High-Nickel Cathode Single Particles That Resist Rolling Cracks
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Solution Overview
Problem
Existing lithium transition metal oxides used in positive electrodes of lithium secondary batteries, particularly those with high nickel content, suffer from particle cracking during rolling, leading to increased side reactions with electrolyte solutions and reduced conductivity, which affects the battery's volumetric energy density and life characteristics.
Innovation Solution
A positive electrode active material comprising a lithium transition metal oxide with 60 mol% nickel, formulated as a single particle with specific particle strength and diameter, is prepared through a two-stage sintering process to minimize fine powder formation and enhance crystallinity, reducing particle cracking during rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content (60 mol% or more) is used in lithium transition metal oxide to achieve large capacity, then reversible capacity is improved, but particle cracking occurs during rolling leading to increased side reactions and reduced conductivity
Solution Approach 1:
The patent applies parameter changes by optimizing the particle strength to be 600-1500 MPa and controlling the particle diameter within specific ranges. These parameter modifications enable the high nickel content material to maintain structural integrity during rolling while preserving the high reversible capacity, thus resolving the contradiction between capacity and particle stability
Solution Approach 2:
The patent creates a composite structure by forming a coating layer on the surface of the lithium transition metal oxide particles. This composite approach enhances particle strength and prevents cracking during rolling, allowing the high nickel content core to maintain its large capacity while the protective coating prevents degradation
2Volume of stationary object
If rolling pressure is applied to reduce voids and increase volumetric energy density, then packing density is improved, but particle cracking increases leading to more side reactions with electrolyte
Solution Approach 1:
The patent implements beforehand cushioning by pre-enhancing the particle strength to 600-1500 MPa and forming protective coating layers before the rolling process. This preparatory strengthening allows the particles to withstand the rolling pressure that increases volumetric energy density without cracking, thereby preventing the harmful side reactions that would otherwise occur
3Strength
If particle strength is increased to suppress cracking during rolling, then particle stability is improved, but manufacturing complexity increases due to two-stage sintering process
Solution Approach 1:
The patent applies segmentation by dividing the sintering process into two distinct stages: a first sintering stage to form the base structure and a second sintering stage to enhance particle strength and form the protective coating. This segmented approach systematically achieves the required particle strength of 600-1500 MPa while making the complex manufacturing process more controllable and manageable
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 effectively suppresses particle cracking and minimizes side reactions, resulting in improved capacity and life characteristics of the lithium secondary battery.
Implementation Method 1
a positive electrode active material comprising a lithium transition metal oxide in a form of a single particle, wherein the lithium transition metal oxide contains 60 mol% or more of nickel among total transition metals
Data Source
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AI summary
The present invention relates to a positive electrode active material comprising a lithium transition metal oxide in a form of a single particle, wherein the lithium transition metal oxide contains 60 mol% or more of nickel among total transition metals, wherein, when a pressure of 6,500 kgf/cm2 is applied to the positive electrode active material, an amount of fine powder having a particle diameter of 1 µm or less is 10 vol% or less based on a total volume of the positive electrode active material after the applying the pressure, a method for preparing the positive electrode active material, and a positive electrode and lithium secondary battery including the positive electrode active material.