Battery secondary liquid injection formation process and battery

Abstract

The invention relates to the technical field of batteries, in particular to a secondary liquid injection formation process of a battery and the battery. The secondary liquid injection formation process of the battery comprises the following steps: after primary liquid injection of the battery, performing primary formation, aging and discharging; after discharging is finished, the battery is subjected to secondary liquid injection, centrifugation and standing; and after the standing is finished, carrying out secondary formation on the battery. By adopting the secondary liquid injection formation process of the battery, the uniformity of electrolyte components in each region in the battery at each stage can be greatly improved, the positive and negative electrode interface structures of the battery are optimized, the uniformity of an interface is improved, and the states and the performances of each region in the battery tend to be consistent, so that the long-term performance of the battery and the consistency between individual batteries are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a secondary liquid injection formation process for batteries and a battery. Background Art

[0002] With the development of lithium-ion battery technology, customers have higher and higher requirements for its performance. As one of the three main materials, the electrolyte plays a vital role in the performance of the battery. Therefore, the design and setting of parameters such as the electrolyte formula, injection method, and formation process cannot be underestimated. Usually, the electrolyte components mainly include lithium salts, solvents and additives. Different components play different roles. In particular, additives are of many types, have different functions, and influence each other. Therefore, in order to give full play to their respective roles, in the preparation process of the battery, some will adopt the method of secondary injection in order to obtain better performance of the battery. Usually, since the formulas of the primary and secondary injection electrolytes are different, after the secondary injection, it is easy to cause inconsistency in the electrolyte components of various regions inside the battery.

[0003] In the related art, the positive and negative electrodes of the battery are protected in a targeted manner in stages through the method of secondary injection, in order to optimize the battery performance. However, these existing methods ignore the fact that after the secondary injection, due to the different electrolyte components of the two injections, the electrolyte components in various regions inside the battery will be inconsistent, resulting in different states and performances of various regions inside the battery. Especially for large-size batteries, this difference is particularly obvious, so that the expected effect cannot be achieved. Furthermore, due to the different states and performances of various regions inside the battery, the current density distributed on the surface of the electrode will be uneven during the charging and discharging process of the battery, resulting in the deterioration of the long-term performance of the battery, especially the deterioration of the long-term high-temperature performance of the battery. At the same time, it will also increase the individual performance differences between batteries, and consistency is difficult to ensure.

[0004] Therefore, there is an urgent need to provide a secondary liquid injection formation process to improve the long-term performance of the battery and the consistency between individual batteries. Summary of the invention

[0005] In view of this, the present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the present invention provides a battery secondary liquid injection formation process and a battery, which can improve the long-term performance of the battery and improve the consistency between individual batteries.

[0006] In order to solve the above technical problems, this application is implemented as follows:

[0007] According to one aspect of the present application, an embodiment of the present application provides a battery secondary liquid injection formation process, comprising the following steps:

[0008] After the battery is filled once, it undergoes formation, aging and discharge;

[0009] After the discharge is completed, the battery is injected with liquid for the second time, centrifuged and left to stand;

[0010] After the standing is completed, the battery is subjected to secondary formation.

[0011] In addition, the battery secondary liquid injection formation process according to the present application may also have the following additional technical features:

[0012] In some embodiments, the primary formation includes a first constant current charge and a second constant current charge performed sequentially, and a current of the second constant current charge is greater than a current of the first constant current charge.

[0013] In some embodiments, the current of the first constant current charging is 0.005C to 0.15C, and the charging time is 5min to 15min.

[0014] In some embodiments, the current of the second constant current charging is 0.02C to 1C, and the charging time is 60min to 120min.

[0015] In some embodiments, the aging temperature is 40° C. to 50° C., and the aging time is 20 h to 28 h.

[0016] In some embodiments, the discharge current of the discharge is greater than or equal to a minimum current of a formation charge, and less than or equal to a maximum current of a formation charge.

[0017] Optionally, the discharge current is 0.005C to 1C, and the discharge is to 0% SOC.

[0018] In some of the embodiments, after the first injection and before the first formation, a soaking and shelving step is also included.

[0019] In some embodiments, the centrifugation includes a first centrifugation and a second centrifugation.

[0020] In some embodiments, during the first centrifugation, the bottom of the battery faces the same direction as or opposite to the direction of the centrifugal force during centrifugation.

[0021] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, the speed of the first centrifugation is 2000-6000 rpm, and the time of the first centrifugation is 5min-30min; when the group margin of the battery is ≥91.5%, the speed of the first centrifugation is 6000-9000 rpm, and the time of the first centrifugation is 5min-30min.

[0022] In some embodiments, the bottom direction during the second centrifugation is opposite to that during the first centrifugation.

[0023] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, the speed of the second centrifugation is 2000-6000 rpm, and the time of the second centrifugation is 5min-30min; when the group margin of the battery is ≥91.5%, the speed of the second centrifugation is 6000-9000 rpm, and the time of the second centrifugation is 5min-30min.

[0024] In some embodiments, the standing includes placing the battery vertically, the standing time is ≥ 2 hours, and the standing temperature is 25° C. to 55° C.

[0025] In some embodiments, in the secondary formation step, the charge and discharge cycle is performed within a range of 5% to 90% SOC of the battery.

