Battery three-dimensional interlayer diaphragm structure with graded liquid retention capacity

[0024] In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] See Figure 1 to Figure 4 , The present invention provides a three-dimensional battery sandwich diaphragm structure with hierarchical liquid retention capability, including a front surface layer base film 11 and a back surface layer base film 12 distributed at intervals between front and rear;

[0026] In the cavity between the front surface layer base film 11 and the back surface layer base film 12, a plurality of laterally distributed liquid storage interlayers 2 are sequentially spaced from top to bottom;

[0027] The liquid storage interlayer 2 is used to divide the cavity between the front surface layer base film 11 and the back surface layer base film 12 into a plurality of independent liquid storage channels (ie, multi-level electrolyte storage channels and cavities);

[0028] Each liquid storage interlayer 2 includes a plurality of interlayer monomers 4 connected together in sequence;

[0029] The interlayer monomer 4 is a groove structure with an upward opening (bottom seal);

[0030] At the junction between any two adjacent interlayer monomers 4, an interconnecting hole 3 that penetrates vertically up and down is opened.

[0031] In the present invention, in terms of specific implementation, a plurality of liquid storage interlayers 2 are distributed at equal intervals in the cavity between the front surface layer base film 11 and the back surface layer base film 12.

[0032] In the present invention, in terms of specific implementation, the sandwich monomer 4 is preferably a V-shaped or concave-shaped structure with an upward opening, but it is not limited to this shape.

[0033] In the present invention, in terms of specific implementation, the liquid storage interlayer 2 exists between the two base film plane layers (ie, the front surface layer base film 11 and the back surface layer base film 12), and they are combined together by glue.

[0034] In the present invention, the thickness of the base film 11 of the front surface layer and the base film 12 of the rear surface layer is 2-50um.

[0035] In the present invention, in terms of specific implementation, the depth and width of the channel connecting the interconnecting holes 3 in the liquid storage interlayer 2 can be flexibly designed according to the amount of liquid injected, and the size range is all included in the protection scope of this patent.

[0036] It should be noted that, for the present invention, after the electrolyte is injected, it will be retained in stages in the multi-level liquid storage channels of the diaphragm structure of the battery cell in different height directions. And there are certain interconnected holes between the multilayer channels, but it does not affect the long-term storage of electrolyte in the channels.

[0037] In the present invention, the material of the base film 11 of the front surface layer and the base film 12 of the rear surface layer can be made of polyolefin materials, prepared by the existing dry method or wet method, and can adopt the mature technology of the prior art. Battery separator base film.

[0038] In the present invention, the liquid storage interlayer 2 located between the front surface layer base film 11 and the rear surface layer base film 12 is a three-dimensional structure made of PVDF (polyvinylidene fluoride) glue (but not limited to PVDF substances, all materials that can meet the design structure are within the protection range), the size of the PVDF raw material powder is nanometer, the amorphous region is maintained in the range of 10-40%, and the weight ratio is 20%-67%. The nanometer-level PVDF powder is dissolved in NMP (N-methylpyrrolidone) or DMF (dimethylformamide) or betaine BS-12 emulsion. The heating temperature is above 30℃ and the stirring time is 30min to fully dissolve the nanometer grade. PVDF, until the glue viscosity is 2000~7000/cp.

[0039] In the present invention, in terms of specific implementation, the specific preparation process of the battery three-dimensional sandwich separator structure of the present invention is as follows: First, according to the settings, on the surface of the polyolefin rear surface layer base film 12, through a mold injection method (existing ) To form a preliminary composite of a continuous interlayer (ie, multiple liquid storage interlayers 2) and the base film 12 of the back surface layer to obtain a preliminary composite, in which two V-shaped interlayer monomers 4 are left with small gaps (interconnecting holes 3). ) To ensure that the electrolyte can be transferred between the multilayer liquid storage channels when the electrolyte is injected; subsequently, the front surface layer base film 11 is covered on the front surface of the liquid storage interlayer 2, and the thermal temperature is controlled to 50-120°C, The preliminary composite body is bonded to the front surface layer base film 11 to finally form a three-dimensional battery sandwich diaphragm structure.

[0040] It should be noted that for the liquid storage interlayer 2, the colloid used should not be limited to the PVDF glue, including the scope extended to any material that can form the original shape. The method protection is not limited to the above methods, and should include any method for preparing the sandwich structure.

