Solid-state electrolyte, plasticizer for solid-state electrolyte, and application

Abstract

The application provides a solid-state electrolyte, a plasticizer for the solid-state electrolyte and application, wherein the solid-state electrolyte is added with the plasticizer, the plasticizer can significantly reduce the crystallinity of a polymer matrix, can provide overcharge protection for a battery, can simultaneously improve the rate performance and safety performance of the battery, and can prolong the cycle service life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a solid-state electrolyte, a plasticizer for the solid-state electrolyte and applications. BACKGROUND

[0002] At present, solid-state batteries have attracted extensive attention due to their higher safety performance, lighter mass and smaller volume. Especially for bipolar batteries, the bipolar battery includes a plurality of cell units stacked in series, and the bipolar cell using electrolyte needs extremely complex packaging process in production, which also significantly increases the cost of the battery, so the bipolar battery using solid-state electrolyte gradually becomes the focus of battery manufacturers.

[0003] Among them, the polymer solid-state electrolyte has good film-forming property and has been widely used. However, the polymer solid-state electrolyte often has a problem of high crystallinity, which is not conducive to the transmission of active ions, and needs to use a plasticizer to adjust the crystallinity of the polymer solid-state electrolyte. However, even if the crystallinity of the polymer solid-state electrolyte is reduced to improve the rate performance of the battery, the bipolar battery using the solid-state electrolyte still has the problem of "easy overcharging due to the consistent difference between the plurality of cell units", which causes the cycle performance of the battery to deteriorate and also brings great safety hazards. The above problems further limit the development of solid-state bipolar batteries. Therefore, it is urgent to provide a new solid-state electrolyte. SUMMARY

[0004] In view of this, the embodiments of the present application provide a solid-state electrolyte, which adds a plasticizer, the plasticizer can not only significantly reduce the crystallinity of the polymer matrix, but also provide overcharge protection for the battery, thereby simultaneously improving the rate performance and safety performance of the battery and prolonging the cycle service life of the battery.

[0005] The first aspect of the present application provides a solid-state electrolyte, which comprises a polymer matrix, an electrolyte salt and at least one plasticizer as shown in formula (I),

[0006]

[0007] wherein R1, R2, R3, R4, R5 and R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl group, a substituted or unsubstituted cyclic alkyl group and -OR7;

[0008] wherein the R1-R6 contains one or two -OR7;

[0009] wherein the R7 is * The position marked is connected with the oxygen atom, R8, R9, R 10 , R 11each independently is at least one selected from a hydrogen atom, a halogen atom, and a linear alkyl group; and n is any integer from 1 to 10.

[0010] The maximum molecular weight of the above-mentioned plasticizer molecule (structure shown in formula (I)) is also much smaller than the polymer matrix commonly used in solid-state electrolytes, so it can be inserted between the polymer matrix, destroying the ordered arrangement of the polymer matrix, thus reducing the crystallinity of the polymer matrix, thereby improving the ionic conductivity of the solid-state electrolyte, and further improving the rate performance of the battery. More importantly, the -OR7 segment in the above-mentioned plasticizer and the benzene ring form a redox shuttle, so that the above-mentioned plasticizer molecule can effectively prevent the battery cell from overcharging, thereby improving the safety performance and cycle life of the battery. Therefore, the above-mentioned solid-state electrolyte can improve the rate performance and safety performance of the battery, and prolong the cycle life of the battery.

[0011] The second aspect of the present application provides a plasticizer for solid-state electrolyte, the structure of the plasticizer is shown in formula (I),

[0012]

[0013] wherein R1, R2, R3, R4, R5, R6 are each independently at least one selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted linear alkyl group, a substituted or unsubstituted cyclic alkyl group, and -OR7;

[0014] wherein the R1-R6 contains one or two -OR7;

[0015] wherein the R7 is * The position marked is connected to the oxygen atom, R8, R9, R 10 , R 11 each independently is at least one selected from a hydrogen atom, a halogen atom, and a linear alkyl group; and n is any integer from 1 to 10.