[0026] In some embodiments, the current of the secondary formation charge and discharge is greater than or equal to the minimum current of the primary formation charge, and less than or equal to 1.5 times the maximum current of the primary formation charge.

[0027] In some embodiments, the current range of the charging and discharging of the secondary formation is 0.005C to 1.5C.

[0028] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, the number of cycles during secondary formation is ≥1, preferably 1 to 3; when the group margin of the battery is ≥91.5%, the number of cycles during secondary formation is ≥2, preferably 2 to 5.

[0029] In some of the embodiments, after the secondary formation, a volume separation step is also included.

[0030] In some embodiments, the injection volume of the single injection accounts for 60% to 95% of the total injection volume.

[0031] In some embodiments, the electrolyte of the first injection is a first electrolyte, and the electrolyte of the second injection is a second electrolyte.

[0032] According to another aspect of the present application, an embodiment of the present application provides a battery, wherein the battery includes a battery prepared by the aforementioned battery secondary liquid injection formation process.

[0033] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0034] In the present application, after the battery is filled once, it is formed and aged once, and then discharged with a small current, which can reduce the expansion of the battery pole piece, reduce the volume of the winding core, and provide more space for the secondary injection, which is conducive to the uniform mixing of the electrolyte in the battery after the secondary injection, and will further improve the circulation and high-temperature storage of the battery. Secondly, after the secondary injection of the battery, centrifugal treatment is carried out. After centrifugal treatment, the electrolyte of the primary injection and the electrolyte of the secondary injection in the battery can be fully mixed and uniform, wherein the electrolyte of the primary injection also contains the electrolyte injected once into the electrode sheet. Furthermore, through the step of secondary formation, the SEI film after the primary injection and aging can be repaired, and its structure can be optimized and stabilized. At the same time, through the expansion and contraction of the pole piece during the charging and discharging process, the electrolyte components in the battery are further homogenized.

[0035] Furthermore, through the technical solution of the present invention, the uniformity of the electrolyte components in each area inside the battery at each stage can be greatly improved, the interface structure of the positive and negative electrodes of the battery can be optimized, the uniformity of the interface can be improved, and the state and performance of each area inside the battery can be made consistent, thereby improving the long-term performance of the battery and the consistency between individual batteries.

[0036] Additional aspects and advantages of the present application will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0037] The present application is further described below in conjunction with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and are not used to limit the scope of the present application.

[0038] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0040] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0042] In the related art, some secondary injection processes are disclosed, such as the patent with publication number CN106784589A discloses a secondary injection method for high-nickel system, which uses the additive of the first injection as the negative electrode SEI film-forming additive, and the secondary injection additive as the positive electrode CEI film-forming additive to balance the high temperature performance and kinetic performance of the high-nickel material. The patent with publication number CN104577031A discloses a secondary injection method for vinyl carbonate (VC), in which a high content of vinyl carbonate is added in the first injection, and a lower content of vinyl carbonate (VC) is added in the second injection to improve the high temperature storage and high temperature cycle performance of the battery. The patent with publication number CN102201563A discloses a solution in which the first injection does not use isopropyl carbonate (PC), and the second injection contains isopropyl carbonate (PC) to reduce the expansion of the negative electrode material and ensure the cycle performance. The patent with publication number CN114335925A discloses a method in which the first injection contains no or very little VC and contains sufficient FEC electrolyte, while the second injection contains sufficient VC and no or very little fluorine FEC electrolyte. A low-impedance SEI film is formed through the first injection to maintain good power performance, and then sufficient VC is supplemented for a second time for long-term circulation, thereby obtaining good cycle performance.

[0043] The above-mentioned existing technologies all adopt the secondary injection method. These publicly available methods are more based on theory. Through the secondary injection method, the positive and negative electrodes of the battery are protected in stages and in a targeted manner in order to optimize the battery performance. However, these existing methods all ignore that after the secondary injection, due to the different electrolyte components of the two injections, the electrolyte components of each area inside the battery will be inconsistent, resulting in different states and performances of each area inside the battery. Especially for large-sized batteries, this difference is particularly obvious, so that the expected effect cannot be achieved.

[0044] In view of this, the inventors of the present application have conducted extensive research and proposed new improvement ideas from the injection and formation process end in response to the shortcomings of the existing secondary injection process, in order to avoid or reduce the problem of inconsistent electrolyte components in various regions inside the battery and different states and performances of various regions inside the battery due to the different electrolyte components in the two injections, thereby improving the electrochemical performance of the battery. The present application is described in detail below.

[0045] In some embodiments, the present invention provides a battery secondary liquid injection formation process, comprising the following steps:

[0046] After the battery is filled once, it undergoes formation, aging and discharge;

[0047] After the discharge is completed, the battery is refilled, centrifuged and left to stand;

[0048] After the rest period, the battery is subjected to secondary charge.

[0049] In the embodiments of the present application, the provided battery secondary liquid injection formation process can be used to alleviate the problem that the states and performances of various regions inside the battery are different, which affects the electrochemical performance of the battery, which exists in the current battery secondary liquid injection method. In general, the battery secondary liquid injection formation process includes the steps of primary liquid injection, primary formation, aging, discharge, secondary liquid injection, centrifugation, standing and secondary formation, that is, the battery is injected twice, and the electrolytes used in the two injections can be different, and the steps of primary formation, aging, discharge, etc. are also arranged between the primary liquid injection and the secondary liquid injection, and the steps of centrifugation, standing and secondary formation are also arranged after the secondary liquid injection.

