Silicon-Silicate Anode Composite for Cycle-Stable Li-Ion Batteries
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Solution Overview
Problem
The silicon particles in negative electrode active materials for non-aqueous electrolyte secondary batteries experience significant volume changes during charging and discharging, leading to particle breakage and electrical isolation, which severely deteriorate the charge and discharge cycle characteristics of the batteries.
Innovation Solution
A negative electrode active material is developed containing a silicate-containing complex with a carbon phase and Si-containing silicate particles dispersed in the carbon phase. The Si-containing silicate particles have a silicate phase with dispersed silicon particles, and the ratio of the average particle diameter of the silicate-containing complex to the Si-containing silicate particles is between 15 and 120, which helps to suppress particle breakage and electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to achieve high theoretical capacity density, then energy density is improved, but particle breakage occurs due to large volume change during charging and discharging
Solution Approach 1:
The patent employs a nested structure where silicon particles are embedded within silicate phase particles, which are in turn dispersed in a carbon phase matrix. This multi-level nesting (silicon inside silicate, silicate inside carbon composite) allows the silicon particles to undergo volume changes during lithiation/delithiation while being constrained and protected by the surrounding silicate and carbon phases, preventing particle breakage while maintaining high capacity density
Solution Approach 2:
The patent creates a composite material system consisting of three phases: silicon particles (active material), silicate phase (buffer matrix), and carbon phase (outer matrix). This composite structure combines the high capacity of silicon with the volume stability of silicate and carbon phases, resolving the contradiction between achieving high energy density and maintaining particle integrity during cycling
2Manufacturing precision
If the particle size of silicate-containing complex is reduced to improve dispersion, then manufacturing precision is improved, but particle breakage is accelerated
Solution Approach 1:
The patent performs preliminary action by pre-forming the silicate phase matrix around silicon particles before final dispersion in the carbon phase. This pre-encapsulation creates a protective shell that prevents particle breakage during subsequent handling and processing, allowing for good dispersion without sacrificing particle integrity
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
This configuration effectively suppresses the deterioration of charge and discharge cycle characteristics by reducing particle breakage and maintaining electrical connectivity, thereby enhancing the overall performance and longevity of the non-aqueous electrolyte secondary batteries.
Implementation Method 1
Since the silicon particles have a large volume change associated with charging and discharging, particle breakage occurs in the negative electrode active material containing the silicon particles
Implementation Method 2
particle breakage occurs in the negative electrode active material containing the silicon particles, and the negative electrode active material is likely to be electrically isolated from the negative electrode
Data Source
AI summary
This negative electrode active material for a nonaqueous electrolyte secondary battery is characterized: by comprising a silicate-containing complex having a carbon phase and a plurality of Si-containing silicate particles dispersed in the carbon phase; and in that the Si-containing silicate particles each have a silicate phase and a plurality of silicon particles dispersed in the silicate phase, and the ratio (B/A) of the average particle diameter (B) of the silicate-containing complex with respect to the average particle diameter (A) of the Si-containing silicate particles is 15-120 inclusive.