Cathode Precursor Co-Precipitation for Smaller Primary Particles
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Solution Overview
Problem
The existing methods for preparing positive electrode active material precursors for secondary batteries using batch-type reactors face limitations in reducing primary particle size and surface density, leading to non-uniformity and reduced reactivity during sintering.
Innovation Solution
A method involving a co-precipitation reaction in a batch-type reactor, where a transition metal-containing solution, a basic solution, and an ammonium solution are added, maintaining a molar ratio of ammonium ions to transition metal cations at 0.5 or less and a pH of 11.2 or less, to produce a positive electrode active material precursor with reduced primary particle size and surface density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a batch-type reactor is used to prepare positive electrode active material precursor, then the control of metal composition ratio is easy, but the primary particle size increases and surface density increases as particles grow
Solution Approach 1:
The batch-type reactor process is segmented into multiple controlled stages: initial rapid nucleation phase, intermediate growth phase, and final maturation phase. Each stage uses different addition rates of raw materials and different stirring speeds to control particle development independently, preventing excessive particle growth while maintaining composition control.
Solution Approach 2:
The process dynamically adjusts operating parameters during reaction: stirring speed varies from high (rapid mixing during nucleation) to moderate (controlled growth), temperature is adjusted in stages, and raw material addition rates are modified over time. This dynamic control allows the system to maintain small primary particle size while achieving uniform metal composition ratio.
2Ease of manufacture
If a batch-type reactor is used to prepare positive electrode active material precursor, then the control of metal composition ratio is easy, but the density of particle surface increases as particles grow
Solution Approach 1:
The precipitation process is divided into distinct phases where surface density control is prioritized in early stages. Rapid nucleation creates numerous small particles with high surface area-to-volume ratio, preventing surface densification. Subsequent controlled growth maintains this surface characteristic while achieving target composition.
Solution Approach 2:
The process uses excessive nucleation (creating more nuclei than eventually needed) to ensure a large number of small particles form initially. This excessive nucleation action prevents surface density increase by distributing material across many particles rather than allowing a few particles to grow large and dense at the surface.
3Stability of the object's composition
If the primary particle size of the precursor particle increases, then the surface energy decreases, but the reactivity with lithium source and doping source decreases during sintering
Solution Approach 1:
The process optimizes multiple parameters simultaneously to maintain small primary particle size: controls supersaturation level, adjusts stirring speed, modifies temperature profile, and regulates pH change rate. These parameter changes prevent particle growth that would reduce surface energy and reactivity.
Solution Approach 2:
The process performs preliminary nucleation under controlled conditions to create a large population of small particles before any significant growth occurs. This preliminary action establishes a particle size distribution that maintains high surface energy and reactivity throughout the subsequent sintering process with lithium and doping sources.
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 effectively reduces the primary particle size and surface density of the positive electrode active material precursor, improving capacity, rate capability, cycle characteristics, and resistance increase characteristics when used in lithium batteries.
Implementation Method 1
preparing a positive electrode active material precursor by a co-precipitation reaction while adding a transition metal-containing solution containing transition metal cations, a basic solution, and an ammonium solution to a batch-type reactor
Data Source
AI summary
A method of preparing a positive electrode active material precursor for a secondary battery includes preparing a positive electrode active material precursor by a co-precipitation reaction while adding a transition metal-containing solution containing transition metal cations, a basic solution, and an ammonium solution to a batch-type reactor, wherein a molar ratio of ammonium ions contained in the ammonium solution to the transition metal cations contained in the transition metal-containing solution added to the batch-type reactor is 0.5 or less, and a pH in the batch-type reactor is maintained at 11.2 or less.