Mixed-Phase Cathode Coating for Low-Resistance Li-Ion Batteries
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries require improvements in discharge capacity and durability while reducing positive electrode resistance to meet increasing demands for high energy density and output.
Innovation Solution
A positive electrode active material comprising a lithium metal composite oxide powder with a mixed-phase coating layer of crystalline and amorphous phases, specifically containing lithium tungstate, is used to enhance lithium ion conductivity and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel composite oxide is used as positive electrode active material to achieve high battery capacity, then discharge capacity is improved, but positive electrode resistance increases and durability deteriorates
Solution Approach 1:
A coating layer comprising lithium tungstate fine particles is introduced as an intermediary substance between the lithium-nickel composite oxide and the electrolyte. This coating layer mediates the interaction, providing a conductive pathway that reduces positive electrode resistance while protecting the bulk material from degradation, thereby improving both durability and charge-discharge characteristics without sacrificing capacity.
Solution Approach 2:
The invention changes the surface parameter of the lithium-nickel composite oxide by forming a coating layer with specific composition (lithium tungstate) and structure (amorphous and/or crystalline phases). This parameter change at the surface level reduces resistance and improves charge-discharge characteristics while maintaining the high-capacity bulk material composition.
2Power
If transition metals (W, Mo, Nb, Ta, Re) are added to reduce resistance and improve output, then positive electrode resistance is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of uniformly distributing transition metal elements throughout the bulk lithium-nickel composite oxide structure, the invention applies the transition metal (tungsten) locally as a surface coating layer. This local quality approach reduces resistance and improves output while avoiding the complexity of bulk doping and maintaining simpler manufacturing processes for the core material.
3Power
If surface coating with lithium tungstate is applied to reduce resistance and improve charge-discharge characteristics, then positive electrode resistance is suppressed and output is improved, but manufacturing precision requirements increase
Solution Approach 1:
The coating layer is formed with lithium tungstate fine particles where the particle size and coverage are optimized to provide sufficient conductive pathways without requiring complete or ultra-thin uniform coverage. This partial action approach achieves the desired resistance reduction and output improvement while being more tolerant to manufacturing variations compared to requiring precise thin-film coating control.
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 increases discharge capacity, improves durability, and suppresses positive electrode resistance, leading to higher output and thermal stability, making it suitable for portable electronics and electric vehicles.
Implementation Method 1
The addition of heteroelements has been proposed as a method of achieving the above-mentioned resistance reduction, and transition metals, such as W, Mo, Nb, Ta and Re, that are high valence, have been known as particularly useful.
Data Source
AI summary
The present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery including a lithium metal composite oxide powder represented by a general formula: LizNi1−x−yCoxMyO2+α, wherein 0<x≤0.35, 0≤y≤0.35, 0.95≤z≤1.30, −0.15≤α≤0.15, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al; and a coating layer placed on particle surfaces of the lithium metal composite oxide powder; wherein the coating layer is a mixed-phase of a crystalline phase and an amorphous phase.