[0050] It should be pointed out that in addition to the above-mentioned process steps, other steps can be flexibly selected and adjusted, such as setting a standing step after the second liquid injection and before centrifugation, etc. This embodiment does not limit this.

[0051] Compared with the conventional secondary liquid injection formation method, firstly, the present application performs a formation and aging after the battery is injected once, and then discharges, and the discharge preferably adopts a small current discharge method, so that the expansion of the battery pole piece can be reduced, the volume of the winding core can be reduced, and more space can be provided for the secondary liquid injection, which is conducive to the uniform mixing of the electrolyte in the battery after the secondary liquid injection, and will further improve the battery's circulation and high-temperature storage. Secondly, in the secondary liquid injection formation process of the present application, centrifugal treatment is performed after the secondary liquid injection. After the centrifugal treatment, the electrolyte of the primary liquid injection and the electrolyte of the secondary liquid injection in the battery can be fully mixed and uniform, wherein the electrolyte of the primary liquid injection also contains the electrolyte injected once into the electrode sheet, that is, the mixed electrolyte can be fully infiltrated again in various regions of the battery, which is conducive to improving the uniformity of the electrolyte components in various regions of the battery. Thirdly, through the secondary formation step, the SEI film can be repaired after primary injection aging, and its structure can be optimized and stabilized. At the same time, the expansion and contraction of the electrode during the charging and discharging process can further homogenize the electrolyte components in the battery.

[0052] Therefore, the battery secondary liquid injection formation process of the present application can greatly improve the uniformity of the electrolyte components in each region inside the battery at each stage, optimize the interface structure of the positive and negative electrodes of the battery, improve the uniformity of the interface, and make the state and performance of each region inside the battery consistent, thereby facilitating improving the long-term performance of the battery and the consistency between individual batteries.

[0053] In some embodiments, the battery group margin is ≥ 89%. Preferably, the battery group margin is ≥ 90%. As an example, the battery group margin can be 89%, 90%, 96%, 97%, 98% or greater than 98%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0054] In the present application, the secondary liquid injection formation process of the battery is applicable to batteries with a group margin greater than or equal to 89%, preferably more than 90%. It should be understood that the battery group margin mainly refers to the gap left between each single battery in a battery pack. The battery group margin has a certain influence on the performance of the battery. Generally, improving the battery group margin helps to improve the quality of the battery and the safety of the battery. In addition, a group margin that is too large or too small will have an adverse effect on the performance of the battery pack. For example, a group margin that is too large will lead to a reduction in the utilization rate of the internal space of the battery pack, thereby reducing the energy density of the battery pack; and a group margin that is too small may cause the batteries to squeeze each other when they expand, and even cause safety accidents.

[0055] In the present application, in the secondary liquid injection formation process of the battery, the setting of the specific operating conditions of some operating steps is related to the group margin of the battery, such as the centrifugation step, the secondary formation step, etc. For different group margins, the specific operating parameters can be adaptively adjusted to make the electrolyte more fully mixed and uniform. This is because, relatively speaking, the higher the group margin, the more difficult it is to mix the electrolyte evenly. Therefore, setting different operating parameters for batteries with different group margins is more conducive to improving the uniformity of the electrolyte components in each area inside the battery at each stage.

[0056] It should be pointed out that in the battery secondary liquid injection formation process of the present application, different electrolytes may be used for the primary injection and the secondary injection, that is, the composition of the electrolyte of the primary injection and the electrolyte of the secondary injection is different. For example, the additives in the electrolyte of the primary injection and the electrolyte of the secondary injection are different, and / or the electrolyte salts in the electrolyte of the primary injection and the electrolyte of the secondary injection are different, and / or the organic solvents in the electrolyte of the primary injection and the electrolyte of the secondary injection are different. The battery secondary liquid injection formation process of the present application is suitable for scenarios where different electrolytes are used for secondary injection, and the specific types or components of the electrolytes used in the primary injection and the secondary injection are not limited, as long as the electrolytes used in the two injections are different and do not limit the purpose of this application.

[0057] In some embodiments, the electrolytes injected twice can be different electrolytes. For example, a small amount of high voltage resistant electrolyte containing film-forming aids is used for primary electrolyte injection for high voltage formation, and a large amount of conventional electrolyte containing gas generation inhibitors is used for secondary electrolyte injection for conventional voltage volume division and circulation.

[0058] In some specific embodiments, the secondary liquid injection formation process of the battery specifically includes the following steps S1 to S6:

[0059] S1: After the battery is filled once, it undergoes formation, aging and discharge.

[0060] In some embodiments, after the first injection and before the first formation, a soaking and resting step is also included.

[0061] The step S1 specifically includes: firstly injecting liquid into the battery, after the injection, placing the battery for soaking, and then sequentially performing formation, aging and discharging.

[0062] Preferably, the discharge is performed with a small current, which can reduce the expansion of the battery pole piece, reduce the volume of the winding core, provide more space for secondary injection, and also facilitate uniform mixing of the electrolyte after the secondary injection and in the battery.

[0063] In step S1, the steps of primary formation and aging can be performed in a conventional manner in the art, such as using conventional process parameters in the art, and this application does not limit this.