[0016] The third aspect of the present application provides a secondary battery, comprising a positive electrode, a negative electrode, and a solid-state electrolyte disposed between the positive electrode and the negative electrode. Since the solid-state electrolyte provided by the first aspect of the present application is used, the secondary battery has overcharge protection performance, and has high safety performance, good rate performance, and long cycle life.

[0017] The fourth aspect of the present application provides an electrical equipment comprising the battery provided by the third aspect of the present application. The above-mentioned secondary battery is used to power the electrical equipment, so the electrical equipment has good market competitiveness. DETAILED DESCRIPTION

[0018] To solve the above problems, the embodiment of the present application provides a solid-state electrolyte, comprising a polymer matrix, an electrolyte salt and at least one plasticizer as shown in formula (I),

[0019]

[0020] wherein R1, R2, R3, R4, R5, R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl, a substituted or unsubstituted cyclic alkyl and -OR7;

[0021] wherein the R1-R6 contains one or two -OR7;

[0022] wherein the R7 is * the position marked is connected with an oxygen atom, R8, R9, R 10 , R 11 are each independently selected from at least one of a hydrogen atom, a halogen atom and a chain alkyl; n is any integer in 1-10.

[0023] The above plasticizer can be inserted between the commonly used polymer matrix (for example, polyethylene oxide, abbreviated as PEO) of the solid-state electrolyte, destroying the ordered arrangement of the polymer matrix, so that the crystallinity of the polymer matrix can be significantly reduced; at the same time, the plasticizer with the above structure can also promote the dissociation of the electrolyte salt, so that the ionic conductivity of the solid-state electrolyte can be improved, and the rate performance of the battery can be improved, so that the rate performance of the battery can reach the level of the battery with the general plasticizer added for the solid-state electrolyte. And the -OR7 segment in the above plasticizer and the benzene ring constitute a redox shuttle, which can lose electrons and be oxidized at a certain voltage higher than the cutoff voltage of the battery, the benzene ring loses electrons and undergoes electronic rearrangement, and the -OR7 segment can stabilize the structure, so that the above plasticizer molecule can form a stable shuttle cation radical structure after losing electrons (for a bipolar battery containing m series-connected battery units, the cutoff voltage of the bipolar battery is U, the cutoff voltage of each battery unit is U / m, and the certain voltage higher than the cutoff voltage is U / m+ΔU); and the above shuttle cation radical can diffuse to the negative electrode end and be reduced to a redox shuttle (i.e., a plasticizer molecule as shown in formula (I)) during the charging process of the battery, and then diffuse back to the positive electrode end to be oxidized again, continuously consuming the overcharged electricity, significantly improving the safety performance and cycle life of the battery. Therefore, the above solid-state electrolyte can improve the rate performance and safety performance of the battery at the same time, and prolong the cycle life of the battery.

[0024] In the present application, in the above formula (I), n can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments of the present application, n is any positive integer from 1 to 5, i.e., n is 1, 2, 3, 4, or 5. In this way, the segment of -OR7 in the plasticizer molecule is shorter, and the steric hindrance of the plasticizer molecule is smaller, which can further ensure that the plasticizer molecule can quickly and freely diffuse between the solid electrolyte, the positive electrode, and the negative electrode, thereby ensuring that the plasticizer molecule can fully exert its overcharge protection performance, and thus the cycle performance of the battery can be further improved. In addition, it is also beneficial for the plasticizer molecule to be inserted between the polymer matrix, reducing the crystallinity of the solid electrolyte, and benefiting the rate performance of the battery.