[0041] It should be noted that the front surface layer base film 11 and the back surface layer base film 12 are both planar layers, which have a two-layer planar structure, and the liquid storage interlayer in the middle is a three-dimensional V-shaped channel. The base membrane plane layer and the liquid storage interlayer are controllably assembled into a three-dimensional interlayer structure. This three-dimensional structure can achieve controllable grading by adjusting the size of the sandwich structure and the interlayer density to store the electro-hydraulic in different interlayer channels, matching the needs of different pole piece positions for the electrolyte, improving the liquid retention capacity of the diaphragm, and accelerating The reaction speed of the ions in the electrolyte is improved, which improves the rate performance of the battery. At the same time, this structure also avoids the uneven distribution of electrolyte in the electrode group caused by uneven tension, solves the phenomenon of lithium evolution caused by this, and improves the safety performance of the battery. In addition, through the multi-level and designability of the channel distribution, the present invention can realize the effect of the controllable and hierarchical distribution of the electrolyte according to the difference of the coating amount at different positions of the pole piece. None of the current diaphragm materials have this structure.

[0042] In order to make the technical solution of the present invention clearer, the following description will be given in conjunction with specific embodiments.

[0043] See Figure 1 to Figure 4 As shown, a battery three-dimensional sandwich diaphragm structure with hierarchical liquid retention capacity of the present invention includes a surface layer and a sandwich body (that is, a front surface layer base film 11, a rear surface layer base film 12, and a liquid storage interlayer). The liquid interlayer 2 has a V shape and can store electro-hydraulic in the tunnel.

[0044] The base film 11 of the front surface layer and the base film 12 of the rear surface layer are made of polyolefin material and are prepared by dry stretching; the liquid storage interlayer in the middle is a three-dimensional structure of PVDF glue, and the size of the PVDF raw material powder is nanometer and amorphous Zone retention range 22%, dissolve nanometer PVDF in NMP or water-based solvent, heating temperature 50℃, stirring time 60min, fully dissolve nanometer PVDF, until the glue reaches a viscosity of 5600cp. According to the setting, on the height direction surface (ie the front side) of the back surface layer base film 12, through the injection molding method, a preliminary composite of the multilayer sandwich body and the back surface layer base film is formed. Small gaps to ensure the transfer between multiple layers when electrolyte is injected. Subsequently, the front surface of the interlayer is covered with a base film of the front surface layer, and the heat temperature is controlled to 60° C. to bond the preliminary composite with the base film of the front surface layer to form the three-dimensional sandwich structure.

[0045] For the present invention, according to the difference in the distribution of the coating amount of the pole pieces, the upper side of the height direction of the battery is designed, the pore level is slightly sparse, and the electrolyte retained slightly. In the same way, the pores on the lower side are dense and can store a lot of electrolyte.

[0046] Compared with the prior art, the three-dimensional battery sandwich diaphragm structure with hierarchical liquid retention capability provided by the present invention has the following beneficial effects:

[0047] 1. The three-dimensional sandwich diaphragm structure of the battery of the present invention can avoid the disadvantages of the electrolyte concentration gradient distribution caused by the vertical placement of the battery. Its unique liquid retention structure can make the lithium ions in the electrolyte start quickly and improve the battery's electricity performance.

[0048] 2. The three-dimensional sandwich diaphragm structure of the battery of the present invention can effectively infiltrate the electrolyte, avoiding the lithium evolution caused by the lack of electrolyte in some areas, and greatly reducing the safety risk of the battery.

[0049] 3. The three-dimensional sandwich diaphragm structure of the battery of the present invention can keep the electrolyte in different areas of the battery height. The position, depth and density of the grading channel can be controlled and customized to achieve the difference between the coating amount of the pole piece and the amount of electrolyte. Matching avoids waste of electrolyte and safety problems caused by lack of electrolyte.

[0050] 4. In the three-dimensional sandwich diaphragm structure of the battery of the present invention, the nano-scale PVDF particles used in the sandwich structure can achieve effective retention of electrolyte. At the same time, the sandwich structure can reduce the risk of diaphragm contraction due to temperature rise to a certain extent, and can also play a buffering effect on the direct piercing of the diaphragm by foreign matter in the process, thereby avoiding safety problems caused by this.

[0051] 5. The three-dimensional sandwich diaphragm structure of the battery of the present invention retains the electrolyte in the directional distribution in the height direction of the diaphragm. Compared with other structures, it can accelerate the infiltration of the pole pieces, reduce the standing time in the production process, and improve the production efficiency.

[0052] 6. The three-dimensional sandwich diaphragm structure of the battery of the present invention has strong designability.

[0053] In summary, compared with the prior art, the present invention provides a three-dimensional battery sandwich diaphragm structure with hierarchical liquid retention capability. Its structural design is scientific, and the electrolyte can be controlled to achieve hierarchical storage at different height levels, thereby It prevents battery safety and electrical performance problems caused by lack of electrolyte, which is of great production and practical significance.

[0054] In addition, the three-dimensional battery sandwich diaphragm structure with hierarchical liquid retention capability provided by the present invention has high flexibility, and can flexibly design the channel size, distribution position and density according to the difference in coating amount at different positions of the pole pieces, thereby controlling the orientation Distribute electro-hydraulic. All current diaphragms do not have this structure and function.

[0055] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.