Cathode Active Material Surface Doping for Stable Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face rapid capacity decline and poor cycle properties due to low structural stability of existing positive electrode active materials, especially at high temperatures and high voltages, despite efforts to enhance thermal stability and conductivity through doping and surface coatings.
Innovation Solution
A method involving the use of a nanosol of a ceramic-based ion conductor to dope lithium complex metal oxide particles, enhancing structural stability and conductivity by uniformly distributing metal elements from the ceramic-based ion conductor on the surface of the active material particles, prepared through a process of mixing a precursor with the nanosol and a lithium raw material, followed by heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode active material, then lifespan property and charge-discharge efficiency are improved, but structural stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface layer has different composition and properties than the core. The surface is modified with aluminum hydroxide coating and doped with elements like titanium, zinc, or boron to enhance structural stability specifically at the surface where degradation occurs, while maintaining the high-capacity LiCoO2 core composition.
Solution Approach 2:
The patent uses composite materials by combining LiCoO2 with surface-modifying materials such as aluminum hydroxide coating and dopant elements (Ti, Zn, B). This creates a composite structure that integrates the high efficiency of LiCoO2 with the structural stability of the surface layer, resolving the contradiction between lifespan and structural stability.
2Temperature
If doping materials such as Al, Ti, Sn, Ag or Zn is performed, then thermal stability is improved, but capacity decline occurs due to uniform dopant distribution
Solution Approach 1:
The patent applies local quality by concentrating dopants specifically in the surface layer rather than uniformly distributing them throughout the bulk material. The aluminum hydroxide coating serves as a matrix that locally hosts dopant elements at the surface, providing thermal stability where needed while preserving the high-capacity bulk composition.
Solution Approach 2:
The patent changes the concentration parameter of dopants by creating a gradient distribution - high dopant concentration at the surface for thermal stability, and low or zero dopant concentration in the bulk for maintaining capacity. This is achieved through controlled doping during the sol-gel process and subsequent heat treatment.
3Power
If dry or wet coating metals having favorable conductivity on surface is performed, then conductivity is improved, but extent of improvement is insufficient
Solution Approach 1:
The patent uses aluminum hydroxide as an intermediary material that forms a stable surface layer during the sol-gel process. This intermediate layer provides a controlled matrix for subsequent dopant incorporation, enabling better conductivity improvement compared to direct metal coating. The hydroxide layer acts as a mediator between the LiCoO2 core and the dopant elements.
Solution Approach 2:
The patent changes the physical state and composition parameters of the surface layer by using a hydroxide-based sol-gel process instead of direct metal deposition. This creates a more uniform and controllable surface composition that enhances conductivity improvement effectiveness.
4Reliability
If LiNiO2 is used for high discharge capacity, then capacity property is improved, but thermal stability and cycle property deteriorate
Solution Approach 1:
The patent applies local quality by modifying only the surface layer of LiNiO2 particles with aluminum hydroxide coating and dopant elements. This surface modification provides thermal stability and improved cycle properties at the surface, while maintaining the high-capacity Ni-rich composition in the bulk material.
Solution Approach 2:
The patent creates a composite structure combining Ni-rich LiCoO2 (or LiNiO2) core with an aluminum hydroxide-based surface layer containing dopant elements. This composite approach preserves the high discharge capacity of the Ni-rich core while adding thermal stability through the surface layer.
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
This approach significantly improves the structural stability, capacity, and cycle properties of lithium secondary batteries, minimizing capacity decline and enhancing rate and cycle performance compared to traditional doping methods.
Implementation Method 1
mixing a precursor of a metal for a positive electrode active material with a nanosol of a ceramic-based ion conductor to adsorb the nanosol of the ceramic-based ion conductor on the precursor surface
Implementation Method 2
which may be prepared by dissolving a precursor of a metal for forming the ceramic-based ion conductor in a glycol-based solvent, and then hydrating the result by adding water thereto
Implementation Method 3
mixing the nanosol of the ceramic-based ion conductor-adsorbed precursor with a lithium raw material, and heat treating the result to prepare a positive electrode active material including lithium complex metal oxide particles
Data Source
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AI summary
The present invention provides a positive electrode active material prepared using a preparation method including mixing a precursor of a metal for a positive electrode active material with a nanosol of a ceramic-based ion conductor to adsorb the nanosol of the ceramic-based ion conductor on the precursor surface, and mixing the nanosol of the ceramic-based ion conductor-adsorbed precursor with a lithium raw material, and heat treating the resultant to prepare a positive electrode active material including lithium complex metal oxide particles, wherein the lithium complex metal oxide present on a surface side of the lithium complex metal oxide particles is doped with a metal element of the ceramic-based ion conductor, and thereby having greatly increased structural stability by the lithium complex metal oxide present on the surface as a metal element forming the ceramic-based ion conductor being uniformly doped, and as a result, capable of significantly enhancing capacity, a rate property and a cycle property of a battery, a method for preparing the same, and a lithium secondary battery including the same.