Lithium Battery Separator with Li Absorber for High-Rate Durability

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Solution Overview

Problem

Lithium secondary batteries experience higher polarization at the positive electrode during charging and discharging, leading to reduced capacity and increased degradation due to the higher overvoltage, especially during high-rate charge/discharge cycles, resulting in a capacity difference between the positive and negative electrodes.

Innovation Solution

Incorporating an organic porous material layer between the positive and negative electrodes and an inorganic porous material layer with a Li absorber on the negative electrode side, which irreversibly stores lithium, adjusts the capacity balance and reduces polarization, thereby enhancing durability during high-rate charging and discharging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high-rate charging and discharging is performed, then power output is improved, but polarization increases causing capacity loss and degradation

Engineering Contradiction:

Improvepower outputVSAvoidbattery durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies preliminary anti-action by introducing a Li absorber that preemptively takes excess lithium from the negative electrode before it can cause harmful effects. The Li absorber is positioned to intercept lithium ions during high-rate charging, preventing the accumulation of excess lithium that would otherwise lead to polarization, capacity loss, and degradation during subsequent discharge cycles.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The Li absorber acts as an intermediary component between the negative electrode and the excess lithium ions. It mediates the lithium transport by selectively absorbing surplus lithium during charging and releasing it during discharge, thereby balancing the lithium flow and reducing the polarization effect that occurs at high charge/discharge rates.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a separator is used to prevent short circuits, then safety is improved, but thermal contraction at high temperature may cause new short-circuit spots

Engineering Contradiction:

Improveshort-circuit preventionVSAvoidthermal contraction damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs composite materials by combining the separator with a Li absorber layer to create a heat-resistant separator. This composite structure integrates the short-circuit prevention function of the separator with the thermal stability and lithium absorption capabilities of the Li absorber, allowing the component to simultaneously prevent short circuits and resist thermal contraction damage at elevated temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The heat-resistant separator serves multiple functions: it prevents short circuits between electrodes, maintains structural integrity at high temperatures by resisting thermal contraction, and absorbs excess lithium ions. This multi-functional design eliminates the need for separate components and addresses both the short-circuit prevention requirement and the thermal stability issue.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The solution effectively reduces the amount of lithium remaining in the negative electrode active material, maintaining capacity and suppressing resistance increase, thus improving the battery's durability and performance during high-rate charge/discharge cycles.

Implementation Method 1

an inorganic porous material layer with a Li absorber on the negative electrode side, which irreversibly stores lithium

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

the inorganic porous material layer adjusts the capacity balance and reduces polarization, thereby enhancing durability during high-rate charging and discharging

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 3

with the pores of the separator being impregnated with an electrolyte solution, it also serves to form ion-conducting paths (conduction channels) between the two electrodes

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 4

A separator formed from a porous resin sheet as described above undergoes thermal contraction when the temperature reaches a point where the shutdown function is activated

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS10115949B2Lithium secondary battery

Publication Date: 2018.10.30 TOYOTA JIDOSHA KK

AI summary

This invention provides a lithium secondary battery which degrades less upon high-rate charge/discharge cycles (thus durable). The lithium secondary battery comprises positive electrode 10 having positive electrode active material layer 14, negative electrode 20 having negative electrode active material layer 24, organic porous material layer 32 placed between positive electrode active material layer 14 and negative electrode active material layer 24, inorganic porous material layer 34 placed between organic porous material layer 32 and negative electrode active material layer 24. Inorganic porous material layer 34 comprises an inorganic filler that does not store lithium at a potential higher than the lithium-storing potential of the negative electrode active material layer, and a Li absorber that irreversibly stores lithium at a potential higher than the lithium-storing potential.