[0064] In some embodiments, the injection volume of a single injection accounts for 60% to 95% of the total injection volume. Preferably, the injection volume of a single injection accounts for 75% to 90% of the total injection volume. As an example, the injection volume of a single injection can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc. of the total injection volume, and of course it can also be other values ​​within the above range, which are not limited here. Those skilled in the art are informed that the total injection volume is the sum of the injection volume of a single injection and the injection volume of a secondary injection.

[0065] In some embodiments, the soaking and placing time is 2 to 4 hours. As an example, the soaking and placing time can be 2 hours, 3 hours, or 4 hours, and of course, it can also be other values ​​within the above range, which is not limited here. The soaking and placing can be performed at room temperature.

[0066] After the infiltration and storage, it can ensure that the electrolyte fully infiltrates the electrode, forms a stable SEI film, removes bubbles, and balances the electrolyte distribution.

[0067] In some embodiments, a formation includes a first constant current charge and a second constant current charge performed sequentially, and the current of the second constant current charge is greater than the current of the first constant current charge. The second constant current charge current being greater than the first constant current charge current can ensure that the chemical reaction of the battery in the formation process is more gentle and reduces side reactions, which helps to form a more stable SEI film, and can also optimize the electrode structure and improve the safety and consistency of the battery.

[0068] In some embodiments, the current of the first constant current charging is 0.005C to 0.15C, preferably 0.05C to 0.15C, and more preferably 0.08C to 0.1C. As an example, the current of the first constant current charging can be 0.005C, 0.01C, 0.015C, 0.025C, 0.035C, 0.045C, 0.055C, 0.075C, 0.085C, 0.095C, 0.1C, 0.12C, 0.13C, 0.15C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0069] In some embodiments, the first constant current charging time is 5 min to 15 min. As an example, the first constant current charging time can be 5 min, 6 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 15 min, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0070] In some embodiments, the current of the second constant current charging is 0.02C to 1C, preferably 0.1C to 0.5C, and more preferably 0.2C to 0.3C. As an example, the current of the second constant current charging can be 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.1C, 0.3C, 0.5C, 0.6C, 0.7C, 1C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0071] In some embodiments, the second constant current charging time is 60 min to 120 min. As an example, the second constant current charging time can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0072] It should be noted that the values ​​of the first constant current charging current and the second constant current charging current need to satisfy that the second constant current charging current is greater than the first constant current charging current.

[0073] In some embodiments, the aging temperature is 40° C. to 50° C., preferably 45° C. As an example, the aging temperature can be 40° C., 41° C., 42° C., 43° C., 44° C., 45° C., 46° C., 47° C., 48° C., 49° C., 50° C., etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0074] In some embodiments, the aging time is 20 hours to 28 hours, preferably 24 hours. As an example, the aging time can be 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours, 28 hours, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0075] In the present application, after aging, the battery is discharged with a small current. In some embodiments, the discharge current is greater than or equal to the minimum current of a formation charge and less than or equal to the maximum current of a formation charge.

[0076] Exemplarily, the discharge current is 0.005C~1C, and the discharge is to 0% SOC; preferably, the discharge current is 0.01C~0.5C. For example, the discharge current can be 0.005C, 0.01C, 0.015C, 0.025C, 0.035C, 0.045C, 0.055C, 0.075C, 0.085C, 0.095C, 0.1C, 0.12C, 0.13C, 0.15C, 0.3C, 0.5C, 0.6C, 0.7C, 1C, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0077] The present application can reduce the expansion of the battery pole piece and the volume of the winding core by discharging the battery with a small current after the primary formation, thereby providing more space for the secondary injection, thereby facilitating the uniform mixing of the electrolyte in the battery after the secondary injection, and further improving the battery's circulation and high-temperature storage. In addition, if the discharge current of the discharge step is too large, it will also cause lithium precipitation, which will affect the negative electrode interface. Therefore, by adopting a small current discharge method and controlling the discharge current within the above range, it helps to avoid or reduce lithium precipitation and avoid the impact on the negative electrode interface.

[0078] S2: After the discharge is completed, the battery is filled with liquid for the second time and then centrifuged for the first time.

[0079] In step S2, after the discharge step of step S1 is completed, the battery is injected with liquid for the second time, and after the battery is injected with liquid for the second time, it is sealed, and after sealing, the first centrifugation is performed.

[0080] Optionally, the injection volume of the secondary injection accounts for 5% to 40% of the total injection volume. Preferably, the injection volume of the secondary injection accounts for 10% to 25% of the total injection volume.

[0081] In some embodiments, during the first centrifugation, the bottom of the battery faces the same direction as or opposite to the direction of the centrifugal force during centrifugation.

[0082] Optionally, in step S2, when performing the first centrifugal treatment, the battery is placed in a centrifuge along the lateral direction of the battery (winding core) with the bottom facing outwards for centrifugation.

