Elaborate the Lithium-ion Battery Manufacturing Process 5 - Winding/Stacking

 Winding Process

1. Principle and Process

• Principle: The winding process involves the use of a fixed winding needle to wind and compress the pre-processed anode sheets, separator, and cathode sheets in sequence to form a cylindrical or elliptical shape.
• Process: The raw materials are stacked in the sequence of anode, separator, cathode, separator. Then, they are wound into cylindrical or elliptical shapes and placed into metal casings, either square or cylindrical. Specific steps include the unwinding of the anode and cathode sheets and separators, automatic alignment, automatic tension detection and control. The anode and cathode sheets are fed into the winding section by a clamp feeding mechanism, which, together with the separator, undergoes automatic winding according to specified process requirements. After the winding is completed, the machine automatically switches workstations, cuts the separator, attaches the end seal tape, and the finished bare cell is automatically discharged. After pre-pressing, the cell is transported to the discharge outlet by a pull belt.
• Application Scenario: The winding process is mostly used in square and cylindrical batteries.

An Overview of the Four Steps in the Formation of Lithium Batteries

The formation process is an indispensable step in the manufacturing of lithium-ion batteries, as it directly affects the battery’s performance, safety, and lifespan.

One of the key roles during the formation process is the formation of a stable solid electrolyte interphase (SEI) film on the surface of the anode.

The SEI film protects the anode material from further erosion by the electrolyte, preventing the dissolution of the anode material in the electrolyte and thus extending the battery’s lifespan.

Tsinghua University’s Kang Feiyu Team Reports in Nature Communications: Homogeneous Polymer-Ion Solvent Electrolyte with Weak Dipole-Dipole Interactions Enables High-Performance Lithium Metal Pouch Cells

Lithium metal batteries have attracted significant attention due to their high energy density. However, their development has been hindered by issues such as uncontrollable dendrite growth of lithium metal anodes, unstable solid electrolyte interphase (SEI), and poor cycling stability. Solid-state electrolytes (SSEs) are attractive due to their inherent safety, with polymer solid-state electrolytes (SPEs) receiving particular attention for their processability, cost-effectiveness, and good contact with electrodes. However, traditional SPEs (such as poly(ethylene oxide) (PEO)-based electrolytes) have low ionic conductivity (typically <10⁻⁵ S cm⁻¹ at room temperature), limiting their application at room temperature.

Comprehensive Solution for Negative Electrode Binders for Lithium Batteries                                                                                                                                                                                            

Overview of Lithium-ion Battery Binders

In the production of lithium-ion batteries, binders are often referred to as "auxiliary materials" together with conductive agents, additives, etc., but they are an indispensable key material. Their main function is to adhere active substances and conductive agents to the current collector to ensure electrical contact between powder material particles in the electrode and between the powder material and the current collector. Binders have a low mass ratio in the electrode and do not participate in electrochemical reactions. Their main function is to adhere active substances and conductive agents to the current collector to keep the electrode intact. Binders affect the formation of the solid electrolyte interface (SEI), charge transfer inside the electrode and between the electrode-electrolyte interface, the wetting behavior of the electrode, and the cycle performance and cost of the battery. Therefore, an ideal binder can ensure the stability of the electrode structure with the least possible usage.

An article to understand EIS lithium battery applications, with typical circuit model diagrams

An article to understand EIS lithium battery applications, with typical circuit model diagrams

1. What is electrochemical impedance spectroscopy (EIS)? 🔍

1️⃣Electrochemical impedance spectroscopy (EIS) is a non-destructive parameter determination and effective method for determining battery kinetic behavior. A small-amplitude sinusoidal voltage signal with a frequency of w1 is applied to the battery system, and the system generates a sinusoidal current response with a frequency of w2. The change in the ratio of the excitation voltage to the response current is the impedance spectrum of the electrochemical system.

Analysis of the influence of slurry quality on coating surface fluctuation｜‌Lithium battery production process front end (mixing/coating)

Lithium battery production process - mixing/coating

The production process of lithium batteries varies among different battery manufacturers. Generally speaking, it is divided into three stages: front, middle and back.

1. Front section: pole piece production

(Mixing, coating, tableting, baking, slitting, tableting, tab forming)

(Core link: coating)

2. Middle section: battery cell assembly

(winding or lamination, pre-packaging of cells (into shells), electrolyte injection, sealing)

(Core link: winding)

3. Post-processing (activating the battery cell)

(battery cell formation, capacity division, static placement, testing, and sorting)

(Core links: formation, volume fractionation, and testing)

Exploring the mixing process of lithium-ion batteries---mixer

Understand the principle of lithium-ion battery mixing equipment in one article

Found the culprit! -- Stanford University EES reveals: the fundamental reason for the difference in Coulombic efficiency of high-performance lithium metal battery electrolytes!

                  

Lithium metal batteries are considered ideal energy storage devices due to their high capacity and energy density, but the high activity of lithium limits their commercialization. In recent years, advances in the design of liquid electrolytes have improved the efficiency of lithium metal batteries, but the efficiency improvement has reached a bottleneck, and the reason is still unclear.

Science Bulletin: Carbonate electrolyte releases NO₃⁻ and I⁻ to achieve stable lithium metal batteries!

