New energy battery aluminum foil surface treatment equipment based on coating spraying composite structure

Abstract

The invention relates to the technical field of coating devices, and discloses new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure, the new energy battery aluminum foil surface treatment equipment comprises an upper die head and a lower die head which are symmetrically arranged up and down, baffles are arranged on the two sides of the upper die head and the lower die head, and a gasket is arranged in a gap between the upper die head and the lower die head; the ends, away from the gasket, of the upper die head and the lower die head are fixedly connected with a discharging plate. The upper die head, the lower die head and the gasket jointly define a runner, the gasket comprises a blocking piece, and the other end of the blocking piece is fixedly connected with a guide plate. The mold is provided with the flow channel, the unstable elastic recovery and free flow of slurry after mold stripping are core reasons for causing coating stripes, edge defects and bubbles, the flow channel is defined by a blocking piece of a gasket, a guide plate, a first inclined plate, a second inclined plate, an upper mold head and a lower mold head, the flow channel is divided into two sections of a shearing cavity and a relaxation cavity, and through continuous control of pre-shearing-stress relaxation, the thickness of the flow channel is smaller than that of the flow channel, and the thickness of the flow channel is smaller than that of the flow channel. And elastic recovery is inhibited fundamentally.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating devices, in particular to a new energy battery aluminum foil surface treatment equipment based on coating spraying composite structure. BACKGROUND

[0002] The core purpose of new energy battery aluminum foil surface treatment is to convert the rolled base aluminum foil into a current collector that meets the stringent requirements of high-performance batteries. The key functional coating (such as carbon coating) spraying is to build a multifunctional film on this clean substrate, the main purpose of which is to greatly improve the electrical conductivity of the aluminum foil, reduce the interface resistance, and thus improve the rate performance and energy efficiency of the battery; the lithium battery slurry has significant viscoelasticity due to the presence of PVDF, SBR and other binders, and during the slot coating process, this characteristic can cause a series of flow stability problems. When the slurry flows in the die cavity 15, it will produce elastic deformation under the action of wall shear, and when it leaves the die, the constraint is suddenly released, and the elastic deformation will quickly recover (i.e. "elastic recovery"), causing a slight fluctuation in the flow direction of the slurry. If the slurry is too elastic, "necking" (cross-sectional contraction) or periodic fluctuations will occur during the recovery process, which will further cause local fluid rotation and form eddies.

[0003] During the "free flow stage" of the slurry from the die outlet to the contact with the substrate, the inherently unstable viscoelastic flow is more easily coupled with external disturbances (such as small air currents, substrate speed fluctuations), which exacerbates the eddy and flutter phenomena, which are manifested as follows: the flutter causes the slurry to form alternating thick and thin periodic stripes when it comes into contact with the substrate; the eddy or air flow disturbance causes the edges of the coating to be jagged or wavy, which requires additional cutting and causes waste of the substrate; air entrained by the eddy can form small air bubbles that remain in the coating and become pinholes after compaction; these defects not only reduce the uniformity of the coating, but also cause uneven distribution of internal resistance in the battery electrode and poor charge-discharge consistency, which can cause local overheating during long-term use and threaten the safety performance of the battery. SUMMARY

[0004] Technical problems to be solved

[0005] To solve the above-mentioned shortcomings of the prior art, the present application provides a new energy battery aluminum foil surface treatment equipment based on coating spraying composite structure, which can effectively solve the problem of slurry viscoelastic flow in the prior art, and the problem of coating defects and substrate waste.

[0006] To achieve the above-mentioned purposes, the present application is implemented by the following technical solutions:

[0007] The present application provides a new energy battery aluminum foil surface treatment equipment based on coating spraying composite structure, comprising: a coating roller, the coating roller is provided with a slot coating head at the side, the slot coating head performs coating on the aluminum foil transmitted on the surface of the coating roller;

[0008] The slit coating head comprises an upper die head and a lower die head symmetrically arranged, both sides of the upper die head and the lower die head are provided with baffles, a gap between the upper die head and the lower die head is provided with a gasket, and one end of the upper die head and the lower die head away from the gasket is fixedly connected with a discharge plate; the upper die head, the lower die head and the gasket jointly enclose a flow channel, and the gasket comprises a baffle, and the other end of the baffle is fixedly connected with a guide plate.

