The Importance of Lithium ion Battery Slurry Viscosity

Lithium batteries, a new type of high-energy battery developed in the 20th century, are batteries that contain lithium elements, including metallic lithium, lithium alloys, lithium ions, and lithium polymers. These can be categorized into lithium metal batteries (rarely produced and used) and lithium-ion batteries (widely used today). Thanks to their high specific energy, high voltage, wide operating temperature range, and long storage life, they have found widespread use in military and civilian small appliances, such as mobile phones, portable computers, cameras, and camcorders, partially replacing traditional batteries.

1. Structure and principle of lithium ion battery

The main components of lithium ion battery:

Cathode electrode —— active substances mainly refer to lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel oxide, lithium nickel cobalt oxide, etc., and the conductive current collector is generally used Aluminum Foil with a thickness of 10-20 microns;

Separator—— a special plastic film, can allow lithium ions through, but is an insulator of electrons, currently mainly PE and PP two and their combination. There is also a class of inorganic solid separator, such as aluminum oxide diaphragm coating is a kind of inorganic solid separator;

Anode electrode —— active material mainly refers to graphite, lithium titanate, or carbon materials with graphite-like structure, and the conductive current collector is generally used copper foil with a thickness of 7-15 microns;

Electrolyte —— generally an organic system, such as carbonate solvent dissolved with lithium hexafluorophosphate, and some polymer batteries use gel electrolyte;

Battery Case—— mainly divided into hard shell (steel shell, aluminum shell, nickel-plated iron shell, etc.) and soft pack (aluminum plastic film).

The core of the whole battery manufacturing, the quality of the battery slurry is particularly important.

The electrode slurry is composed of a variety of raw materials with different specific gravity and particle size, and is mixed and dispersed in solid-liquid phase. The slurry formed belongs to non-Newtonian fluid. In order to meet the requirements of subsequent coating process, the slurry needs to have the following three characteristics:

1. Good fluidity: Fluidity can be observed by stirring the slurry and letting it flow naturally, observing its continuity. Good continuity, continuous and intermittent, indicates good fluidity.

2. Flowability: The flowability of the paste affects the flatness and uniformity of the coating.

3. Rheology: Rheology refers to the deformation characteristics of slurry in flow, and its properties affect the quality of electrode sheet.

The electrode slurry must have a stable and appropriate viscosity, which is crucial for the electrode sheet coating process. For battery slurry, the viscosity range is 2000-10000mPa.s. Both too high and too low viscosities are detrimental to the electrode sheet coating. A high viscosity prevents sedimentation and improves dispersion, but it hinders leveling and coating. On the other hand, too low viscosity, while improving fluidity, makes drying difficult, reduces coating efficiency, and can lead to coating cracking, particle aggregation, and inconsistent surface density.

Rotary viscometer is one of the commonly used types of viscometers. The structure is simple, easy to use, and has a wide measurement range. It is commonly used to measure the absolute viscosity of Newtonian liquids and the apparent viscosity of non Newtonian liquids. When a rotor is placed in the middle of a sample and rotates at a constant speed, viscosity is determined by measuring the torque (shear stress) acting on the surface of the rotor.

AOT rotary viscometer can be used for viscosity measurement of various fluids. It is assembled quickly and equipped with different types of rotors, suitable for measuring high, medium, and low viscosity samples. The measurement range is wide, and the sample size can be as low as 15ml. With a one click design, it is easy to operate and can use disposable containers (paper cups) instead of traditional beakers, reducing cleaning time and helping to improve work efficiency. And it is widely used for fluid viscosity measurement in various chemical industries such as adhesives, adhesives, food, pharmaceuticals, coatings, lubricants, etc. The portable design can be used for both laboratory and on-site rapid measurement, making it a compact and portable viscometer.