Lithium ion battery manufacturing method, lithium ion battery

Abstract

The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium ion battery manufacturing method and a lithium ion battery, comprising the following steps: step S1, stirring to obtain a premix; step S2, coating the premix to obtain a prefabricated material; step S3, roll-cutting the prefabricated material to obtain positive and negative electrode sheets; step S4, winding the positive and negative electrode sheets to obtain a bare battery cell; step S5, laser die-cutting the bare battery cell to obtain a first battery cell; step S6, hot-pressing the first battery cell to obtain a second battery cell; step S7, ultrasonically welding the second battery cell to obtain a third battery cell; step S8, welding the third battery cell with an adapter to obtain a fourth battery cell; step S9, assembling the fourth battery cell to obtain a lithium ion battery; wherein the laser die-cutting uses three-level laser parameters to cut the pole ears under a full negative pressure environment; and the scanning direction of the laser die-cutting is vertical up and down.

Description

Technical Field

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

[0002] At present, in the square aluminum shell lithium-ion battery industry, the conventional process flow of electrodes and assembly sections is "stirring-coating-roll cutting-die cutting-winding-hot pressing-ultrasonic welding-adapter welding-assembly". In the roll cutting process, the coated incoming material is rolled to a certain thickness of positive and negative electrodes according to the roll gap and pressure parameters required by the process, and the slitting is completed. In the die-cutting process, the uncoated empty foil area of ​​the incoming electrode material is cut by hardware or laser cutting to make the electrode sheet with the required ear size and ear spacing. Then the electrode sheet flows to the winding process, and the positive and negative electrode sheets are combined with the diaphragm and wound to form a bare battery cell with the ear alignment meeting the requirements (the positive and negative electrode sheet ears are located on the same side of the battery cell).

[0003] During the die-cutting stage, for foils with inconsistent thickness, there will be a problem of excess heat in the die-cutting process, which will lead to the generation of molten beads and cause safety problems; there will be a phenomenon of ear misalignment in the winding process, and the root cause is the inconsistent thickness of the roller-cut pole pieces. The above two steps have now become the main problems in battery cell production.

[0004] Therefore, how to overcome the safety and quality issues brought about by electrodes of different thicknesses is a technical challenge to be solved in the industry. Summary of the invention

[0005] The present invention provides a lithium ion battery manufacturing method and a lithium ion battery, so as to solve the problems of excess heat and misalignment of pole tabs caused by different pole piece thicknesses in current lithium ion batteries.

[0006] In order to solve the above technical problems, the present invention provides a method for manufacturing a lithium-ion battery, comprising the following steps: step S1, stirring to obtain a premix; step S2, coating the premix to obtain a prefabricated material; step S3, roll-cutting the prefabricated material to obtain positive and negative electrode sheets; step S4, winding the positive and negative electrode sheets to obtain a bare battery cell; step S5, laser die-cutting the bare battery cell to obtain a first battery cell; step S6, hot-pressing the first battery cell to obtain a second battery cell; step S7, ultrasonically welding the second battery cell to obtain a third battery cell; step S8, welding the third battery cell with an adapter to obtain a fourth battery cell; step S9, assembling the fourth battery cell to obtain a lithium-ion battery; wherein the laser die-cutting uses three-level laser parameters to cut the pole ears under a full negative pressure environment; and the scanning direction of the laser die-cutting is vertical up and down.

[0007] Furthermore, the roll cutting in step S3 includes: rolling the prefabricated material coated in step S2 to positive and negative electrode sheets of a certain thickness according to the set roll gap and pressure parameters, and completing the slitting.

[0008] Furthermore, the winding in step S4 includes: winding the positive and negative electrode sheets obtained after roller cutting in step S3 with the separator in a relative position of the empty foil to form a bare battery cell; wherein the positive and negative electrode tabs of the battery cell are respectively arranged on both sides of the battery cell.

[0009] Furthermore, the laser die-cutting in step S5 includes: placing the bare battery cell wound in step S4 on a laser cutting platform, and cutting the inner foil according to the set laser cutting parameters of the positive and negative electrode sheets and along the laser scanning trajectory until all the foil is cut and removed to form a first battery cell with the positive and negative electrode tab sizes required by the process.