[0009] The lower die head is provided with a die cavity with uniform slurry rate in the middle of the top end.

[0010] Further, the die cavity comprises a distribution cavity I located at the bottom, the upper end of the distribution cavity I is provided with a distribution cavity II, the upper surface of the distribution cavity II is provided with a clamping block, and the inner clamping block of the clamping block is connected with a flow uniformizing plate.

[0011] Further, the bottom end side of the flow uniformizing plate is designed in an arc shape, the upper end of the distribution cavity II is attached to the arc-shaped edge of the flow uniformizing plate, and the four sides of the flow uniformizing plate are provided with sealing strips for filling gaps.

[0012] Further, the inner walls of the distribution cavity I and the distribution cavity II are designed in an arc shape, and the distribution cavity I and the distribution cavity II are placed in a stepped manner.

[0013] Further, the upper surface of the flow uniformizing plate is flush with the upper surface of the lower die head, and the flow uniformizing plate is designed with a plurality of honeycomb holes.

[0014] Further, the inner wall of the baffle is provided with an inclined plate I, the inclined plate I is designed to be inclined from top to bottom, the side edge of the guide plate is provided with an inclined plate II, and the inclined plate II is designed to be inclined from inside to outside.

[0015] Further, the flow channel comprises a shearing cavity surrounded by the inclined plate I, the side edge of the shearing cavity is provided with a relaxation cavity surrounded by the inclined plate II, and the side edge of the relaxation cavity is provided with a flow uniformizing port.

[0016] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0017] The flow channel is provided to solve the problems of elastic recovery and unstable free flow, and the elastic recovery and unstable free flow after the slurry is discharged from the die are the core reasons for causing coating stripes, edge defects and bubbles. The flow channel is jointly surrounded by the baffle, the guide plate, the inclined plate I, the inclined plate II and the upper die head and the lower die head, and is divided into two sections of "shearing cavity" and "relaxation cavity". Through the continuous control of "pre-shearing-stress relaxation", the elastic recovery is fundamentally inhibited.

[0018] The present application is provided with a relaxation cavity, firstly, the length of the relaxation cavity is short, the passing time of the slurry is much smaller than the characteristic time of particle sedimentation, and the particle sedimentation problem caused by the traditional long cavity is completely avoided; secondly, the relaxation cavity is still in the wall constraint of the upper die head, the lower die head and the inclined plate two, and the slurry cannot expand freely, and the elastic recovery is limited in the "controllable range"; in the traditional structure, the slurry is easy to form vortex due to uneven elastic recovery when relaxing freely without constraint; and in the present application, the wall constraint makes the elastic recovery of the slurry smooth along the inner wall of the cavity, and local rotation does not occur, effectively inhibiting the generation of vortex.

[0019] The present application is provided with a mold cavity, the primary diffusion of the distribution cavity one changes the slurry flow field from "severe fluctuation" to "smooth and stable", and the subsequent flow channel does not need to deal with large flow rate difference again, reducing the difficulty of homogenization; at the same time, the arc inner wall has no dead zone, avoiding the slurry from being left in the corner and dried, and reducing the "impurity point" defects; the distribution cavity two is located at the upper end of the distribution cavity one, and its structure design forms "complementary cooperation" with the distribution cavity one, the inner wall of the cavity is an arc with a smaller radius, which is used to enhance the guiding property, the cross-sectional size gradually changes from the inlet end (connected with the distribution cavity one) to the outlet end (connected with the flow distribution plate), the cross-sectional area decreases, and the change rate is further reduced, realizing "more gentle diffusion". BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, below the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0021] Figure 1 It is a whole structure schematic diagram of the embodiment of the present application;

[0022] Figure 2 It is a structure schematic diagram of the slit coating head of the embodiment of the present application;

[0023] Figure 3 It is a structure schematic diagram of the slit coating head of the embodiment of the present application;

[0024] Figure 4 It is a structure schematic diagram of the mold cavity of the embodiment of the present application;

[0025] Figure 5 It is a structure schematic diagram of the connection between the lower die head and the gasket of the embodiment of the present application;

[0026] Figure 6 It is a structure schematic diagram of the gasket of the embodiment of the present application;

[0027] Figure 7 It is a structure schematic diagram of the flow channel of the embodiment of the present application.

