Silicon Anode Pitch Coating Using Two-Solvent Deposition
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Solution Overview
Problem
Existing methods for preparing anode active materials for secondary batteries face challenges in achieving uniform and dense pitch coating layers, leading to poor initial discharge capacity, coulombic efficiency, and cycle life characteristics.
Innovation Solution
A method involving the use of two types of solvents to form a pitch coating layer on a composite material containing nano-silicon and amorphous carbon, or a graphite core surrounded by a nano-silicon-pitch shell, to enhance the uniformity and density of the coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pitch is pulverized to submicron size using physical friction, then the coating coverage is improved, but the silicon structure is easily damaged and pitch agglomeration occurs
Solution Approach 1:
The patent replaces the mechanical pulverization method (physical friction) with a chemical dissolution method. The pitch is dissolved in a solvent to form a solution, which is then coated onto the silicon particles. This substitution eliminates the mechanical damage to silicon structure while achieving uniform submicron-sized pitch distribution through the solution process.
Solution Approach 2:
The patent introduces a solvent as an intermediary substance to facilitate the coating process. The solvent dissolves the pitch to create a homogeneous solution that can be evenly distributed on silicon particles. After coating, the solvent evaporates, leaving behind a uniform pitch coating without the need for mechanical pulverization that causes damage.
2Ease of manufacture
If a single solvent is used in the wet method, then the process is simple, but coating uniformity deteriorates when solvent amount becomes insufficient
Solution Approach 1:
The patent segments the single solvent system into a two-solvent system. The first solvent (e.g., NMP or THF) dissolves the pitch effectively, while the second solvent (e.g., ethanol or acetone) adjusts the solution properties and ensures uniform coating. This segmentation allows each solvent to perform its specific function optimally, improving coating uniformity while maintaining process simplicity.
Solution Approach 2:
The patent changes the parameters of the solvent system by introducing a second solvent with different properties. The combination of solvents with complementary characteristics (different polarity, boiling points, and solubility parameters) enables better control over the coating process, ensuring uniform pitch distribution even when solvent amount varies.
3Ease of manufacture
If the pitch coating layer is formed using conventional methods, then the process is straightforward, but the coating density is insufficient
Solution Approach 1:
The patent applies preliminary action by thoroughly dissolving the pitch in the solvent mixture before coating. This pre-dissolution step ensures that the pitch is in a homogeneous molecular state, which then deposits as a dense, uniform coating on the silicon particles. The preliminary dissolution prevents agglomeration and ensures maximum packing density in the final coating layer.
Solution Approach 2:
The patent uses a composite solvent system consisting of two different solvents with complementary properties. This composite approach creates optimal coating conditions that result in higher coating layer density while maintaining ease of manufacture. The dual-solvent system provides better solubility and evaporation characteristics than a single solvent.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method improves the initial discharge capacity, initial coulombic efficiency, and cycle life characteristics of the secondary battery by ensuring a uniform and dense pitch coating layer.
Implementation Method 1
dissolving high softening point pitch in a first solvent to prepare a pitch solution
Implementation Method 2
adding a second solvent to the dispersion solution to precipitate the pitch on a composite containing the nano-silicon and the carbon-based conductive material to form a pitch coating layer
Implementation Method 3
removing the first solvent and the second solvent to obtain dry powders
Data Source
AI summary
According to a method for manufacturing an anode active material for a secondary battery of the present invention, in manufacturing an anode active material for a secondary battery, having: i) a structure in which a pitch coating layer is formed on a composite material comprising nano silicon and amorphous carbon; or ii) a structure of a graphite core and a nano silicon-pitch shell surrounding the core, a pitch coating layer is formed by using two types of solvent, thereby improving uniformity and density of the pitch coating layer. In addition, an anode material for a secondary battery, comprising the anode active material for a secondary battery of the present invention, can improve initial discharge capacity, initial coulombic efficiency, and cycle life characteristics of a secondary battery.