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During the manufacturing process of lithium-ion batteries, there are three crucial items that must be strictly controlled: dust, metal particles, and moisture. If dust and metal particles are not properly controlled, it will directly lead to safety accidents such as internal short circuits and fires in the battery. If moisture is not effectively controlled, it will also cause significant harm to battery performance and lead to serious quality accidents! Therefore, it is crucial to strictly control the water content of main materials such as electrodes, separators, and electrolytes during the manufacturing process. There must be no relaxation and constant vigilance! The following is a detailed explanation from three aspects: the harm of moisture to lithium batteries, the source of moisture during the manufacturing process, and the control of moisture during the manufacturing process. 1.  The harm of moisture to lithium batteries (1) Battery swelling and leakage: If there is excessive moisture in lithium-ion batteries, it reacts chemically with the lithium salt in the electrolyte, generating HF: H2O + LiPF6 → POF3 + LiF + 2HF Hydrofluoric acid (HF) is a highly corrosive acid that can cause significant damage to battery performance: HF corrodes the metal components, battery shell, and sealing within the battery, eventually leading to cracks, ruptures, and leakage. HF also destroys the SEI (Solid-Electrolyte-Interface) film inside the battery by reacting with its main components: ROCO2Li + HF → ROCO2H + LiF Li2CO3 + 2HF → H2CO3 + 2LiF Eventually, LiF precipitates form inside the battery, causing irreversible chemical reactions in the negative electrode that consume active lithium ions, thereby reducing the battery's energy capacity. When there is a sufficient amount of moisture, more gas is generated, increasing the internal pressure of the battery. This can lead to deformation, swelling, and even leakage, posing a safety risk. Many instances of battery swelling and cover popping encountered in mobile phones or digital electronic products on the market are often attributed to high moisture content and gas generation inside the lithium battery.   (2) Increased battery internal resistance: Battery internal resistance is one of the most critical performance parameters, serving as a primary indicator of the ease with which ions and electrons can travel within the battery. It directly affects the battery's cycle life and operating state. A lower internal resistance means less voltage is consumed during discharge, resulting in higher energy output. An increase in moisture content can lead to the formation of POF3 and LiF precipitates on the surface of the SEI film (Solid-Electrolyte-Interface). This degrades the density and uniformity of the SEI film, gradually increasing the battery's internal resistance and decreasing its discharge capacity.   (3) Shortened cycle life: Excessive moisture can damage the SEI film, leading to a gradual increa...

The side voltage of the battery specifically refers to the voltage of the aluminum layer between the cathode tab and the aluminum laminated film of the polymer battery. The side voltage of the polymer lithium battery refers to: 1.The voltage of the aluminum layer between the cathode tab and the aluminum laminated film; 2. The voltage of the aluminum layer between the anode tab and the aluminum laminated film. In theory, the aluminum layer between the cathode tab and the aluminum laminated film is insulated, which means that their voltage should be 0. In fact, during the processing of the aluminum laminated film, the inner PP layer may be locally damaged, resulting in local conduction (including electronic channels and ionic channels) between them, forming a micro-battery and thus a potential difference (voltage). The side voltage standards vary among manufacturers, but most of the industry sets it below 1.0V. The standard of voltage is based on the dissolution potential of aluminum-lithium alloy Side voltage testing: Side voltage testing is primarily used to inspect the sealing effect of lithium battery packaging films and detect short circuits between the tab and the aluminum laminated film of the packaging film. Short circuits can cause corrosion of the aluminum laminated film, electrolyte leakage, gas swelling, low voltage, and a series of other issues, posing safety hazards. The side voltage of lithium polymer batteries specifically refers to the voltage across the aluminum layer between the positive tab and the aluminum-laminated film of a polymer lithium battery. In theory, the aluminum layer between the positive terminal and the aluminum-laminated film should be insulated, meaning that their voltage should be zero. However, during the processing of the aluminum-laminated film, the inner PP layer can suffer from localized damage, resulting in partial conduction (including both electronic and ionic channels) between them. This creates a micro-battery, leading to a potential difference (voltage). The side voltage standards vary across manufacturers, but the industry generally sets it below 1.0V. The basis for this voltage standard is derived from the dissolution potential of the aluminum-lithium alloy. The potential difference between the positive tab and the aluminum-laminated shell is used to check if there are electronic channels between the negative tab and the aluminum-laminated film. If there are electronic channels between the negative tab and the aluminum-laminated film, and the inner PP layer of the aluminum-laminated film is damaged, corrosion may occur. One of the reasons for gas swelling: packaging corrosion. Gas swelling can be quite troublesome. Without effective detection methods, it's difficult to control defective products within the company and prevent them from reaching customers. The issue may manifest months later as gas swelling, leading to returns. In such cases, the aluminum-laminated film of the battery cell has alrea...

