Silicon Anode Composite With Silicate Matrix for Cycle Stability
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Solution Overview
Problem
Secondary batteries using silicon particles as negative electrode active materials face deterioration in charge/discharge cyclic characteristics due to large volume changes during charge/discharge reactions, leading to particle structure breakage.
Innovation Solution
A negative electrode active material comprising a silicate phase with Li, Si, and Mx, where Mx is an element other than alkali or alkaline earth metals, with silicon particles and oxide particles like Zr, Ce, Al, or Ti dispersed within, maintaining a Li content of 3-45 mol%, Si content of 40-78 mol%, and Mx content of 1-40 mol%, which prevents volume change and enhances ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to increase ion intercalation capacity, then the battery capacity is improved, but the charge/discharge cyclic characteristics deteriorate due to large volume changes causing particle structure breakage
Solution Approach 1:
The invention uses a composite material system consisting of silicon particles dispersed in a glassy phase matrix. The glassy phase acts as a binding medium that holds the silicon particles together, preventing particle structure breakage during volume changes while allowing silicon to maintain its high ion intercalation capacity. This composite structure resolves the contradiction between high capacity and cyclic stability.
Solution Approach 2:
The invention changes the physical and chemical parameters of the binding phase by using a glassy phase with specific composition (containing B2O3, SiO2, and other oxides) and controlled softening point (50-150°C). This parameter optimization allows the matrix to accommodate silicon's volume expansion/contraction without structural failure, maintaining both high capacity and good cyclic characteristics.
2Quantity of substance
If silicon particles undergo charge/discharge reactions to intercalate lithium ions, then the battery capacity increases, but the particle structure breaks due to large volume changes
Solution Approach 1:
The glassy phase matrix acts as a flexible shell surrounding the silicon particles. This shell can deform elastically to accommodate the volume changes of silicon during lithium ion intercalation and deintercalation, preventing particle structure breakage while maintaining the integrity of the composite electrode material.
Solution Approach 2:
The glassy phase serves as an intermediary between the silicon particles and the electrolyte, providing a mechanical framework that supports the silicon particles during volume changes. This intermediary structure prevents direct contact stresses that would cause particle breakage, while still allowing lithium ion transport.
3Productivity
If the glassy phase softening point is lowered to improve ion conductivity, then lithium ion migration becomes smoother, but the structural stability may be compromised
Solution Approach 1:
The invention optimizes the glassy phase composition to achieve a softening point within the specific range of 50-150°C. This parameter control allows the phase to be soft enough at operating temperature to provide good ion conductivity and flexibility, while remaining stable enough structurally to maintain particle integrity during cycling.
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 proposed solution effectively prevents the deterioration of charge/discharge cyclic characteristics by stabilizing the silicon particles' structure and ensuring smooth lithium ion migration, thereby enhancing the battery's performance and capacity retention.
Implementation Method 1
dispersion of silicon particles and predetermined metal oxide particles in a silicate phase having a predetermined component can prevent a volume change of the silicon particles due to the charge/discharge reaction
Implementation Method 2
ensuring smooth lithium ion migration
Data Source
Figure 1
AI summary
This negative electrode active material for a secondary cell which is one aspect of the present disclosure comprises: a silicate phase 11 that contains Li, Si, and Mx (Mx alkali metal, alkaline earth metal, and an element other than Si); silicon particles 12 dispersed in the silicate phase 11; and oxide particles 15 that contain Zr dispersed in the silicate phase 11. The content of each element with respect to the total of the elements other than oxygen in the silicate phase is 3 to 45 mol% for Li, 40 to 78 mol% for Si, and 1 to 40 mol% for Mx.