Dual-Doped Cathode Material for Capacity and Thermal Stability
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Solution Overview
Problem
Lithium-nickel composite oxides used in lithium secondary batteries have poor thermal stability, leading to battery rupture and ignition due to internal short circuits, and substituting nickel with cobalt or manganese results in compromised thermal stability and output characteristics.
Innovation Solution
A positive electrode active material comprising a lithium layer doped with a first doping element and a transition metal layer doped with a second doping element, with an I(003)/I(006) peak intensity ratio in X-ray diffraction measurement of 23.8 or less, is developed, improving thermal stability and cell characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel composite oxide is used as positive electrode active material, then reversible capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct doped regions within the cathode material structure. Specifically, magnesium is doped into the lithium layer while aluminum is doped into the transition metal layer, creating localized compositional variations that provide different functional properties in different regions of the material, thereby achieving both high capacity and thermal stability
Solution Approach 2:
The patent employs composite materials by combining multiple elements (lithium, nickel, magnesium, aluminum, and other transition metals) into a multi-element composite oxide structure. This composite approach allows the material to simultaneously exhibit high reversible capacity from the nickel content and improved thermal stability from the magnesium and aluminum doping, resolving the contradiction between capacity and thermal stability
2Productivity
If nickel is substituted with cobalt, then charge and discharge characteristics are improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping concentrations of magnesium and aluminum, as well as the overall composition ratios of the cathode material. By optimizing these compositional parameters, the material achieves excellent charge and discharge characteristics while maintaining high thermal stability, avoiding the thermal stability issues associated with cobalt substitution
3Reliability
If nickel is substituted with manganese, then thermal stability is improved, but output characteristics deteriorate
Solution Approach 1:
The patent applies local quality by placing magnesium specifically in the lithium layer and aluminum in the transition metal layer, creating localized functional regions. This spatial differentiation allows the material to achieve both improved thermal stability and maintained output characteristics, avoiding the output deterioration that occurs with direct nickel-manganese substitution
4Reliability
If nickel is substituted with cobalt and manganese, then thermal stability is improved, but metal element elution increases
Solution Approach 1:
The patent employs composite materials by creating a multi-element composite oxide structure with magnesium, aluminum, and other transition metals. This composite approach provides a more stable crystal structure that prevents metal element elution while maintaining thermal stability, overcoming the elution problem associated with cobalt-manganese substitution
Data Source
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AI summary
A positive electrode active material according to an Example of the present invention may comprise a lithium layer doped with a first doping element and a transition metal layer doped with a second doping element, wherein an I(003)/I(006) peak intensity ratio in X-ray diffraction measurement is equal to or less than 23.8.