CN117878405A

CN117878405A - Electrochemical device and electronic device

Info

Publication number: CN117878405A
Application number: CN202410009897.8A
Authority: CN
Inventors: 刘建禹; 张珊; 唐超
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2024-01-03
Filing date: 2024-01-03
Publication date: 2024-04-12

Abstract

The application provides an electrochemical device and an electronic device. The electrochemical device comprises electrolyte, a separation film, a positive electrode plate and a negative electrode plate, wherein the electrolyte comprises a compound shown in a formula (I), and the mass percentage of the compound shown in the formula (I) is A% which is more than or equal to 30 and less than or equal to 80 based on the mass of the electrolyte; the isolating film comprises a porous substrate and a porous coating layer arranged on at least one side of the porous substrate, and the porosity of the isolating film is 25-35%. According to the application, the separation membrane structure and the electrolyte component are regulated and combined, and the synergistic effect of the separation membrane structure and the electrolyte component improves the OCPD cycle performance of the electrochemical device.

Description

Electrochemical device and electronic device

Technical Field

The present disclosure relates to the field of electrochemical technology, and in particular, to an electrochemical device and an electronic device.

Background

Electrochemical devices, such as lithium ion batteries, have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, good safety and the like, and are widely applied to various fields of portable electric energy storage, electronic equipment, electric automobiles and the like. With the rapid development of application of lithium ion batteries in the fields of consumer terminals and the like, the performance requirements of the market on the lithium ion batteries are also higher and higher, such as OCPD (one cylce per day) cycle performance. The testing process of the circulation performance simulates the use habit of the client, and is closer to a real use scene. However, the OCPD cycling process requires higher requirements for lithium ion batteries, and the OCPD cycling performance of existing lithium ion batteries is not ideal. Therefore, how to improve the OCPD cycle performance of the lithium ion battery is a technical problem to be solved.

Disclosure of Invention

An object of the present application is to provide an electrochemical device and an electronic device to improve OCPD (one cylce per day) cycle performance of the electrochemical device. The specific technical scheme is as follows:

a first aspect of the present application provides an electrochemical device comprising an electrolyte, a separator, a positive electrode sheet, and a negative electrode sheet, wherein the electrolyte comprises a compound represented by formula (I):

R ₁₁ and R is ₁₂ Each independently selected from C substituted or unsubstituted with fluorine ₁ To C ₁₀ Alkyl of R ₁₁ And R is ₁₂ At least one of which is substituted with fluorine; based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is A, and A is more than or equal to 30 and less than or equal to 80; the isolating film comprises a porous substrate and a porous coating layer arranged on at least one side of the porous substrate, and the porosity of the isolating film is 25-35%. The isolating membrane has lower porosity, can ensure that the electrochemical device has higher mechanical strength, and is favorable for reducing the probability of internal short circuit of the electrochemical device in the actual working condition process, thereby improving the safety performance of the electrochemical device. However, a lower porosity of the separator reduces the storage space of the electrolyte, reduces the retention amount of the electrolyte, and makes the battery poweredThe electrolyte is easy to be lost, so that a transmission channel of lithium ions between the anode and the cathode is not smooth, the transmission of the lithium ions is influenced, and further the OCPD cycle performance of the electrochemical device is influenced. The compound shown in the formula (I) has strong oxidation resistance, so that the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte is delayed, and the OCPD cycle performance of the electrochemical device can be improved while the safety performance of the electrochemical device is ensured.

In some embodiments of the present application, 40.ltoreq.A.ltoreq.75. The value of A is regulated within the range, so that the effect of the compound shown in the formula (I) is exerted, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is further reduced, the loss rate of the electrolyte is delayed, and the OCPD cycle performance of the electrochemical device is further improved while the safety performance of the electrochemical device is ensured.

In some embodiments of the present application, the separator has a porosity of 25% to 30%. The isolating film has lower porosity, can ensure that the electrochemical device has higher mechanical strength, and is favorable for further reducing the probability of internal short circuit of the electrochemical device in the actual working condition process, thereby being favorable for further improving the safety of the electrochemical device.

In some embodiments of the present application, the compound of formula (I) includes at least one of the following compounds:

in the electrochemical device, the electrolyte comprises the compound shown in the formula (I) in the range, and the effect of the compound shown in the formula (I) can be better exerted, so that the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the loss efficiency of the electrolyte is delayed, and the OCPD cycle performance of the electrochemical device is improved while the safety performance of the electrochemical device is ensured.

In some embodiments of the present application, the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60. The non-fluorinated carboxylic ester of the type is further introduced into the electrolyte, and the mass percentage content B% of the non-fluorinated carboxylic ester is regulated and controlled within the range, so that the electrolyte has proper viscosity, the wettability of an anode interface and a cathode interface is improved, polarization is reduced, and the safety performance of an electrochemical device is ensured, and meanwhile, the OCPD cycle performance of the electrochemical device is improved.

In some embodiments of the present application, the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10. The cyclic carbonate is further introduced into the electrolyte, and the mass percent C% of the cyclic carbonate is regulated and controlled within the range, so that the dissociation of lithium salt is facilitated, the conductivity of the electrolyte is improved, the film formation of lithium salt anions is facilitated, the solvation structure of the electrolyte is regulated, the stability of an anode interface and a cathode interface is enhanced, and the safety performance of an electrochemical device is ensured and the OCPD cycle performance of the electrochemical device is improved.

In some embodiments of the present application, the electrolyte comprises a tri-nitrile compound comprising at least one of 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile, or 1,2, 3-tris (2-cyanoethoxy) propane; based on the mass of the electrolyte, the mass percentage of the tri-nitrile compound is D.ltoreq.D.ltoreq.3. The electrolyte is further introduced with the tri-nitrile compound of the type and the mass percent D% of the tri-nitrile compound is regulated and controlled within the range, so that the stability of the positive electrode interface can be further enhanced, and the safety performance of the electrochemical device is ensured and the OCPD cycle performance of the electrochemical device is improved.

In some embodiments of the present application, the porous coating has a coated surface density of 0.1mg/1540.25mm ² To 10mg/1540.25mm ² . By regulating the coating surface density of the porous coating within the above range, the isolating film can have lower porosity, and higher binding force is formed between the isolating film and the positive electrode plate and between the isolating film and the negative electrode plate, so that the thickness of the electrochemical device is reduced, the safety performance of the electrochemical device is ensured, the electrochemical device has good OCPD (optical clear resist) cycle performance, and the volume energy density of the electrochemical device is improved.

In some embodiments of the present application, the porous coating layer includes inorganic particles and a fluorine-containing binder, and the mass ratio of the inorganic particles to the fluorine-containing binder is m, 1.ltoreq.m.ltoreq.2, based on the mass of the porous coating layer. By regulating the mass ratio m of the inorganic particles to the fluorine-containing binder within the above range, the separator, the positive electrode sheet and the negative electrode sheet can have higher binding force while the effects of the inorganic particles and the fluorine-containing binder are exerted, the thickness of the electrochemical device is reduced, the separator is ensured to have proper porosity, the safety performance of the electrochemical device is ensured, the electrochemical device has good OCPD (optical power distribution) cycle performance, and the volume energy density of the electrochemical device is improved.

