Lithium ion battery and formation method thereof

Abstract

The invention provides a lithium ion battery and a formation method thereof. The method comprises the following steps: S1, injecting an electrolyte into the lithium ion battery to obtain a lithium ion battery to be formed; s2, performing constant-current charging on the to-be-formed lithium ion battery to a first voltage by adopting a first multiplying power; s3, carrying out floating charge on the to-be-formed lithium ion battery subjected to constant-current charging by adopting a first voltage and a second multiplying power, wherein the time is greater than or equal to 2 hours; s4, performing constant-current discharge on the to-be-formed lithium ion battery subjected to floating charge to a second voltage by adopting a third multiplying power; wherein the second voltage is lower than the first voltage; s5, performing constant-voltage discharge on the to-be-formed lithium ion battery subjected to constant-current discharge by adopting a second voltage until the constant-voltage discharge is not lower than 85% of the designed rated capacity, wherein the time is longer than or equal to 2 hours; a standing process is further included between the steps. By adopting the method, active substances in the lithium ion battery can be fully activated, and the capacity exerting and cycling stability of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery preparation, and in particular to a lithium ion battery and a formation method thereof. Background Art

[0002] The lithium-ion battery formation process is a key step in battery manufacturing, which aims to activate the active materials in the battery and promote the effective combination of lithium ions and electrode materials, so as to optimize the battery performance. This process is not only complex, but also has a significant impact on the performance of the battery (such as capacity, cycle life and safety). The traditional formation process involves repeated cycles of charging and discharging to ensure sufficient migration of lithium ions between the positive and negative electrodes to form a stable embedded structure. During the charging stage, lithium ions migrate from the ternary lithium material of the positive electrode to the crystal surface, escape from the positive electrode material, enter the electrolyte under the action of the electric field force, pass through the diaphragm, and migrate to the crystal surface of the negative electrode material through the electrolyte, and finally embed into the negative electrode material. Conversely, during the discharge stage, lithium ions are deintercalated from the negative electrode material, pass through the electrolyte and the diaphragm, and then return to the positive electrode material.

[0003] However, most of the existing formation methods have the problem of insufficient reaction between active materials and lithium ions, which leads to a gap between the theoretical capacity of the battery and the actual available capacity, thus affecting the overall performance and application range of the battery. In addition, the number of charge and discharge cycles in the existing formation methods is large, and each cycle takes a certain amount of time to complete, which significantly increases the production cycle of the battery, reduces production efficiency, and increases production costs.

[0004] In summary, researching and developing a lithium-ion battery formation method is of great significance to improving the capacity of lithium-ion batteries, improving formation efficiency and reducing production costs. Summary of the invention

[0005] The main purpose of the present invention is to provide a formation method for a lithium ion battery to solve the problem that the formation method in the prior art is difficult to fully activate the active material inside the lithium ion battery, thereby limiting the capacity of the lithium ion battery and the existing formation method has low efficiency and high energy consumption.

[0006] In order to achieve the above-mentioned object, the present invention provides a formation method of a lithium ion battery on one hand, and the formation method comprises: step S1, injecting an electrolyte into a lithium ion battery to obtain a lithium ion battery to be formed; step S2, using a first rate to perform constant current charging on the lithium ion battery to be formed to a first voltage; step S3, using the first voltage and the second rate to float charge the lithium ion battery to be formed that has completed constant current charging, and the floating charge time is ≥2h; step S4, using a third rate to perform constant current discharge on the lithium ion battery to be formed that has completed float charging to a second voltage; wherein the second voltage is lower than the first voltage; step S5, using the second voltage to perform constant voltage discharge on the lithium ion battery to be formed that has completed constant current discharge to not less than 85% of the designed rated capacity, and the constant voltage discharge time is ≥2h; a first static process is also included between step S2 and step S3, a second static process is also included between step S3 and step S4, and a third static process is also included between step S4 and step S5.

[0007] Furthermore, in step S5, the lithium-ion battery to be formed that has completed constant current discharge is subjected to constant voltage discharge to 85-100% of the designed rated capacity, and the constant voltage discharge time is 2-5 hours.

[0008] Furthermore, the floating charge time is 2 to 10 hours.

[0009] Furthermore, the formation method also includes: step S6, using a fourth rate to perform at least one constant current charge and discharge cycle on the lithium ion battery to be formed that has completed constant voltage discharge, wherein the voltage interval of the constant current charge and discharge cycle is between the first voltage and the second voltage; and a fourth static process is also included between step S5 and step S6.

[0010] Furthermore, the fourth standing time is 10 to 30 minutes.

[0011] Furthermore, the floating charge time is 5 to 8 hours, and the number of constant current charge and discharge cycles in step S6 is ≤ 3 cycles, preferably 1 or 2 cycles.

