Method for improving the hardness of energy storage lithium ion batteries and lithium ion battery

Abstract

The application provides a method for improving the hardness of a lithium ion battery and the lithium ion battery. The method for improving the hardness of the lithium ion battery comprises the following steps: winding a cathode sheet, an anode sheet and a diaphragm to form a roll core, wherein one side of the diaphragm opposite to the cathode sheet is coated with a first ceramic layer and a polyvinylidene fluoride layer, and one side of the diaphragm opposite to the anode sheet is coated with a second ceramic layer and an acrylic layer; placing the roll core into an aluminum plastic film; baking the roll core; injecting liquid into the roll core and standing; pre-baking and hot-pressing the roll core; forming and distributing the roll core; cold and hot pressing the roll core; cooling the roll core; degassing and cutting the roll core, and obtaining the battery. The polyvinylidene fluoride layer and the cathode sheet expand when the battery is charged, so that the diaphragm and the cathode sheet are in close contact and are bonded, and the hardness of the roll core is improved. The first ceramic layer increases the heat resistance of the diaphragm and the affinity of the diaphragm to the electrolyte, and further improves the electrochemical performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a method for improving the hardness of a lithium ion battery for energy storage and a lithium ion battery. BACKGROUND

[0002] As the most representative energy storage device in the field of new energy, lithium ion batteries occupy an irreplaceable position in the power supply devices of mobile electronic products. With mobile electronic products becoming lighter and thinner, the thickness of lithium ion batteries therein is also becoming thinner. From the perspective of safety, the hardness requirement of lithium ion batteries is also becoming higher and higher, while the production efficiency of the battery cell also needs to be considered. Therefore, it is particularly important to prepare a lithium ion battery with high hardness in a very short time.

[0003] There are mainly two methods for improving the hardness of lithium ion batteries: one is to heat and cold-press the battery cell before formation, and then put it into a clamp for high-temperature and high-pressure baking after formation and capacity to improve the hardness of the battery cell. However, the use of high-temperature and high-pressure baking operation will result in the loss of battery capacity. The other is to coat polyvinylidene fluoride (PVDF) on the separator to increase the hardness of the battery cell. However, the coating of polyvinylidene fluoride on the separator will result in the deterioration of the electrochemical performance of the lithium ion battery. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method for improving the hardness of a lithium ion battery for energy storage and a lithium ion battery with improved battery capacity and electrochemical performance.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A method for improving the hardness of a lithium ion battery for energy storage, comprising:

[0007] winding a cathode sheet, an anode sheet and a separator to form a roll core, wherein one side of the separator opposite to the cathode sheet is mixedly coated with a first ceramic layer and a polyvinylidene fluoride layer, and one side of the separator opposite to the anode sheet is mixedly coated with a second ceramic layer and an acrylic layer;

[0008] putting the battery cell into an aluminum plastic film;

[0009] baking the battery cell;

[0010] injecting liquid into the battery cell and standing;

[0011] performing pre-baking and hot-pressing operations on the battery cell;

[0012] performing formation and capacity distribution operations on the battery cell;

[0013] performing cold and hot pressing shaping operations on the battery cell;

[0014] cooling the battery cell;

[0015] degassing and cutting the gas pocket of the battery cell to obtain a battery.

[0016] In one embodiment, the front and back surfaces of the battery cell are pressed during the pre-baking and hot-pressing of the battery cell.

[0017] In one embodiment, a pressure of 0.1-2.0 MPa is applied to the front and back surfaces of the battery cell during the pre-baking and hot-pressing of the battery cell.

[0018] In one embodiment, the pre-baking temperature is 60-90°C and the pre-baking time is 10-30 min during the pre-baking and hot-pressing of the battery cell.

[0019] In one embodiment, the battery cell is placed vertically in the formation machine during the pre-baking and hot-pressing of the battery cell.

[0020] In one embodiment, the formation and equalization of the battery cell comprises:

[0021] clamping the battery cell in the charge-discharge tester;

[0022] repeatedly performing cyclic charging on the battery cell using three charging currents in sequence, with the charging currents increasing in sequence, until the battery cell reaches a predetermined voltage;

[0023] alternately performing charging / discharging and discharging / charging on the battery cell.