In some embodiments of the present application, the inorganic particles comprise at least one of magnesium hydroxide, boehmite, or aluminum oxide, the fluorine-containing binder comprises a polyvinylidene fluoride-based binder, and the polyvinyl fluoride-based binder comprises at least one of polyvinylidene fluoride or a polyvinylidene fluoride-hexafluoropropylene copolymer. The inorganic particles of the above kind are selected to improve the high temperature resistance and heat shrinkage resistance of the separator and enhance the mechanical strength of the separator, thereby being beneficial to improving the safety performance of the electrochemical device on the basis that the electrochemical device has good OCPD cycle performance. The fluorine-containing binder of the type is selected, so that the affinity of the electrode pole piece to the electrolyte can be improved, and the wettability of the electrolyte to the electrode pole piece can be improved, thereby ensuring the safety performance of the electrochemical device and being beneficial to improving the OCPD cycle performance of the electrochemical device.

In some embodiments of the present application, the inorganic particles are magnesium hydroxide, and the excellent flame retardant property thereof can further improve the high temperature resistance and heat shrinkage resistance of the separator, and enhance the mechanical strength of the separator, thereby being beneficial to further improving the safety performance of the electrochemical device on the basis that the electrochemical device has good OCPD cycle performance.

A second aspect of the present application provides an electronic device comprising the electrochemical device provided in the first aspect of the present application. The electrochemical device provided by the application has good OCPD cycle performance, so that the electronic device provided by the application has longer service life and good performance.

The beneficial effects of this application:

the application provides an electrochemical device and an electronic device. The electrochemical device comprises electrolyte, a separation film, a positive electrode plate and a negative electrode plate, wherein the electrolyte comprises a compound shown in a formula (I), and the mass percentage of the compound shown in the formula (I) is A% which is more than or equal to 30 and less than or equal to 80 based on the mass of the electrolyte; the isolating film comprises a porous substrate and a porous coating layer arranged on at least one side of the porous substrate, and the porosity of the isolating film is 25-35%. The isolating membrane has lower porosity, can ensure that the electrochemical device has higher mechanical strength, and is favorable for reducing the probability of internal short circuit of the electrochemical device in the actual working condition process, thereby improving the safety of the electrochemical device. However, the lower porosity of the isolating membrane can reduce the storage space of the electrolyte, reduce the liquid retention amount of the electrolyte, and enable the electrolyte to be easily lost, so that a transmission channel of lithium ions between the anode and the cathode is not smooth, the transmission of the lithium ions is affected, and further the OCPD cycle performance of the electrochemical device is affected. The compound shown in the formula (I) has strong oxidation resistance, so that the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte is delayed, and the OCPD cycle performance of the electrochemical device can be improved while the safety performance of the electrochemical device is ensured.

Of course, not all of the above-described advantages need be achieved simultaneously in practicing any one of the products or methods of the present application.

Detailed Description

The following description of the technical solutions in the embodiments of the present application will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments obtained based on the present application by a person skilled in the art are within the scope of the protection of the present application.

In the specific embodiment of the present application, the present application is explained using a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.

Compared with the conventional cycle performance test, the full charge and full discharge standing process is added in the OCPD cycle performance test process, so that the stability requirements on the positive electrode interface and the negative electrode interface of the electrochemical device are higher. However, the existing electrochemical devices have poor stability of the positive electrode interface and the negative electrode interface, so that the cycle performance of the OCPD cannot reach an ideal level. Based on this, the present application provides an electrochemical device and an electronic device.

R ₁₁ And R is ₁₂ Each independently selected from C substituted or unsubstituted with fluorine ₁ To C ₁₀ Alkyl of R ₁₁ And R is ₁₂ At least one of which is substituted with fluorine. In some embodiments of the present application, R ₁₁ And R is ₁₂ Each independently selected from the following groups substituted or unsubstituted with fluorine: methyl groupEthyl or propyl, R ₁₁ And R is ₁₂ At least one of which is substituted with fluorine. Based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is A.ltoreq.A.ltoreq.80, preferably 40.ltoreq.A.ltoreq.75; the separator includes a porous substrate and a porous coating layer provided on at least one side of the porous substrate, and has a porosity of 25% to 35%, preferably 25% to 30%. For example, a may be 30, 40, 43, 50, 56, 60, 64, 70, 75, 80 or a range of any two of the foregoing values. For example, the porosity of the separator may be 25%, 27%, 27.5%, 29%, 30%, 31%, 33%, 35% or a range of any two of the above values.

According to the porous isolating membrane, the porous coating is arranged on at least one side of the porous isolating membrane substrate, the porosity of the isolating membrane is regulated and controlled within the range, the isolating membrane has lower porosity, the electrochemical device can be ensured to have higher mechanical strength, the probability of internal short circuit of the electrochemical device in the actual working condition process is reduced, and therefore the safety performance of the electrochemical device is improved. However, the lower porosity of the isolating membrane can reduce the storage space of the electrolyte, reduce the liquid retention amount of the electrolyte, and enable the electrolyte to be easily lost, so that a transmission channel of lithium ions between the anode and the cathode is not smooth, the transmission of the lithium ions is affected, and further the OCPD cycle performance of the electrochemical device is affected. According to the application, the compound shown in the formula (I) is introduced into the electrolyte and the mass percent A% of the compound is regulated and controlled within the range, so that the oxidation resistance of the compound shown in the formula (I) is high, the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the deletion rate of the electrolyte is delayed, and the OCPD (optical clear-cut) cycle performance of the electrochemical device is improved. Therefore, the above-described separator and the electrolyte including the compound represented by formula (I) are applied to an electrochemical device, and the OCPD cycle performance of the electrochemical device can be improved while ensuring the safety performance of the electrochemical device. When the porosity of the separator is too small, for example, less than 25%, the transmission path of lithium ions is insufficient, thereby being disadvantageous in improving the OCPD cycle performance of the electrochemical device. When the porosity of the isolating membrane is too large, for example, more than 35%, the isolating membrane is unstable in structure and poor in mechanical strength, cannot resist the puncture of particles on the surface of the electrode plate, and is easy to cause local positive and negative electrode short circuit, so that serious self-discharge is caused, and the safety performance of the electrochemical device is influenced. When A is too small, for example, less than 30, the content of the compound represented by the formula (I) is too low, the effect of enhancing the stability of the positive electrode interface is limited, and the effects of reducing the electrolyte consumption rate and delaying the electrolyte deficiency rate are also poor, thereby being unfavorable for improving the OCPD cycle performance of the electrochemical device. When A is too large, for example, more than 80, an excessively high content of the compound represented by formula (I) may cause an increase in impedance of the electrochemical device and increase in polarization, thereby adversely improving OCPD cycle performance of the electrochemical device. In the application, the isolating films with different porosities can be obtained by regulating and controlling the coating surface density, thickness or formula composition of the porous coating.

in the electrochemical device, the electrolyte comprises the compound shown in the formula (I) in the range, and the effect of the compound shown in the formula (I) can be better exerted, so that the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte is delayed, and the OCPD cycle performance of the electrochemical device is improved while the safety performance of the electrochemical device is ensured.

