All-solid-state battery slurry and manufacturing method of all-solid-state battery

Abstract

The invention relates to a slurry prepared from a sulfide electrolyte, a cosolvent, a binder and a lithium salt and a manufacturing method for simultaneously applying the slurry to a solid-state battery. The invention mainly aims to provide all-solid-state battery slurry with high ion transmission and low interface impedance. In the patent, the following slurry is provided to solve the problem: the cosolvent-binder slurry with good compatibility with the sulfide electrolyte, the cosolvent contains a first solvent and a second solvent, the first solvent is a non-polar or weakly polar solvent, and the second solvent is a polar solvent with large steric hindrance; the adhesive is a rubber type adhesive; and the lithium salt is an organic lithium salt.

Description

Technical Field

[0001] The invention relates to an all-solid-state battery slurry and a method for manufacturing an all-solid-state battery. Background Art

[0002] In order to apply sulfide electrolytes to all-solid-state batteries for large-scale production, pole pieces and electrolyte separators are required. The use of polymer binders is an indispensable component to prevent pole pieces from falling off and to compensate for the brittleness of the inorganic components of the pole piece active materials and electrolytes. Moreover, in the electrode active materials, the volume strain generated by stress during the cycle is relieved by the polymer binder. However, the addition of 1-2wt% of the binder seriously affects the electrochemical performance of the all-solid-state battery due to the obstruction of the transmission of Li+ at the interface. In addition, the choice of solvent is crucial for the sulfide solid-state battery system. Strong polar solvents react severely with sulfide electrolytes and decompose the sulfide electrolytes, so they should be excluded; single non-polar or weak polar solvents have good compatibility with sulfide electrolytes, but because the solvent has a low boiling point, high saturated vapor pressure, and fast solvent volatilization, it is not conducive to the large-scale preparation of pole pieces; although many research groups have proposed dry manufacturing processes, wet coating technology is still indispensable because it has the currently mature manufacturing process technology of lithium-ion batteries. Summary of the invention

[0003] The purpose of the present invention is to provide a solid-state battery slurry with low ionic resistivity and a method for manufacturing a solid-state battery, aiming to solve the problem that after the slurry-like electrode is coated with a binder, the contact area between the active material, the conductive agent and the electrolyte is small, the interfacial ion transmission is blocked, the ion conductivity is low, and the high-impedance solid electrode is formed; and the coating process technical difficulties caused by the excessive evaporation of a non-polar or weakly polar single solvent during the wet coating process. To achieve the above purpose, the slurry provided by the present invention is a sulfide electrolyte layer slurry containing a sulfide electrolyte, a co-solvent, a binder and a lithium salt. The co-solvent contains a first solvent and a second solvent, the first solvent is a non-polar or weakly polar solvent, such as one or more of toluene, alkane, and halogenated alkane solvents; the second solvent is a polar solvent, such as one or more of a chain ketone solvent, an ester solvent, a glycol ether solvent, and an amide solvent, and the boiling point of the second solvent is higher than that of the first solvent. The binder is a rubber binder that can be dissolved in a non-polar solvent, such as natural rubber (NR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS), hydrogenated styrene-butadiene block copolymer (SEBS) One or more. The lithium salt is one or more of the organic lithium salts of lithium bis(oxalate borate) (LiBOB), lithium difluorooxalate borate (LiDFOB), lithium bis(difluorosulfonyl imide) (LiFSI) and lithium bis(trifluoromethylsulfonyl imide) (LiTFSI), lithium hexafluorophosphate, and lithium tetrafluoroborate. The solid content of the above-mentioned slurry is 100 parts (weight), preferably, the first solvent is 5 parts (weight) or more, and the second solvent is the opposite. The solid content of the above-mentioned slurry is 100 parts (weight), preferably, the binder is 1-5 parts (weight). The solid content of the above-mentioned slurry is 100 parts (weight), preferably, the lithium salt is 0.05-5 parts (weight). The conductivity of the electrolyte layer is determined by coating the slurry on copper foil, drying, rolling, cutting, and assembling the electrode into a button battery for conductivity testing. In the above invention, the slurry provided by the present invention may further contain active materials and conductive agents. The all-solid-state battery is an all-solid-state half-cell and full-cell having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The solid electrolyte layer contains a first solvent and a second solvent as a co-solvent, a binder, and a lithium salt; wherein the first solvent is 5 parts (weight) or more of the solid component, the lithium salt is 1 part (weight) or more, and the binder is 2 parts (weight) or more. The manufacturing method of the all-solid-state battery, the coating process, the solid electrolyte layer is coated on the positive electrode active material layer or the negative electrode active material layer, avoiding the uneven electrolyte layer caused by the solvent volatilizing too fast during the coating process; the drying process, forming a dry coating layer; the rolling process, the positive electrode or the negative electrode is in close contact with the solid electrolyte layer.Compared with the prior art, the advantages of the present invention are: (1) By using a co-solvent, the two solvents work together to dissolve the binder and lithium salt, and have good compatibility with the solid electrolyte. The dispersion degree of the binder can be adjusted by the co-solvent ratio, avoiding the sedimentation of the electrolyte in the weak polar solvent, which is conducive to the formation of a uniform slurry; (2) The addition of lithium salt allows the ion-conducting binder to fill the pores as an interface material, increase the interface contact, and increase the physical contact between the components, thereby improving the ion transmission of the electrode and reducing the interface impedance. (3) From the manufacturing process point of view, during the coating process, the use of a co-solvent avoids the uneven electrolyte layer caused by the rapid evaporation of the solvent; the use of a first solvent with a low boiling point can maintain good manufacturing efficiency. The second solvent may have solvent residues during the drying process due to its high boiling point, which can increase the sliding of the particles and form a dense layer. DETAILED DESCRIPTION

