Halogen-Containing Lithium Transition Metal Oxide Surface Coating
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face issues with capacity reduction and gas generation due to electrolyte decomposition when stored at high temperatures in a charged state, particularly with lithium transition metal oxides containing halogen atoms as positive electrode active materials.
Innovation Solution
A positive electrode active material is developed by attaching a rare-earth compound to the surface of lithium transition metal oxide particles, ensuring the halogen atom concentration on the surface is 5 mass percent or less, which stabilizes the crystal structure and suppresses electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lithium transition metal oxide containing a halogen atom is used as a positive electrode active material to increase charge voltage, then the charge voltage of the battery is improved, but the nonaqueous electrolyte is decomposed during storage at high temperature leading to capacity reduction and gas generation
Solution Approach 1:
A rare-earth compound is introduced as an intermediary substance between the halogen-containing lithium transition metal oxide and the nonaqueous electrolyte. This intermediate layer prevents direct contact and harmful interactions between the electrolyte and halogen atoms, thereby suppressing electrolyte decomposition while maintaining the high voltage characteristics of the halogen-containing active material
Solution Approach 2:
The harmful halogen atoms are extracted from the surface region of the lithium transition metal oxide particle by attaching the rare-earth compound. This concentrates the halogen atoms in the interior of the particle while the surface is covered by the rare-earth compound, eliminating the source of electrolyte decomposition at the particle surface
2Quantity of substance
If the halogen atom concentration on the surface of lithium transition metal oxide is increased to enhance battery performance, then the energy density is improved, but the decomposition of nonaqueous electrolyte is accelerated during high-temperature storage
Solution Approach 1:
The structure is designed with different compositions at different locations: the interior of the particle contains high halogen atom concentration for enhanced performance, while the surface is covered by rare-earth compound to prevent harmful interactions. This local differentiation allows simultaneous achievement of high energy density and electrolyte stability
Solution Approach 2:
The rare-earth compound serves as a protective intermediary layer that physically separates the high-concentration halogen atoms from the electrolyte, allowing the system to maintain high halogen content for energy density while preventing the harmful decomposition reactions
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
This configuration effectively prevents capacity reduction and gas generation during high-temperature storage in a charged state, maintaining battery performance and energy density.
Implementation Method 1
a rare-earth compound attached to the surface of each particle of the lithium transition metal oxide
Data Source
AI summary
Provided are a positive electrode active material capable of suppressing the reduction in capacity of a battery and the generation of gas during storage at high temperature in a charged state and a nonaqueous electrolyte secondary battery including the positive electrode active material. A positive electrode active material particle (20) includes a lithium transition metal oxide particle (21) containing a halogen atom and rare-earth compound particles (22) attached to the surface of the lithium transition metal oxide particle (21). The amount of the halogen atom present on the surface of the lithium transition metal oxide particle (21) is 5 mass percent or less of the total amount of the halogen atom contained in the lithium transition metal oxide particle (21). A rare-earth element making up the rare-earth compound particles (22) is one other than yttrium and scandium.