Lithium Nickel Cathode Material High Temperature Swelling
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with structural instability and poor inhibition of swelling at high temperatures in existing positive active materials, particularly at charge voltages above 4.2V, which limits their energy density and cycle life.
Innovation Solution
A lithium/nickel-based positive active material with secondary particles of 1 μm to 4 μm diameter, formed by heat-treating a hydroxide compound containing nickel and cobalt, and further processed with a lithium-containing compound through multiple heat treatments to minimize surface carbon content and optimize particle size, enhancing electrochemical performance and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charge voltage is increased to over 4.2V to obtain more than 50% of the theoretical capacity of LiCoO2, then the energy density is improved, but the structural instability due to phase transition sharply decreases the capacity retention
Solution Approach 1:
The patent modifies the chemical composition parameters of the cathode material by introducing multiple dopant elements (Mg, Sr, V, and rare earth elements) at controlled concentrations. This changes the electronic and structural parameters of LiCoO2, stabilizing the crystal structure at high voltages above 4.2V and preventing phase transitions that would otherwise cause capacity fading.
Solution Approach 2:
The patent creates a composite cathode material system where LiCoO2 is doped with multiple elements (Mg, Sr, V, and rare earth elements) to form a multi-element composite structure. This composite approach combines the high energy density of LiCoO2 with the structural stability provided by the dopant elements, enabling operation at high voltages without severe capacity retention loss.
2Use of energy by moving object
If existing positive active materials are used to achieve high energy density, then the electrochemical performance is improved, but the inhibition of swelling at high temperatures is poor
Solution Approach 1:
The patent changes the thermal and structural parameters of the cathode material by incorporating dopant elements with different thermal expansion characteristics and ionic radii. These parameter modifications reduce the material's susceptibility to thermal swelling while maintaining high energy density, as the dopants stabilize the crystal lattice against temperature-induced expansion.
Solution Approach 2:
The patent develops a composite cathode material where LiCoO2 is combined with dopant elements (Mg, Sr, V, and rare earth elements) to create a multi-component system. This composite structure provides both high energy density and improved resistance to high-temperature swelling, as the dopant elements create a more thermally stable lattice structure.
3Quantity of substance
If LiCoO2 is used as positive active material, then the theoretical capacity is high (274 mAh/g), but only about 50% is practically obtained due to structural instability
Solution Approach 1:
The patent modifies the structural and electronic parameters of LiCoO2 through multi-element doping, changing the crystal field stabilization energy and ionic conductivity parameters. These parameter changes enable more complete lithium extraction and insertion without triggering structural collapse, thus achieving higher practical capacity utilization close to the theoretical maximum.
Solution Approach 2:
The patent creates a composite cathode material system where LiCoO2 is doped with multiple elements to form a structurally reinforced composite. This composite structure maintains the high theoretical capacity of LiCoO2 while preventing structural instability, enabling practical capacity utilization to approach the theoretical limit of 274 mAh/g.
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 provides excellent electrochemical performance and significant inhibition of swelling at high temperatures, maintaining high discharge capacity and cycle life, while reducing surface carbon content and optimizing particle size for improved battery functionality.
Implementation Method 1
preparing an oxide material by heat-treating a hydroxide compound that includes nickel and cobalt
Implementation Method 2
mixing the oxide material with a lithium-containing compound and performing a first heat treatment to the resulting mixture; and performing a second heat treatment to the first heat-treated mixture
Data Source
AI summary
The present invention relates to a positive active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery comprising the same. The positive active material includes a lithium/nickel-based compound wherein primary particles having an average particle diameter ranging from 1 μm to 4 μm are agglomerated to form secondary particles. The positive active material of the present invention has excellent electrochemical performance and outstanding inhibition to swelling at high temperatures.