[0012] Further, in step S6, the fourth magnification is 0.15-1C.

[0013] Furthermore, the positive electrode material in the lithium-ion battery to be formed is selected from one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide and lithium iron phosphate, and the negative electrode material is lithium titanate negative electrode material.

[0014] Further, in step S2, the first magnification is 0.15-1C.

[0015] Furthermore, the first voltage is ≥2.7V, preferably 2.7-3.0V.

[0016] Furthermore, in step S3, the second magnification is 0.1-1C.

[0017] Further, in step S4, the third magnification is 0.15-1C.

[0018] Furthermore, the second voltage is ≤1.8V, preferably 1.5-1.8V.

[0019] Furthermore, the above-mentioned formation method also includes: step S7, repeating the floating charge process in step S3 at least once; wherein, a fifth static process is also included between step S6 and step S7.

[0020] Further, step S7 includes repeating the floating charge process in step S3 once or twice.

[0021] Furthermore, the fifth standing time is 0.1 to 1 h.

[0022] Furthermore, between step S1 and step S2, the temperature of the lithium-ion battery to be formed is raised to a preset temperature within 180 to 300 minutes.

[0023] Furthermore, the preset temperature is 80-90°C.

[0024] Furthermore, the time for the first standing, the second standing and the third standing is independently 10 to 30 minutes.

[0025] In order to achieve the above-mentioned object, another aspect of the present invention further provides a lithium-ion battery, which is formed by the above-mentioned formation method provided in the present application.

[0026] Applying the technical solution of the present invention, in the formation method of the lithium ion battery provided by the present application, step S2 adopts the first multiple rate to perform constant current charging to the first voltage, which can preliminarily activate the active material inside the lithium ion battery, and can make lithium ions uniformly deposited on the surface of the negative electrode material, while creating conditions for the subsequent active material and lithium ions to react more deeply. Step S3 performs floating charge on the lithium ion battery to be formed after the constant current charging is completed under the conditions of the first voltage and the second multiple rate, and by extending the floating charge time, the infiltration effect of the electrolyte and the positive electrode active material and the negative electrode active material is improved, and the active material and lithium ions are more evenly deposited on the surface of the negative electrode material, thereby improving the capacity of the lithium ion battery, and improving its cycle stability and safety performance. The constant current discharge process of step S4 can make lithium ions deintercalate from the negative electrode material back to the positive electrode material, which is conducive to further activating the active material inside the lithium ion battery, and at the same time, reducing the voltage from the first voltage to the second voltage can eliminate the unstable components generated in the above-mentioned charging process (steps S2 and S3), thereby further improving the stability of the lithium ion battery. Step S5 performs constant voltage discharge at the second voltage, and limits the constant voltage discharge time to the above-mentioned range of the present application, which can further activate the active substances inside the lithium-ion battery and inhibit the capacity reduction of the lithium-ion battery due to long-term low-voltage discharge. At the same time, the constant voltage discharge process can also improve the utilization efficiency of the lithium-ion battery, so that it maintains a stable output during the discharge process, thereby improving the electrochemical performance and stability of the lithium-ion battery and extending its service life.

[0027] The present application also arranges a plurality of static processes between step S2 and step S5. The arrangement of the static process can timely discharge the gas produced in the formation process, enable the internal structure and materials of the lithium-ion battery to be fully adapted and adjusted, and inhibit structural damage inside the lithium-ion battery caused by rapid charging or discharging processes, thereby improving the formation effect and enhancing the capacity and cycle stability of the lithium-ion battery.

[0028] In summary, the formation method of the lithium-ion battery provided in the present application can fully activate the active substances inside the lithium-ion battery, thereby improving the capacity and cycle stability of the lithium-ion battery, while also shortening the formation time, improving the formation efficiency, reducing energy consumption, and reducing production costs. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0030] As described in the background art, the existing formation method has the problem of insufficient reaction between active materials and lithium ions, which results in limited capacity of lithium-ion batteries and low efficiency and high energy consumption of the existing formation method. In order to solve the above technical problems, the first aspect of the present application provides a formation method of a lithium ion battery, which includes: step S1, injecting an electrolyte into a lithium ion battery to obtain a lithium ion battery to be formed; step S2, using a first rate to perform constant current charging on the lithium ion battery to be formed to a first voltage; step S3, using the first voltage and the second rate to float charge the lithium ion battery to be formed that has completed constant current charging, and the floating charge time is ≥2h; step S4, using a third rate to perform constant current discharge on the lithium ion battery to be formed that has completed float charging to a second voltage; wherein the second voltage is lower than the first voltage; step S5, using the second voltage to perform constant voltage discharge on the lithium ion battery to be formed that has completed constant current discharge to not less than 85% of the designed rated capacity, and the constant voltage discharge time is ≥2h; a first static process is also included between step S2 and step S3, a second static process is also included between step S3 and step S4, and a third static process is also included between step S4 and step S5.

