Positive Electrode Coating with Tungsten Oxide and Phosphate
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face a decrease in initial charge capacity when their positive electrode active material or electrode is exposed to air, due to reactions leading to LiOH production and degradation.
Innovation Solution
A positive electrode comprising a lithium transition metal composite oxide, tungsten oxide, and a phosphate compound, where the tungsten oxide suppresses LiOH production and the phosphate compound interacts with Mn4+ to reduce moisture adsorption, maintaining charge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the positive electrode active material is exposed to air for ease of manufacture, then the manufacturing process is simplified, but the initial charge capacity decreases due to LiOH production and degradation
Solution Approach 1:
A coating layer comprising tungsten oxide and a phosphate compound is applied to the surface of the positive electrode active material particles. This coating layer acts as an intermediary barrier that prevents direct contact between the active material and moisture in the air, thereby suppressing LiOH production and capacity degradation while allowing the electrode to be handled in air during manufacturing
Solution Approach 2:
The patent uses a composite coating material consisting of tungsten oxide and a phosphate compound (such as lithium phosphate, cobalt phosphate, or nickel phosphate). This composite material combines the moisture-suppressing properties of tungsten oxide with the protective characteristics of the phosphate compound, providing effective protection against air exposure while maintaining ease of manufacture
2Ease of operation
If the positive electrode active material is exposed to air to simplify handling, then the handling process is simplified, but the initial charge characteristics degrade due to moisture adsorption and LiOH production
Solution Approach 1:
The coating layer of tungsten oxide and phosphate compound serves as a protective intermediary that allows the positive electrode active material to be handled in air without direct harmful interactions. The coating prevents moisture adsorption and LiOH production on the active material surface, enabling simplified handling operations while maintaining charge characteristics
Solution Approach 2:
The coating layer creates an inert protective environment around the positive electrode active material particles, shielding them from reactive moisture in the air. This allows the electrode to be handled in ambient air conditions without requiring specialized inert atmosphere equipment, thus simplifying operations while protecting against degradation
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 combination of tungsten oxide and phosphate compound significantly suppresses the degradation of initial charge characteristics when the electrode is exposed to air, maintaining battery performance.
Implementation Method 1
tungsten oxide that adheres to the surface of the lithium transition metal composite oxide... the tungsten oxide suppresses LiOH production
Implementation Method 2
a phosphate compound that adheres to the surface of the lithium transition metal composite oxide... the phosphate compound interacts with Mn4+ to reduce moisture adsorption
Data Source
AI summary
There is provided a positive electrode for nonaqueous electrolyte secondary batteries in which a decrease in the initial charge capacity can be suppressed even when a positive electrode exposed to the air is used. A positive electrode for a nonaqueous electrolyte secondary battery according to an aspect of the present invention contains a lithium transition metal composite oxide represented by general formula Li1+xMnaMbO2+c (in the formula, x, a, b, and c satisfy x+a+b=1, 0<x≤0.2, 0.09≤a, and −0.1≤c≤0.1, and M is at least one element selected from the group consisting of transition metal elements other than Mn, alkali metal elements, alkaline-earth metal elements, group 12 elements, group 13 elements, and group 14 elements) and also contains tungsten oxide and a phosphate compound.