阅读说明：本技术 复合聚合物及其制备方法和应用 (Composite polymer and preparation method and application thereof ) 是由 李小栓 吕文彬 魏礼勇 徐赛 邓素祥 马忠龙 于 2020-03-03 设计创作，主要内容包括：本发明公开了一种复合聚合物及其制备方法和应用,所述复合聚合物为聚糠醇和聚氧化乙烯的嵌段共聚物。该复合聚合物具有较优的粘结性能和导电子和离子性能,有利于提高极片的品质和剥离力,提高电池的循环性能、倍率性能和安全性能。(The invention discloses a composite polymer, a preparation method and application thereof, wherein the composite polymer is a segmented copolymer of polyfurfuryl alcohol and polyethylene oxide. The composite polymer has excellent adhesive property and electron and ion conducting properties, is beneficial to improving the quality and the stripping force of a pole piece, and improves the cycle performance, the rate capability and the safety performance of a battery.)

1. A composite polymer, wherein the composite polymer is a block copolymer of polyfurfuryl alcohol and polyethylene oxide.

2. The composite polymer according to claim 1, wherein the composite polymer is a chain polymer or a star polymer or a dendritic polymer.

3. The composite polymer according to claim 1, wherein the molecular weight of the composite polymer is 45000-55000;

optionally, the composite polymer has a solids content of 1.2 to 18 wt%.

4. A method of preparing the composite polymer of any one of claims 1-3, comprising: the initiator, the solvent, the polyethylene oxide and the furfuryl alcohol are mixed and stirred so as to obtain the composite polymer.

5. The method according to claim 4, wherein the initiator is selected from at least one of oxalic acid, hydrochloric acid, preferably oxalic acid;

optionally, the solvent is selected from at least one of N-methylpyrrolidone, dimethylsulfoxide.

6. The method according to claim 4 or 5, wherein the mass ratio of the initiator to the solvent is 2-4: 90-98.

7. The positive electrode slurry is characterized by comprising a positive electrode active material and a glue solution, wherein the glue solution is the composite polymer as defined in any one of claims 1-3 or the composite polymer prepared by the method as defined in any one of claims 5-6.

8. The positive electrode slurry according to claim 7, wherein the solid content of the positive electrode slurry is 50 to 80 wt%;

optionally, the viscosity of the positive electrode slurry is 3000-20000 cP;

optionally, the positive electrode active material is NCM and/or NCA.

9. A lithium battery having a positive electrode sheet prepared from the positive electrode slurry according to claim 8.

10. An automobile, characterized in that it has a lithium battery as claimed in claim 9.

Technical Field

The invention belongs to the technical field of lithium batteries and application thereof, and particularly relates to a composite polymer and a preparation method and application thereof.

Background

Along with the rapid development and progress of society, the problems of energy shortage and environmental pollution become more serious day by day, and people pay more and more attention to clean energy; meanwhile, with the increasing popularization of new energy automobiles and the increasing development of energy power, people are prompted to develop lithium ion batteries with higher energy density. At present, lithium iron phosphate and ternary materials are mostly adopted for the anode of the lithium ion power battery, and along with the continuous improvement of the requirement on the energy density, the continuous improvement of the energy density on the existing battery cell design system is increasingly difficult, especially in the aspect of high-endurance electric automobiles.

In order to achieve high voltage and high energy density, an organic solvent is generally adopted as an electrolyte of a traditional liquid power battery, but the organic electrolyte contains inflammable substances, so that potential safety hazards are easily caused. Along with the increase of the size of the power battery, the use amount of the combustible organic solvent is increased, the heat radiation is increased, the battery is easier to heat, and the risk of thermal runaway of the battery is increased. The spontaneous combustion phenomenon of new energy automobiles is endless, and people try to develop safe and reliable novel batteries all the time. The all-solid-state battery can exist more stably because of not containing electrolyte components, thereby arousing general attention of people; however, the current all-solid-state battery technology is not mature, and a long way is left for industrialization. The semi-solid battery is used as an intermediate product of the liquid battery and the all-solid battery, can reduce the using amount of electrolyte in the battery core, improves the safety performance of the battery core to a certain extent, and is a transition product which is closest to the prior art and is most easy to realize mass production.

