CN100517852C - A wound lithium ion battery and manufacturing method thereof - Google Patents

Abstract

The invention provides a winding lithium ion battery and its manufacturing method, which is characterized in that a current collector blank with a certain width is reserved on the upper side of the positive electrode sheet and the lower side of the negative electrode sheet along the winding direction. Stagger the positive and negative electrodes by a certain distance along the width direction and wind them into batteries. Pour the blank current collectors exposed at both ends of the cell into a flat surface, and then weld the current collector plates or tabs on the end faces respectively. Or fold the blank current collectors reserved for the positive and negative electrodes, and then stagger them along the width direction to expose the folded blank blanks and wind them into batteries, and directly weld the collector plates or tabs on both ends of the batteries. The end surface current collecting structure of the present invention not only increases the contact area between the current collecting plate and the pole piece, but also ensures the welding strength, effectively reduces the internal resistance of the battery, and the current density is evenly distributed in the process of charging and discharging with a large current, with less heat generation and heat dissipation Good performance is conducive to improving the safety and cycle life of batteries, and is suitable for power batteries such as electric tools, electric bicycles and electric vehicles.

Description

A wound lithium ion battery and manufacturing method thereof

technical field

The invention relates to a lithium-ion battery and a manufacturing method thereof, in particular to a wound-type lithium-ion battery with high-power charging and discharging characteristics and a manufacturing method thereof, belonging to the field of lithium-ion batteries.

Background technique

In recent years, with the rapid rise of electric tools, electric toys, model airplanes and electric vehicles, higher requirements have been put forward for the high rate charge and discharge performance of secondary batteries. Lithium-ion batteries have been widely used due to their outstanding characteristics such as high operating voltage, high energy density, low pollution, long cycle life, and low self-discharge rate. At present, most of the traditional winding lithium-ion batteries use single or multiple tabs as the current collection method. During the discharge process, the current distribution is uneven, and it is difficult to realize high-current charge and discharge. In addition, when charging and discharging with high current, due to the large internal resistance of the battery, it will cause serious heating and the temperature of the battery will be too high, which will cause potential safety hazards. Therefore, improving the high-current charge-discharge characteristics of lithium-ion batteries has become one of the current research focuses. Most of the research is devoted to improving the high-current charge and discharge performance of positive and negative active materials and electrolytes of lithium-ion batteries, and has achieved certain results, but the power characteristics still restrict the application of existing lithium-ion batteries in the field of power batteries. . The end-face current collection technology of the electrode has been successfully applied to the alkaline secondary battery, which has greatly improved the power performance of the battery.

It has also been attempted to introduce the end surface current collection technology of the electrode into the lithium-ion battery. For example, the positive electrode sheet at the left end of the cell in CN2817081Y has exposed aluminum foil to form the positive electrode fluid, and the negative electrode sheet at the right end of the cell has exposed copper foil to form the negative electrode fluid. After the end faces of the positive and negative fluids stick together or weld a collector plate, they stick to the poles. This end surface current collecting structure can effectively improve the current converging effect of the battery, which is beneficial to the high current performance. However, the end face of the wound battery is generally not smooth, and the current collecting plate needs to be welded at multiple points, and there will be force between the solder points, which is easy to desolder. The connection between the current collecting plate and the pole piece in this end surface current collecting structure belongs to point contact, and the contact area is small. At the same time, the positive and negative current collectors of lithium-ion batteries usually use thin aluminum foil (15-30 μm) and copper foil (5-20 μm), which have poor strength and are easily distorted and deformed when welding under a certain pressure, causing welding failure. tight or a short circuit occurs. Therefore, it is necessary to improve the current collecting structure of the end surface, ensure the welding strength and increase the drainage area of the end surface to further improve the high-current charging and discharging performance of the battery.

Contents of the invention

A winding lithium ion battery provided by the present invention is characterized in that a current collector blank with a certain width is reserved on the upper side of the positive electrode sheet and the lower side of the negative electrode sheet along the winding direction. When winding, the positive and negative electrode sheets are staggered by a certain distance along the height direction of the battery. The staggered distance is equivalent to the reserved current collector blank width, exposing the blank current collector, and the separator is located in the middle of the positive and negative electrode sheets. The upper and lower ends of the wound battery core are edged, and the blank current collector that has leaked out is flattened to form a plane, and then the current collector plate or tabs are respectively welded on the end faces. The blank current collectors reserved after the edge treatment are connected upside down to form a plane, the contact and connection of the current collectors themselves are greatly strengthened, the contact between the end face and the collector plate or tab is surface contact, and the contact area is greatly increased. At the same time, the force strength of the end face after the edge treatment is greatly increased, which ensures the welding strength of the collector plate. Or first fold the blank current collectors reserved for the positive and negative electrodes, and then stagger along the width direction to expose the folded edge blanks and wind them into cells, and then directly weld the current collecting discs or tabs on both ends of the cells to form an end current collecting structure . The end area of the battery core wound after the positive and negative pole pieces are folded is increased, and the force strength is obviously increased, which ensures the contact area and welding strength between the current collector plate and the pole piece.

