Boron-Doped NCM Cathode Material for High-Nickel Stability
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Solution Overview
Problem
Lithium nickel cobalt manganese oxide positive electrode active materials for lithium secondary batteries face limitations due to low particle strength, structural instability, and capacity issues, particularly when nickel content exceeds 60 mol%, leading to swelling and reduced battery performance.
Innovation Solution
A lithium transition metal oxide with a composition of Li1+a Ni x Co y Mn z B w O2, where 0≤a≤0.5, 0.8≤x<1, 0<y≤0.2, 0<z≤0.2, and 0<w≤0.01, doped with boron (B), is used, with an average particle diameter of 4 µm to 10 µm and a rolling density of 3.0 g/cm3 to 3.3 g/cm3, to enhance capacity, lifetime, and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of nickel is increased to 60 mol% or more to increase capacity characteristics, then the reversible capacity is improved, but a large amount of lithium by-products such as LiOH and Li2CO3 are generated on the surface due to the tendency of nickel to be maintained as Ni2+
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxidation state of nickel from Ni2+ to Ni3+ through adjusted calcination conditions. This transformation reduces the tendency to form lithium by-products while maintaining high reversible capacity. The specific parameter changes include calcination temperature (800-900°C), oxygen partial pressure (0.1-0.5 MPa), and calcination time (10-20 hours), which collectively achieve the desired nickel oxidation state and minimize harmful by-product formation.
Solution Approach 2:
The patent employs strong oxidizing conditions during calcination to accelerate the oxidation of nickel from Ni2+ to Ni3+. By using an oxygen-rich atmosphere with controlled oxygen partial pressure (0.1-0.5 MPa) and elevated temperatures (800-900°C), the oxidation process is enhanced, ensuring complete conversion of nickel species. This accelerated oxidation prevents the formation of Ni2+ that would otherwise lead to lithium by-product generation, thereby resolving the contradiction between high capacity and by-product reduction.
2Quantity of substance
If LiCoO2 is used as a positive electrode active material, then high operating voltage and excellent capacity characteristics are achieved, but very poor thermal properties occur due to an unstable crystal structure caused by delithiation and high cost
Solution Approach 1:
The patent employs composite materials by creating a lithium nickel cobalt manganese oxide with a specific layered structure that combines multiple transition metals. This composite approach integrates the high voltage and capacity benefits of nickel-based materials with the thermal stability contributions from cobalt and manganese. The layered structure with controlled stoichiometry (Li1-x-y-zNixCoyMnzO2) achieves a balance between electrochemical performance and thermal reliability, resolving the contradiction between high capacity/voltage and thermal stability.
3Quantity of substance
If LiNiO2 is used to achieve high reversible capacity, then excellent capacity characteristics are obtained, but poorer thermal stability occurs and the positive electrode active material decomposes when internal short circuit occurs
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of transition metals within the crystal structure. Specifically, nickel is concentrated in certain layers while cobalt and manganese are distributed in other regions, creating local variations in chemical composition and properties. This local quality approach allows high-capacity nickel regions to coexist with thermally stable cobalt and manganese regions, achieving both high reversible capacity and improved thermal stability simultaneously.
Solution Approach 2:
The patent uses composite materials by forming a multi-element lithium transition metal oxide where nickel, cobalt, and manganese are combined in specific ratios within a layered structure. This composite material approach leverages the high capacity of nickel while incorporating the thermal stability contributions from cobalt and manganese, creating a material that exhibits both excellent reversible capacity and improved thermal resistance compared to pure LiNiO2.
4Quantity of substance
If lithium nickel cobalt manganese oxide is used, then capacity characteristics are improved, but low particle strength and structural stability occur
Solution Approach 1:
The patent applies parameter changes by optimizing calcination conditions including temperature (800-900°C), oxygen partial pressure (0.1-0.5 MPa), and time (10-20 hours). These parameter adjustments promote the formation of a well-crystallized layered structure with enhanced particle strength and structural stability. The controlled oxidation of nickel to Ni3+ during calcination also strengthens the crystal lattice, preventing structural degradation while maintaining high capacity characteristics.
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 boron-doped lithium transition metal oxide improves structural stability, reduces lithium by-products, and maintains electrochemical properties even at lower calcination temperatures, resulting in improved particle strength, capacity retention, and resistance characteristics for lithium secondary batteries.
Implementation Method 1
a positive electrode active material which is a lithium transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn) and represented by Li1+aNixCoyMnzM1-bO2-b wherein M represents at least one element selected from the group consisting of boron (B), aluminum (Al), and titanium (Ti)
Implementation Method 2
mixing a lithium raw material with the mixture and calcining at 810°C or higher to prepare a lithium transition metal oxide in the form of a single particle
Data Source
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AI summary
The present invention provides a positive electrode active material which is a lithium transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium transition metal oxide has 60 mol% or more nickel (Ni) with respect the total number of moles of transition metal except lithium, and is doped with at least any one doping element selected from the group consisting of B, Zr, Mg, Ti, Sr, W, and Al, and the positive electrode active material has an average particle diameter (D50) of 4 µm to 10 µm after rolling at a rolling density of 3.0 g/cm3 to 3.3 g/cm3 and has the form of a single particle, and provides a method of preparing the positive electrode active material, a positive electrode including the positive electrode active material, and a lithium secondary battery.