[0083] The specific operating parameters of the first centrifugal treatment are related to the group margin of the battery. For example, in some embodiments, when the group margin of the battery is ≥89% and <91.5%, that is, 89%≤group margin<91.5%, the speed of the first centrifugation is 2000-6000 rpm. As an example, the speed of the first centrifugation can be 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0084] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, that is, 89%≤group margin<91.5%, the time of the first centrifugation is 5min to 30min. As an example, the time of the first centrifugation can be 5min, 10min, 15min, 20min, 25min, 30min, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0085] In some embodiments, when the battery group margin is ≥91.5%, the speed of the first centrifugation is 6000-9000 rpm. As an example, the speed of the first centrifugation can be 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0086] In some embodiments, when the battery group margin is ≥91.5%, the time for the first centrifugation is 5 min to 30 min. As an example, the time for the first centrifugation can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0087] It should be noted that the centrifuge speed is related to the group margin of the battery. The higher the group margin, the more difficult it is to mix the electrolyte. Therefore, when the group margin is high, a higher centrifuge speed is set. In this way, the electrolyte can be fully settled to the bottom, promoting the full mixing of the electrolyte components, thereby improving the uniformity of the positive and negative electrode interfaces of the battery, making the state and performance of each area inside the battery consistent, thereby improving the long-term performance of the battery and the consistency between individual batteries.

[0088] S3: After the first centrifugation is completed, a second centrifugation is performed.

[0089] In some embodiments, the bottom direction during the second centrifugation is opposite to that during the first centrifugation.

[0090] Optionally, in step S3, after the first centrifugation to allow the electrolyte to fully sink to the bottom, the battery is turned over and the battery (winding core) is centrifuged along the lateral direction with the bottom facing inward, that is, the battery is centrifuged for a second time to allow the electrolyte injected for the first time and the electrolyte injected for the second time in the battery to be fully mixed and evenly mixed, and the electrolyte contains the electrolyte injected once and infiltrated into the battery electrode.

[0091] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, that is, 89%≤group margin<91.5%, the speed of the second centrifugation is 2000-6000 rpm. As an example, the speed of the second centrifugation can be 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0092] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, that is, 89%≤group margin<91.5%, the time of the second centrifugation is 5min to 30min. As an example, the time of the second centrifugation can be 5min, 10min, 15min, 20min, 25min, 30min, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0093] In some embodiments, when the battery group margin is ≥91.5%, the speed of the second centrifugation is 6000-9000 rpm, and the time of the second centrifugation is 5-30 min. As an example, the speed of the second centrifugation can be 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0094] In some embodiments, when the battery group margin is ≥91.5%, the second centrifugation time is 5 min to 30 min. As an example, the second centrifugation time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0095] It should be noted that the centrifugal speed is related to the group margin of the battery. The higher the group margin, the more difficult it is to mix the electrolyte. Therefore, when the group margin is high, a higher centrifugal speed is set. In this way, after the second centrifugation, the electrolyte of the first injection and the electrolyte of the second injection in the battery can be fully mixed, which can greatly improve the uniformity of the electrolyte components in each area of ​​the battery at each stage.

[0096] S4: Let the battery after the second centrifugation stand.

[0097] In some embodiments, the resting includes placing the battery vertically.

[0098] In step S4, after the battery is centrifuged twice, the battery is taken out of the centrifuge, placed bottom-down vertically for a certain period of time to allow the mixed electrolyte to fully permeate all areas of the battery again.

[0099] In some embodiments, the standing time is ≥ 2 hours; preferably, the standing time is 2 hours to 8 hours. As an example, the standing time can be 2 hours, 4 hours, 5 hours, 8 hours, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0100] In some embodiments, the static temperature is 25°C to 55°C; preferably, the static temperature is 25°C to 45°C. As an example, the static temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0101] Therefore, by controlling the time and temperature of the above-mentioned standing step within the above-mentioned range, the mixed electrolyte can be fully re-permeated in various regions within the battery, which is beneficial to improving the uniformity of various regions within the battery.

[0102] S5: After the battery has been placed vertically for more than 2 hours, it is subjected to a small current charge and discharge cycle within a certain SOC range, i.e. secondary formation.

[0103] In step S5, the secondary formation treatment is mainly carried out. After the above-mentioned battery has been placed vertically for more than 2 hours, it is subjected to a small charge and discharge cycle, i.e., the secondary formation, which can repair the SEI after primary injection aging, optimize and stabilize its structure, and at the same time, the expansion and contraction of the electrode during the charging and discharging process can further make the electrolyte components in the battery uniform.

[0104] In some embodiments, in the secondary formation step, the charge and discharge cycle is performed within the range of 5% to 90% SOC of the battery, and preferably, the charge and discharge cycle is performed within the range of 30% to 70% SOC of the battery. As an example, in the secondary formation step, the battery can be charged to 90% SOC, discharged to 5% SOC, and complete a charge and discharge cycle, or charged to 80% SOC, discharged to 10% SOC, and complete a charge and discharge cycle, or charged to 70% SOC, discharged to 30% SOC, and complete a charge and discharge cycle. That is, during the charge and discharge cycle, the charge and discharge can be any value within the above SOC range.

[0105] In some embodiments, the current of the secondary formation charge and discharge is greater than or equal to the minimum current of the primary formation charge, and less than or equal to 1.5 times the maximum current of the primary formation charge. By limiting the charge and discharge currents to this range, the negative electrode interface can be optimized to prevent lithium deposition.