[0028] The reference signs in the figures respectively represent: 1, slit coating head; 11, upper die head; 12, lower die head; 13, gasket; 131, baffle; 132, guide plate; 133, inclined plate one; 134, inclined plate two; 14, baffle plate; 15, die cavity; 151, distribution cavity one; 152, distribution cavity two; 153, clamping block; 16, flow equalizing plate; 17, discharge plate; 18, flow channel; 181, shearing cavity; 182, relaxation cavity; 183, flow equalizing port; 2, coating roller. DETAILED DESCRIPTION

[0029] To make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings of the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0030] The present application will be further described in conjunction with the embodiments.

[0031] Embodiment:

[0032] Please refer to Figures 1-7 The present application provides a new energy battery aluminum foil surface treatment equipment technical scheme based on a coating spraying composite structure:

[0033] Reference Figure 1 and Figure 2 The equipment includes a coating roller 2, and a slit coating head 1 is arranged at the side of the coating roller 2, and the slit coating head 1 coats paint on the aluminum foil transmitted on the surface of the coating roller 2.

[0034] In actual slit coating operation of a lithium battery pole piece, when the pseudoplastic slurry flows in the die cavity 15 of the slit coating head, a significant shear rate gradient is formed due to wall friction; the shear rate is high, the viscosity is low, and the flow rate is fast at the wall surface, and the shear is weak, the viscosity is high, and the flow rate is slow in the central region, and the flow rate difference between the two can reach 2-5 times. This uneven flow rate causes the residence time of the slurry in the die cavity 15 to be unbalanced, and the particles in the central region are more prone to sedimentation due to slow flow rate and gravity, forming a concentration gradient of “thick in the center and thin at the edge”; the agglomerates of particles that are not fully dispersed also accumulate in the low flow rate area, and even block the local slits. Ultimately, the coating thickness and area density are out of tolerance, the internal particle distribution is uneven, and the battery capacity consistency is poor, the internal resistance is increased, and the risk of thermal runaway is caused.

[0035] Reference Figure 2 and Figure 3The slot coating head 1 comprises an upper die head 11 and a lower die head 12 symmetrically arranged, the upper die head 11 and the lower die head 12 are provided with baffles 14 on both sides, the gap between the upper die head 11 and the lower die head 12 is provided with a gasket 13, and the end of the upper die head 11 and the lower die head 12 away from the gasket 13 is fixedly connected with a discharge plate 17, and the upper die head 11, the lower die head 12 and the gasket 13 jointly enclose a flow channel 18;

[0036] The die cavity 15 of the lower die head 12 is a “primary flow field regulation area”, which solves the flow velocity gradient problem at the inlet end of the slurry; the flow uniformizing plate 16 is a “secondary homogenizing area”, which breaks the agglomerates and further flattens the flow field; the flow channel 18 surrounded by the gasket 13 and the upper die head 11 and the lower die head 12 is a “tertiary viscoelastic control area”, which realizes pre-shearing and stress relaxation; and finally the stable outflow is realized through the discharge plate 17, so as to ensure that the slurry forms a uniform liquid curtain in the free flow stage;

[0037] The inner walls of the upper die head 11 and the lower die head 12 are mirror polished to reduce the friction resistance of the slurry flow; the two side baffles 14 are made of polytetrafluoroethylene material and are fixed with the upper die head 11 and the lower die head 12 through bolts, which can effectively prevent the slurry from overflowing from the side of the flow channel 18 and ensure the sealing of the flow channel 18; the gasket 13 is made of solvent-resistant fluororubber material, and its special inclined plate structure directly determines the shape of the flow channel 18, and the outlet end is a rounded corner to avoid disturbance caused by edge burrs when the slurry flows out.