[0004] The present invention will be described in detail below in conjunction with specific embodiments. It should be noted that the descriptions provided here are only preferred embodiments for illustrative purposes and do not limit the scope of the present invention, and it should be understood that other equivalents or improved embodiments may be obtained therefrom without departing from the spirit and scope of the present invention.

[0005] Embodiment 1: The slurry provided by the present invention is a sulfide electrolyte layer slurry containing a sulfide electrolyte, a co-solvent, a binder and a lithium salt. The co-solvent contains a first solvent and a second solvent, wherein the first solvent is a non-polar or weakly polar solvent, such as one or more of toluene, alkane, and halogenated alkane solvents; for example, p-xylene solvent, boiling point 138.5oC, saturated vapor pressure 1.2KPa (20oC); the second solvent is a polar solvent, such as one or more of chain ketone solvents, ester solvents, glycol ether solvents, and amide solvents, and the boiling point of the second solvent is higher than that of the first solvent; for example, 2,6-dimethyl-4-heptanone, boiling point 168.1 oC, saturated vapor pressure 0.27KPa (20oC). Wherein, the weight ratio of the first solvent to the second solvent is 1:9. The binder is a rubber binder that can be dissolved in a non-polar solvent, such as one or more of natural rubber (NR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS), and hydrogenated styrene-butadiene block copolymer (SEBS). The weight ratio of the binder is 2. The lithium salt is one or more of the organic lithium salts of lithium bis(oxalate borate) (LiBOB), lithium difluorooxalate borate (LiDFOB), lithium bis(difluorosulfonyl imide) (LiFSI), lithium bis(trifluoromethylsulfonyl imide) (LiTFSI), lithium hexafluorophosphate, and lithium tetrafluoroborate. The weight ratio of the lithium salt is 1. The conductivity of the electrolyte layer is determined by coating the slurry on copper foil, drying, rolling, cutting, and assembling the electrode into an indium sheet into a button battery for conductivity testing; compared with the solid electrolyte layer without adding lithium salt, the conductivity of the solid electrolyte layer with 1 part of lithium salt is significantly improved.

Claims

1. The slurry provided by the present invention is a sulfide electrolyte layer slurry containing a sulfide electrolyte, a co-solvent, a binder and a lithium salt, wherein the co-solvent contains a first solvent and a second solvent, wherein the first solvent is a non-polar or weakly polar solvent, such as one or more of toluene, alkanes, and halogenated alkanes; the second solvent is a polar solvent, such as one or more of chain ketone solvents, ester solvents, glycol ether solvents, and amide solvents, and the boiling point of the second solvent is higher than that of the first solvent.

2. The binder according to claim 1 is a rubber binder soluble in a non-polar solvent, such as one or more of natural rubber (NR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS), and hydrogenated styrene-butadiene block copolymer (SEBS).

3. The lithium salt according to claim 1 is one or more of the organic lithium salts of lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium bis(difluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium hexafluorophosphate, and lithium tetrafluoroborate.

4. According to claim 1, the solid content of the slurry is 100 parts by weight, preferably, the first solvent is 5 parts by weight or more, and the second solvent is the opposite.

5. According to claim 2, the solid content of the slurry is 100 parts by weight, and preferably, the binder is 1 part to 5 parts by weight.

6. According to claim 3, the solid content of the slurry is 100 parts by weight, and preferably the lithium salt is 0.05 parts by weight to 5 parts by weight.

7. A solid electrolyte layer is prepared according to claims 1-6, wherein the conductivity of the electrolyte layer is measured by coating the slurry on a copper foil, drying, rolling, cutting, and assembling the counter electrode into a button cell for conductivity testing.

8. An all-solid-state battery is an all-solid-state half-cell and a full-cell having a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer, wherein the solid electrolyte layer contains a first solvent and a second solvent as a co-solvent, a binder and a lithium salt.

9. The all-solid-state battery according to claim 8, wherein the first solvent has a solid content of 5 parts (weight) or more, the lithium salt has a solid content of 1 part (weight) or more, and the binder has a solid content of 2 parts (weight) or more.

10. The manufacturing method of the all-solid-state battery comprises a coating process, in which a solid electrolyte layer is coated on the positive electrode active material layer or the negative electrode active material layer, thereby avoiding uneven electrolyte layer caused by too fast solvent evaporation during the coating process; a drying process, in which a dry coating layer is formed; and a rolling process, in which the positive electrode or the negative electrode is in close contact with the solid electrolyte layer.