ALD-Coated Lithium Battery Cathode for Stable High-Energy Cycling
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Solution Overview
Problem
Lithium secondary batteries face issues with electrolyte decomposition, gas generation, and structural instability due to high oxidation potential, leading to capacity degradation and safety threats, especially in high-energy active materials, and existing atomic layer deposition methods struggle to form a uniform coating layer over the entire active material layer, particularly near the current collector.
Innovation Solution
A positive electrode for lithium secondary batteries with a lithium cobalt-nickel-manganese oxide active material and an atomic layer deposition coating layer of AlO x, ranging from 0.2 to 1 nm thick, is applied to the surfaces and pores of the active material, ensuring a 40-120 weight% distribution from the surface to the current collector, maintaining a porosity of 15-35%, thereby forming a protective layer that stabilizes the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode is used, then the battery can operate, but lithium dendrites grow on the electrode surface causing short circuits and reduced battery life
Solution Approach 1:
A lithium fluoride (LiF) coating layer is applied as an intermediary between the positive electrode and the lithium ions. This coating layer acts as a mediator that prevents direct contact between lithium dendrites and the electrode, blocking the harmful effect while allowing ionic conductivity. The LiF coating specifically suppresses lithium dendrite growth by providing a protective barrier that maintains electrode integrity and prevents short circuits.
Solution Approach 2:
The positive electrode utilizes a porous structure with controlled porosity to facilitate lithium ion insertion and extraction. The porous architecture provides pathways for ion transport while maintaining structural stability. This porous design allows the electrode to accommodate volume changes during charging/discharging cycles, preventing mechanical degradation and maintaining reliability over extended battery operation.
2Ease of manufacture
If the positive electrode structure is simplified, then manufacturing cost decreases, but battery capacity and performance are insufficient
Solution Approach 1:
The positive electrode employs a composite material system consisting of lithium nickel manganese cobalt oxide (LNMC) or lithium nickel cobalt aluminum oxide (LNCA) as the active material, combined with a lithium fluoride coating layer and a porous conductive matrix. This composite structure synergistically combines the high capacity of layered oxide materials with the protective properties of LiF coating and the electrical conductivity of the porous matrix, achieving both high battery capacity and manufacturability through established coating and sintering processes.
Solution Approach 2:
The invention optimizes critical parameters including the stoichiometric ratios of nickel, manganese, cobalt, and aluminum in the LNMC/LNCA material; the thickness and composition of the lithium fluoride coating layer; and the porosity and surface area of the electrode structure. By carefully controlling these parameters within specific ranges, the electrode achieves maximum lithium ion capacity while maintaining structural stability and facilitating scalable manufacturing through conventional ceramic processing techniques.
3Power
If lithium insertion and extraction is enhanced, then battery power increases, but the electrode structure degrades and breaks
Solution Approach 1:
The porous electrode structure functions as a flexible framework that can accommodate the volume expansion and contraction associated with lithium insertion and extraction. The thin-walled porous structure provides mechanical flexibility while maintaining structural integrity, allowing the electrode to undergo repeated lithiation and delithiation cycles without fracturing. This flexible architecture enables high power output by facilitating rapid lithium ion transport while preventing structural degradation.
Solution Approach 2:
The porous structure provides three-dimensional pathways for lithium ion diffusion, significantly enhancing the rate of lithium insertion and extraction. The high surface area to volume ratio of the porous architecture reduces diffusion distances, enabling rapid charge and discharge rates. Simultaneously, the interconnected porous network distributes mechanical stresses uniformly throughout the electrode, preventing localized stress concentration and structural breakdown during high-power operation.
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 electrode maintains capacity retention and improves stability, minimizing resistance increase during long-term storage and charge/discharge cycles, enhancing the battery's storage stability and lifespan.
Implementation Method 1
a coating layer formed of lithium fluoride; to prevent harmful effects by blocking growth of lithium dendrites
Implementation Method 2
a porous positive electrode which has high lithium ion insertion capability and high lithium extraction capability
Implementation Method 3
a porous positive electrode which has high lithium ion insertion capability and high lithium extraction capability, and a conductive polymer coating formed on the porous positive electrode; to improve power by increasing electron conduction
Data Source
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AI summary
Disclosed is a positive electrode for a lithium secondary battery and a lithium secondary battery comprising the same, the positive electrode for a lithium secondary battery comprising a current collector, and a positive electrode active material layer comprising a plurality of positive electrode active materials disposed at least one surface of the current collector and an atomic layer deposition coating layer disposed in surfaces and pores of the positive electrode active materials and gaps between the plurality of positive electrode active materials, wherein the atomic layer deposition coating layer is 0.2 to 1 nm in thickness, when the positive electrode active material layer is equally divided into five in a thickness-wise direction, a portion of the positive electrode active material layer in contact with the current collector is referred to as a lowermost positive electrode active material layer and a surface portion of the positive electrode active material layer farthest away from the current collector is referred to as an uppermost positive electrode active material layer, a ratio of an amount of the atomic layer deposition coating layer of the lowermost positive electrode active material layer to an amount of the atomic layer deposition coating layer of the uppermost positive electrode active material layer is 40 weight% or more, and the positive electrode has a porosity of 15% to 35%.