[0106] Exemplarily, the range of the charging and discharging current of the secondary formation is 0.005C to 1.5C; preferably, the range of the charging and discharging current of the secondary formation is 0.1C to 1C. For example, the charging current of the secondary formation can be 0.005C, 0.01C, 0.015C, 0.025C, 0.035C, 0.045C, 0.055C, 0.075C, 0.085C, 0.095C, 0.1C, 0.12C, 0.13C, 0.15C, 0.3C, 0.5C, 0.6C, 0.7C, 1C, 1.5C, etc., and of course, it can also be other values ​​within the above range, which is not limited here. The discharge current of the secondary formation can be 0.005C, 0.01C, 0.015C, 0.025C, 0.035C, 0.045C, 0.055C, 0.075C, 0.085C, 0.095C, 0.1C, 0.12C, 0.13C, 0.15C, 0.3C, 0.5C, 0.6C, 0.7C, 1C, 1.5C, etc., and of course, it can also be other values ​​within the above range, which are not limited here. Among them, the charge and discharge currents of the secondary formation can be the same or different.

[0107] In some embodiments, when the group margin of the battery is ≥89% and <91.5%, that is, 89%≤group margin<91.5%, the number of cycles during secondary formation is ≥1, preferably 1 to 3. As an example, when the group margin of the battery is ≥89% and <91.5%, the number of cycles during secondary formation can be 1, 2, 3, 4, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0108] In some embodiments, when the group margin of the battery is ≥91.5%, the number of cycles during the secondary formation is ≥2, preferably 2 to 5. As an example, when the group margin of the battery is ≥91.5%, the number of cycles during the secondary formation can be 2, 3, 4, 5, etc., and of course it can be other values ​​within the above range, which is not limited here.

[0109] The number of cycles during the above-mentioned secondary formation is related to the group margin of the battery. The higher the group margin of the battery, the more difficult it is to mix the electrolyte evenly, so multiple small current charging and discharging mixing are required.

[0110] S6: After the battery is formed by the second injection, it is finally divided into capacities to obtain the finished battery.

[0111] In step S6, the main purpose is to perform capacity division processing, and the specific operation method of the capacity division processing can adopt a method known in the art, which is not limited thereto.

[0112] Thus, according to the above technical solution, after the battery is injected once, it is formed and aged once, and then discharged, which can reduce the expansion of the battery pole piece, reduce the volume of the winding core, and provide more space for the secondary injection, which is conducive to the uniform mixing of the electrolyte in the battery after the secondary injection, and will further improve the battery's circulation and high temperature storage. More specifically, the primary formation includes the first constant current charging and the second constant current charging performed in sequence, and the current of the second constant current charging is greater than the current of the first constant current charging. Among them, the current of the second constant current charging is greater than the current of the first constant current charging, which can ensure that the chemical reaction of the battery in the primary formation process is more gentle and reduces side reactions, which helps to form a more stable SEI film, and can also optimize the electrode structure and improve the safety and consistency of the battery. Secondly, after two centrifugations in opposite directions, the electrolyte of the primary injection and the electrolyte of the secondary injection in the battery can be fully mixed and uniform, wherein the electrolyte of the primary injection also includes the electrolyte injected into the electrode sheet once, which can greatly improve the uniformity of the electrolyte components in each region of the battery at each stage. Furthermore, the secondary formation step can repair the SEI film after primary injection aging, optimize and stabilize its structure, and at the same time, further homogenize the electrolyte components in the battery through the expansion and contraction of the electrode during the charging and discharging process.

[0113] Based on the same inventive concept, an embodiment of the present application provides a battery, which includes a battery prepared by the aforementioned battery secondary liquid injection formation process.

[0114] The battery is prepared by the aforementioned secondary liquid injection formation process, and therefore has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0115] In the embodiment of the present application, the battery may be a secondary battery. Optionally, the secondary battery may be a lithium-ion battery, or a sodium-ion battery, or a magnesium-ion battery, etc. The present application does not limit the specific type of the battery.

[0116] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this area or the product instructions are used. If the manufacturer of the reagents, materials or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0117] Battery Preparation

[0118] The battery is a 150Ah large-size aluminum shell square battery.

[0119] (1) The composition of the positive electrode slurry includes:

[0120] The mass ratio of lithium iron phosphate (LFP): conductive carbon black (SuperP): binder polyvinylidene fluoride (PVDF_5130): dispersant polyvinyl pyrrolidone (PVP_30) is 100:2:2.5:0.5.

[0121] (2) The composition of the negative electrode slurry includes:

[0122] The mass ratio of graphite: conductive agent (SuperP): binder styrene-butadiene rubber (SBR): binder sodium carboxymethyl cellulose (CMC_500): water is 100:2:2:0.8:99.

[0123] (3) Diaphragm: Polyethylene film is used.

[0124] (4) Electrolyte:

[0125] The electrolyte during the first injection and the electrolyte during the second injection both include lithium salt, organic solvent and additives.

[0126] Among them, the electrolyte during the first injection includes 13% lithium hexafluorophosphate (LiPF6), organic solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), the volume ratio of EC, EMC and DMC is 3:5:2, and additives include 1% vinylene carbonate (VC) and 1% fluoroethylene carbonate (FEC).

[0127] The electrolyte during the secondary injection includes 13% lithium hexafluorophosphate (LiPF6), organic solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), the volume ratio of EC, EMC and DMC is 3:5:2, and additives include 16% vinylene carbonate (VC) and 1% fluoroethylene carbonate (FEC).

