Gas film-forming additive release device and battery

Abstract

The utility model provides a gas film-forming additive release device and a battery, the gas film-forming additive release device comprises a shell capable of isolating liquid, the shell is enclosed to form a hollow cavity for accommodating a gas film-forming additive, the shell comprises a first part and a second part which are spliced with each other, the first part is a breathable part, and the second part is a hollow part. The ventilation piece comprises a plurality of ventilation holes. The device provided by the utility model is used for the battery, and can release the gas film-forming additive in the electrolyte to continuously provide conditions for film formation on the surface of the negative electrode, so that serious rupture of an SEI film in the cycle process of the battery is avoided, and long cycle and low attenuation of the battery are realized.

Description

Technical Field

[0001] The present application relates to the field of battery devices, and in particular to a gas film-forming additive release device and a battery. Background Art

[0002] During the formation stage of the battery, the electrolyte will form a thin solid electrolyte film (SEI) on the surface of the negative electrode. A stable SEI film is the key to improving the electrochemical performance of lithium-ion batteries. However, as the battery is continuously charged and discharged, the SEI film will be continuously destroyed and regenerated, and the active lithium in the battery will be continuously consumed, resulting in a decrease in the battery's cycle performance. Using electrolyte film-forming additives is one of the most economical and effective methods to improve the performance of lithium-ion batteries. Among them, gas film-forming additives (carbon dioxide, sulfur dioxide, etc.) are commonly used additives for forming SEI films on the surface of the negative electrode. However, the solubility of common gas film-forming additives in the electrolyte is limited, and a small amount of gas film-forming additives will basically be consumed during the formation. Therefore, it is difficult for the SEI film to be continuously repaired during a long cycle. In addition, if an excessive amount of gas film-forming additives is added to the initial electrolyte, it is very likely to cause excessive internal pressure in the battery, which is easy to cause safety hazards. Utility Model Content

[0003] The present application provides a gas film-forming additive release device to solve the problems existing in the prior art.

[0004] The present application also provides a battery. Since the battery includes the above-mentioned gas film-forming additive release device, the battery has a long cycle life.

[0005] On the one hand, the present application provides a gas film-forming additive release device, including a shell that can isolate liquid, the shell encloses a hollow chamber for accommodating the gas film-forming additive, the shell includes a first part and a second part spliced ​​to each other, the first part is a breathable part, and the breathable part includes a plurality of breathable holes.

[0006] In a preferred embodiment, the second part has N splicing interfaces, the first part includes N breathable components, and the N breathable components are spliced ​​to the N splicing interfaces in a one-to-one correspondence, wherein N≥1.

[0007] In a preferred embodiment, the hollow chamber includes M independent hollow sub-chambers, and each of the hollow sub-chambers is connected to the outside through at least one of the air permeable members, wherein 1<M≤N.

[0008] In a preferred embodiment, the pore size of the air-permeable pore is P, wherein 0.3 nm ≤ P < 0.4 nm.

[0009] In a preferred embodiment, the gas film-forming additive release device satisfies the following formula 1:

[0010] V0>V1+V2 Formula 1;

[0011] Among them, V0 is the volume of the hollow chamber, V1 is the total pore volume of the electrode and the diaphragm in the battery, and V2 is the total volume of the gas film-forming additive that can be dissolved in the electrolyte.

[0012] In a preferred embodiment, the material of the breathable member is one of polytetrafluoroethylene resin, polyethylene, polypropylene, chloroprene rubber, polyamide fiber, aromatic polyamide fiber, polyester and polyvinyl alcohol fiber.

[0013] In a preferred embodiment, a connecting piece is provided on a side of the second portion away from the hollow chamber, and the connecting piece is used to be connected to the inner side of a cell casing of the battery.

[0014] In a preferred embodiment, the connecting member comprises an adhesive layer, and the adhesive layer is used for bonding and connecting with the inner side of the battery cell casing.