In some embodiments of the present application, the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60. For example, B may be 10, 20, 24, 30, 36, 40, 50, 58, 60 or a range of any two of the foregoing values. The compound shown in the formula (I) has high viscosity, so that the electrolyte has poor wettability to a positive electrode interface and a negative electrode interface. The non-fluorinated carboxylic ester is similar to the compound shown in the formula (I) in structure, has good affinity and small viscosity, and the non-fluorinated carboxylic ester is further introduced into the formula (I) and the mass percent B% of the non-fluorinated carboxylic ester is regulated and controlled in the range, so that the electrolyte has proper viscosity, the wettability of an anode interface and a cathode interface is improved, polarization is reduced, and the safety performance of an electrochemical device is ensured, and the OCPD cycle performance of the electrochemical device is improved.

In some embodiments of the present application, the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10. For example, C may be 0, 2, 3.5, 4, 6, 6.4, 8, 10 or a range of any two of the foregoing values. The compound shown in the formula (I) has poorer dissociation on lithium salt, the cyclic carbonate of the type is further introduced on the basis of the compound shown in the formula (I) and the mass percent C% of the cyclic carbonate is regulated and controlled within the range, so that the dissociation of the lithium salt is facilitated, the conductivity of electrolyte is improved, the anion film formation of the lithium salt is facilitated, the solvation structure of the electrolyte is regulated, the stability of an anode interface and a cathode interface is enhanced, and the safety performance of an electrochemical device is ensured and the OCPD cycle performance of the electrochemical device is improved.

In some embodiments of the present application, the electrolyte comprises a tri-nitrile compound comprising at least one of 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile, or 1,2, 3-tris (2-cyanoethoxy) propane; based on the mass of the electrolyte, the mass percentage of the tri-nitrile compound is D.ltoreq.D.ltoreq.3. For example, D may be 1, 1.4, 1.8, 2, 2.4, 2.8, 3 or a range of any two of the foregoing values. The tri-nitrile compound can be complexed with high-valence metal ions in the positive electrode active material to stabilize the positive electrode interface, the tri-nitrile compound of the type is further introduced on the basis of the compound shown in the formula (I) and the mass percent D% of the tri-nitrile compound is regulated and controlled in the range, so that the stability of the positive electrode interface can be further enhanced, the safety performance of an electrochemical device is ensured, and the OCPD cycle performance of the electrochemical device is improved.

In this application, the electrolyte also includes other organic solvents and other additives. The kind of the other organic solvents is not particularly limited in the present application, as long as the objects of the present application can be achieved. For example, the number of the cells to be processed, other organic solvents may include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), methyl Ethyl Carbonate (MEC), fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate at least one of trifluoromethyl ethylene carbonate, gamma-butyrolactone, decalactone, valerolactone, caprolactone, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. Other additives may include, but are not limited to, at least one of succinonitrile, adiponitrile, 1, 3-propane sultone, vinyl sulfate, vinylene carbonate.

In some embodiments of the present application, the sum of the mass percentages of other organic solvents and other additives is E.ltoreq.E.ltoreq.40, based on the mass of the electrolyte. For example, E may be 0, 10, 15, 20, 23, 25, 30, 37, 35, 40 or a range of any two of the foregoing values.

In the present application, the electrolyte further includes a lithium salt, and the kind of the lithium salt is not particularly limited as long as the object of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato borate, or lithium difluorophosphate. Preferably, the lithium salt comprises lithium hexafluorophosphate.

In some embodiments of the present application, the mass percent of lithium salt is F%, 10.ltoreq.F.ltoreq.20, based on the mass of the electrolyte. For example, F may be 10, 12, 12.5, 14, 15, 16, 18, 20 or a range of any two of the foregoing values.

In some embodiments of the present application, the electrolyte may include a lithium salt, a compound of formula (I), a cyclic carbonate, other organic solvents, and other additives. The mass percentages of the lithium salt, the compound of formula (I), the cyclic carbonate, other organic solvents and other additives are as described above. The electrochemical device comprising the electrolyte has good OCPD cycle performance.

In some embodiments of the present application, the electrolyte may include any one of a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents and other additives, and a non-fluorinated carboxylate, a tri-nitrile compound. The mass percentages of lithium salt, compound of formula (I), cyclic carbonate, other organic solvents and other additives, non-fluorocarboxylic acid ester, and tri-nitrile compound are as described above. The electrochemical device comprising the electrolyte has good OCPD cycle performance.

In some embodiments of the present application, the electrolyte may include lithium salts, compounds of formula (I), cyclic carbonates, non-fluorocarboxylates, tri-nitrile compounds, other organic solvents, and other additives. The mass percentage of the compound shown in the formula (I) is 30-79%, the mass percentage of the non-fluorinated carboxylic ester is 10-59%, and the mass percentage of the lithium salt, the cyclic carbonate, the tri-nitrile compound, other organic solvents and other additives are as described above. The electrochemical device comprising the electrolyte has good OCPD cycle performance.

In some embodiments of the present application, the porous coating has a coated surface density of 0.1mg/1540.25mm ² To 10mg/1540.25mm ² Preferably, the porous coating has a coating surface density of 2.5mg/1540.25mm ² To 5mg/1540.25mm ² . For example, the porous coating may have a coating surface density of 0.1mg/1540.25mm ² 、2mg/1540.25mm ² 、2.5mg/1540.25mm ² 、4mg/1540.25mm ² 、5mg/1540.25mm ² 、5.7mg/1540.25mm ² 、6mg/1540.25mm ² 、7.4mg/1540.25mm ² 、8mg/1540.25mm ² 、10mg/1540.25mm ² Or a range of any two values recited above. By regulating the coating surface density of the porous coating within the range, the isolating film can have lower porosity, so that the electrochemical device is ensured to have higher mechanical strength, the probability of internal short circuit of the electrochemical device in the actual working condition process is reduced, and the safety performance of the electrochemical device is improved. Meanwhile, the separator, the positive pole piece and the negative pole piece have higher cohesive force, and the thickness of the electrochemical device is reduced, so that the electrochemical device has good OCPD (optical clear diode) cycle performance and the volume energy density of the electrochemical device is improved while the safety performance of the electrochemical device is ensured.