                   

The formation of inactive lithium (Li) in lithium metal batteries (LMBs) mainly originates from the undesirable components of the solid electrolyte interface (SEI) and the growth of lithium dendrites. Lithium nitrite (LiNO₃) as an electrolyte additive has shown great potential to alleviate interfacial instability and lithium dendrite growth by in situ constructing a nitride-rich SEI. However, the limited solubility of LiNO₃ in carbonate electrolytes (~0.01 mg mL⁻¹) restricts its practical application.

The "Breathing Technique" in Lithium Battery Baking: Decoding the Core Technology of Nitrogen Cycle

Why is nitrogen circulation introduced in the vacuum baking of lithium batteries? The seemingly safe inert gas actually hides the risk of condensation! Behind the efficiency improvement is the ultimate control of the "breathing rhythm" by precision technology - this article deciphers the game logic of nitrogen filling, dehumidification and risk prevention and control.

Is it necessary to introduce nitrogen circulation during vacuum baking of battery cells? When filling with nitrogen, the pressure inside the cavity will change. Will the moisture condense again and affect the baking effect?

Key auxiliary materials in lithium batteries - conductive agents

 Key auxiliary materials in lithium batteries - conductive agents

Conductive agent is an important auxiliary material for batteries, and conductive carbon black is the most widely used conductive agent. The main function of conductive agent is to improve the conductivity of batteries. Only a small amount of addition can greatly improve the performance of lithium batteries. Conductive agent products include conductive carbon black, carbon nanotubes, graphene, etc., which are important auxiliary materials for batteries.

1

Why do we need to add conductive agent to lithium batteries?

The normal charging and discharging process of lithium batteries requires the participation of lithium ions and electrons. This requires that the electrodes of lithium-ion batteries must be mixed conductors of ions and electrons, and the electrode reaction can only occur at the junction of the electrolyte, conductive agent, and active material. The positive electrode active materials are mostly transition metal oxides or transition metal phosphates, which are semiconductors or insulators with poor conductivity, and conductive agents must be added to improve conductivity.

Nature Energy: Accurate monitoring of lithium battery status!

 

First author: Meng Li

Corresponding author: Boryann Liaw

Corresponding Unit: Idaho National Laboratory, USA

Achievements at a Glance

This study developed a novel non-destructive method to track the remaining amount of active lithium (Li) in lithium-ion batteries, similar to the fuel gauge in a car engine. By converting the theoretical capacity of transition metal oxides into lithium content analysis, the researchers were able to reliably track the lithium content in the electrode and reveal the impact of battery formulation and testing methods on performance. The study found that lithium content tracking was able to reveal stoichiometric changes near the electrode-electrolyte interface compared to capacity analysis.

By tracking four key variables from battery formation to end of life, the researchers used a thermodynamic framework to characterize electrode and battery performance. This precise lithium content utilization differential analysis is expected to enable more accurate battery engineering, evaluation, failure analysis and risk mitigation. This method may be applicable to all stages from battery cell design optimization, manufacturing to battery management, thereby improving battery performance and reliability.

Interfacial friction makes the vertical structure of lithium metal batteries

Interfacial friction makes the vertical structure of lithium metal batteries

summary

A practical high-energy-density lithium metal battery requires a free-standing lithium metal anode with a thickness of less than 20 μm, but it is difficult to achieve large-scale processing of thin layers and free-standing structures due to the low melting point and strong diffusion creep effect of lithium metal. In this study, a free-standing lithium chips with a thickness of 5 to 50 μm was formed on the lithium metal surface by mechanical rolling, which was determined by the in-situ tribochemical reaction between lithium and zinc dialkyl dithiophosphate (ZDDP). A layer of organic/inorganic hybrid interface (about 450 nm) was formed on the lithium metal surface with extremely high hardness (0.84 GPa) and Young's modulus (25.90 GPa), which not only enables scalable processing of lithium chips, but also realizes dendrite-free lithium metal anode by inhibiting dendrite growth. The rolled lithium anode has a long cycle life and high-rate cycling stability ( more than 1700 cycles at 25°C even at current densities of 18.0 mA cm −2  and 1.5 mA cm −2  ). This work provides a scalable tribological design approach for producing practical thin free-standing lithium metal anodes.

In-depth! Detailed explanation of lithium-ion battery formation technology

In-depth! Detailed explanation of lithium-ion battery formation technology

Lithium-ion battery production requires formation to achieve electrode wetting and full activation of electrode materials. During the first charge, as lithium ions are embedded in the negative electrode, the electrolyte components undergo a reduction reaction at the negative electrode to form a stable solid electrolyte interface film (SEI film) to prevent irreversible consumption of electrolyte and lithium ions in subsequent cycles.

Therefore, this technology is of extraordinary significance to battery performance. The effect of formation directly affects the subsequent performance of lithium-ion batteries, including storage performance, cycle life, rate performance and safety. This article focuses on the technical parameters/methods of formation and its impact on battery performance.

Why do electrodes crack during lithium battery coating? How to solve it?

1. Detailed reasons for the cracking of the pole piece

1. Slurry problem

   The slurry viscosity is not suitable:

     - Viscosity is too high: The slurry has poor fluidity, making it difficult to spread evenly during coating and prone to cracking.

     - Viscosity is too low: The slurry tends to flow, resulting in uneven coating thickness and cracking after drying.

  Uneven slurry dispersion:

     - Active materials, conductive agents and binders are not fully dispersed, resulting in local stress concentration.

     - Agglomerated particles exist in the slurry, forming weak points during coating.