Nb2TiO7 Composite Anode for Rapid Charge Safety
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Solution Overview
Problem
Secondary batteries, particularly those with carbon-based negative electrodes, face issues with rapid charge/discharge leading to metallic lithium dendrite precipitation, heat generation, and ignition due to internal short circuits, while titanium oxide negative electrodes offer stability but have low energy density and capacity per weight.
Innovation Solution
A niobium-titanium composite oxide active material comprising an Nb2TiO7 phase and at least one Nb-rich phase, such as Nb10Ti2O29, Nb14TiO37, or Nb24TiO64, is used, which stabilizes lithium insertion and maintains electric neutrality, enhancing energy density and over-charge resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon-based negative electrode is used, then capacity per weight is high, but rapid charge/discharge causes metallic lithium dendrite precipitation and safety issues
Solution Approach 1:
The patent uses a composite oxide material containing both titanium (Ti) and niobium (Nb) elements in specific ratios (Ti: 20-40 wt%, Nb: 60-80 wt%). This composite structure combines the high capacity characteristics of carbon-based materials with the safety and stability of titanium oxide, eliminating dendrite formation while maintaining acceptable energy density.
2Reliability
If titanium oxide negative electrode is used, then rapid charge/discharge stability is improved, but energy density and capacity per weight are reduced
Solution Approach 1:
The patent optimizes the compositional parameters by controlling the Ti and Nb content ratios (Ti: 20-40 wt%, Nb: 60-80 wt%) and particle size parameters (D10: 3-7 μm, D50: 7-13 μm, D90: 13-25 μm). These parameter changes enable the material to achieve both high rapid charge/discharge stability and improved energy density compared to conventional titanium oxide.
3Quantity of substance
If niobium-titanium composite oxide is used, then energy density is improved, but capacity balance between positive and negative electrodes collapses during charge/discharge cycles
Solution Approach 1:
The patent precisely controls the Ti/Nb ratio and particle size distribution parameters to optimize the electrochemical performance. The specific composition range (Ti: 20-40 wt%, Nb: 60-80 wt%) and particle size range (D50: 7-13 μm) ensure stable capacity balance between electrodes during cycling while maintaining high energy density.
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 niobium-titanium composite oxide material achieves high weight energy density, improved over-charge resistance, and extended cycle life by regulating lithium ion flow and reducing electrode potential, thereby addressing the limitations of titanium oxide electrodes.
Implementation Method 1
The potential of an oxide of titanium is attributed to the redox reaction between Ti3+ and Ti4+ upon electrochemical insertion and extraction of lithium
Implementation Method 2
stabilizes lithium insertion and maintains electric neutrality, enhancing energy density and over-charge resistance
Data Source
AI summary
An active material includes an Nb2TiO7 phase and at least one Nb-rich phase selected from an Nb10Ti2O29 phase, an Nb14TiO37 phase, and an Nb24TiO64 phase. The active material satisfies a peak intensity ratio represented by the following Formula (1): 0<IB/IA≤0.25 (1). In Formula (1), IA is a peak intensity of the maximum peak attributed to the Nb2TiO7 phase and appealing at 2θ of 26.0±0.1° in a wide angle X-ray diffraction pattern under CuKα rays as an X-ray source, and IB is a peak intensity of the maximum peak attributed to the at least one Nb-rich phase and appearing at 2θ of 24.9±0.2° in the diffraction pattern.