Lithium-ion Battery Negative Electrode Remainder Positioning
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with local potential increases at the positive electrode's winding-direction end portions, leading to metal element elution and self-discharge, particularly due to oxygen reaction with negative electrode remainder portions during charging.
Innovation Solution
The battery design includes a wound electrode body with elongated positive and negative electrodes, where the negative electrode remainder portions are positioned within the nonaqueous electrolyte, preventing oxygen exposure and thus reducing lithium ion diffusion and metal element elution, along with a current interrupt device and gas generating agent for overcharge protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode remainder portion is exposed to oxygen during charging, then lithium ions diffuse to the positive electrode causing self-discharge, but if the battery structure is modified to prevent oxygen exposure, then manufacturing complexity increases
Solution Approach 1:
The patent positions the negative electrode remainder portion within the nonaqueous electrolyte environment, which acts as an inert atmosphere preventing oxygen exposure. The electrolyte surrounds the remainder portion, creating a protective environment that eliminates the harmful oxidation reaction while maintaining simple battery structure without requiring additional sealing components or complex modifications.
2Stability of the object's composition
If the negative electrode is made longer than the positive electrode to prevent lithium precipitation, then capacity utilization decreases, but if the electrode lengths are equalized, then lithium precipitation risk increases
Solution Approach 1:
The patent applies local quality by creating a specific configuration where the negative electrode remainder portion (the extended part beyond the positive electrode) is positioned within the nonaqueous electrolyte. This localized arrangement allows the remainder portion to serve a protective function against lithium precipitation while minimizing its impact on overall capacity utilization, as only the specific remainder portion benefits from the electrolyte environment rather than the entire electrode structure.
3Reliability
If the starting-end-side negative electrode remainder portion is positioned in the nonaqueous electrolyte, then metal element elution is suppressed, but then manufacturing precision requirements increase
Solution Approach 1:
The patent solves the positioning precision issue by transitioning from a two-dimensional planar arrangement to a three-dimensional spatial configuration. By positioning the negative electrode remainder portion vertically within the nonaqueous electrolyte fill space, the invention creates a buffer zone that accommodates manufacturing variations. The electrolyte environment provides a forgiving spatial dimension that allows the remainder portion to be effectively protected even with moderate positioning tolerances during assembly.
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 effectively suppresses metal element elution from the positive electrode active material, stabilizes the battery's potential, and reduces self-discharge, enhancing the battery's reliability and durability for high-energy-density applications.
Implementation Method 1
the elution of the metal element from the positive electrode active material is easily generated in a 'specific portion', namely in a winding-direction end portion of a wound electrode body... the starting-end-side negative electrode remainder portion is positioned in a region where the surplus nonaqueous electrolyte exists
Implementation Method 2
a gas may be generated due to decomposition of a nonaqueous electrolyte or the internal temperature of the battery may be increased due to heat generated from an active material... the gas generating agent is oxidized and decomposed on a surface of a positive electrode, at which time a hydrogen gas (H2) is generated from a negative electrode
Implementation Method 3
a self-discharge amount (a leak current) may grow larger... lithium ion diffusion and metal element elution
Data Source
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AI summary
A lithium-ion secondary battery (100) includes a wound electrode body (80), a nonaqueous electrolyte, and a box-shaped case (50). The wound electrode body includes a positive electrode (10), a negative electrode (20), and a separator (40). The box-shaped case contains the wound electrode body and the nonaqueous electrolyte. The wound electrode body includes a starting-end-side negative electrode remainder portion (22) provided in a winding-direction starting end portion (81) of the wound electrode body. The winding-direction starting end portion exists at a winding center side. The starting-end-side negative electrode remainder portion protrudes toward the winding center side along a winding direction beyond the positive electrode. A surplus nonaqueous electrolyte exists in a gap between the wound electrode body and the box-shaped case. The starting-end-side negative electrode remainder portion is positioned in a region where the surplus nonaqueous electrolyte exists, when the lithium-ion secondary battery is disposed in a predetermined posture.