Bimodal Niobium-Titanium Electrode for High Energy Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Secondary batteries with carbon-based negative electrodes face issues such as rapid degradation and low energy density due to lithium dendrite formation and limited lithium insertion sites, while titanium-based electrodes offer stability but lower capacity and energy density.
Innovation Solution
An electrode with a bimodal particle size distribution of monoclinic niobium-titanium composite oxide active material particles, where smaller particles are coated with a carbon layer for enhanced durability and larger particles are not, to improve electrode density and energy density while maintaining cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon-based negative electrode is used, then capacity per weight is improved, but reliability deteriorates due to lithium dendrite formation and rapid degradation
Solution Approach 1:
The negative electrode is segmented into two distinct particle size groups: small particles (0.3-2.0 μm) that are fully coated with carbon material to prevent dendrite formation, and large particles (2.0-10.0 μm) that remain uncoated to maintain high capacity. This segmentation allows each particle group to fulfill its specific function optimally.
Solution Approach 2:
Different regions of the electrode have different carbon coverage characteristics. Small particles have high carbon coverage (5-50 mass%) to ensure stability and prevent dendrites, while large particles have low or no carbon coverage to maintain high lithium insertion capacity. This local quality differentiation resolves the contradiction between safety and capacity.
2Reliability
If oxide of titanium is used in negative electrode, then reliability is improved with stable rapid charge-discharge, but energy density deteriorates due to lower capacity per weight
Solution Approach 1:
The invention changes the particle size parameter of the titanium oxide particles, creating a bimodal distribution with specific size ranges. Small particles provide stability for rapid charge-discharge, while large particles contribute high capacity, achieving both reliability and energy density improvement simultaneously.
3Quantity of substance
If niobium-titanium composite oxide is used, then capacity per weight is improved, but reliability deteriorates due to variable cycle life deterioration depending on particle size
Solution Approach 1:
The niobium-titanium composite oxide particles are segmented into two size groups with different carbon coverage treatments. Small particles are coated with carbon to prevent cycle life deterioration, while large particles remain uncoated to maintain high capacity, resolving the particle size-dependent reliability issue.
Solution Approach 2:
The invention uses a composite structure combining niobium-titanium composite oxide with carbon material coating. This composite approach enhances both capacity and cycle life by leveraging the high capacity of niobium-titanium oxide and the protective properties of the carbon coating.
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 approach results in a secondary battery with improved high energy density and cycle life characteristics by balancing the carbon coverage and particle size distribution, reducing side reactions and enhancing lithium ion insertion/extraction properties.
Implementation Method 1
a carbon material layer with which at least a part of surfaces of the core particles is coated
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
Implementation Method 4
the speed of deterioration of cycle life characteristics varies depending on the size of particles
Data Source
AI summary
According to one embodiment, an electrode is provided. The electrode includes the active material-containing layer formed on the current collector and including active material particles. The particle size distribution chart obtained by the laser diffraction scattering method for the active material particles includes the first region and the second region. The first particle group included in the first region includes the first active material particles, and the second particle group included in the second region includes second active material particles. The carbon coverage of the first particle group is higher than the carbon coverage of the second particle group.