Positive Electrode Coating for Low-Resistance Secondary Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries with high-adhesion safety coatings experience high internal resistance and significant resistance growth rates during high-temperature tests, leading to performance degradation and reduced lifespan due to gas accumulation and side reactions at the interface of the electrode layers.
Innovation Solution
A secondary battery design with controlled particle size and composition of the first material layer, including a matrix of LiFekM(1-k)PO4 and a carbon coating layer, enhances peel strength and reduces gas accumulation and side reactions, thereby lowering internal resistance and growth rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-adhesion safety coating is applied on the positive electrode current collector to reduce short-circuit points, then safety is improved, but internal resistance increases significantly
Solution Approach 1:
The patent changes the particle size parameter of the safety coating material to Dv10=0.3-2.0μm (optimally 0.5-1.5μm), which is smaller than conventional coatings. This parameter change reduces the coating thickness and density, thereby reducing internal resistance while maintaining safety function through the fine particle distribution that provides adequate coverage.
Solution Approach 2:
The patent uses a composite material system consisting of LiFekM(1-k)PO4 matrix particles with carbon coating layer. The carbon-coated lithium iron phosphate or lithium iron manganese phosphate particles combine the safety function of the phosphate material with the conductivity enhancement of the carbon layer, reducing internal resistance while preventing short circuits.
2Reliability
If a high-adhesion safety coating is applied on the positive electrode current collector, then short-circuit resistance is improved, but internal resistance growth rate increases after high-temperature storage
Solution Approach 1:
The patent optimizes the particle size parameter Dv10 to 0.3-2.0μm, which creates a thinner, more uniform coating that allows better electrolyte penetration and ion transport. This parameter optimization reduces the initial internal resistance and minimizes the growth rate during high-temperature storage by preventing excessive coating degradation.
Solution Approach 2:
The carbon coating layer is applied locally on the surface of each matrix particle, providing localized conductivity enhancement at the particle surface where electrochemical reactions occur. This local quality improvement ensures efficient electron transfer while maintaining the safety function of the phosphate matrix, reducing overall internal resistance and its growth over time.
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
The controlled particle size and composition of the first material layer improve the electrical performance and safety of lithium-ion batteries by reducing internal resistance and defects, while maintaining high peel strength and conductivity.
Implementation Method 1
the carbon coating layer on the surface of the matrix undergoes increased side reactions at a high temperature, causing the byproducts to accumulate on the matrix surface and within the first material layer
Data Source
AI summary
A secondary battery includes a positive electrode plate, where the positive electrode plate includes a positive electrode current collector, a first material layer, and a second material layer that are stacked; the positive electrode current collector includes a metal layer; the first material layer is disposed between the positive electrode current collector and the second material layer; the first material layer includes first material particles; the first material particle includes a matrix and a carbon coating layer on a surface of the matrix; Dv10 of the first material particles is D1 μm, where 0.3≤D1≤2.0; and the matrix includes at least one of LiFekM(1-k)PO4, where 0≤k≤1, and the M element is selected from at least one of manganese, cobalt, magnesium, calcium, zinc, chromium, or lead. The secondary battery of this application has a low internal resistance and internal resistance growth rate. An electronic apparatus including the secondary battery is further provided.