NaCl Cathode Phase Transition for Reversible Sodium-Ion Storage
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Solution Overview
Problem
Conventional methods for inducing a structural phase change in alkali metal halide compounds like NaCl for sodium ion secondary batteries require high temperature and high pressure conditions, making them difficult to produce and risky, while also resulting in lower electrochemical characteristics compared to lithium ion batteries.
Innovation Solution
An electrochemical process involving pre-charge and pre-discharge steps is used to transform NaCl from its B1 phase to the B2 phase, enabling reversible Na ion intercalation/deintercalation and improving electrochemical characteristics without the need for high temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature and high pressure conditions are used to induce structural phase change in NaCl, then the phase change can be achieved, but the manufacturing complexity and safety risks increase significantly
Solution Approach 1:
The patent replaces the conventional mechanical/thermal method (high temperature and high pressure) with an electrochemical method to induce the B1 to B2 phase change in NaCl. This substitution eliminates the need for complex high-temperature and high-pressure production facilities, thereby resolving the contradiction between achieving phase change and reducing manufacturing complexity.
Solution Approach 2:
The patent changes the approach from controlling physical parameters (temperature and pressure) to controlling electrochemical parameters (voltage and charge/discharge cycles). By applying electrochemical potential, the NaCl undergoes phase change at ambient conditions, avoiding the need for extreme environmental control and simplifying the production process.
2Manufacturing precision
If high temperature and high pressure conditions are used to induce structural phase change in NaCl, then the phase change can be achieved, but safety risks increase due to extreme conditions
Solution Approach 1:
The patent substitutes the dangerous mechanical/thermal system with a safe electrochemical system. Instead of using high temperature and high pressure equipment that pose safety risks, the invention uses electrochemical cells operating at ambient conditions to achieve the same phase change, thereby eliminating the harmful factors associated with extreme conditions.
Solution Approach 2:
The patent converts the inherent electrochemical reactivity of NaCl, which was previously a challenge under extreme conditions, into a beneficial mechanism. By utilizing electrochemical charge and discharge processes, the NaCl naturally undergoes phase change through ion insertion/extraction, transforming what could be a harmful side reaction into the primary mechanism for achieving the desired B2 phase.
3Quantity of substance
If conventional alkali halide compounds are used as cathode materials, then the voltage range is limited to −2.71V vs. SHE, but the electrochemical characteristics remain lower compared to lithium ion batteries
Solution Approach 1:
The patent exploits the phase transition of NaCl from B1 to B2 structure as a key mechanism to improve electrochemical characteristics. The B2 phase, with its different crystal structure and electronic properties, enables better ion transport and electrochemical performance while maintaining the same voltage range constraint, thus resolving the contradiction between voltage limitation and electrochemical performance.
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 process results in a sodium ion secondary battery with enhanced capacity and cycle characteristics, achieving a discharge capacity of 250 mAhg−1 at 0.03 C-rate and 30% capacity retention after 20 cycles, with NaCl in the B2 phase maintaining 90% of its total content in the cathode active material.
Implementation Method 1
carrying out electrochemical charge/discharge of NaCl in B1 phase to thereby obtain NaCl in B2 phase
Implementation Method 2
enabling reversible Na ion intercalation/deintercalation
Data Source
AI summary
The present disclosure relates to a cathode active material for a secondary battery, a cathode for a secondary battery including the same, a secondary battery including the cathode for a secondary battery and manufacturing methods thereof. More particularly, it is possible to obtain a secondary battery having excellent electrochemical characteristics by electrochemically inducing a structural phase change in the cathode active material of a secondary battery including NaCl as a cathode active material.