Insulating Layer on Lithium Nickel Positive Electrode
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in suppressing gas production at the positive electrode, particularly when using lithium nickel composite oxide as the active material, which leads to increased gas production due to oxidation of cyclic carbonic acid esters on the positive electrode surface.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a lithium nickel composite oxide with a layer structure, a non-aqueous electrolyte containing a high percentage of cyclic carbonic acid esters, and an insulating layer on the positive electrode surface, including insulating polymeric material and inorganic oxide particles, to reduce gas production by enhancing electrolyte retention and uniformity of the electrode reaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite oxide is used as positive electrode active material, then battery capacity is improved, but gas production at positive electrode increases
Solution Approach 1:
An insulating layer is introduced as an intermediary between the lithium nickel composite oxide positive electrode and the cyclic carbonic acid ester electrolyte. This insulating layer prevents direct contact and oxidation reactions, thereby suppressing gas production while allowing the high-capacity positive electrode material to function effectively.
Solution Approach 2:
The insulating layer, which might seem to hinder electrochemical reactions, actually converts a harmful effect (oxidation of electrolyte by strongly alkaline positive electrode) into a beneficial outcome (suppression of gas production). The layer protects the electrolyte from degradation while maintaining battery performance.
2Object-generated harmful factors
If insulating layer is formed on positive electrode, then gas production is suppressed, but electrolyte retention uniformity is improved
Solution Approach 1:
The insulating layer is designed with a porous structure that allows electrolyte penetration and retention while preventing direct contact between the electrolyte and the positive electrode active material. The porosity enables uniform electrolyte distribution throughout the layer, improving retention uniformity while maintaining gas suppression functionality.
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 effectively suppresses gas production at both the negative and positive electrodes, improving the reliability and capacity of the battery while maintaining safety through uniform electrode reactions and insulation, even under high temperatures.
Implementation Method 1
ethylene carbonate or propylene carbonate contained in the non-aqueous solvent is subject to oxidation on the positive electrode surface since the positive electrode active material is strongly alkaline
Implementation Method 2
The non-aqueous electrolyte is a liquid non-aqueous electrolyte including a lithium salt, such as LiBF4 or LiPF6, dissolved in an aprotic non-aqueous solvent
Implementation Method 3
The separator is, for example, a microporous film made of polyolefin
Implementation Method 4
The positive electrode active material is a lithium-containing transition metal oxide, since it has a high potential relative to lithium
Data Source
AI summary
A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and an insulating layer formed on a surface of the positive electrode. The positive electrode includes a lithium nickel composite oxide having a layer structure, and the lithium nickel composite oxide is represented by the general formula: LixNiyM1-yO2 where M is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Cu, Zn, Al, Cr, Pb, Sb, and B, 0<x≦1.2, and 0.5<y≦1.0. The non-aqueous electrolyte includes a solute and a non-aqueous solvent dissolving the solute, and the non-aqueous solvent contains 40% by weight or more of a cyclic carbonic acid ester. The insulating layer includes an insulating polymeric material.