SiOx Negative Electrode Active Material for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries using silicon as a negative electrode material face challenges in achieving high battery capacity and cycle characteristics due to particle expansion, cracking, and low water resistance, leading to degraded battery performance and instability during electrode preparation.
Innovation Solution
A production method involving a silicon compound SiOx (0.5≤x≤1.6) with lithium insertion, followed by contact with a polycyclic aromatic compound solution and a quinoid structure-containing solution to desorb active lithium, stabilizing the electrode and preventing violent reactions, thereby enhancing cycle retention and initial efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to improve battery capacity, then the theoretical capacity increases significantly, but the particles expand and contract during charge/discharge causing cracking and degradation of cycle characteristics
Solution Approach 1:
The patent uses a composite structure where silicon particles are embedded in a silicon oxide matrix (SiOx where 0.5 ≤ x ≤ 1.6). This composite material allows the silicon to provide high capacity while the silicon oxide matrix constrains volume expansion and prevents particle cracking during charge/discharge cycles, thereby maintaining cycle characteristics.
Solution Approach 2:
The silicon oxide matrix acts as a flexible constraint structure that accommodates the expansion and contraction of silicon particles during lithium insertion and extraction. This matrix structure prevents the silicon particles from cracking while allowing the necessary volume changes for electrochemical reactions.
2Productivity
If lithium is inserted into the silicon compound to improve initial efficiency, then the initial charge/discharge efficiency increases, but the water resistance decreases leading to violent reactions with water
Solution Approach 1:
The patent optimizes the oxygen content parameter in SiOx (where 0.5 ≤ x ≤ 1.6) to balance two competing requirements: sufficient lithium insertion capability for high initial efficiency and adequate water resistance to prevent violent reactions. By controlling the stoichiometry of silicon oxide, the material achieves both high productivity and safety.
Solution Approach 2:
The patent creates local quality differentiation where lithium is preferentially inserted into specific regions of the silicon compound while maintaining an oxygen-rich environment in other regions. This localized lithium insertion, controlled by the SiOx matrix structure, enhances initial efficiency while the oxygen-rich regions maintain water resistance and prevent violent reactions.
3Reliability
If the oxygen content in silicon compound is increased to improve cycle characteristics, then the structural stability improves, but the lithium insertion capability decreases reducing initial efficiency
Solution Approach 1:
The patent identifies and optimizes the critical parameter x in SiOx (where 0.5 ≤ x ≤ 1.6) to achieve the optimal balance between cycle characteristics and initial efficiency. This parameter optimization allows sufficient oxygen content for structural stability while maintaining enough silicon character for lithium insertion capability.
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 results in a negative electrode active material with improved high capacity, cycle characteristics, and reduced irreversible capacity, preventing degradation and ensuring stable battery performance even under low humidity conditions.
Implementation Method 1
inserting lithium into the silicon compound
Implementation Method 2
making the silicon compound into which the lithium has been inserted contact with a solution B containing a polycyclic aromatic compound or a derivative thereof or both thereof... making the silicon compound that has been contacted with the solution B contact with a solution C... containing a compound having a quinoid structure in a molecule as a solute
Data Source
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AI summary
The present invention provides a production method of a negative electrode active material containing a silicon compound (SiOx: 0.5≤x≤1.6) that contains Lithium comprising: making a silicon compound into which the lithium has been inserted contact with a solution B containing a polycyclic aromatic compound or a derivative thereof or both thereof (here, the solution B contains one or more kinds selected from an ether-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, and an amine-based solvent as a solvent); and making the silicon compound contact with a solution C (here, the solution C contains one or more kinds selected from an ether-based material, a ketone-based material, and an ester-based material as the solvent, and contains a compound having a quinoid structure in a molecule as a solute). Thereby, a production method of a negative electrode active material for nonaqueous electrolyte secondary batteries capable of increasing a battery capacity and improving the cycle characteristics is provided.