Assembling method of square winding type lithium ion battery and lithium ion battery

Abstract

The invention belongs to the technical field of battery assembly, and relates to an assembling method of a square winding type lithium ion battery and the lithium ion battery. The assembling method ofthe lithium ion battery comprises the following steps of: shaping a roll core in at least one hot pressing and / or cold pressing manner; making a positive electrode blank area and a negative electrodeblank area at the two ends of the roll core respectively; flattening at least one part of the positive electrode blank area and the negative electrode blank area of the shaped roll core to respectively form a positive electrode flattening area and a negative electrode flattening area; respectively welding the positive electrode flattening region and the negative electrode flattening region with the positive electrode busbar and the negative electrode busbar in a laser welding manner; and putting into a shell to obtain the square winding type lithium ion battery. The battery energy density ofthe square winding full-tab design is improved, the problems of small effective volume proportion of the winding cores, low battery energy density, difficulty in parallel assembly of multiple windingcores and the like in the traditional assembly process are solved, and the process is simple, feasible, efficient, controllable and low in process loss.

Description

technical field [0001] The invention belongs to the technical field of battery assembly, and in particular relates to an assembly method of a square wound lithium-ion battery and the lithium-ion battery. Background technique [0002] Lithium batteries have been widely used in new energy vehicles, energy storage and other fields due to their advantages such as high voltage, large specific energy, long charge and discharge life, stable discharge performance, low self-discharge rate and no pollution. With the development of the market, especially the rapid development of new energy vehicles, the needs of the industry, and the guidance of national policies, the requirements for the rate performance and energy density of power lithium-ion batteries are getting higher and higher. According to "Made in China 2025", the development plan of power batteries is clarified: in 2020, the battery energy density will reach 300Wh / kg; in 2025, the battery energy density will reach 400Wh / kg; i...

AI Technical Summary

Problems solved by technology

The traditional full tab solution: no need to die-cut the uncoated current collector, and the welding process is simple, but because the positive or negative electrode is welded to the bus bar through ultrasonic welding, the welding area is large, and when welding, The misalignment between layers results in a high ratio of positive and negative coating blanks, so the effective volume of the core in the single casing is less. The energy density of the full-tab solution of the same size is 5% lower than that of the multi-tab solution. ~15%; when the capacity of a single cell is increased, multiple winding cores need to be connected in parallel, and the parallel assembly process of multiple cells is difficult to realize, and the effective volume of the winding core is less

Traditional multi-tab solution: Due to the die-cutting of the uncoated current collector part of the pole piece, one more process is required; and the pole piece after die-cutting is in the winding process, which requires high requirements on the winding machine and low production efficiency ; There are many blank design of the current collector, resulting in a lot of process loss, which has a certain impact on improving the compaction of the pole piece

[0004] Therefore, it is desired to provide an assembly method of a square winding lithium-ion battery, which can alleviate the problems of low energy density of the battery in the existing all-tab design scheme and difficult assembly when designing multi-winding cores in parallel.

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