Silicon Anode Tar Coating to Suppress SEI in Li-Ion Batteries
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Solution Overview
Problem
The existing graphite-based negative active materials in lithium secondary batteries have limited theoretical capacity and suffer from performance deterioration due to volume changes in silicon-based alternatives, leading to issues like short circuits, electrode collapse, and rapid degradation of battery characteristics.
Innovation Solution
A manufacturing method involving coating a silicon-based negative active material precursor with crude tar or soft pitch, followed by annealing, to reduce the specific surface area and suppress the formation of the solid electrolyte interphase (SEI), thereby improving cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical energy treatment (ball milling) is applied to synthesize Li4Ti5O12, then homogeneous mixing and fine particle formation are achieved, but particle aggregation occurs and secondary reactions with milling media contaminate the product
Solution Approach 1:
The patent introduces a liquid medium (water or alcohol) as an intermediary during the mechanical energy treatment process. This liquid medium prevents direct contact between particles and milling media, thereby preventing particle aggregation and contamination while still allowing effective mixing and particle size reduction through ultrasonic vibration and mechanical impact.
2Strength
If conventional sintering is used to form Li4Ti5O12 particles, then dense particles are obtained, but particle size distribution becomes wide and secondary reactions occur
Solution Approach 1:
The patent changes the sintering parameters by conducting the process in a liquid medium (water or alcohol) at relatively low temperatures (900-1100°C) for short durations (1-10 hours). This parameter change prevents excessive particle growth and secondary reactions while still achieving dense particle formation through controlled sintering in the liquid environment.
3Stability of the object's composition
If Li4Ti5O12 is synthesized without Li2SiO3 glass coating, then particle aggregation is reduced, but particle strength decreases and sintering difficulty increases
Solution Approach 1:
The patent applies a thin layer of Li2SiO3 glass coating only on the surface of Li4Ti5O12 particles, creating a composite structure with different properties in different regions. The core maintains the spinel structure and electrochemical performance, while the surface coating provides enhanced strength and sintering resistance without causing significant aggregation.
4Strength
If Li2SiO3 glass is added to improve sinterability, then particle strength increases, but particle aggregation increases and Li4Ti5O12 content decreases
Solution Approach 1:
The patent uses a small, controlled amount of Li2SiO3 glass (1-10 wt%) as a sintering aid. This partial addition provides enough glass phase to enhance particle strength and improve sinterability, while limiting the amount to prevent excessive aggregation and maintain high Li4Ti5O12 content in the final product.
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 active material with a reduced specific surface area, enhancing the cycle-life characteristics and stability of lithium secondary batteries by minimizing SEI formation and maintaining electrical conductivity.
Implementation Method 1
irradiating ultrasonic waves to a mixture of LiO2 and TiO2 powders in a mixed solvent
Implementation Method 2
drying the mixture to obtain a dried powder
Implementation Method 3
sintering the dried powder in air at 900° C. to 1100° C. for 1 hour to 10 hours
Data Source
Figure 1
AI summary
The present invention is related to a manufacturing method of a negative active material for a lithium secondary battery, a negative active material for a lithium secondary battery manufactured by the method, and a lithium secondary battery including the same. According to one embodiment, it is provided that: a method of manufacturing a negative active material for lithium secondary battery, comprising: coating a negative active material precursor containing Si with crude tar or soft pitch; and annealing an obtained coating product, wherein, the crude tar contains a low molecular weight component that can be removed by a distillation process in an amount of 20 wt% or less.