Lithium ion battery low-temperature electrolyte injection method

Abstract

The invention relates to a lithium ion battery low-temperature electrolyte injection method which comprises the following steps: S1, removing excessive moisture in a battery through heating and baking, then standing and preheating an electrolyte, and cooling the heated and baked battery; s2, putting the battery into a liquid injection device for vacuumizing, stopping vacuumizing and injecting liquid into the battery when the vacuum degree reaches a preset value, stopping liquid injection when the liquid injection amount is reached, maintaining the vacuum state, and then transporting and transferring into a standing box; s3, after vacuum wall breaking is conducted in the standing box, nitrogen positive pressure is input into the standing cavity, and circulation is conducted after the condition is kept for 60-240 s; s4, vacuumizing the standing box to-95 Kpa, stopping vacuumizing, keeping for 30-120 seconds, and then circulating; s5, the steps S3 and S4 are repeated for 3-10 times, then the vacuum and nitrogen cavity is subjected to pressure relief, a sealing rubber nail is inserted before the battery is transferred out, liquid injection is completed, and the next procedure is conducted; and S6, placing the battery after liquid injection in a high-temperature room, standing, infiltrating and performing related process aging, and conveying the battery to a negative-pressure formation process for formation.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage battery equipment, and more particularly to a method for injecting low-temperature electrolyte into a lithium-ion battery. Background Art

[0002] After lithium-ion batteries are assembled, they need to be filled. The electrolyte in lithium-ion batteries is a crucial component, responsible for ion transport within the battery, while also dissipating heat and protecting the battery. This process ensures the proper functioning of the chemical reactions within the battery and effectively prevents safety issues such as overheating, short circuits, and leakage.

[0003] The Chinese patent publication number CN109037579B discloses a constant pressure liquid injection device and liquid injection method for a square power battery, including a liquid injection device and a clamp. The clamp includes a clamp upper cover and a clamp lower cover. The clamp upper cover and the clamp lower cover are separate structures, and when closed, they are in a locked and sealed state and form a clamp inner cavity. The clamp inner cavity is used to fix the battery. The battery includes a battery liquid injection hole and a battery inner cavity. The liquid injection device is fixedly connected to the upper surface of the clamp. A reversing valve is also connected to the top of the liquid injection cup. One end of the reversing valve is connected to the air pipe joint. The device is alternately injected with positive and negative pressure by switching the reversing valve and connecting an external device through the air pipe joint. It is fast and safe, and the battery is not easily deformed.

[0004] However, the inventors have discovered that, during the actual injection process, the higher the battery's areal density, the more difficult it is to inject the liquid, and the longer the post-injection wetting time. This results in a longer production cycle and increased production costs. Currently, the post-injection wetting time for batteries is generally longer than 36 hours. Poor wetting can also lead to increased internal resistance, black spots, lithium precipitation, and other anomalies, posing safety concerns. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and provide a method for low-temperature electrolyte injection into a lithium-ion battery. The method utilizes an electrolyte low-temperature storage at 0-6°C to transfer the electrolyte to an electrolyte standing room. The workshop does not need to be placed in a standby state to heat the electrolyte to 20°C±3°C, thereby saving process time and preheating the electrolyte holding room. The electrolyte is then kept at a certain temperature before being injected into the battery. The battery injection is completed through a cyclic process, thereby improving the low-temperature electrolyte injection method while ensuring the injection effect and injection accuracy, shortening the battery manufacturing cycle, ensuring good infiltration of the battery electrode interface, better eliminating battery polarization, and enabling a better and more effective chemical reaction between the cathode and the anode, thereby effectively improving electrical performance and performance stability.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0008] S1. Remove excess water inside the battery by heating and baking, then place the electrolyte aside for preheating, and cool the heated and baked battery;

[0009] S2. Place the battery in a liquid injection device and evacuate the battery. When the vacuum reaches a predetermined value, stop evacuating the battery and inject liquid into the battery. When the injection volume is reached, stop injecting liquid and maintain the vacuum state for 30s-60s before transporting the battery to a static box.