[0025] In the present application, in formula (I), R1, R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl group, and -OR7, and one or two OR7 groups are connected to the benzene ring. It can be understood that the structure of formula (I) is that one or two H atoms on the benzene ring are replaced by -OR7 groups, and the other positions on the benzene ring are still hydrogen atoms, or the H atoms at the other positions are each independently replaced by a halogen atom, a substituted or unsubstituted chain alkyl group, or a substituted or unsubstituted cyclic alkyl group. When two -OR7 groups are present at the same time, their structures can be completely the same or different, that is, the two -OR7 groups connected to the same benzene ring can be the same or different. In the above formula (II), R8, R9, R 10 , R 11 are each independently selected from a hydrogen atom, a halogen atom, and a chain alkyl group.

[0026] In some embodiments of the present application, R7 to R 10 In the above formula (II), the chain alkyl group is a C1-C4 chain alkyl group. For example, the C1-C4 chain alkyl group is selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, or a tert-butyl group. In this way, it is beneficial to control the small molecular volume of the plasticizer molecule, so that the plasticizer molecule and the subsequent shuttle cation radical can more quickly and freely diffuse between the solid electrolyte, the positive electrode, and the negative electrode, thereby ensuring that the plasticizer molecule can fully exert its overcharge protection performance. In some embodiments of the present application, R7 to R 10 In the above formula (II), the halogen atom is selected from at least one of a fluorine atom, a chlorine atom, and a bromine atom. The above three atoms can further improve the structural stability of the shuttle cation radical, thereby benefiting the service life of the redox shuttle.

[0027] In some embodiments of the present application, formula (I) contains two -OR7 groups at the same time, i.e., the structure of formula (I) is and two -OR7s are located at ortho or para positions on the benzene ring. The -OR7s at ortho or para positions on the benzene ring can improve the stability of the above structure. When two -OR7s are contained, it is more conducive to improving the structural stability of the shuttle cation, reducing the risk of side reactions (for example, two shuttle cations combine to cause the shuttle cation to be inactivated, the shuttle cation reacts with the polymer matrix to cause the shuttle cation to be inactivated, etc.) between the shuttle cation and other substances in the battery cell, thereby prolonging the service life of the redox shuttle.

[0028] In some embodiments of the present application, the solid-state electrolyte comprises at least one plasticizer as shown in formula (A) to formula (C):

[0029]

[0030] In some embodiments of the present application, formula (I) contains only one -OR7. At this time, it is conducive to reducing the steric hindrance of the redox shuttle (plasticizer molecule) / shuttle cation radical, so as to improve the reciprocating motion of the redox shuttle / shuttle cation radical between the positive electrode and the negative electrode, and thus improve the cycle service life of the battery. It can be understood that not all plasticizer molecules can be compared using the above principle, and the size of the steric hindrance of the -OR7 and the interaction between the functional groups on the benzene ring also need to be considered. It is a comprehensive effect, which is more suitable for comparison between plasticizer molecules with a single variable.

[0031] In some embodiments of the present application, the solid-state electrolyte comprises at least one plasticizer as shown in formula (D) to formula (G):

[0032]

[0033] For the convenience of description, the groups in R1 to R6 other than -OR7 are referred to as other substituents. In some embodiments of the present application, the other substituents include substituted or unsubstituted C1-C6 linear alkyl, and in some specific embodiments, the above C1-C6 linear alkyl is selected from methyl, ethyl, propyl, isopropyl, butyl or tert-butyl. The above linear alkyl as an electron donor can stabilize the shuttle cation radical. In some embodiments of the present application, the substituents in the above substituted C1-C6 linear alkyl include but are not limited to halogen atoms, carbonyl groups, cyano groups, sulfonic acid groups, C1-C6 alkoxy groups, C6-C 12 aryl groups, C5-C 12 cycloalkyl groups. In some specific embodiments, the above halogen atoms are selected from fluorine atoms, chlorine atoms, bromine atoms. The above three atoms can further improve the structural stability of the shuttle cation radical formed by -OR7. In some specific embodiments, the above C1-C6 alkoxy groups are selected from methoxy or ethoxy. In some specific embodiments, the above C6-C 12The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl.