[0010] Furthermore, the laser cutting parameters of the negative electrode plate include: the first level, suitable for cutting the 1st to 22nd layers of foil, using a power of 1000±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the second level, suitable for cutting the 23rd to 40th layers of foil, using a power of 900±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 5s after cutting to cool and remove dust from the foil; the third level, suitable for cutting the remaining layers of foil, using a power of 500±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

[0011] Furthermore, the laser cutting parameters of the positive electrode plate include: the first level, suitable for cutting the 1st to 22nd layers of foil, using a power of 900±100W, a laser frequency of 400±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the second level, suitable for cutting the 23rd to 40th layers of foil, using a power of 800±100W, a laser frequency of 400±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the third level, suitable for cutting the remaining layers of foil, using a power of 400±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

[0012] Furthermore, the length of the positive and negative electrode tabs extending out of the separator is 26.5±1 mm, the width of the bottom of the tab is 40±1 mm, and the distance between the positive and negative electrode tabs and the side edges is 65±1 mm.

[0013] Furthermore, the hot pressing in step S6 includes: hot pressing the first battery cell after laser die-cutting in step S5 according to parameters required by the process to obtain a second battery cell.

[0014] Furthermore, the ultrasonic welding in step S7 includes: overlapping the positive and negative electrode tabs on both sides of the second battery cell after hot pressing in step S6 with the copper-aluminum adapter sheet respectively, and completing ultrasonic welding according to the amplitude, energy, and time parameters required by the process to obtain a third battery cell; wherein the positive electrode tab is welded to the aluminum adapter sheet, and the negative electrode tab is welded to the copper adapter sheet.

[0015] Furthermore, the adapter plate welding in step S8 includes:

[0016] After the ultrasonic welding in step S7, the third battery cell is overlapped with the top cover, and the laser welding process is used to complete the welding of the adapter according to the welding speed, power and defocus parameters required by the process to obtain the fourth battery cell.

[0017] In another aspect, the present invention further provides a lithium ion battery obtained by the manufacturing method as described above.

[0018] The beneficial effect of the present invention is that the lithium ion battery manufacturing method and the lithium ion battery of the present invention apply laser die-cutting to the lithium battery cell tabs in an alternative way, and improve the die-cutting before winding to winding before laser die-cutting, and directly perform laser die-cutting on the entire cell tabs after winding, and utilize the vertical vertical scanning direction of the laser to make the cutting position of each layer of the positive and negative electrodes consistent, and each layer of the tabs will not have misalignment after cutting, which fundamentally solves the problem of tab alignment. At the same time, the three-level parameter design method also avoids the problem of excess heat from laser die-cutting, which leads to the generation of molten beads and thus affects safety, thereby greatly improving the product yield.

[0019] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below for detailed description as follows. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to solve the problem of misaligned pole tabs, the existing process proposes a closed-loop roller-cut control of pole piece thickness, but this technology is immature, automatic adjustment has lags, and the effect is not good; employees adjust the roller pressure to control the pole piece thickness, but this technology has lags and misjudgment risks, and the effect is not good; employees identify and manually remove pole pieces with abnormal roller-cut thickness, but this technology has the risk of missing and scrapping; the die-cutting length calculation logic comes from the digital electrical feedback of the length-counting roller and the encoder, but during the production operation, there are often abnormalities between the length-counting roller and the encoder, resulting in abnormal pole tab spacing, resulting in batch winding misalignment; die-cutting adopts the "hardware" die-cutting method, and there are conditions such as die wear that affect the cutting quality, such as wire drawing, shavings, and continuous cutting, which affects product safety. At the same time, the life management of the die is difficult and requires frequent replacement, which is not conducive to cost control.

[0023] At least one embodiment provides a method for manufacturing a lithium-ion battery, comprising the following steps: step S1, stirring to obtain a premix; step S2, coating the premix to obtain a prefabricated material; step S3, roll-cutting the prefabricated material to obtain positive and negative electrode sheets; step S4, winding the positive and negative electrode sheets to obtain a bare battery cell; step S5, laser die-cutting the bare battery cell to obtain a first battery cell; step S6, hot-pressing the first battery cell to obtain a second battery cell; step S7, ultrasonically welding the second battery cell to obtain a third battery cell; step S8, welding the third battery cell with an adapter to obtain a fourth battery cell; step S9, assembling the fourth battery cell to obtain a lithium-ion battery; wherein the laser die-cutting uses three-level laser parameters to cut the pole ears under a negative pressure environment throughout the process; and the scanning direction of the laser die-cutting is vertical up and down.