[0038] Reference Figure 3 And Figure 4 The top middle part of the lower die head 12 is provided with a die cavity 15 for uniformly distributing the slurry, the die cavity 15 comprises a distribution cavity one 151 located at the bottom, a distribution cavity two 152 is arranged at the upper end of the distribution cavity one 151, a clamping block 153 is arranged on the upper surface of the distribution cavity two 152, and a flow uniformizing plate 16 is clamped and connected in the clamping block 153;

[0039] The traditional coating head usually adopts a T-shaped or clothes hanger-shaped distribution cavity, and after the slurry enters, vortex and dead zone are easily formed due to the sudden change of the cross section of the flow channel 18, and the uneven flow velocity is aggravated. In the scheme, the die cavity 15 at the top middle part of the lower die head 12 adopts a “stepped arc gradual change structure” composed of the distribution cavity one 151, the distribution cavity two 152 and the clamping block 153, and the gradual transition of the slurry flow velocity is realized through two-stage diffusion, so as to reduce the shear rate gradient from the source.

[0040] The distribution cavity one 151 is the bottom cavity of the die cavity 15, and the design core is “arc-shaped inner wall + gradually changing cross section”; the inner wall of the cavity adopts arc transition (instead of the traditional right-angle inner wall), so as to avoid the formation of vortex when the slurry flows due to sudden turning; the cross-sectional size gradually changes from the inlet end (connected with the main distribution cavity) to the outlet end (connected with the distribution cavity two 152).

[0041] When the slurry enters the distribution cavity one 151 from the main distribution cavity (i.e. the external feeding system), the arc-shaped inner wall guides the slurry to flow smoothly along the wall, avoiding the "wall slurry impact rebound" phenomenon caused by the traditional right-angle inner wall. At the same time, the design of the gradually changing cross-section makes the slurry experience "slow decompression-uniform diffusion" during the flow process; the high-flow-rate slurry near the wall in the main distribution cavity gradually reduces in flow rate due to the increase in cross-sectional width and the decrease in height; while the low-flow-rate slurry in the center region slightly accelerates under the guidance of the gradually changing cross-section. During this process, the wall-center flow rate difference of the slurry is reduced from the initial 2-5 times to 1.5-2 times, effectively alleviating the "residence time imbalance" problem-the residence time of the slurry in the center region is shortened, and the difference with the wall region is controlled within a short time, laying a foundation for subsequent particle settling control.

[0042] The primary diffusion of the distribution cavity one 151 changes the slurry flow field from "severe fluctuation" to "gentle and stable", and the subsequent flow channel 18 no longer needs to deal with large flow rate differences, reducing the difficulty of homogenization; at the same time, the arc-shaped inner wall has no dead zone, avoiding the slurry from being left to dry in the corner and reducing "impurity point" defects.

[0043] The distribution cavity two 152 is located at the upper end of the distribution cavity one 151, and its structure design is "complementary and cooperative" with that of the distribution cavity one 151. The inner wall of the cavity is an arc with a smaller radius, used to enhance the guidance, and the cross-sectional size gradually changes from the inlet end (connected with the distribution cavity one 151) to the outlet end (connected with the flow uniformizing plate 16), the cross-sectional area decreases, and the change rate further decreases, realizing "more gentle diffusion".

[0044] The clamping block 153 is a protruding structure on the upper surface of the distribution cavity two 152, which is integrally processed and formed, and the inner side is provided with a clamping groove with a depth for clamping and fixing the flow uniformizing plate 16. The design of the clamping block 153 has two functions; one is to ensure that the flow uniformizing plate 16 is completely matched with the outlet of the distribution cavity two 152 through the precise positioning of the clamping groove, avoiding the leakage of slurry from the gap; the other is to limit the installation position of the flow uniformizing plate 16 through the height of the flange, so that the upper surface of the flow uniformizing plate 16 is flush with the upper surface of the lower mold head 12, ensuring the uniform height of the subsequent flow channel 18.

