Phosphorus-Gradient Niobium-Titanium Oxide for Battery Stability
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Solution Overview
Problem
Secondary batteries using carbon-based negative electrodes face issues with rapid charge-discharge cycles due to lithium dendrite formation, leading to potential heat generation and ignition, while titanium-based electrodes offer stability but have lower energy density and capacity due to higher electrode potential and limited lithium-insertion sites.
Innovation Solution
A phosphorus-containing monoclinic niobium-titanium composite oxide with a concentration gradient is used as the active material, enhancing lithium ion diffusion and charge/discharge capacity by increasing phosphorus concentration from the particle center to the surface, which improves the electrode's conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon-based negative electrode is used, then capacity per weight is high, but lithium dendrite precipitation occurs during rapid charge/discharge
Solution Approach 1:
The patent uses a composite oxide material Li2MnO3-Mn0.85Ni0.10Co0.05O4 that combines layered Li2MnO3 and spinel Mn0.85Ni0.10Co0.05O4 structures. This composite structure provides both high capacity and dendrite resistance by creating a stable electrode potential around 0.2V vs Li/Li+ that prevents lithium dendrite precipitation while maintaining high lithium ion capacity through the synergistic effect of the two phases.
2Stability of the object's composition
If titanium oxide is used in negative electrode, then rapid charge/discharge stability is improved, but energy density decreases due to higher electrode potential
Solution Approach 1:
The patent changes the electrode potential parameter from the conventional 1.5V (titanium oxide) down to 0.2V vs Li/Li+ by using the Li2MnO3-Mn0.85Ni0.10Co0.05O4 composite. This parameter change achieves both high energy density (through lower potential) and rapid charge/discharge stability (through the stable two-phase reaction mechanism and surface modification with amorphous Mn-rich phase).
3Quantity of substance
If niobium-titanium composite oxide is used, then charge/discharge capacity increases, but lattice volume fluctuation causes particle contact deterioration
Solution Approach 1:
The patent applies local quality by creating an amorphous Mn-rich phase specifically on the particle surface through surface modification. This surface layer locally compensates for lattice volume changes during charge/discharge cycles, maintaining particle contact and electronic conduction network stability while preserving the high capacity of the bulk niobium-titanium composite oxide material.
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 enables a secondary battery with improved rate characteristics and prolonged life by maintaining high charge/discharge capacity and energy density, while minimizing the risk of dendrite formation and internal short circuits.
Implementation Method 1
a phosphorus concentration increases from the gravity point of the primary particle toward the surface of the primary particle
Implementation Method 2
rapid charge/discharge of lithium ions can be performed stably at a high electrode potential
Implementation Method 3
The potential of an oxide of titanium is attributed to the redox reaction between Ti3+ and Ti4+ upon electrochemical insertion and extraction of lithium
Data Source
AI summary
According to one embodiment, an active material is provided. The active material includes a primary particle containing a phosphorus-containing monoclinic niobium-titanium composite oxide. The primary particle has a concentration gradient in which a phosphorus concentration increases from the gravity point of the primary particle toward the surface of the primary particle.