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CN-121983674-A - Method for improving volumetric specific energy of lithium ion power battery

CN121983674ACN 121983674 ACN121983674 ACN 121983674ACN-121983674-A

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a method for improving volumetric specific energy of a lithium ion power battery. The technical scheme is that the method mainly solves the problems that an aluminum alloy shell of an existing lithium ion power battery is heavy and internally connected, occupied space is occupied, the thickness of a cell layer is high due to core materials, and the like. According to the invention, through plating the nickel thin shell on the carbon steel, eliminating the switching piece, optimizing the cell material, saving the cell space, reducing the internal resistance, increasing the loading capacity of active substances in a limited volume, and improving the energy of the lithium iron phosphate power cell.

Inventors

  • LIU YAN
  • Zang Tiankuo
  • WANG WEIJIN
  • LI XIAOQING

Assignees

  • 实联新能源电池宿迁有限公司

Dates

Publication Date
20260505
Application Date
20260302

Claims (9)

  1. 1. A method for increasing the volumetric specific energy of a lithium ion power battery, comprising the steps of: firstly, designing a shell in a lightweight way, namely adopting a carbon steel nickel plating composite shell, wherein the composite shell is sequentially provided with a carbon steel substrate, a Ni-P alloy interface transition layer and a gradient nickel plating layer from inside to outside; releasing the inner space, namely welding the electrode lugs with the electrode posts through two steps of laser welding of pre-spot welding and deep-penetration welding after the electrode lugs are overlapped in multiple layers; step three, ultrathin electric core materials and performance optimization: the negative electrode current collector adopts a high-conductivity copper foil with the thickness of 4.2-4.8 mu m, and the positive electrode current collector adopts a carbon-coated aluminum foil with the thickness of 10.5-11.5 mu m; The diaphragm adopts a composite ceramic coating diaphragm of Al 2 O 3 and ZrO 2 ; The positive electrode material adopts ultra-high compacted lithium iron phosphate which is coated by Li 3 PO 4 and doped and modified by Nb 2 O 5 , and the compacted density is 2.62-2.65g/cm 3 ; and step four, the winding process is adapted, namely a gradual change tension winding method is adopted, and the gap between the winding core and the inner wall of the shell is 0.3-0.5mm, so that the preparation and assembly of the battery cell are completed.
  2. 2. The method for improving volumetric specific energy of a lithium ion power battery according to claim 1, wherein in the first step, the thickness of the carbon steel substrate is 0.22-0.28mm, the thickness of the top cover is 0.6-0.8mm, and the thickness of the side wall is 0.25-0.3mm; The thickness of the Ni-P alloy interface transition layer is 0.1-0.3 mu m; the total thickness of the gradient nickel plating layer is 2-3 mu m.
  3. 3. The method for improving the volumetric specific energy of the lithium ion power battery according to claim 2, wherein in the first step, the gradient nickel plating layer comprises a bottom compact nickel plating layer and a surface loose nickel plating layer, wherein the thickness of the bottom compact nickel plating layer is 1-1.5 mu m, the porosity is less than or equal to 5%, the thickness of the surface loose nickel plating layer is 1-1.5 mu m, and the porosity is 10% -15%; the grain size ratio of the bottom layer to the surface layer is 1:2-3; The plating solution of the gradient nickel plating layer comprises the raw material components of ：NiSO 4 ・6H 2 O 220-240g/L、NiCl 2 ・6H 2 O 32-38g/L、H 3 BO 3 33-37g/L、 g/L brightening agent 0.3-0.8g/L leveling agent 0.1-0.3g/L and stress relieving agent 0.5-1.2g/L; The brightening agent is a compound of saccharin sodium and 1, 4-butynediol, and the mass ratio of the saccharin sodium to the 1:0.8-1.2; the leveling agent is sodium dodecyl sulfate; The stress relieving agent is coumarin.
  4. 4. The method for improving the volumetric specific energy of the lithium ion power battery according to claim 3, wherein the plating solution of the gradient nickel plating layer comprises the raw materials of 4 ・6H 2 O 230g/L、NiCl 2 ・6H 2 O 35g/L、H 3 BO 3 g/L of NiSO, 0.55 g/L of brightening agent, 0.2g/L of leveling agent and 0.8g/L of stress relieving agent.
  5. 5. The method for improving the volumetric specific energy of the lithium ion power battery according to claim 4, wherein in the first step, the preparation of the carbon steel nickel-plated composite shell comprises the following steps of degreasing, pickling and activating a carbon steel base material, depositing a Ni-P alloy interface transition layer through chemical plating, preparing a gradient nickel-plated layer through double pulse electroplating, and finally carrying out vacuum annealing at 200-250 ℃ for 1-2h.
  6. 6. The method for improving the volumetric specific energy of the lithium ion power battery according to claim 1, wherein the electroplating solution of the gradient nickel plating layer further comprises 0.05-0.15g/L cobalt chloride as a grain refiner for adjusting and controlling the grain size of the bottom compact nickel plating layer to 50-80nm and the grain size of the surface loose nickel plating layer to 100-240nm.
  7. 7. The method for improving the volumetric specific energy of the lithium ion power battery according to claim 1, wherein in the second step, the pre-welding power is 800-1000W, the welding spot diameter is 0.8-1mm, the deep-welding power is 1200-1500W, and the welding seam width is 1.2-1.5mm.
  8. 8. The method for increasing volumetric specific energy of a lithium ion power battery according to claim 1, wherein in the third step, the carbon-coated aluminum foil has a carbon-coated layer thickness of 0.5-0.8 μm and a ceramic-coated layer thickness of 1.5-2 μm.
  9. 9. The method of claim 1, wherein the winding tension in the fourth step is 5-8N and the winding speed is 0.8-1.2m/s.