[0045] After the primary diffusion of the slurry in the distribution cavity one 151, the slurry enters the distribution cavity two 152 and is further guided by the arc-shaped inner wall with a smaller radius, realizing further flow rate homogenization. At this time, the flow rate in the wall region decreases, the flow rate in the center region increases, and the flow rate difference decreases, basically eliminating the extreme difference of "fast on the wall and slow in the center". At the same time, the gentle diffusion of the distribution cavity two 152 makes the slurry form a "laterally uniform distribution" flow field before entering the flow uniformizing plate 16-the flow rate fluctuation along the width direction of the distribution cavity is controlled within ±5%, avoiding the lateral unevenness problem of "low edge flow rate and high middle flow rate" in the traditional structure.

[0046] The stability of the slurry flow field after secondary diffusion is significantly improved, providing a "uniform initial condition" for the subsequent homogenization of the flow plate 16; the precise positioning of the clamping block 153 ensures the installation accuracy of the flow plate 16, avoiding local flow rate abnormalities caused by installation deviations, and reducing the transverse surface density difference of the coating.

[0047] The bottom side of the flow plate 16 is designed with an arc shape, and the upper end of the distribution cavity two 152 is in contact with the arc-shaped edge of the flow plate 16. The flow plate 16 is provided with sealing strips to fill the gaps on the four sides. The inner walls of the distribution cavity one 151 and the distribution cavity two 152 are designed with an arc shape, and the distribution cavity one 151 and the distribution cavity two 152 are placed in a stepped manner. The upper surface of the flow plate 16 is flush with the upper surface of the lower die head 12. The flow plate 16 is designed with multiple honeycomb holes.

[0048] The flow plate 16 is designed with multiple honeycomb holes, and the arrangement of the honeycomb holes adopts a regular hexagonal array to ensure uniform distribution of the holes along the width direction of the flow channel 18, without local dense or sparse areas. The bottom side of the flow plate 16 (the end in contact with the distribution cavity two 152) is processed into an arc shape, which is completely in contact with the arc-shaped edge of the upper surface of the distribution cavity two 152, avoiding the formation of step dead zones.

[0049] The four sides of the flow plate 16 are pasted with fluororubber sealing strips, which are in close contact with the inner walls of the clamping groove of the clamping block 153, further enhancing the sealing performance and preventing slurry leakage.

[0050] When the slurry that has undergone secondary diffusion in the distribution cavity two 152 flows to the flow plate 16, it will be divided into countless streams by the honeycomb holes. During this process, two key actions occur. When the slurry stream passes through the honeycomb hole, it will be subjected to uniform shear force from the hole wall. This shear force can effectively break up large micro-agglomerates. In lithium battery slurry, common agglomerates (such as active material particles and conductive agent agglomerates) are broken down into individual particles under the action of shear force, and the agglomerates are dispersed into individual particles along with the slurry stream.

[0051] The damping effect of the honeycomb holes further flattens the flow field when the slurry passes through. Even if there is still a small local flow rate difference after secondary diffusion, it will be eliminated under the damping effect of the honeycomb holes. The flow rate in the area with high flow rate will slightly decrease due to the large resistance of the hole channel, while the flow rate in the area with low flow rate will remain stable due to consistent resistance, ultimately controlling the flow rate difference of all streams within ±3%. At the same time, the uniform distribution of the honeycomb holes ensures consistent slurry flow along the width direction of the flow channel 18, avoiding "local concentration" (such as high particle density in the center area and low particle density at the edges), and forming a "macro-uniform, micro-dispersed" slurry state.

[0052] The design of the flow equalizing plate 16 directly solves the problems of particle agglomeration and local concentration. After passing through the flow equalizing plate 16, the content of agglomerates in the slurry is reduced, and there are no large agglomerates with a diameter greater than 5 μm, the frequency of slit blockage is reduced, and the cleaning time is reduced. The uniformity of particle distribution in the coating is significantly improved. The cooperation of the arc-shaped bottom end and the sealing strip avoids slurry leakage, reduces slurry waste, and reduces production cost.

