Silicon Solid Solution Grain Boundary Doping for Battery Cycle Life
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Solution Overview
Problem
Conventional boron-containing silicon material powders for negative electrodes in nonaqueous secondary batteries inadequately improve charge/discharge cycle and rate characteristics.
Innovation Solution
A negative electrode active material with a silicon solid solution incorporating group 3, 4, or 5 elements on its crystal grain boundaries, produced through a process involving a mixed melt with a coolant, rapid boiling, and heat treatment to enhance electron conductivity and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing materials are used as negative electrode active material to increase discharge capacity, then discharge capacity is improved, but charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The invention applies local quality by concentrating group 3, 4, or 5 elements specifically at the crystal grain boundaries of silicon, rather than uniformly distributing them throughout the material. This localized positioning at grain boundaries provides protective effects that improve cycle characteristics while preserving the high capacity of silicon bulk material.
Solution Approach 2:
The invention creates a composite structure by incorporating multiple elements (group 3, 4, or 5 elements combined with silicon) to form a multi-component system. This composite approach combines the high capacity of silicon with the stabilizing effects of other elements, achieving both high discharge capacity and improved cycle characteristics.
2Reliability
If conventional boron-containing silicon material powders are used to improve cycle characteristics, then capacity loss is reduced, but charge/discharge rate characteristics remain insufficient
Solution Approach 1:
The invention changes the compositional parameters by incorporating group 3, 4, or 5 elements in addition to or instead of boron, and optimizes their concentrations and distributions. This parameter optimization enables simultaneous improvement of both cycle characteristics and rate characteristics by adjusting the chemical composition and spatial distribution of elements.
3Quantity of substance
If silicon material is used to achieve high discharge capacity, then capacity is improved, but electrode expansion increases
Solution Approach 1:
The invention applies local quality by positioning group 3, 4, or 5 elements at crystal grain boundaries, where they can locally constrain expansion and prevent structural degradation during charge/discharge cycles, thereby reducing overall electrode expansion while preserving bulk silicon capacity.
Solution Approach 2:
The invention implements beforehand cushioning by pre-introducing group 3, 4, or 5 elements into the silicon structure before electrochemical cycling begins. These elements act as preventive measures that cushion against expansion stresses during subsequent charge/discharge operations, reducing cumulative expansion damage.
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 silicon solid solution exhibits improved charge/discharge cycle characteristics, increased reversibility, and enhanced oxidation resistance, reducing electrode expansion and maintaining discharge capacity in high-temperature environments.
Implementation Method 1
introducing the mixed melt into a liquid coolant to form a vapor film covering the mixed melt in the coolant, rupturing the vapor film to bring the mixed melt and the coolant into direct contact to cause boiling as a result of spontaneous nucleation
Implementation Method 2
rupturing the vapor film to bring the mixed melt and the coolant into direct contact to cause boiling as a result of spontaneous nucleation
Implementation Method 3
rending and atomizing the mixed melt by making use of the pressure wave resulting from the boiling while cooling and solidifying the mixed melt to give a silicon solid solution
Implementation Method 4
heating the silicon solid solution at 500° to 1200° C. for 0.3 to 20 hours
Data Source
AI summary
A negative electrode active material for nonaqueous secondary batteries is disclosed. The active material contains a silicon solid solution having one or more than one of a group 3 semimetal or metal element, a group 4 semimetal or metal element except silicon, and a group 5 nonmetal or semimetal element incorporated in silicon as a solute element. The solute element is present more on the crystal grain boundaries of the silicon solid solution than inside the grains.