Electrode Assembly Layout to Prevent Ni-Band in Rechargeable Batteries
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Solution Overview
Problem
The Ni-band phenomenon occurs in rechargeable batteries due to the lack of electrolyte moistening at the outermost part of the second separator, leading to excess electrolyte generation, Ni elution, and voltage imbalance, which can cause safety issues like sudden drops in cell lifespan and ignition.
Innovation Solution
The second electrode is designed with an uncoated portion at the outermost turn covered by the second separator, featuring an exposed portion that contacts the case to reduce internal resistance and an end portion that provides electrolyte moistening, preventing excess electrolyte generation and Ni elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second separator fully covers the second electrode at the outermost turn, then electrolyte distribution is improved, but the electrode structure becomes more complex and manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating different coverage states of the second separator at different locations of the second electrode. Specifically, the second separator covers the second electrode at most turns but intentionally leaves an uncoated portion exposed at the outermost turn. This localized differentiation in coverage quality resolves the contradiction by ensuring adequate electrolyte distribution where needed while simplifying the overall structure and manufacturing requirements.
2Reliability
If the uncoated portion is fully covered by the second separator, then electrolyte moistening is improved, but internal resistance increases and voltage imbalance occurs
Solution Approach 1:
The patent creates local quality differentiation in electrolyte access by having the second separator cover the second electrode in most areas while intentionally leaving the uncoated portion at the outermost turn exposed. This allows different regions to have different electrolyte moistening characteristics, preventing excessive electrolyte accumulation that would increase internal resistance and cause voltage imbalance, while still maintaining adequate moistening where the separator provides coverage.
3Reliability
If the second separator covers the entire second electrode, then safety is improved by preventing electrolyte leakage, but the Ni-band phenomenon occurs due to excess electrolyte generation
Solution Approach 1:
The patent resolves this contradiction by applying local quality differentiation - the second separator covers the second electrode in most regions to prevent electrolyte leakage and ensure safety, but intentionally leaves the uncoated portion at the outermost turn exposed. This localized exposure prevents excessive electrolyte generation that causes the Ni-band phenomenon while maintaining adequate coverage and safety in the rest of the structure.
Solution Approach 2:
The patent extracts or removes the second separator coverage from the specific uncoated portion at the outermost turn of the second electrode. This extraction of the covering function from that specific location prevents the harmful effect of excess electrolyte generation and Ni-band phenomenon, while the separator remains in place for the majority of the electrode structure to maintain safety and prevent leakage.
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 stabilizes the open circuit voltage and prevents the Ni-band phenomenon, ensuring stable battery performance and safety by reducing internal resistance and eliminating excess electrolyte issues.
Implementation Method 1
the exposed portion and the second separator may be in contact with an inner surface of the case
Implementation Method 2
the Ni-band phenomenon occurs in rechargeable batteries due to the lack of electrolyte moistening at the outermost part of the second separator
Data Source
AI summary
An electrode assembly, the electrode assembly including a first electrode, a first separator, a second electrode, and a second separator wound in a stacked state, wherein, the second electrode comprises an uncoated portion formed at an outermost turn, the second separator covers a part of the uncoated portion, and the uncoated portion comprises a covering portion covered with the second separator, and an exposed portion connected to the covering portion and exposed from the second separator.