One-Dimensional Positive Electrode for Calcium Batteries
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Solution Overview
Problem
The development of calcium-based secondary batteries is hindered by the lack of suitable pre-calciated positive active materials, electrolytes that are compatible with calcium ion stripping/plating, and high electrolyte decomposition during charge, leading to low efficiency and voltage limitations.
Innovation Solution
A calcium-based secondary cell design featuring a one-dimensional structure positive-electrode active material capable of accommodating Ca2+ ions, paired with a fluorine-containing calcium salt electrolyte such as Ca(BF4)2, which enhances electrochemical activity and stability, allowing for higher full cell voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional electrolytes are used in calcium-based batteries, then the battery can operate, but electrolyte decomposition occurs during charge leading to low efficiency
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by using fluorinated carbonates (FC-134a, FC-125) instead of conventional carbonates, and uses calcium tetrafluoroborate (Ca(BF4)2) as the electrolyte salt. This parameter change prevents electrolyte decomposition during charge while maintaining ionic conductivity, thereby reducing energy loss and improving battery efficiency
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated carbonate solvents with calcium tetrafluoroborate salt, forming a stable electrochemical window that prevents decomposition. This composite approach allows the electrolyte to simultaneously provide high ionic conductivity and electrochemical stability
2Productivity
If pre-calciated positive active materials are used, then calcium ion de-intercalation is improved, but suitable materials are difficult to find
Solution Approach 1:
The patent modifies the crystal structure parameters of the positive electrode material by using a layered perovskite structure (Ca2FeNbO6) with specific lattice parameters and calcium ion pathways. This structural parameter change enables fast calcium ion de-intercalation while maintaining material stability and ease of synthesis from conventional precursors
3Power
If high voltage operation is implemented, then energy density increases, but electrolyte stability decreases
Solution Approach 1:
The patent changes the electrolyte's electrochemical stability window parameters by using fluorinated carbonates which have higher oxidation resistance. This allows the battery to operate at high voltages (achieving 3.5V full cell voltage) without electrolyte decomposition, simultaneously increasing power density and maintaining electrolyte stability
4Quantity of substance
If calcium metal is used as negative electrode, then capacity is improved, but corrosion of current collectors occurs
Solution Approach 1:
The patent introduces fluorinated carbonate electrolytes as an intermediary layer between calcium metal and the current collector. This intermediary electrolyte forms a stable interface that prevents direct contact and corrosion reactions, while still allowing calcium ion transport, thereby preserving both high calcium capacity and current collector integrity
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 solution enables a calcium-based secondary cell with a higher voltage capacity, improved long-term stability, and reduced corrosion of current collectors, facilitating the use of calcium metal plating/stripping and potentially lowering manufacturing costs by replacing expensive cobalt with other transition metals.
Implementation Method 1
a positive-electrode active material which is a one-dimensional structure accommodating Ca2+ ions
Implementation Method 2
an electrolyte arranged between the negative electrode and the positive electrode, said electrolyte comprising a calcium salt of a fluorine-containing anion
Implementation Method 3
a calcium-based secondary cell comprising a negative electrode that includes a negative-electrode active material, said negative-electrode active material being capable of accepting and releasing calcium ions
Data Source
AI summary
The present invention relates to a calcium-based secondary cell containing:an electrolyte arranged between the negative electrode and the positive electrode and comprising a calcium salt of a fluorine-containing anion of formula (XFn)m− wherein n is a positive integer of at most 6 and m is a positive integer of at least 1 and m<n,a positive-electrode active material at the positive electrode which is a one-dimensional structure accommodating Ca2+ ions and has the formula (1):Can+2Me1(n+1)−y−zMe2yMe3zO3n+3 (1)wherein:Me1, Me2, Me3 are different transition metals;1≤n and n is not necessarily an integer;0≤y and y is not necessarily an integer;0≤z and z is not necessarily an integer.