[0034] In the present application, when the other substituent group is selected from a hydrogen atom, R8, R9, R 10 , R 11 are each independently selected from at least one of a hydrogen atom, a halogen atom, and a chain alkyl group; when the substituent group is selected from a halogen atom, R8, R9, R 10 , R 11 are each independently selected from at least one of a hydrogen atom, a halogen atom, and a chain alkyl group; when the other substituent group is selected from a Ci-C6chain alkyl group, R8, R9, R 10 , R 11 are each independently selected from at least one of a hydrogen atom, a halogen atom, and a chain alkyl group.

[0035] In some embodiments, the substituted or unsubstituted cycloalkyl group is a substituted or unsubstituted C5-C6cycloalkyl group, which can be exemplified by cyclopentyl, cycloalkyl, and the like. The C5-C6cycloalkyl group has higher stability. In some embodiments of the present application, the substituent group of the substituted cycloalkyl group includes, but is not limited to, a halogen atom, a cyano group, a sulfonic acid group, a Ci-C6alkoxy group, a Ci-C6chain alkyl group, a C6-Ci2aryl group, and a C5-Ci2cycloalkyl group. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl. In some embodiments, the Ci-C6chain alkyl group of the substituted cycloalkyl group can be a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, or a tert-butyl group. The C5-Ci2cycloalkyl group of the substituted cycloalkyl group can be exemplified by cyclopentyl, cycloalkyl, and the like. 12 The aryl group is selected from the group consisting of phenyl, naphthyl, and biphenyl. The C5-Ci2cycloalkyl group is selected from the group consisting of cyclopentyl, cyclohexyl, and bicyclohexyl.

[0036] In some embodiments of the present application, the mass ratio of the polymer matrix, the plasticizer and the electrolyte salt in the solid-state electrolyte is (30-94):(1-35):(5-35). In some specific embodiments of the present application, the mass ratio of the polymer matrix, the plasticizer and the electrolyte salt in the solid-state electrolyte is (30-80):(10-35):(10-35). Controlling the mass ratio of the three within the above range, there are sufficient plasticizer molecules to provide overcharge protection for the battery cell, and the appropriate amount of plasticizer molecules can more fully promote the dissociation of the electrolyte salt, so that the active ion content in the solid-state electrolyte is higher, and the solid-state electrolyte also has a more appropriate crystallinity, which is beneficial to the transmission of active ions and thus the rate performance of the battery; at the same time, the solid-state electrolyte has a suitable crystallinity, which can make the mechanical strength of the solid-state electrolyte better and the stability of the internal structure of the battery cell higher. Exemplarily, the mass ratio of the polymer matrix, the plasticizer and the electrolyte salt can be (35-90):(5-35):(8-35), (40-75):(10-35):(10-35), (45-70):(15-35):(15-35), (50-60):(20-35):(20-35), etc.

[0037] The present application also provides a plasticizer for a solid-state electrolyte, and the structure of the plasticizer is shown in formula (I),

[0038]

[0039] wherein R1, R2, R3, R4, R5, R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl, a substituted or unsubstituted cyclic alkyl and -OR7;

[0040] wherein the R1-R6 contains one or two -OR7;

[0041] wherein the R7 is * The position marked is connected to an oxygen atom, R8, R9, R 10 , R 11 are each independently selected from at least one of a hydrogen atom, a halogen atom and a chain alkyl; and n is any integer from 1 to 10.

[0042] The above plasticizer can reduce the crystallinity of the polymer matrix, thereby improving the ionic conductivity of the solid-state electrolyte and thus the rate performance of the battery. More importantly, the -OR7 segment in the above plasticizer and the benzene ring form a redox shuttle, so that the above plasticizer can effectively prevent the overcharge of the battery cell and thus improve the safety performance and cycle life of the battery.

