Li-M-O Cathode Coating for High-Nickel Surface Stability
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Solution Overview
Problem
Conventional lithium ion batteries face degradation issues due to cathode decomposition and electrolyte interactions, particularly with high-nickel content cathode materials, leading to phase transitions, ion consumption, and impedance increases, which are not effectively addressed by traditional binary metal oxide coatings.
Innovation Solution
A process involving a one-pot synthesis where a lithium metal oxide coating is formed on the cathode active material using a metal salt solution, leveraging excess lithium to create a thin, ionically conductive and electronically insulating Li—M—O coating, which prevents deleterious side reactions and stabilizes the cathode surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binary metal oxide coatings are used on cathode materials, then some protection is provided, but cathode decomposition and electrolyte interactions still occur leading to phase transitions, ion consumption, and impedance increases
Solution Approach 1:
The patent applies composite materials by creating a Li-M-O coating that combines lithium metal oxide with other metal oxides (such as Al, Ti, Fe, Ni, Cu, Zr, Nb, Mo, Sn, Y, Sb, or Sc). This composite coating structure provides superior protection compared to conventional binary metal oxide coatings, effectively preventing cathode decomposition and electrolyte interactions while maintaining cathode stability during battery cycling.
Solution Approach 2:
The patent employs parameter changes by controlling the oxidation state of metals in the Li-M-O coating and adjusting the coating composition ratios. The coating is formed through controlled oxidation of metal salts at specific temperatures (400-900°C), creating a coating with optimized ionic conductivity and electronic insulation properties that prevents harmful side reactions while maintaining performance.
2Object-affected harmful factors
If a coating is applied to protect the cathode, then cathode degradation is reduced, but the coating must maintain ionic diffusivity while being electronically insulating
Solution Approach 1:
The patent applies local quality by creating a coating with spatially varying properties: the Li-M-O coating is ionically conductive where lithium ions need to diffuse (maintaining high ionic conductivity at the interface with cathode material), while being electronically insulating at the outer surface (preventing electron leakage and side reactions). This localized property distribution allows the coating to simultaneously protect the cathode and maintain ionic diffusivity.
Solution Approach 2:
The patent uses parameter changes by controlling the oxidation state and composition of the Li-M-O coating to achieve optimal ionic conductivity. The coating is formed through controlled oxidation at 400-900°C, creating a structure with appropriate lithium content and metal oxidation states that enable high ionic diffusivity while maintaining electronic insulation, thus resolving the contradiction between protection and ion transport.
3Quantity of substance
If high-nickel content cathode materials are used to increase capacity, then energy density is improved, but phase transitions and impedance increases occur during cycling
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a Li-M-O coating on high-nickel cathode materials before battery assembly. This coating acts as a protective barrier that prevents phase transitions and suppresses impedance increases during cycling. The coating is formed through controlled oxidation of metal salts at 400-900°C, creating a stable surface layer that counteracts the inherent instability of high-nickel cathode materials during electrochemical cycling.
Solution Approach 2:
The patent uses composite materials by creating a Li-M-O coating on high-nickel cathode materials that combines the high capacity benefits of nickel-rich compositions with the stability of lithium metal oxide and other metals (Al, Ti, Fe, etc.). This composite structure maintains the high energy density of nickel-based cathodes while preventing phase transitions and impedance increases through the protective coating.
4Manufacturing precision
If a multi-step washing and coating process is used, then coating quality is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent applies merging by combining the washing and coating steps into a single integrated process. Instead of separately washing the cathode material and then applying a coating, the patent forms the Li-M-O coating in-situ through controlled oxidation of metal salts that are applied to the cathode surface. This single-step process maintains coating quality while significantly reducing manufacturing complexity and processing time compared to multi-step conventional methods.
Solution Approach 2:
The patent uses preliminary action by pre-applying metal salt solutions to the cathode surface before the oxidation step. The metal salts (such as Al(NO3)3, TiCl4, FeCl3, etc.) are dissolved in water or alcohol and applied to the cathode material, followed by controlled oxidation at 400-900°C to form the Li-M-O coating. This preliminary preparation simplifies the overall process compared to multi-step washing and coating methods while maintaining high coating quality.
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 Li—M—O coating effectively minimizes cathode degradation, maintains ionic diffusivity, and enhances the stability and performance of lithium ion batteries by scavenging harmful species and reducing impedance, thereby improving the battery's cycle life and rate capabilities.
Implementation Method 1
dissolving a metal salt in a solvent comprising water to generate an aqueous acidic solution
Implementation Method 2
annealing the acid treated electrode active material at a temperature sufficient to form a lithium metal oxide coating
Implementation Method 3
The coatings are ionically conductive while being electronically insulating
Data Source
AI summary
A process for coating a cathode active material includes dissolving a metal salt in water to generate an aqueous acidic solution; mixing the aqueous acidic solution with the cathode active material for an aging time period to form an acid treated cathode active material; and annealing the acid treated cathode active material at a temperature sufficient to form a lithium metal oxide coating on the cathode active material; wherein: the cathode active material is a high-nickel content lithium cathode active material; the metal salt is M(NO3)x, MClx, MIx, M(ClO3)x, or , M(ClO4)x; M is Al, Co, Cu, Fe, Mn, Mo, Nb, Ni, Sb, Sc, Sn, Ti, Y, Zr, or a mixture of any two or more thereof; and 1≤x≤8.