Polymeric Phosphorus Esters as Battery Cathode Binders
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Solution Overview
Problem
Conventional polymer electrolytes in lithium batteries, such as poly(ethylene oxide) (PEO), suffer from temperature-dependent ionic conductivity and low stability under oxidizing conditions, limiting battery power and voltage operation.
Innovation Solution
The use of polymeric phosphorus esters (PPEs) as cathode binders, which provide ionic conductivity and stability at high voltages due to their non-crystalline structure and high oxidization resistance, allowing for a 5% increase in voltage and thus power and energy in lithium polymer batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PEO is used as polymer electrolyte, then ionic conductivity is achieved, but stability under oxidizing conditions deteriorates at voltages above 3.8 V
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer electrolyte by incorporating phosphorus esters with specific molecular structures (including aromatic rings and phosphorus-oxygen bonds) that inherently resist oxidation. This compositional parameter change enables stability at voltages above 3.8 V while maintaining ionic conductivity through the polymer matrix.
Solution Approach 2:
The patent creates a composite polymer electrolyte system combining PEO with phosphorus ester additives and metal salts. This composite material integrates the ionic conductivity of PEO with the oxidative stability of phosphorus esters, achieving both functions simultaneously in the battery electrolyte system.
2Power
If PEO is used as polymer electrolyte, then battery operation is enabled, but temperature-dependent ionic conductivity limits power output
Solution Approach 1:
The patent modifies the physical and chemical parameters of the polymer electrolyte by adding phosphorus esters that alter the glass transition temperature and crystalline structure of PEO. These parameter changes reduce the temperature sensitivity of ionic conductivity, enabling more stable power output across a wider temperature range.
3Power
If voltage is increased to improve power, then battery power increases, but oxidization stability deteriorates
Solution Approach 1:
The patent changes the electrochemical stability window parameters of the electrolyte by incorporating phosphorus esters that raise the oxidation potential. This parameter change allows the battery to operate at higher voltages (increasing power) without compromising long-term stability, as the phosphorus ester components resist degradation at elevated potentials.
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
PPEs enable lithium polymer batteries to operate stably at higher voltages, improving long-term stability and increasing battery power and energy by maintaining ionic conductivity across a wide temperature range without crystallization and resisting further oxidization.
Implementation Method 1
its ionic conductivity is highly temperature dependent
Implementation Method 2
PEO is stable only to about 3.8 V vs Li+/Li, as higher voltages present oxidizing conditions that render it unstable
Data Source
AI summary
A class of polymeric phosphorous esters can be used as binders for battery cathodes. Metal salts can be added to the polymers to provide ionic conductivity. The polymeric phosphorous esters can be formulated with other polymers either as mixtures or as copolymers to provide additional desirable properties. Examples of such properties include even higher ionic conductivity and improved mechanical properties. Furthermore, cathodes that include the polymeric phosphorous esters can be assembled with a polymeric electrolyte separator and an anode to form a complete battery.