Rock-Salt Cathode Doping for Higher Energy Density and Capacity
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Solution Overview
Problem
Existing positive electrode active materials for lithium ion secondary batteries, despite improvements, still fall short in achieving high energy density and capacity, particularly when using lithium transition metal composite oxides with a rock salt structure.
Innovation Solution
Incorporating trace amounts of elements such as Ca, Al, and Si into lithium metal composite oxides with a rock salt structure, along with fluorine substitution, to enhance electron movement and vacancy creation, thereby improving charge transfer reactions and discharge potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li-excessive lithium metal composite oxide with rock salt structure is used to achieve high capacity, then energy density is improved, but capacity improvement is insufficient and stability deteriorates
Solution Approach 1:
The patent applies local quality by introducing specific dopant elements (Ca, Al, or Si) at controlled concentrations (0.01 ≤ a ≤ 0.20 in the formula Li1+xMn1-aAO2) into the rock salt structure. This localized modification of the crystal lattice creates optimal conditions for both high capacity and stability, where the dopant elements occupy specific sites to enhance lithium mobility and structural integrity without completely altering the overall rock salt architecture.
Solution Approach 2:
The patent employs parameter changes by systematically varying the composition parameters (x and a in the formula Li1+xMn1-aAO2) to optimize performance. Specifically, controlling the lithium excess parameter (x) and dopant concentration (a) allows tuning of the material's electrochemical properties, achieving the balance between high energy density and stable capacity retention that was not attainable with previous compositions.
2Quantity of substance
If cobalt is replaced with nickel to increase capacity, then energy density is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses parameter changes by modifying the transition metal composition ratio, specifically using manganese-based rock salt structure with controlled lithium excess and dopant addition, rather than nickel-cobalt composite systems. This compositional parameter adjustment achieves high capacity while simplifying the manufacturing process, as the rock salt structure can be synthesized through more straightforward solid-state reactions compared to multi-component nickel-cobalt materials.
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 results in a significant increase in energy density and available capacity of secondary batteries, with improved discharge potential and stability of the Li-excessive state, leading to enhanced battery performance.
Implementation Method 1
Incorporating trace amounts of elements such as Ca, Al, and Si into lithium metal composite oxides with a rock salt structure, along with fluorine substitution, to enhance electron movement and vacancy creation, thereby improving charge transfer reactions
Data Source
AI summary
A positive electrode active material for a secondary battery including: a lithium metal composite oxide having a crystal structure based on a rock salt structure belonging to a space group Fm-3m. The lithium metal composite oxide contains an element A1 of at least one selected from the group consisting of Ca, Al, and Si, and in the lithium metal composite oxide, a total of Ca, Al, and Si contents relative to a total of the lithimn metal composite oxide is 10 to 1000 ppm by mass.