Disordered Rocksalt Cathode Synthesis for Better Conductivity
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Solution Overview
Problem
Disordered rocksalt materials for lithium ion batteries suffer from poor conductivity, which limits their performance.
Innovation Solution
Forming disordered rocksalt materials by using a metal precursor compound in a lower oxidation state, such as manganese in the 2+ valence state, and controlling the annealing process to maintain small particle sizes through milling and controlled atmospheres, resulting in improved conductivity and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If disordered rocksalt materials are used as cathode materials, then energy density is improved, but conductivity deteriorates
Solution Approach 1:
The patent changes the oxidation state parameter of the metal precursor from higher states (e.g., Mn3+) to lower states (e.g., Mn2+). This parameter change in the precursor leads to smaller particle sizes after annealing, which improves conductivity while maintaining the high energy density of the disordered rocksalt structure. The lower oxidation state precursor creates a more reduced environment during synthesis, preventing excessive particle growth.
2Reliability
If particle size is reduced by milling, then conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary action by selecting metal precursors in lower oxidation states before the annealing process. This preliminary choice of precursor oxidation state pre-determines the particle size outcome, eliminating the need for subsequent milling steps. The smaller particle sizes are achieved inherently through the synthesis process itself, rather than requiring post-synthesis mechanical processing.
3Reliability
If metal precursor in lower oxidation state is used, then particle size is reduced and conductivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by focusing control on the specific property of the metal precursor (oxidation state) rather than attempting to control all parameters. By selecting precursors with specifically lower oxidation states (e.g., Mn2+ instead of Mn3+), the method achieves consistent small particle sizes through this localized control point, simplifying the overall manufacturing precision requirements.
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 method produces disordered rocksalt materials with enhanced metal redox capacity and improved cycle life, achieving higher energy density and conductivity compared to conventional methods.
Implementation Method 1
forming a mixture comprised of a Mn compound having an oxidation state greater than 2 with at least one other metal precursor compound in the absence of lithium compound to a temperature to form the precursor... This intermediate precursor formed is comprised of Mn having a reduced oxidation state of 2
Implementation Method 2
mixing a lithium compound with a metal precursor compound comprised of Mn having an oxidation state of 2 to form a mixture and heating the mixture to a temperature to form a disordered rocksalt structure
Implementation Method 3
controlling the annealing process to maintain small particle sizes through milling and controlled atmospheres
Data Source
AI summary
It has been discovered that improved disordered rocksalts comprise of Mn are made by method comprising mixing a lithium compound with a metal precursor compound comprised of Mn having an oxidation state of 2 to form a mixture and heating the mixture to a temperature to form a disordered rocksalt structure. The method may realize improved cycle life with altered metal and oxygen redox of the disordered rocksalt.