Oil-Immersed Battery Pack Venting for Thermal Runaway Safety

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Solution Overview

Problem

Existing battery packs face challenges in efficiently managing heat generation during high-rate charging, leading to thermal runaway and safety risks such as flame ejection and electrical short circuits, particularly in cylindrical cells.

Innovation Solution

A battery pack design incorporating a housing with a receiving cavity filled with insulating cooling oil, a pressure relief space, and a bus bar configuration that utilizes heat convection for efficient cooling, along with a fixing layer to stabilize the cell set, and explosion-proof valves to manage thermal runaway.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If indirect liquid cooling technology (liquid cooling plate) is used, then heating problem in low rate charging mode can be alleviated, but cooling efficiency is obviously insufficient in high rate charging mode

Engineering Contradiction:

Improvecooling efficiencyVSAvoidheat dissipation capability

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent uses direct liquid cooling by injecting cooling liquid directly into the battery pack cavity surrounding the cells, replacing the indirect cooling plate method. This hydraulic approach allows the cooling liquid to flow directly around the heat-generating components, significantly improving heat transfer efficiency and cooling performance during high-rate charging operations.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The patent introduces cooling liquid as an intermediary substance that directly contacts both the battery cells and the heat dissipation system. This intermediary enables efficient thermal energy transfer from the cells through the liquid medium, solving the insufficient cooling efficiency problem of indirect cooling methods.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If thermal runaway occurs in a cell, then flame may be ejected from explosion-proof valve, but this leads to safety risk to occupant and may melt bus bar

Engineering Contradiction:

Improvesafety performanceVSAvoidflame ejection and electrical short circuit risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of thermal runaway flames into a beneficial outcome by using the cooling liquid to extinguish flames. When thermal runaway occurs and flame is ejected from the explosion-proof valve, the cooling liquid surrounding the cells immediately suppresses the flame, preventing it from reaching the bus bar and causing electrical short circuits or damage to occupants.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent prepares the cooling liquid in advance within the battery pack cavity, positioned to immediately respond to thermal runaway events. This pre-positioned cooling liquid acts as a protective cushion that can quickly suppress flames and prevent catastrophic failures before they propagate, enhancing safety without requiring additional active safety systems.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Use of energy by moving object

If energy density of power battery is increased using high-nickel positive electrode and silicon-carbon negative electrode, then endurance mileage and charge ratio improve, but heat generation during operation increases rapidly

Engineering Contradiction:

Improveendurance mileage and charge ratioVSAvoidheat generation

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent employs direct liquid cooling where cooling liquid flows directly around the high-energy-density cells, providing intensive heat removal capability. This hydraulic cooling system can handle the rapid heat generation from high-nickel and silicon-carbon cells during high-rate charging, maintaining thermal management effectiveness despite the increased energy density and heat output.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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

Enhances safety by extinguishing flames and preventing electrical short circuits, while maintaining structural stability and improving heat dissipation, thus reducing risks associated with thermal runaway.

Implementation Method 1

The battery pack utilizes heat convection of the liquid to achieve the efficient cooling of the cell set by injecting insulating cooling oil into the receiving cavity

Methodology Applied

Scientific EffectHeat convection: Convection

Implementation Method 2

the insulating cooling oil in the pressure relief space is capable of extinguishing a flame ejected from an explosion-proof valve directly

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Data Source

PatentUS20250309406A1Battery pack

Publication Date: 2025.10.02 EVE ENERGY CO LTD

AI summary

A battery pack is disclosed according to the present disclosure. The battery pack includes: a housing, a cover, a cell set and a bus bar. The housing includes a receiving cavity with an opening on a side of the housing. The cover is provided over the side of the housing with the opening to close the receiving cavity. The cell set is provided in the receiving cavity, and electrodes of the cell set face the cover. The bus bar is provided between the cell set and the cover, and a pressure relief space is reserved between the bus bar and the cover. The receiving cavity is filled with insulating cooling oil, and the electrodes of the cell set and the bus bar are submerged in the insulating cooling oil.