[0024] In one embodiment, the formation temperature is 80±5°C during the repeatedly performing cyclic charging on the battery cell using three charging currents in sequence, with the charging currents increasing in sequence, until the battery cell reaches a predetermined voltage.

[0025] In one embodiment, the cyclic charging is performed using charging currents of 0.05C, 0.1C and 0.15C in sequence, for 3-5 cycles, until the potential of the battery cell is 3.6-3.8V during the repeatedly performing cyclic charging on the battery cell using three charging currents in sequence, with the charging currents increasing in sequence, until the battery cell reaches a predetermined voltage.

[0026] In one embodiment, the cold and hot shaping of the battery cell comprises:

[0027] hot-pressing the battery cell using a steel glass clamping plate set, with a hot-pressing time of 10-30 min, a clamping force of 100-300 kg and a hot-pressing temperature of 80±5°C;

[0028] The electric core is hot-pressed by the tempered glass clamping plate group, the hot-pressing time is 10-30 min, the clamping force is 100-300 kg, and the hot-pressing temperature is 45-60 DEG C.

[0029] The electric core is cold-pressed by the tempered glass clamping plate group, the cold-pressing time is 10-30 min, the clamping force is 100-300 kg, and the cold-pressing temperature is 20-28 DEG C.

[0030] A lithium ion battery prepared by the method for improving the hardness of the energy storage lithium ion battery according to any one of the above embodiments.

[0031] Compared with the prior art, the present application has at least the following advantages:

[0032] 1. The cathode sheet is mixed coated by the first ceramic layer and the polyvinylidene fluoride layer, which can improve the hardness of the battery and inhibit the influence of the polyvinylidene fluoride layer on the electrochemical performance. Specifically, the polyvinylidene fluoride layer and the cathode sheet expand during the charging of the battery, so that the separator and the cathode sheet are in close contact and adhesion, thereby improving the hardness of the electric core. The first ceramic layer increases the heat resistance of the separator and the affinity to the electrolyte, thereby improving the electrochemical performance of the battery. In this way, the hardness of the battery is improved, and the influence of the polyvinylidene fluoride layer on the electrochemical performance is inhibited.

[0033] 2. The anode sheet is mixed coated by the second ceramic layer and the acrylic layer, the anode sheet, i.e. the negative electrode sheet, is in contact with the acrylic layer. The acrylic layer is polymethyl methacrylate, which belongs to organic glass, and the adhesion between the acrylic layer and the anode sheet is not good. Therefore, the problem of powder falling and falling of the anode sheet under pressure is better prevented, and the acrylic layer can also provide support for the electrode plate to avoid the electrode plate from being wrinkled under pressure, thereby preventing the surface of the anode sheet from falling and falling due to uneven pressure under pressure, and improving the electrochemical performance of the battery.

[0034] 3. The traditional technology needs to perform a hot-pressing operation at high temperature and high pressure to improve the hardness of the electric core. However, the electric core of the present application has the first ceramic layer and the polyvinylidene fluoride layer mixed on the opposite side of the separator and the ceramic layer and the acrylic layer mixed on the opposite side of the anode sheet, so that the hardness of the electric core is high, and the hot-pressing operation at high temperature and high pressure is not needed, thereby inhibiting the capacity loss of the battery. Therefore, compared with the capacity of the traditional battery, the capacity of the battery of the present application is higher.

