Lithium-Doped SiOx Anode Material for High-Capacity Cycle Stability
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Solution Overview
Problem
Conventional lithium secondary batteries using graphite-based materials have low energy density due to low theoretical capacity, while Si-based materials face issues with large volume expansion and low initial coulombic efficiency, making them unsuitable for practical applications.
Innovation Solution
A lithium-doped silicon-based oxide negative electrode active material is developed, with controlled crystallinity and optimized through a Li pretreatment process to improve battery stability and efficiency by adjusting the ratio of specific reversible and irreversible phases, using silicon oxide and lithium silicates like Li2SiO3 and Li2Si2O5, and suppressing crystalline silicon growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based material is used as negative electrode active material, then theoretical capacity is improved (3580 mAh/g), but volume expansion occurs (～400%) leading to deteriorated battery life characteristic
Solution Approach 1:
The patent uses SiOx material as a composite negative electrode active material that combines silicon oxide with conductive carbon materials. This composite structure provides high theoretical capacity while the carbon matrix constrains volume expansion, thereby improving battery life characteristic
Solution Approach 2:
The patent changes the oxidation state parameter of silicon from Si (0) to SiOx (+4), which fundamentally alters the volume expansion behavior. Silicon oxide exhibits significantly lower volume expansion during lithium insertion/extraction compared to pure silicon, thus maintaining reliability while preserving high capacity
2Reliability
If SiOx material is used as negative electrode active material, then volume expansion rate is reduced, but initial coulombic efficiency becomes low due to formation of irreversible phase
Solution Approach 1:
The patent performs preliminary lithium insertion into SiOx before battery assembly through controlled reaction with lithium metal or lithium compounds. This preliminary action pre-forms the lithium silicate phase, reducing the amount of irreversible phase formation during initial battery cycling and thereby improving initial coulombic efficiency
Solution Approach 2:
The patent creates local lithium-rich regions within the SiOx structure through controlled partial reduction or surface treatment. These local regions serve as lithium reservoirs that can rapidly supply lithium during initial cycling, improving initial efficiency without compromising the overall structural stability
3Quantity of substance
If Li pretreatment is performed on silicon-based oxide, then initial efficiency is improved, but crystallinity of silicon-based oxide increases which may affect performance
Solution Approach 1:
The patent carefully controls the temperature parameter during Li pretreatment, maintaining it below the crystallization temperature of SiOx. By changing the thermal parameter within an optimal range, the patent achieves lithium insertion for improved initial efficiency while preventing unwanted crystallization that would harm electrochemical performance
Solution Approach 2:
The patent employs periodic or cyclic Li pretreatment processes with multiple stages of lithium insertion and removal. This periodic action allows controlled modification of the SiOx structure to improve initial efficiency while the rest periods prevent excessive crystallization, maintaining the desired amorphous or microcrystalline structure
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 solution enhances battery capacity, improves initial efficiency, and extends the life of the battery by mitigating volume expansion and crystalline silicon growth, resulting in improved discharge capacity and stability.
Implementation Method 1
a negative electrode for a lithium secondary battery, and a lithium secondary battery
Implementation Method 2
a negative electrode for a lithium secondary battery, and a lithium secondary battery
Data Source
AI summary
Provided are a negative electrode active material which includes negative electrode active material particles which includes a silicon oxide (SiOx, 0<x≤2); and at least one lithium silicate selected from Li2SiO3, Li2Si2O5, and Li4SiO4 in at least a part of the silicon oxide. A signal generated in a region of 200 to 600 cm−1 according to a Raman spectrum is subjected to deconvolution into three peaks, which are set to peak A, peak B, and peak C from lowest to highest of an absolute value of a wavenumber. Also disclosed are a method of preparing the same, and a negative electrode and a lithium secondary battery including the negative electrode active material.