Lithium ion battery inactivation lithium activation method and application thereof

Abstract

The invention relates to the technical field of batteries, and discloses a lithium ion battery inactivation lithium activation method and application thereof. The method comprises the following steps: (1) carrying out constant-current discharge I treatment on a lithium ion battery to obtain an intermediate I; (2) carrying out constant-current discharge II treatment on the intermediate I to lower limit cut-off voltage to obtain an intermediate II; and (3) carrying out standing treatment on the intermediate II to obtain the activated lithium ion battery, the current of the constant-current discharge I processing is at least 0.8 C higher than that of the constant-current discharge II processing; the time of the constant-current discharge I treatment is 1-3 minutes; the current of the constant-current discharge I treatment is 1.1 C to 3C; and the current of the constant-current discharge II treatment is 0.05 C to 0.33 C. The method provided by the invention has the advantages of effectively enhancing the charge-discharge efficiency of the battery, improving the energy density of the battery, reducing the thermal runaway risk, prolonging the cycle life of the battery and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a method for activating inactivated lithium in a lithium-ion battery and its application. Background Art

[0002] Lithium-ion batteries mainly use carbon materials as the negative electrode material and lithium-containing compounds as the positive electrode material. With the rapid development of lithium-ion battery technology, lithium-ion batteries as power sources have been widely studied by technicians.

[0003] Currently, the demands in industries such as electric vehicles and consumer electronics are continuously increasing, and the requirements for the high energy density and cycle life of lithium-ion batteries are also getting higher and higher. However, during the charging process of lithium-ion batteries, some lithium ions are deposited on the surface of the negative electrode in the form of lithium metal, and the remaining lithium ions are embedded in the negative electrode material. During the discharging process, the phenomena of ion extraction and partial stripping of the deposited lithium metal are likely to occur. During the stripping process of lithium metal, some inactivated lithium is formed, and the reaction of this inactivated lithium with the electrolyte is the main cause of the capacity loss and shortened cycle life of lithium-ion batteries. The existence of inactivated lithium reduces the concentration of migratable and diffusible lithium ions, and at the same time limits the diffusion of lithium ions in the negative electrode material. Accordingly, the lithium insertion current also gradually decreases, ultimately leading to the generation of lithium dendrites and local micro-short circuits and thermal imbalances, quickly consuming the battery life. Therefore, for existing lithium-ion batteries, how to activate and reuse the generated inactivated lithium has very important research significance.

[0004] CN109216796A discloses a method for activating a lithium-ion battery, which includes the following steps: 1) discharging the lithium-ion battery to a cut-off voltage, and the cut-off voltage is 2.7 - 2.8V; 2) then continuing to over-discharge to an over-discharge cut-off voltage; 3) performing positive and negative alternating pulse current cycling near the over-discharge cut-off voltage for a lithium-ion battery discharged to the over-discharge cut-off voltage for several times, where the magnitudes of the positive pulse current and the negative pulse current are the same, and the pulse action times are the same. This method can activate a battery with capacity attenuation, making the capacity of the activated battery recover close to the original capacity and extending the cycle life of the battery. However, this method of performing multiple pulse impacts in the low voltage region is likely to cause irreversible damage to the battery capacity.

[0005] CN117766881A discloses a method for activating dead lithium in a secondary battery. The method includes the following steps: controlling the secondary battery to perform constant current discharge at a first current until the voltage of the secondary battery reaches the discharge cut-off voltage, where the first current is less than one times the rated current; controlling the secondary battery to perform constant voltage discharge according to the discharge cut-off voltage for a first set time; after reaching the first set time, controlling the secondary battery to perform constant current discharge at a second current lower than the first current until the voltage of the secondary battery reaches the voltage threshold at which a solid electrolyte film can be formed. This method can improve the recovery rate of dead lithium through three stages of discharge, with a short activation time, and at the same time takes into account the repair of the solid electrolyte film, which is more conducive to the recovery of battery capacity. However, the current used in the constant current discharge stage of this method is relatively too small, and it is difficult for the inactivated lithium far from the current collector to reconnect with the current collector to build an electron channel, resulting in incomplete recovery and activation of the inactivated lithium.

[0006] Therefore, it is of great significance to develop a new technology for activating inactivated lithium in lithium-ion batteries. Summary of the Invention

[0007] The object of the present invention is to overcome the problems in the prior art, such as the increased risk of over-discharge of lithium-ion batteries, the easy damage of battery capacity during the activation of inactivated lithium, low activation efficiency, and incomplete activation.