[0015] On the other hand, the present application provides a battery, which includes the above-mentioned gas film-forming additive release device, and the permeable member is at least partially immersed in the electrolyte of the battery.

[0016] In a preferred embodiment, the gas film-forming additive release device is connected to the inner side of the battery cell casing.

[0017] The device provided in the present application is used for batteries, and can release gas film-forming additives in the electrolyte to continuously provide conditions for film formation on the surface of the negative electrode, thereby avoiding serious rupture of the SEI film during the battery cycle and achieving long-cycle low attenuation of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0019] Figure 1 A gas film-forming additive release device according to a specific embodiment of the present application;

[0020] In the figure, 001: housing, 002: first part, 003: hollow chamber, 004: second part, 005: connector, 0010: gas inlet;

[0021] Figure 2 A gas film-forming additive release device according to another specific embodiment of the present application;

[0022] In the figure, 001: housing, 0021: air permeable member, 0022: air permeable member, 0031: hollow chamber, 0032: hollow chamber, 004: second part, 005: connecting member;

[0023] Figure 3 A battery according to a specific embodiment of the present application;

[0024] In the figure, 007: battery cell shell, 006: gas film-forming additive release device, 008: negative electrode sheet, 009 positive electrode sheet;

[0025] Figure 4 The capacity retention curves of the batteries of Example 2 and Comparative Example 1 of the present application after 100 cycles.

[0026] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the application embodiments will be clearly and completely described below in combination with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in the application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if there are terms such as "upper", "lower", "left", "right" and the like indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific direction. It is constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0029] Gas film-forming additives are commonly used additives to form SEI film on the surface of the negative electrode, but the solubility of common gas film-forming additives (carbon dioxide, sulfur dioxide, etc.) in the electrolyte is very limited. The existing means are usually to dissolve as much gas film-forming additive as possible in the electrolyte by pressurizing the battery before formation. However, this method is very likely to cause excessive pressure inside the battery, which may easily cause safety hazards. Moreover, after the battery is formed, there may still be little gas film-forming additives left. After several cycles of the battery, the SEI film will rupture again, affecting the battery life.

[0030] Based on the above problems, on the one hand, the present application provides a gas film-forming additive releasing device, which can accommodate the gas film-forming additive and isolate it from the electrolyte. Since the volume of the accommodating chamber can be set as needed, the gas film-forming additive can be continuously released and dissolved in the electrolyte during the long-term circulation process of battery formation or after formation, thereby repairing the SEI film in time and helping to extend the battery life.

[0031] Figure 1 A gas film-forming additive release device according to a specific embodiment of the present application, combined with Figure 1 The device is described in detail, including: a shell 001 that can isolate liquid, the shell encloses a hollow chamber 003 for accommodating gas film-forming additives, the shell 001 includes a first part 002 and a second part 004 spliced ​​to each other, the first part is a breathable part, and the breathable part includes a plurality of breathable holes.

[0032] It can be understood that in order to avoid adverse effects on battery charging and discharging, the shell is preferably made of corrosion-resistant insulating materials. In addition, in order for the device to be used normally when the battery is negatively pressurized, the device should meet the following conditions: under a pressure of -200Kpa to -80Kpa, the shell is not damaged, and the air-permeable member can continuously release gas film-forming additives. Exemplarily, the material of the second part 004 can be plastic, rubber, etc., and the material of the air-permeable member can be flexible polymer, fiber, etc.

[0033] The present application does not specifically limit the shapes of the shell 001, the hollow chamber 003, the first part 002 and the second part 004. For example, the shell 001 and the hollow chamber 003 can independently be cylinders, cubes, cones, prisms, irregular cubes, etc., and the first part 002 and the second part 004 can be regarded as two mutually connected parts divided by the shell 001 along any regular or regular dividing line.

[0034] Similarly, the shape of the above-mentioned pores is not specifically limited in this application, as long as their size is larger than the molecules of the gas film-forming additive but smaller than the size of the particles in the electrolyte. For example, the pores can be circular, square, rectangular, triangular, etc.

