Lithium Cathode Additives for Silicon Anode Capacity Retention

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Solution Overview

Problem

Lithium ion batteries face challenges with low energy density, rapid capacity fading, and electrode degradation due to volume changes and side reactions, which limit their performance in high-energy demanding applications.

Innovation Solution

Incorporating a lithiation agent with a lithium constituent into the cathode active material to provide a sacrificial source of lithium, which reacts with the anode active material and forms a stable solid-electrolyte interphase layer, reducing irreversible lithium consumption and preserving capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is used as anode material to increase capacity, then the theoretical capacity increases significantly, but large volume variations induce electrode fracturing and capacity degradation

Engineering Contradiction:

Improvelithium capacityVSAvoidcycle life

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies this principle by using graphene sheets as flexible thin films that conform to the silicon anode material. The graphene forms a continuous network that accommodates the large volume expansion of silicon during lithiation while maintaining structural integrity and electrical contact, preventing electrode fracturing and capacity degradation.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent creates a composite material system combining silicon anode particles with a graphene continuous network. This composite structure allows the silicon to provide high capacity while the graphene matrix provides mechanical flexibility and electrical conductivity, resolving the contradiction between high capacity and cycle stability.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If more lithium is provided in the cathode to match high-capacity anode, then energy density increases, but side reactions consume lithium irreversibly causing capacity fading

Engineering Contradiction:

Improvelithium contentVSAvoidcapacity fading

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by pre-forming a stable solid electrolyte interphase (SEI) layer during initial cycles using a portion of the lithium from the cathode. This preliminary SEI formation consumes lithium irreversibly but prevents further side reactions during subsequent cycling, thereby preserving the majority of lithium for reversible capacity and preventing capacity fading.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful irreversible lithium consumption during SEI formation into a beneficial protective layer. The initial lithium loss creates a stable SEI that prevents ongoing side reactions and electrolyte decomposition, ultimately preserving capacity and converting the initial harm into long-term benefit.

Inventive Principle:

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

3Reliability

If graphite anode is used for stability, then cycle life is maintained, but theoretical capacity is limited to 372 mAh/g

Engineering Contradiction:

Improvecycle stabilityVSAvoidtheoretical capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent changes the fundamental parameter of the anode material from graphite (intercalation mechanism, 372 mAh/g capacity) to silicon (alloying mechanism, up to 4200 mAh/g capacity). This parameter change enables high capacity while the graphene network and SEI layer provide the stability that graphite would have otherwise provided.

Inventive Principle:

Principle #35Parameter changes

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 approach enhances the reversible capacity of lithium-ion batteries by minimizing capacity loss and extending cycle life, while maintaining high energy storage efficiency.

Implementation Method 1

reacts with the anode active material and forms a stable solid-electrolyte interphase layer, reducing irreversible lithium consumption and preserving capacity

Methodology Applied

Scientific EffectSolid-electrolyte interphase formation:

Implementation Method 2

Lithium ions are intercalated and deintercalated between the anode and the cathode through the electrolyte during discharge and charge

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 3

lithium metal can electrochemically alloy with other metals at room temperature, lithium alloying reactions with metallic or semi-metallic elements and various compounds have been investigated

Methodology Applied

Scientific EffectAlloying reaction:

Data Source

PatentUS11069919B2Cathode additives to provide an excess lithium source for lithium ion batteries

Publication Date: 2021.07.20 M2INNOVATIONS LLC

AI summary

A lithium ion electrochemical cell is described in which the lithium comprising further comprises a lithiation agent. The lithiation agent, which comprises a lithium constituent, is designed to provide an excess source of lithium to minimize capacity loss of the lithium ion electrochemical cell. The anode of the lithium ion cell comprises a material matrix comprising carbon, graphene and an active element such as silicon or tin.