[0043] In some embodiments of the present application, the plasticizer includes, but is not limited to, one synthesized according to the following route, taking a benzene ring with one -OR7 group as an example:

[0044]

[0045] In some embodiments of the present application, the catalyst includes, but is not limited to, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, triethylamine, etc. The embodiments of the present application also provide a secondary battery including a positive electrode, a negative electrode, and the aforementioned solid-state electrolyte disposed between the positive electrode and the negative electrode. Due to the adoption of the solid-state electrolyte provided by the embodiments of the present application, the secondary battery itself has overcharge protection function, and thus has high safety performance and long cycle service life; meanwhile, the secondary battery also has good rate performance. The secondary battery itself having overcharge protection function means that the secondary battery has overcharge protection function without relying on the charging protection program set by the battery management system.

[0046] In some embodiments of the present application, the secondary battery is a bipolar battery, and specifically, the secondary battery includes a plurality of cell units stacked in series, each of the cell units including a positive electrode, a negative electrode, and the solid-state electrolyte disposed between the positive electrode and the negative electrode.

[0047] In some embodiments of the present application, the solid-state electrolyte is clamped between the positive electrode and the negative electrode.

[0048] In some embodiments of the present application, the secondary battery is a bipolar battery, and the plurality of cell units are stacked in the thickness direction of the cell units and connected in series between the cell units; the first end cell unit and the second end cell unit are respectively led out with electrode tabs in the stacking direction of the plurality of cell units, and the electrode tab of the first end and the electrode tab of the second end are opposite in polarity. In the present application, the positive electrode includes any publicly known positive electrode in the field of solid-state batteries.

[0049] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the positive electrode active material layer includes positive electrode active material, conductive agent, polymer matrix, lithium salt, and additive. In some embodiments, the mass ratio of the positive electrode active material, the conductive agent, the polymer matrix, the electrolyte salt, and the additive is (50-90):(1-10):(9-20):(0-10):(0-10).

[0050] In some embodiments of the present application, the positive active material includes at least one of lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2(wherein, A is selected from one of Co, Mn, 0 < x < 1), ternary material LiNi m M n E (1-y-z) O2(wherein, M, E are independently selected from at least one of Co, Al, Mn, and M and E are not the same, 0 < y < 1, 0 < z < 1).

[0051] In the present application, the negative electrode of the secondary battery can be any negative electrode known in the art. In embodiments of the present application, the negative electrode can include one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. The carbon-based negative electrode can include graphite, hard carbon, soft carbon, graphene, etc.; the silicon-based negative electrode can include silicon, silicon-carbon (a mixture of silicon material and carbon material), silicon-oxygen (SiO x ), silicon metal compound, etc.; the tin-based negative electrode can include tin, tin-carbon (a mixture of tin metal and carbon material), tin oxide, tin metal compound; and the lithium negative electrode can include metallic lithium or lithium alloy. The lithium alloy can be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0052] In some embodiments of the present application, the negative electrode includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector. The composition of the negative active material includes negative active material, conductive agent, polymer matrix, electrolyte salt, and additive. In the present application, the negative active material, conductive agent, and plasticizer can be materials known to those skilled in the art. In some embodiments of the present application, the negative active material includes, but is not limited to, lithium metal, lithium metal alloy, graphite, silicon, silicon monoxide, silicon-carbon composite, silicon alloy, and when the negative active material is selected from lithium metal and lithium metal alloy, the negative active material layer does not contain conductive agent, polymer matrix, lithium salt, and additive. In some embodiments, the mass ratio of the negative active material, conductive agent, polymer matrix, electrolyte salt, and additive is (50-90):(1-10):(9-20):(0-10):(0-10).

[0053] In the present application, the additives in the positive active material layer and the negative active material layer described above can be materials known to those skilled in the art, for example, but not limited to, at least one of butanedione, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide. In some specific embodiments, the additives in the positive active material and the negative active material layer described above include the aforementioned plasticizers provided by the embodiments of the present application.

[0054] In some embodiments of the present application, the conductive agent in the positive electrode and the negative electrode can each independently be selected from at least one of acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotube and Ketjen black.

