【Battery Products】Characteristics and comparative analysis of cylindrical, square shell, soft pack battery cells and battery packs

 1.Overview of three types of batteries

1. Cylindrical battery cell

The cylindrical battery cell was first invented by Sony Corporation of Japan in 1992. It has a long history of development and a high degree of standardization. Common models include 18650, 21700, 46800, etc. It adopts a mature winding process, with a high degree of automation, high production efficiency, good consistency and relatively low cost. For example, the 21700 battery used in Tesla Model 3 and Model Y, and the 46800 battery that is about to be mass-produced, once made the cylindrical battery cell popular in the market. However, there are also some problems with cylindrical batteries. Due to the cylindrical shape, the space utilization rate is low, and in the case of modularization, a large space waste will be caused. At the same time, the radial thermal conductivity is not good, the number of windings of the battery cannot be too many, and the single cell capacity is small. When used in electric vehicles, a large number of single cells are required to form battery modules and battery packs, and the connection loss and BMS management complexity are greatly increased. In addition, the weight is large. Compared with some other shapes of batteries, the weight at the same capacity may be large, which may not be suitable for some applications with high lightweight requirements.

Lithium Battery Cell Production Process

A battery cell is the smallest unit of a battery system. Multiple battery cells form a module, and multiple modules form a battery pack. This is the basic structure of a car power battery. A battery is like a container for storing electrical energy. The amount of capacity it can store is determined by the amount of active material covered by the positive and negative electrodes. The design of the positive and negative electrode plates needs to be tailored to different models. The gram capacity of the positive and negative electrode materials , the ratio of active materials, the thickness of the electrode plates, the compaction density, etc. are also crucial to the capacity.

explanation of lithium-ion power battery technology - battery cell

What are battery cells? How many types are there?

The cell of a lithium-ion battery is the core unit for storing and providing electrical energy in a lithium battery system. Each cell stores and releases electrical energy through electrochemical reactions. The components of a lithium-ion secondary rechargeable battery include a cell and a protection circuit board. Among them, the cell is the core part of the rechargeable battery responsible for storing electrical energy, while the protection circuit board is responsible for the safety management of the battery. If the protection circuit board is removed, the remaining part is the cell. The quality of the cell directly determines the overall performance and quality of the rechargeable battery.

Study on coating and drying of lithium iron phosphate positive electrode sheets

The coating and drying of lithium battery pole pieces accounts for 8% to 10% of the entire manufacturing cost of lithium batteries, which is mainly due to the low thermal efficiency of the pole piece drying process. In addition, the residual solvent in the pole piece drying process has a great impact on the stability, capacity and cycle life of the subsequent processing of the pole piece. The pole piece drying process not only affects the manufacturing cost of the battery, but also indirectly determines the manufacturing process level and safety.This paper studies the drying characteristics of the coating layer of the positive electrode of LiFePO4 battery under static drying and hot air tunnel drying conditions, and analyzes its drying rules to provide a reference for optimizing the hot air drying process and the development of corresponding drying equipment.

Lithium battery positive and negative plates

1. What is the coating substrate?

In lithium-ion batteries, the positive and negative active materials are coated on the substrate to make the pole pieces, which are then wound or stacked to form the battery cell. The substrates used here are mainly copper foil and aluminum foil. The current lithium battery positive electrode is aluminum foil and the negative electrode is copper foil. This is because copper is easily oxidized at the positive electrode with a higher potential. At the same time, there is a dense oxide layer on the surface of the aluminum foil, which protects the internal aluminum at high potential.

Understanding how lithium battery electrodes are prepared and how the quality of the electrodes during the preparation process affects the battery's performance.

1. Lithium battery pole piece production process

The general process of lithium-ion battery pole piece manufacturing is : pulping, coating, drying, rolling, cutting, etc. The specific process flow is shown in the figure below.

Lithium battery pole piece design basics, common defects and their impact on battery performance

1.Basics of Pole Design

The lithium battery electrode is a coating composed of particles, which is evenly coated on the metal current collector. The lithium-ion battery electrode coating can be regarded as a composite material, which mainly consists of three parts: