Disordered Rock Salt Cathode Materials for High Energy Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current disordered rock salt compositions for lithium ion battery cathodes face limitations in energy density, capacity retention, and rate performance, with prior art materials typically using stoichiometric lithium content of 1.4 or less, and lacking effective charge compensation and doping strategies.
Innovation Solution
The development of disordered rock salt compositions with increased lithium content, controlled 3d to 4d element ratios, and strategic doping, including fluorine substitution, to enhance electrochemical performance, specifically through formulas like LixNby−aNaMz−bPbO2−cFc, where 1.2<x≤1.75, 0≤y<0.55, 0.1<z<1, and 0≤a<0.5, 0≤b<1, 0≤c<0.8, with M, N, and P being specific transition metals and dopants, to improve lithium diffusion and oxygen stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If disordered rock salt structure is used to achieve high energy density, then theoretical energy density increases significantly, but capacity retention and rate performance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the lithium content (x) to be greater than 1.4 and adjusting the stoichiometric ratios of transition metals (M, Nb) to optimize electrochemical performance. This includes setting specific ranges for Li content and metal ratios to achieve both high energy density and good capacity retention
Solution Approach 2:
The patent creates a composite disordered rock salt structure combining multiple transition metals (M and Nb) with lithium in specific ratios. This composite approach leverages the complementary properties of different metals to achieve high energy density while maintaining structural stability and capacity retention
2Quantity of substance
If lithium content is increased to improve capacity, then energy density increases, but structural stability and oxygen release resistance worsen
Solution Approach 1:
The patent optimizes the lithium content parameter within a specific range (x > 1.4) to balance capacity enhancement with structural stability. This parameter optimization prevents excessive lithium that would cause oxygen release while maximizing the lithium content for high capacity
Solution Approach 2:
The patent introduces local quality variations through the disordered rock salt structure where lithium and transition metals are randomly distributed. This local structural variation allows high lithium content regions to coexist with stable metal-oxygen clusters that prevent oxygen release
3Ease of manufacture
If conventional stoichiometric ratios are used to simplify manufacturing, then ease of manufacture increases, but energy density and electrochemical performance deteriorate
Solution Approach 1:
The patent deviates from conventional stoichiometric ratios by setting lithium content x > 1.4 and optimizing metal ratios (M:Nb) to specific ranges. This parameter optimization achieves high energy density while maintaining relatively simple synthesis procedures through solid-state reaction
4Speed
If higher lithium content is used to improve rate performance, then lithium diffusion increases, but oxygen release and structural degradation worsen
Solution Approach 1:
The patent optimizes lithium content within a controlled range (x > 1.4) to enhance lithium diffusion kinetics while preventing oxygen release. This parameter control ensures that the increased lithium content improves rate performance without triggering structural degradation
Solution Approach 2:
The patent converts the potential harm of excess lithium (which could cause oxygen release) into a benefit by using the disordered rock salt structure. The random distribution of lithium and metals creates stable local environments that prevent oxygen release while maintaining high lithium content for fast diffusion
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 proposed compositions demonstrate improved energy density, capacity retention, and rate performance, with increased lithium content and controlled cation ratios leading to enhanced electrochemical characteristics, such as higher first cycle charge and discharge capacities and reduced oxygen release, compared to conventional disordered rock salt materials.
Implementation Method 1
improve lithium diffusion
Implementation Method 2
strategic doping, including fluorine substitution, to enhance electrochemical performance
Data Source
AI summary
A disorder rock salt composition for use as a cathode active material. The stoichiometry of the lithium, niobium, oxygen, and transition metal components of the disordered rock salt is varied to improved performance in an electrochemical cell while substantially maintaining the disordered rock salt crystallographic structure.