[0053] With reference to Figure 5 , Figure 6 and Figure 7 , the gasket 13 includes a baffle 131, the other end of the baffle 131 is fixedly connected with a guide plate 132, an inclined plate one 133 is arranged on the inner wall of the baffle 131, the inclined plate one 133 is designed to be inclined from top to bottom, an inclined plate two 134 is arranged on the side edge of the guide plate 132, the inclined plate two 134 is designed to be inclined from inside to outside, the flow channel 18 includes a shearing cavity 181 surrounded by the inclined plate one 133, the shearing cavity 181 is provided with a relaxation cavity 182 surrounded by the inclined plate two 134 on the side edge, and the relaxation cavity 182 is provided with a flow equalizing port 183 on the side edge.

[0054] The conventional coating head lacks a targeted agglomerate breaking structure and only relies on pre-dispersion treatment of the slurry. Once the pre-dispersion is insufficient, the agglomerates are easy to accumulate and block the slit in the mold cavity 15. In the present scheme, the flow equalizing plate 16 adopts a composite design of "honeycomb hole + arc-shaped bottom end", which has the dual functions of "damping flow equalization" and "shearing breaking", and is the core component for solving the problems of particle agglomeration and local concentration.

[0055] The design of the flow channel 18 solves the problems of elastic recovery and unstable free flow after the slurry is discharged from the mold. The elastic recovery and unstable free flow after the slurry is discharged from the mold are the core reasons for causing coating stripes, edge defects and bubbles. In the present scheme, the flow channel 18 is surrounded by the baffle 131, the guide plate 132, the inclined plate one 133, the inclined plate two 134 of the gasket 13 and the upper die head 11 and the lower die head 12, and is divided into two sections of "shearing cavity 181" and "relaxation cavity 182". Through the continuous control of "pre-shearing-stress relaxation", the elastic recovery is fundamentally inhibited.

[0056] The inner side section (close to the flow equalization plate 16 end) of the gasket 13 has a length of 5 mm, and the inner wall is provided with an inclined plate one 133. The inclined plate one 133 is inclined from top to bottom to form a “wedge-shaped” shearing cavity 181 with the lower surface of the upper die head 11, and the height of the cavity gradually changes from 1 mm at the inlet end (connected with the flow equalization plate 16) to 0.8 mm at the outlet end (connected with the relaxation cavity 182); the outer side section (close to the discharge plate 17 end) of the gasket 13 is provided with an inclined plate two 134 on the side. The inclined plate two 134 is inclined from inside to outside to form a “flared” relaxation cavity 182 with the lower surface of the upper die head 11, and the height of the cavity gradually changes from 0.8 mm at the inlet end to 1 mm at the outlet end (flow equalization port 183); the outlet end of the relaxation cavity 182 has a width consistent with the flow channel 18 and is aligned with the outlet of the discharge plate 17, which is the “last stable section” of the slurry entering the free flow stage.

[0057] The slurry homogenized by the flow equalization plate 16 enters the shearing cavity 181 and flows along the inner wall of the wedge-shaped cavity under the inclined guide of the inclined plate one 133. At this time, the slurry is subjected to three-dimensional extrusion by the “upper die head 11, lower die head 12 wall + inclined plate one 133”, forming a uniform pre-shearing and best matching with the optimal shearing interval of lithium battery slurry. The core function of this pre-shearing is to “unify the shearing history of the slurry”; in the traditional structure, the shearing history of the slurry is greatly different before entering the final slit (part of the area does not experience sufficient shearing, and part of the area is over-sheared), resulting in inconsistent elastic recovery after discharge; the pre-shearing of the shearing cavity 181 makes all the slurry experience “the same intensity and the same length” of shearing before entering the relaxation cavity 182, and the viscoelastic deformation tends to be uniform, avoiding random elastic recovery during subsequent discharge.

[0058] At the same time, during the pre-shearing process, the viscosity of the slurry decreases due to the shear thinning characteristics (pseudoplasticity), the fluidity increases, and the viscosity distribution is uniform (the viscosity fluctuation along the cross section of the flow channel 18 is ≤±5%), further reducing the flow velocity fluctuation during discharge.

