Polymer Electrolyte-Protected Anode Particulates for Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face challenges with high-capacity anode active materials that suffer from severe pulverization during charge and discharge cycles, leading to shortened cycle life, low reversible capacity, and high irreversible capacity due to mechanical degradation and inadequate protective coatings.
Innovation Solution
The development of multi-functional composite particulates with a polymer electrolyte matrix containing a lithium salt and encapsulated anode active material particles, which are further coated with a conducting shell to enhance lithium ion conductivity and mechanical toughness, allowing for volume expansion without shell breakage and reducing SEI formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode active materials (such as Li-Si alloys) are used to increase reversible capacity, then the specific capacity is improved, but severe pulverization occurs during charge and discharge cycles due to expansion and contraction, leading to shortened cycle life
Solution Approach 1:
The patent applies nested structure by placing anode active material particles inside a protective coating shell, which is in turn embedded in a polymer electrolyte matrix. This multi-layer nested structure protects the core active material from mechanical degradation while maintaining high capacity, directly resolving the contradiction between high reversible capacity and cycle life.
Solution Approach 2:
The patent creates a composite material system consisting of anode active material particles coated with protective material and embedded in polymer electrolyte matrix. This composite structure combines the high capacity of Li-Si alloys with the mechanical stability of the polymer electrolyte, preventing pulverization while maintaining high reversible capacity.
2Reliability
If the anode active material particles are coated with a protective shell to prevent pulverization, then cycle life is improved, but the coating may break during severe expansion, leading to shell breakage and loss of protection
Solution Approach 1:
The patent replaces rigid protective coatings with a flexible polymer electrolyte matrix that can accommodate the expansion and contraction of anode active material particles during charge and discharge cycles. This flexible matrix maintains shell integrity even during severe expansion, preventing breakage while protecting against pulverization.
Solution Approach 2:
The patent changes the mechanical properties of the protective layer by using a polymer electrolyte matrix with appropriate elasticity and flexibility parameters. This allows the protective structure to dynamically adapt to volume changes of the active material, maintaining integrity under severe expansion conditions while preventing particle degradation.
3Strength
If a protective coating is applied to anode active material particles, then mechanical degradation is reduced, but SEI formation increases leading to higher irreversible capacity loss
Solution Approach 1:
The patent introduces a polymer electrolyte matrix as an intermediary between the anode active material particles and the liquid electrolyte. This intermediary layer provides mechanical stability to prevent particle degradation while being electrochemically stable to minimize SEI formation, thus reducing irreversible capacity loss compared to traditional protective coatings.
4Stability of the object's composition
If conventional binders are used to bond anode active material particles, then structural integrity is achieved, but lithium ion conductivity and mechanical toughness are insufficient
Solution Approach 1:
The patent fundamentally changes the properties of the binder material by using a polymer electrolyte matrix that simultaneously provides structural integrity, lithium ion conductivity, and mechanical toughness. This polymer electrolyte maintains a stable composition while enabling efficient lithium ion transport, overcoming the limitations of conventional binders that lack ionic conductivity.
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 solution significantly increases the cycle life and reversible capacity of lithium-ion batteries by preventing shell breakage and minimizing SEI formation, resulting in stable charge/discharge cycles and improved high-rate capacity.
Implementation Method 1
severe expansion and contraction of the anode active material particles induced by the insertion and extraction of the lithium ions in and out of these particles
Implementation Method 2
encapsulated by, embedded in, dispersed in, or bonded by the polymer electrolyte having a lithium ion conductivity from 10−8 to 5×10−2 S/cm
Implementation Method 3
The lithium in this reaction comes from some of the lithium ions originally intended for the purpose of the charge transfer between an anode and a cathode. As the SEI is formed, the lithium ions become part of the inert SEI layer and become irreversible
Implementation Method 4
encapsulated by, embedded in, dispersed in, or bonded by the polymer electrolyte having a lithium ion conductivity from 10−8 to 5×10−2 S/cm
Data Source
AI summary
The disclosure provides multi-functional composite particulates for a lithium battery, wherein at least one of the composite particulates has a diameter from 100 nm to 50 μm and comprises a polymer electrolyte matrix comprising a lithium salt dissolved or dispersed in the polymer electrolyte matrix and one or a plurality of primary particles of an anode active material that are encapsulated by, embedded in, dispersed in, or bonded by the polymer electrolyte having a lithium ion conductivity from 10−8 to 5×10−2 S/cm, wherein the primary particles have a diameter or thickness from 0.5 nm to 20 μm and occupy a weight fraction from 5% to 98% based on the total weight of the composite particulate. Also provided is a method of producing such composite particulates, an anode electrode comprising these particulates, and a lithium cell.