Direct Metal Oxalate Precursor Synthesis for Li-Ion Cathodes

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Solution Overview

Problem

The existing methods for producing lithium ion battery cathode active materials (CAMs) face challenges related to material waste and inefficiencies in the supply chain, particularly in forming metal carbonates from metal sulfates, which are low in metal content and require additional purification steps, increasing costs and complexity.

Innovation Solution

A method is developed to directly form metal salt precursors from elemental metals using multi-carboxylic acids, eliminating the need for metal sulfates and carbonates, and involving a process of reacting elemental metals with nitric acid and multi-carboxylic acids to create oxide precursors, which are then calcined to produce lithium metal oxide cathodes in spinel or rock-salt structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If metal sulfates are used as feedstock to form metal carbonates, then the supply chain is established, but the metal content is low (21 wt% for nickel) and additional purification steps are required, increasing cost and complexity

Engineering Contradiction:

Improvemetal contentVSAvoidpurification steps

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The invention extracts the problematic intermediate steps (sulfate formation and purification) from the process chain by using elemental metals as direct feedstock. This eliminates the need to handle low-concentration metal sulfates and the associated purification complexity, directly obtaining high-purity metal oxalate precursors.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The process segments the traditional sulfate-based route by replacing it with a direct oxidation pathway. Elemental metals are directly oxidized by oxalic acid to form metal oxalates, bypassing the sulfate intermediate entirely and simplifying the overall process architecture.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If metal sulfates are converted to metal carbonates through digestion in oxalic acid, then the oxalate precursor is formed, but the Na2SO4 waste stream is created and purity is insufficient without additional purification

Engineering Contradiction:

ImprovepurityVSAvoidwaste stream

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The invention converts the traditionally harmful waste stream (Na2SO4 from sulfate digestion) into a non-issue by eliminating the sulfate step entirely. Elemental metals directly react with oxalic acid to form metal oxalates without generating sulfate waste, transforming a pollution problem into a clean process.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Instead of the conventional approach of converting sulfates to carbonates/oxalates, the invention inverts the logic by using elemental metals as the starting point. This reversal eliminates the need for sulfate formation and subsequent purification, directly achieving high-purity metal oxalate precursors.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If the traditional sulfate-carbonate-oxalate process is used, then the CAM is formed, but the number of process steps is increased and some steps are detrimental to sintering and calcining

Engineering Contradiction:

Improveprocess efficiencyVSAvoidnumber of process steps

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The invention merges multiple traditional process steps (sulfate formation, purification, carbonate precipitation, and oxalate formation) into a single direct oxidation step. Elemental metals react directly with oxalic acid to form metal oxalates, consolidating the process and eliminating detrimental intermediate steps that affect sintering and calcining.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention performs preliminary oxidation of elemental metals to form metal oxalate precursors in advance, using oxalic acid as both the oxidizing agent and the source of the oxalate group. This preliminary action creates a ready-to-calcine precursor that is optimized for subsequent thermal processing, eliminating the need for intermediate carbonate formation and purification steps.

Inventive Principle:

Principle #10Preliminary action

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 streamlines the production process, reduces waste, and enables the formation of high nickel CAMs with improved cost and purity, enhancing the efficiency and stability of lithium ion batteries.

Implementation Method 1

reacting elemental metals with oxalic acid to form metal oxalate precursors

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

The mixed oxalate precursor is then calcined to make the CAM

Methodology Applied

Scientific EffectCalcination: Pyrolysis

Data Source

PatentUS20220064019A1Alternative One-Pot Process for Making a Cam Precursor Using Metal Feedstocks

Publication Date: 2022.03.03 NANO ONE MATERIALS

AI summary

The present invention provides a method for forming a lithium ion cathode material. The method comprises reacting elemental metal with a multi-carboxylic acid to form an oxide precursor and heating the oxide precursor to form the lithium ion cathode material. In a preferred embodiment the elemental mixture comprises at least two of Ni, Mn, Co and Al.