[0035] Regarding the number of the above-mentioned breathable parts, the present application does not make any specific limitation, but in order to make the ventilation rate of the breathable parts smoother and more uniform, preferably, the second part has N splicing interfaces, and the first part includes N said breathable parts, and the N said breathable parts are spliced ​​one by one at the N said splicing interfaces, wherein N ≥ 1.

[0036] In a specific embodiment, in combination Figure 2 It is described that in the gas film-forming additive release device, the second part has two splicing interfaces, and the first part includes two breathable parts 0021 and 0022, and the two breathable parts are spliced ​​to the above two splicing interfaces one by one.

[0037] The present application does not make any specific limitation on the number of the above-mentioned hollow chambers 003, but in order to enable the battery to achieve a longer cycle time, preferably, the hollow chamber includes M independent hollow sub-chambers, and each of the hollow sub-chambers is connected to the outside through at least one of the air permeable members, wherein 1<M≤N.

[0038] In a specific embodiment, in combination Figure 2 It is described that in the gas film-forming additive release device, the hollow chamber includes two independent hollow sub-chambers 0031 and 0032, and each of the hollow sub-chambers is connected to the outside through a corresponding air permeable member 0021 and 0022.

[0039] Preferably, the pore size of the air pore is P, wherein 0.3nm≤P<0.4nm. Under this condition, the air permeability rate of the air permeable member is relatively slow, which can achieve the effect of slowly releasing the gas film-forming additive, thereby helping to further improve the cycle life of the battery.

[0040] It can be understood that the volume of the hollow chamber 003 can be freely adjusted according to the volume of different batteries and the required number of cycles of different batteries; in order to ensure that there is still a large amount of gas film-forming additive after the battery is formed, preferably, the gas film-forming additive release device satisfies the following formula 1:

[0041] V0>V1+V2 Formula 1;

[0042] Wherein, V0 is the volume of the hollow chamber 003, V1 is the total pore volume of the electrode and the diaphragm in the battery, and V2 is the total volume of the gas film-forming additive that can be dissolved in the electrolyte.

[0043] Among them, the total pore volume of the electrode and diaphragm in the battery can be determined by existing methods, including but not limited to the mercury injection method or the gas adsorption method, for example, the gas adsorption method of the true density meter is used for determination: the gas pressure of helium injected into the sample cell of the true density meter is 18PSI, and at room temperature, the electrode and the diaphragm are placed in the sample cell of the true density meter in turn, and the total pore volume V1 can be measured; the total volume of the gas film-forming additive that can be dissolved in the electrolyte can be tested by conventional methods such as the static saturation method, the gas PVT determination method, the bubble point pressure method, and the equilibrium liquid sampling method.

[0044] Preferably, the material of the air-permeable member is one of polytetrafluoroethylene resin, polyethylene, polypropylene, chloroprene rubber, polyamide fiber, aramid fiber, polyester and polyvinyl alcohol fiber. The air-permeable member made of these materials has good insulation, corrosion resistance and pressure bearing capacity, and can better ensure the rate and stability of the air-permeable member releasing the gas film-forming additive.

[0045] Exemplarily, the polytetrafluoroethylene resin is e-PTFE from GORE, and the pore size is between 0.3-0.4 nm.

[0046] When the gas film-forming additive release device of the present application is used, it can be directly put into the electrolyte, or it can be connected to the inner side of the battery cell shell by ultrasonic welding, threaded connection, bonding, etc.; as a preferred embodiment, combined with Figure 1 It is explained that in the above-mentioned gas film-forming additive release device, the second part is provided with a connector 005 on the side away from the hollow chamber 003, and the connector 005 is used to connect with the inner side of the battery cell shell of the battery. The shape of the connector 005 is not specifically limited in this application, and can be sheet-shaped, dot-shaped, column-shaped, etc. The material of the connector 005 can also be selected according to the actual use situation. For example, the gas film-forming additive release device is directly put into the electrolyte for use, and the material of the connector 005 should be an insulating corrosion-resistant material; if the gas film-forming additive release device is connected to the inner side of the battery cell shell of the battery for use, the material of the connector 005 is a corrosion-resistant material, such as plastic, rubber or metal, etc., but in order to increase the supporting strength, it can be preferably a copper sheet or an aluminum sheet.