[0035] 4. Lithium ions need to pass through the second ceramic layer and the acrylic layer in the process of embedding into the negative electrode material of the anode sheet, so that the second ceramic layer and the acrylic layer alleviate the impact of lithium ions on the negative electrode material, avoid the collapse of the negative electrode material, and inhibit the problem of powder falling of the negative electrode material, thereby improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0037] Figure 1 The flow chart of the steps of the method for improving the hardness of the energy storage lithium ion battery. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present application, the following will be described in more detail with reference to the related drawings. The drawings show the preferred embodiments of the present application. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0039] It should be noted that when a component is referred to as being "fixed" to another component, it can be directly on the other component or there can be an intervening component. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or there can be an intervening component. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are for illustrative purposes only and are not intended to be limiting.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] A method for improving the hardness of an energy storage lithium ion battery, comprising: winding a cathode sheet, an anode sheet and a separator to form a roll core, wherein one side of the separator opposite to the cathode sheet is mixed coated with a first ceramic layer and a polyvinylidene fluoride layer, and one side of the separator opposite to the anode sheet is mixed coated with a second ceramic layer and an acrylic layer; packaging the roll core in an aluminum plastic film; baking the roll core; injecting liquid into the roll core and standing; pre-baking and hot pressing the roll core; forming and distributing the roll core; cold and hot pressing the roll core; cooling the roll core; degassing and cutting the roll core, to obtain a battery.

[0042] The method for improving the hardness of the energy storage lithium ion battery improves the hardness of the battery while inhibiting the influence of the polyvinylidene fluoride layer on the electrochemical performance by mixing the first ceramic layer and the polyvinylidene fluoride layer on the cathode sheet. Specifically, the polyvinylidene fluoride layer and the cathode sheet expand during charging of the battery, so that the separator is in close contact and bonded with the cathode sheet, thereby improving the hardness of the battery cell. The first ceramic layer increases the heat resistance of the separator and the affinity to the electrolyte, thereby improving the electrochemical performance of the battery. In this way, the hardness of the battery is improved while the influence of the polyvinylidene fluoride layer on the electrochemical performance is inhibited.

[0043] Further, the anode sheet, i.e., the negative electrode sheet, is in contact with the acrylic layer, which is polymethyl methacrylate and belongs to organic glass. The acrylic layer and the anode sheet have poor adhesion. The second ceramic layer and the acrylic layer mixed on the anode sheet can better prevent the anode sheet from falling off and shedding under pressure. The acrylic layer can also provide support for the electrode plate to avoid wrinkles on the electrode plate under pressure, prevent the surface of the anode sheet from falling off and shedding due to uneven pressure, and improve the electrochemical performance of the battery.

[0044] Further, the traditional technology needs to perform a hot pressing operation at high temperature and high pressure to improve the hardness of the battery cell. The battery cell of the present application has a first ceramic layer and a polyvinylidene fluoride layer mixed on the side of the separator opposite the cathode sheet, and a second ceramic layer and an acrylic layer mixed on the side of the separator opposite the anode sheet, so that the hardness of the battery cell is high, and the hot pressing operation at high temperature and high pressure is not needed, thereby inhibiting the capacity loss of the battery. Therefore, compared with the capacity of the traditional battery, the capacity of the battery of the present application is higher. Moreover, lithium ions need to pass through the second ceramic layer and the acrylic layer during embedding in the negative electrode material of the anode sheet, so that the second ceramic layer and the acrylic layer alleviate the impact of lithium ions on the negative electrode material, avoid the collapse of the negative electrode material, and inhibit the problem of powder falling of the negative electrode material, thereby improving the electrochemical performance of the battery.

[0045] In order to better understand the technical solutions and beneficial effects of the present application, the present application will be further described in detail in combination with specific embodiments:

[0046] As shown in the method for improving the hardness of the energy storage lithium ion battery according to an embodiment, the method comprises: Figure 1

[0047] S101: winding the cathode sheet, the anode sheet and the separator to form a roll core, wherein the side of the separator opposite the cathode sheet is mixed with a first ceramic layer and a polyvinylidene fluoride layer, and the side of the separator opposite the anode sheet is mixed with a second ceramic layer and an acrylic layer.

