Layered Nickel Oxide Oxidative Delithiation for Higher Ni(IV) Yield
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Solution Overview
Problem
Existing methods for chemically charging alkali metal-containing transition metal oxides, such as acid-promoted disproportionation, are inefficient due to low yields, incomplete oxidation, and extended treatment times, often requiring expensive reagents.
Innovation Solution
A multi-step hybrid process involving the treatment of alkali metal-containing layered nickel oxide with a peroxydisulfate salt at an elevated temperature to form a Ni(IV)-containing mixture, followed by treatment with a mineral acid to further form an alkali metal-deficient layered nickel oxide electrochemically active cathode material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If acid-promoted disproportionation is used to chemically charge alkali metal-containing transition metal oxides, then the process is simple to implement, but the yield is low and treatment time is extended
Solution Approach 1:
The chemical charging process is divided into two sequential steps: first oxidative demetallation with persulfate salt to remove alkali metals and oxidize transition metals to +4 state, then subsequent treatment with mineral acid to complete the charging process. This segmentation allows each step to be optimized independently, achieving high yield while maintaining operational simplicity.
Solution Approach 2:
The oxidative demetallation step is performed as a preliminary action before acid treatment. By pre-removing alkali metals and oxidizing transition metals to the +4 state, the subsequent acid treatment becomes more efficient and achieves higher yields in less time, rather than attempting to accomplish both tasks simultaneously.
2Ease of manufacture
If acid-promoted disproportionation is used, then the process requires minimal reagents, but the oxidation of transition metal is incomplete and treatment time is extended
Solution Approach 1:
The oxidation state of transition metals is changed from +3 to +4 through persulfate treatment before acid exposure. This parameter change enables more complete oxidation and reduces the time required for subsequent acid treatment, as the transition metal is already in a higher oxidation state and requires less time to reach the desired charged state.
3Productivity
If strong soluble chemical oxidants are used for direct oxidation, then oxidation efficiency is improved, but the process becomes complex and expensive
Solution Approach 1:
Persulfate salt serves as an intermediary oxidizing agent that generates sulfate radicals in situ. These radicals provide strong oxidation capability comparable to expensive reagents like nitrosonium salts, but the persulfate system is simpler and more cost-effective. The intermediary approach maintains high oxidation efficiency while reducing process complexity and cost.
4Ease of manufacture
If acid-promoted disproportionation is used, then the process is straightforward, but particle size reduction occurs due to M(II) ion dissolution
Solution Approach 1:
The persulfate treatment performs a preliminary anti-action by oxidizing transition metals to the +4 state before acid exposure, preventing the formation of soluble M(II) ions that would cause particle dissolution. By preemptively establishing the higher oxidation state, the subsequent acid treatment does not generate M(II) ions, thus preserving particle size while maintaining process simplicity.
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 method achieves high yields (>70%) of Ni(IV)-containing alkali metal-deficient layered nickel oxide with improved discharge capacity and larger particle size distribution, while minimizing environmental waste and reducing the formation of gamma-nickel oxyhydroxide.
Implementation Method 1
reacting an alkali metal-containing layered nickel oxide having a formula A 1-a Ni 1+a O 2 with an oxidant comprising a persulfate salt to form a Ni(IV)-containing mixture
Implementation Method 2
acid-promoted disproportionation of the transition metal, e.g., by treatment with a mineral acid
Data Source
Figure 1
AI summary
Provided are methods of preparing an electrochemically active cathode material including the steps of (a) combining an alkali metal-containing layered nickel oxide having a formula A1-aNi1+aO2, wherein A comprises an alkali metal and 0 < a ≤ 0.2, with an oxidant comprising a peroxydisulfate salt and/or a monopersulfate salt to form a mixture, (b) heating the mixture to form a Ni(IV) containing mixture including a Ni(IV) containing electrochemically active cathode material; (c) adding to the Ni(IV) containing mixture of step (b) a mineral acid; and (d) heating the mixture of step (c) to form an additional amount of the Ni(IV) containing electrochemically active cathode material, the Ni(IV) containing electrochemically active cathode material formed in steps (b) and (d) having a general formula AxHyNi1+aO2, wherein A comprises an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 ≤ a ≤ 0.2.