Lithium Accumulator Cell with Aluminum Protective Layer
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Solution Overview
Problem
Lithium-metal accumulators face issues with lithium foam and dendrite formation, leading to irreversible degradation and limited cycle life due to the reactivity of metallic lithium with liquid electrolytes, which is exacerbated by the formation of lithium dendrites that can cause short circuits and temperature rises.
Innovation Solution
An electrochemical cell design featuring a negative electrode with a metallic lithium layer coated with a compound containing aluminum, paired with an aluminum current collector and an electrolyte containing lithium salts such as lithium imide, lithium triflate, or lithium perchlorate, which reduces foam and dendrite formation by providing a protective layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metallic lithium is used as the negative electrode to achieve high energy density, then the energy density per unit mass is improved, but lithium dendrites form causing short circuits and irreversible degradation
Solution Approach 1:
An aluminum-based protective layer is introduced as an intermediary between the metallic lithium negative electrode and the liquid electrolyte. This layer acts as a mediator that prevents direct contact and harmful reactions between lithium and the electrolyte, thereby eliminating dendrite formation while preserving the high energy density benefits of metallic lithium.
Solution Approach 2:
The invention changes the chemical composition and physical properties of the interface between the lithium electrode and electrolyte by applying an aluminum-based coating. This parameter change in the electrode surface composition prevents the formation of lithium foam and dendrites, resolving the reliability issue while maintaining energy density.
2Reliability
If a polymer electrolyte is used to prevent dendrite formation, then the reliability is improved, but the operating temperature must be raised above 50°C due to insufficient conductivity
Solution Approach 1:
The invention changes the physical state of the electrolyte interface by applying an aluminum-based protective layer, allowing the system to operate with liquid electrolyte at ambient temperatures. This parameter change in the electrode surface enables low-temperature operation while maintaining dendrite prevention, unlike bulk polymer electrolytes which require heating.
Solution Approach 2:
The negative electrode is constructed as a composite structure with metallic lithium combined with an aluminum-based protective layer. This composite material provides both the high energy density of lithium and the protective properties needed to prevent dendrites, eliminating the need for high-temperature polymer electrolytes.
3Quantity of substance
If metallic lithium reacts with liquid electrolyte to form lithium foam, then the reactivity is utilized, but active material is lost reducing accumulator life
Solution Approach 1:
The aluminum-based protective layer serves as an intermediary barrier that controls the interaction between metallic lithium and the liquid electrolyte. It allows beneficial reactivity while preventing excessive reaction that would form lithium foam and cause active material loss, thereby extending accumulator life.
Solution Approach 2:
A thin aluminum-based protective film is applied to the lithium electrode surface. This thin film acts as a selective barrier that prevents direct harmful reactions between lithium and electrolyte, reducing lithium foam formation and active material loss while maintaining the necessary electrochemical 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
This configuration enhances cyclability by preventing lithium foam and dendrite formation, thereby extending the life of lithium accumulators while maintaining high energy density and reducing operating temperatures.
Implementation Method 1
the negative electrode is provided at its face in contact with the electrolyte with a layer comprising a compound containing aluminium
Implementation Method 2
the production of ions that will circulate from one electrode to the other through an electrolyte
Implementation Method 3
a positive electrode on aluminium collector
Data Source
AI summary
An electrochemical cell for a lithium accumulator comprising: a negative electrode comprising metallic lithium as active material; a positive electrode associated with an aluminium current collector; and an electrolyte placed between the negative electrode and the positive electrode, wherein the negative electrode is provided with a layer comprising a compound containing aluminium at its face in contact with the electrolyte, and in that the electrolyte comprises at least one lithium salt chosen from among lithium imide, lithium triflate, lithium perchlorate salts and mixtures thereof.