[0048] In this embodiment, after the cathode sheet, the anode sheet and the separator are stacked, the cathode sheet, the anode sheet and the separator are wound by a winding machine to form a roll core. ​

[0049] Further, by mixing the first ceramic layer and the polyvinyl fluoride layer to coat the cathode sheet, specifically, the first ceramic layer is coated on one side of the cathode sheet, the polyvinyl fluoride layer is coated on the first ceramic layer, and the polyvinyl fluoride layer is arranged opposite to the separator, which improves the hardness of the battery while inhibiting the influence of the polyvinyl fluoride layer on the electrochemical performance. Specifically, the polyvinyl fluoride layer and the cathode sheet expand during charging of the battery, so that the separator is in close contact and bonded with the cathode sheet, thereby improving the hardness of the battery. The first ceramic layer increases the heat resistance of the separator and the affinity to the electrolyte, thereby improving the electrochemical performance of the battery. In this way, the hardness of the battery is improved while the influence of the polyvinyl fluoride layer on the electrochemical performance is inhibited.

[0050] Further, by mixing the second ceramic layer and the acrylic layer to coat the anode sheet, specifically, the second ceramic layer is coated on the anode sheet, the acrylic layer is coated on the second ceramic layer, and the acrylic layer is arranged opposite to the separator, and the anode sheet, i.e. the negative electrode sheet, is in contact with the acrylic layer. Since the acrylic layer is polymethyl methacrylate, which belongs to organic glass, and the acrylic layer has poor adhesion with the anode sheet, the problem of powder falling off of the anode sheet under pressure is better prevented. At the same time, the acrylic layer can also provide support for the electrode plate to avoid the electrode plate from being wrinkled under pressure, prevent the surface of the anode sheet from falling off due to uneven pressure under pressure, and improve the electrochemical performance of the battery. Moreover, lithium ions need to pass through the second ceramic layer and the acrylic layer during embedding into the negative electrode material of the anode sheet, so that the second ceramic layer and the acrylic layer alleviate the impact of lithium ions on the negative electrode material, avoid the collapse of the negative electrode material, and inhibit the problem of powder falling off of the negative electrode material, thereby improving the electrochemical performance of the battery.

[0051] S103: The battery cell is loaded into an aluminum plastic film.

[0052] In this embodiment, the battery cell is loaded into an aluminum plastic film to coat the battery cell with the aluminum plastic film.

[0053] S105: The battery cell is baked.

[0054] In this embodiment, the battery cell is baked to remove moisture in the battery cell, thereby avoiding dilution of the electrolyte by the moisture.

[0055] S107: The battery cell is injected with electrolyte and left to stand.

[0056] In this embodiment, the electrolyte is injected into the battery cell, and then left to stand for a period of time to allow the electrolyte to fully soak the battery cell.

[0057] S109: The battery cell is pre-baked and hot-pressed.

[0058] In the embodiment, the flowability of the electrolyte is increased by baking the battery cell, and the effect of formation is improved, and the excess electrolyte is squeezed into the air bag by hot pressing the battery cell. The pressure is applied to both sides of the battery cell at the same time, so that the interface between the anode and the cathode is better fitted, the electrochemical impedance of the battery cell is reduced, and the first charge and discharge efficiency is improved.

[0059] S111: performing formation and equalization operations on the battery cell.

[0060] In the embodiment, the formation and equalization operations of the battery cell are performed in the charge and discharge test machine, and the battery cell is activated by charging multiple times. The equalization is performed immediately after the formation is completed, so that the formation and equalization are quickly completed in the same stage, the process integration is realized, and the production efficiency is improved.

[0061] S113: performing cold and hot pressing shaping operations on the battery cell.

[0062] In the embodiment, when the battery cell completes the formation and equalization operations, the battery cell has a temperature after formation, and the cold and hot pressing operations are performed on the battery cell until the battery cell cools to a predetermined temperature, such as the temperature of the working environment. By cold and hot pressing the battery cell, the internal stress of the battery can be effectively released, so that the flatness, thickness consistency and capacity of the battery cell are higher. Further, in order to improve the hardness of the battery cell, the traditional technology needs to perform a hot pressing operation at high temperature and high pressure, but the battery cell of the present application has a first ceramic and polyvinylidene fluoride layer mixed coated on the side of the separator opposite to the cathode sheet, and a ceramic layer and acrylic layer mixed coated on the side of the separator opposite to the anode sheet, so that the hardness of the battery cell is higher, and the hot pressing operation at high temperature and high pressure is not needed, the capacity loss of the battery is inhibited, and thus, the capacity of the battery of the present application is higher than that of the traditional battery.