[0024] In this embodiment, specifically, the "die-cutting-winding" process in the conventional electrode and assembly stage process is changed to "winding-laser die-cutting", and the battery cell pole ears are directly laser die-cut as a whole after winding, without the need for pole piece tape die-cutting, thereby saving equipment usage space and shortening the battery cell production flow time.

[0025] In this embodiment, specifically, after the winding is completed, the bare battery cell is fixed on the winding machine using hot melt adhesive to facilitate the subsequent laser die-cutting process.

[0026] In this embodiment, specifically, in the laser die-cutting process, the laser trajectory is set according to a specific process to scan and cut the positive and negative ears of the battery cell as a whole, and the laser scanning direction is the up and down vertical direction, so the cutting position of each layer of empty foil of the positive and negative electrodes is consistent, and there is no misalignment of each layer of ears after cutting, which fundamentally solves the problem of ear alignment.

[0027] In this embodiment, specifically, the laser operation parameters are designed using three-level parameters, that is, different process parameter designs are used for cutting different layers of foil combinations, so as to avoid safety problems caused by excess heat during the laser die-cutting process.

[0028] The rolling cutting in step S3 includes: rolling the prefabricated material coated in step S2 to positive and negative electrode sheets of a certain thickness according to the set rolling gap and pressure parameters, and completing the cutting.

[0029] The winding in step S4 includes: winding the positive and negative electrode sheets obtained after the roll cutting in step S3 with the separator in the relative position of the empty foil to form a bare battery cell; wherein the positive and negative electrode tabs of the battery cell are respectively arranged on both sides of the battery cell.

[0030] Among them, the laser die-cutting in step S5 includes: placing the bare battery cell wound in step S4 on the laser cutting platform; moving the contoured protective cover plate to the surface of the battery cell pole ear to protect the battery cell, and the contoured protective cover plate is hollowed out for the laser line scanning area; turning on the negative pressure dust removal, and the dust removal wind speed is greater than 23m / s; using the laser galvanometer drive mode; the positive and negative electrode foils are melted and vaporized in the high temperature environment generated by the laser scanning trajectory to complete the cutting, and compressed cooling air is used to purge the battery cell foil to ensure that there are no burrs and molten beads on the cutting surface that affect product safety. Synchronously turn on the negative pressure dust removal to remove the surface foil that has been cut; repeat the above process to continue to complete the cutting of the inner foil according to the laser scanning trajectory until all the foils are cut and removed to make the first battery cell with the pole ear size required by the process.

[0031] Among them, the laser galvanometer driving mode is preferably carried out by the American IPG fiber laser.

[0032] Among them, the laser cutting parameters of the negative electrode plate include: the first level, suitable for cutting the 1st to 22nd layers of foil, using a power of 1000±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the second level, suitable for cutting the 23rd to 40th layers of foil, using a power of 900±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 5s after cutting to cool and remove dust from the foil; the third level, suitable for cutting the remaining layers of foil, using a power of 500±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

[0033] Among them, the laser cutting parameters of the positive electrode plate include: the first level, suitable for cutting the 1st to 22nd layers of foil, using a power of 900±100W, a laser frequency of 400±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the second level, suitable for cutting the 23rd to 40th layers of foil, using a power of 800±100W, a laser frequency of 400±20KHz, a scanning speed of 100±10mm / s, and using compressed cooling air for 10s after cutting to cool and remove dust from the foil; the third level, suitable for cutting the remaining layers of foil, using a power of 400±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

[0034] Among them, the length of the positive and negative electrode ears extending out of the diaphragm is 26.5±1mm, the width of the bottom of the ear is 40±1mm, and the distance between the positive and negative electrode ears and the side edges is 65±1mm.

[0035] The hot pressing in step S6 includes: hot pressing the first battery cell after laser die-cutting in step S5 according to the parameters required by the process to obtain the second battery cell.

[0036] Among them, the ultrasonic welding in step S7 includes: overlapping the positive and negative electrode tabs on both sides of the second battery cell after hot pressing in step S6 with the copper-aluminum adapter sheet respectively, and completing ultrasonic welding according to the amplitude, energy and time parameters required by the process to obtain a third battery cell; wherein the positive electrode tab is welded to the aluminum adapter sheet, and the negative electrode tab is welded to the copper adapter sheet.