In the manufacturing process of the existing semi-solid battery, the binder commonly adopted by the anode is PVDF, and three kinds of interactions mainly exist in the electrode by the binder PVDF: the interaction between the binder and the active material particles, the interaction between the binder and the current collector, and the interaction between the binder molecules and the binder molecules. The viscosity of the binder is an important process parameter, and if the viscosity of the binder is too low, the viscosity of the prepared slurry is also low, so that the slurry has too high fluidity, is easy to settle, has poor storage stability, and needs to be additionally added with a thickening agent; however, if the viscosity of the binder is too high, the dispersion of the active material and the conductive agent is not facilitated, and the binder has no conductive function, so that the internal resistance of the battery is increased, and the performance of the battery is influenced. In order to improve the energy density and rate capability of the power battery, the content of active substances is often increased and the content of binders is reduced in the design of an electric core system. And the reduction of the using amount of the binder influences the homogenization process, so that the stability of slurry is reduced, the peeling strength of the prepared pole piece is reduced, the coating is easy to peel off from the current collector, the exertion of electrical property is influenced, and the potential safety hazard to the battery is great.

Therefore, the existing lithium battery is yet to be further improved.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, an object of the present invention is to provide a composite polymer, a method for producing the same, and use thereof. The composite polymer has excellent adhesive property and electron and ion conducting properties, is beneficial to improving the quality and the stripping force of a pole piece, and improves the cycle performance, the rate capability and the safety performance of a battery.

In one aspect of the invention, the invention provides a composite polymer, which according to an embodiment of the invention is a block copolymer of polyfurfuryl alcohol and polyethylene oxide. According to the composite polymer provided by the embodiment of the invention, the composite polymer has the characteristics of electron and ion transmission, and compared with the traditional binder material, lithium ions can be freely transmitted in the composite polymer; compared to common ionic polymers, the conductivity is increased due to pi C ═ C chemical bonds forming an electron cloud. Meanwhile, the composite polymer contains a structural part similar to the adhesive, so that the composite polymer is easier to be fully mixed with the positive active substance to form a uniform phase, and the adhesive force and the stripping force of the pole piece are improved. Furthermore, the composite polymer can be quickly gelatinized after being added with electrolyte, so that the transmission of electrons and ions in the pole piece is promoted, and meanwhile, the existence of too much electrolyte in the battery cell can be avoided, and the safety performance of the battery is further improved.

In addition, the composite polymer according to the above embodiment of the present invention may also have the following additional technical features:

in some embodiments of the invention, the composite polymer is a chain polymer or a star polymer or a dendrimer.

In some embodiments of the invention, the molecular weight of the composite polymer is 45000-55000.

In some embodiments of the invention, the composite polymer has a solids content of 1.2 to 18 wt%.

In yet another aspect of the present invention, the present invention provides a method of preparing a composite polymer, the method comprising, according to an embodiment of the present invention: the initiator, the solvent, the polyethylene oxide and the furfuryl alcohol are mixed and stirred so as to obtain the composite polymer.

According to the preparation method of the embodiment of the invention, under the action of the initiator and the solvent, furfuryl alcohol can be subjected to polymerization reaction, and the polymerized furfuryl alcohol can be reacted with polyethylene oxide to obtain a block polymer of polyfurfuryl alcohol and polyethylene oxide. Under the combined action of the polyfurfuryl alcohol and the polyethylene oxide, the composite polymer has the characteristics of electron and ion transmission, and compared with the traditional binder material, lithium ions can be freely transmitted in the composite polymer; compared to common ionic polymers, the conductivity is increased due to pi C ═ C chemical bonds forming an electron cloud. Meanwhile, the composite polymer contains a structural part similar to the adhesive, so that the composite polymer is easier to be fully mixed with the positive active substance to form a uniform phase, and the adhesive force and the stripping force of the pole piece are improved. Furthermore, the composite polymer can be quickly gelatinized after being added with electrolyte, so that the transmission of electrons and ions in the pole piece is promoted, and meanwhile, the existence of too much electrolyte in the battery cell can be avoided, and the safety performance of the battery is further improved.

In addition, the method for preparing a composite polymer according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, the initiator is selected from at least one of oxalic acid, hydrochloric acid.

In some embodiments of the invention, the solvent is selected from at least one of N-methylpyrrolidone, dimethylsulfoxide.

In some embodiments of the invention, the mass ratio of the initiator to the solvent is from 2 to 4: 90-98.