In some embodiments of the present application, the porous coating layer includes inorganic particles and a fluorine-containing binder, and the mass ratio of the inorganic particles to the fluorine-containing binder is m, 1.ltoreq.m.ltoreq.2, based on the mass of the porous coating layer. For example, m may be 1, 1.2, 1.4, 1.6, 1.8, 2 or a range of any two of the foregoing values. The compound shown in the formula (I) has higher viscosity, so that the electrolyte has poorer wettability to the electrode plate. The fluorine-containing binder in the porous coating can improve the affinity of the electrode plate to the electrolyte and improve the wettability of the electrolyte to the electrode plate, thereby being beneficial to improving the OCPD cycle performance of the electrochemical device. The inorganic particles in the porous coating can improve the high temperature resistance and heat shrinkage resistance of the isolating film and strengthen the mechanical strength of the isolating film, thereby being beneficial to improving the safety performance of the electrochemical device on the basis that the electrochemical device has good OCPD cycle performance. By regulating the mass ratio m of the inorganic particles to the fluorine-containing binder within the above range, the separator, the positive electrode plate and the negative electrode plate can have higher binding force while the effects of the inorganic particles and the fluorine-containing binder are exerted, the thickness of the electrochemical device is reduced, the separator is ensured to have proper porosity, and the electrochemical device is ensured to have good OCPD (optical power distribution) cycle performance and the volume energy density of the electrochemical device.

In some embodiments of the present application, the inorganic particles comprise at least one of magnesium hydroxide, boehmite, or aluminum oxide, preferably magnesium hydroxide. The inorganic particles of the above kind are selected to improve the high temperature resistance and heat shrinkage resistance of the separator and enhance the mechanical strength of the separator, thereby being beneficial to improving the safety performance of the electrochemical device on the basis that the electrochemical device has good OCPD cycle performance. When the inorganic particles are magnesium hydroxide, the excellent flame retardant property of the inorganic particles can further improve the high temperature resistance and the heat shrinkage resistance of the isolating film, and the mechanical strength of the isolating film is enhanced, so that the safety performance of the electrochemical device is further improved on the basis that the electrochemical device has good OCPD (organic light-emitting diode) cycle performance.

In some embodiments of the present application, the fluorine-containing binder comprises a polyvinylidene fluoride-based binder, and the polyvinyl fluoride-based binder comprises at least one of polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer. The compound shown in the formula (I) has higher viscosity, so that the electrolyte has poorer wettability to the electrode plate. By selecting the fluorine-containing binder of the type, the affinity of the electrode plate to the electrolyte can be improved, and the wettability of the electrolyte to the electrode plate can be improved, so that the safety performance of the electrochemical device is ensured, and the OCPD cycle performance of the electrochemical device is improved.

The porous coating of the present application may also include a wetting agent and an auxiliary binder. The inorganic particles may be 25 to 70% by mass, the fluorine-containing binder may be 20 to 60% by mass, the wetting agent may be 5 to 10% by mass, and the auxiliary binder may be 5 to 15% by mass, based on the mass of the porous coating layer. The types of the wetting agent and the auxiliary binder are not particularly limited in the present application, as long as the objects of the present application can be achieved. For example, the wetting agent may include, but is not limited to, at least one of dimethyl siloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer, or dioctyl sodium sulfosuccinate, and the auxiliary binder may include, but is not limited to, ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, or butadiene, or a homopolymer or copolymer obtained by polymerization of at least one of the above monomers.

The porous substrate of the separator is not particularly limited as long as the object of the present application can be achieved. For example, the material of the porous substrate may include, but is not limited to, at least one of polyethylene, polypropylene, polytetrafluoroethylene-based polyolefin-based films, polyester films (e.g., polyethylene terephthalate (PET) films), cellulose films, polyimide films, polyamide films, spandex or aramid films, and the like. The type of porous substrate may include, but is not limited to, at least one of a woven film, a nonwoven film (nonwoven), a microporous film, a composite film, a rolled film, a spun film, or the like. In the present application, the thickness of the porous substrate is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the porous substrate may be 3 μm to 30 μm. In the present application, the size of the pore diameter of the porous substrate is not particularly limited as long as the object of the present application can be achieved, for example, the pore diameter may be 0.01 μm to 1 μm.

The positive electrode sheet is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In the present application, the positive electrode active material layer may be provided on one surface of the positive electrode current collector in the thickness direction thereof, or may be provided on both surfaces of the positive electrode current collector in the thickness direction thereof. The "surface" here may be the entire region of the positive electrode current collector or may be a partial region of the positive electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.

The present application is not particularly limited as long as the object of the present application can be achieved. For example, it may include, but is not limited to, aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum carbon composite current collector). The thicknesses of the positive electrode current collector and the positive electrode active material layer are not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 6 μm to 12 μm, and the thickness of the positive electrode active material layer is 30 μm to 120 μm. The thickness of the positive electrode sheet is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the positive electrode sheet is 50 μm to 250 μm.

The positive electrode active material layer of the present application includes a positive electrode active material including a substance capable of reversibly intercalating and deintercalating active ions such as lithium ions. The positive electrode active material layer may be one or more layers, and each of the multiple positive electrode active material layers may contain the same or different positive electrode active materials. The positive electrode active material is not particularly limited as long as the object of the present application can be achieved, and for example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganate (e.g., NCM811, NCM622, NCM523, NCM 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO) ₂ ) At least one of lithium manganate, lithium iron manganese phosphate or lithium titanate. The chemical formula of the lithium-rich manganese-based material is LiMnO.LiMO, and M can comprise Ni, co or Mn. In this application, the surface of the positive electrode active material may be attached with a substance having a composition different from that of the positive electrode active material, and illustratively, the surface-attached substance may include, but is not limited to, at least one of alumina, silica, titania, zirconia, magnesia, calcia, boria, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate, lithium carbonate, calcium carbonate, magnesium carbonate, or carbon. By attaching the above substances to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, thereby improving the electrochemistry The service life of the device.

The positive electrode active material layer may further include a positive electrode conductive agent and a positive electrode binder, the kinds of which are not particularly limited as long as the objects of the present application can be achieved, and for example, the positive electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropylcellulose, diacetylcellulose, polyvinylchloride, carboxylated polyvinylchloride, polyvinylfluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon; the positive electrode conductive agent may include, but is not limited to, at least one of a carbon-based material, a metal-based material, or a conductive polymer. Illustratively, the carbon-based material may include at least one of natural graphite, artificial graphite, conductive carbon black (Super P), or carbon fiber, and the metal-based material may include, but is not limited to, at least one of metal powder, metal fiber, copper, nickel, aluminum, or silver; the conductive polymer may include, but is not limited to, a polyphenylene derivative. The mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in the positive electrode active material layer is not particularly limited, and may be selected according to actual needs as long as the purposes of the present application can be achieved.

The negative electrode sheet is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In the present application, the anode active material layer may be provided on one surface in the anode current collector thickness direction, or may be provided on both surfaces in the anode current collector thickness direction. The "surface" here may be the entire region of the negative electrode current collector or may be a partial region of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.

The negative electrode current collector is not particularly limited as long as the object of the present application can be achieved. For example, it may include, but is not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector (e.g., carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.), and the like. In the present application, the thicknesses of the anode current collector and the anode active material layer are not particularly limited as long as the object of the present application can be achieved, for example, the anode current collector has a thickness of 6 μm to 12 μm and the anode active material layer has a thickness of 30 μm to 150 μm. In the present application, the thickness of the negative electrode tab is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode tab is 50 μm to 350 μm.