[0008] To achieve the above object, on the one hand, the present invention provides a method for activating inactivated lithium in a lithium-ion battery, the method comprising:

[0009] (1) Performing constant current discharge I treatment on the lithium-ion battery to obtain intermediate I;

[0010] (2) Performing constant current discharge II treatment on the intermediate I to the lower cut-off voltage to obtain intermediate II;

[0011] (3) Performing a standing treatment on the intermediate II to obtain an activated lithium-ion battery;

[0012] The current of the constant current discharge I treatment is at least 0.8C higher than the current of the constant current discharge II treatment; the time of the constant current discharge I treatment is 1 - 3 min; the current of the constant current discharge I treatment is 1.1C - 3C; the current of the constant current discharge II treatment is 0.05C - 0.33C.

[0013] On the second aspect, the present invention provides the application of the method described in the first aspect in the field of lithium-ion battery regeneration.

[0014] Through the above technical solutions, the present invention has at least the following beneficial technical effects:

[0015] (1) In the method for activating deactivated lithium in a lithium-ion battery provided by the present invention, a high current density can ensure that metallic lithium far from the current collector is converted into Li + , and a low current density promotes the uniform insertion of lithium ions into the graphite negative electrode, inhibits the generation of secondary dendrites, and effectively realizes the reversible effect of dead lithium.

[0016] (2) The standing step in the present invention can effectively promote the dissolution of deactivated lithium.

[0017] (3) The method for activating deactivated lithium in a lithium-ion battery provided by the present invention can effectively enhance the charge-discharge efficiency of the battery, improve the energy density of the battery, reduce the risk of thermal runaway, and extend the cycle life of the battery. Detailed implementation manners

[0018] In the ranges disclosed herein, the endpoints and any values are not limited to the exact 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, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0019] As described above, the first aspect of the present invention provides a method for activating deactivated lithium in a lithium-ion battery, and the method includes:

[0020] (1) Performing a constant current discharge I treatment on the lithium-ion battery to obtain intermediate I;

[0021] (2) Performing a constant current discharge II treatment on the intermediate I to a lower cut-off voltage to obtain intermediate II;

[0022] (3) Performing a standing treatment on the intermediate II to obtain an activated lithium-ion battery;

[0023] The current of the constant current discharge I treatment is at least 0.8C higher than the current of the constant current discharge II treatment; the time of the constant current discharge I treatment is 1 - 3 min; the current of the constant current discharge I treatment is 1.1C - 3C; the current of the constant current discharge II treatment is 0.05C - 0.33C.

[0024] Preferably, the current of the constant current discharge I treatment is 1.5C - 2.5C. The inventors of the present invention have found that in this preferred case, the method for activating deactivated lithium in a lithium-ion battery provided by the present invention enables the lithium-ion battery to have a lower risk of thermal runaway and a better cycle life.

[0025] Further preferably, the time of the constant current discharge I treatment is 1.5 - 2.5 min.

[0026] More preferably, the current of the constant current discharge II treatment is 0.15C - 0.25C.

[0027] Preferably, the time of the standing treatment is 6 - 18h.

[0028] According to a preferred embodiment, the time of the standing treatment is 10 - 15h. The inventors of the present invention have found that in this preferred case, the method for activating inactivated lithium of the lithium-ion battery provided by the present invention can restore the battery capacity of the lithium-ion battery with higher efficiency.

[0029] When the lithium-ion battery is subjected to the standing treatment in the present invention, the battery is in a state of empty charge. In this state, inactivated lithium, especially the part far from the current collector, will dissolve and participate in the reaction again, thereby effectively improving the activation efficiency of inactivated lithium.

[0030] Preferably, the lower cut-off voltage is 2.0V - 2.5V.

[0031] In the present invention, the inactivated lithium is metallic lithium that has lost the conductive path by detaching from the electrode, and the capacity loss of the lithium-ion battery is 2 - 10%. The inventors of the present invention have found that in this preferred case, the method for activating inactivated lithium of the lithium-ion battery provided by the present invention has the optimal activation efficiency.

[0032] According to a preferred embodiment, the temperatures of the constant current discharge I treatment, the constant current discharge II treatment, and the standing treatment are each independently 20 - 28°C.

[0033] According to a more preferred embodiment, the temperature of the constant current discharge I treatment is 20 - 25°C, the temperature of the constant current discharge II treatment is 20 - 28°C, and the temperature of the standing treatment is 25 - 28°C.

[0034] Preferably, the negative electrode material of the lithium-ion battery is graphite, and the positive electrode material is selected from at least one of ternary materials, lithium iron phosphate, and lithium cobaltate; the ternary material is lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminate.