[0128] (5) Battery preparation

[0129] The positive electrode sheet, separator, and negative electrode sheet are bonded, wound, and the tabs are welded to obtain a battery cell. The bare battery cell is placed in the battery outer packaging, and preparation is made for the secondary liquid injection and formation process of the battery.

[0130] Example 1

[0131] The secondary liquid injection formation process of the battery includes the following steps:

[0132] Step S1, injecting the battery to be injected with liquid once (the amount of liquid injected once accounts for 90% of the total amount of liquid injected), after being soaked, formed once, and aged, discharging it with a small current, and after the discharge is completed, injecting it with liquid twice;

[0133] Step S2, after the battery is filled with liquid for the second time and sealed, the battery is placed in a centrifuge along the transverse direction of the winding core with the bottom facing outward for centrifugation (one centrifugation);

[0134] Step S3, after the electrolyte has fully settled to the bottom, the battery is turned over, and the battery is centrifuged continuously along the transverse direction of the winding core with the bottom facing inward (secondary centrifugation);

[0135] Step S4: After the second centrifugation, take out the battery and place it vertically with the bottom facing downwards;

[0136] Step S5, after the battery is placed vertically, a small current charge and discharge cycle is performed on it within a certain SOC range, i.e., secondary formation;

[0137] Step S6: After the battery is formed by the second injection, the capacity is finally divided to obtain a finished battery.

[0138] The parameters of the secondary liquid injection formation step in Example 1 are detailed in Tables 1 and 2.

[0139] The specific parameters of the liquid injection formation of Examples 2-14 and Comparative Examples 1-4 are shown in Table 1 and Table 2. Among them, the liquid injection volume of Example 14 accounts for 75% of the total liquid injection volume, and the rest are the same as Example 1.

[0140] Table 1

[0141]

[0142]

[0143] Table 2

[0144]

[0145]

[0146] Note: “ / ” in Table 1 and Table 2 means that the step was not implemented in this embodiment or comparative example.

[0147] Performance Testing

[0148] (1) 45°C cycle test: The lithium ion batteries prepared in each embodiment and comparative example were cycled at 45°C, 1C / 1C for 1500 cycles, and the battery capacity retention rate and DCR increase rate were tested. Specifically, the lithium ion batteries prepared in each embodiment and comparative example were left at 45°C for 5 minutes, discharged at 1C to 2.5V, left at 15 minutes, charged at 1C constant current to 3.65V, left at 15 minutes, discharged at 1C to 2.5V, recorded the discharge capacity as C1, and obtained DCR1 according to the discharge curve, and the above charge and discharge process was repeated for 1500 cycles, and the capacity Cn at the 1500th cycle was recorded, and DCRn was obtained according to the 1500th cycle discharge curve, and the capacity retention rate = Cn / C1×100%, and the DCR increase rate = ((DCRn / DCR1)-1)×100%.

[0149] (2) 60°C high temperature storage test: After the lithium-ion batteries prepared in the embodiments and comparative examples were stored at 60°C for 100 days, the capacity remaining rate, capacity recovery rate and DCR increase rate were tested respectively. Specifically, the lithium ion batteries prepared in the embodiments and comparative examples are first charged to 3.65V at 1C constant current and constant voltage at 25°C, with a cut-off current of 0.05C, and then discharged to 2.5V at 1C constant current, and the discharge capacity C0 is recorded. At the same time, DCR1 is obtained according to the discharge curve. The battery is then charged with 1C constant current and constant voltage, and the cut-off voltage is 0.05C. It is transferred to a 60°C oven for high-temperature storage for 100 days and then taken out. It is discharged to 2.5V at 1C constant current at 25°C, and the discharge capacity at this time is recorded as the residual capacity C1. Then, the battery is charged to 3.65V at 1C constant current and constant voltage, with a cut-off voltage of 0.05C, and then discharged to 2.5V at 1C constant current. The discharge capacity is determined as the reversible capacity C2. At the same time, DCR2 is obtained according to the discharge curve. The capacity residual rate = C1 / C0×100%, the capacity recovery rate = C2 / C0×100%, and the DCR rise rate = ((DCR2 / DCR1)-1)×100%.

[0150] The specific test results are shown in Table 3.

[0151] Table 3

[0152]

[0153] Judging from the test data, after the battery has gone through the first injection, immersion and storage, the first formation and aging, the battery cycle performance and high-temperature storage performance can be significantly improved by adding small current discharge, secondary injection, centrifugal mixing of the components of the electrolyte in the battery, vertical standing after centrifugation, secondary formation, and small current circulation after secondary formation. The capacity retention rate and recovery rate are effectively improved, the increase in DCR is effectively suppressed, and the overall performance of the battery is further improved.

[0154] Specifically, by comparing the data of Examples 1-3, it can be seen that before the secondary injection of the battery, the battery cycle and high temperature storage performance are improved by increasing the small current discharge, and the discharge current is small (such as the discharge current is about 0.2C), and the performance is better. That is, after the primary formation of the battery, the small current discharge can improve the electrical performance and storage performance of the battery.

[0155] By comparing the data of Example 1, Example 5 and Example 6, and comparing the data of Example 8 and Example 9, it can be seen that the battery cycle and high-temperature storage performance are improved by appropriately increasing the centrifugal speed and the centrifugal time, and the higher the group margin, the greater the impact.