[0055] In the present application, the polymer matrix described above can be a material known to those skilled in the art. For example, the polymer matrix described above can be, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), styrene butadiene rubber (SBR), nitrile rubber (NBR), lithium carboxymethyl cellulose (CMC-Li), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), ethylene oxide-propylene oxide copolymer (PEO-PO), styrene-ethylene oxide block polymer (PEO-b-PS).

[0056] In the present application, taking lithium salt as an example, the electrolyte salt described above can be selected from at least one of organic lithium salt, inorganic lithium salt, for example, at least one of LiPF6, LiBF4, LiTFSI, LiFSI, LiClO4, LiAsF6, LiBOB, LiDFOB, LiTFOP.

[0057] The embodiments of the present application also provide a power utilization device comprising the secondary battery provided by the present application.

[0058] In some embodiments of the present application, the power utilization device described above includes, but is not limited to, a power vehicle, a 3C electronic product, etc.

[0059] The technical solutions of the present application are further described in the following embodiments.

[0060] Embodiment 1

[0061] (1) Preparation of solid-state electrolyte: a polymer matrix (specifically polyethylene oxide PEO) with a molecular weight of 600,000, an electrolyte salt (specifically LiTFSI), and a plasticizer as shown in formula (A) with a mass ratio of 50:25:25 were dissolved in a solvent (specifically acetonitrile) to obtain a solution; then the solution was coated on the release surface of the release film with a doctor blade, dried at room temperature for 10 min, and then heated to 60°C for 30 min; after drying, it was peeled off from the release film to obtain a solid-state electrolyte with a thickness of 50 μm.

[0062]

[0063] (2) Preparation of positive electrode sheet: positive active material (specifically lithium iron phosphate) with a mass ratio of 78:2:10:5:5, conductive agent (specifically super p), polymer matrix (PEO with a molecular weight of 600,000), electrolyte salt (specifically LiTFSI), and plasticizer as shown in formula (A) were uniformly mixed in a solvent (specifically N,N-dimethylformamide) to obtain a positive electrode slurry, and then the positive electrode slurry was coated on the surface of the positive electrode current collector (specifically aluminum foil), and then dried at 60°C for 1 h and at 80°C for 2 h to obtain a positive electrode sheet, wherein the surface loading of lithium iron phosphate is 8 mg / cm 2 .

[0064] (3) Assembly of single cell: the positive electrode sheet prepared in step (2) above was cut into a rectangular sheet with a size of 4.5 cm x 6 cm in an argon-filled glove box (O2 content ≤0.5 ppm, H2O content ≤0.5 ppm), and a lithium-copper composite strip with a size of 4.7 cm x 6.2 cm x 15 μm was used as a negative electrode sheet, and the solid-state electrolyte prepared in step (1) was cut into a size of 4.8 cm x 6.3 cm x 50 μm, and the dry cell was obtained by stacking the positive electrode sheet, the solid-state electrolyte, and the negative electrode sheet in order.

[0065] (4) Preparation of bipolar battery: the above four identical cells were connected in series, and tabs were drawn from the outermost aluminum current collector and negative electrode sheet, respectively, and packaged into a bipolar soft pack battery using an aluminum plastic film.

[0066] Example 2

[0067] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer with the structure shown in formula (B):

[0068]

[0069] Example 3

[0070] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer of the structure shown in Formula (C):

[0071]

[0072] Example 4

[0073] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer of the structure shown in Formula (D):

[0074]

[0075] Example 5

[0076] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer of the structure shown in Formula (F):

[0077]

[0078] Example 6

[0079] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer of the structure shown in Formula (E):

[0080]

[0081] Example 7

[0082] The difference from Example 1 is that the plasticizer in the solid-state electrolyte and the positive electrode slurry is replaced by a plasticizer of the structure shown in Formula (E):

[0083]

[0084] Example 8

[0085] The difference from Example 4 is that in step (1), the mass ratio of the polymer matrix (PEO), the electrolyte salt (LiTFSI), and the plasticizer is 80:10:10.

