Lithium-Sulfur Battery with Solid LiNO3 Holder for Cycle Efficiency
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Solution Overview
Problem
Lithium-sulfur batteries face a significant challenge in maintaining high coulombic efficiency over long cycles due to the dissolution of lithium polysulfides in the electrolyte, leading to reduced discharge capacity and increased charge capacity, which results in a rapid decrease in performance.
Innovation Solution
Incorporating a lithium nitrate holder in a solid state within the battery, which continuously supplies lithium nitrate, preventing the decrease in coulombic efficiency and maintaining high efficiency for an extended number of cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium polysulfide is used as a positive electrode active material in a lithium-sulfur battery, then high theoretical energy density (2,600 Wh/kg) and capacity (1,675 mAh/g) are achieved, but lithium polysulfide dissolves in the electrolyte solution causing rapid decrease in coulombic efficiency over long cycles
Solution Approach 1:
Lithium nitrate is pre-added to the electrolyte solution to proactively prevent the dissolution of lithium polysulfide before it occurs. The lithium nitrate forms a protective film on the positive electrode surface in advance, blocking the dissolution pathway and maintaining high coulombic efficiency throughout long cycling operations.
Solution Approach 2:
Lithium nitrate acts as an intermediary substance between the lithium polysulfide and the electrolyte solution. It mediates the interaction by forming a protective interface layer that prevents direct contact between the polysulfide and electrolyte, thereby eliminating the harmful dissolution effect while preserving the electrochemical functionality.
2Reliability
If lithium polysulfide elutes from the positive electrode into the electrolyte solution, then the electrochemical reaction area is reduced, but adding lithium nitrate to the electrolyte solution consumes the additive over time causing rapid decrease in coulombic efficiency
Solution Approach 1:
The lithium nitrate in the electrolyte solution serves itself by continuously forming protective films on the positive electrode surface during cycling. This self-service mechanism allows the lithium nitrate to prevent polysulfide dissolution without being consumed, maintaining stable coulombic efficiency over long cycles without rapid 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 lithium nitrate holder ensures high coulombic efficiency is maintained for a long cycle, with a minimum of 200 cycles at 98% or more, significantly improving the battery's lifespan and performance.
Implementation Method 1
lithium nitrate, which has an effect of preventing dissolution of lithium polysulfide
Implementation Method 2
a carbon-based material having intercalation/deintercalation of metal ions such as lithium ions as a negative electrode active material
Implementation Method 3
electric energy is stored and produced using an oxidation-reduction reaction in which an oxidation number of sulfur decreases as sulfur-sulfur bonds are broken during a reduction reaction (discharge), and an oxidation number of sulfur increases as sulfur-sulfur bonds are formed again during an oxidation reaction (charge)
Data Source
AI summary
A lithium secondary battery includes a cell stack having one or more unit cells. Each of the one or more unit cells includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode. The lithium secondary battery includes a lithium nitrate holder in a solid state, an electrolyte solution, and a battery case. The cell stack, the lithium nitrate holder in the solid state, and the electrolyte solution are in the battery case.