Silicon Core Anode with Lithium Titanium Oxide Shell

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Solution Overview

Problem

Silicon anode materials in lithium secondary batteries face significant lifespan deterioration due to reduced binding forces and continuous solid electrolyte interface formation caused by volumetric expansion and shrinkage, leading to irreversible reactions during charging and discharging.

Innovation Solution

A composite anode active material is developed, comprising a silicon core coated with a carbonaceous shell containing lithium titanium oxide, which suppresses irreversible reactions and maintains lithium ion conductivity, thereby enhancing electrochemical properties and battery lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is used as anode active material to achieve high specific capacity, then battery capacity is improved, but binding force between active materials is reduced and particles crack causing lifespan deterioration

Engineering Contradiction:

Improvespecific capacityVSAvoidlifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies composite materials by combining silicon core particles with a carbonaceous shell containing lithium titanium oxide. This composite structure allows the silicon to provide high specific capacity (3600 mAh/g) while the carbonaceous shell with lithium titanium oxide provides structural stability and prevents particle cracking, thus resolving the contradiction between high capacity and long lifespan.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The carbonaceous shell acts as a flexible protective layer that can accommodate the volumetric expansion and shrinkage of silicon particles during charging and discharging cycles. This shell prevents direct contact between silicon and electrolyte, reducing SEI layer formation and maintaining binding force, thereby extending battery lifespan while preserving high capacity.

Inventive Principle:

Principle #30Flexible shells and thin films

2Quantity of substance

If silicon particles undergo volumetric expansion and shrinkage during charging and discharging, then lithium ion capacity is improved, but SEI layer is continuously formed causing irreversible reactions

Engineering Contradiction:

Improvelithium ion capacityVSAvoidirreversible reactions

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The carbonaceous shell containing lithium titanium oxide serves as an intermediary layer between the silicon core and the electrolyte. This intermediary allows lithium ions to be stored and transported efficiently (maintaining high capacity) while preventing direct reactions between silicon and electrolyte that would form continuous SEI layers and cause irreversible energy loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If binding force between active materials is reduced during silicon charging and discharging, then lithium ion mobility is improved, but particle integrity is lost causing performance degradation

Engineering Contradiction:

Improvelithium ion mobilityVSAvoidbinding force

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The carbonaceous shell provides a flexible yet strong protective structure that maintains binding force between silicon particles and conductive agents during volumetric changes. This shell ensures particle integrity is preserved while still allowing efficient lithium ion mobility, preventing the performance degradation that would result from particle disintegration.

Inventive Principle:

Principle #30Flexible shells and thin films

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 composite anode active material significantly improves charge/discharge efficiency, maintains high capacity retention, and extends battery lifespan by preventing core material breakdown and SEI layer formation, even at high discharge rates.

Implementation Method 1

a solid electrolyte interface (SEI) layer is continuously formed due to repeated volumetric expansion and shrinkage of the silicon particles, causing drastic lifespan deterioration

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) layer formation:

Implementation Method 2

The lithium titanium oxide may be an inert material which does not intercalate or deintercalate lithium ions during charging and discharging of a lithium secondary battery

Methodology Applied

Scientific EffectLithium ion intercalation and deintercalation:

Implementation Method 3

when silicon is charged and discharged in a battery, the binding force between active materials may be reduced, and the silicon particles themselves may crack, and a solid electrolyte interface (SEI) layer is continuously formed due to repeated volumetric expansion and shrinkage of the silicon particles

Methodology Applied

Scientific EffectVolumetric expansion and shrinkage:

Data Source

PatentUS10658654B2Composite anode active material, anode including the same, and lithium secondary battery including the anode

Publication Date: 2020.05.19 SAMSUNG ELECTRONICS CO LTD

AI summary

A composite anode active material includes: a core comprising silicon; and a carbonaceous shell, wherein the carbonaceous shell includes a carbonaceous material and lithium titanium oxide.