[0063] S115: performing cooling operations on the battery cell.

[0064] In the embodiment, after the battery cell is cooled, the shape of the battery cell is kept in a stable state.

[0065] S117: performing degassing and cutting air bag operations on the battery cell to obtain a battery.

[0066] In the embodiment, the gas in the battery cell is extracted and the air bag is cut to obtain a battery.

[0067] The method for improving the hardness of the energy storage lithium ion battery, by mixing the first ceramic layer and the polyvinyl fluoride layer on the cathode sheet, improves the hardness of the battery while inhibiting the influence of the polyvinyl fluoride layer on the electrochemical performance. Specifically, the polyvinyl fluoride layer and the cathode sheet expand during the charging of the battery, so that the separator and the cathode sheet are in close contact and are bonded, thereby improving the hardness of the battery cell. The first ceramic layer increases the heat resistance of the separator and the affinity to the electrolyte, thereby improving the electrochemical performance of the battery. In this way, the hardness of the battery is improved while the influence of the polyvinyl fluoride layer on the electrochemical performance is inhibited.

[0068] Further, by mixing the second ceramic layer and the acrylic layer on the anode sheet, the anode sheet, i.e. the negative electrode sheet, is in contact with the acrylic layer. The acrylic layer is polymethyl methacrylate, which is organic glass, and the adhesion between the acrylic layer and the anode sheet is not good. The acrylic layer can better prevent the anode sheet from falling off and shedding under pressure, and can also provide support for the electrode plate to avoid wrinkles in the electrode plate under pressure, thereby preventing the surface of the anode sheet from falling off and shedding due to uneven pressure, and improving the electrochemical performance of the battery.

[0069] Further, the traditional technology requires a high-temperature and high-pressure heat pressing operation to improve the hardness of the battery cell. The battery cell of the present application has the first ceramic layer and the polyvinyl fluoride layer mixed on the side of the separator opposite the cathode sheet, and the ceramic layer and the acrylic layer mixed on the side of the separator opposite the anode sheet, so that the hardness of the battery cell is high and the heat pressing operation under high temperature and high pressure is not required, thereby inhibiting the capacity loss of the battery. Therefore, the capacity of the battery of the present application is higher than that of the conventional battery. Moreover, the lithium ion needs to pass through the second ceramic layer and the acrylic layer during embedding in the negative electrode material of the anode sheet, so that the second ceramic layer and the acrylic layer alleviate the impact of the lithium ion on the negative electrode material, avoid the collapse of the negative electrode material, and inhibit the problem of powder falling of the negative electrode material, thereby improving the electrochemical performance of the battery.

[0070] In one embodiment, during the pre-baking and heat pressing operation of the battery cell, the front and back surfaces of the battery cell are pressed, so that the interface between the anode and the cathode is better fitted, the electrochemical impedance of the battery cell is reduced, and the first charge and discharge efficiency is improved.

[0071] In one embodiment, during the pre-baking and heat pressing operation of the battery cell, a pressure of 0.1-2.0 MPa is applied to the front and back surfaces of the battery cell to make the interface between the anode and the cathode better fitted.

[0072] In one embodiment, during the pre-baking and heat pressing operation of the battery cell, the pre-baking temperature is 60-90°C, and the pre-baking time is 10-30 min, so that the flowability of the electrolyte is better.

[0073] In one of the embodiments, in the step of pre-baking and hot-pressing the battery cell, the battery cell is vertically placed in the formation machine.

[0074] In one of the embodiments, the step of forming and equalizing the battery cell includes: clamping the battery cell in the charge-discharge tester; performing multiple cyclic charging operations on the battery cell using three charging currents in sequence, which are sequentially increased, to make the battery cell reach a predetermined voltage; and performing charging / discharging and discharging / charging operations on the battery cell in sequence. In this embodiment, the battery cell is clamped in the charge-discharge tester, and then is cyclically charged to the SEI film formation voltage using three small currents in sequence, which are sequentially increased, so that the battery polarization is smaller, and the capacity consistency of the prepared battery cell is better. Moreover, the formation and the capacity are quickly completed in the same stage, the process integration is realized, and the production efficiency is improved.

