High-Nickel Positive Electrode Composition for Capacity and Cycle Life
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries face challenges in simultaneously achieving high initial discharge capacity and good cyclic characteristics, particularly when using composite oxides with high nickel content.
Innovation Solution
Incorporating a positive electrode mixture layer with composite oxide particles containing Ni, Co, and Li, along with Mn or Al, and polyvinyl alcohol (PVA) having a degree of saponification of 85% or less, where the ratio of BET specific surface area to theoretical specific surface area (A/B) is controlled between 1.0 and 4.3, enhancing adhesion and electron conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the proportion of Ni is increased to 50 mol % or more to obtain larger battery capacity, then the initial discharge capacity is improved, but the cyclic characteristics deteriorate
Solution Approach 1:
The patent changes the surface area parameter by controlling the volume average particle size of composite oxide particles to 3 μm or less, which increases the BET specific surface area. This parameter change allows high Ni content (50 mol % or more) to be used while improving cyclic characteristics through enhanced surface area-to-volume ratio, resolving the contradiction between capacity and cycling stability
Solution Approach 2:
The patent uses composite oxide particles containing multiple metal elements (Ni, Co, Li, and at least one of Mn or Al) with specific compositional ratios. This composite material approach allows the high Ni content to provide high capacity while the other elements contribute to structural stability during cycling, simultaneously achieving both improved initial discharge capacity and good cyclic characteristics
2Reliability
If the volume average particle size is reduced to increase BET specific surface area, then cyclic characteristics are improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent specifies a precise parameter range for volume average particle size (3 μm or less) and controls the BET specific surface area to theoretical specific surface area ratio within 1.0 to 4.3. These defined parameter ranges provide clear manufacturing targets that balance the need for small particle size (for good cyclic characteristics) with manufacturability constraints
3Quantity of substance
If polyvinyl alcohol with degree of saponification of 85% or less is used to enhance adhesion, then initial discharge capacity is improved, but electron conductivity may be affected
Solution Approach 1:
The patent specifies a particular parameter range for the degree of saponification of polyvinyl alcohol (85% or less), which optimizes the balance between adhesion properties and electrical conductivity. This parameter control allows the binder to provide sufficient adhesion for high initial discharge capacity while maintaining adequate electron conductivity for reliable battery performance
Data Source
AI summary
A positive electrode for non-aqueous electrolyte secondary batteries has a mix layer which contains composite oxide particles each containing Ni, Co and Li and also contains Mn and/or Al, a conductive material, and poly(vinyl alcohol) having a saponification degree of 85% or less. In the composite oxide particles, the content of Ni relative to the total number of moles of metal elements other than Li is 50 mol % or more, and the ratio of the BET specific surface area A (m2/g) to the theoretical specific surface area B (m2/g) as determined in accordance with the below-mentioned formula, i.e., (A/B), is 1.0 to 4.3 exclusive. The theoretical specific surface area B (m2/g)=6/((true density (g/cm3))×(volume average particle diameter (μm))).