Positive Electrode Sheet Composition for High-Voltage Impedance Control
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Solution Overview
Problem
Lithium-ion batteries face issues with increased direct current impedance and capacity degradation when operated at high temperatures due to electrolyte decomposition, which existing methods partially address but not comprehensively.
Innovation Solution
A positive electrode sheet with a specific composition and structure, including a positive electrode material layer doped or coated with metal elements and a compound represented by formula I, which reduces side reactions and impedance increase by forming a passivation film, optimizing the compacted density and content of the material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the operating voltage of the lithium-ion battery is increased to improve energy density, then the energy density is improved, but the decomposition of the electrolyte is aggravated and by-products are increased, leading to gas generation, capacity degradation, and increased direct current impedance
Solution Approach 1:
The patent introduces a specific compound (Formula I) as an intermediary substance in the electrolyte that mediates between the high voltage operation and electrolyte stability. This compound acts as a mediator that enables high voltage operation while preventing electrolyte decomposition, thus resolving the contradiction between energy density improvement and reliability maintenance.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by incorporating the specific compound of Formula I with defined structural characteristics (R1, R2, R3 groups). This parameter change in electrolyte composition allows the system to operate at high voltages without suffering from electrolyte decomposition, thereby maintaining both high energy density and reliable cycling performance.
2Reliability
If existing electrolyte additives are used to improve high-temperature cycling performance, then the gas expansion and capacity degradation are reduced to a certain extent, but the direct current impedance still increases excessively
Solution Approach 1:
The patent introduces a specific compound (Formula I) as an intermediary substance in the electrolyte that mediates between the high voltage operation and electrolyte stability. This compound acts as a mediator that enables high voltage operation while preventing electrolyte decomposition, thus resolving the contradiction between energy density improvement and reliability maintenance.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by incorporating the specific compound of Formula I with defined structural characteristics (R1, R2, R3 groups). This parameter change in electrolyte composition allows the system to operate at high voltages without suffering from electrolyte decomposition, thereby maintaining both high energy density and reliable cycling performance.
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 solution significantly reduces impedance increase and enhances high-temperature cycling and storage performance of lithium-ion batteries by improving the structural stability of the positive electrode material and the stability of the battery at high temperatures.
Implementation Method 1
including a positive electrode material layer doped or coated with metal elements and a compound represented by formula I, which reduces side reactions and impedance increase by forming a passivation film
Data Source
AI summary
A positive electrode sheet includes a positive electrode current collector and a positive electrode material layer formed thereon. The positive electrode sheet has a potential range of greater than or equal to 4.25 V with respect to metal lithium. The positive electrode material layer includes a positive electrode active material doped or coated with metal elements and a compound represented by formula I. The positive electrode sheet satisfies:0.3≤(m+n)100k≤59;and 50≤m≤10000, 50≤n≤10000, 2.8≤k≤3.8; where m is a content of the compound in the positive electrode material layer; n is a total content of the metal elements doped and coated in the positive electrode material layer; and k is a compacted density of the positive electrode material layer. A characteristic peak appears in a region having a retention time of 6.5 min to 7.5 min.