[0031] In the formation method of the lithium-ion battery provided by the present application, step S2 adopts the first multiple rate to carry out constant current charging to the first voltage, which can preliminarily activate the active material inside the lithium-ion battery, and can make lithium ions deposit evenly on the surface of the negative electrode material, while creating conditions for the subsequent active material and lithium ions to react more deeply. Step S3 floats the lithium-ion battery to be formed after the constant current charging is completed under the conditions of the first voltage and the second multiple rate, and by extending the float charging time, the infiltration effect of the electrolyte and the positive electrode active material and the negative electrode active material is improved, and the active material and lithium ions are more evenly deposited on the surface of the negative electrode material, thereby improving the capacity of the lithium-ion battery, and improving its cycle stability and safety performance. The constant current discharge process of step S4 can make lithium ions deintercalate from the negative electrode material back to the positive electrode material, which is conducive to further activating the active material inside the lithium-ion battery, and at the same time, reducing the voltage from the first voltage to the second voltage can eliminate the unstable components generated in the above-mentioned charging process (steps S2 and S3), thereby further improving the stability of the lithium-ion battery. Step S5 performs constant voltage discharge at the second voltage, and limits the constant voltage discharge time to the above-mentioned range of the present application, which can further activate the active substances inside the lithium-ion battery and inhibit the capacity reduction of the lithium-ion battery due to long-term low-voltage discharge. At the same time, the constant voltage discharge process can also improve the utilization efficiency of the lithium-ion battery, so that it maintains a stable output during the discharge process, thereby improving the electrochemical performance and stability of the lithium-ion battery and extending its service life.

[0032] The present application also arranges a plurality of static processes between step S2 and step S5. The arrangement of the static process can timely discharge the gas produced in the formation process, enable the internal structure and materials of the lithium-ion battery to be fully adapted and adjusted, and inhibit structural damage inside the lithium-ion battery caused by rapid charging or discharging processes, thereby improving the formation effect and enhancing the capacity and cycle stability of the lithium-ion battery.

[0033] In summary, the formation method of the lithium-ion battery provided in the present application can fully activate the active substances inside the lithium-ion battery, thereby improving the capacity and cycle stability of the lithium-ion battery, while also shortening the formation time, improving the formation efficiency, reducing energy consumption, and reducing production costs.

[0034] In a preferred embodiment, the floating charge time is 2 to 10 hours, preferably 3 to 9 hours, 5 to 8 hours, or 7 to 8 hours. The floating charge time includes but is not limited to the above range. Limiting it to the above range is beneficial to improving the wetting effect of the electrolyte with the positive electrode active material and the negative electrode active material, and is beneficial to making the active material react with lithium ions more fully. At the same time, it is also beneficial to make lithium ions more uniformly deposited on the surface of the negative electrode material, thereby improving the capacity of the lithium ion battery and improving its cycle stability and safety performance. Specifically, the floating charge time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0035] In a preferred embodiment, the formation method further includes: step S6, using a fourth rate to perform at least one constant current charge and discharge cycle on the lithium ion battery to be formed that has completed constant voltage discharge, wherein the voltage interval of the constant current charge and discharge cycle is between the first voltage and the second voltage; and a fourth static process is also included between step S5 and step S6. Compared with other methods, setting the fourth static process after the constant voltage discharge in step S5 is conducive to fully adapting and adjusting the internal structure and materials of the lithium ion battery, and is also conducive to timely discharging the gas generated during the constant voltage discharge process, which is conducive to preparing for step S6. After the fourth static process, the fourth rate is used to perform a constant current charge and discharge cycle between the first voltage and the second voltage, which is conducive to further optimizing the lithium ion transmission path, thereby facilitating further activation of the active substances inside the lithium ion battery, and further facilitating improvement of the capacity and cycle stability of the lithium ion battery.

[0036] In order to further adapt and adjust the internal structure and materials of the lithium-ion battery more fully, and to further discharge the gas generated during the constant voltage discharge process, and to further prepare for step S6, preferably, the fourth resting time is 10 to 30 minutes.

[0037] In a preferred embodiment, the floating charge time is 5 to 8 hours, and the number of constant current charge and discharge cycles in step S6 is ≤ 3 cycles, preferably 1 or 2 cycles. Compared with other methods, appropriately extending the floating charge time is conducive to reducing the number of constant current charge and discharge cycles in step S6, which is conducive to shortening the formation time and improving the formation efficiency on the one hand, and is also conducive to reducing energy consumption and reducing production costs on the other hand.

[0038] In a preferred embodiment, the positive electrode material in the lithium ion battery to be formed includes but is not limited to one or more of the group consisting of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide and lithium iron phosphate, and the negative electrode material is a lithium titanate negative electrode material. Compared with other types of positive electrode materials and negative electrode materials, the above-mentioned formation method provided in the present application is more suitable for lithium ion batteries composed of the above-mentioned materials.

