Lithium Battery with Concentration Gradient Electrode
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Solution Overview
Problem
Lithium secondary batteries face limitations in lifetime characteristics and high-voltage charging due to increased lithium ion amounts and electrolyte decomposition, especially with conventional lithium transition metal oxides.
Innovation Solution
A lithium secondary battery design featuring a positive electrode with a lithium-metal oxide having a continuous concentration gradient of metals from the center to the surface, combined with a non-aqueous electrolyte containing a multinitrile compound, which enhances storage and lifetime characteristics at high temperatures and voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the battery is charged at high voltage to increase capacity, then the battery capacity is improved, but the lifetime of the battery is decreased due to electrolyte decomposition and positive electrode instability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the lithium transition metal oxide particles. The center region has a different metal composition than the surface region, with the surface having lower nickel content and higher content of stabilizing elements like cobalt and manganese. This local compositional variation allows the battery to achieve high capacity while maintaining structural stability and preventing electrolyte decomposition at high voltages, thus resolving the contradiction between capacity and lifetime.
Solution Approach 2:
The patent changes the compositional parameters of the lithium transition metal oxide by introducing a continuous concentration gradient of metal elements from center to surface. Specifically, the nickel content decreases from the center to the surface, while cobalt and manganese content increase from center to surface. This parameter change optimizes the material to withstand high voltage charging (4.3-4.5V) while maintaining high capacity, thereby improving both battery capacity and lifetime simultaneously.
2Quantity of substance
If the amount of lithium ions is increased to improve capacity, then the battery capacity is improved, but the instability of the positive active material structure is greatly increased
Solution Approach 1:
The patent uses local quality by creating regions with different metal compositions within the lithium transition metal oxide particles. The surface region has lower nickel content and higher content of structurally stabilizing elements (cobalt and manganese), which prevents structural instability when large amounts of lithium ions are present. This local compositional optimization allows high lithium ion content while maintaining structural stability.
Solution Approach 2:
The patent creates a composite structure within the lithium transition metal oxide particles by combining multiple metal elements (nickel, cobalt, manganese) in a specific spatial distribution. The continuous concentration gradient creates a composite material where different regions have different properties - the center provides high capacity while the surface provides structural stability, allowing high lithium ion content without structural degradation.
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and more particularly, the positive electrode includes a positive active material including lithium-metal oxide in which at least one metal has the continuous concentration gradient from the center to the surface, and the non-aqueous electrolyte includes a lithium salt, a multinitrile compound, and an organic solvent, thereby improving storage characteristics at a high voltage and lifetime characteristics.