Porous Inorganic Cathode Coating for High-Voltage Li-Ion Stability
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Solution Overview
Problem
Lithium-ion batteries face issues with high energy density and charging efficiency due to excessive charge-discharge voltage causing lithium-ion de-intercalation, electrolyte decomposition, and side reactions, leading to capacity degradation and safety hazards, while increasing positive electrode active material capacity results in poor electrolyte retention and ion conductivity.
Innovation Solution
A positive electrode with a porous dielectric inorganic layer of 20 nm to 2000 nm thickness, free from binders, is applied on the surface of the active material layer using vapor deposition, enhancing ion transmission, mechanical stability, and preventing electrolyte side reactions, while maintaining high compaction density and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charge-discharge voltage is increased to improve energy density, then the battery energy density is improved, but lithium-ions de-intercalate excessively causing crystal structure collapse and electrolyte decomposition
Solution Approach 1:
An inorganic coating layer is introduced as an intermediary between the positive electrode active material and the electrolyte. This coating layer prevents direct contact and harmful interactions at high voltages while allowing lithium-ion transport, thereby enabling high energy density operation without structural collapse or electrolyte decomposition.
Solution Approach 2:
A thin inorganic coating film is applied on the surface of the positive electrode active material particles. This film acts as a protective shell that maintains crystal structure stability during high-voltage charging/discharging cycles while permitting ion diffusion, thus resolving the contradiction between energy density and structural reliability.
2Quantity of substance
If the compaction density of the positive electrode is increased to improve capacity, then the battery capacity is improved, but the electrode porosity decreases and ion conductivity degrades
Solution Approach 1:
The inorganic coating layer is designed with a porous structure that contains numerous channels and voids. This porous architecture maintains high ion conductivity even when the electrode compaction density is increased, allowing lithium-ions to efficiently transport through the coating layer while enabling higher capacity through increased active material loading.
3Stability of the object's composition
If a coating layer is applied to stabilize the crystal structure, then the structural stability is improved, but coating shedding and particle agglomeration occur
Solution Approach 1:
The coating process parameters are optimized to achieve uniform coating thickness and strong adhesion. By controlling deposition conditions, the coating is applied evenly without excessive thickness variations that would cause shedding, while preventing particle agglomeration through controlled coating application.
Solution Approach 2:
The positive electrode consists of a composite structure with the inorganic coating layer combined with the active material particles. This composite design ensures strong interfacial bonding between coating and substrate, preventing coating shedding while maintaining structural stability during cycling.
4Stability of the object's composition
If chemically inert inorganic material is used for coating, then the crystal structure is stabilized, but the electrical conductivity becomes poor and DCR increases
Solution Approach 1:
The inorganic coating layer is designed with a porous structure containing numerous channels and voids. This porous architecture provides conduction pathways for electrons and ions, maintaining good electrical conductivity despite the use of chemically inert inorganic materials, thereby reducing DC resistance while preserving structural stability.
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 inorganic layer improves the battery's safety, cycle stability, and capacity retention by stabilizing the electrode interface, reducing gas production, and enhancing ion conductivity and electrolyte retention, thus addressing the limitations of existing lithium-ion batteries.
Implementation Method 1
preparing an inorganic layer having a thickness of 20 nm to 2000 nm on a surface of the at least one positive electrode active material layer away from the current collector by vapor deposition method
Data Source
AI summary
The present disclosure relates to the technical field of energy storage, and in particular, relates to a positive electrode, a method for preparing the positive electrode and an electrochemical device. The positive electrode includes a current collector and a positive electrode active material layer that contains positive electrode active material and is arranged on at least one surface of the current collector. An inorganic layer having a thickness of 20 nm to 2000 nm is arranged on the surface of the at least one positive electrode active material layer away from the current collector. The inorganic layer is a porous dielectric layer containing no binder, and the inorganic layer has a porosity of 10%˜60%. The positive electrode active material layer according to the present disclosure significantly improves the cycle performance, high-temperature storage performance and safety of the electrochemical device.