[0010] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 60s-240s before circulation.

[0011] S4. Vacuum the static box to -90Kpa ～ -95Kpa, stop vacuuming and keep it for 30S-120S before circulating;

[0012] S5. Repeat steps S3 and S4 for 3-10 times, then release the pressure in the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection before proceeding to the next process;

[0013] S6: Place the battery after liquid injection in a high temperature room for static immersion and related process aging, and then the battery can be sent to the negative pressure formation process for formation.

[0014] As a preference, in S1, the baking is vertical contact baking, and the moisture content of the battery after baking is ≤200ppm.

[0015] As a preference, in S1, the electrolyte preheating temperature range is 17°C-23°C, and the battery temperature range after cooling is 40°C-50°C.

[0016] As a preferred embodiment, in S6, the temperature range of the high temperature room is 42° C.-48° C., and the static soaking time is 24 hours.

[0017] As a preferred embodiment, in S2, the injection device includes a three-way solenoid valve and a negative pressure tube, an injection tube and a fixed tube threadedly connected to the three-way solenoid valve, a liquid removal component is arranged in the negative pressure tube, the liquid removal component includes a plurality of staggered flaps and a sponge fixedly arranged on the flap, an extrusion component is arranged on the inner wall of the negative pressure tube, the fixed tube is used to seal after docking with the battery injection port, the injection tube is used to inject electrolyte into the battery after vacuuming the inside of the battery through the negative pressure tube, the liquid removal component absorbs the electrolyte in the negative pressure tube through the sponge, and the extrusion component is used to squeeze and recover the electrolyte in the sponge.

[0018] As a preferred embodiment, the liquid removal component also includes a slide groove opened on the inner wall of the negative pressure tube, a slider slidingly arranged in the slide groove, a slide plate slidingly arranged in the negative pressure tube, a plurality of through holes opened on the slide plate, a fixed rod fixedly arranged in the middle of the slide plate, a plurality of fixed plates fixedly arranged on the inner wall of the negative pressure tube, a push rod fixedly arranged on the fixed rod, and a connecting rod hingedly arranged on the flap and the push rod, a spring is connected between the slider and the slide groove, the slider is fixedly connected to the slide plate, and the flap is rotatably arranged on the fixed plate.

[0019] As a preferred embodiment, the extrusion assembly includes a plurality of accommodating cavities opened on the inner wall of the negative pressure tube, an extrusion plate slidably arranged in the accommodating cavity, a plurality of through ports opened on the accommodating cavity, a plurality of plugs fixedly arranged on the extrusion plate, through grooves opened on both sides of the accommodating cavity, extrusion rods fixedly arranged on both sides of the extrusion plate, and a plurality of channels opened on the inner wall of the negative pressure tube, a spring is connected between the extrusion plate and the accommodating cavity, the plug cooperates with the through port, the extrusion rod cooperates with the through groove, the flap cooperates with the extrusion rod, the channel is connected to the accommodating cavity, and the extrusion rod is a telescopic structure.

[0020] As a preference, a V-shaped liquid injection nozzle is provided on the fixing tube and the V-shaped liquid injection nozzle is embedded in the battery liquid injection port and communicated with the interior of the battery.

[0021] As a preference, a water level meter is provided on the liquid injection pipe, and the water level meter is electrically connected to the three-way solenoid valve.

[0022] As a preference, a rubber layer is provided on the flap and the rubber layer can be set to be any one of natural rubber or styrene-butadiene rubber.

[0023] The beneficial effects of the present invention are

[0024] 1. The present invention utilizes a low-temperature electrolyte storage at 0-6°C to transfer the electrolyte to a static electrolyte room. The workshop does not need to be shelved to heat up to 17°C-23°C, which saves process time and preheats the electrolyte storage room. The electrolyte is kept at a certain temperature before being injected into the battery, and the battery injection is completed through a circulating process. The low-temperature electrolyte injection method is improved while ensuring the injection effect and injection accuracy, shortening the battery manufacturing cycle, ensuring good infiltration of the battery electrode interface, better eliminating battery polarization, and enabling the cathode and anode to obtain a better and more effective chemical reaction, thereby effectively improving electrical performance and performance stability.

