTFSI is 10%; then add lithium cobalt oxide LCO used as a positive electrode active material and acetylene black and carbon nanotubes used as a conductive agent to the solution, where the mass concentration of LCO is 70%, the mass concentration of acetylene black is 5%, and the mass concentration of carbon nanotubes is 5%; stir the above materials for 2-8 hours to fully mix them to prepare slurry. Apply the slurry to both sides of 12um aluminum foil, dry it with air at 85℃ for 20 hours, and roll it up to prepare a positive electrode sheet;

[0030] 2) See attached Figure 2 PVDF-HFP was dissolved in N-methylpyrrolidone (NMP), wherein the solid content of PVDF-HFP was 10%. Polyethylene glycol dimethyl ether, nano-alumina and lithium salt LiTFSI were added to the PVDF-HFP solution and stirred for 12 hours. The different raw materials were fully dispersed, wherein the polyethylene glycol dimethyl ether accounted for 40% of the total mass, the nano-alumina accounted for 10% of the total mass, and [O] / [Li]=20. The solution prepared above was evenly coated on a tetrafluoroethylene plate by a doctor blade method, heated and dried for use, and the room temperature ionic conductivity of the obtained composite polymer electrolyte was 4.58×10 -5 S / cm;

[0031] 3) Using the prepared material as the positive electrode, the lithium sheet as the negative electrode and the prepared material as the electrolyte, the positive electrode material, the composite polymer electrolyte and the negative electrode material are stacked in sequence using a lamination manufacturing process to prepare a solid-state lithium-ion battery.

[0032] 4) According to the operation steps of 2), polyethylene glycol dimethyl ether was added in an amount of 60% of the total mass, and then a composite polymer electrolyte was prepared to obtain a composite polymer electrolyte with a room temperature ionic conductivity of 1.38×10 -4 S / cm;

[0033] 5) According to the operation steps in 3), a new solid-state lithium-ion battery is prepared using a lamination manufacturing process.

[0034] 6) Dissolve PVDF-HFP in NMP, wherein the solid content of PVDF-HFP is 10%. Add polyethylene glycol dimethyl ether, nano-alumina and lithium salt LiTFSI to the PVDF-HFP solution and stir for 12 hours to fully disperse the different raw materials, wherein polyethylene glycol dimethyl ether accounts for 60% of the total mass, nano-alumina accounts for 10% of the total mass, and [O] / [Li]=20. Apply the above prepared solution evenly on the positive electrode sheet by scraping, heat and dry for standby use;

[0035] 7) Step 6) Prepare the positive electrode sheet, which includes a positive electrode and a separator. Using the lamination manufacturing process, the positive electrode sheet and the lithium sheet are stacked in sequence to prepare another new type of solid-state lithium-ion battery.

[0036] 8) heating aluminum triisopropoxide and methoxy polyethylene glycol to react under vacuum to obtain modified nano-alumina, and replacing the nano-alumina with modified nano-alumina according to step 6) to obtain another solid-state lithium-ion battery, or replacing the nano-alumina with nano-silicon oxide according to step 6) to obtain another solid-state lithium-ion battery.

[0037]

[0038] The detailed description of the composite polymer electrolyte solid-state lithium-ion battery with reference to the above embodiment is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A solid-state lithium-ion battery with a composite polymer electrolyte, characterized in that: The positive electrode material, the negative electrode material and the composite polymer electrolyte on the upper and lower surfaces of the negative electrode material are placed and packaged in sequence; The composite polymer electrolyte is a solid composite polymer electrolyte membrane formed by mixing a polymer electrolyte matrix, a lithium salt, an inorganic compound and a lithium ion conductive matrix to obtain a mixed solution; The polymer electrolyte matrix is ​​PVDF-HFP, and the polymer electrolyte matrix forms a network structure through physical cross-linking of the branched structure; the amount of the polymer electrolyte matrix is ​​10%-80% of the mass of the composite polymer electrolyte; The lithium ion conductive matrix of the composite polymer electrolyte is polyethylene glycol dimethyl ether; the amount of the lithium ion conductive matrix is ​​30-70% of the mass of the composite polymer electrolyte.

2. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The lithium salt of the composite polymer electrolyte is one or more of lithium bis(trifluoromethylsulfonimide), lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium trifluoromethylsulfonate; the amount of the lithium salt is 5% to 80% of the mass of the composite polymer electrolyte.

3. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The inorganic compound of the composite polymer electrolyte includes one or more of nano silicon dioxide, nano titanium dioxide or nano aluminum oxide; the amount of the inorganic compound is 0.5%-80% of the mass of the composite polymer electrolyte.

4. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The inorganic nanoparticles of the composite polymer electrolyte have a particle size of 20-200 nm.

5. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The composite polymer electrolyte is prepared by solution casting and doctor blade coating.

6. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The active material in the positive electrode material is one or more of lithium iron phosphate, lithium cobalt oxide or sulfide.

7. The solid-state lithium-ion battery of the composite polymer electrolyte according to claim 1, characterized in that: The active material in the negative electrode material is one or more of metallic lithium, metallic lithium alloy, lithium titanate, graphite or silicon material.

Images