When there is only a low content of CMC in the slurry without SBR, graphite particles agglomerate during the homogenization process and cannot be well dispersed. When the ratio of CMC to graphite is moderate, adding 1.0% to 4.5% of SBR to the slurry will cause SBR to adsorb on the surface of graphite, dispersing the graphite particles and reducing the viscosity and modulus of the slurry. When the amount of CMC is 0.7% to 1.0%, the slurry exhibits viscoelasticity, and continuous addition of SBR will not change the rheological properties of the slurry. Comparing the two mixing methods of adding SBR and CMC simultaneously and adding CMC first and then SBR, the results show that CMC plays a leading role in the dispersion of graphite in the slurry, and CMC preferentially adsorbs on the surface of graphite particles. In general, when the amount of CMC added is very low, the addition of SBR will adsorb on the surface of graphite particles, which has a certain impact on the dispersion of graphite. As the amount of CMC added increases, the amount of adsorption on the surface of graphite also increases, and SBR cannot adsorb on the surface of graphite, thus playing no role in the dispersion of graphite. When a certain amount of CMC is reached, the combined attraction of excess CMC that fails to adsorb on the surface of graphite particles becomes greater than the repulsion, which can lead to agglomeration between graphite particles. Therefore, CMC plays a crucial role in the dispersion of graphite negative electrode slurry. Email :tob.amy@tobmachine.com Skype :amywangbest86 Whatsapp/Phone number :+86 181 2071 5609

Double planetary mixer Currently, the mainstream slurry mixing equipment used by lithium-ion battery manufacturers is the double planetary mixer, also known as the PD mixer. This mixer is equipped with a low-speed mixing component, Planet, and a high-speed dispersing component, Disper. The low-speed mixing component comprises two folding frame agitators that utilize planetary gear transmission. As the agitators rotate and orbit, they allow the material to move in various directions, achieving the desired mixing effect within a relatively short time. The high-speed dispersing component typically features a toothed dispersing disk that rotates along with the planetary carrier while spinning rapidly, exerting intense shearing and dispersing forces on the material. This effect is several times greater than that of ordinary mixers. Additionally, the dispersing component can be configured with either a single or double dispersing shaft, depending on the specific requirements of the application. Ball mill mixing Ball milling mixing is also often used for the preparation of lithium-ion battery slurry, which is generally more common in laboratories. Similar to fluid mechanics-based mixing methods, the dispersion ability of the ball milling process is determined by the balance of cluster fragmentation and agglomeration reorganization speeds, which is related to the properties of powder particles and can be changed by the addition of surfactants. In the ball milling process, powder particles undergo a large number of surface and volumetric changes, which may lead to mechanical and chemical transformations of the material (such as the rupture of carbon nanotubes, changes in their aspect ratio and structure). Reactions may occur between particles, between powder and dispersing media (solvents and binders), and even between powder and grinding balls. Collisions between grinding balls and local fluid high-shear turbulence can also cause the rupture of binder molecules. Ultrasonic stirring Currently, ultrasound is used by people for mixing at the microscopic scale based on the transient acoustic cavitation effect. This effect needs to be generated under quite high ultrasonic intensity, accompanied by the formation and growth of a large number of microbubbles. When the bubble size reaches a certain critical value, the bubble growth rate increases rapidly and then ruptures instantly, forming shock waves to disperse agglomerates while causing local high temperature and high pressure (local pressure can reach thousands of atmospheres). Another process that occurs during ultrasonic mixing is the macroscopic flow of the liquid. The concentration of cavitation bubbles gradually decreases along the axis centered on the generator, and the bubbles diffuse to low-concentration regions, driving the liquid to flow with a speed of up to 2m/s. This fluid flow is sufficient to provide adequate mixing effects without the need for additional equipment. Email :tob.amy@tobmachine.c...