[0075] In one of the embodiments, in the step of performing multiple cyclic charging operations on the battery cell using three charging currents in sequence, which are sequentially increased, to make the battery cell reach a predetermined voltage, the formation temperature is 80±5℃, so as to improve the formation effect.

[0076] In the conventional technology, a high-rate charging current is used for cyclic charging during formation, which can cause the battery polarization and the electrolyte absorption not timely, resulting in the first ceramic layer and the second ceramic layer falling off, the battery internal resistance increasing, and the battery performance decreasing. In order to solve the problems of the first ceramic layer and the second ceramic layer falling off and the battery internal resistance increasing during formation, in one of the embodiments, in the step of performing multiple cyclic charging operations on the battery cell using three charging currents in sequence, which are sequentially increased, to make the battery cell reach a predetermined voltage, the cyclic charging operations are performed using charging currents of 0.05C, 0.1C and 0.15C in sequence, and the cycle number is 3-5, so that the potential of the battery cell is 3.6-3.8V. Since a small-rate current is used for cyclic charging during formation, the problem of the first ceramic layer and the second ceramic layer falling off is inhibited, and the battery polarization is smaller, the battery internal resistance is smaller, and the capacity consistency of the prepared battery cell is better.

[0077] In one embodiment, the cold and hot pressing step of the cell includes: hot pressing the cell by a set of tempered glass clamping plates, the hot pressing time is 10-30 min, the clamping force is 100-300 kg, and the hot pressing temperature is 80±5℃; hot pressing the cell by a set of tempered glass clamping plates, the hot pressing time is 10-30 min, the clamping force is 100-300 kg, and the hot pressing temperature is 45-60℃; and cold pressing the cell by a set of tempered glass clamping plates, the cold pressing time is 10-30 min, the clamping force is 100-300 kg, and the cold pressing temperature is 20-28℃. In this embodiment, the cold and hot pressing is performed immediately after the formation and capacity test to cool the cell, which can effectively release the internal stress of the battery, so that the flatness, thickness consistency and capacity of the cell are higher. Further, the traditional technology needs to perform a hot pressing operation at high temperature and high pressure to improve the hardness of the cell, while the cell of the present application has a higher hardness due to the mixed coating of the first ceramic and polyvinylidene fluoride layer on the side of the separator opposite to the cathode sheet, and the mixed coating of the ceramic layer and acrylic layer on the side of the separator opposite to the anode sheet, so that the cell does not need to be hot pressed at high temperature and high pressure, which inhibits the capacity loss of the battery. Therefore, the capacity of the battery of the present application is higher than that of the traditional battery.

[0078] It can be understood that using a larger charging current for charging operation will result in a looser SEI film, which in turn results in a higher reuse rate of the battery, so the traditional technology uses a smaller current, but this will result in a slower formation efficiency of the battery. Therefore, in one embodiment, in the step of using three charging currents in sequence to perform multiple cyclic charging operations to make the cell reach a predetermined voltage, first, 0.05C, 0.1C and 0.15C charging currents are used in sequence to perform 3-5 cyclic charging operations, and then 1C and 0.2C are used in sequence to charge the cell to make the cell reach a predetermined voltage. In this embodiment, a plurality of small currents in sequence are first used to perform 3-5 cyclic charging operations on the cell, and then large currents in sequence are used for charging, i.e., small currents are used for cyclic charging first, and then large currents are used for charging, which improves the formation efficiency and in turn improves the production efficiency of the battery.

[0079] The present application also provides a lithium ion battery by the method for improving the hardness of the energy storage lithium ion battery according to any one of the above embodiments.

[0080] In one embodiment, the method for improving the hardness of the energy storage lithium ion battery includes: winding the cathode sheet, the anode sheet and the separator to form a roll core, wherein the side of the separator opposite to the cathode sheet is coated with a first ceramic layer and a polyvinylidene fluoride layer, and the side of the separator opposite to the anode sheet is coated with a second ceramic layer and an acrylic layer; the cell is packaged in an aluminum plastic film; the cell is baked; the cell is injected and left; the cell is pre-baked and hot-pressed; the cell is formed and divided; the cell is cold and hot pressed; the cell is cooled; the cell is degassed and the gas bag is cut off, and the battery is obtained.