The wound lithium-ion battery of the present invention is composed of positive electrode sheet 1, negative electrode sheet 2, separator 3, cap 4, metal shell 5, positive electrode current collector or tab 6 and negative electrode current collector or tab 7. The production process is as follows: (1) Add the active material, conductive agent and binder to an appropriate amount of solvent, stir evenly and apply it on both sides of the current collector. When coating, one side of the pole piece is reserved along the length direction for a certain width. The current collector is blank; (2) the pole pieces are cut according to the designed size after drying and rolling, and the positive pole piece 1 and the negative pole piece 2 are obtained; (3) the positive pole piece and the negative pole piece are staggered along the battery height direction by a certain amount during winding. When the blank current collector leaks from the distance, the diaphragm 3 is placed in the middle and wound into a battery cell, and then the upper and lower ends of the battery cell are edged, and the leaked blank current collector is flattened to form a plane. Or fold the blank current collectors of the positive and negative electrodes and stagger them along the width direction to expose the blanks of the folds. The positive and negative current collectors of the folds are located on both sides, and the middle of the pole pieces is wound with a diaphragm to form a battery cell; (4) The two ends of the core are welded to the current collecting plate or the tabs 6 and 7; (5) After the battery is installed in the case, the bottom point, the rolling groove, the welding cap, the liquid injection and the sealing are carried out.

The advantage of the winding lithium-ion battery of the present invention is that the unique end-face current-collecting structure greatly increases the end-face current-collecting area and improves the welding strength, and realizes the uniform distribution of the current density during the battery's high-current charging and discharging process, reducing the Internal resistance, good heat dissipation performance, can effectively control the battery temperature during high-current charging and discharging, and improve the safety and cycle life of the battery. It is suitable for power batteries such as electric tools, electric bicycles and electric vehicles. The manufacturing method of the invention is economical and simple, and is easy to realize large-scale production. The active material utilization rate of the battery is high, and the high-rate charging and discharging performance is excellent, and the invention has broad application prospects in designing and manufacturing high-power lithium-ion batteries.

Description of drawings

Fig. 1: Schematic diagram of the positive electrode sheet structure of the present invention;

Fig. 2: Schematic diagram of negative plate structure of the present invention;

Figure 3: Schematic diagram of the battery cell after edge treatment in the present invention;

Figure 4: Schematic diagram of the structure of the wound lithium ion battery of the present invention;

Figure 5: 15C discharge curve of the lithium ion battery of Example 1 of the present invention.

The labels in the figure are: 1. Positive electrode sheet; 2. Negative electrode sheet; 3. Diaphragm; 4. Cap; 5. Metal shell; 6. Positive electrode collector plate; 7. Negative electrode collector plate; ; B, negative electrode blank current collector.

Detailed ways

Example 1

A 1.2Ah high-rate 18650 lithium-ion battery made by this method. Dissolve polyvinylidene fluoride in an appropriate amount of N-methylpyrrolidone to make a glue, and mix lithium iron phosphate and superconducting carbon black according to lithium iron phosphate: superconducting carbon black: polyvinylidene fluoride = 90:5:5 Add the proportion of the glue into the glue, stir it evenly, and apply it on both sides of the 20μm thick aluminum foil. When coating, reserve a 1mm wide blank on the front and back sides of one side, and cut it after drying and rolling to obtain a coating width of 57mm. A positive electrode sheet 1 with a blank width of 1 mm. Add mesocarbon microspheres, SBR, CMC and superconducting carbon black in deionized water at a ratio of 94.5:2.25:2.25:1, stir evenly, and coat on a 9 μm thick copper foil, with one side reserved The blank with a width of 1 mm was dried and rolled, and then cut to obtain a negative electrode sheet 2 with a coating width of 57 mm and a blank width of 1 mm. The positive and negative electrodes are staggered by 1 mm along the width direction to expose the blank current collector, and the separator is placed in the middle and then wound to form a battery cell. The two end faces of the cell are edged and welded to a collector plate with a diameter of 15mm. After the battery cell is installed in the case, the bottom point, rolling groove, welding cap, liquid injection and sealing are carried out. After the battery is formed and the capacity is divided, the high-rate performance test is carried out. As can be seen from the discharge curve in Figure 5, compared with the conventional single-pole lithium-ion battery, the lithium-ion battery with the end-face current-collecting structure provided by the present invention has a significantly higher high-current discharge platform, a significantly increased discharge capacity, and high-current discharge performance. Greatly improve.