[0047] In a specific embodiment, the connector includes an adhesive layer, and the adhesive layer is used to be bonded to the inner side of the battery cell housing. The material of the adhesive layer is not specifically limited in this application, as long as it can be bonded, for example: ear glue.

[0048] As to whether the above-mentioned hollow chamber 003 needs to be filled with the required gas film-forming additive before the gas film-forming additive release device is packaged, it can be selected according to needs. For example, the hollow chamber 003 remains hollow before packaging, and is filled with the required gas film-forming additive when the release device is used. At this time, in order to facilitate the filling of the required gas film-forming additive at any time before and after packaging, in a specific embodiment, the second part 004 includes a gas inlet 0010, and the gas inlet is provided with an openable and closable sealing cover; the gas inlet is connected to the hollow chamber 003; preferably, the gas inlet is located on the side away from the breathable member. Furthermore, if the hollow chamber 003 includes a plurality of independent hollow sub-chambers, it is more preferred to set a plurality of gas inlets in the second part 004, and each of the gas inlets corresponds one-to-one to the above-mentioned plurality of hollow sub-chambers, that is, the corresponding hollow sub-chambers are connected one-to-one with each of the gas inlets.

[0049] On the other hand, the present application provides a battery, Figure 3 The battery is described in detail, including the above-mentioned gas film-forming additive release device 006, and the permeable member is at least partially immersed in the electrolyte of the battery.

[0050] Preferably, the gas film-forming additive releasing device is connected to the inner side of the battery cell shell 007 of the battery.

[0051] It can be understood that the above-mentioned battery also includes a negative electrode sheet 008 and a positive electrode sheet 009; the above-mentioned gas film-forming additive release device can be directly immersed in the electrolyte of the battery, and can also be connected to the inner side of the battery cell shell by ultrasonic welding, threaded connection, bonding, etc.

[0052] The following is a further description of the method and principle of use of the device of the present application in combination with two specific processes:

[0053] If the battery is not charged, Figure 1 The method for using the gas film-forming additive release device shown comprises the following steps:

[0054] Step S1: When the gas film-forming additive release device does not include a conductive component, it is directly placed in the electrolyte, or according to Figure 3 The connection relationship shown is connected to the inner side of the battery cell housing in advance, but it is necessary to ensure that the air permeable member is at least partially immersed in the electrolyte of the battery;

[0055] Step S2: The battery is subjected to negative pressure, and the negative pressure value reaches -60KPa. The negative pressure pipeline is closed. At this time, the gas film-forming additive in the device is quickly released and dissolved in the electrolyte. At this time, the battery starts constant current charging. The charging current is 0.01C-0.2C, and the time is 10-30 minutes. The smaller the current, the longer the charging time. During constant current charging, the gas film-forming additive and the lithium salt in the electrolyte form a solid electrolyte film (SEI film) on the surface of the negative electrode.

[0056] In the above method, step S1 starts the formation by pumping negative pressure to extract the gas in the gaps of the electrode, and the gas film-forming additive can fill these gaps more easily. During constant current charging, the gas film-forming additive and the lithium salt in the electrolyte form a relatively stable SEI film on the surface of the negative electrode. The SEI film is more stable and can ensure that the SEI film does not suffer from serious rupture during a long cycle of the battery. After the formation is completed, since there is still gas additive in the release device, it can be slowly released during the subsequent cycles of the battery to continue to provide conditions for film formation on the surface of the negative electrode, thereby helping to achieve long-cycle low attenuation of the battery.