[0081] The above method for improving the hardness of the energy storage lithium ion battery, by mixing the first ceramic layer and the polyvinylidene fluoride layer on the cathode sheet, improves the hardness of the battery while inhibiting the influence of the polyvinylidene fluoride layer on the electrochemical performance. Specifically, the polyvinylidene fluoride layer and the cathode sheet expand during battery charging, causing the separator to be in close contact and bonded with the cathode sheet, thereby improving the hardness of the cell. The first ceramic layer increases the heat resistance of the separator and the affinity to the electrolyte, thereby improving the electrochemical performance of the battery. In this way, the hardness of the battery is improved while the influence of the polyvinylidene fluoride layer on the electrochemical performance is inhibited.

[0082] Further, by mixing the second ceramic layer and the acrylic layer on the anode sheet, the anode sheet, i.e. the negative electrode sheet, is in contact with the acrylic layer. Since the acrylic layer is polymethyl methacrylate, which is organic glass, and the adhesion between the acrylic layer and the anode sheet is not good, the problem of powder falling off the anode sheet under pressure is better prevented. At the same time, the acrylic layer can also provide support to the electrode plate to avoid wrinkles on the electrode plate under pressure, prevent the surface of the anode sheet from falling off due to uneven pressure under pressure, and improve the electrochemical performance of the battery.

[0083] Further, the traditional technology requires a hot pressing operation at high temperature and high pressure to improve the hardness of the cell. However, the cell of the present application has a high hardness due to the mixing of the first ceramic and polyvinylidene fluoride layer on the side of the separator opposite to the cathode sheet and the mixing of the ceramic layer and the acrylic layer on the side of the separator opposite to the anode sheet, so that the hot pressing operation at high temperature and high pressure is not required, the capacity loss of the battery is inhibited, and thus the battery capacity of the present application is higher than that of the conventional battery. Moreover, lithium ions need to pass through the second ceramic layer and the acrylic layer during embedding into the negative electrode material of the anode sheet, so that the second ceramic layer and the acrylic layer alleviate the impact of lithium ions on the negative electrode material, avoid the collapse of the negative electrode material, and inhibit the problem of powder falling off the negative electrode material, thereby improving the electrochemical performance of the battery.

[0084] Compared with the prior art, the present application has at least the following advantages:

[0085] 1. By co-coating the cathode sheet with a first ceramic layer and a polyvinylidene fluoride (PVDF) layer, the battery hardness is improved while the influence of the PVDF layer on electrochemical performance is suppressed. Specifically, the PVDF layer and the cathode sheet expand during battery charging, causing the separator and cathode sheet to make close contact and adhere, thus improving the cell hardness. The first ceramic layer increases the separator's heat resistance and affinity for the electrolyte, thereby improving the battery's electrochemical performance. In this way, the battery hardness is improved while suppressing the influence of the PVDF layer on electrochemical performance.

[0086] 2. The anode sheet is coated with a mixture of a second ceramic layer and an acrylic layer. The anode sheet, i.e., the negative electrode sheet, is in contact with the acrylic layer. Since the acrylic layer is polymethyl methacrylate, which is a type of plexiglass, and the adhesion between the acrylic layer and the anode sheet is not good, it better prevents the anode sheet from shedding powder and falling off under pressure. At the same time, the acrylic layer can also provide support for the electrode plate, preventing the electrode plate from wrinkling under pressure. This also prevents the anode sheet surface from shedding powder and falling off due to uneven pressure, thus improving the electrochemical performance of the battery.

[0087] 3. Traditional technology requires a hot-pressing operation at high temperature and high pressure to improve the hardness of the battery cell. However, the battery cell of this application has a high hardness because the side of the separator opposite the cathode is coated with a first ceramic and polyvinylidene fluoride layer, and the side of the separator opposite the anode is coated with a ceramic layer and an acrylic layer. This eliminates the need for a hot-pressing operation at high temperature and high pressure, thus suppressing the capacity loss of the battery. As a result, the battery capacity of this invention is higher than that of traditional batteries.

