Cathode Sacrificial Salt Filling for Silicon-Anode Battery Life
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity and maintaining life characteristics when using silicon-based negative electrodes, as the initial efficiency of the positive electrode is reduced, leading to potential electrical short circuits and capacity degradation.
Innovation Solution
A method of preparing a positive electrode by forming a layer with a sacrificial salt additive that decomposes into lithium and gases during charge, allowing lithium to be charged into the negative electrode while removing gases through a gas supply process, thereby reducing initial efficiency without degrading capacity or life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive electrode with higher initial efficiency is used, then charge/discharge efficiency is improved, but negative electrode potential increases during discharge and shrinkage increases leading to electrical short circuit
Solution Approach 1:
The patent applies preliminary action by filling the positive electrode pores with a sacrificial salt solution before battery assembly. During initial charging, the sacrificial salt decomposes to generate lithium ions that are preferentially inserted into the negative electrode, pre-lithiating it to compensate for subsequent shrinkage and prevent electrical short circuits during normal operation
Solution Approach 2:
The sacrificial salt acts as an intermediary substance that mediates between the positive and negative electrodes. It decomposes to provide lithium ions that buffer the negative electrode potential changes, preventing direct harmful interactions between the high-efficiency positive electrode and the silicon-based negative electrode
2Quantity of substance
If silicon-based negative electrode is used to increase capacity, then energy density is improved, but initial efficiency of positive electrode is reduced leading to capacity degradation
Solution Approach 1:
The sacrificial salt provides preliminary lithium insertion into the silicon-based negative electrode during initial charging cycles. This pre-lithiation compensates for the lithium loss during subsequent cycles, maintaining the positive electrode's discharge capacity and extending battery life characteristics
Solution Approach 2:
The patent changes the chemical composition parameter of the positive electrode by incorporating sacrificial salt (lithium azide, lithium oxocarbon, lithium dicarboxylate, or lithium hydrazide) at concentrations of 0.1-10 wt%. This compositional change enables controlled decomposition to generate lithium ions that stabilize the battery's capacity characteristics
3Reliability
If sacrificial salt additive is added to positive electrode, then initial efficiency is reduced, but discharge capacity and capacity density are maintained
Solution Approach 1:
The sacrificial salt component is extracted from the main positive electrode active material and placed in the pores as a separate functional component. This allows it to perform its specific function of generating lithium ions during initial charging without directly participating in the main charge/discharge reactions, thus maintaining capacity density while adjusting initial efficiency
Solution Approach 2:
The sacrificial salt is localized within the pores of the positive electrode structure rather than being uniformly distributed. This local placement allows it to function specifically during initial charging cycles to modify initial efficiency, while the bulk positive electrode material maintains its high capacity and capacity density characteristics
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 approach enables a positive electrode with reduced initial efficiency that maintains discharge capacity and capacity density, enhancing the performance and life characteristics of lithium secondary batteries when used with silicon-based negative electrodes.
Implementation Method 1
the sacrificial salt additive decomposes into lithium and N 2, CO, or CO 2 during charge so that the lithium is charged into a negative electrode
Implementation Method 2
N 2, CO, or CO 2 are vaporized and removed through a gas supply process
Implementation Method 3
electrical energy is produced by oxidation and reduction reactions when the lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode
Implementation Method 4
electrical energy is produced by oxidation and reduction reactions when the lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode
Data Source
AI summary
The present invention relates to a method of preparing a positive electrode for a secondary battery, which includes preparing a positive electrode by forming a positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder on a positive electrode collector, impregnating the positive electrode in a sacrificial salt solution including a sacrificial salt additive, and, after the impregnating of the positive electrode in the sacrificial salt solution, drying the positive electrode to fill pores of the positive electrode active material layer with the sacrificial salt additive, and a positive electrode for a secondary battery prepared thereby.