The anode active material layer of the present application includes an anode active material, the anode active material layer may be one or more layers, and each of the multiple anode active material layers may contain the same or different anode active materials. The negative electrode active material is any substance capable of reversibly intercalating and deintercalating active ions such as lithium ions. The negative electrode active material may include, but is not limited to, graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO _x (0.5 < x < 1.6), li-Sn alloy, li-Sn-O alloy, sn, snO, snO ₂ Spinel structured lithiated TiO ₂ -Li ₄ Ti ₅ O ₁₂ At least one of Li-Al alloy and metallic lithium.

The anode active material layer in the present application may further include an anode binder and an anode conductive agent, or the anode active material layer may further include an anode binder, an anode conductive agent, or a thickener. The types of the negative electrode binder and the negative electrode conductive agent are not particularly limited as long as the object of the present application can be achieved, and for example, the negative electrode binder may include, but is not limited to, at least one of the positive electrode binders described above, and the negative electrode conductive agent may include, but is not limited to, at least one of the positive electrode conductive agents described above. The kind of the thickener is not particularly limited as long as the object of the present application can be achieved, and for example, the thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or carboxymethyl cellulose.

The electrochemical device of the present application further includes a package for accommodating the positive electrode tab, the separator, the negative electrode tab, and the electrolyte, and other components known in the art in the electrochemical device, and the present application is not particularly limited. The packaging bag is not particularly limited, and may be a packaging bag known in the art as long as the object of the present application can be achieved. For example, an aluminum plastic film package may be used.

The electrochemical device of the present application is not particularly limited, and may include any device in which an electrochemical reaction occurs. In some embodiments of the present application, the electrochemical device may include, but is not limited to: lithium ion batteries, sodium ion batteries, lithium polymer electrochemical devices, lithium ion polymer electrochemical devices, and the like.

The process of preparing the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited, and may include, for example, but not limited to, the following steps: sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, winding and folding the positive electrode plate, the isolating film and the negative electrode plate according to the need to obtain an electrode assembly with a winding structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain an electrochemical device; or sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, fixing four corners of the whole lamination structure by using adhesive tapes to obtain an electrode assembly of the lamination structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain the electrochemical device. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the package as needed, thereby preventing the pressure inside the electrochemical device from rising and overcharging and discharging.

A second aspect of the present application provides an electronic device comprising an electrochemical device according to any one of the preceding embodiments of the present application. The electrochemical device provided by the application has good OCPD cycle performance, so that the electronic device provided by the application has longer service life and good performance.

The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. For example, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a hand-held cleaner, a portable CD, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash, a camera, a household large-sized battery, and a lithium ion capacitor.

Examples

Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. The various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "parts" and "%" are mass references.

Test method and apparatus:

testing of the porosity of the separation film

Determination of pore size distribution and porosity of solid Material according to national Standard GB/T21650.1-2008 mercury porosimetry and gas adsorption, part 1: mercury porosimetry test the porosity of the separator.

Testing of the coating surface Density of porous coating

After discharging the lithium ion batteries of each example and comparative example to 3.0V at 0.5C, the separator was disassembled, and after cleaning impurities on the surface of the separator with dimethyl carbonate (DMC), the separator was dried at 60℃ to obtain a test sample of the separator. Punching area of S mm on test sample of isolating film ² The mass of the small disc is weighed and is recorded as m ₁ Then stripping the porous coating on one side of the small disc to obtain the quality of the small disc after stripping the porous coating, which is marked as m ₂ Coating area density of porous coating = (m ₁ -m ₂ )/S。

Testing of OCPD cycle Performance

The test temperature was adjusted to a constant temperature of 25 ℃. The lithium ion battery is charged to 4.48V at a constant current of 0.5C, then charged to 0.05C at a constant voltage of 4.48V, kept stand for 12h, then discharged to 3.0V at a constant current of 0.2C, kept stand for 5h, and the total time is 24h, and the first cycle is recorded as the discharge capacity of the first cycle. And (3) carrying out charge and discharge cycles on the lithium ion battery according to the method, recording the discharge capacity of each cycle until the discharge capacity of the lithium ion battery is reduced to 80% of the discharge capacity of the first cycle, and recording the number of charge and discharge cycles, namely the number of OCPD cycles at 25 ℃.

Testing of pass rate of 1h hot box at 135 DEG C

The lithium ion battery was charged to 4.48v at a constant current of 0.7C and charged to 0.05C at a constant voltage of 4.48v at 25 ℃. And (3) placing the lithium ion battery in a high-temperature box, heating to 135 ℃ at a temperature rise rate of 5+/-2 ℃/min, then keeping for 1h, and recording the voltage, the temperature and the change of the temperature of the hot box of the lithium ion battery. The lithium ion battery passes the test without ignition, explosion and smoking. 10 lithium ion batteries were prepared according to the preparation methods of the respective examples and comparative examples, and tested according to the above methods, and the number of lithium ion batteries passing the test was recorded. The safety performance is characterized by the passing rate of a heat box at 135 ℃ for 1h, and the higher the number of the lithium ion batteries is tested, the better the safety performance is.

Example 1-1

< preparation of isolation Membrane >

A porous polyethylene film (supplied by Celgard corporation) having a thickness of 5 μm was used as the porous substrate;

inorganic particle magnesium hydroxide, fluorine-containing binder polyvinylidene fluoride (weight average molecular weight mw=1.3×10 ⁶ ) Dimethyl siloxane (CH) as wetting agent ₃ ) ₂ SiO and auxiliary binder acrylonitrile are mixed according to the mass ratio of 51:34:10:5, deionized water is added as a solvent, and the mixture is stirred uniformly to form porous coating slurry with the solid content of 12 wt%. Coating a porous substrate with a porous coating slurry having a coating surface density of 3.3mg/1540.25mm on one surface ² And forming a porous coating layer on one surface of the porous substrate after drying. And coating the porous coating slurry on the other surface of the porous substrate at the same coating surface density, and drying to obtain the isolating film with the porous coating on both surfaces. Wherein the porosity of the isolating film is 30%, and the mass ratio of the inorganic particles to the fluorine-containing binder is m=1.5.

< preparation of electrolyte >

In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF ₆ ) And (3) uniformly mixing the compound shown in the formula (I) and the compound shown in the formula (I-3) to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percentage of the compound of the formula (I-3) is 12.5%, the mass percentage A% is 30%, and the rest is the basic solvent.

< preparation of Positive electrode sheet >

LiCoO as positive electrode active material ₂ Positive electrode conductive agent conductive carbon black (Super P), positive electrode binder polyvinylidene fluoride (PVDF, mw=7×10) ⁶ ) Mixing according to the mass ratio of 97.5:1:1.5, adding N-methyl pyrrolidone (NMP) as a solvent, and stirring uniformly under the action of a vacuum stirrer to obtain the anode slurry with the solid content of 75 wt%. And uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 10 mu m, drying at the temperature of 85 ℃, and cold pressing to obtain the positive electrode plate with the single-sided coating thickness of the positive electrode active material layer with the thickness of 50 mu m. And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating positive electrode active material layer. And then cutting and welding the aluminum tab of the positive electrode tab to obtain the positive electrode tab with the specification of 74mm multiplied by 851mm for standby.