[0088] 4. During the process of embedding lithium ions into the negative electrode material of the anode sheet, they need to pass through the second ceramic layer and the acrylic layer. The second ceramic layer and the acrylic layer alleviate the impact of lithium ions on the negative electrode material, prevent the negative electrode material from collapsing, and suppress the problem of powder shedding from the negative electrode material, thereby improving the electrochemical performance of the battery.

[0089] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method of increasing the hardness of an energy storage lithium-ion battery, characterized by, The method comprises the following steps: rolling the cathode sheet, the anode sheet and the separator to form a roll core, wherein the side of the separator opposite to the cathode sheet is coated with a first ceramic layer and a polyvinylidene fluoride layer, and the side of the separator opposite to the anode sheet is coated with a second ceramic layer and an acrylic layer; putting the electric core into an aluminum plastic film; baking the electric core; injecting liquid into the electric core and standing; pre-baking and hot pressing the electric core; forming and distributing the electric core; cold and hot pressing the electric core; cooling the electric core; de-gassing and cutting the gas bag of the electric core to obtain a battery. The step of forming and distributing the electric core comprises the following steps: clamping the electric core in a charge-discharge tester; carrying out multiple cycle charging operations on the electric core using three charging currents in sequence to make the electric core reach a predetermined voltage; carrying out charging / discharging and discharging / charging operations on the electric core in sequence; in the step of carrying out multiple cycle charging operations using three charging currents in sequence to make the electric core reach a predetermined voltage, the cycle charging operations are carried out using charging currents of 0.05C, 0.1C and 0.15C in sequence, and the cycle number is 3-5 times, so that the electric potential of the electric core is 3.6-3.8V; or in the step of carrying out multiple cycle charging operations using three charging currents in sequence to make the electric core reach a predetermined voltage, first, cycle charging operations are carried out using charging currents of 0.05C, 0.1C and 0.15C in sequence for 3-5 times, and then the electric core is charged using 1C and 0.2C in sequence to make the electric core reach a predetermined voltage.

2. The method of increasing the hardness of an energy storage lithium-ion battery of claim 1, wherein, In the step of pre-baking and hot pressing the electric core, the front and back sides of the electric core are pressed.

3. The method of increasing the hardness of an energy storage lithium-ion battery of claim 2, wherein, In the step of pre-baking and hot pressing the electric core, a pressure of 0.1-2.0MPa is applied to the front and back sides of the electric core at the same time.

4. The method of increasing the hardness of an energy storage lithium-ion battery of claim 1, wherein, In the step of pre-baking and hot pressing the electric core, the pre-baking temperature is 60-90℃, and the pre-baking time is 10-30min.

5. The method of increasing the hardness of an energy storage lithium-ion battery of claim 1, wherein, In the step of pre-baking and hot pressing the electric core, the electric core is vertically placed in a forming machine.

6. The method of increasing the hardness of an energy storage lithium-ion battery of claim 1, wherein, In the step of carrying out multiple cycle charging operations using three charging currents in sequence to make the electric core reach a predetermined voltage, the forming temperature is 80±5℃.

7. The method of increasing the hardness of an energy storage lithium-ion battery of claim 1, wherein, The step of cold and hot pressing the electric core comprises the following steps: hot pressing the electric core through a steel glass clamping plate group, the hot pressing time is 10-30min, the clamping force is 100-300kg, and the hot pressing temperature is 80±5℃; hot pressing the electric core through a steel glass clamping plate group, the hot pressing time is 10-30min, the clamping force is 100-300kg, and the hot pressing temperature is 45-60℃; cold pressing the electric core through a steel glass clamping plate group, the cold pressing time is 10-30min, the clamping force is 100-300kg, and the cold pressing temperature is 20-28℃.

8. A lithium-ion battery, characterized by, The method is prepared by the method for improving the hardness of the energy storage lithium ion battery in any one of claims 1-7.

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