TiNb2O7 Negative Electrode Orientation for Fast-Charging Batteries
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Solution Overview
Problem
Secondary batteries with carbon-based negative electrodes face issues such as rapid charge/discharge leading to metallic lithium precipitation, heat generation, and low energy density due to the limited lithium insertion sites and capacity, while titanium-based electrodes offer stability but have lower capacity and energy density.
Innovation Solution
A niobium-titanium composite oxide electrode with a monoclinic crystal structure, specifically TiNb2O7, is developed to enhance lithium ion diffusion and energy density, incorporating a conductive agent to improve electrical conductivity and using controlled pressing to optimize particle orientation for better input/output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based negative electrode is used, then the capacity per weight is high, but metallic lithium precipitation occurs during rapid charge/discharge
Solution Approach 1:
The patent uses a composite oxide material containing both titanium and niobium (Ti-Nb composite oxide) to combine the advantages of both elements. Titanium provides structural stability and prevents lithium precipitation, while niobium increases the capacity per weight. This composite approach resolves the contradiction by integrating two materials with complementary properties into a single electrode material.
Solution Approach 2:
The patent modifies the electrode potential parameter by using Ti-Nb composite oxide, which has a lower potential than pure titanium oxide. This parameter change allows the electrode to operate at a potential that prevents lithium precipitation while maintaining high capacity. The specific potential range achieved balances both stability and capacity requirements.
2Reliability
If an oxide of titanium is used in the negative electrode, then rapid charge/discharge can be stably performed, but the energy density is low
Solution Approach 1:
The patent creates a Ti-Nb composite oxide where niobium substitution in the titanium oxide lattice increases the capacity per weight from 165 mAh/g (pure TiO2) to over 380 mAh/g (TiNb2O7), while maintaining the structural stability and low potential characteristics that enable stable rapid charge/discharge.
Solution Approach 2:
The patent introduces niobium atoms at specific positions within the titanium oxide crystal lattice, creating local regions with enhanced lithium insertion capacity. This local modification allows different parts of the crystal structure to contribute differently to the overall performance, with some regions providing stability and others providing high capacity.
3Quantity of substance
If a general graphite based electrode material is used, then the capacity per weight is high, but the structure becomes unstable during rapid charge/discharge
Solution Approach 1:
The patent combines the high capacity characteristic of graphite-based materials with the structural stability of titanium oxide by creating a Ti-Nb composite oxide. The titanium-niobium oxide lattice provides a stable framework that can accommodate lithium ions during rapid charge/discharge without the structural degradation that occurs in graphite, while maintaining high capacity through niobium's contribution.
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 electrode achieves high charge/discharge capacity, stable rapid charging, and improved energy density by optimizing lithium ion diffusion and particle orientation, while maintaining electrical conductivity and preventing metallic lithium precipitation.
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
incorporating a conductive agent to improve electrical conductivity
Implementation Method 3
using controlled pressing to optimize particle orientation for better input/output characteristics
Data Source
AI summary
According to one embodiment, an electrode is provided. The electrode includes a current collector, and an active material-containing layer which is formed on a surface of the current collector and includes a plurality of niobium titanium composite oxide particles. A X-ray diffraction pattern using a Cu-Kα ray source with respect to a surface of the active material-containing layer includes a peak A with a highest intensity in a range of 2θ=26°±0.2° and a peak B with a highest intensity in a range of 2θ=23.9°±0.2°. An intensity ratio (Ia/Ib) between an intensity Ia of the peak A and an intensity Ib of the peak B is in a range of 1.80 or more to 2.60 or less.