Comparative Study of Titanium 32×MXene Coated Carbon Electrodes and Thermally Treated Carbon Electrodes for Vanadium Redox Flow Batteries in RSC Advances

1.Research Background

A major challenge in vanadium redox flow batteries is the competition between the main and side reactions of hydrogen evolution associated with the V(II)/V(III) redox couple at the negative electrode.

Lithium Battery Negative Electrode Lithium Deposition Causes and Solutions

1.What is Lithium Deposition on the Negative Electrode?

The lithium intercalation potential of graphite is between 65–200 mV (vs. Li+/Li0). When the potential of the negative electrode approaches or drops below the deposition potential of metallic lithium, lithium ions will be deposited as metallic lithium on the surface of the negative electrode. Experiments have shown that during the charging process, some lithium ions are deposited as metallic lithium on the surface of the negative electrode, while the remaining lithium ions intercalate into the graphite or other negative electrode materials. During discharge, both ion de-intercalation and the stripping of deposited lithium metal occur simultaneously. In the process of lithium metal stripping, "dead lithium" is formed.

In short, the phenomenon of lithium deposition on the negative electrode refers to the simultaneous intercalation and deposition of lithium ions during the charge and discharge processes, causing lithium to deposit as metallic lithium on the surface of the negative electrode, and resulting in the formation of "dead lithium" that cannot be reused.

Design of Electrolyte for Achieving 4.8V-Class NCM811-Lithium Metal Batteries in Angew

1.Research Abstract

Combining high-voltage nickel-rich cathodes with lithium metal anodes is one of the most promising approaches to achieving high-energy-density lithium batteries. However, most current electrolytes cannot simultaneously meet the requirements for compatibility with lithium metal anodes and tolerance for ultra-high-voltage NCM811 cathodes. In this study, by adjusting the composition of fluorinated carbonate-based electrolytes, an ultra-anti-oxidative electrolyte was designed. The research found that through the synergistic decomposition of fluorinated solvents and PF6- anions, an SEI (solid electrolyte interphase) rich in LiF and Li2O was constructed on the lithium anode, which facilitated smooth deposition of lithium metal. More importantly, this electrolyte exhibited excellent antioxidant properties, enabling Li||NCM811 coin cells to maintain 80% of their capacity after 300 cycles at an ultra-high cut-off voltage of 4.8 V. Furthermore, under harsh conditions of high cathode loading (30 mg cm-2), low N/P ratio (1.18), and lean electrolyte (2.3 g Ah-1), a 4.8 V-class lithium metal pouch cell with an energy density of 462.2 Wh kg-1 could stably cycle for 110 times.

1. Key Factors Influencing Formation: Mechanism

1. Basic Concepts of Formation

1.1. What is Formation?

l Formation refers to the process of activating the cathode and anode materials inside a battery after it has been fully rested following electrolyte injection. This activation is achieved through a specific charging and discharging cycle, which also leads to the formation of a SEI (Solid Electrolyte Interphase) film on the surface of the active materials. The SEI film helps to improve the overall performance of the battery in terms of charging and discharging, self-discharge, and storage capabilities.

Lithium-ion Full Battery Manufacturing Process Training--Coating

1.Coating Basics

Purpose: To uniformly coat a fluid slurry onto the surface of a metal foil, dry it, and produce a battery electrode

Principle: The coating roller rotates to carry the slurry, and the amount of slurry transferred is adjusted by adjusting the gap between the doctor blade and the roller. The relative rotation of the back roller and the coating roller is used to transfer the slurry onto the substrate. Subsequently, the solvent in the slurry is evaporated through drying and heating, causing the solid matter to adhere to the substrate.

Lithium-ion Full Battery Manufacturing Process Training--Coating 2

1.Electrode Shedding

Negative electrodes are prone to powder shedding

Main reason：

1.Formula issues,insufficient bonding strength leading to material loss

2.Excessive baking temperature,rapid solvent evaporation resulting in SBR

bleeding.Insufficient adhesive between the material and the current collector leading to material loss

Lithium-ion Full Battery Manufacturing Process Training--Coating 3

1.Coating Basics

Purpose：To uniformly coat a fluid slurry onto the surface of a metal foil, dry it, and produce a battery electrode

Principle:The coating roller rotates to carry the slurry, and the amount of slurry transferred is adjusted by adjusting the gap between the blade and the roller. The relative rotation of the back roller and the coating roller is used to transfer the slurry onto the substrate. Subsequently, the solvent in the slurry is evaporated through drying and heating, causing the solid matter to adhere to the substrate.

Lithium-ion Full Cell Manufacturing Process

1.The function of adhesives

Cathode and anode slurries：

Provide viscosity to ensure that particles in the slurry do not easily settle and maintain sslurry stability

Provide viscosity for good fluidity

Provide viscosity to facilitate effective dispersion of materials

Lithium-ion Full Cell Manufacturing Process Training--Soft-Pack Battery Cell Encapsulation

1.Baking

1.1.The main purpose of baking is to remove moisture from the bare cell

H2O can cause the decomposition of LiPF6, leading to an increase in HF levels:

H2O can react with organic solvents in the electrolyte to produce alcohol and CO2, for example:

During the formation process, H2O can decompose, producing H2, consuming lithium ions,

reducing the initial efficiency and capacity of the battery, and damaging the battery interface.

Lithium-ion Full Cell Manufacturing Process Training--Baking and electrolyte injection

1.Rolling Principle

Roll pressing is a process that utilizes a roll press machine (as shown in Figure 1,the roll press machine used in the industry consists of three core components: a pair of rollers, an unwinding device, and a rewinding device) to compress the thickness of the electrode (as shown in Figure 1). This compression increases the compaction density of the electrode coating, reduces the thickness of the electrode, and ultimately enhances the energy density of the battery.

Lithium-ion Full Battery Manufacturing Process Training--Rolling

1.Process Flow

The main components of a lithium battery include a positive electrode with an active material typically being lithium cobalt oxide, a separator made of PP or PE composite membrane, a negative electrode with carbon as the active material, organic electrolyte, and a battery case made of aluminum-plastic composite film. The manufacturing process involves slurry preparation, film coating, assembly, and formation. In recent years, electronic products have become increasingly thinner and lighter, with faster charging speeds and reduced space, resulting in higher demands for the energy density of lithium batteries. Lithium batteries need to be continuously updated and improved to meet these demands, further trending towards smaller, lighter, and thinner batteries. The related topics of lithium batteries have always been a hot research focus. Adopting suitable materials and cell manufacturing processes can improve battery performance. For specific materials and processes, please consult Canrd!

Lithium-ion Full Cell Manufacturing Process Training--Summary of Processes

1.Role and Selection Criteria of Separators

1.1.Role of Separator

1) The separator is an important component of lithium-ion batteries.

2) Electronic insulation and ionic conductivity.

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