Description

Method for improving volumetric specific energy of lithium ion power battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a method for improving volumetric specific energy of a lithium ion power battery. Background With the rapid development of the fields of new energy automobiles, energy storage power stations and the like, the lithium ion power battery is used as a core energy supply component, the energy density of the lithium ion power battery becomes a key factor for limiting the endurance mileage and the energy storage capacity of a terminal product, and the demand of the market on the high-volume specific energy power battery is increasingly urgent. At present, the existing lithium ion power battery generally adopts an aluminum alloy material as a battery core shell structural design, the thickness of the aluminum alloy material is high, a massive shell occupies a large amount of internal space of the battery, the loading capacity of active substances is limited, the space utilization rate of the battery is seriously reduced, meanwhile, the anti-extrusion strength and the anti-internal pressure performance of the aluminum alloy material are limited, if the thickness of the shell is simply reduced, the safety performance of the battery is obviously reduced, the connection between a lug and a pole of a lithium iron phosphate square battery generally adopts a three-section structure of 'lug-switching piece-pole', the use of the switching piece also occupies the internal space of the battery, and the thickness of each unit layer in the battery is high due to the selection of the existing battery core material, so that the improvement of the volumetric specific energy of the battery is seriously limited. Therefore, a new battery design concept is urgently needed to meet the market demand for high energy density lithium ion batteries. In view of the above, the present invention proposes a method for increasing the volumetric specific energy of a lithium ion power battery. Disclosure of Invention The invention aims to solve the problems of high thickness of a unit layer and the like caused by thick internal connection of an aluminum alloy shell of an existing lithium ion power battery and electric core material in the background art, and provides a method for improving the volumetric specific energy of the lithium ion power battery. The technical scheme of the invention is that the method for improving the volumetric specific energy of the lithium ion power battery comprises the following steps: firstly, designing a shell in a lightweight way, namely adopting a carbon steel nickel plating composite shell, wherein the composite shell is sequentially provided with a carbon steel substrate, a Ni-P alloy interface transition layer and a gradient nickel plating layer from inside to outside; releasing the inner space, namely welding the electrode lugs with the electrode posts through two steps of laser welding of pre-spot welding and deep-penetration welding after the electrode lugs are overlapped in multiple layers; step three, ultrathin electric core materials and performance optimization: the negative electrode current collector adopts a high-conductivity copper foil with the thickness of 4.2-4.8 mu m, and the positive electrode current collector adopts a carbon-coated aluminum foil with the thickness of 10.5-11.5 mu m; The diaphragm adopts a composite ceramic coating diaphragm of Al 2O3 and ZrO 2; The positive electrode material adopts ultra-high compacted lithium iron phosphate which is coated by Li 3PO4 and doped and modified by Nb 2O5, and the compacted density is 2.62-2.65g/cm 3; and step four, the winding process is adapted, namely a gradual change tension winding method is adopted, and the gap between the winding core and the inner wall of the shell is 0.3-0.5mm, so that the preparation and assembly of the battery cell are completed. Optionally, in the first step, the thickness of the carbon steel substrate is 0.22-0.28mm, the thickness of the top cover is 0.6-0.8mm, and the thickness of the side wall is 0.25-0.3mm; The thickness of the Ni-P alloy interface transition layer is 0.1-0.3 mu m; the total thickness of the gradient nickel plating layer is 2-3 mu m. Optionally, in the first step, the gradient nickel plating layer comprises a bottom compact nickel plating layer and a surface loose nickel plating layer, wherein the thickness of the bottom compact nickel plating layer is 1-1.5 mu m, the porosity is less than or equal to 5%, the thickness of the surface loose nickel plating layer is 1-1.5 mu m, and the porosity is 10% -15%; the grain size ratio of the bottom layer to the surface layer is 1:2-3; The plating solution of the gradient nickel plating layer comprises the raw material components of ：NiSO4・6H2O 220-240g/L、NiCl2・6H2O 32-38g/L、H3BO3 33-37g/L、 g/L brightening agent 0.3-0.8g/L leveling agent 0.1-0.3g/L and stress relieving agent 0.5-1