< preparation of negative electrode sheet >

Artificial graphite as a negative electrode active material, a negative electrode conductive agent Super P, and carboxymethyl cellulose as a thickener (CMC-Na, mw=7x10) ⁵ ) Negative electrode binder styrene-butadiene rubber (SBR, mw=5×10 ⁶ ) Mixing according to the mass ratio of 97.5:1:0.5:1, adding deionized water as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the cathode slurry with the solid content of 50 wt%. Uniformly coating the negative electrode slurry on one surface of a negative electrode current collector copper foil with the thickness of 8 mu m, drying at 85 ℃, and cold pressing to obtain a negative electrode with the single-sided coating thickness of 60 mu mAnd a negative electrode sheet of the electrode active material layer. And repeating the steps on the other surface of the copper foil to obtain the negative electrode plate with the double-sided coating negative electrode active material layer. And then cutting and welding the nickel tab of the negative electrode tab to obtain the negative electrode tab with the specification of 76mm multiplied by 867mm for standby.

< preparation of lithium ion Battery >

And stacking and winding the prepared negative electrode plate, the separator and the positive electrode plate in sequence to obtain the electrode assembly with a winding structure. And placing the electrode assembly in an aluminum plastic film packaging bag, drying, injecting electrolyte, and performing vacuum packaging, standing, formation (0.3C constant current charging to 3.5V, and then 1C constant current charging to 3.9V), capacity, degassing, trimming and other procedures to obtain the lithium ion battery.

Examples 1-2 to 1-5

The procedure of example 1-1 was repeated except that the mass percentage A% of the compound of formula (I-3) was adjusted in accordance with Table 1 in < preparation of electrolyte >. When the mass percentage A% of the compound of formula (I-3) is changed, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC and the mass percentage of the lithium salt are unchanged.

Examples 1 to 6 to 1 to 9

The procedure of examples 1 to 3 was repeated except that the coating surface density of the porous coating layer and the porosity of the separator were adjusted as shown in Table 1 in < preparation of separator >.

Examples 1 to 10 to 1 to 12

The procedure of examples 1 to 3 was repeated except that the type of the compound represented by the formula (I) was changed as shown in Table 1 in the < preparation of electrolyte >.

Example 2-1

The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.

< preparation of electrolyte >

Uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and other organic solvents diethyl carbonate (DEC) according to the mass ratio of 10:10:80 in an argon atmosphere glove box with the water content of less than 10ppm to obtain a base solventThen adding lithium hexafluorophosphate (LiPF) as a lithium salt to the base solvent ₆ ) And uniformly mixing the compound shown in the formula (I) with the non-fluorinated carboxylic ester propyl propionate shown in the formula (I-3) to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 65%, the mass percent B% is 10%, and the rest is the basic solvent.

Example 2-2

The procedure of example 2-1 was repeated, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of the propyl propionate were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percentage of the compound of formula (I-3) a% and the mass percentage of the propyl propionate B% were varied, the mass ratio of EC, PC, DEC, the mass percentage of the base solvent, and the mass percentage of the lithium salt were unchanged.

Examples 2 to 3

< preparation of electrolyte >

In an argon atmosphere glove box with the water content being less than 10ppm, uniformly mixing a compound shown in a formula (I) in a formula (I-3) and propyl non-fluorinated carboxylate propionate according to a mass ratio of 30:57.5, and then adding lithium salt lithium hexafluorophosphate (LiPF ₆ ) And (5) after uniformly mixing, obtaining the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percent of the (B) is 12.5%, and the rest is the compound of the formula (I-3) and propyl propionate.

Examples 2 to 4 to 2 to 5

The procedure of example 2-2 was repeated except that the type of the non-fluorocarboxylic acid ester was changed as shown in Table 2 in the following description of the electrolyte preparation.

Examples 2 to 6

< preparation of electrolyte >

In an argon atmosphere glove box having a water content of less than 10ppm, a cyclic carbonate Ethylene Carbonate (EC),The preparation method comprises the steps of uniformly mixing cyclic carbonate Propylene Carbonate (PC) and other organic solvents diethyl carbonate (DEC) according to a mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF) as a lithium salt into the base solvent ₆ ) And uniformly mixing the compound shown in the formula (I) with the compound shown in the formula (I-3) and the tri-nitrile compound 1,3, 6-hexanetrinitrile to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 50%, the mass percent D% is 1%, and the balance is the base solvent.

Examples 2 to 7 to 2 to 8

The procedure of examples 2 to 6 was followed except that the content of 1,3, 6-hexanetrinitrile in mass% D% was adjusted in accordance with Table 2. When the mass percentage D% of the 1,3, 6-hexanetrinitrile is changed, the mass percentage of the basic solvent is changed, and the mass ratio of EC, PC, DEC, the mass percentage of the lithium salt and the mass percentage A% of the compound of formula (I-3) are unchanged.

Examples 2 to 9

< preparation of electrolyte >

In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF ₆ ) The electrolyte is obtained after the compound shown in the formula (I) is uniformly mixed with the compound shown in the formula (I-3), the non-fluorinated carboxylic ester propyl propionate and the tri-nitrile compound 1,3, 6-hexanetrinitrile. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 49%, the mass percent C% is 25%, the mass percent D% of the 1,3, 6-hexanetrinitrile is 1%, and the rest is the basic solvent.

Examples 2 to 10 to 2 to 11

The procedure of examples 2 to 9 was repeated, except that the mass percentage A% of the compound of the formula (I-3) and the mass percentage D% of 1,3, 6-hexanetrinitrile were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percentage of the compound of formula (I-3) a% and the mass percentage of 1,3, 6-hexanetrinitrile D% were varied, the mass ratio of EC, PC, DEC, the mass percentage of the base solvent, the mass percentage of the lithium salt, and the mass percentage of the propyl propionate B% were unchanged.

Examples 2 to 12

The procedure of examples 2 to 10 was repeated except that the types of the tri-nitrile compounds were adjusted in accordance with Table 2 in < preparation of electrolyte >.

Examples 2 to 13

< preparation of electrolyte >

In an argon atmosphere glove box with the water content being less than 10ppm, uniformly mixing a compound shown in a formula (I) in a formula (I-3) and non-fluorinated carboxylic ester propyl propionate according to a mass ratio of 50:37.5, and then adding lithium salt lithium hexafluorophosphate (LiPF ₆ ) And (5) after uniformly mixing, obtaining the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percent of the (B) is 12.5%, and the rest is the compound of the formula (I-3) and propyl propionate.