[0025] 2. The present invention is also provided with a liquid injection device, which drives the liquid to flow into the battery after reciprocating vacuum inside the battery. During the vacuuming process, the electrolyte in the negative pressure tube is absorbed to prevent the electrolyte from damaging the equipment, and the electrolyte is recovered at the same time.

[0026] In summary, the present invention has the advantages of good liquid injection effect and high efficiency, and is suitable for the technical field of energy storage battery equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings:

[0028] Figure 1 This is the disassembly result after infiltration;

[0029] Figure 2 This is the result of the full-power disassembly;

[0030] Figure 3 This is the performance test result diagram;

[0031] Figure 4 It is a structural schematic diagram of the liquid injection device;

[0032] Figure 5 Schematic diagram of the structure of the liquid removal component;

[0033] Figure 6 for Figure 5 Enlarged view of point A in the middle;

[0034] Figure 7 is a schematic diagram of the structure of the extrusion component;

[0035] Figure 8 Schematic diagram of the structure of the flap;

[0036] Figure 9 Schematic diagram of the structure of the extruded plate;

[0037] Figure 10 This is a schematic diagram of the state when the battery is vacuumed and liquid is removed;

[0038] Figure 11 for Figure 10 Enlarged view of point B in the middle;

[0039] Figure 12 A schematic diagram of the state of the battery being filled with electrolyte and squeezed out;

[0040] Figure 13 for Figure 12 Enlarged view of point C in the middle;

[0041] Figure 14 This is a schematic diagram of the state when the flap is tilted during vacuuming;

[0042] Figure numerals: 1 three-way solenoid valve, 2 negative pressure tube, 3 liquid injection tube, 4 fixed tube, 5 liquid removal assembly, 51 flip plate, 52 sponge, 53 slide groove, 54 slider, 55 slide plate, 56 through hole, 57 fixed rod, 58 fixed plate, 59 push rod, 510 connecting rod, 6 extrusion assembly, 61 accommodating chamber, 62 extrusion plate, 63 through port, 64 plug, 65 through groove, 66 extrusion rod, 67 channel, 7 V-type liquid injection nozzle, 8 water level meter. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings.

[0044] Example 1

[0045] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0046] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0047] S1. Remove excess water from the battery by vertical contact heating and baking, then preheat the electrolyte to 27°C, and cool the heated and baked battery to 42°C.

[0048] S2. Place the battery in a liquid injection device and evacuate the battery. When the vacuum reaches a predetermined value, stop evacuating the battery and inject liquid into the battery. When the injection volume is reached, stop injecting liquid and maintain the vacuum state for 30 seconds before transporting the battery to a static box.

[0049] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 60 seconds before circulating.

[0050] S4, vacuum the static box to -95Kpa, stop vacuuming and keep it for 120S before circulating;

[0051] S5. Repeat steps S3 and S4 three times, then sequentially release the pressure of the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection and proceed to the next process;

[0052] S6: Place the battery after injection in a high temperature room at 42°C for 24 hours, and then send it to the negative pressure formation process for formation.

[0053] It is worth mentioning that in S1, the baking is vertical contact baking, and the battery moisture content after baking is ≤200ppm.

[0054] In addition, in S1, the electrolyte preheating temperature range is 17℃-23℃, and the battery temperature range after cooling is 40℃-50℃.

[0055] It should be emphasized that in S6, the temperature range of the high temperature room is 42℃-48℃, and the static immersion time is 24h.