[0035] The present invention also includes operations of activation pre - cycling and lithium deposition preparation for lithium - ion batteries. Specifically, in the activation pre - cycling stage, a constant - current and constant - voltage charging method is adopted. The battery is charged to the upper cut - off voltage and then discharged at a constant current to the lower cut - off voltage. The above steps are cycled to activate the battery, and the last cycle is selected as the fixed - volume capacity. In the lithium deposition preparation stage, the battery after determining the volume is discharged to the cut - off voltage, and a constant - current charge is carried out with a current greater than the maximum charge rate that the battery can withstand, then a constant - voltage charge is carried out to the cut - off voltage, and then a constant - current discharge is carried out to the lower cut - off voltage, and the above steps are cycled. The battery after lithium deposition is charged and discharged in multiple cycles by using the same charge - discharge method as in the activation pre - cycling step, and the last cycle is used as the fixed - volume capacity of the battery after lithium deposition. In the activation stage, through high - rate discharge within a short time to activate the inactivated lithium and small - current discharge to continuously promote the electrochemical reaction and migration of lithium ions, the inactivated metallic lithium re - establishes a connection with the current collector, successfully converting the inactivated lithium into active lithium that can continue to participate in the electrochemical reaction, completing the activation process. The activated battery is charged and discharged in multiple cycles by using the same charge - discharge method as in the activation pre - cycling step, and the last cycle is used as the fixed - volume capacity of the activated battery.

[0036] As described above, the second aspect of the present invention provides an application of the method described in the first aspect in the field of lithium - ion battery regeneration.

[0037] The present invention will be described in detail below through examples. In the following examples, without special instructions, various instruments and raw materials used are ordinary commercially available products.

[0038] In the present invention, "99% SOC" represents that the charging state of the battery is 99%;

[0039] "1 / 3C charging" means that during the charging process of the battery, the current used is 1 / 3 times the rated capacity of the battery;

[0040] "1 / 3C discharge" means that the battery discharges at a current of 1 / 3 times the rated capacity of the battery.

[0041] Example 1

[0042] This example is used to provide a method for activating inactivated lithium in a lithium - ion battery, which specifically includes the following steps:

[0043] (1) Pre - cycle and determine the volume of the lithium - ion battery

[0044] ① Charge at 1 / 3C to a voltage of 3.65V;

[0045] ② Constant - voltage charge until the current is 0.05C;

[0046] ③ Discharge at 1 / 3C to a voltage of 2.5V and let it stand for 10 min;

[0047] ④ Repeat the operations of ①-③ above 10 times, and use the battery capacity of the last cycle as the fixed capacity of the battery after pre-cycle activation.

[0048] (2) Perform lithium deposition preparation and fixed capacity determination on the activated lithium-ion battery

[0049] ① Discharge at 1 / 3C until the voltage reaches 2.5V, and let it stand for 10 min;

[0050] ② Charge at 2.1C until 99% SOC (the upper cut-off voltage is 3.89V, and the protection voltage is 3.9V), and let it stand for 1 min;

[0051] ③ Charge at 0.2C until the voltage reaches 3.65V, and let it stand for 3 h;

[0052] ④ Discharge at 1 / 3C until the voltage reaches 2.5V, and let it stand for 10 min;

[0053] ⑤ Repeat the operations of ②-④ above 5 times.

[0054] Use the same operations of ①-③ in step (1) above, repeat the operations 3 times, and use the battery capacity of the last cycle as the fixed capacity of the battery after lithium deposition preparation.

[0055] (3) Activate and determine the fixed capacity of the lithium-ion battery after lithium deposition preparation

[0056] ① Charge at 1 / 3C until the voltage reaches 3.65V;

[0057] ② Constant voltage charge until the current reaches 0.05C, and let it stand for 10 min;

[0058] ③ Discharge at 2C for 2 min;

[0059] ④ Discharge at 0.2C until the voltage reaches 2.5V, and let it stand for 12 h.

[0060] Use the same operations of ①-③ in step (1) above, repeat the operations 3 times, and use the battery capacity of the last cycle as the fixed capacity of the battery after activating the inactivated lithium.

[0061] The results of the fixed capacity of the battery obtained in the above steps are shown in Table 1.

[0062] Example 2

[0063] This example uses a method similar to that of Example 1. The difference is that the operation ③ in step (3) is adjusted to: constant current discharge at 1.5C for 2.5 min; the operation ④ is adjusted to: constant current discharge at 0.15C until the voltage reaches 2.5V, and let it stand for 10 h. The rest of the operations and conditions are the same as those in Example 1.

[0064] Example 3

[0065] This embodiment uses a method similar to that of Embodiment 1. The difference is that operation ③ in step (3) is adjusted to: constant current discharge at 1.1C for 2 min. The remaining operations and conditions are the same as those in Embodiment 1.

[0066] Embodiment 4

[0067] This embodiment uses a method similar to that of Embodiment 1. The difference is that operation ③ in step (3) is adjusted to: constant current discharge at 3C for 2 min. The remaining operations and conditions are the same as those in Embodiment 1.

