Metal Sulfide Coated Lithium Metal Oxide Cathode
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Solution Overview
Problem
Cathode active materials with high nickel content in lithium secondary batteries are vulnerable to moisture, undergo side reactions with electrolytes, and experience lattice changes during charging/discharging, leading to rapid deterioration and reduced lifetime due to electrolyte penetration through cracks in the grain boundaries.
Innovation Solution
A cathode active material with a lithium metal oxide core coated with a metal sulfide layer on its surface and inner grain boundaries, formed through dry mixing and heat treatment, to suppress side reactions and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a water-based coating is used for surface modification, then the coating process is simple and low-cost, but high nickel content cathode active materials deteriorate in distilled water and solvents making it difficult to apply
Solution Approach 1:
The patent changes the chemical composition parameters of the coating material from water-based to organic solvent-based system. The coating solution uses solvents like N-methyl-2-pyrrolidone, dimethyl carbonate, or ethyl methyl carbonate instead of water, fundamentally altering the chemical environment to prevent deterioration of high nickel content materials while maintaining coating applicability
Solution Approach 2:
The patent introduces an organic solvent as an intermediary medium between the coating material and the high nickel content cathode active material. This intermediary prevents direct harmful interaction between water/solvent and the sensitive cathode material, enabling successful coating application
2Quantity of substance
If the cathode active material has high nickel content for high capacity, then the battery capacity increases, but side reactions with electrolyte occur due to highly reactive Ni4+ and lattice changes during charging/discharging
Solution Approach 1:
The patent creates a composite structure by coating the high nickel content cathode active material with aluminum oxide (Al2O3) and/or aluminum hydroxide (Al(OH)3). This composite approach combines the high capacity benefits of nickel-rich materials with the chemical stability and protective properties of aluminum-based coating materials
Solution Approach 2:
The patent applies a protective coating of aluminum oxide and/or aluminum hydroxide before the cathode active material can undergo harmful side reactions with the electrolyte. This preliminary protective layer prevents the highly reactive Ni4+ surfaces and lattice structures from directly interacting with the electrolyte during charging/discharging cycles
3Device complexity
If coating is applied only on the surface in the form of islands, then the coating process is simple, but sudden lattice change during charging/discharging causes cracks and electrolyte penetration into grain boundaries
Solution Approach 1:
The patent enhances the coating at critical locations, particularly at grain boundaries and internal surfaces, where aluminum hydroxide provides localized protection. The coating is not uniformly distributed but concentrated where it is most needed to prevent electrolyte penetration during lattice expansion/contraction
Solution Approach 2:
The patent performs preliminary coating treatment to pre-fill cracks and grain boundaries before the cathode material undergoes charging/discharging cycles. The aluminum oxide and aluminum hydroxide coating is applied in advance to create a protective network that prevents subsequent electrolyte infiltration when lattice changes occur
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 metal sulfide coating effectively prevents electrolyte penetration and side reactions, significantly improving the lifetime characteristics of the battery by maintaining structural integrity and reversible lithium intercalation.
Implementation Method 1
a coating formed on a surface and inner grain boundaries of the core... the coating layer may include a metal sulfide... effectively prevents electrolyte penetration and side reactions
Implementation Method 2
formed through dry mixing and heat treatment
Data Source
AI summary
Provided are a cathode active material for a lithium secondary battery, a cathode and a lithium secondary battery each including the same, and a method of manufacturing the same. The cathode active material for a lithium secondary battery includes a core including a lithium metal oxide and a coating layer formed on a surface and the inner grain boundaries of the core, wherein the coating layer includes a metal sulfide.