Cation-Disordered Lithium Oxides for High-Capacity Battery Cathodes
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Solution Overview
Problem
Current lithium ion batteries face limitations in achieving high energy density and capacity due to the poor electrochemical performance of existing lithium transition metal oxides, which are hindered by the inability to maintain redox-active species at lower oxidation states with lithium excess, leading to reduced charge capacity.
Innovation Solution
A cation-disordered lithium metal oxide with a formula LiaMbM′cO2 is developed, incorporating a redox-active species with multiple oxidation states and a charge-compensating species, allowing for a lithium excess that forms a percolating network of diffusion pathways, thereby maintaining the redox-active species at a lower oxidation state and enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium excess is introduced to increase charge capacity, then the charge capacity improves, but the redox-active species oxidation state increases leading to reduced electrochemical performance
Solution Approach 1:
A charge-compensating species acts as an intermediary between the lithium excess and the redox-active species. This species accepts the excess positive charge from lithium ions, preventing the redox-active species from being over-oxidized. The mediator enables high lithium content while maintaining the redox-active species in a lower, more stable oxidation state, thus resolving the contradiction between charge capacity and electrochemical performance.
Solution Approach 2:
The invention changes the oxidation state parameter of the charge-compensating species to balance the charge. By introducing a species with a higher oxidation state than the redox-active species, the system maintains charge neutrality with lithium excess without forcing the redox-active species into high oxidation states. This parameter change enables simultaneous achievement of high capacity and good performance.
2Device complexity
If conventional lithium transition metal oxides are used, then the material structure is simple, but the energy density and charge capacity are limited
Solution Approach 1:
The invention creates a composite material system containing three distinct components: redox-active species, charge-compensating species, and lithium ions. This composite approach combines the benefits of multiple species with different functions - the redox-active species provide electron transfer capability, the charge-compensating species enable lithium excess, and together they achieve high energy density. The composite structure resolves the limitation of simple conventional oxides.
Solution Approach 2:
The material is segmented into functionally distinct species: redox-active species responsible for electron transfer and charge-compensating species responsible for charge balance. This functional segmentation allows each component to optimize its role - the redox-active species maintain lower oxidation states while the charge-compensating species handle the excess charge from lithium, enabling high capacity without sacrificing performance.
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 cation-disordered lithium metal oxide exhibits improved charge capacity and energy density, with specific discharge capacities exceeding 200 mAh/g and energy densities up to 680 Wh/kg, surpassing the performance of conventional materials.
Implementation Method 1
forming a percolating network of diffusion pathways
Data Source
AI summary
Embodiments related to cation-disordered lithium metal oxide compounds, their methods of manufacture, and use are described. In one embodiment, a cation-disordered lithium metal oxide includes LiaMbM′cO2 with a greater than 1. M includes at least one redox-active species with a first oxidation state n and an oxidation state n′ greater than n, and M is chosen such that a lithium-M oxide having a formula LiMO2 forms a cation-disordered rocksalt structure. M′ includes at least one charge-compensating species that has an oxidation state y that is greater than n.