[0037] Among them, the adapter welding in step S8 includes: overlapping the third battery cell and the top cover after ultrasonic welding in step S7, using a laser welding process, completing the adapter welding according to the welding speed, power, and defocus parameters required by the process, and obtaining a fourth battery cell.

[0038] At least one embodiment further provides a lithium-ion battery obtained by the manufacturing method as described above.

[0039] Embodiment: A lithium battery is prepared according to the above method, wherein the key steps and parameters are as follows:

[0040] Step S3, roller cutting process:

[0041] Negative electrode: according to the process requirements, set the roller gap: 1470±50 um, roller pressure: 70±20 T, and thread the coated prefabricated material (width 882±1mm) in the order of roller cutting and roller cutting, and complete the "one-to-four" slitting at a speed of 90±10m / s.

[0042] Key product parameter requirements: rolling thickness 160±3μm, width 220.5±0.5mm.

[0043] Positive electrode: according to the process requirements, the roller gap is set to 1450±50 um, the roller pressure is 70±20 T, the coated prefabricated material (width 876±1mm) is threaded in the order of roller cutting and passing through the roller, and the roller is pressed at a speed of 90±10m / s to complete the "one-to-four" slitting.

[0044] Key product parameter requirements: rolling thickness 120±3μm, width 219±0.5mm.

[0045] After the product parameters are monitored and the appearance is qualified, it will flow to the next winding process.

[0046] Step S4, winding process:

[0047] The upper and lower diaphragms (specifications: 7um base film + 3μm ceramic layer + 3μm*2 PVDF layer = 16μm total thickness; 195±1mm width), positive and negative pole pieces (placed in relative positions with empty foils to ensure that the pole ears are located on both sides of the battery cell) are threaded in the order of front and back of the roller.

[0048] The diaphragm tension was set at 200±50gf, and starting from the 9th turn, the tension was reduced by 3gf per turn until it reached 100gf. The positive and negative electrode sheet tensions were set at 600±100gf, and starting from the 9th turn, the tension was reduced by 5gf per turn until it reached 500gf. The winding speed was set at 2m / s for the winding operation, wherein the positive electrode sheet was wound 51 turns, the negative electrode sheet was wound 52 turns, and the upper and lower diaphragms were wound 54 turns.

[0049] The key product parameter overhang (the size of the negative electrode edge exceeding the positive electrode) requires: the negative electrode exceeds the starting position of the positive electrode by 8±3mm; the negative electrode exceeds the ending position of the positive electrode by 10±5mm; the negative electrode on the tab side exceeds the positive electrode by 1.5±0.5mm, and the separator exceeds the negative electrode by 3.5±1mm.

[0050] After the product parameters are monitored and the appearance is qualified, it will flow to the next hot pressing process.

[0051] Step S5, laser die-cutting process:

[0052] Set the specific laser scanning trajectory according to the size requirements; set the negative laser cutting parameters: the first level is suitable for cutting the 1st to 22nd layers of foil, with a power of 1000±100W, a laser frequency of 500±20KHz, and a scanning speed of 100±10mm / s. After cutting, use compressed cooling air to blow for 10s to cool and remove dust from the foil; the second level is suitable for cutting the 23rd to 40th layers of foil, with a power of 900±100W, a laser frequency of 500±20KHz, and a scanning speed of 100±10mm / s. After cutting, use compressed cooling air to blow for 5s to cool and remove dust from the foil; the third level is suitable for cutting the remaining layers of foil, with a power of 500±100W, a laser frequency of 400±20KHz, and a scanning speed of 10 0±10mm / s; Set positive laser cutting parameters: the first level is suitable for cutting the 1st to 22nd layers of foil, with a power of 900±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s. After cutting, use compressed cooling air to blow for 10s to cool and remove dust from the foil; the second level is suitable for cutting the 23rd to 40th layers of foil, with a power of 800±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s. After cutting, use compressed cooling air to blow for 10s to cool and remove dust from the foil; the third level is suitable for cutting the remaining layers of foil, with a power of 400±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

[0053] Key product parameter requirements: The length of the positive and negative tabs extending out of the diaphragm is 26.5±1 mm, the width of the tab bottom is 40±1 mm; the distance between the positive and negative tabs and the side margins is 65±1 mm.