[0039] In a preferred embodiment, in step S2, the first rate is 0.15-1C, preferably 0.15-0.8C, 0.2-0.6C, or 0.3-0.5C. The first rate includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the efficiency of the constant current charging process, improving the formation efficiency, gradually activating the active substances inside the lithium-ion battery at the initial stage of formation, and making the lithium ions deposit more evenly on the surface of the negative electrode material, thereby helping to improve the capacity and cycle stability of the lithium-ion battery. Specifically, the first rate can be 0.15C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C or 1C.

[0040] In order to further improve the efficiency of the constant current charging process, further activate the active materials inside the lithium-ion battery, further make the lithium ions deposit more evenly on the surface of the negative electrode material, and further improve the formation efficiency, preferably, the first rate is 0.15-0.3C.

[0041] In a preferred embodiment, the first voltage is ≥ 2.7 V. Compared with other ranges, limiting the first voltage within the above range is conducive to fully activating the active material inside the lithium ion battery, and is conducive to improving the infiltration effect of the electrolyte and the electrode material, thereby facilitating the improvement of the electrochemical reaction efficiency of the lithium ion battery, and further facilitating the improvement of the capacity and cycle stability of the lithium ion battery.

[0042] In order to suppress overcharging and further activate the active materials inside the lithium ion battery to further improve the formation efficiency, preferably, the first voltage is 2.7 to 3.0 V, more preferably 2.8 to 3.0 V. Specifically, the first voltage may be 2.7 V, 2.8 V, 2.9 V or 3.0 V.

[0043] In a preferred embodiment, in step S3, the second rate is 0.1 to 1C, preferably 0.3 to 1C. The second rate includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the efficiency of floating charge, improving the infiltration effect of electrolyte and electrode active materials, promoting a deeper reaction between active substances and lithium ions, and making lithium ions more evenly deposited on the surface of negative electrode materials, thereby improving the capacity and cycle stability of lithium-ion batteries. Specifically, the second rate can be 0.1C, 0.15C, 0.2C, 0.3C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C or 1C.

[0044] In order to further improve the efficiency of floating charge, further promote the deeper reaction between active materials and lithium ions, and thus further improve the capacity and cycle stability of lithium-ion batteries, preferably, the second rate is 0.5-1C.

[0045] In a preferred embodiment, in step S4, the third rate is 0.15-1C, preferably 0.15-0.8C, 0.2-0.6C, or 0.3-0.5C. The third rate includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the efficiency of constant current discharge, and is beneficial to making lithium ions more fully deintercalate from the negative electrode material back into the positive electrode material, which is beneficial to further activate the active substances inside the lithium ion battery. At the same time, it is also beneficial to inhibit the occurrence of local overheating and side reactions caused by excessive discharge, thereby improving the capacity and cycle stability of the lithium ion battery. Specifically, the third rate can be 0.15C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C or 1C.

[0046] In a preferred embodiment, the second voltage is ≤1.8 V. Compared with other ranges, limiting the second voltage within the above range is conducive to suppressing over-discharge, eliminating unstable components generated in the above charging process (step S2 and step S3), and reducing the loss of electrolyte and reducing the accumulation of gas generated in the formation process inside the lithium ion battery, thereby improving the capacity and cycle stability of the lithium ion battery.

[0047] In order to further suppress over-discharge, further reduce the loss of electrolyte and the accumulation of gas inside the lithium-ion battery, thereby further improving the capacity and cycle stability of the lithium-ion battery, preferably, the second voltage is 1.5 to 1.8 V, more preferably 1.5 to 1.6 V. Specifically, the second voltage can be 1.5 V, 1.6 V, 1.7 V or 1.8 V.

[0048] In a preferred embodiment, in step S5, the lithium-ion battery to be formed that has completed constant current discharge is subjected to constant voltage discharge to 85-100% of the designed rated capacity, and the constant voltage discharge time is 2-5 hours. Compared with other ranges, limiting the constant voltage discharge time and the designed rated capacity corresponding to the constant voltage discharge process to the above range is conducive to more accurate control of the constant voltage discharge process, further activating the active substances inside the lithium-ion battery, and inhibiting the capacity reduction of the lithium-ion battery due to long-term low-voltage discharge. At the same time, it is also conducive to improving the use efficiency of the lithium-ion battery, so that it maintains a stable output during the discharge process, thereby further improving the capacity and cycle stability of the lithium-ion battery and extending its service life.

