Ni-Rich Cathode Surface Coating for Stable Lithium Exchange
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Solution Overview
Problem
Existing Ni-rich electrode active materials in lithium ion batteries face undesired reactions on the surface, leading to electrolyte decomposition and hindered lithium exchange during charging and discharging, despite previous attempts to coat these materials with oxides or wash away impurities like LiOH or Li2CO3.
Innovation Solution
A process involving treating Ni-rich electrode active materials with an aqueous medium, followed by partial water removal, then using a heteropoly acid or its salt, and finally a thermal treatment to create a uniform coating of tungsten or molybdenum oxides and phosphates or silicates on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Ni-rich electrode active materials are used to increase capacity, then energy density is improved, but surface reactions cause electrolyte decomposition and hinder lithium exchange
Solution Approach 1:
The patent applies composite materials by creating a dual-component surface coating on Ni-rich electrode active materials. The coating comprises both oxide components (from heteropoly acid decomposition) and phosphate/silicate components (from the aqueous formulation), forming a composite protective layer that maintains high Ni content (at least 50 mole-%) while providing enhanced surface stability and preventing electrolyte decomposition
Solution Approach 2:
The patent employs parameter changes by controlling the composition ratios of transition metals (Ni, Co, Mn) and the stoichiometry of the heteropoly acid (e.g., H3PW12O40, H4SiW12O40) to achieve optimal coating properties. The process parameters including treatment temperature, aqueous formulation concentration, and drying conditions are optimized to form a uniform coating that preserves the high energy density characteristics of Ni-rich materials
2Reliability
If electrode active materials are coated with oxides to protect surface, then surface stability is improved, but lithium exchange during charging and discharging is hindered
Solution Approach 1:
The patent applies local quality by creating a surface coating with specific spatial distribution and composition gradient. The heteropoly acid treatment creates a localized protective layer primarily on the particle surface, while the bulk material retains its original composition and lithium exchange capabilities. The coating thickness and composition are controlled to provide protection where needed while maintaining lithium ion conductivity at the interface
Solution Approach 2:
The patent uses the heteropoly acid decomposition products as an intermediary layer between the Ni-rich electrode material and the electrolyte. This intermediate coating acts as a buffer that prevents direct harmful interactions while allowing lithium ion transport, thus mediating between the need for surface protection and maintaining lithium exchange efficiency
3Quantity of substance
If free LiOH or Li2CO3 on surface are removed by washing, then surface purity is improved, but electrochemical properties do not improve
Solution Approach 1:
The patent extracts harmful surface impurities (free LiOH and Li2CO3) through treatment with aqueous formulations of heteropoly acids. The acid treatment selectively removes these basic impurities by converting them into soluble salts that can be washed away, thereby purifying the surface without damaging the underlying electrode active material structure
Solution Approach 2:
The patent performs preliminary surface treatment with heteropoly acid before final electrode fabrication and battery assembly. This preliminary action removes surface impurities and prepares the surface for optimal electrochemical performance, ensuring that subsequent battery cycling occurs on a clean, stable surface that maximizes lithium exchange efficiency
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 process results in electrode active materials with improved electrochemical properties, reducing lithium content and enhancing surface stability, thus improving battery performance.
Implementation Method 1
treating the solid residue with an aqueous formulation of at least one heteropoly acid or its respective ammonium or lithium salt
Implementation Method 2
treating the residue thermally
Data Source
AI summary
Process for making a partially coated electrode active material wherein said process comprises the following steps: (a) Providing an electrode active material according to general formula Li1+xTM1-xO2, wherein TM is Ni and, optionally, at least one of Co and Mn, and, optionally, at least one element selected from Al, Mg, and Ba, transition metals other than Ni, Co, and Mn, and x is in the range of from zero to 0.2, wherein at least 50 mole-% of the transition metal of TM is Ni, (b) treating said electrode active material with an aqueous medium, (c) partially removing water by solid-liquid separation method, (d) treating the solid residue with an aqueous formulation of at least one heteropolyacid or its respective ammonium or lithium salt, (e) treating the residue thermally.