[0054] After the product parameters are monitored and the appearance is qualified, it will flow to the next hot pressing process.

[0055] Step S6, hot pressing process:

[0056] Set the hot pressing pressure to 6500±200 Kgf, the hot pressing temperature to 95±5 ℃, and press the upper and lower hot pressing plates together for 180±2s.

[0057] Key product parameter requirements: The length of the positive and negative tabs extending out of the diaphragm is 26.5±1 mm, the width of the tab bottom is 40±1 mm; the distance between the positive and negative tabs and the side edges is 65.5±1 mm.

[0058] After the product parameters are monitored and the appearance is qualified, it will flow to the next ultrasonic welding process.

[0059] Step S7, ultrasonic welding process:

[0060] Use "energy mode" welding, set the positive electrode welding parameters: welding amplitude 38±5 um, welding pressure 35±5psi, welding energy 230±50 J; set the negative electrode welding parameters: welding amplitude 35±5 um, welding pressure 35±5 psi, welding energy 320±50 J.

[0061] After hot pressing and punching, the positive and negative electrode tabs on both sides of the battery cell are overlapped with the copper-aluminum adapter respectively, the positive electrode tab is welded to the aluminum adapter, and the negative electrode tab is welded to the copper adapter, and the ultrasonic welding program is started to complete the welding.

[0062] Key product parameter requirements: Positive and negative electrode peeling residual area ≥ 60%, positive and negative electrode peeling force ≥ 60 N.

[0063] After the product parameters are monitored and the appearance is qualified, it will flow to the next adapter welding process.

[0064] Step S8, adapter welding process:

[0065] Set the positive laser parameters: welding speed 50 mm / s, laser output power 2400±200 W, defocus 0±2 mm; set the negative laser parameters: welding speed 50 mm / s, laser output power 4500±200 W, defocus 0±2 mm; overlap the battery cell and the top cover after ultrasonic welding, and start the laser welding program to complete the welding.

[0066] Key product parameter requirements: The width of the molten pool on the positive electrode surface is ≥0.9mm, the peeling force is ≥100N, and the residual area is ≥80%; the width of the molten pool on the negative electrode surface is ≥0.6mm, the peeling force is ≥100N, and the residual area is ≥80%.

[0067] After the key parameters of the product are monitored and the appearance is qualified, it will flow to the next assembly process.

[0068] The parameters in the laser die-cutting process in step S5 were tested, and the parameters and performance results are shown in the following Examples 1-3 and Comparative Examples 1-3:

[0069] In Example 1, three-level laser parameters are used to cut the tabs, and the parameters are set as follows:

[0070] The three-stage cutting process of the negative electrode: first cut 1~22 layers of foil, use power 1100w, laser frequency 500KHz, scanning speed 100mm / s; use compressed cooling air to purge for 10s to cool and remove dust from the foil; then cut 23~40 layers of foil, use power 1000w, laser frequency 500KHz, scanning speed 100mm / s; use compressed cooling air to purge for 5s to cool and remove dust from the foil; the remaining layers of foil use power 700w, laser frequency 400KHz, scanning speed 100mm / s, after cutting, check the appearance of the pole ear for molten beads, burrs, and other poor appearance phenomena;

[0071] Positive electrode three-level cutting process: first cut 1~22 layers of foil, use power 1000w, laser frequency 400KHz, scanning speed 100mm / s; use compressed cooling air to purge for 10s to cool and remove dust from the foil, then cut 23~40 layers of foil using power 900w, laser frequency 400KHz, scanning speed 100mm / s; use compressed cooling air to purge for 10s to cool and remove dust from the foil, and the remaining layers of foil use power 500w, laser frequency 400KHz, scanning speed 100mm / s. After cutting, check the appearance of the pole ear for any molten beads, burrs, and other poor appearance phenomena.

