Silicon Anode Slurry Acidification for Viscosity and Cycle Stability
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face challenges due to high irreversible capacity and volume expansion, leading to reduced initial efficiency and lifespan, especially when metal-doped silicon oxides react with moisture and change the viscosity of the slurry.
Innovation Solution
A manufacturing method involving the preparation of a negative electrode slurry with silicon-based particles containing a Li compound, where an acid is added to control the pH between 10 and 12.5, forming a lithium silicate gel that increases porosity and stabilizes the phase, minimizing electrode deformation during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-doped silicon-based oxide is used as negative electrode active material, then capacity is improved, but the metal oxide reacts with moisture to increase pH and change slurry viscosity, deteriorating electrode state and charging/discharging efficiency
Solution Approach 1:
The patent controls the pH of the negative electrode slurry within a specific range (9.5 ≤ pH < 11.5) to prevent harmful side reactions between metal oxide and moisture while maintaining good slurry flowability and electrode formation. This parameter control resolves the contradiction by creating optimal conditions that preserve both capacity and charging/discharging efficiency.
Solution Approach 2:
The patent introduces an acid substance as an intermediary to regulate the pH of the slurry system. This acid substance mediates between the metal-doped silicon-based oxide and moisture, preventing direct harmful reactions while maintaining the beneficial high capacity characteristics of the doped material.
2Quantity of substance
If metal-doped silicon-based oxide is used as negative electrode active material, then capacity is improved, but slurry viscosity changes due to pH increase, deteriorating electrode state
Solution Approach 1:
The patent maintains pH within the range of 9.5 ≤ pH < 11.5 to stabilize slurry viscosity. By controlling this critical parameter, the patent prevents excessive thickening of the slurry that would occur at higher pH values, thereby maintaining both high capacity and stable rheological properties during electrode manufacturing.
3Speed
If silicon-based active material is used, then high-speed charging characteristics are improved, but volume expansion/contraction occurs, reducing initial efficiency and lifespan
Solution Approach 1:
The patent uses metal-doped silicon-based oxide as a composite active material that combines the high-speed charging characteristics of silicon with the structural stability provided by metal doping. This composite structure mitigates volume expansion/contraction while preserving fast charging capabilities, thereby extending electrode lifespan.
Solution Approach 2:
The patent optimizes the pH parameter of the slurry system to enhance the structural stability of the silicon-based active material during electrode formation. This parameter optimization helps reduce irreversible capacity loss from volume changes, improving both initial efficiency and long-term lifespan while maintaining high-speed charging characteristics.
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 charge/discharge capacity, initial efficiency, and lifespan of the negative electrode by suppressing side reactions, maintaining phase stability, and preventing electrode deformation through controlled pH and porosity creation.
Implementation Method 1
forming a lithium silicate gel that increases porosity and stabilizes the phase
Implementation Method 2
adding and mixing an acid to the preliminary negative electrode slurry, wherein the pH of the negative electrode slurry at 25° C. is 10 or more and less than 12.5
Implementation Method 3
forming a lithium silicate gel that increases porosity and stabilizes the phase, minimizing electrode deformation during charging and discharging
Implementation Method 4
the silicon-based active material has a disadvantage of having low initial efficiency due to a high degree of volume expansion/contraction according to charging and discharging
Data Source
AI summary
A manufacturing method of a negative electrode including steps of preparing a preliminary negative electrode slurry including a negative electrode active material and a conductive material; adding an acid to the preliminary negative electrode slurry and mixing to form a negative electrode slurry; applying the negative electrode slurry on at least one surface of a current collector and performing a first drying and rolling the slurry to form a negative electrode active material layer; and performing a second drying of the current collector on which the negative electrode active material layer is formed. The negative electrode active material includes silicon-containing particles including silicon and a Li compound. A pH of the negative electrode slurry at 25° C. is 10 or more and less than 12.5.