[0156] By comparing the data of Example 1 and Example 7, and comparing the data of Example 9 and Example 10, it can be seen that the battery cycle and high-temperature storage performance are improved by appropriately increasing the vertical placement time and the vertical placement temperature.

[0157] By comparing the data of Example 1, Example 2 and Example 4, and comparing the data of Example 9 and Example 12, it can be seen that by increasing the secondary formation and small current cycles, the battery cycle and high-temperature storage performance are improved, and appropriately increasing the number of small current cycles is also conducive to performance improvement.

[0158] Comparing the data of Example 9 and Example 11, it can be seen that the battery cycle and high-temperature storage performance are improved by appropriately increasing the secondary formation and low-current cycle SOC. Comparing the data of Example 9 and Example 13, it can be seen that appropriately increasing the secondary formation and low-current cycle current has little effect on the battery cycle and high-temperature storage performance.

[0159] Through the analysis and comparison of Example 1 and Comparative Examples 1-4, it can be seen that after the secondary liquid injection of the battery, the centrifugation step is added, and the battery cycle and high-temperature storage performance are improved; for example, the capacity retention rate of Comparative Example 1 after the 45°C cycle test is much lower than that of Example 1. Adding secondary formation to the battery after the secondary liquid injection can also improve the battery's cycle and high-temperature storage performance. In addition, when the group margin is low, the battery cycle and high-temperature storage performance can also reach a good level without centrifugation, secondary formation and low current circulation. It can be seen that the technical solution of the present invention can effectively alleviate the problems faced by batteries with higher group margins.

[0160] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0161] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0162] It should be noted that the term "and / or" or " / " used in this document is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The singular forms of "a", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0163] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery secondary liquid injection formation process, characterized in that: The following steps are involved: After the battery is filled once, it undergoes formation, aging and discharge; After the discharge is completed, the battery is injected with liquid for the second time, centrifuged and left to stand; After the standing is completed, the battery is subjected to secondary formation.

2. The battery secondary liquid injection formation process according to claim 1, characterized in that: The primary formation includes a first constant current charge and a second constant current charge performed sequentially, wherein the current of the second constant current charge is greater than the current of the first constant current charge; Preferably, the current of the first constant current charging is 0.005C to 0.15C, and the charging time is 5min to 15min; Preferably, the current of the second constant current charging is 0.02C to 1C, and the charging time is 60min to 120min; Preferably, the aging temperature is 40° C. to 50° C., and the aging time is 20 h to 28 h.

3. The battery secondary liquid injection formation process according to claim 1, characterized in that: The discharge current of the discharge is greater than or equal to the minimum current of a formation charge, and less than or equal to the maximum current of a formation charge. Preferably, the discharge current is 0.005C to 1C, and the discharge is to 0% SOC; And / or, after the first injection and before the first formation, the method further includes a step of soaking and shelving.

4. The battery secondary liquid injection formation process according to claim 1, characterized in that: The centrifugation includes a first centrifugation and a second centrifugation; During the first centrifugation, the bottom of the battery faces the same direction as or opposite to the direction of the centripetal force during centrifugation; Preferably, when the group margin of the battery is ≥89% and <91.5%, the speed of the first centrifugation is 2000 to 6000 rpm, and the time of the first centrifugation is 5 min to 30 min; When the group margin of the battery is ≥91.5%, the rotation speed of the first centrifugation is 6000-9000 rpm, and the time of the first centrifugation is 5-30 min.

5. The battery secondary liquid injection formation process according to claim 4, characterized in that: The bottom direction during the second centrifugation is opposite to that during the first centrifugation; Preferably, when the group margin of the battery is ≥89% and <91.5%, the speed of the second centrifugation is 2000 to 6000 rpm, and the time of the second centrifugation is 5 min to 30 min; When the group margin of the battery is ≥91.5%, the rotation speed of the second centrifugation is 6000-9000 rpm, and the time of the second centrifugation is 5-30 min.

6. The battery secondary liquid injection formation process according to claim 1, characterized in that: The standing still includes placing the battery vertically, the standing still time is ≥ 2 hours, and the standing still temperature is 25° C. to 55° C.

7. The battery secondary liquid injection formation process according to claim 1, characterized in that: In the secondary formation step, the charge and discharge cycle is performed within the range of 5% to 90% SOC of the battery; Preferably, the current of the charge and discharge of the secondary formation is greater than or equal to the minimum current of the primary formation charge, and less than or equal to 1.5 times the maximum current of the primary formation charge; Preferably, the current range of the charging and discharging of the secondary formation is 0.005C to 1.5C.

8. The battery secondary liquid injection formation process according to claim 7, characterized in that: When the group margin of the battery is ≥89% and <91.5%, the number of cycles during secondary formation is ≥1, preferably 1 to 3; When the group margin of the battery is ≥91.5%, the number of cycles during secondary formation is ≥2 cycles, preferably 2 to 5 cycles; Preferably, after the secondary formation, a volume separation step is also included.

9. The battery secondary liquid injection formation process according to any one of claims 1 to 8, characterized in that: The injection volume of the one injection accounts for 60% to 95% of the total injection volume.

10. A battery, characterized in that: The battery comprises a battery prepared by the battery secondary liquid injection formation process according to any one of claims 1 to 9.

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