Lithium-Metal-Oxide Electrodes with Polyanionic Coatings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium-ion battery cathodes, particularly lithium-metal-oxide electrodes with layered or spinel structures, face challenges in delivering sufficient electrochemical capacity and power due to instability, solubility issues, and limited rate capability, which hinders their application in high-energy and high-power devices like plug-in hybrid-electric vehicles and portable electronics.
Innovation Solution
The use of surface-protected lithium-metal-oxide electrodes with lithium-metal-polyanionic materials, such as lithium-nickel phosphate or lithium-silicate, which act as lithium-ion conductors and provide stability, enhancing the surface protection against electrolyte oxidation and oxygen loss, thereby improving rate and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-metal-oxide electrodes with layered or spinel structures are used to achieve high electrochemical capacity, then the energy density is improved, but the surface stability deteriorates due to electrolyte oxidation and oxygen loss at high potentials
Solution Approach 1:
A lithium phosphate coating layer is applied as an intermediary between the lithium-metal-oxide electrode and the electrolyte. This coating acts as a protective mediator that prevents direct contact and harmful reactions between the electrode surface and electrolyte, thereby maintaining surface stability while preserving electrochemical capacity at high potentials
Solution Approach 2:
The electrode structure is transformed into a composite material system consisting of the core lithium-metal-oxide material combined with a lithium phosphate coating layer. This composite structure integrates the high capacity characteristics of the lithium-metal-oxide with the protective properties of the lithium phosphate coating, resolving the contradiction between capacity and stability
2Use of energy by moving object
If lithium-metal-oxide electrodes are charged to high potentials to deliver higher capacities, then the energy output is improved, but the cycling stability deteriorates due to surface degradation
Solution Approach 1:
The lithium phosphate coating serves as a stable intermediary layer that remains intact at high potentials, protecting the electrode surface from degradation during repeated charging cycles. This enables the electrode to maintain cycling stability even when charged to high potentials for maximum energy output
Solution Approach 2:
The lithium phosphate coating is applied in advance before the electrode undergoes cycling at high potentials. This preliminary protective action prevents surface degradation from occurring in the first place, allowing the electrode to withstand high potential charging throughout its operational life
3Power
If conventional lithium-metal-oxide electrodes are used to achieve high power output, then the rate capability is improved, but the surface protection deteriorates leading to increased oxygen loss and electrolyte oxidation
Solution Approach 1:
The lithium phosphate coating acts as a protective intermediary that blocks the pathways for oxygen loss and electrolyte oxidation while still allowing lithium ion transport. This enables the electrode to deliver high power output without generating harmful side reactions
Solution Approach 2:
The protective properties are localized to the electrode surface through the lithium phosphate coating layer. This coating provides targeted protection at the surface where harmful reactions occur, while the bulk electrode material maintains its high power output characteristics
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 surface protection significantly enhances the electrochemical performance of lithium-metal-oxide electrodes, allowing for higher capacities to be delivered at improved rates and improved cycling stability, especially when charged to high potentials, thus addressing the limitations of conventional lithium-ion batteries.
Implementation Method 1
lithium-metal-polyanionic materials, for example, a lithium-metal-phosphate, a lithium-metal-silicate or the like, such as a lithium-nickel phosphate or a lithium-nickel-silicate, that can act as a lithium-ion conductor
Implementation Method 2
protecting the surface of the electrode from undesirable effects, such as electrolyte oxidation
Implementation Method 3
protecting the surface of the electrode from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution
Data Source
AI summary
A lithium-metal-oxide positive electrode having a layered or spinel structure for a non-aqueous lithium electrochemical cell and battery is disclosed comprising electrode particles that are protected at the surface from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution by one or more lithium-metal-polyanionic compounds, such as a lithium-metal-phosphate or a lithium-metal-silicate material that can act as a solid electrolyte at or above the operating potential of the lithium-metal-oxide electrode. The surface protection significantly enhances the surface stability, rate capability and cycling stability of the lithium-metal-oxide electrodes, particularly when charged to high potentials.