In yet another aspect of the present invention, the present invention provides a positive electrode slurry, which according to an embodiment of the present invention, is composed of a positive electrode active material and a gum solution, wherein the gum solution is the composite polymer or the composite polymer prepared by the method for preparing the composite polymer. According to the positive electrode slurry provided by the embodiment of the invention, the composite polymer has the bonding property of the binder, and can improve the compatibility of the binder and the positive active material, so that the positive active material is uniformly dispersed in the electrode plate, the bonding force and the stripping force of the electrode plate are improved, the rate cycle performance of the battery is improved, and the composite polymer also has the conductivity and ion conductivity, can be used as a carrier for lithium ion transmission, bears the action of a solvent in an electrolyte, and synergistically promotes the transmission of lithium ions in the electrode plate, and improves the rate performance of the battery. Therefore, the positive electrode slurry does not need to be additionally added with a binder and a conductive agent, and the reduction of the material components in the slurry is also beneficial to improving the consistency of the slurry, so that the quality of the battery is improved. Furthermore, the composite polymer can also improve the mechanical property of the pole piece, endow the pole piece with flexibility, effectively relieve the volume expansion of the pole piece in the charging and discharging process, keep the stability of the electrode, further improve the transmission speed of lithium ions in the pole piece and improve the multiplying power performance.

In addition, the positive electrode slurry according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, the solid content of the cathode slurry is 50 to 80 wt%.

In some embodiments of the invention, the viscosity of the positive electrode slurry is 3000-.

In some embodiments of the invention, the positive active material is NCM and/or NCA.

In yet another aspect of the present invention, the present invention provides a lithium battery having a positive electrode sheet prepared from the above positive electrode slurry according to an embodiment of the present invention. According to the lithium battery provided by the embodiment of the invention, the lithium battery is provided with the positive plate prepared by the positive slurry consisting of the positive active material and the composite polymer, and the composite polymer has the bonding property of the binder, so that the compatibility of the positive active material and the positive active material can be improved, the positive active material is uniformly dispersed in the plate, the bonding force and the stripping force of the plate are improved, the rate cycle performance of the battery is improved, and the lithium battery also has the conductive and ion-conducting properties, can be used as a carrier for lithium ion transmission, can bear the action of a solvent in an electrolyte to cooperatively promote the transmission of lithium ions in the plate, and improves the rate performance of the battery. Meanwhile, as the positive electrode slurry does not need to be additionally added with a binder and a conductive agent, the reduction of the material components in the slurry is also beneficial to improving the consistency of the slurry, and further the quality of the battery is improved. Furthermore, the composite polymer can also improve the mechanical property of the pole piece, endow the pole piece with flexibility, effectively relieve the volume expansion of the pole piece in the charging and discharging process, keep the stability of the electrode, further improve the transmission speed of lithium ions in the pole piece and improve the multiplying power performance.

In yet another aspect of the invention, the invention provides an automobile, which is provided with the lithium battery according to the embodiment of the invention. According to the automobile provided by the embodiment of the invention, the automobile is provided with the lithium battery, and the lithium battery is provided with the positive plate prepared from the positive slurry, so that the lithium battery has excellent cycle performance and rate capability, and good safety performance and consistency. Therefore, the cruising ability and the safety performance of the automobile are improved.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is an SEM photograph of a coating layer of a positive electrode sheet obtained in example 1;

fig. 2 is a charge and discharge performance test curve of the positive electrode sheet obtained in example 1;

FIG. 3 is a cycle performance test curve at 0.5C for the positive electrode sheets obtained in example 1 and comparative example 1;

fig. 4 is a graph showing rate performance test curves of the positive electrode sheets obtained in example 1 and comparative example 1 at 0.1C, 0.33C, 0.5C, 1C, and 2C;

fig. 5 is an SEM image of the coating layer of the positive electrode sheet obtained in comparative example 1.

Detailed Description

The following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.

In one aspect of the invention, the invention provides a composite polymer, which according to an embodiment of the invention is a block copolymer of polyfurfuryl alcohol and polyethylene oxide. The inventor finds that the composite polymer has the characteristics of electron and ion transmission, and compared with the traditional binder material, lithium ions can be freely transmitted in the composite polymer; compared to common ionic polymers, the conductivity is increased due to pi C ═ C chemical bonds forming an electron cloud. Meanwhile, the composite polymer contains a structural part similar to the adhesive, so that the composite polymer is easier to be fully mixed with the positive active substance to form a uniform phase, and the adhesive force and the stripping force of the pole piece are improved. Furthermore, the composite polymer can be quickly gelatinized after being added with electrolyte, so that the transmission of electrons and ions in the pole piece is promoted, and meanwhile, the existence of too much electrolyte in the battery cell can be avoided, and the safety performance of the battery is further improved.

