Positive Electrode Slurry Composition for High-Nickel Stability
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Solution Overview
Problem
Conventional slurry compositions for non-aqueous secondary batteries, particularly those using nickel-containing positive electrode active materials, face issues with stability and output characteristics due to alkali content leading to pH increase and thickening, resulting in suboptimal performance.
Innovation Solution
A slurry composition with a nickel proportion among transition metals between 30.0 mol% and 100.0 mol% and a copolymer containing a nitrile group-containing monomer unit (70.0 mass% to 96.0 mass%) and a basic group-containing monomer unit (0.1 mass% to 5.0 mass%), along with optional acidic and (meth)acrylic acid ester monomer units, is used to enhance stability and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a Ni-containing positive electrode active material is used to increase battery capacity, then the battery capacity increases, but the slurry composition stability deteriorates due to pH increase and thickening from residual alkali content
Solution Approach 1:
The patent introduces a specific binder as an intermediary substance between the Ni-containing active material and the slurry matrix. This binder mediates the interaction by buffering the pH increase from residual alkali, preventing direct adverse effects on slurry stability while maintaining the high capacity benefits of Ni-containing materials.
Solution Approach 2:
The patent changes the chemical composition parameters of the binder, specifically using a copolymer with nitrile groups and basic groups in controlled ratios. This parameter change allows the binder to neutralize or buffer the pH increase from alkali content, maintaining slurry stability despite the presence of Ni-containing active material.
2Ease of manufacture
If conventional binders are used with Ni-containing active materials, then the manufacturing process is simple, but the output characteristics of the battery deteriorate
Solution Approach 1:
The patent modifies the binder's chemical structure parameters by incorporating specific functional groups (nitrile and basic groups) in defined ratios. This enables the binder to maintain slurry stability and enable proper electrode formation, thereby achieving excellent output characteristics while keeping the manufacturing process relatively simple.
Solution Approach 2:
The patent uses a composite binder structure combining different monomer units (nitrile-containing and basic-group-containing) in specific proportions. This composite approach creates a binder with dual functionality: maintaining manufacturing ease while enabling superior battery output characteristics through controlled chemical interactions.
3Quantity of substance
If the proportion of nickel in the positive electrode active material is increased to enhance capacity, then the battery capacity increases, but the slurry composition thickens over time due to pH increase from alkali content
Solution Approach 1:
The specialized binder acts as a time-dependent intermediary that continuously buffers pH changes throughout the storage period. This allows the slurry to maintain stable viscosity and composition over extended periods, enabling the use of high-nickel active materials without suffering from progressive thickening.
Solution Approach 2:
The patent changes the temporal stability parameters of the slurry by introducing a binder with pH-buffering capacity. This parameter change ensures that even as time progresses and alkali content gradually increases pH, the slurry viscosity remains stable, preventing thickening over the storage and usage period.
Data Source
AI summary
Provided is a slurry composition for a non-aqueous secondary battery positive electrode that has excellent stability and enables formation of a positive electrode mixed material layer that causes a non-aqueous secondary battery to display excellent output characteristics. The slurry composition contains a positive electrode active material and a copolymer. The proportion constituted by nickel among transition metal in the positive electrode active material is at least 30.0 mol% and not more than 100.0 mol%. The copolymer includes a nitrile group-containing monomer unit in a proportion of at least 70.0 mass% and not more than 96.0 mass% and a basic group-containing monomer unit in a proportion of at least 0.1 mass% and not more than 5.0 mass%.