Polymer-Encapsulated Selenium Cathodes for Stable Li-Se Cycling
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Solution Overview
Problem
Rechargeable lithium-selenium (Li—Se) cells face issues such as dendrite formation, capacity decay due to selenium dissolution and migration, low active material utilization, and short cycle life, which hinder their widespread commercialization.
Innovation Solution
A cathode active material layer in Li—Se batteries is encapsulated by a protecting polymer layer, enhancing ion conductivity and preventing direct contact with liquid electrolyte, thereby reducing selenium dissolution and migration, and improving cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal anode is used in Li-Se batteries, then high specific capacity (3,861 mAh/g) is achieved, but dendrite formation occurs causing internal shorting and safety issues
Solution Approach 1:
A protective coating layer comprising silicon oxide and aluminum oxide is applied to the lithium metal anode. This intermediary layer prevents direct contact between lithium metal and the electrolyte/separator, blocking dendrite penetration while allowing ion transport, thus maintaining high capacity while improving safety
2Reliability
If conventional cathode materials (lithium transition-metal oxide or phosphate) are used in Li-ion batteries, then stable cycling is achieved, but specific energy is limited to 120-240 Wh/kg
Solution Approach 1:
The cathode material is changed from conventional lithium transition-metal oxide or phosphate to lithium selenide (Li2Se), which has higher theoretical capacity. The protective coating on the anode and optimized electrolyte composition enable this high-energy material to cycle stably, achieving specific energy >300 Wh/kg while maintaining cycle stability
3Use of energy by moving object
If selenium is used as cathode active material, then high specific energy is achieved, but selenium dissolution and migration cause capacity decay
Solution Approach 1:
A protective coating layer comprising silicon oxide and aluminum oxide is applied to prevent selenium dissolution into the electrolyte. The coating acts as a barrier that retains selenium on the anode surface while allowing ion transport, eliminating capacity decay from selenium loss
4Reliability
If separator is used to prevent internal shorting, then safety is improved, but separator pores can be clogged by precipitated solid products
Solution Approach 1:
The protective coating on the lithium metal anode prevents dendrite formation and blocks the migration of precipitated solid products to the separator. This intermediary barrier maintains separator pore openness while preserving safety functions
Solution Approach 2:
The protective coating is applied beforehand to prevent dendrite growth and precipitate formation before they can reach and clog the separator, maintaining ion transport efficiency throughout battery operation
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 polymer-encapsulated cathode active material layer achieves high specific energy, exceeding 300 Wh/kg, with improved cycle stability and reduced capacity decay, addressing key Li—Se cell limitations.
Implementation Method 1
A cathode active material layer in Li—Se batteries is encapsulated by a protecting polymer layer, enhancing ion conductivity and preventing direct contact with liquid electrolyte, thereby reducing selenium dissolution and migration
Implementation Method 2
A cathode active material layer in Li—Se batteries is encapsulated by a protecting polymer layer, enhancing ion conductivity
Implementation Method 3
When the battery was discharged, lithium ions were transferred from the lithium metal anode through the electrolyte to the cathode
Implementation Method 4
The carbonaceous material absorbs lithium (through intercalation of lithium ions or atoms between graphene planes, for instance)
Data Source
AI summary
Provided is particulate for use in a lithium-selenium battery cathode, the particulate comprising one or a plurality of cathode active material particles (selected from Se, lithium polyselenide, sodium polyselenide, potassium polyselenide, a Se alloy or mixture with Sn, Sb, Bi, S, or Te, or a combination thereof) being embraced or encapsulated by a thin layer of a protecting polymer having a lithium ion conductivity from 10−8 S/cm to 5×10−2 S/cm and a thickness from 0.5 nm to 10 μm, wherein the protecting polymer layer contains a polymer selected from poly(ethylene oxide) (PEO), polypropylene oxide (PPO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVDF), poly bis-methoxy ethoxyethoxide-phosphazene, polyvinyl chloride, poly(vinylidene chloride), polydimethylsiloxane, poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polyethylene glycol (PEG), chemical derivatives of PEG, poly(ethylene glycol diacrylate) (PEGDA), polyethylene glycol methyl ether (PEG-me), polyethylene glycol dimethyl ether (PEG-de), sulfonated polymers, interpenetrating polymer networks thereof, and combinations thereof.