[0086] Example 9

[0087] The difference from Example 4 is that in step (1), the mass ratio of the polymer matrix (PEO), the electrolyte salt (LiTFSI), and the plasticizer is 30:35:35.

[0088] Example 10

[0089] The difference from Example 4 is that in step (1), the mass ratio of the polymer matrix (PEO), the electrolyte salt (LiTFSI), and the plasticizer is 20:40:40.

[0090] Example 11

[0091] The difference from Example 4 is only that in step (1), the mass ratio of the polymer matrix (PEO), electrolyte salt (LiTFSI) and plasticizer is 96:1:4.

[0092] To highlight the beneficial effects of the embodiments of the present application, the following comparative examples are set.

[0093] Comparative Example 1

[0094] The difference from Example 1 is only that the solid-state electrolyte and the plasticizer in the positive electrode slurry of Example 1 are replaced by

[0095] Comparative Example 2

[0096] The difference from Example 1 is only that the composition of the solid-state electrolyte is a polymer matrix (PEO) and lithium salt (LiTFSI) with a mass ratio of 67:33. Moreover, the positive electrode slurry does not contain plasticizer.

[0097] Comparative Example 3

[0098] The difference from Example 1 is only that the solid-state electrolyte and the plasticizer in the positive electrode slurry of Example 1 are replaced by the following structure:

[0099] Battery electrochemical performance test

[0100] (1) Rate performance test: at 60°C, the batteries prepared in the above examples and comparative examples are first charged from 10V to 15.2V at a rate of 0.05C, then stand for 5 minutes, and then discharged from 15.2V to 10V at a rate of 0.05C. The above process is repeated three times. Then charge from 10V to 15.2V at a rate of 0.1C, and charge at 15.2V to 0.01C cutoff, then stand for 5 minutes, and finally discharge at rates of 0.1C, 0.2C, 0.5C and 1C to 10V, respectively. The discharge specific capacity at 0.1C and the discharge capacity retention rate at 0.2C, 0.5C and 1C relative to 0.1C are recorded. The test results are summarized in Table 1.

[0101] (2) Battery cycle performance test

[0102] The batteries prepared in the above examples and comparative examples were charged from 10 V to 15.2 V at a rate of 0.05 C at 60 °C, then rested for 5 minutes, and then discharged from 15.2 V to 10 V at a rate of 0.05 C, and the above process was repeated three times. Then the batteries were charged from 10 V to 15.2 V at a rate of 0.2 C, and charged at 15.2 V to 0.01 C cut-off, then rested for 5 minutes, and finally discharged to 10 V at a rate of 0.2 C, and finally rested for 5 minutes. The battery was considered to be invalid when the specific capacity of the battery was 80% of the initial capacity, and the cycle number at this time was recorded as the cycle life of the battery. The results are summarized in Table 1.

[0103] Table 1

[0104]

[0105] As can be seen from the data in Table 1, compared with Comparative Example 1 and Comparative Example 3, the cycle life of the battery is significantly prolonged after the conventional plasticizer is replaced with an equal amount of the plasticizer provided in the examples of the present application, and the rate performance and discharge capacity of the battery of the examples can also reach a level comparable to that of the battery of Comparative Example 1, fully demonstrating the beneficial effects of the plasticizer of the examples of the present application. In comparison with the battery without any added plasticizer (Comparative Example 2), the electrochemical performance of the battery of the examples is significantly higher.

[0106] Comparing the data between Comparative Example 4, Examples 8-9 and Examples 10-11, it can be found that the ratio of the contents of the plasticizer, the polymer matrix and the electrolyte salt also affects the electrochemical performance of the battery, and when the ratio of the above three is within the further provided range of the present application, the overall effect of the battery is better, so the person skilled in the art can select according to actual needs.

