Bipolar Lithium-Sulfur Battery Architecture
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Solution Overview
Problem
Lithium-ion batteries face issues with power behavior due to the use of graphite as a negative electrode, leading to reduced energy density when replaced with lithiated titanium oxide, and there is a risk of metallic lithium dendrite formation, which can cause degradation and safety concerns.
Innovation Solution
A lithium electrochemical battery with a bipolar architecture using elemental sulfur as the negative electrode and a lithiated compound like LiFePO4 as the positive electrode, avoiding metallic lithium formation and maintaining high mass capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If graphite is used as the negative electrode, then the battery exhibits good power behavior, but the energy density is reduced when replaced with lithiated titanium oxide
Solution Approach 1:
The patent merges multiple electrochemical cells into a single bipolar architecture where the negative electrode of one cell is directly connected to the positive electrode of the adjacent cell through a current collector. This integration eliminates the need for separate graphite electrodes while maintaining good power behavior through direct electron transfer paths, and achieves high energy density by using lithiated titanium oxide without requiring additional graphite layers.
Solution Approach 2:
Instead of using graphite as the negative electrode material (conventional approach), the patent inverts the approach by using lithiated titanium oxide as the negative electrode in a bipolar configuration. This inversion allows the material to function effectively as a negative electrode while maintaining both good power behavior and high energy density, resolving the traditional trade-off between these two parameters.
2Use of energy by moving object
If lithium metal is used at the negative electrode, then high nominal cell voltage and excellent mass and volume energy densities are obtained, but there is a risk of lithium dendrites forming which can cause short-circuit phenomena
Solution Approach 1:
The patent replaces the problematic lithium metal (which forms dangerous dendrites) with lithiated titanium oxide as the negative electrode material. While lithiated titanium oxide has lower theoretical capacity than lithium metal, the bipolar architecture compensates for this by stacking multiple cells, achieving high overall energy density without the safety risks of dendrite formation.
Solution Approach 2:
The patent introduces an intermediary material (lithiated titanium oxide) between the electrolyte and the electrode reaction site, preventing direct lithium metal deposition that causes dendrites. This intermediary layer allows lithium ion insertion/extraction in a controlled manner, maintaining high energy density while eliminating the harmful dendrite formation mechanism.
3Power
If lithiated titanium oxide is used to replace graphite, then power behavior improves, but the nominal cell voltage is reduced from 3.6V to 2.5V
Solution Approach 1:
The patent segments the battery into multiple electrochemical cells connected in series within a bipolar architecture. By stacking several cells, the overall nominal voltage of the battery pack increases despite each individual cell operating at 2.5V. This segmentation allows the use of lithiated titanium oxide for improved power behavior while achieving the required voltage through series connection of multiple lower-voltage cells.
Solution Approach 2:
The patent transitions from optimizing single-cell voltage to optimizing multi-cell stack voltage. Instead of focusing on increasing the voltage of a single cell (which would require sacrificing power behavior), the solution moves to another dimension by stacking multiple 2.5V cells in series to achieve the desired overall voltage, thereby preserving both power behavior and voltage requirements.
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 battery achieves high mass capacity and safety without dendrite formation, with adaptable voltage and compactness for portable applications, suitable for energy-intensive fields like electric vehicles and microelectronics.
Implementation Method 1
the electrodes comprising specific materials capable of reacting according to an oxidation-reduction reaction, whereby there is production of electrons at the origin of the electric current and production of ions which will circulate from one electrode to the other through an electrolyte
Implementation Method 2
the transfer, via an ion-conducting electrolyte lithium, lithium cations originating from a negative electrode which are intercalated in the acceptor network of the positive electrode
Implementation Method 3
electrons resulting from the reaction at the negative electrode will supply the external circuit to which the positive electrodes are connected and negative
Data Source
AI summary
The invention relates to a lithium electrochemical accumulator comprising at least a first electrochemical cell and at least a second electrochemical cell separated from one another by a current collecting substrate. A first face of the aforementioned substrate supports an electrode of the first electrochemical cell and a second face, opposite the first, supports an electrode, of opposite sign, of the second electrochemical cell. Each cell comprises a positive electrode and a negative electrode separated by an electrolyte. The invention is characterised in that the positive electrode comprises a lithium compound and the negative electrode comprises elementary sulphur.