[0057] If the battery is fully charged, Figure 1 The method for using the gas film-forming additive release device shown comprises the following steps:

[0058] Open the battery cell and put it directly into the electrolyte if the gas film-forming additive release device does not include conductive materials, or Figure 3 The connection relationship shown is previously connected to the inner side of the battery cell housing, and ensures that the gas permeable member is at least partially immersed in the electrolyte of the battery.

[0059] In the above method, the gas film-forming additive releasing device can release the gas film-forming additive during the subsequent cycles of the battery, continuously providing conditions for film formation on the surface of the negative electrode, thereby helping to achieve long-cycle and low-attenuation of the battery.

[0060] The present invention is further described below in conjunction with specific embodiments:

[0061] The following examples or comparative examples involve batteries: NCM811 (molecular formula: LiMn 0.8 Co 0.1 Ni 0.1 O2) is the positive electrode, graphite is the negative electrode, the electrolyte is 1 mol / L LiPF6 dissolved in EC / DMC / DEC (v:v:v=1:1:1), and the diaphragm is assembled using a PP / PE composite diaphragm;

[0062] The first part (breathable part) and the second part are made of e-PTFE from CORE.

[0063] Example 1

[0064] This embodiment provides a gas film-forming additive release device, such as Figure 1 As shown, it includes a shell 001 that can isolate liquid, the shell is surrounded by a hollow chamber 003 for accommodating gas film-forming additives, the shell 001 includes a first part 002 and a second part 004 that are spliced ​​to each other, the first part is a breathable member, and the breathable member includes a plurality of breathable holes; the second part 004 includes a gas inlet 0010 on a side away from the breathable member, and the gas inlet 0010 is provided with an openable and closable sealing cover; and the second part is provided with a connector 005 on a side away from the hollow chamber 003, the connector is a copper sheet, and the copper sheet includes an adhesive layer, and the adhesive layer is a tab glue; the volume V0 of the above-mentioned hollow chamber satisfies the following formula 1:

[0065] V0>V1+V2 Formula 1;

[0066] Among them, V1 is the total pore volume of the electrode and diaphragm in the battery, and V2 is the total volume of the electrolyte that can dissolve the gas film-forming additive.

[0067] Example 2

[0068] This embodiment provides a battery, such as Figure 3 As shown, it includes a battery cell shell 007, a negative electrode sheet 008, a positive electrode sheet 009, an electrolyte, a separator and a gas film-forming additive release device 006 of Example 1, and the gas film-forming additive release device is bonded to the inner side of the battery cell shell of the battery through an adhesive layer.

[0069] The battery assembly method of this embodiment includes the following steps:

[0070] Step S1: Open the sealing cover of the gas inlet in the gas film-forming additive release device, fill the hollow chamber 003 of the gas film-forming additive release device with CO2, and close the sealing cover;

[0071] Step S2: Follow Figure 3 The connection relationship shown is such that the gas film-forming additive release device is bonded to the inner side of the battery cell shell through the bonding layer, and the gas film-forming additive release device is immersed in the electrolyte to encapsulate the battery;

[0072] Step S3: During the formation stage, negative pressure is pumped onto the battery, and the negative pressure value reaches -60KPa. The negative pressure pipe is closed, and the gas film-forming additive CO2 in the sustained-release device is rapidly released into the battery and dissolved in the electrolyte. The battery then begins constant-current charging with a charging current of 0.01C-0.2C for 10-30 minutes. During constant-current charging, CO2 and lithium salts and solvents in the electrolyte form an SEI film on the surface of the negative electrode.

[0073] Comparative Example 1

[0074] The battery of this comparative example is different from that of Example 2 in that it does not include a gas film-forming additive release device. The assembly method of the battery comprises the following steps:

[0075] Step S1: Before packaging the battery, CO2 is dissolved in the electrolyte at a pressure of 60Kpa and saturated.