[0107] Comparing the data of Examples 1-7, it can be seen that different -OR7 groups or different numbers of functional groups also have some effect on the performance of the battery. The carbon chain of Example 4 is shorter than that of Example 6, and the steric hindrance is relatively smaller, so it is easier to move between the positive electrode and the negative electrode, and it is also easier to destroy the ordered arrangement of the polymer matrix molecules, so the cycle life and rate performance of the battery are better. Although Example 4 contains only one -OR7 group, the structural stability of the shuttle ion formed by the plasticizer molecules in Example 4 is not as good as that of Examples 1-2, and the cycle life of the redox shuttle itself in Example 4 is relatively shorter, but thanks to the smaller steric hindrance of the plasticizer molecules in Example 4, it is easier to move between the positive electrode and the negative electrode, so its cycle performance is also better.

[0108] The above describes exemplary embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, some improvements and refinements can be made, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. A solid electrolyte, characterized in that comprising a polymer matrix, an electrolyte salt and at least one plasticizer as represented by formula (I), wherein R1, R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl group, a substituted or unsubstituted cycloalkyl group, and -OR7; wherein said R1 to R6 contain one or two -OR7; Wherein, the R7 is The position marked with * is connected to the oxygen atom, R8, R9, R 10 、R 11 Each is independently selected from at least one of a hydrogen atom, a halogen atom, and a chain alkyl group; n is any integer from 1 to 10; The mass ratio of the polymer matrix, the plasticizer and the electrolyte salt is (30-94): (1-35): (5-35).

2. The solid electrolyte according to claim 1, characterized in that The n is any integer from 1 to 5.

3. The solid electrolyte according to claim 1, characterized in that The formula (I) contains two -OR7 groups, and the two -OR7 groups are located at the ortho or para position on the benzene ring.

4. The solid electrolyte according to claim 3, characterized in that The solid electrolyte includes at least one plasticizer as shown in formula (A) to formula (C):

5. The solid electrolyte according to claim 1, characterized in that The formula (I) contains one -OR7.

6. The solid electrolyte according to claim 5, characterized in that The solid electrolyte includes at least one plasticizer as shown in formula (D) to formula (G):

7. The solid electrolyte according to claim 1, characterized in that The R8~R 11 wherein the chain alkyl group is a C1-C4 chain alkyl group.

8. The solid electrolyte according to claim 7, characterized in that The C1-C4 chain alkyl group is selected from at least one of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group and a tert-butyl group.

9. The solid electrolyte according to claim 1, characterized in that The halogen atom is at least one selected from a fluorine atom, a chlorine atom, and a bromine atom.

10. The solid electrolyte according to claim 1, characterized in that Except for the -OR7, all of R1 to R6 are other substituted groups. Among the other substituted groups, the substituted or unsubstituted chain alkyl group is a substituted or unsubstituted C1-C6 chain alkyl group; the substituted or unsubstituted cycloalkyl group is a substituted or unsubstituted C3-C6 cycloalkyl group.

11. A plasticizer for solid electrolyte, characterized in that The structure of the plasticizer is shown in formula (I), wherein R1, R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted chain alkyl group, a substituted or unsubstituted cycloalkyl group, and -OR7; wherein said R1 to R6 contain one or two -OR7; Wherein, the R7 is The position marked with * is connected to the oxygen atom, R8, R9, R 10 、R 11 Each is independently selected from at least one of a hydrogen atom, a halogen atom and a chain alkyl group; and n is any integer from 1 to 10.

12. A secondary battery, characterized in that: The secondary battery includes a positive electrode, a negative electrode, and the solid electrolyte according to any one of claims 1 to 10 disposed between the positive electrode and the negative electrode.

13. The secondary battery according to claim 12, characterized in that The secondary battery includes a plurality of battery cell units stacked in series, and each of the battery cell units includes the positive electrode, the negative electrode, and the solid electrolyte disposed between the positive electrode and the negative electrode.

14. An electrical device, characterized in that: The electric device includes the secondary battery according to claim 13.

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