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1.Battery material aging and decay The materials inside lithium batteries mainly include: positive and negative electrode active materials, binders, conductive agents, current collectors, separators, and electrolytes. During the use of lithium batteries, these materials undergo a certain degree of decay and aging. Tang Zhiyuan et al. believed that the factors causing capacity decay in manganese acid lithium batteries include dissolution of the positive electrode material, phase changes in the electrode material, electrolyte decomposition, formation of an interfacial film, and corrosion of the current collector. Vetter et al. systematically and deeply analyzed the changes in the positive electrode, negative electrode, and electrolyte of the battery during cycling. The author believed that the formation and subsequent growth of the SEI film on the negative electrode would be accompanied by irreversible loss of active lithium, and the SEI film did not possess true solid electrolyte functionality. The diffusion and migration of substances other than lithium ions would lead to gas generation and particle rupture. In addition, changes in material volume during cycling and the precipitation of metal lithium would also lead to capacity loss. 2. Charge and discharge system  The charge and discharge system mainly includes three aspects: charge and discharge method, rate, and cut-off conditions. Regarding the charge method, American scientist Mas proposed the concept of an optimal charging curve. He believed that the optimal charging current of a battery gradually decreases as the charging time increases, which can be expressed by the formula I=I0e-αt. In this formula, I represents the receivable charging current; I0 represents the maximum initial current at the time t=0; t represents the charging time; and α represents the decay constant. The relationship curve between I and t is shown in follow Figure. 3.Temperature Different types of lithium batteries have different optimal operating temperatures, and both excessively high and low temperatures can have an impact on the service life of the batteries. 4.Cell Consistency Battery packs typically consist of hundreds or even thousands of individual cells connected in series or parallel. In addition to the aforementioned factors influencing their cycle life, cell consistency is another crucial factor. Due to differences in materials and manufacturing processes, it is challenging to ensure the consistency of lithium-ion battery cells. In terms of materials, the uniformity of positive and negative electrode materials and electrolytes is crucial. Lithium batteries produced from the same materials and in the same batch often exhibit relatively better consistency. In terms of manufacturing, the production process of lithium batteries is complex, involving multiple process parameters at each step. Poor control can lead to inconsistencies in parameters such as battery voltage, capacity, and internal resistance. E...

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Electrode piece coating generally refers to a process in which the evenly stirred slurry is evenly coated on the current collector and the organic solvent in the slurry is dried. The effect of coating has an important impact on the battery capacity, internal resistance, cycle life and safety, and ensures that the pole piece is evenly coated. The selection of coating methods and control parameters have an important impact on the performance of lithium-ion batteries, which are mainly manifested in: 1) Coating drying temperature control: if the drying temperature is too low during coating, it cannot guarantee that the pole piece is completely dry, if the temperature is too high, it may be because the organic solvent inside the pole piece evaporates too quickly, and the surface coating of the pole piece cracks and falls off; 2) Coating surface density: if the coating surface density is too small, the battery capacity may not reach the nominal capacity, if the coating surface density is too large, it is easy to cause batching waste, and if the positive electrode capacity is excessive in serious cases, lithium dendrites will be formed due to the precipitation of lithium to puncture the battery separator and cause a short circuit, causing potential safety hazards; 3) Coating size: The coating size is too small or too large may cause the positive electrode inside the battery to not be completely wrapped by the negative electrode, during the charging process, lithium ions are embedded from the positive electrode and move to the electrolyte that is not completely wrapped by the negative electrode, the actual capacity of the positive electrode can not be played efficiently, and in serious cases, lithium dendrites will be formed inside the battery, which is easy to puncture the separator and cause the internal circuit of the battery;   4) Coating thickness: If the coating thickness is too thin or too thick, it will have an impact on the subsequent electrode rolling process, and the performance consistency of the battery electrode piece cannot be guaranteed. Selection of coating equipment and coating process The coating process in a broad sense includes: uncoiling→ splicing→ tension control → pulling tabs→ coating → drying→ guiding → tension control→ guiding → winding and other processes. The coating process is complex, and there are many factors that affect the coating effect, such as: the manufacturing accuracy of the coating equipment, the smoothness of the equipment operation, the control of the dynamic tension in the coating process, the size of the air volume in the drying process and the temperature control curve will affect the coating effect, so it is extremely important to choose the appropriate coating process.   Generally, the selection of coating method needs to be considered from the following aspects, including: the number of layers to be coated, the thickness of the wet coating, the rheological properties of the coating solution, the...