Non-Aqueous Electrolyte Composition for Si-Anode Cycle Retention

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Solution Overview

Problem

Non-aqueous liquid electrolyte secondary batteries using negative-electrode active materials like Si, Sn, and Pb face challenges in maintaining high charge-discharge cycle performance and discharge capacity retention over time, due to issues such as dendrite growth and increased negative-electrode active material deterioration.

Innovation Solution

Incorporating a carbonate with an unsaturated bond or halogen atom, along with specific lithium salts and sulfur-containing compounds, into the non-aqueous liquid electrolyte to form a protective layer on the negative-electrode active material, enhancing cycle performance and capacity retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If negative-electrode active material containing Si, Sn, Pb is used to increase capacity, then charge capacity increases, but charge-discharge cycle performance deteriorates

Engineering Contradiction:

Improvecharge capacityVSAvoidcharge-discharge cycle performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A protective layer is introduced as an intermediary between the negative-electrode active material (Si, Sn, Pb) and the electrolyte. This protective layer, formed by specific additives (cyclic carbonate ester, phosphoric acid triester, and heterocyclic compounds with S and/or O atoms), prevents direct harmful interactions while allowing Li ion transport, thus maintaining high capacity while improving cycle performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte by specifically selecting and combining certain additives (cyclic carbonate ester, phosphoric acid triester, and heterocyclic compounds). This parameter change in electrolyte composition leads to the formation of a protective layer with optimal properties that resolves the contradiction between capacity and cycle performance.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If negative-electrode active material containing Si, Sn, Pb is used to increase capacity, then charge capacity increases, but discharge capacity retention rate decreases

Engineering Contradiction:

Improvecharge capacityVSAvoiddischarge capacity retention rate

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The protective layer acts as a mediator that stabilizes the interface between the high-capacity negative electrode material and the electrolyte. It prevents material deterioration and maintains discharge capacity retention by blocking harmful reactions while permitting necessary ion transport throughout the battery's operational life.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective layer is formed preliminarily during initial charging cycles through the decomposition of specific electrolyte additives. This preliminary formation of the protective layer prevents subsequent material deterioration and ensures long-term discharge capacity retention before the battery is put into regular use.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If metal lithium is used as negative electrode to achieve higher capacity, then charge capacity increases, but dendrite growth occurs leading to short circuit

Engineering Contradiction:

Improvecharge capacityVSAvoiddendrite growth

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The protective layer serves as an intermediary that prevents direct contact between metal lithium and the electrolyte. It provides a stable interface that suppresses dendrite formation by uniformizing Li ion flux distribution, thereby eliminating the harmful effect of dendrite growth while maintaining high capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 proposed solution significantly improves the battery's charge capacity and maintains excellent discharge capacity retention over a long period, addressing the limitations of previous battery technologies.

Implementation Method 1

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 2

carbonaceous material capable of intercalating and deintercalating lithium, such as coke, artificial graphite or natural graphite

Methodology Applied

Scientific EffectIntercalation:

Data Source

PatentUS12100809B2Non-aqueous liquid electrolyte and non-aqueous liquid electrolyte secondary battery

Publication Date: 2024.09.24 MITSUBISHI CHEM CORP

AI summary

A non-aqueous liquid electrolyte secondary battery using negative-electrode active material having Si, Sn and/or Pb, with high charge-capacity, superior characteristics including discharge-capacity retention rate over long is provided. Its non-aqueous liquid electrolyte contains carbonate having unsaturated bond and/or halogen and compounds like LiPF6 and/or LiBF4 (first lithium salt) and lithium salt different from said first one, represented by formula below (second lithium salt).Lil(αmXan)(In the formula, l, m and n represent integers of 1 to 10, 1 to 100 and 1 to 200, respectively.α represents boron, carbon, nitrogen, oxygen or phosphorus. Xa represents functional group having atom selected from 14th to 17th groups of periodic table at its binding-position to α. Two or more of Xa may be connected to each other to form a ring structure. However, such a case where α is boron and Xa is compound represented by(CiH2(i-2)O4)(CjH2(j-2)O4)is omitted (i and j represent integers of 2 or larger).