[0072] Example 2: Using three-level laser parameters to cut the tabs, the parameters are set as follows:

[0073] The three-level cutting process of the negative electrode: first cut 1~22 layers of foil, use power 1000w, laser frequency 500KHz, scanning speed 100mm / s; use compressed cooling air to purge for 10s to cool and remove dust from the foil; then cut 23~40 layers of foil using power 900w, laser frequency 500KHz, scanning speed 100mm / s; use compressed cooling air to purge for 5s to cool and remove dust from the foil; the remaining layers of foil use power 600w, laser frequency 400KHz, scanning speed 100mm / s, after cutting, check the appearance of the pole ear for molten beads, burrs, and other poor appearance phenomena;

[0074] Positive three-stage cutting process: first cut 1~22 layers of foil, use 900w power, 400KHz laser frequency, and 100mm / s scanning speed. Use compressed cooling air to purge for 10s to cool and remove dust from the foil, and then cut 23~40 layers of foil using 800w power, 400KHz laser frequency, and 100mm / s scanning speed; use compressed cooling air to purge for 10s to cool and remove dust from the foil, and use 400w power, 400KHz laser frequency, and 100mm / s scanning speed for the remaining layers of foil. After cutting, check the appearance of the pole ear for any molten beads, burrs, and other undesirable appearance phenomena.

[0075] Example 3, using three-level laser parameters to cut the pole ear, the parameters are set as follows:

[0076] The three-stage cutting process of the negative electrode: first cut 1~22 layers of foil, use 900w power, 500KHz laser frequency, and 100mm / s scanning speed; use compressed cooling air to purge for 10s to cool and remove dust from the foil; then cut 23~40 layers of foil using 800w power, 500KHz laser frequency, and 100mm / s scanning speed; use compressed cooling air to purge for 5s to cool and remove dust from the foil; the remaining layers of foil use 500w power, 400KHz laser frequency, and 100mm / s scanning speed. After cutting, check the appearance of the pole ear for any molten beads, burrs, and other poor appearance phenomena;

[0077] Positive electrode three-level cutting process: first cut 1~22 layers of foil, use 800w power, 400KHz laser frequency, and 100mm / s scanning speed; use compressed cooling air to purge for 10s to cool and remove dust from the foil; then cut 23~40 layers of foil, use 700w power, 400KHz laser frequency, and 100mm / s scanning speed; use compressed cooling air to purge for 10s to cool and remove dust from the foil; for the remaining layers of foil, use 300w power, 400KHz laser frequency, and 100mm / s scanning speed. After cutting, check that there are no molten beads on the appearance of the pole ear, burrs, and other poor appearance phenomena.

[0078] In comparative example 1, conventional laser die-cutting was used to cut a single-layer pole piece, with a laser power of 80w, a laser frequency of 500KHz, and a scanning speed of 100mm / s. Because the existing process involves die-cutting of multiple layers of pole pieces for wound cells, conventional laser die-cutting parameters resulted in uncut parts.

[0079] In comparative example 2, conventional laser die-cutting was used to cut the pole ears of the battery cell formed by winding the pole pieces. The laser power was 80w, the laser frequency was 500KHz, and the scanning speed was 100mm / s. Because it involved cutting of multiple layers of pole pieces, the conventional laser die-cutting parameters resulted in continuous cutting.

[0080] Comparative Example 3, in order to ensure cutting integrity, the process of Example 1 is adopted but the third-level laser is changed to a first-level laser. The difference is that the first-level laser adopts a laser power of 1000w, a laser frequency of 500KHz, and a scanning speed of 100mm / s; a molten bead phenomenon occurs, affecting product safety.

[0081] In this embodiment, specifically, the use of three-level laser parameters in conjunction with a purging and cooling process can avoid the occurrence of molten beads due to excessive power and burr problems due to excessive power after scanning of the tabs, thereby greatly improving the quality of lithium-ion batteries.

[0082] In summary, the lithium ion battery manufacturing method and the lithium ion battery of the present invention apply laser die-cutting to the lithium battery cell tabs in an alternative way, and improve the die-cutting before winding to winding before laser die-cutting, and directly perform laser die-cutting on the entire cell tabs after winding, and utilize the vertical vertical scanning direction of the laser to make the cutting position of each layer of the positive and negative electrodes consistent, and there will be no misalignment of each layer of tabs after cutting, which fundamentally solves the problem of tab alignment. At the same time, the three-level parameter design method also avoids the problem of excess heat from laser die-cutting, which leads to the generation of molten beads and thus affects safety, thereby greatly improving the product yield.

[0083] In this embodiment, specifically, the PID is a basic regulation mode of the control system, which is a linear regulation law with proportional, integral and differential effects.

