Primary Lithium Spiral Cell Layout for High-Temperature Yield
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Solution Overview
Problem
Lithium primary cells with spirally-wound constructions face limitations in high-temperature applications due to increased self-discharge of the anode, leading to reduced negative electrode capacity and inefficient use of lithium, necessitating a higher lithium content to maintain performance.
Innovation Solution
The electrochemical cell design features a spiral electrode plate group with a positive electrode and a lithium or lithium-based alloy strip covering an inner face of the container, optimizing the positive electrode's performance by distributing lithium in two contributions: one at the spiral negative electrode and another at the strip, thereby increasing the discharge yield and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a greater quantity of lithium is used to compensate for self-discharge at high temperatures, then the anode capacity increases, but the positive electrode becomes the limiting electrode and its operating performance deteriorates
Solution Approach 1:
The negative electrode is segmented into two distinct components: a spiral-wound negative electrode integrated with the positive electrode in the spiral assembly, and a separate lithium strip positioned against the inner face of the container. This segmentation allows each component to serve a specific function - the spiral negative electrode maintains structural integrity while the separate lithium strip provides additional capacity without compromising positive electrode performance.
Solution Approach 2:
The separator acts as an intermediary between the spiral electrode assembly and the lithium strip, enabling ionic conduction while maintaining physical separation. This allows the lithium strip to contribute to the overall cell capacity without directly interfering with the spiral wound structure or the positive electrode's operating characteristics.
2Reliability
If more lithium is added to maintain performance at high temperatures, then the cell capacity is maintained, but the amount of active materials increases leading to higher production costs
Solution Approach 1:
The lithium strip is positioned locally against the inner face of the container, creating a localized region of additional lithium capacity. This local quality enhancement allows the cell to maintain performance at high temperatures without uniformly increasing the amount of active materials throughout the entire cell structure.
3Productivity
If the ratio of negative electrode capacity to positive electrode capacity is greater than 1, then the positive electrode is optimized for high-temperature operation, but the device complexity increases
Solution Approach 1:
The separator is merged with the lithium strip, creating an integrated component that combines the functions of separation and additional lithium capacity. This merging reduces the number of discrete components and simplifies the overall device structure while maintaining the capability to achieve optimized positive electrode performance at high temperatures.
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 design enhances the electrochemical capacity and discharge yield of the cell, allowing for identical performance to standard spirally-wound cells while using less active materials, thus reducing production costs and improving high-temperature application efficiency.
Implementation Method 1
During the discharge of such a cell, the oxidation of the lithium metal to lithium ions occurs at the anode
Implementation Method 2
At the positive electrode, reduction of the oxidizing compound occurs in the pores of the carbon mass
Implementation Method 3
The salt used may be chosen from lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, or lithium hexafluorophosphate LiPF6
Data Source
AI summary
An electrochemical cell including a container including an electrochemical spiral bundle including: a positive electrode including an active material selected from among SOCl2, SO2, SO2Cl; CFx where x≤1.5; MnO2, FeS2, V2O5, I2, Bi2O3, Bi2Pb2O5, CuCl2, CuF2, CuO, Cu4O(PO4)2, CuS, FeS, MoO3, Ni3S2, AgCl, Ag2CrO4, SVO, MO6S8, and a mixture of a plurality thereof; a separator; and a negative electrode including an active material made of lithium metal or of a lithium-based alloy. The outer face of the spiral, facing the container, is formed by the positive electrode, and a strip of lithium or of a lithium-based alloy at least partially covers the inner face of the container. The strip pressed against the inner face of the container makes it possible to make use of an outer face of the positive electrode which forms the last turn of the spirally-wound electrode plate group.