[0049] In a preferred embodiment, in step S6, the fourth rate is 0.15-1C, preferably 0.15-0.8C, 0.2-0.6C, or 0.3-0.5C. Compared with other ranges, limiting the fourth rate within the above range is beneficial to improving the efficiency and stability of the constant current charge and discharge cycle process, thereby further optimizing the electrochemical path inside the lithium-ion battery, further activating the active substances inside the lithium-ion battery, and further improving the capacity and cycle stability of the lithium-ion battery. Specifically, the fourth rate can be 0.15C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C or 1C.

[0050] In a preferred embodiment, the first standing time is 10 to 30 minutes, preferably 10 to 20 minutes or 10 to 15 minutes. The first standing time includes but is not limited to the above range, and limiting it within the above range is conducive to suppressing the transition charging during the constant current charging process, and is conducive to preparing for the floating charge of step S3, and is also conducive to timely discharging the gas generated during the constant current charging process, thereby improving the formation efficiency and increasing the formation efficiency.

[0051] In a preferred embodiment, the second standing time is 10 to 30 minutes, preferably 10 to 20 minutes or 10 to 15 minutes. The second standing time includes but is not limited to the above range, and limiting it within the above range is conducive to suppressing the occurrence of transitional charging during the floating charge process, and is conducive to preparing for the constant current discharge of step S4, and is also conducive to timely discharge of the gas generated during the floating charge process, thereby helping to improve the formation efficiency and increase the formation efficiency.

[0052] In a preferred embodiment, the third standing time is 10 to 30 minutes, preferably 10 to 20 minutes or 10 to 15 minutes. The third standing time includes but is not limited to the above range, and limiting it within the above range is conducive to suppressing the transition discharge during the constant current discharge process, and is conducive to preparing for the constant voltage discharge of step S5, and is also conducive to timely discharge of the gas generated during the constant current discharge process, thereby improving the formation efficiency and increasing the formation efficiency.

[0053] In a preferred embodiment, the formation method further includes: step S7, repeating the floating charge process in step S3 at least once; wherein, a fifth resting process is further included between step S6 and step S7. Compared with other methods, the fifth resting process is provided after the constant current charge and discharge cycle of step S6, which is conducive to fully adapting and adjusting the internal structure and materials of the lithium-ion battery, and is also conducive to timely discharging the gas generated during the constant current charge and discharge cycle, which is conducive to preparing for step S7. Performing step S7 after the fifth resting process is conducive to making the active material react with lithium ions more fully, thereby activating more active materials, and further conducive to improving the capacity and cycle stability of the lithium-ion battery.

[0054] In order to further enable the active material to react more fully with lithium ions and further activate more active materials, thereby further improving the capacity and cycle stability of the lithium-ion battery, preferably, step S7 includes repeating the floating charge process in step S3 once or twice.

[0055] In order to make the internal structure and materials of the lithium-ion battery more fully adaptable and adjustable, and to further discharge the gas generated during the constant current charge and discharge cycle, so as to facilitate the subsequent step S7, preferably, the fifth resting time is 10 to 30 minutes.

[0056] In a preferred embodiment, between step S1 and step S2, the lithium ion battery to be formed is also heated to a preset temperature within 180 to 300 minutes. Compared with other methods, the above method is beneficial to keep the lithium ion battery in a relatively constant temperature environment during the formation process, and is also beneficial to improve the wetting effect of the electrolyte and the electrode active material, thereby improving the subsequent formation effect, and further improving the electrochemical performance and cycle stability of the lithium ion battery. Preferably, the time for heating to the preset temperature is 180 to 280 minutes, 200 to 250 minutes, or 210 to 230 minutes. In order to further keep the lithium ion battery in a relatively constant temperature environment, further improve the wetting effect of the electrolyte and the electrode active material, and further improve the subsequent formation effect, preferably, the preset temperature is 80 to 90°C. Preferably, the preset temperature can be 82 to 90°C, 83 to 88°C, or 85 to 87°C, for example, it can be 82°C, 84°C, 86°C, 88°C or 90°C.

[0057] In order to further improve the formation effect, further activate more active substances, and thus further improve the capacity and cycle stability of the lithium-ion battery, preferably, the process from step S2 to step S7 is performed at a preset temperature.

[0058] The second aspect of the present application also provides a lithium-ion battery, which is formed using the above-mentioned formation method provided in the present application.

[0059] The formation method of the lithium-ion battery provided in the present application can fully activate the active substances inside the lithium-ion battery, thereby improving the capacity and cycle stability of the lithium-ion battery, and can also shorten the formation time, improve the formation efficiency, reduce energy consumption, and reduce production costs.