[0084] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0085] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for manufacturing a lithium ion battery, characterized in that: The steps include: S1, stirring to obtain a premix; S2, coating the premix to obtain a prefabricated material; S3, roller cutting the preform to obtain positive and negative electrode sheets; S4, winding the positive and negative electrode sheets to obtain a bare battery cell; S5, laser die-cutting the bare battery cell to obtain a first battery cell; S6, hot pressing the first battery cell to obtain a second battery cell; S7, ultrasonically welding the second battery cell to obtain a third battery cell; S8, welding the third battery cell with the adapter to obtain a fourth battery cell; S9, assembling the fourth battery cell to obtain a lithium-ion battery; in The laser die-cutting uses three-level laser parameters to cut the tabs in a negative pressure environment throughout the process; as well as The scanning direction of the laser die-cutting is vertical up and down; The laser die-cutting in step S5 includes: The bare battery cell wound in step S4 is placed on a laser cutting platform, and the inner foil is cut according to the set laser cutting parameters of the positive and negative electrode sheets and the laser scanning trajectory until all the foils are cut and removed to form a first battery cell with positive and negative electrode tab sizes that meet the process requirements; The laser cutting parameters of the negative electrode sheet include: The first level is suitable for cutting the 1st to 22nd layers of foil, using a power of 1000±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and a compressed cooling air purge for 10s after cutting; The second level is suitable for cutting the 23rd to 40th layers of foil, using a power of 900±100W, a laser frequency of 500±20KHz, a scanning speed of 100±10mm / s, and a compressed cooling air purge for 5s after cutting. The third level is suitable for cutting the remaining layer of foil, using a power of 500±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

2. The method for manufacturing a lithium-ion battery according to claim 1, wherein: The roller cutting in step S3 includes: The prefabricated material after coating in step S2 is rolled to positive and negative electrode sheets of a certain thickness according to the set roller gap and pressure parameters, and then cut.

3. The method for manufacturing a lithium ion battery according to claim 1, wherein: The winding in step S4 includes: The positive and negative electrode sheets obtained after the roll cutting in step S3 are wound with the separator in the relative position of the empty foil to form a bare battery cell; wherein The positive and negative tabs of the battery cell are respectively arranged on both sides of the battery cell.

4. The method for manufacturing a lithium-ion battery according to claim 1, wherein: The laser cutting parameters of the positive electrode sheet include: The first level is suitable for cutting the 1st to 22nd layers of foil. The power is 900±100W, the laser frequency is 400±20KHz, and the scanning speed is 100±10mm / s. After cutting, compressed cooling air is used for 10s to cool and remove dust from the foil. The second level is suitable for cutting the 23rd to 40th layers of foil. The power is 800±100W, the laser frequency is 400±20KHz, and the scanning speed is 100±10mm / s. After cutting, compressed cooling air is used for 10s to cool and remove dust from the foil. The third level is suitable for cutting the remaining layer of foil, using a power of 400±100W, a laser frequency of 400±20KHz, and a scanning speed of 100±10mm / s.

5. The method for manufacturing a lithium-ion battery according to claim 1, wherein: The length of the positive and negative electrode tabs extending out of the diaphragm is 26.5±1 mm, the width of the bottom of the tabs is 40±1 mm, and the distance between the positive and negative electrode tabs and the side edges is 65±1 mm.

6. The method for manufacturing a lithium ion battery according to claim 1, wherein: The hot pressing in step S6 includes: The first battery cell after laser die-cutting in step S5 is hot-pressed according to the parameters required by the process to obtain a second battery cell.

7. The method for manufacturing a lithium ion battery according to claim 1, wherein: The ultrasonic welding in step S7 includes: After hot pressing in step S6, the positive and negative electrode tabs on both sides of the second battery cell are overlapped with the copper-aluminum adapter sheet respectively, and ultrasonic welding is completed according to the amplitude, energy and time parameters required by the process to obtain a third battery cell; wherein The positive electrode tab is welded to the aluminum adapter plate, and the negative electrode tab is welded to the copper adapter plate.

8. The method for manufacturing a lithium-ion battery according to claim 1, wherein: The adapter plate welding in step S8 includes: After the ultrasonic welding in step S7, the third battery cell is overlapped with the top cover, and the laser welding process is used to complete the welding of the adapter according to the welding speed, power and defocus parameters required by the process to obtain the fourth battery cell.

9. A lithium ion battery, characterized in that: The method is obtained by the manufacturing method according to any one of claims 1 to 8.