Positive electrode active materials, positive electrodes, and rechargeable lithium batteries
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Solution Overview
Problem
Rechargeable lithium batteries using lithium nickel-based oxides, lithium nickel-cobalt based composite oxides, and lithium nickel-manganese based composite oxides face issues with thermal runaway due to heat generation during short circuits, posing a safety risk.
Innovation Solution
A positive electrode active material comprising a mixture of lithium iron phosphate-based compounds and lithium nickel-based composite oxides, with a specific weight ratio, along with a thin-walled carbon nanotube to enhance stability and conductivity, is used to create a positive electrode for rechargeable lithium batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel-based oxides or lithium nickel-cobalt/manganese based composite oxides are used as positive electrode active materials, then high capacity is achieved, but thermal stability deteriorates causing heat generation and thermal runaway during short circuits
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of lithium nickel-based oxide (LiNi0.8Co0.1Mn0.1O2) as the core material and lithium iron phosphate (LiFePO4) as the coating layer. This composite structure combines the high capacity characteristics of lithium nickel-based oxides with the excellent thermal stability of lithium iron phosphate, thereby achieving both high capacity and improved thermal stability while preventing thermal runaway during short circuits.
2Reliability
If lithium iron phosphate-based compounds are used as positive electrode active materials, then thermal stability is improved, but capacity decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core (lithium nickel-based oxide) provides high capacity and the shell (lithium iron phosphate coating layer with 1-15 wt%) provides thermal stability. This localized differentiation allows the high-capacity core material to function while being protected by the thermally stable coating, thus achieving both high capacity and improved thermal stability simultaneously.
Data Source
AI summary
A positive electrode active material is provide, the positive electrode active material including a first positive electrode active material including a lithium iron phosphate-based compound; and a second positive electrode active material including lithium nickel-based composite oxide; wherein the second positive electrode active material is included in an amount of about 1 wt % to about 15 wt % based on 100 wt % of the first positive electrode active material and second positive electrode active material. The positive electrode active material, the positive electrode including the same, and the rechargeable lithium battery according to some example embodiments may achieve high capacity and excellent or suitable stability.