Li Silicate Silicon Anode Material for Slurry Stability and Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode material face challenges in achieving initial charge-discharge characteristics and cycle stability equivalent to carbon-based active materials, with modified silicon oxide exhibiting low water resistance and slurry instability.
Innovation Solution
A negative electrode active material comprising silicon compound particles with Li2SiO3 and Li2Si2O5, characterized by specific peaks in the XANES spectrum and a cristobalite-type structure, which improves battery capacity and slurry stability by reducing irreversible capacity and suppressing gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to improve battery capacity, then the battery capacity increases significantly, but the negative electrode active material expands or shrinks during charging and discharging, making it easy to break and reducing cycle characteristics
Solution Approach 1:
The patent applies the nesting principle by forming a core-shell structure where silicon particles are embedded within a silicon oxide matrix. The silicon core provides high capacity while the silicon oxide shell constrains volume expansion and prevents particle breakage during charging-discharging cycles, thus maintaining structural integrity and cycle stability.
Solution Approach 2:
The patent uses composite materials by combining silicon and silicon oxide in a controlled structure. The composite consists of silicon particles (for high capacity) dispersed in or coated with silicon oxide (for structural stability), creating a material that balances high capacity with mechanical strength and cycle durability.
2Reliability
If modified silicon oxide is used to improve cycle characteristics, then the structural stability improves, but the water resistance decreases and slurry stability becomes poor
Solution Approach 1:
The patent applies local quality by controlling the oxygen content and distribution specifically in regions near the current collector interface. The silicon oxide is modified to have lower oxygen content (0.8≤x<1.5) in the bulk but maintains appropriate properties at the interface, providing both structural stability for cycling and compatibility with the electrolyte for slurry stability.
Solution Approach 2:
The patent changes the chemical composition parameter of silicon oxide by controlling the oxygen-to-silicon ratio (0.8≤x<1.5) and adjusting the oxygen content gradient through the particle structure. This parameter optimization simultaneously improves cycle characteristics while maintaining water resistance and slurry stability.
3Quantity of substance
If the surface layer of negative electrode active material breaks and new surface is created, then the reaction area increases, but the electrolyte decomposition reaction increases and consumes electrolyte, reducing cycle characteristics
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable silicon oxide shell around silicon particles before battery assembly. This pre-formed protective layer prevents premature surface breakage and electrolyte decomposition during electrode manufacturing and initial charging cycles, reducing electrolyte consumption while still allowing adequate Li-ion diffusion.
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 enhances the first-time efficiency, capacity, and stability of the slurry, allowing for the production of high-capacity batteries with improved charge-discharge characteristics and extended cycle life.
Implementation Method 1
silicon compound particles each containing a silicon compound that contains oxygen... which has been inserted and released Li
Implementation Method 2
in a Si K-edge spectrum obtained from a XANES spectrum: a peak P which is derived from the Li silicate and located near 1847 eV; and a peak Q which is gentler than the peak P and located near 1851 to 1852 eV
Data Source
AI summary
The present invention is a negative electrode active material containing negative electrode active material particles. The negative electrode active material particles include silicon compound particles each containing an oxygen-containing silicon compound. The silicon compound particle contains at least one of Li2SiO3 and Li2Si2O5. The silicon compound particle has, in a Si K-edge spectrum obtained from a XANES spectrum: a peak P derived from the Li silicate and located near 1847 eV; and a peak Q gentler than the peak P and located near 1851 to 1852 eV. This provides a negative electrode active material that is capable of stabilizing a slurry when the negative electrode active material is used for a secondary battery, and capable of increasing the battery capacity by improving the initial efficiency.