[0059] The consistency of the viscoelastic behavior of the pre-sheared slurry is significantly improved, and the amplitude of the elastic recovery after discharge is reduced; the liquid curtain stability in the free flow stage is enhanced, the flutter frequency is reduced, and the periodic stripe defects are basically eliminated.

[0060] Stress release inhibits necking and vortex; after pre-shearing, the slurry enters the relaxation cavity 182, and the flared design reduces the flow pressure of the slurry, and the elastic stress accumulated during the pre-shearing process is quickly relaxed here.

[0061] Compared with the traditional open type, the relaxation cavity 182 has two advantages, first, the length of the relaxation cavity 182 is shorter, and the slurry passing time is much smaller than the characteristic time of particle sedimentation, which completely avoids the particle sedimentation problem caused by the traditional long cavity; second, the relaxation cavity 182 is still in the wall constraint of the upper die head 11, the lower die head 12 and the inclined plate two 134, and the slurry cannot freely expand, and the elastic recovery is limited in the "controllable range"; in the traditional structure, the slurry is easy to form vortex due to uneven elastic recovery when it freely relaxes without constraint; and in the present scheme, the wall constraint makes the elastic recovery of the slurry smooth along the inner wall of the cavity, and local rotation does not occur, effectively inhibiting the generation of vortex.

[0062] In addition, the inclined design of the inclined plate two 134 guides the slurry to flow smoothly along the "flared direction", avoiding the sudden turning of the slurry at the outlet end, further stabilizing the outflow form. When the slurry flows out from the flow uniformizing port 183, a "cross-section uniform and undulating" liquid curtain has been formed, and the liquid curtain width is completely matched with the aluminum foil width, and there is no jagged deformation at the edge.

[0063] The stress release of the relaxation cavity 182 greatly improves the stability of the slurry outflow form, reduces the cutting loss of the edge jagged defect of the coating, reduces the amount of air entrained by the vortex, and reduces the pinhole density and the battery charge-discharge consistency (capacity difference).

[0064] The core advantage of the present device is the "seamless cooperation" of each structure, and the flow path and control logic of the slurry in the slit coating head 1 are as follows; main distribution cavity feeding→distribution cavity one 151 (primary diffusion, flow rate difference reduction), solving the initial flow rate gradient problem; distribution cavity one 151→distribution cavity two 152 (secondary diffusion), realizing uniform horizontal flow field; distribution cavity two 152→flow uniformizing plate 16 (honeycomb hole shearing, agglomerate crushing plus flow uniformizing, flow rate fluctuation), solving the problems of particle agglomeration and local concentration;

[0065] Flow uniformizing plate 16→shearing cavity 181 (pre-shearing, uniform viscoelastic deformation), inhibiting the elastic recovery of the die; shearing cavity 181→relaxation cavity 182 (stress release, inhibiting vortex and sedimentation, liquid curtain stabilization), stabilizing the free flow stage; relaxation cavity 182→flow uniformizing port 183→discharge plate 17 (outflow forming, uniform coating); finally forming a high-quality coating.

[0066] In this process, the symmetrical structure of the upper die head 11 and the lower die head 12 ensures the uniformity of the flow channel 18, the sealing effect of the baffle 14 avoids slurry leakage, and the round corner design of the discharge plate 17 eliminates outflow disturbance, and all components cooperatively form a "fully controllable" coating system.

[0067] Through the above structure optimization, the device completely solves the four core technical problems of lithium battery pole piece slot coating, solves the coating area density overproof problem, reduces the area density CV value, reduces the thickness tolerance, and meets the pole piece precision requirements of high energy density batteries (such as ternary lithium batteries, iron lithium phosphate batteries);

[0068] Solve the problem of slot blockage and low production efficiency, improve the breaking rate of agglomerates, reduce the frequency of slot blockage, improve the OEE of the equipment, and increase the annual production capacity; solve the problem of coating appearance defects, reduce the periodic stripe rate, reduce the edge cutting loss, reduce the density of pinholes, and improve the yield of the coating; solve the problem of battery performance consistency and safety, improve the uniformity of the internal particles of the pole piece, reduce the battery resistance fluctuation, reduce the charge and discharge capacity difference, and reduce the risk of thermal runaway.

