Lithium Cobalt Oxide Surface Doping for Cycle-Stable Cathodes
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining discharge capacity retention rates due to defects in positive electrode active materials after cycle tests, leading to deterioration and reduced battery lifespan.
Innovation Solution
Incorporating lithium cobalt oxide with additive elements like magnesium or aluminum, which are positioned in the surface regions of the positive electrode active material to form barrier layers that inhibit deterioration and maintain the crystal structure, thereby reducing defect progression and enhancing battery safety and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sol-gel treatment is performed multiple times to repair cracks in positive electrode active material, then crack repair is achieved, but the deterioration state after cycle test is not addressed and discharge capacity retention rate decreases
Solution Approach 1:
The patent applies preliminary action by forming a protective coating layer containing additive elements (such as aluminum, magnesium, or calcium) on the surface of the positive electrode active material before cycle testing begins. This pre-formed protective layer prevents crack formation and deterioration during cycling, addressing the root cause rather than just repairing symptoms after they occur. The coating is applied through methods such as co-precipitation, sol-gel, or atomic layer deposition, ensuring the protective elements are in place before any deterioration can occur.
2Reliability
If additive elements are incorporated into lithium cobalt oxide, then deterioration is inhibited and discharge capacity retention is improved, but the complexity of material composition increases
Solution Approach 1:
The patent applies local quality by concentrating the additive elements specifically at the surface region of the positive electrode active material particles rather than uniformly distributing them throughout the bulk material. The surface coating contains the additive elements (aluminum, magnesium, calcium, etc.) at concentrations of 1-10 atomic percent, while the interior maintains the original lithium cobalt oxide composition. This localized approach provides protective functionality at the surface where deterioration occurs most, while keeping the bulk material simple and effective for lithium ion insertion/extraction.
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 proposed solution effectively suppresses the decrease in discharge capacity retention rate, leading to a longer battery lifespan and improved safety for lithium-ion secondary batteries.
Implementation Method 1
the additive element is positioned in a surface portion of the lithium cobalt oxide... contains at least an element identical to the additive element in a region in the vicinity of the defect
Data Source
AI summary
A positive electrode active material in which the number of defects that cause deterioration is small or progress of the defect is suppressed is provided. The positive electrode active material is used for a secondary battery. The positive electrode active material contains lithium cobalt oxide containing an additive element. After a cycle test is performed on a cell that uses the positive electrode active material for a positive electrode and a lithium electrode as a counter electrode, the positive electrode active material includes a defect and contains at least the same element as the additive element in a region in the vicinity of the defect. The additive element is contained also in a surface portion of the positive electrode active material.