Phosphorus-Doped Cathode Coating for Low-Resistance High-Nickel Batteries
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Solution Overview
Problem
High nickel positive electrode active materials in lithium secondary batteries face issues such as electrolyte decomposition, gas generation, and structural instability due to high oxidation potential, leading to reduced capacity retention and safety concerns, with existing coating methods failing to form uniform and effective layers on complex surface structures.
Innovation Solution
A phosphorus-doped aluminum oxide coating layer with a thickness of 0.1 nm to 2.0 nm is applied using atomic layer deposition, improving the stability and energy density of the positive electrode active material while preventing increases in interfacial and cell resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is formed on high nickel positive electrode active material to improve stability, then capacity retention is improved, but interfacial resistance and cell resistance increase
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by incorporating phosphorus-doped aluminum oxide with specific molar ratios (Al2O3: 80-95 mol%, P2O5: 5-20 mol%) to achieve optimal balance between stability and conductivity. The doping concentration and oxidation state are carefully controlled to maintain low resistance while providing protective function.
Solution Approach 2:
The patent uses a composite coating material consisting of aluminum oxide as the base matrix doped with phosphorus compounds. This composite structure combines the high stability of Al2O3 with the conductivity-enhancing properties of phosphorus, creating a coating that simultaneously provides protection and maintains electrical performance.
2Manufacturing precision
If a boron-based coating layer is formed to achieve uniform coating, then coating uniformity is improved, but rolling density decreases and energy density is reduced
Solution Approach 1:
The patent changes the material composition from boron-based to phosphorus-doped aluminum oxide, which has different physical and chemical properties. This material substitution maintains coating uniformity while avoiding the glassy nature of boron that causes rolling density reduction, thereby preserving energy density.
3Reliability
If an inorganic or organic coating layer is formed to improve stability, then positive electrode stability is improved, but lithium ion conductivity is reduced
Solution Approach 1:
The patent employs a composite inorganic coating material where phosphorus doping within the aluminum oxide matrix creates conductive pathways that facilitate lithium ion transport. The phosphorus dopants modify the crystal structure and electronic properties of Al2O3, enabling it to maintain high stability while preserving lithium ion conductivity.
Solution Approach 2:
The coating layer is designed with a controlled porous structure that allows lithium ions to penetrate and transport through the coating. The porosity is optimized to provide sufficient ion conduction channels while maintaining the protective function and structural stability of the coating layer.
4Quantity of substance
If high nickel content is used to increase capacity, then energy density is improved, but structural stability decreases and safety is reduced
Solution Approach 1:
The patent applies a protective coating layer before the high nickel positive electrode material undergoes degradation. This pre-applied coating acts as a barrier that prevents electrolyte decomposition and structural collapse during cycling, counteracting the inherent instability of high nickel materials before it manifests.
Solution Approach 2:
The high nickel cathode material is combined with a stable phosphorus-doped aluminum oxide coating, creating a composite structure where the unstable high-nickel core provides high capacity while the stable coated shell provides structural support and chemical stability, enabling the system to achieve both high energy density and safety.
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 enhances the lifetime and stability of lithium secondary batteries by maintaining high energy density and reducing resistance, thereby improving capacity retention and suppressing output reduction.
Implementation Method 1
A phosphorus-doped aluminum oxide coating layer with a thickness of 0.1 nm to 2.0 nm is applied using atomic layer deposition
Data Source
AI summary
A positive electrode active material, a method of preparing the same, and a positive electrode and a lithium secondary battery including the same are provided. The positive electrode active material includes a particulate positive electrode active material and a coating layer formed on a surface of the particulate positive electrode active material, the coating layer including a phosphorus (P)-doped aluminum oxide, and the coating layer having a thickness of 0.1 nm to 2.0 nm.