Positive Electrode Mixture Composition for High-Ni Viscosity Stability
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Solution Overview
Problem
Existing positive electrode mixtures for secondary batteries face challenges in maintaining low viscosity over time, especially when containing high proportions of Ni, which affects battery capacity and productivity.
Innovation Solution
A positive electrode mixture comprising polyvinylidene fluoride (PVdF) combined with specific fluorinated monomers and polar group-containing monomers, along with additives like diketone compounds and organophosphorus compounds, to stabilize viscosity and enhance capacity retention after high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a positive electrode mixture contains high proportions of Ni to improve battery capacity, then the battery capacity increases, but the viscosity of the mixture increases over time affecting productivity
Solution Approach 1:
The patent modifies the chemical composition parameters of the binder by incorporating specific fluorinated monomers (such as hexafluoropropylene, fluoroalkyl vinyl ether) and polar group-containing monomers (such as acrylic acid, methacrylic acid) into the polyvinylidene fluoride structure. This chemical parameter change enables the binder to maintain stable viscosity over time even when used with high-Ni positive electrode active materials, thereby resolving the contradiction between achieving high battery capacity and maintaining productivity.
2Reliability
If a positive electrode mixture is prepared with high Ni content to enhance capacity, then the residual capacity rate after high-temperature storage improves, but the viscosity increases significantly over time
Solution Approach 1:
The patent creates a composite binder material by combining polyvinylidene fluoride with fluorinated monomer units and polar group-containing monomer units in a specific molecular structure. This composite material approach provides both the viscosity stability needed for manufacturing and the capacity retention performance required for reliable battery operation after high-temperature storage, thus resolving the contradiction between reliability and compositional stability.
3Ease of manufacture
If polyvinylidene fluoride is used as a simple binder to maintain low cost and ease of manufacture, then manufacturing simplicity is improved, but viscosity stability over time deteriorates
Solution Approach 1:
The patent applies local quality modification by introducing specific functional units (fluorinated monomers and polar group-containing monomers) at targeted positions within the polyvinylidene fluoride polymer structure. Rather than completely replacing the simple PVdF binder, the invention locally enhances specific molecular segments to provide viscosity stability while maintaining the overall simplicity and ease of manufacture associated with PVdF-based binders.
Data Source
AI summary
A positive electrode mixture containing: a polyvinylidene fluoride (A); a positive electrode active material (C) represented by the general formula (C): LiyNi1-XMxO2, wherein x is 0.01≤x≤0.7, y is 0.9≤y≤2.0, and M represents a metal atom (excluding Li and Ni); and an additive (D), wherein the polyvinylidene fluoride (A) is a combination of: (A2) a polymer containing vinylidene fluoride unit and a fluorinated monomer unit; and at least one selected from the group consisting of (A3) a polymer containing vinylidene fluoride unit and a polar group-containing monomer unit, and (A4) a polymer containing vinylidene fluoride unit, a fluorinated monomer unit, and a polar group-containing monomer unit. Also disclosed is a positive electrode famed from the positive electrode mixture and a secondary battery including the positive electrode.