According to one embodiment of the present invention, the composite polymer may be a chain polymer or a star polymer or a dendritic polymer, and those skilled in the art can select the polymer according to the needs and the preparation process. Further, the molecular weight of the composite polymer is not particularly limited, and those skilled in the art can select the molecular weight according to actual needs, such as 45000-. Depending on the reaction temperature, a polymer having a higher molecular weight can be produced at a high temperature to increase the viscosity of the polymer, whereby the temperature of the composite polymer can be increased by increasing the reaction temperature, for example, the reaction temperature can be increased to 55 ℃. Further, the solid content of the composite polymer is also not particularly limited, and may be, for example, 1.2 to 18% by weight. The inventors have found that increasing the solids content can increase the polymer slurry viscosity.

According to the composite polymer provided by the embodiment of the invention, the composite polymer has the characteristics of electron and ion transmission, and compared with the traditional binder material, lithium ions can be freely transmitted in the composite polymer; compared to common ionic polymers, the conductivity is increased due to pi C ═ C chemical bonds forming an electron cloud. Meanwhile, the composite polymer contains a structural part similar to the adhesive, so that the composite polymer is easier to be fully mixed with the positive active substance to form a uniform phase, and the adhesive force and the stripping force of the pole piece are improved. Furthermore, the composite polymer can be quickly gelatinized after being added with electrolyte, so that the transmission of electrons and ions in the pole piece is promoted, and meanwhile, the existence of too much electrolyte in the battery cell can be avoided, and the safety performance of the battery is further improved.

In yet another aspect of the present invention, the present invention provides a method of preparing a composite polymer, the method comprising, according to an embodiment of the present invention: the initiator, the solvent, the polyethylene oxide and the furfuryl alcohol are mixed and stirred so as to obtain the composite polymer. The inventor finds that under the action of an initiator and a solvent, furfuryl alcohol can be subjected to polymerization reaction, and polymerized furfuryl alcohol can be reacted with polyethylene oxide to obtain a block polymer of polyfurfuryl alcohol and polyethylene oxide. Specifically, the initiator and the solvent may be mixed and stirred first, and then the polyoxyethylene and the furfuryl alcohol may be added and stirred for mixing and reacting to obtain the composite polymer.

According to an embodiment of the present invention, the specific types of the initiator and the solvent are not particularly limited, and may be selected by those skilled in the art according to actual needs, for example, the initiator may be selected from at least one of oxalic acid and hydrochloric acid, preferably oxalic acid; the solvent may be at least one selected from the group consisting of N-methylpyrrolidone and dimethylsulfoxide. The inventors have found that the use of the above initiators and solvents is advantageous in reducing costs while allowing the reaction rate to be easily controlled. Further, the mass ratio of the initiator to the solvent is also not particularly limited, and may be, for example, 2 to 4: 90-98, preferably 1: 30. the inventors found that too high a mass ratio increases the viscosity of the slurry.

According to the preparation method of the embodiment of the invention, under the action of the initiator and the solvent, furfuryl alcohol can be subjected to polymerization reaction, and the polymerized furfuryl alcohol can be reacted with polyethylene oxide to obtain a block polymer of polyfurfuryl alcohol and polyethylene oxide. Under the combined action of the polyfurfuryl alcohol and the polyethylene oxide, the composite polymer has the characteristics of electron and ion transmission, and compared with the traditional binder material, lithium ions can be freely transmitted in the composite polymer; compared to common ionic polymers, the conductivity is increased due to pi C ═ C chemical bonds forming an electron cloud. Meanwhile, the composite polymer contains a structural part similar to the adhesive, so that the composite polymer is easier to be fully mixed with the positive active substance to form a uniform phase, and the adhesive force and the stripping force of the pole piece are improved. Furthermore, the composite polymer can be quickly gelatinized after being added with electrolyte, so that the transmission of electrons and ions in the pole piece is promoted, and meanwhile, the existence of too much electrolyte in the battery cell can be avoided, and the safety performance of the battery is further improved.

