Cathode Precursor Co-Precipitation With Low Ammonium and pH Control
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Solution Overview
Problem
The existing methods for preparing positive electrode active materials for lithium secondary batteries, such as those using lithium cobalt oxide, face limitations due to cobalt price instability and non-uniformity in particle size and composition when using batch-type reactors, affecting reactivity and sintering uniformity.
Innovation Solution
A method involving a co-precipitation reaction in a batch-type reactor with a controlled molar ratio of ammonium ions to transition metal cations and maintaining a pH of 11.2 or less, which reduces primary particle size and surface density, and subsequent sintering with a lithium source to form a lithium transition metal oxide.
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 reaction time elapses, reducing reactivity with lithium source and doping source
Solution Approach 1:
The batch-type reactor process is segmented into multiple controlled addition stages. Raw materials are added in specific sequences with controlled intervals, dividing the single reaction process into multiple phases. This segmentation allows the system to maintain ease of composition control while preventing excessive particle growth and surface densification that would reduce reactivity.
Solution Approach 2:
The patent implements periodic action through controlled intermittent addition of raw materials during the batch reaction. Instead of continuous or single-stage addition, materials are added at periodic intervals with specific time gaps. This periodic addition pattern maintains uniform particle size distribution and prevents surface densification while keeping the batch reactor's composition control advantage.
2Shape
If the primary particle size of the precursor particle increases and the density of the particle surface increases, then surface energy decreases, but reactivity with lithium source and doping source decreases and uniform sintering becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling reaction parameters including temperature, pH, and most importantly, the timing and rate of raw material addition. By changing the temporal parameters of material addition and maintaining specific pH ranges, the process prevents excessive particle growth and surface densification, thereby maintaining high surface energy, reactivity, and uniform sintering 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
This approach results in a positive electrode active material with improved capacity, rate capability, and cycle characteristics, enhancing the performance and stability of 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
Implementation Method 2
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
Implementation Method 3
subsequent sintering with a lithium source to form a lithium transition metal oxide
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.