Heating coating machine is used for the doctor-blade coating of gel electrolyte films in zinc-ion batteries.

This article introduces the blade coating process for preparing gel electrolyte films for zinc-ion batteries using a heated coating mechanism. By controlling parameters such as temperature, coating speed, and gap height, this method can produce films with uniform thickness and smooth surfaces. The article details the complete process, from slurry preparation and equipment setup to coating operations and film curing, and analyzes key factors affecting film quality, such as slurry viscosity, heating temperature, and environmental humidity. Finally, the electrochemical and mechanical properties of the films are evaluated through characterization, and directions for future process optimization are discussed.

Introduction

In the research and development of energy storage devices, the preparation process of gel electrolyte films directly affects their electrochemical properties and mechanical properties. As a common wet coating technique, scraping can produce films with uniform thickness and flat surface, which is suitable for laboratory-scale material screening and process optimization. The heated film coating machine provides controllable and highly repeatable experimental conditions for the preparation of gel electrolyte films by integrating temperature control and mechanical scraping functions. This article will discuss the specific process, key parameters and effects on film quality of gel electrolyte films for zinc-ion batteries using a heated coating mechanism.

Equipment and principle

The heated coating machine usually consists of a heating platform, a scraper mechanism, a substrate fixture and a temperature control system. The working principle is as follows: the pre-prepared gel electrolyte slurry is placed on the substrate, and the slurry is maintained at a suitable temperature by heating the platform to control its rheological characteristics. Subsequently, move the scraper at a set speed so that the slurry spreads into a uniform wet film on the substrate; Subsequently, solid or gel films are formed through solvent volatilization or cross-linking reactions. The key to this process is the coordinated control of temperature, scraping speed and gap height.

Preparation process

The preparation process can be divided into four main stages: slurry preparation, equipment preparation, scraping operation, and film curing. First, the polymer matrix, zinc salts, plasticizers and solvents are mixed in specific proportions and stirred to form a homogeneous, bubble-free viscous slurry. The coater is then preheated to the target temperature and the clean substrate, such as glass or metal foil, is fixed on the heated platform. Use a thickness gauge to set the gap between the scraper and the substrate, which directly determines the thickness of the wet film. Place an appropriate amount of slurry in front of the scraper and start the equipment for one-way scraping. After scraping, the wet film is transferred along with the substrate to a controlled environment for drying or curing, and finally peeled off to obtain a self-supporting gel electrolyte film.

Key parameter analysis

The quality of the scraping process is affected by several parameters, the following are the main considerations:

Slurry viscosity	It affects the spreading uniformity and defect formation, which needs to be matched with the scraping speed.
Heating temperature	Adjust the volatilization rate of solvents and slurry fluidity, as too high a temperature may lead to premature geling.
Scraping speed	Too low speed is prone to streaks, and too high may lead to insufficient slurry supply.
Scraper gap	The thickness of the wet film is directly determined, and the drying shrinkage rate needs to be considered.
Ambient humidity	It affects the volatile kinetics of solvents and may cause surface unevenness.

These parameters need to be systematically optimized according to the specific slurry formulation. For example, wet film thicknessh_wetand dry film thicknessh_dryThe relationship can be approximated as:h_dry = h_wet × (1 - φ), where φ is the volume fraction of volatile components in the slurry.

Thin film characterization

The prepared gel electrolyte film needs to be characterized in series to evaluate its suitability. Common characteristics include: thickness measurement, multi-point measurement using a micrometer or thickness gauge to take the average; Surface topography observation, through optical microscopy or scanning electron microscopy to check for cracks, holes or contamination; electrochemical performance tests, such as ionic conductivity determination and electrochemical stability window testing; Mechanical properties such as tensile strength and flexibility testing. These data provide a basis for process adjustments and material improvements.

Applications and prospects

Gel electrolyte films prepared with heated coating machines can be used as electrode spacers or integrated electrode-electrolyte components in zinc-ion batteries. The thickness of the film prepared by this method is controllable and consistent, which is conducive to the contact of the internal interface of the battery and ion transport. In the future, we can explore higher precision temperature gradient control, multi-layer layered scraping process, and in-line curing technology adapted to different polymer systems to further improve film performance and process efficiency.

References

1. Review of gel electrolyte preparation technology, Transactions of the Chinese Society of Materials Science and Engineering, 2022.
2. Influence of wet coating process parameters on film uniformity, Journal of Chemical Engineering, 2021.
3. Research Progress on Electrolytes for Zinc-ion Batteries, Journal of Electrochemistry, 2023.
4. Laboratory Coating Equipment Operation Code, Laboratory Equipment and Technology, 2020.