In another aspect of the present invention, the present invention provides a positive electrode slurry, which is composed of a positive electrode active material and a binder solution according to an embodiment of the present invention, wherein the binder solution is the composite polymer or the composite polymer prepared by the method for preparing the composite polymer. The inventor finds that the composite polymer has the binding property of the binding agent, can improve the compatibility of the binding agent and the positive active material, enables the positive active material to be uniformly dispersed in the pole piece, improves the binding force and the stripping force of the pole piece, improves the rate cycling performance of the battery, has the conductivity and the ion conductivity, can be used as a carrier for lithium ion transmission, and bears the action of a solvent in an electrolyte to cooperatively promote the transmission of lithium ions in the pole piece, so that the rate performance of the battery is improved. Therefore, the positive electrode slurry does not need to be additionally added with a binder and a conductive agent, and the reduction of the material components in the slurry is also beneficial to improving the consistency of the slurry, so that the quality of the battery is improved. Furthermore, the composite polymer can also improve the mechanical property of the pole piece, endow the pole piece with flexibility, effectively relieve the volume expansion of the pole piece in the charging and discharging process, keep the stability of the electrode, further improve the transmission speed of lithium ions in the pole piece and improve the multiplying power performance.

According to an embodiment of the present invention, the solid content and viscosity of the cathode slurry are not particularly limited, and those skilled in the art can select them according to actual needs, for example, the solid content can be 50-80 wt%, and the viscosity can be 3000-. The inventors have found that too high a slurry solids content and viscosity results in a reduced slurry consistency. Further, the specific type of the positive electrode active material is also not particularly limited, and may be NCM and/or NCA, for example.

According to the positive electrode slurry provided by the embodiment of the invention, the composite polymer has the bonding property of the binder, and can improve the compatibility of the binder and the positive active material, so that the positive active material is uniformly dispersed in the electrode plate, the bonding force and the stripping force of the electrode plate are improved, the rate cycle performance of the battery is improved, and the composite polymer also has the conductivity and ion conductivity, can be used as a carrier for lithium ion transmission, bears the action of a solvent in an electrolyte, and synergistically promotes the transmission of lithium ions in the electrode plate, and improves the rate performance of the battery. Therefore, the positive electrode slurry does not need to be additionally added with a binder and a conductive agent, and the reduction of the material components in the slurry is also beneficial to improving the consistency of the slurry, so that the quality of the battery is improved. Furthermore, the composite polymer can also improve the mechanical property of the pole piece, endow the pole piece with flexibility, effectively relieve the volume expansion of the pole piece in the charging and discharging process, keep the stability of the electrode, further improve the transmission speed of lithium ions in the pole piece and improve the multiplying power performance.

In yet another aspect of the present invention, the present invention provides a lithium battery having a positive electrode sheet prepared from the above positive electrode slurry according to an embodiment of the present invention. According to the lithium battery provided by the embodiment of the invention, the lithium battery is provided with the positive plate prepared by the positive slurry consisting of the positive active material and the composite polymer, and the composite polymer has the bonding property of the binder, so that the compatibility of the positive active material and the positive active material can be improved, the positive active material is uniformly dispersed in the plate, the bonding force and the stripping force of the plate are improved, the rate cycle performance of the battery is improved, and the lithium battery also has the conductive and ion-conducting properties, can be used as a carrier for lithium ion transmission, can bear the action of a solvent in an electrolyte to cooperatively promote the transmission of lithium ions in the plate, and improves the rate performance of the battery. Meanwhile, as the positive electrode slurry does not need to be additionally added with a binder and a conductive agent, the reduction of the material components in the slurry is also beneficial to improving the consistency of the slurry, and further the quality of the battery is improved. Furthermore, the composite polymer can also improve the mechanical property of the pole piece, endow the pole piece with flexibility, effectively relieve the volume expansion of the pole piece in the charging and discharging process, keep the stability of the electrode, further improve the transmission speed of lithium ions in the pole piece and improve the multiplying power performance.

In yet another aspect of the invention, the invention provides an automobile, which is provided with the lithium battery according to the embodiment of the invention. According to the automobile provided by the embodiment of the invention, the automobile is provided with the lithium battery, and the lithium battery is provided with the positive plate prepared from the positive slurry, so that the lithium battery has excellent cycle performance and rate capability, and good safety performance and consistency. Therefore, the cruising ability and the safety performance of the automobile are improved.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.