[0056] It should be further explained that if Figure 4 and Figure 14 As shown in S2, the liquid injection device includes a three-way solenoid valve 1 and a negative pressure tube 2, a liquid injection tube 3 and a fixed tube 4 threadedly connected to the three-way solenoid valve 1. A liquid removal component 5 is provided in the negative pressure tube 2. The liquid removal component 5 includes a plurality of staggered flaps 51 and a sponge 52 fixedly provided on the flap 51. An extrusion component 6 is provided on the inner wall of the negative pressure tube 2. The fixed tube 4 is used to seal after docking with the battery liquid injection port. The liquid injection tube 3 is used to inject the electrolyte into the battery after vacuuming the inside of the battery through the negative pressure tube 2. Internally, the liquid removal component 5 absorbs the electrolyte in the negative pressure tube 2 through the sponge 52, and the squeezing component 6 is used to squeeze and recover the electrolyte in the sponge 52. Among them, the three-way solenoid valve 1 is a three-way solenoid ball valve. By rotating the ball valve, the connection state between the fixed tube 4 and the negative pressure tube 2 and the injection tube 3 is switched. The three-way solenoid valve 1 is an existing mature technology and will not be described in detail here. The negative pressure tube 2 is connected to a negative pressure device, and the negative pressure inside the battery is pumped out through the negative pressure tube 2. One side of the injection tube 3 is connected to a load-bearing The electrolyte storage tank, when in use, after the fixed tube 4 is docked with the battery filling port, the three-way solenoid valve 1 drives the ball valve to connect the negative pressure tube 2 with the fixed tube 4, the negative pressure device is turned on, and negative pressure is pumped into the battery interior through the negative pressure tube 2 and the fixed tube 4. After the negative pressure reaches the set value, the negative pressure device stops, and the three-way solenoid valve 1 drives the ball valve to cut off the connection between the negative pressure tube 2 and the fixed tube 4, and at the same time connects the injection tube 3 with the fixed tube 4. Since the battery interior is in a negative pressure state, the electrolyte in the liquid storage tank will automatically flow into the injection tube 3 and into the battery interior from the fixed tube 4. In the process of the electrolyte flowing into the battery interior, if air enters or other external factors occur, the negative pressure inside the battery will gradually decrease, and the force of sucking electrolyte will become smaller and smaller. When the electrolyte in the injection tube 3 is less than the set value of the water level meter, the water level meter sends a signal to drive the three-way solenoid valve 1 to switch the ball valve, reconnecting the negative pressure tube 2 with the fixed tube 4, and the negative pressure device will pump negative pressure into the battery interior again, and repeat the above steps until the filling is completed.

[0057] It is worth mentioning that Figure 10 and Figure 11As shown, the liquid removal component 5 also includes a chute 53 provided on the inner wall of the negative pressure tube 2, a slider 54 slidably set in the chute 53, a slide plate 55 slidably set in the negative pressure tube 2, a plurality of through holes 56 provided on the slide plate 55, a fixed rod 57 fixedly set in the middle of the slide plate 55, a plurality of fixed plates 58 fixedly set on the inner wall of the negative pressure tube 2, a push rod 59 fixedly set on the fixed rod 57, and a connecting rod 510 hingedly set on the flap 51 and the push rod 59. A spring is connected between the slider 54 and the chute 53, the slider 54 is fixedly connected to the slide plate 55, and the flap 51 is rotatably set on the fixed plate 58, wherein the initial state of the flap 51 is a vertical state, fitting with the inner wall of the negative pressure tube 2. When in use, when the ball valve rotates during the injection process, the electrolyte adhering to the ball valve flows into the negative pressure tube 2. Therefore, when the negative pressure device is turned on, the airflow in the negative pressure tube 2 will drive the slide plate 55 to slide downward, the spring is compressed, and the flap 51 is driven to flip through the push rod 59 and the connecting rod 510, so that the flap 51 is in an inclined state. Under the influence of the airflow, the electrolyte flows along the inner wall of the negative pressure tube 2 until it flows to the sponge 52. The sponge 52 absorbs the electrolyte inside to ensure that the electrolyte will not damage the negative pressure device.

