Li-Containing Silicon Oxide Powder Uniform Doping
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Solution Overview
Problem
Existing methods for producing Li-containing silicon oxide powders for lithium ion secondary batteries result in the formation of both water-insoluble and water-soluble lithium silicate phases, leading to lithium elution and reduced cycle properties, due to non-uniform reaction processes during Li-doping, which is exacerbated by the large particle size difference between the silicon oxide and lithium sources.
Innovation Solution
The method involves finely grinding the lithium source to match the particle diameter of the silicon oxide powder, ensuring uniform Li-doping and inhibiting local lithium concentration, with calcination temperatures between 300°C and 800°C, and optionally incorporating a conductive carbon coating to enhance electrical conductivity and prevent disproportionation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Li-doping is performed to improve initial efficiency, then initial efficiency is improved, but water-soluble lithium silicate phases (Li2SiO3 and Li4SiO4) are formed causing lithium elution
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Li/O atomic ratio within 0.67-1.0 and adjusting calcination temperature (300-800°C) and time (1-48 hours) to transform the lithium silicate phase composition. These parameter adjustments enable the formation of water-insoluble Li2Si2O5 while suppressing water-soluble Li2SiO3 and Li4SiO4, thereby resolving the contradiction between improving initial efficiency and preventing lithium elution.
Solution Approach 2:
The patent applies local quality by creating a uniform distribution of lithium compounds throughout the silicon oxide powder matrix. Through controlled Li-doping and calcination, the lithium is evenly distributed as water-insoluble Li2Si2O5 phases rather than concentrated local regions of water-soluble lithium silicates, preventing localized lithium elution while maintaining overall initial efficiency improvement.
2Quantity of substance
If powder calcining-based Li-doping is used to form lithium silicate, then Li-doping is achieved, but non-uniform reaction occurs leading to mixed lithium silicate phases
Solution Approach 1:
The patent applies preliminary action by pre-mixing the silicon oxide powder with lithium compounds (such as Li2CO3, LiOH, or LiH) before calcination. This preliminary uniform distribution of lithium sources ensures that during subsequent calcination, the reaction proceeds uniformly throughout the powder matrix, producing consistent Li2Si2O5 phases without forming mixed lithium silicate compositions.
Solution Approach 2:
The patent uses parameter changes by optimizing the Li/O atomic ratio to 0.67-1.0 and controlling calcination conditions (temperature 300-800°C, time 1-48 hours) to achieve complete and uniform transformation to Li2Si2O5 phase. These precise parameter controls prevent the formation of intermediate or mixed phases, ensuring manufacturing precision in phase composition.
3Ease of operation
If crystallization of lithium silicate is promoted to improve handlability, then water reactivity is reduced, but crystalline Si forms adversely affecting cycle properties
Solution Approach 1:
The patent applies parameter changes by carefully controlling calcination temperature (300-800°C) and time (1-48 hours) to achieve crystallization of lithium silicate as Li2Si2O5 without reaching conditions that would cause silicon crystallization. This precise parameter control allows the material to gain the handling benefits of crystallization (water insolubility) while avoiding the harmful formation of crystalline Si that would degrade cycle properties.
Solution Approach 2:
The patent applies composite materials by creating a composite structure where crystallized Li2Si2O5 phases are embedded within an amorphous silicon oxide matrix. This composite configuration allows the lithium silicate to crystallize for improved handlability while the surrounding amorphous silicon oxide prevents silicon crystallization, thereby maintaining good cycle properties.
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
This approach produces Li-containing silicon oxide powders with predominantly crystallized Li2Si2O5 and minimal crystalline Si, reducing lithium elution and improving initial efficiency and cycle properties by ensuring uniform Li-doping and preventing the formation of reactive Li2SiO3 and crystalline Si.
Implementation Method 1
The method involves finely grinding the lithium source to match the particle diameter of the silicon oxide powder, ensuring uniform Li-doping
Implementation Method 2
with calcination temperatures between 300°C and 800°C, and optionally incorporating a conductive carbon coating
Data Source
AI summary
There is produced a Li-containing silicon oxide powder containing a crystallized lithium silicate that is mostly water-insoluble Li2Si2O5 and containing little crystalline Si. This object is attained through the mixing of a lower silicon oxide powder represented by a compositional formula SiOx (0.5<x<1.5) with a powdered lithium source that involves grinding of the powdered lithium source; controlling a median diameter D1 of the lower silicon oxide powder and a median diameter D2 of the powdered lithium source so as to fulfill 0.05≤D2/D1≤2; and calcining the mixed powder at 300° C. or higher and 800° C. or lower.