Example 3-1

Except at<Preparation of a separator film>In the above, inorganic particle magnesium hydroxide and polyvinylidene fluoride (weight average molecular weight mw=1.3×10 ⁶ ) Dimethyl siloxane (CH) as wetting agent ₃ ) ₂ SiO and acrylonitrile as auxiliary binder were mixed in a mass ratio of 42.5:42.5:10:5, and the rest was the same as in examples 1 to 3 except that the mass ratio of the inorganic particles to the fluorine-containing binder was m=1.

Example 3-2

Except at<Preparation of a separator film>In the above, inorganic particle magnesium hydroxide and polyvinylidene fluoride (weight average molecular weight mw=1.3×10 ⁶ ) Dimethyl siloxane (CH) as wetting agent ₃ ) ₂ SiO and auxiliary binder acrylonitrile are mixed according to the mass ratio of 56.6:28.4:10:5, so that inorganic particles are bonded with fluorine-containing particlesThe mass ratio of the agents was the same as in examples 1 to 3 except that m=2.

Examples 3-3 to 3-4

The procedure of examples 1-3 was repeated except that the parameters were adjusted as shown in Table 3 in < preparation of a separator >.

Comparative example 1 and comparative example 2

The procedure of examples 1 to 3 was repeated except that the coating surface density of the porous coating layer and the porosity of the separator were adjusted in < preparation of separator >.

Comparative example 3

The procedure of example 1-1 was repeated except that the electrolyte was prepared.

< preparation of electrolyte >

In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF ₆ ) And (5) uniformly mixing to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF ₆ The mass percentage of the solvent is 12.5 percent, and the rest is basic solvent.

Comparative examples 4 to 5

The procedure of example 1-1 was repeated except that the mass percentage A% of the compound of formula (I-3) was adjusted in accordance with Table 1 in < preparation of electrolyte >. When the mass percentage of the compound of formula (I-3) is A%, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC and the mass percentage of the lithium salt are unchanged.

The preparation parameters and performance parameters of each example and comparative example are shown in tables 1 to 3.

TABLE 1

Note that: the "\" in table 1 indicates that there is no corresponding parameter. Taking the 135 ℃ 1h hot box pass rate data of examples 1-3 in table 1 as an example, 8/10 means that 8 lithium ion batteries among 10 lithium ion batteries pass the hot box test, other examples are understood by analogy.

As can be seen from examples 1-1 to 1-12 and comparative examples 1 to 5, the lithium ion battery of the examples of the present application has a larger number of OCPD cycles at 25 ℃ and a higher heat box passing rate at 135 ℃ for 1h by adding the compound of formula (I) to the electrolyte, with the mass percentage a% of the compound of formula (I) being within the scope of the present application, and providing a porous coating layer on at least one side of the porous substrate in the separator, with the porosity of the separator being within the scope of the present application. Indicating that the cycle performance and the safety performance of the OCPD of the lithium ion battery are good. Whereas the porosity of the separator of the lithium ion batteries of comparative examples 1 and 2 is not within the scope of the present application; the lithium ion battery of comparative example 3, in which the compound represented by formula (I) was not included in the electrolyte; the lithium ion batteries of comparative example 4 and comparative example 5, in which the mass percent A% of the compound shown in formula (I) in the electrolyte is not within the scope of the application, the lithium ion batteries of comparative examples 1 to 5, the cycle number of OCPD at 25 ℃ is smaller, the heat box passing rate at 135 ℃ for 1h is lower, show that the cycle performance and the safety performance of the OCPD of the lithium ion batteries are poorer.

The mass percent A% of the compound of formula (I) generally affects the OCPD cycle performance and safety performance of lithium ion batteries. As can be seen from examples 1-1 to 1-5 and comparative examples 3 to 5, when a is too small, for example, comparative examples 3 and 4, the compounds of formula (I) exert limited effects, and the number of OCPD cycles at 25 ℃ of the lithium ion battery is smaller; when A is too large, for example, comparative example 5, too much of the compound of formula (I) causes the impedance of the lithium ion battery to increase, the polarization increases, and the number of OCPD cycles at 25℃is smaller. Indicating that the OCPD cycling performance of the lithium ion battery is worse. When A is within the scope of this application, it is advantageous to work with the compounds of formula (I) and lithium ion batteries have a greater number of OCPD cycles at 25 ℃. Indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The porosity of the separator typically affects the OCPD cycling performance and safety performance of the lithium ion battery. As can be seen from examples 1 to 3, examples 1 to 6 to examples 1 to 9, and comparative examples 1 to 2, when the porosity of the separator is too small, for example, comparative example 1, the transmission path of lithium ions in the lithium ion battery is insufficient, so that the number of OCPD cycles at 25 ℃ of the lithium ion battery is smaller; when the porosity of the separator is too large, for example, comparative example 2, the separator is unstable in structure, poor in mechanical strength, and serious in self-discharge problem, the cycle number of the OCPD at 25 ℃ of the lithium ion battery is smaller, and the passing rate of the hot box at 135 ℃ for 1h is lower. Indicating that the OCPD cycle performance and safety performance of the lithium ion battery are worse. When the porosity of the separator is within the scope of the present application, the lithium ion battery has a greater number of OCPD cycles at 25 ℃. Indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The type of compound of formula (I) generally affects the OCPD cycle performance and safety performance of lithium ion batteries. It can be seen from examples 1-3, examples 1-10 to examples 1-12 that when the electrolyte of the lithium ion battery includes the compound represented by formula (I) within the scope of the present application, the effect of the compound represented by formula (I) is advantageously exerted, and the lithium ion battery has a large number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

TABLE 2

Note that: the "\" in table 2 indicates that there is no corresponding parameter. Taking the 135 ℃ 1h hot box pass rate data of examples 1-3 in table 2 as an example, 8/10 means that 8 lithium ion batteries among 10 lithium ion batteries pass the hot box test, other examples are understood by analogy.