[0060] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0061] Example 1

[0062] A formation method for a lithium ion battery comprises the following steps:

[0063] (1) injecting 1 mol / L lithium hexafluorophosphate electrolyte (solvent is DEC+EC+EMC, volume ratio is 1:1:1) into a soft-pack lithium ion battery of model LTO3488105 to obtain a lithium ion battery to be formed, wherein the positive electrode material of the lithium ion battery to be formed is lithium nickel cobalt manganese oxide (NCM523), the negative electrode material is lithium titanate, and the diaphragm prepared by a wet process has a thickness of 12 μm;

[0064] (2) placing the lithium-ion battery to be formed in a formation device and heating it to 90° C. within 180 min, and all subsequent steps are carried out at this temperature;

[0065] (3) charging the lithium-ion battery to be formed at a constant current of 0.15C to 2.9V, and then leaving it to stand for 10 minutes;

[0066] (4) floating charge the above-mentioned lithium-ion battery to be formed at a constant voltage of 2.9V and a constant current of 1C for 2 hours; then let it stand for 10 minutes;

[0067] (5) discharging the floating-charged lithium-ion battery to be formed at a constant current of 1C to 1.5V, and then leaving it to stand for 10 minutes;

[0068] (6) performing constant voltage discharge on the lithium-ion battery to be formed after completing constant current discharge at a constant voltage of 1.5 V for 2 h, followed by standing for 10 min;

[0069] (7) performing one cycle of constant current charge and discharge at a constant current of 1 C in the voltage range of 1.5 V to 2.9 V on the lithium-ion battery to be formed that has completed constant voltage discharge, and then allowing it to stand for 10 minutes;

[0070] (8) Repeat step (4) twice to complete the formation.

[0071] Example 2

[0072] The difference from Example 1 is that the floating charge time in step (4) is 5 hours, and 2 constant current charge and discharge cycles are performed in step (7), and the remaining steps are the same as Example 1.

[0073] Example 3

[0074] The difference from Example 1 is that the floating charge time in step (4) is 10 hours, and the constant current charge and discharge cycle in step (7) is not performed. The remaining steps are the same as in Example 1.

[0075] Example 4

[0076] The difference from Example 1 is that the floating charge time in step (4) is 15 hours, and one constant current charge and discharge cycle is performed in step (7), and the remaining steps are the same as Example 1.

[0077] Example 5

[0078] The difference from Example 1 is that in step (3), the battery is charged to 2.9 V at a constant current of 1 C, and the remaining steps are the same as those in Example 1.

[0079] Example 6

[0080] The difference from Example 1 is that in step (3), the battery is charged to 2.9 V at a constant current of 0.1 C, and the remaining steps are the same as those in Example 1.

[0081] Example 7

[0082] The difference from Example 1 is that in step (3), the battery is charged to 2.6 V at a constant current of 0.15 C, and the remaining steps are the same as those in Example 1.

[0083] Example 8

[0084] The difference from Example 1 is that in step (5), the battery is discharged to 1.5 V at a constant current of 0.15 C, and the remaining steps are the same as those in Example 1.

[0085] Example 9

[0086] The difference from Example 1 is that in step (5), the battery is discharged to 1.8V at a constant current of 1C, and the remaining steps are the same as those in Example 1.

[0087] Example 10

[0088] The difference from Example 1 is that in step (5), the battery is discharged to 1.5V at a constant current of 1.5C, and the remaining steps are the same as those in Example 1.

[0089] Embodiment 11

[0090] The difference from Example 1 is that the constant voltage discharge time in step (6) is 5 hours, and the remaining steps are the same as Example 1.

[0091] Example 12

[0092] The difference from Example 1 is that the constant voltage discharge time in step (6) is 7 hours, and the remaining steps are the same as Example 1.

[0093] Embodiment 13

[0094] The difference from Example 1 is that the temperature in the formation equipment is 80° C., and the remaining steps are the same as Example 1.

[0095] Embodiment 14

[0096] The difference from Example 1 is that the temperature in the formation equipment is 70° C., and the remaining steps are the same as Example 1.

[0097] Embodiment 15

[0098] The difference from Example 1 is that step (8) is omitted, and after one constant current charge and discharge cycle in step (7) is completed, the formation is terminated, and the remaining steps are the same as those in Example 1.

[0099] Comparative Example 1

[0100] The difference from Example 1 is that step (4) and step (8) are omitted, floating charge is not performed during the formation process, and the remaining steps are the same as those in Example 1.

[0101] Comparative Example 2

[0102] The difference from Example 1 is that steps (4) and (8) are omitted, floating charge is not performed during the formation process, and in step (7), the lithium ion battery to be formed that has completed constant voltage discharge is subjected to two constant current charge and discharge cycles, and the remaining steps are the same as in Example 1.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that steps (4) and (8) are omitted, floating charge is not performed during the formation process, and in step (7), the lithium ion battery to be formed that has completed constant voltage discharge is subjected to three constant current charge and discharge cycles, and the remaining steps are the same as in Example 1.

[0105] Comparative Example 4

[0106] The difference from Example 1 is that the floating charge time in step (4) and step (8) is 0.5 h, and the remaining steps are the same as in Example 1.