[0068] Embodiment 5

[0069] This embodiment uses a method similar to that of Embodiment 1. The difference is that operation ④ in step (3) is adjusted to: constant current discharge at 0.05C until the voltage reaches 2.5V, and then stand for 12 h. The remaining operations and conditions are the same as those in Embodiment 1.

[0070] Comparative Example 1

[0071] This comparative example uses a method similar to that of Embodiment 1. The difference is that operation ③ in step (3) is adjusted to: constant current discharge at 1C for 2 min. The remaining operations and conditions are the same as those in Embodiment 1.

[0072] Comparative Example 2

[0073] This comparative example uses a method similar to that of Embodiment 1. The difference is that operation ③ in step (3) is adjusted to: constant current discharge at 4C for 2 min. The remaining operations and conditions are the same as those in Embodiment 1.

[0074] Comparative Example 3

[0075] This comparative example uses a method similar to that of Embodiment 1. The difference is that operation ④ in step (3) is adjusted to: constant current discharge at 0.5C until the voltage reaches 2.5V, and then stand for 12 h. The remaining operations and conditions are the same as those in Embodiment 1.

[0076] Comparative Example 4

[0077] This comparative example uses a method similar to that of Embodiment 1. The difference is that operation ④ in step (3) is adjusted to: constant current discharge at 0.2C until the voltage reaches 2.5V, and then stand for 5 h. The remaining operations and conditions are the same as those in Embodiment 1.

[0078] Comparative Example 5

[0079] This comparative example uses a method similar to that of Embodiment 1. The difference is that step (3) is adjusted to:

[0080] ① Charge at 1 / 3C until the voltage reaches 3.65V;

[0081] ② Constant voltage charge until the current reaches 0.05C, and then stand for 10 min;

[0082] ③Constant current discharge at 2C for 2 min;

[0083] ④Constant voltage discharge at the voltage reached in ③ above for 30 min;

[0084] ⑤Constant current discharge at 0.2C until the voltage reaches 2.5V, and stand for 12 h.

[0085] All other operations and conditions are the same as in Example 1.

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from the results in Table 1 that the method for activating inactivated lithium of the lithium-ion battery provided by the present invention can more effectively restore the capacity of the lithium-ion battery. Through the synergistic effect of three stages of "short-time high-rate impact + long-time mild discharge + standing repair", the high current density can ensure that the metallic lithium far from the current collector can be converted into Li + , and the low current density promotes the uniform intercalation of lithium ions into the graphite negative electrode, inhibits the generation of secondary dendrites, effectively realizes the reversibility of inactivated lithium, and the standing process promotes the dissolution and restoration of activity of inactivated lithium. Secondly, the method uses simple equipment and has strong versatility, providing a theoretical basis for a low-cost and low-risk battery repair strategy, and is especially suitable for large-scale industrial scenarios of power battery cascade utilization.

[0090] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for activating inactivated lithium in a lithium-ion battery, characterized in that, The method includes: (1) Performing a constant current discharge I treatment on a lithium-ion battery to obtain intermediate I; (2) Performing a constant current discharge II treatment on the intermediate I to a lower cut-off voltage to obtain intermediate II; (3) Performing a static treatment on the intermediate II to obtain an activated lithium-ion battery; The current of the constant current discharge I treatment is at least 0.8C higher than the current of the constant current discharge II treatment; the time of the constant current discharge I treatment is 1 - 3 min; the current of the constant current discharge I treatment is 1.1C - 3C; the current of the constant current discharge II treatment is 0.05C - 0.33C.

2. The method according to claim 1, wherein, The current of the constant current discharge I treatment is 1.5C - 2.5C.

3. The method according to claim 1, wherein, The time of the constant current discharge I treatment is 1.5 - 2.5 min.

4. The method according to claim 1, wherein The current of the constant current discharge II treatment is 0.15C - 0.25C.

5. The method according to claim 1, wherein The time of the static treatment is 6 - 18 h.

6. The method according to any one of claims 1-5, wherein, The lower cut-off voltage is 2.0V - 2.5V.

7. According to the method according to any one of claims 1-5, wherein, The deactivated lithium is metallic lithium that has lost the conductive path by being detached from the electrode, and the capacity loss of the lithium-ion battery is 2 - 10%.

8. The method according to any one of claims 1-5, wherein The temperatures of the constant current discharge I treatment, the constant current discharge II treatment, and the static treatment are each independently 20 - 28°C.

9. The method according to any one of claims 1-5, wherein, The negative electrode material of the lithium-ion battery is graphite, and the positive electrode material is selected from at least one of ternary materials, lithium iron phosphate, and lithium cobaltate; the ternary material is lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminate.

10. Application of the method according to any one of claims 1 - 9 in the field of lithium-ion battery regeneration.

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