Example 2

The 2.3Ah high-rate 26650 lithium-ion battery made of this end-face current collection structure uses spinel lithium manganate as the positive active material, artificial composite graphite as the negative active material, lithium manganate in the positive electrode: superconducting carbon black: polybias The ratio of chlorofluoroethylene is 94:3:3, and the rest of the production process is the same as above. A blank current collector with a width of 6 mm is left along the length direction on one side of the positive and negative electrodes. A separator is sandwiched between the positive and negative electrodes and wound into a battery core. After the two end faces of the cell are edged, two 6mm wide nickel tabs are welded to the negative end, and one 6mm wide aluminum tab is welded to the positive end and then welded to the cap. After the battery cell is installed in the case, the bottom point, rolling groove, welding cap, liquid injection and sealing are carried out. After the battery is formed and the capacity is divided, the high-rate performance test is carried out. The performance is the same as in Figure 5.

Example 3

In the 1.4Ah high-rate SC-type lithium-ion battery produced by adopting the end surface current collecting structure of the present invention, the positive electrode active material adopts lithium-nickel-cobalt-manganese-oxygen ternary material, and the negative electrode active material adopts mesophase carbon microspheres. The manufacturing process of the pole piece is the same as above, the coating width of the pole piece is 30mm, and the blank width is 10mm. After the blank current collector is folded in half twice, the width of the blank edge is 2.5mm. The positive and negative plates are staggered by 2.5mm along the width direction, exposing the blank folded edge, with a separator in the middle and then wound into a battery cell. Weld three 4mm wide nickel lugs on the negative end, weld a 15mm diameter current collector on the positive end, and then weld it to the cap. After the battery cell is installed in the case, the bottom point, rolling groove, welding cap, liquid injection and sealing are carried out. After the battery is formed and the capacity is divided, the high-rate performance test is carried out. The performance test results are similar to Example 1.

Claims (4)

1. A winding lithium-ion battery, consisting of a positive electrode sheet (1), a negative electrode sheet (2), a diaphragm (3), a cap (4), a metal case (5), a positive electrode current collector (6) and a negative electrode The current collector plate (7) is composed of a collector plate (7), which is characterized in that the upper side of the positive electrode sheet (1) and the lower side of the negative electrode sheet (2) are reserved with a certain width of the current collector blank along the winding direction; the blanks reserved for the positive and negative electrode sheets After the current collector is folded, the edge is exposed along the width direction and the blank is wound into a battery core, and then the positive current collector plate (6) or the negative electrode current collector plate (7) is directly welded on both ends of the battery core to form an end current collector structure; The staggered distance of the negative electrode sheet along the width direction is equivalent to the width of the current collector blank after folding. 2. The wound lithium ion battery according to claim 1, characterized in that the separator (3) is located between the positive collector sheet (1) and the negative electrode sheet (2). 3. The manufacturing method of the wound lithium ion battery according to claim 1 or 2, characterized in that the manufacturing steps are: (a) Add the active material, conductive agent and binder into an appropriate amount of solvent, stir evenly, and apply on both sides of the current collector. When coating, reserve a certain width of the current collector blank along the length direction on the side of the pole piece; (b) The electrode sheet is cut according to the designed size after being dried and rolled to obtain a positive electrode sheet (1) and a negative electrode sheet (2); (c) Fold the blank current collectors of the positive and negative electrodes and stagger them along the width direction to expose the blanks of the folds. The positive and negative current collectors of the folded edges are located on both sides, and a separator (3) is sandwiched between the electrodes, which is wound into an electric current collector. core; (d) Weld the positive electrode current collecting plate (6) and the negative electrode current collecting plate (7) on the two ends of the battery cell; (e) After the battery cell is installed in the case, do bottom point, roll groove, welding cap, liquid injection and sealing. 4. The manufacturing method of wound lithium ion battery according to claim 3, characterized in that the coating width of the positive and negative electrode sheets is 30mm, the blank width is 10mm, and the blank current collector is empty after being folded twice. The side width is 2.5mm, and the positive and negative electrodes are staggered by 2.5mm along the width.

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