[0076] Step S2: During the formation stage, the battery is subjected to negative pressure, and the negative pressure value reaches -60KPa. The negative pressure pipe is closed, and the battery begins constant current charging at a charging current of 0.01C-0.2C for 10-30 minutes. During constant current charging, CO2 and lithium salts and solvents in the electrolyte form an SEI film on the surface of the negative electrode.

[0077] Performance Testing

[0078] The batteries of Example 2 and Comparative Example 1 were cycled at a charge and discharge rate of 0.2C, and the capacity of each cycle was compared with the capacity of the first cycle to determine the capacity retention rate. The capacity retention rate was calculated after 100 cycles at 25°C. The results are shown in Table 1. Figure 4 shown.

[0079] like Figure 4 As shown, the capacity retention rate of the second cycle after the formation of Example 2 and Comparative Example 1 is about 100%. In the first few cycles that follow, the capacity retention rates of Example 2 and Comparative Example 1 are close and there is no obvious attenuation, indicating that the SEI films formed in the formation stage are relatively stable, which can ensure that the capacity attenuation of the battery is small. However, after a long period of circulation, there is a significant difference between Example 2 and Comparative Example 1. This is because the gas film-forming additive of Comparative Example 1 is added to the electrolyte at one time, the content is relatively small, and it is likely to have been consumed in the film-forming process during the formation stage, so it is impossible to maintain the subsequent stable cycle of the battery. The addition of a gas additive release device in Example 2 can not only meet the film-forming requirements of the battery formation stage, but also continue to release gas additives into the electrolyte in subsequent cycles to maintain the battery cycle, thereby improving the battery cycle life.

[0080] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A gas film-forming additive release device, characterized in that: It comprises a shell capable of isolating liquid, the shell encloses a hollow chamber for accommodating gas film-forming additives, the shell comprises a first part and a second part which are spliced ​​to each other, the first part is a breathable part, and the breathable part comprises a plurality of breathable holes.

2. The gas film-forming additive release device according to claim 1, characterized in that: The second part has N splicing interfaces, the first part includes N breathable parts, and the N breathable parts are spliced ​​to the N splicing interfaces in a one-to-one correspondence, wherein N≥1.

3. The gas film-forming additive release device according to claim 1, characterized in that: The hollow chamber includes M independent hollow sub-chambers, and each of the hollow sub-chambers is connected to the outside through at least one of the air permeable members, wherein 1<M≤N.

4. The gas film-forming additive release device according to claim 1, characterized in that: The pore size of the air-permeable pore is P, wherein 0.3nm≤P<0.4nm.

5. The gas film-forming additive release device according to any one of claims 1 to 4, characterized in that: Satisfies the following formula 1: V0>V1+V2 Formula 1; Among them, V0 is the volume of the hollow chamber, V1 is the total pore volume of the electrode and the diaphragm in the battery, and V2 is the total volume of the gas film-forming additive that can be dissolved in the electrolyte.

6. The gas film-forming additive release device according to any one of claims 1 to 4, characterized in that: The material of the breathable member is one of polytetrafluoroethylene resin, polyethylene, polypropylene, chloroprene rubber, polyamide fiber, aromatic polyamide fiber, polyester and polyvinyl alcohol fiber.

7. The gas film-forming additive release device according to any one of claims 1 to 4, characterized in that: The second part is provided with a connecting piece on a side away from the hollow chamber, and the connecting piece is used to be connected to the inner side of the battery cell shell of the battery.

8. The gas film-forming additive release device according to claim 7, characterized in that: The connecting piece comprises an adhesive layer, and the adhesive layer is used for bonding and connecting with the inner side of the battery cell shell.

9. A battery, characterized in that: The battery comprises a gas film-forming additive release device as described in any one of claims 1 to 8, and the gas permeable member is at least partially immersed in the electrolyte of the battery.

10. The battery according to claim 9, characterized in that The gas film-forming additive release device is connected to the inner side of the battery cell shell.

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