The mass percent B% of non-fluorinated carboxylic esters generally affects the OCPD cycling performance and safety performance of lithium ion batteries. As can be seen from examples 1-3 and examples 2-1 to 2-2, when the electrolyte of the lithium ion battery comprises the compound shown in formula (I) and the cyclic carbonate, and the non-fluorinated carboxylate is further introduced and the mass percentage content B% is regulated to be within the scope of the application, the lithium ion battery has a larger number of OCPD cycles at 25 ℃, which indicates that the OCPD cycle performance of the lithium ion battery is good. The electrolyte is low in viscosity, the non-fluorinated carboxylic ester is further introduced into the electrolyte, and the mass percentage content B% of the electrolyte is regulated and controlled within the range of the application, so that the problem of high viscosity of the compound shown in the formula (I) can be solved, the electrolyte is provided with proper viscosity, wettability of an anode interface and a cathode interface is improved, polarization is reduced, and therefore the lithium ion battery is provided with good OCPD (optical clear-cut) cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The nature of the non-fluorinated carboxylic acid esters generally affects the OCPD cycling performance and safety performance of lithium ion batteries. It can be seen from examples 1-3, 2-2, and 2-4 to 2-5 that when the electrolyte of the lithium ion battery includes the compound represented by formula (I) and the cyclic carbonate, the non-fluorinated carboxylate is further introduced, and the non-fluorinated carboxylate within the scope of the present application is selected, the lithium ion battery has a larger number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. The non-fluorinated carboxylic ester is further introduced into the electrolyte, so that the problem of high viscosity of the compound shown in the formula (I) can be solved, the electrolyte has proper viscosity, wettability of an anode interface and a cathode interface is improved, polarization is reduced, and therefore the lithium ion battery has good OCPD cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The mass percent D% of the tri-nitrile compound generally affects the OCPD cycling performance and safety performance of the lithium ion battery. As can be seen from examples 1-3, examples 2-6 to examples 2-8, when the electrolyte of the lithium ion battery comprises the compound shown in formula (I) and the cyclic carbonate, and the tri-nitrile compound is further introduced and the mass percentage content D% is regulated within the scope of the application, the lithium ion battery has a larger number of OCPD cycles at 25 ℃, which indicates that the OCPD cycle performance of the lithium ion battery is good. The electrolyte is characterized in that the tri-nitrile compound can stabilize the positive electrode interface, the tri-nitrile compound is further introduced into the electrolyte, and the mass percent content D% of the electrolyte is regulated and controlled within the range of the application, so that the stability of the positive electrode interface can be further enhanced, and the lithium ion battery has good OCPD cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

As can be seen from examples 1-3, examples 2-9 to examples 2-11, when the electrolyte of the lithium ion battery comprises the compound represented by formula (I) and the cyclic carbonate, the non-fluorinated carboxylate and the tri-nitrile compound are further introduced, and the lithium ion battery has a larger number of OCPD cycles at 25 ℃, which indicates that the OCPD cycle performance of the lithium ion battery is good. The compound shown in the formula (I) has good compatibility and additivity with cyclic carbonate, non-fluorinated carboxylic ester and tri-nitrile compound, and the combination of the substances is applied to a lithium ion battery, so that the lithium ion battery has good OCPD cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The type of tri-nitrile compound typically affects the OCPD cycling performance of a lithium ion battery. It can be seen from examples 2-10 and examples 2-12 that when the lithium ion battery selects the tri-nitrile compound within the scope of the application, the lithium ion battery has a larger number of OCPD cycles at 25 ℃, which indicates that the OCPD cycle performance of the lithium ion battery is good. This is because the tri-nitrile compound can stabilize the positive electrode interface, and the tri-nitrile compound within the scope of the present application is further introduced into the electrolyte, so that the stability of the positive electrode interface can be further enhanced, and thus the lithium ion battery can have good OCPD cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

It can be seen from examples 1 to 3, examples 2 to 3 and examples 2 to 13 that when the electrolyte of the lithium ion battery includes the compound represented by formula (I) and the non-fluorinated carbonate, but does not include the cyclic carbonate, the lithium ion battery has a large number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

TABLE 3 Table 3

Note that: taking the 135 ℃ 1h hot box pass rate data of examples 1-3 in table 3 as an example, 8/10 means that 8 lithium ion batteries among 10 lithium ion batteries pass the hot box test, other examples are understood by analogy.

The mass ratio m of inorganic particles to fluorine-containing binder generally affects the OCPD cycle performance and safety performance of lithium ion batteries. It can be seen from examples 1-3, 3-1 to 3-2 that when m is within the scope of the present application, the lithium ion battery has a large number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. The compound shown in the formula (I) in the electrolyte has high viscosity, so that the electrolyte has poor wettability to the electrode plate, and the fluorine-containing binder in the porous coating can improve the affinity of the electrode plate to the electrolyte and improve the wettability of the electrolyte to the electrode plate, so that the lithium ion battery has good OCPD (optical power distribution) cycle performance. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The kind of inorganic particles generally affects the OCPD cycle performance and safety performance of lithium ion batteries. It can be seen from examples 1-3 and examples 3-3 that when the types of the inorganic particles are within the scope of the present application, the lithium ion battery has a large number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

The type of fluorine-containing binder typically affects the OCPD cycling performance and safety performance of lithium ion batteries. It can be seen from examples 1-3 and examples 3-4 that when the types of the fluorine-containing binders are within the scope of the present application, the lithium ion battery has a large number of OCPD cycles at 25 ℃, indicating that the OCPD cycle performance of the lithium ion battery is good. Meanwhile, the lithium ion battery also has higher passing rate of a 1h hot box at 135 ℃, which indicates that the safety performance of the lithium ion battery is good.

It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or article that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or article.

In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.

The foregoing description of the preferred embodiments of the present invention is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, alternatives, and alternatives falling within the spirit and scope of the invention.

Claims

1. An electrochemical device comprises electrolyte, a separation film, a positive electrode plate and a negative electrode plate, wherein,

the electrolyte comprises a compound shown in a formula (I):

R ₁₁ and R is ₁₂ Each independently selected from C substituted or unsubstituted with fluorine ₁ To C ₁₀ Alkyl of R ₁₁ And R is ₁₂ At least one of which is substituted with fluorine;

based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is A.ltoreq.A.ltoreq.80;

the isolating membrane comprises a porous substrate and a porous coating layer arranged on at least one side of the porous substrate, wherein the porosity of the isolating membrane is 25-35%.

2. The electrochemical device according to claim 1, wherein 40.ltoreq.A.ltoreq.75.

3. The electrochemical device of claim 1, wherein the separator has a porosity of 25% to 30%.

4. The electrochemical device of claim 1, wherein the compound of formula (I) comprises at least one of the following compounds:

5. the electrochemical device of any one of claims 1 to 4, wherein the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate;

based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60.

6. The electrochemical device of any one of claims 1 to 4, wherein the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate;

based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10.

7. The electrochemical device according to any one of claims 1 to 4, wherein the electrolyte comprises a tri-nitrile compound comprising at least one of 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile, or 1,2, 3-tris (2-cyanoethoxy) propane;

Based on the mass of the electrolyte, the mass percentage of the tri-nitrile compound is D, and D is more than or equal to 1 and less than or equal to 3.

8. The electrochemical device according to any one of claims 1 to 4, wherein the porous coating layer has a coating weight per unit of 0.1mg/1540.25mm ² To 10mg/1540.25mm ² 。

9. The electrochemical device according to any one of claims 1 to 4, wherein the porous coating layer comprises inorganic particles and a fluorine-containing binder, and a mass ratio of the inorganic particles to the fluorine-containing binder is m, 1.ltoreq.m.ltoreq.2 based on a mass of the porous coating layer.

10. The electrochemical device of claim 9, wherein the inorganic particles comprise at least one of magnesium hydroxide, boehmite, or aluminum oxide, the fluorine-containing binder comprises a polyvinylidene fluoride-based binder comprising at least one of polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene copolymer.

11. The electrochemical device of claim 10, wherein the inorganic particle is magnesium hydroxide.

12. An electronic device comprising the electrochemical device of any one of claims 1 to 11.