SiOx Negative Electrode Composition for Higher Initial Efficiency
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Solution Overview
Problem
Existing negative electrode active materials for lithium secondary batteries, particularly silicon-based oxides, face challenges with low initial efficiency due to high irreversible capacity and instability during charging and discharging, which affects the phase stability of the negative electrode slurry and reduces charge/discharge efficiency.
Innovation Solution
A negative electrode active material comprising silicon-based particles with SiOx (0<x<2) and a Li compound, where the Li compound includes predominantly crystalline lithium silicate (Li2SiO3) and optionally other lithium silicates, with a higher content of crystalline Li2SiO3 than crystalline Li2Si2O5 and Li4SiO4, ensuring a higher crystalline phase content than amorphous phase, which enhances phase stability and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silicon-based oxide (SiOx) is used as negative electrode active material, then capacity and high-speed charging characteristics are improved, but initial efficiency is reduced due to large volume expansion/contraction and large irreversible capacity
Solution Approach 1:
The patent uses a composite structure consisting of silicon-based oxide particles (SiOx where 0<x<2) combined with specific crystalline lithium silicate compounds (predominantly Li2SiO3). This composite material approach allows the silicon-based oxide to provide high capacity and fast charging characteristics while the crystalline lithium silicate component mitigates volume expansion and reduces irreversible capacity, thereby improving initial efficiency.
2Reliability
If metal (Li, Al, Mg) is doped into silicon-based oxide to reduce irreversible capacity, then initial efficiency is improved, but metal oxide reacts with moisture to increase pH and change viscosity of negative electrode slurry
Solution Approach 1:
The patent specifies precise compositional parameters for the lithium silicate compound, requiring it to contain Li, Si, and O in specific atomic ratios (Li:Si:O = 2:1:3 for Li2SiO3). By controlling the chemical composition and crystalline structure parameters, the material achieves improved initial efficiency while maintaining slurry stability, as the specific crystalline lithium silicate structure is less prone to reacting with moisture compared to other metal-doped silicon oxides.
3Stability of the object's composition
If crystalline lithium silicate (Li2SiO3) is predominantly formed in silicon-based particles, then phase stability of negative electrode slurry is improved and charge/discharge efficiency is enhanced, but manufacturing precision is required to control crystalline phase content
Solution Approach 1:
The patent defines specific compositional ranges and phase content ratios to achieve the desired performance. It specifies that the lithium silicate compound should contain crystalline Li2SiO3 as the predominant phase with specific atomic ratios (Li:Si:O = 2:1:3), and sets guidelines for the proportion of crystalline to amorphous phases. These parameter specifications provide clear manufacturing targets while ensuring the material achieves improved slurry stability and charge/discharge efficiency.
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 negative electrode active material significantly improves initial efficiency and service life characteristics by minimizing irreversible capacity and maintaining electrochemical stability during charging and discharging, while also preventing gas generation and viscosity changes in the negative electrode slurry, thus enhancing the overall quality and performance of the battery.
Implementation Method 1
maintaining electrochemical stability during charging and discharging
Implementation Method 2
enhances phase stability and charge/discharge efficiency
Data Source
AI summary
Disclosed are a negative electrode active material, a negative electrode including the same, a secondary battery including the same and a method for preparing the negative electrode active material. The negative electrode active material can include silicon-based particles including SiOx, wherein 0<x<2, and a Li compound, wherein the Li compound includes a crystalline lithium silicate including Li2SiO3, and optionally also including at least selected from the group consisting crystalline Li4SiO4 and crystalline Li2Si2O5, a content of the crystalline Li2SiO3 is higher than the sum of a content of the crystalline Li2Si2O5 and a content of the crystalline Li4SiO4, the content of the crystalline Li2SiO3 is included in an amount of 60 parts by weight or more based on 100 parts by weight of crystalline lithium silicate, and a total content of a crystalline phase present in the silicon-based particles is higher than a total content of an amorphous phase.