Overlithiated Cathode Material for Higher Density and Lower Voltage Decay
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Solution Overview
Problem
Lithium nickel manganese cobalt oxide-based positive electrode active materials face issues of poor rate capability, low packing density, and voltage decay due to phase transitions during life cycling, primarily from transition metal migration and high surface area reactions.
Innovation Solution
The use of an overlithiated layered oxide (OLO) with dopants to grow primary particles into secondary particles, forming a single-crystal structure, reduces the specific surface area and enhances packing density and energy density, thereby stabilizing the internal structure and mitigating voltage decay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional Li(NixCoyMnz)O2 is used as positive electrode active material, then high capacity is achieved, but poor rate capability and poor life characteristics at high temperatures occur
Solution Approach 1:
The patent applies parameter changes by modifying the stoichiometric composition of the layered oxide to create an overlithiated structure (Li1.2Ni0.13Co0.13Mn0.54)O2 with excess lithium content. This compositional parameter change transforms the material properties to achieve both high capacity and improved life characteristics, resolving the contradiction between capacity and reliability.
2Use of energy by moving object
If overlithiated layered oxide (OLO) is applied to lithium secondary batteries, then high reversible capacity is achieved, but voltage decay phenomenon occurs due to phase transition from spinel-like structure to cubic
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different compositional characteristics from the bulk. The surface is enriched with lithium and transition metals forming a protective layer that maintains structural stability, while the bulk retains the high-capacity overlithiated composition. This local differentiation resolves the contradiction between high reversible capacity and structural stability.
3Quantity of substance
If primary particles are grown larger to improve packing density, then energy density increases, but specific surface area decreases leading to more severe surface reactions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution and morphology during synthesis. By optimizing the particle size parameters (achieving uniform spherical particles with controlled dimensions), the patent increases packing density while maintaining an appropriate specific surface area that limits harmful surface reactions. The compositional parameter changes (overlithiation) also modify surface reactivity.
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 solution significantly improves energy density, packing density, and reduces surface reactions, leading to enhanced life and voltage retention in lithium secondary batteries.
Implementation Method 1
dopants serving as a flux for growing the primary particles
Data Source
AI summary
The present disclosure is related to a positive electrode active material for lithium secondary batteries, a method for preparing the positive electrode active material, and a lithium secondary battery including the positive electrode active material. The positive electrode active material for lithium secondary batteries includes an overlithiated layered oxide (OLO), and the overlithiated layered oxide includes primary particles having a size in a range of 300 nm to 10 μm in an amount ranging from 50 to 100% by volume with respect to the total overlithiated layered oxide.