Wound Lithium Primary Battery Layout for Uniform Pulsed Discharge
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Solution Overview
Problem
Lithium primary batteries with large outer diameters and thick wound-electrode assemblies face challenges in maintaining uniform thickness balance, leading to uneven discharge reactions and voltage drops, especially during high pulsed discharge currents, due to expansion and contraction of electrodes and stress on separators.
Innovation Solution
A lithium primary battery design with a wound-electrode assembly featuring a positive electrode with a thickness of 0.8 mm to 1.4 mm, a negative electrode with a total area of 250 cm² to 700 cm², and an outer diameter of 25 mm to 37 mm, where the negative electrode's main surfaces face the positive electrode, and a distance between the electrode assembly and the outer can of 0.3 mm to 1.0 mm, optimizing the configuration to maintain stability and balance during discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the outer diameter of the battery is increased or the thickness of the wound-electrode assembly is increased to ensure high capacity, then the battery capacity is improved, but the uniformity of thickness balance at various parts of the wound-electrode assembly deteriorates, leading to uneven discharge reactions
Solution Approach 1:
The patent optimizes specific parameter ranges: outer diameter D (25-37 mm), positive electrode thickness Tp (0.8-1.4 mm), negative electrode total area S (250-700 cm²), and distance C between outer can and electrode assembly (0.3-1.0 mm). These parameter changes ensure high capacity while maintaining uniform thickness balance during discharge, preventing uneven discharge reactions that would occur with larger dimensions.
2Quantity of substance
If the thickness of the positive electrode is increased to provide greater capacity, then the battery capacity is improved, but the expansion of the positive electrode during discharge increases, making it difficult to maintain uniform thickness balance
Solution Approach 1:
The patent specifies an optimized thickness range for the positive electrode Tp (0.8-1.4 mm). This parameter change provides sufficient capacity while limiting expansion during discharge to levels that can be compensated by the separator, thereby maintaining uniform thickness balance and preventing uneven discharge reactions.
Solution Approach 2:
The separator acts as an intermediary that compensates for thickness changes in the positive electrode during discharge. By positioning the separator between the positive and negative electrodes, it absorbs and distributes the stress from electrode expansion, maintaining uniform thickness balance and ensuring even discharge reactions throughout the wound-electrode assembly.
3Quantity of substance
If the number of windings of the electrode assembly is increased to provide greater electrode area and capacity, then the battery capacity is improved, but the unevenness in discharge reactions increases
Solution Approach 1:
The patent optimizes the outer diameter D (25-37 mm) and negative electrode total area S (250-700 cm²), which indirectly control the number of windings. These parameter changes ensure sufficient electrode area for high capacity while maintaining a manageable number of windings that can be uniformly compressed and discharged, preventing uneven discharge reactions that would occur with excessive windings.
Solution Approach 2:
The optimized parameter ranges ensure that the electrode assembly achieves equipotential discharge characteristics throughout its structure. By controlling the outer diameter and electrode area within specific ranges, the patent ensures uniform current distribution and reaction rates across all windings, eliminating hot spots and uneven discharge that would reduce reliability.
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 ensures stable discharge performance across various depths of discharge, maintaining high capacity and discharge voltage, even during high pulsed currents, by compensating for electrode expansion and contraction, thereby reducing stress and ensuring uniform reaction within the battery.
Implementation Method 1
during discharge, the positive electrode expands, increasing its thickness. On the other hand, the lithium in the negative electrode undergoes dissolution, reducing its thickness.
Data Source
AI summary
A lithium primary battery includes an outer can, a wound-electrode assembly, and a non-aqueous electrolyte. The wound-electrode assembly includes a positive electrode, a negative electrode, and a separator which are provided between the electrodes and are wound together. The positive electrode contains manganese dioxide. The negative electrode contains at least one substance selected from the group consisting of metallic lithium and metallic lithium containing a lithium alloy, and has a first main surface and a second main surface opposite to the first main surface. The first main surface and an entirety of the second main surface of the negative electrode face the positive electrode. The total area S of the first main surface and the second main surface of the negative electrode satisfies 250 cm2≤S≤700 cm2. The thickness Tp of the positive electrode satisfies 0.8 mm≤Tp≤1.4 mm. The outer diameter D of the outer can satisfies 25 mm≤D≤37 mm. The distance C between the outer can and the wound-electrode assembly satisfies 0.3 mm≤C≤1.0 mm.