[0058] Further, such as Figure 12 and Figure 13 As shown, the extrusion assembly 6 includes a plurality of accommodating cavities 61 provided on the inner wall of the negative pressure tube 2, an extrusion plate 62 slidably arranged in the accommodating cavity 61, a plurality of through-ports 63 provided on the accommodating cavity 61, a plurality of plugs 64 fixedly provided on the extrusion plate 62, through-slots 65 provided on both sides of the accommodating cavity 61, an extrusion rod 66 fixedly provided on both sides of the extrusion plate 62, and a plurality of channels 67 provided on the inner wall of the negative pressure tube 2. A spring is connected between the extrusion plate 62 and the accommodating cavity 61, the plug 64 cooperates with the through-port 63, the extrusion rod 66 cooperates with the through-slot 65, the flap 51 cooperates with the extrusion rod 66, the channel 67 is connected to the accommodating cavity 61, and the extrusion rod 66 is a telescopic structure, wherein the initial state of the plug 64 is in contact with the through-port 63, the accommodating cavity 61 is in a sealed state, and the extrusion rod 66 is closed by a spring. The channel 67 is connected to a recycling box for collecting the electrolyte. During use, when the flap 51 is flipped to an inclined state, the extrusion plate 62 drives the plug 64 to block the opening 63 for sealing under the action of the spring, ensuring that the negative pressure work is completed smoothly and that the electrolyte flows smoothly into the sponge 52. When the negative pressure device stops working, the negative pressure tube 2 is depressurized. During the depressurization, the slide plate 55 slides upward under the action of the spring, and the flap 51 drives the sponge 52 to fit the inner wall of the negative pressure tube 2. When the flap 51 rotates, the extrusion rod 66 and the extrusion plate 62 are driven to move, so that the plug 64 is separated from the opening 63. When the flap 51 continues to rotate, the extrusion rod 66 contracts, and the sponge 52 is gradually squeezed, so that the internal electrolyte flows into the accommodating cavity 61 through the opening 63, and then flows into the recycling box from the channel 67.

[0059] In addition, if Figure 5 As shown, a V-shaped liquid injection nozzle 7 is provided on the fixed tube 4 and the V-shaped liquid injection nozzle 7 is embedded in the battery liquid injection port and communicated with the interior of the battery to ensure the sealing of the interior of the battery.

[0060] Further, such as Figure 5 As shown, a water level meter 8 is provided on the liquid injection pipe 3 , and the water level meter 8 is electrically connected to the three-way solenoid valve 1 .

[0061] It should be emphasized that if Figure 7 As shown, a rubber layer is provided on the flap 51 and the rubber layer can be set to any one of natural rubber or styrene-butadiene rubber to prevent the electrolyte from damaging the flap 51 and extend its service life.

[0062] Example 2

[0063] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0064] S1. Remove excess water from the battery by heating and baking, then preheat the electrolyte to 22°C, and cool the heated and baked battery to 42°C.

[0065] S2. Place the battery in the liquid injection device and evacuate it. When the vacuum reaches -95Kpa, stop evacuating the battery and inject liquid into it. When the injection volume is reached, stop injecting liquid and maintain the vacuum state of -95Kpa for 60 seconds before transporting it to a static box.

[0066] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 240 seconds before circulating.

[0067] S4, vacuum the static box to -95Kpa, stop vacuuming and keep it for 120S before circulating;

[0068] S5. Repeat steps S3 and S4 three times, then sequentially release the pressure of the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection and proceed to the next process;

[0069] S6: Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send it to the negative pressure formation process for formation.

[0070] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0071] Example 3

[0072] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0073] S1. Remove excess water from the battery by heating and baking, then preheat the electrolyte to 25°C, and cool the heated and baked battery to 45°C.

[0074] S2. Place the battery in the liquid injection device and evacuate it. When the vacuum reaches -95Kpa, stop evacuating the battery and inject liquid into it. When the injection volume is reached, stop injecting liquid and maintain the vacuum state of -95Kpa for 60 seconds before transporting it to a static box.

[0075] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 240 seconds before circulating.

[0076] S4, vacuum the static box to -95Kpa, stop vacuuming and keep it for 60S before circulating;

[0077] S5. Repeat steps S3 and S4 five times, then sequentially depressurize the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection before proceeding to the next process;

[0078] S6: Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send it to the negative pressure formation process for formation.

