Lithium Cobalt Oxide Coated with Phosphate for Cycle Life
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with lithium-containing transition metal oxides, such as lithium cobalt oxide, face challenges in maintaining initial efficiency and cycle performance due to volume changes during charge-discharge processes, leading to capacity degradation.
Innovation Solution
A lithium-containing transition metal oxide with a layered structure is coated with a phosphate compound surface-treatment layer and doped with a group IVA element and a group IIA element, which improves cycle performance without degrading initial efficiency by restraining irreversible reactions with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of lithium cobalt oxide is treated with aluminum phosphate compound, then cycle performance is improved, but initial efficiency degrades
Solution Approach 1:
The patent changes the chemical composition parameters of the surface treatment layer by using a phosphate compound with general formula M1POk where M1 is a trivalent element and k is 2-4, rather than conventional aluminum phosphate. This parameter change allows achieving both improved cycle performance and maintained initial efficiency.
Solution Approach 2:
The patent creates a composite material structure where lithium cobalt oxide is coated with a phosphate compound layer containing trivalent elements. This composite structure combines the benefits of surface protection for cycle stability while controlling the chemical composition to minimize initial efficiency loss.
2Reliability
If another element is added to lithium-containing transition metal oxide to improve cycle performance, then cycle performance is improved, but initial efficiency degrades
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating a group IVA element at 0.01-5 mol% and a group IIA element at 0.01-5 mol% in the lithium-containing transition metal oxide. This precise parameter control improves cycle performance while minimizing the negative impact on initial efficiency.
Solution Approach 2:
The patent applies element addition locally and selectively - only small amounts of group IVA and IIA elements are added to specific positions in the crystal structure, providing local structural reinforcement to improve cycle performance without significantly affecting overall initial efficiency.
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 approach enhances cycle performance while maintaining initial efficiency, as demonstrated by improved charge-discharge characteristics and capacity retention in lithium cobalt oxide-based batteries.
Implementation Method 1
the lithium-containing transition metal oxide is at least partially covered with a surface-treatment layer comprising a phosphate compound represented by the chemical formula M1POk
Implementation Method 2
the lithium-containing transition metal oxide contains a group IVA element M2 and a group IIA element M3 of the periodic table
Data Source
AI summary
Cycle performance is improved without degrading initial efficiency of a non-aqueous electrolyte secondary battery that includes a positive electrode, a negative electrode, a non-aqueous electrolyte containing a solute and a solvent, the positive electrode including a positive electrode active material made of a lithium-containing transition metal oxide that contains lithium and cobalt and has a layered structure. The lithium-containing transition metal oxide is at least partially covered with a surface-treatment layer containing a phosphate compound represented by the chemical formula M1POk, where M1 is at least one element that can have a valency of 3 and k is an integer in a range of 2 to 4, and the lithium-containing transition metal oxide contains a group IVA element M2 and a group IIA element M3 of the periodic table.