[0107] Comparative Example 5

[0108] The difference from Example 1 is that the constant voltage discharge time in step (6) is 1 hour, and the remaining steps are the same as Example 1.

[0109] The gas production, first effect and average discharge voltage of the to-be-formed lithium-ion batteries in all the embodiments and comparative examples of the present application were tested during the formation process. The capacity of the lithium-ion batteries after formation in all the embodiments and comparative examples of the present application was tested by volume separation.

[0110] Among them, (1) the test method of gas production is: using the isobaric method to test, keeping the internal and external voltages of the soft-pack lithium-ion battery consistent, and testing the change in volume of the soft-pack lithium-ion battery, and the change in volume is the gas production;

[0111] (2) The test method for the first effect is: the first effect in the formation process refers to the first charge and discharge process of the lithium-ion battery to be formed, that is, the ratio of the discharge capacity to the pre-charge capacity in the process from step (3) to step (6) in the embodiment of the present application;

[0112] (3) The test method for the average discharge voltage is as follows: the voltage values ​​at each test time point (data collected every 10 seconds) during the discharge process of the lithium-ion battery to be formed, i.e., during steps (5) and (6) in the embodiment of the present application, are added and divided by the number of test time points to obtain the average discharge voltage;

[0113] (4) The test method for the capacity is as follows: at 25°C, charge the battery to 2.9V at a constant current of 1C on a charge and discharge cabinet, let it stand for 10 minutes, and then discharge it to 1.5V at a constant current of 1C. The capacity of the lithium-ion battery during the constant current discharge process is recorded.

[0114] The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] It should be noted that the active substances in the positive electrode material and the negative electrode material will undergo electrochemical reactions to generate gas during the charging and discharging process of the lithium titanate battery. 3+ Transformed into Ti 4+ , releasing an electron, thereby affecting the oxidation reaction and decomposition reaction of the electrolyte; at the same time, the electrolyte will also produce gases such as H2, CO2 and CO when side reactions occur with the surface of the positive electrode material and the negative electrode material. When the active substances are more fully activated during the formation process, their side reactions will also increase, and the amount of gas released will also increase. If the gas is released as much as possible during the formation process, the gas production of the battery will be reduced during subsequent use, which is beneficial to improve the capacity, cycle stability and safety performance of lithium-ion batteries and extend their service life. Therefore, the more fully the active substances inside the lithium-ion battery are activated, the more gas is produced during its formation process.

[0119] A high first efficiency during the formation process means less irreversible lithium loss in the cathode film and a high recoverable capacity. However, the higher the first efficiency, the better. Too high a first efficiency (≥90%) will cause the performance of lithium-ion batteries to decline during subsequent cycles. The average discharge voltage can reflect the stability of lithium-ion batteries during continuous discharge and the efficiency of the electrochemical reaction inside the battery. The higher the average discharge voltage, the more stable and durable the lithium-ion battery can provide during the discharge process.

[0120] The above-mentioned embodiments of the present invention achieve the following technical effects:

[0121] By comparing Example 1 and Comparative Examples 1 to 3, it can be seen that using the first voltage and the second rate to float charge the lithium-ion battery to be formed after constant current charging can improve the wetting effect of the electrolyte with the positive electrode active material and the negative electrode active material, promote a deeper reaction between the active substance and the lithium ion, and is beneficial to fully activate the active substance inside the lithium-ion battery, thereby improving the capacity of the lithium-ion battery.

[0122] By comparing Examples 1 to 4 and Comparative Example 4, it can be seen that, compared with other ranges, limiting the floating charge time within the above-mentioned range of the present application is beneficial to improving the wetting effect of the electrolyte with the positive electrode active material and the negative electrode active material, and is beneficial to making the active substance react with lithium ions more fully, and is beneficial to fully activating the active substance inside the lithium ion battery, thereby helping to improve the capacity of the lithium ion battery.

[0123] By comparing Examples 1, 11 and 12 and Comparative Example 5, it can be seen that, compared with other ranges, limiting the constant-voltage discharge time within the above-mentioned range of the present application is conducive to more precise control of the constant-voltage discharge process, is conducive to further activating the active substances inside the lithium-ion battery, is conducive to inhibiting the capacity reduction of the lithium-ion battery due to long-term low-voltage discharge, and is also conducive to improving the use efficiency of the lithium-ion battery, so that it maintains a stable output during the discharge process, thereby further improving the capacity of the lithium-ion battery.

[0124] By comparing Examples 1, 5 to 7, it can be seen that, compared with other ranges, limiting the first rate and the first voltage in the constant current charging process to the above-mentioned range of the present application is beneficial to improving the efficiency of the constant current charging process, improving the formation efficiency, gradually activating the active substances inside the lithium-ion battery in the early stage of formation, and making the lithium ions deposited more evenly on the surface of the negative electrode material, thereby helping to improve the capacity of the lithium-ion battery.