[0069] At the same time, the scheme adopts pure mechanical structure optimization, does not increase any pre-drive or complex electronic elements (such as sensors, servo motors), reduces the maintenance cost of the equipment, and has higher tolerance to slurry batch fluctuations (solid content fluctuation ±1%, viscosity fluctuation ±10% can stably produce), the process window is significantly widened, and it is more suitable for the needs of large-scale industrial production.

[0070] Through the integrated design of the "stepped arc-shaped die cavity 15-honeycomb hole flow uniform plate 16-wedge-shaped shearing cavity 181-flared relaxation cavity 182" of the slot coating head 1, the core problems of uneven flow rate, particle agglomeration, and elastic recovery of pseudoplastic slurry are solved from the physical level. The innovation lies in solving the uneven flow field by "staged diffusion", breaking the agglomerates by "honeycomb shearing", and controlling the viscoelasticity by "pre-shearing-constrained relaxation". All optimizations are achieved through mechanical structure without relying on external electronic control. Finally, the coating area density CV value is reduced, the yield is improved, and the OEE of the equipment is improved, providing a reliable industrial solution for the precision coating of lithium battery pole pieces.

[0071] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the protection scope of the technical solutions of the embodiments of the present application.

Claims

1. A new energy battery aluminum foil surface treatment equipment based on coating spraying composite structure, characterized in that, The application relates to a coating roller (2) provided with a slit coating head (1) on the side, which is used for coating the aluminum foil transmitted on the surface of the coating roller (2). The slit coating head (1) comprises upper and lower die heads (11) and (12) which are symmetrically arranged, the upper and lower die heads (11) and (12) are provided with baffle plates (14) on the two sides, a gasket (13) is arranged in the gap between the upper and lower die heads (11) and (12), and discharge plates (17) are fixedly connected to the ends of the upper and lower die heads (11) and (12) away from the gasket (13); the upper and lower die heads (11) and (12) and the gasket (13) jointly form a flow channel (18), and the gasket (13) comprises a baffle (131) and a guide plate (132) fixedly connected to the other end of the baffle (131). The lower die head (12) is provided with a die cavity (15) with a uniform slurry rate at the middle of the top end. The die cavity (15) comprises a distribution cavity I (151) at the bottom, the distribution cavity I (151) is provided with a distribution cavity II (152) at the upper end, the upper surface of the distribution cavity II (152) is provided with a clamping block (153), and the clamping block (153) is internally clamped and connected with a flow uniformizing plate (16).

2. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 1, characterized in that: The bottom end side of the flow uniformizing plate (16) is designed in an arc shape, the upper end of the distribution cavity II (152) is attached to the arc-shaped edge of the flow uniformizing plate (16), and the flow uniformizing plate (16) is provided with sealing strips for filling the gaps on the four sides.

3. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 2, characterized in that: The inner walls of the distribution cavity I (151) and the distribution cavity II (152) are designed in arc shapes, and the distribution cavity I (151) and the distribution cavity II (152) are arranged in a stepped manner.

4. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 2, characterized in that: The upper surface of the flow uniformizing plate (16) is flush with the upper surface of the lower die head (12), and the flow uniformizing plate (16) is designed in a plurality of honeycomb holes.

5. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 3, characterized in that: The inner wall of the baffle (131) is provided with an inclined plate I (133) which is designed to be inclined from top to bottom, and the side of the guide plate (132) is provided with an inclined plate II (134) which is designed to be inclined from inside to outside.

6. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 1, characterized in that: The flow channel (18) comprises a shearing cavity (181) surrounded by the inclined plate I (133), the shearing cavity (181) is provided with a relaxation cavity (182) surrounded by the inclined plate II (134) on the side, and the relaxation cavity (182) is provided with a flow uniformizing port (183) on the side.

7. The new energy battery aluminum foil surface treatment equipment based on a coating spraying composite structure according to claim 1, characterized in that: ​

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