[0079] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0080] Example 4

[0081] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0082] S1. Remove excess water inside the battery by heating and baking, then preheat the electrolyte to 20°C, and cool the heated and baked battery to 48°C;

[0083] S2. Place the battery in the liquid injection device and evacuate it. When the vacuum reaches -95Kpa, stop evacuating the battery and inject liquid into it. When the injection volume is reached, stop injecting liquid and maintain the vacuum state of -95Kpa for 60 seconds before transporting it to a static box.

[0084] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 240 seconds before circulating.

[0085] S4, vacuum the static box to -95Kpa, stop vacuuming and keep it for 30S before circulating;

[0086] S5. Repeat steps S3 and S4 three times, then sequentially release the pressure of the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection and proceed to the next process;

[0087] S6: Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send it to the negative pressure formation process for formation.

[0088] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0089] Comparative Example 1

[0090] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0091] S1. Remove excess moisture from the battery by heating and baking, then preheat the electrolyte to 23°C, and cool the heated and baked battery to 23°C;

[0092] S2. Place the battery in the liquid injection device and evacuate it. When the vacuum reaches -95Kpa, stop evacuating the battery and inject liquid into it. When the injection volume is reached, stop injecting liquid and maintain the vacuum state of -95Kpa for 45 seconds before transporting it to a static box.

[0093] S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 10 seconds before circulating.

[0094] S4, vacuum the box to -95Kpa, stop vacuuming and keep it for 45S before circulating;

[0095] S5. Repeat steps S3 and S4 three times, then sequentially release the pressure of the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection and proceed to the next process;

[0096] S6: Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send it to the negative pressure formation process for formation.

[0097] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0098] Comparative Example 2

[0099] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0100] S1. Remove excess moisture inside the battery by heating and baking, and then preheat the electrolyte to 23°C;

[0101] S2. Preheat the electrolyte to 23°C and keep the temperature of the electrolyte unchanged before entering the battery cell;

[0102] S3. Cool the baked batteries to 42°C. During the cooling process, the temperature uniformity of the entire oven must be ensured.

[0103] S4. After removing the battery from the oven and cooling it, place it into the cup of the liquid filling machine. The liquid filling machine chamber is vacuumed. When the battery is removed from the oven, it is removed and enters the vacuum chamber of the liquid filling machine at the same time.

[0104] S5. When the vacuum degree reaches -95Kpa or higher, stop vacuuming and start filling the battery. When the set filling volume is reached, stop filling and maintain the pressure at -95Kpa for 5 minutes.

[0105] S6. Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send the battery to the formation process for formation.

[0106] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0107] Comparative Example 3

[0108] A method for injecting low-temperature electrolyte into a lithium-ion battery comprises the following steps:

[0109] S1. Remove excess moisture inside the battery by heating and baking, and then preheat the electrolyte to 23°C;

[0110] S2. Preheat the electrolyte to 19°C and keep the temperature of the electrolyte unchanged before entering the battery cell;

[0111] S3. Cool the baked batteries to 42°C. During the cooling process, the temperature uniformity of the entire oven must be ensured.

[0112] S4. After removing the battery from the oven and cooling it, place it into the cup of the liquid filling machine. The liquid filling machine chamber is vacuumed. When the battery is removed from the oven, it is removed and enters the vacuum chamber of the liquid filling machine at the same time.

[0113] S5. When the vacuum degree reaches -95Kpa or higher, stop vacuuming and start filling the battery. When the set filling volume is reached, stop filling and maintain the pressure at -95Kpa for 5 minutes.

[0114] S6. Place the battery after injection in a high temperature room at 45°C for 24 hours, and then send the battery to the formation process for formation.

