Core-Shell Hydroxide Precipitation for Cathode Composition Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods struggle to achieve a desired total metal composition and maintain constant molar ratios between the core and shell portions of lithium-ion battery cathode active material precursors, particularly in core-shell structured particles, limiting the performance and stability of lithium-ion secondary batteries.
Innovation Solution
A method involving two precipitation stages is employed to form core-shell particles, where the first stage forms the core portion and the second stage forms the shell portion, with precise control of metal compositions and ratios using equations to determine the amounts of metals M c' and M s' in each stage, ensuring a predetermined overall metal composition and constant molar ratios between the core and shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a co-precipitation process is used to prepare transition metal hydroxides, then the active material can be produced for lithium-ion batteries, but it is difficult to achieve a desired total metal composition and maintain constant molar ratios between core and shell portions
Solution Approach 1:
The precipitation process is divided into two distinct stages: a first precipitation stage that forms the core portion with a specific metal composition, and a second precipitation stage that forms the shell portion with a different metal composition. This segmentation allows independent control of core and shell compositions, enabling precise achievement of desired total metal composition and constant molar ratios between core and shell portions.
Solution Approach 2:
The core portion is formed first in the first precipitation stage before the shell portion is formed in the second stage. This preliminary action establishes the core structure with controlled metal composition, providing a foundation upon which the shell is subsequently built, ensuring that the final particle achieves the target overall metal composition with maintained molar ratios.
2Quantity of substance
If lithium-nickel composite oxide is used to increase charging and discharging capacity, then battery capacity increases, but thermal stability decreases compared to lithium-cobalt or lithium-nickel-cobalt-manganese oxides
Solution Approach 1:
Different regions of the particle are given different metal compositions to fulfill different functions: the core portion contains metals optimized for charging and discharging capacity (such as nickel-rich composition), while the shell portion contains metals optimized for thermal stability (such as cobalt or nickel-cobalt-manganese composition). This local quality differentiation allows the particle to simultaneously achieve high capacity and high thermal stability.
Solution Approach 2:
The particle is constructed as a composite structure with core and shell portions having different metal compositions. The core uses nickel-rich composition for high capacity, while the shell uses cobalt or nickel-cobalt-manganese composition for thermal stability. This composite material approach combines the advantages of different metal oxides within a single particle structure, achieving both high capacity and high thermal stability.
3Reliability
If different transition metal compositions are used in core and shell portions, then battery characteristics are improved, but it becomes challenging to repeat precipitation to achieve desired target total metal ratio while keeping molar ratios constant
Solution Approach 1:
The method incorporates feedback control by calculating the amounts of metals Mc' and Ms' to be provided in the first and second precipitation stages based on the target overall metal composition and the desired shell-to-core ratio. This feedback mechanism ensures that each precipitation stage contributes the correct amount of metal to achieve the target composition, enabling consistent reproduction of the desired metal ratios across multiple batches.
Solution Approach 2:
The method controls the precipitation process by adjusting key parameters including the amounts of metals Mc' and Ms' provided in each stage, the shell-to-core ratio ε, and the median particle diameter D50. By precisely controlling these parameters according to the target composition requirements, the method achieves consistent metal ratios in the core-shell structure across repeated precipitation processes.
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 method achieves a predetermined total metal composition with varying metal compositions on the surface and inside the particles, maintaining constant molar ratios, resulting in improved cathode active material precursors with enhanced charging and discharging capacity and thermal stability.
Implementation Method 1
combining a metal salt solution and an alkali solution... thereby increasing the sizes of particles comprising M c'-hydroxide in a slurry thus formed
Data Source
Figure 1(a)~1(f)
Figure 2~3(d)
Figure 4(a)~4(d)
AI summary
A method for preparing a metal-bearing M'-hydroxide particulate material, the method comprising the steps of: (a) determining a target value (D') for a median particle diameter D50 of the material to be prepared, preferably the D' being in the range of 3-20 µm ; (b) combining, during a time period (T1-T2), streams of an aqueous solution (βc) containing salts of metals Mc' and an aqueous solution (ω) containing an alkali metal hydroxide in a stirred tank reactor at a pH of 10.5-12.5, determined at 20 °C, thereby increasing the sizes of particles comprising Mc'-hydroxide in a slurry thus formed; (c) continuing step (b) until the D50 of the particles reaches approximately a value of Dc, wherein the amount of metals Mc' provided by the flow of solution (βc) during the period (T1-T2) is θc, wherein Dc=1−ε∗D'3, wherein ε is a predetermined value selected from the range of 0.01-0.9; (d) providing at least a fraction Sc of the slurry obtained in step (c) either to the same or to a different stirred tank reactor, wherein 0<Sc≤1; (e) combining the fraction Sc of the slurry with streams of an aqueous solution (βs) containing salts of metals Ms' and the solution (ω) in the reactor at a pH of 10.5-12.5, determined at 20 °C, thereby forming a layer comprising M,'-hydroxide on the particles comprising Mc'-hydroxide of the slurry; and (f) continuing step (e) until the amount of metals Ms' combined in step (e) reaches a value of θs, which θs=11−ε−1∗θc, wherein the Mc'=Ni1-xc-yc-zcMnxcCoycAzc with 0≤xc≤0.85, 0≤yc≤0.35, 0≤zc<0.1 and 0.15≤1-xc-yc-zc≤1, and wherein the Ms'=Ni1-xs-ys-zsMnxsCoysAzs with 0≤xs≤0.85, 0.05≤ys≤1, 0≤zs<0.1 and 0≤1-xs-ys-zs≤0.95.