[0125] By comparing Examples 1, 8 to 10, it can be seen that, compared with other ranges, limiting the third rate and the second voltage in the constant current discharge process within the above-mentioned range of the present application is beneficial to improving the efficiency of the constant current discharge process, and is beneficial to making the lithium ions more fully deintercalated from the negative electrode material back into the positive electrode material, which is beneficial to further activating the active substances inside the lithium-ion battery, and is also beneficial to inhibiting the occurrence of local overheating and side reactions caused by excessive discharge, thereby helping to improve the capacity of the lithium-ion battery.

[0126] By comparing Examples 1, 13 and 14, it can be seen that, compared with other ranges, limiting the temperature in the formation process within the above-mentioned range of the present application is beneficial to improving the wetting effect of the electrolyte and the electrode active material, which is beneficial to improving the subsequent formation effect, and further beneficial to improving the electrochemical performance of the lithium-ion battery.

[0127] Comparing Examples 1 and 15, it can be seen that repeating the floating charge at least once is beneficial to making the active material react with lithium ions more fully, thereby activating more active materials, and further facilitating improving the capacity of the lithium-ion battery.

[0128] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A formation method for a lithium ion battery, characterized in that: The formation method comprises: Step S1, injecting an electrolyte into a lithium-ion battery to obtain a lithium-ion battery to be formed; Step S2, charging the lithium-ion battery to be formed at a first rate with a constant current to a first voltage; Step S3, using the first voltage and the second rate to float charge the lithium-ion battery to be formed after the constant current charging, and the floating charge time is ≥ 2h; Step S4, using a third rate to perform constant current discharge on the lithium-ion battery to be formed after the floating charge to a second voltage; wherein the second voltage is lower than the first voltage; Step S5, using a second voltage to perform constant voltage discharge on the lithium ion battery to be formed after the constant current discharge to a value not less than 85% of the designed rated capacity, and the constant voltage discharge time is ≥ 2h; A first static process is included between step S2 and step S3, a second static process is included between step S3 and step S4, and a third static process is included between step S4 and step S5.

2. The formation method of a lithium ion battery according to claim 1, characterized in that: The floating charge time is 2 to 10 hours; Preferably, the formation method further comprises: step S6, performing at least one constant current charge-discharge cycle on the lithium ion battery to be formed after the constant voltage discharge at a fourth rate, wherein the voltage interval of the constant current charge-discharge cycle is between the first voltage and the second voltage; a fourth resting process is further included between step S5 and step S6; preferably, the fourth resting time is 10 to 30 minutes; More preferably, the floating charge time is 5 to 8 hours, and the number of constant current charge and discharge cycles in step S6 is ≤ 3 cycles, preferably 1 or 2 cycles; More preferably, in step S6, the fourth magnification is 0.15-1C.

3. The formation method of a lithium ion battery according to claim 1, characterized in that: In the step S5, the lithium-ion battery to be formed that has completed the constant current discharge is subjected to the constant voltage discharge to 85-100% of the designed rated capacity, and the constant voltage discharge time is 2-5 hours.

4. The lithium ion battery formation method according to any one of claims 1 to 3, characterized in that: The positive electrode material in the lithium-ion battery to be formed is selected from one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide and lithium iron phosphate, and the negative electrode material is lithium titanate negative electrode material.

5. The lithium ion battery formation method according to claim 4, characterized in that: In the step S2, the first magnification is 0.15 to 1C; and / or, The first voltage is ≥2.7V, preferably 2.7-3.0V; and / or, In the step S3, the second magnification is 0.1-1C.

6. The lithium ion battery formation method according to claim 5, characterized in that: In the step S4, the third magnification is 0.15 to 1C; and / or, The second voltage is ≤1.8V, preferably 1.5-1.8V.

7. The lithium ion battery formation method according to claim 2, characterized in that: The formation method further comprises: step S7, repeating the floating charge process in step S3 at least once; wherein a fifth static process is further comprised between step S6 and step S7; Preferably, the step S7 includes repeating the floating charge process in the step S3 once or twice; Preferably, the fifth standing time is 0.1 to 1 hour.

8. The lithium ion battery formation method according to any one of claims 1 to 7, characterized in that: The step between step S1 and step S2 also includes heating the lithium-ion battery to be formed to a preset temperature within 180 to 300 minutes; Preferably, the preset temperature is 80-90°C.

9. The lithium ion battery formation method according to claim 1, characterized in that: The time for the first standing, the second standing and the third standing are each independently 10 to 30 minutes.

10. A lithium ion battery, characterized in that: The lithium-ion battery is formed by the formation method according to any one of claims 1 to 9.

Images