[0115] Finally, the battery strip finally obtained in this embodiment was subjected to performance testing. The test items included: infiltration and disassembly to focus on the infiltration effect of the electrode diaphragm and the amount of free electrolyte; full-charge disassembly to focus on the appearance of the negative electrode and the black spot lithium precipitation; performance testing to focus on the first efficiency, first discharge capacity, and battery internal resistance. The test results are attached. Figure 1 To the attached Figure 3

[0116] Working process

[0117] When the fixed tube 4 is docked with the battery filling port, the three-way solenoid valve 1 drives the ball valve to connect the negative pressure tube 2 with the fixed tube 4, the negative pressure device is turned on, and the negative pressure inside the battery is pumped through the negative pressure tube 2 and the fixed tube 4. After the negative pressure reaches the set value, the negative pressure device stops, and the three-way solenoid valve 1 drives the ball valve to cut off the connection between the negative pressure tube 2 and the fixed tube 4, and at the same time connects the injection tube 3 with the fixed tube 4. Since the battery is in a negative pressure state, the electrolyte in the liquid storage tank will automatically flow into the injection tube 3 and flow into the battery from the fixed tube 4. During the process of filling the battery, air enters or other external reasons occur, causing the negative pressure inside the battery to gradually decrease, and the force of sucking electrolyte becomes smaller and smaller. After the electrolyte in the injection pipe 3 is less than the set value of the water level meter, the water level meter sends a signal to drive the three-way solenoid valve 1 to switch the ball valve, and reconnect the negative pressure pipe 2 with the fixed pipe 4. The negative pressure device re-extracts negative pressure from the battery, and repeats the above steps until the injection is completed. During the injection process, when the ball valve rotates, the electrolyte adhering to the ball valve flows into the negative pressure pipe 2. Therefore, when the negative pressure device is turned on , the airflow in the negative pressure tube 2 will drive the slide plate 55 to slide downward, the spring is compressed, and the flip plate 51 is flipped through the push rod 59 and the connecting rod 510, so that the flip plate 51 is in an inclined state. Under the influence of the airflow, the electrolyte flows along the inner wall of the negative pressure tube 2 until it flows to the sponge 52. The sponge 52 absorbs the electrolyte inside to ensure that the electrolyte does not damage the negative pressure device. When the flip plate 51 is flipped to an inclined state, the extrusion plate 62 drives the plug 64 under the action of the spring to block the opening 63 for sealing, ensuring that the negative pressure work is completed smoothly and the electricity is guaranteed. The electrolyte flows smoothly into the sponge 52. When the negative pressure device stops working, the negative pressure tube 2 is depressurized. During the depressurization, the slide plate 55 slides upward under the action of the spring, and the flap 51 drives the sponge 52 to fit the inner wall of the negative pressure tube 2. When the flap 51 rotates, it drives the extrusion rod 66 and the extrusion plate 62 to move, so that the plug 64 is separated from the opening 63. When the flap 51 continues to rotate, the extrusion rod 66 contracts, and the sponge 52 is gradually squeezed, and the internal electrolyte flows into the accommodating cavity 61 through the opening 63, and then flows into the recovery box from the channel 67.

[0118] In the description of the present invention, it should be understood that the terms "front and back", "left and right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the equipment or components referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the invention.

[0119] Of course, in this technical solution, those skilled in the art should understand that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0120] The above description in conjunction with the accompanying drawings is only a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment. It should be pointed out that for those skilled in the art, various modifications and improvements can be made without departing from the structure of the present invention. These should also be regarded as the scope of protection of the present invention and will not affect the effect and practicality of the implementation of the present invention.

Claims

1. A method for injecting low-temperature electrolyte into a lithium-ion battery, comprising the following steps: S1. Remove excess water inside the battery by heating and baking, then place the electrolyte aside for preheating, and cool the heated and baked battery; S2. Place the battery in a liquid injection device and evacuate the battery. When the vacuum reaches a predetermined value, stop evacuating the battery and inject liquid into the battery. When the injection volume is reached, stop injecting liquid and maintain the vacuum state for 30s-60s before transporting the battery to a static box. S3. After the vacuum wall in the static chamber is broken, nitrogen positive pressure is input into the static chamber. When the nitrogen positive pressure in the static chamber reaches 0.65 MPa, the injection is stopped and maintained for 60s-240s before circulation. S4. Vacuum the static box to -90Kpa ～ -95Kpa, stop vacuuming and keep it for 30S-120S before circulating; S5. Repeat steps S3 and S4 for 3-10 times, then sequentially release the pressure of the vacuum and nitrogen chambers, insert the sealing nails before removing the battery, and complete the liquid injection and proceed to the next process; S6: Place the battery after liquid injection in a high temperature room for static immersion and related process aging, and then the battery can be sent to the negative pressure formation process for formation.

