Cathode Active Material for Lithium Battery Swelling Control
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Solution Overview
Problem
Lithium secondary batteries face issues with cation mixing, leading to swelling, reduced high-rate discharge characteristics, and instability due to the substitution of Li cations with Ni cations, which affects the performance and safety of cathode active materials like LiNiO2-based batteries.
Innovation Solution
A cathode active material represented by the formula Li a Ni x Mn y Co z M w O 2-t, where M is a metal cation with a greater ionic radius than Ni, such as Sr2+ or Ba2+, is introduced to minimize cation mixing by occupying Li cation sites or empty spaces in the crystal lattice, thereby enhancing structural stability and reducing natural Li cation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LiNiO2-based cathode active material is used to achieve high discharge capacity and low cost, then excellent battery characteristics are obtained, but cation mixing occurs leading to swelling, deterioration of high-rate discharge characteristics, and rapid phase transition
Solution Approach 1:
The patent applies local quality by introducing a metal element (Mg, Ca, Sr, or Ba) at specific crystal lattice positions (Li cation sites or empty spaces) within the cathode material structure. This localized doping at specific positions prevents cation mixing and stabilizes the crystal structure, thereby improving cycle characteristics while maintaining the high discharge capacity provided by the LiNiO2-based material.
Solution Approach 2:
The patent creates a composite cathode active material with formula Li1-xMxNi1-yMn1-zCoxO2 or Li1-xMxNi1-yMn1-zCoxO2-tAt, combining LiNiO2 with metal-doped LiMnO3 and LiCoO3 components. This composite structure leverages the high capacity of LiNiO2 while the doped LiMnO3 phase prevents cation mixing and swelling, achieving both high discharge capacity and improved cycle characteristics.
2Reliability
If LiCoO2 is used as cathode active material to achieve excellent lifespan characteristics and high charge-discharge efficiency, then high performance is obtained, but safety at high temperature is low and cobalt is expensive
Solution Approach 1:
The patent develops a composite cathode material combining LiNiO2-based high-capacity phase with metal-doped LiMnO3 phase. The LiMnO3 component provides high thermal stability that compensates for the lower temperature safety of LiNiO2, creating a composite that maintains both excellent lifespan characteristics and improved high-temperature safety.
3Object-affected harmful factors
If lithium-containing manganese oxides are used to achieve high thermal stability and low cost, then thermal safety and price competitiveness are improved, but capacity is low and high-temperature characteristics are poor
Solution Approach 1:
The patent creates a composite where metal-doped LiMnO3 (providing thermal stability) is combined with LiNiO2-based phase (providing high discharge capacity). The synergistic combination allows the material to achieve both the thermal stability of manganese oxides and the high capacity of nickel-based materials, overcoming the limitations of using either component alone.
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 use of the cathode active material with a larger metal cation reduces Li cation loss, minimizes swelling, and improves the safety and performance of lithium secondary batteries by maintaining capacity retention and structural integrity, even under extended use and high-temperature conditions.
Implementation Method 1
a metal cation having a greater ionic radius than a Ni cation at a Li cation site or in an empty space within a crystal lattice so as to prevent mixing of Ni cations into a Li layer
Data Source
Figure 1
Figure 2~3
AI summary
Disclosed are a cathode active material represented by Formula 1 below and including a metal cation having a greater ionic radius than a Ni cation and represented by M of Formula 1 at a Li cation site or in an empty space within a crystal lattice so as to prevent mixing of Ni cations into a Li layer, a lithium secondary battery including the same, and a method of preparing the cathode active material which has improved productivity. €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒLi a Ni x Mn y Co z M w O 2-t A t €ƒ€ƒ€ƒ€ƒ€ƒ(1) wherein a, x, y, w, M, A, z, and t are the same as defined in the specification.