2. The method for injecting a low-temperature electrolyte into a lithium-ion battery according to claim 1, wherein: In S1, the baking is vertical contact baking, and the moisture content of the battery after baking is ≤200ppm.

3. The method for injecting a low-temperature electrolyte into a lithium-ion battery according to claim 1, wherein: In the above S1, the electrolyte is preheated to a temperature range of 17°C-23°C, and the battery temperature after cooling is in a range of 40°C-50°C.

4. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 1, wherein: In S6, the temperature range of the high temperature room is 42° C.-48° C., and the static soaking time is 24 hours.

5. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 1, wherein: In the S2, the liquid injection device comprises a three-way solenoid valve (1) and a negative pressure tube (2), a liquid injection tube (3) and a fixed tube (4) threadedly connected to the three-way solenoid valve (1); a liquid removal assembly (5) is provided in the negative pressure tube (2); the liquid removal assembly (5) comprises a plurality of staggered flaps (51) and a sponge (52) fixedly arranged on the flap (51); an extrusion assembly (6) is provided on the inner wall of the negative pressure tube (2); the fixed tube (4) is used to seal after docking with the battery liquid injection port; the liquid injection tube (3) is used to inject electrolyte into the battery after vacuuming the inside of the battery through the negative pressure tube (2); the liquid removal assembly (5) absorbs the electrolyte in the negative pressure tube (2) through the sponge (52); and the extrusion assembly (6) is used to squeeze and recover the electrolyte in the sponge (52).

6. A method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 5, characterized in that: The liquid removal assembly (5) further comprises a chute (53) provided on the inner wall of the negative pressure tube (2), a slider (54) slidably provided in the chute (53), a slide plate (55) slidably provided in the negative pressure tube (2), a plurality of through holes (56) provided on the slide plate (55), a fixed rod (57) fixedly provided in the middle of the slide plate (55), a plurality of fixed plates (58) fixedly provided on the inner wall of the negative pressure tube (2), a push rod (59) fixedly provided on the fixed rod (57), and a connecting rod (510) hingedly provided on the flap (51) and the push rod (59). A spring is connected between the slider (54) and the chute (53), the slider (54) is fixedly connected to the slide plate (55), and the flap (51) is rotatably provided on the fixed plate (58).

7. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 5, wherein: The extrusion assembly (6) comprises a plurality of accommodating cavities (61) provided on the inner wall of the negative pressure tube (2), an extrusion plate (62) slidably arranged in the accommodating cavity (61), a plurality of through-ports (63) provided on the accommodating cavity (61), a plurality of plugs (64) fixedly arranged on the extrusion plate (62), through-slots (65) provided on both sides of the accommodating cavity (61), an extrusion rod (66) fixedly arranged on both sides of the extrusion plate (62), and a plurality of channels (67) provided on the inner wall of the negative pressure tube (2). A spring is connected between the extrusion plate (62) and the accommodating cavity (61), the plug (64) cooperates with the through-ports (63), the extrusion rod (66) cooperates with the through-slot (65), the flap (51) cooperates with the extrusion rod (66), the channel (67) is connected with the accommodating cavity (61), and the extrusion rod (66) is a telescopic structure.

8. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 5, wherein: The fixed tube (4) is provided with a V-shaped liquid injection nozzle (7), and the V-shaped liquid injection nozzle (7) is embedded in the battery liquid injection port and communicates with the interior of the battery.

9. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 5, wherein: The liquid injection pipe (3) is provided with a water level meter (8), and the water level meter (8) is electrically connected to the three-way electromagnetic valve (1).

10. The method for injecting low-temperature electrolyte into a lithium-ion battery according to claim 5, wherein: The flap (51) is provided with a rubber layer, and the rubber layer can be set to any one of natural rubber and styrene-butadiene rubber.

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