Two-Stage Charging for Non-Aqueous Electrolyte Battery
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Solution Overview
Problem
Existing methods for producing non-aqueous electrolyte secondary batteries with multiple additives result in non-uniform electrode reactions and increased internal resistance over time, especially when using additives with different reaction potentials.
Innovation Solution
A two-stage charging method is employed, where the first stage maintains the battery voltage at the negative electrode potential for decomposing the additive with the noblest reduction potential, and the second stage maintains the voltage at which the non-aqueous solvent is reduced, ensuring the negative electrode potential is at least 0.7 V relative to lithium, promoting uniform SEI film formation and reducing gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple additives are present in the electrolyte with different reduction potentials, then the battery can achieve improved performance characteristics, but the electrode reaction becomes non-uniform and internal resistance increases after long-term storage
Solution Approach 1:
The initial charging process is divided into two distinct stages: a first charging step at a potential where only the additive with the noblest reduction potential decomposes, and a second charging step at a higher potential where the non-aqueous solvent decomposes. This segmentation prevents simultaneous decomposition of multiple additives, ensuring uniform electrode reaction while still allowing multiple additives to be present in the electrolyte for improved battery performance.
2Reliability
If multiple additives are present in the electrolyte, then comprehensive performance improvement can be achieved, but internal resistance increases after long-term storage
Solution Approach 1:
The first charging step performs a preliminary action by selectively decomposing only the additive with the noblest reduction potential at a controlled potential before the solvent decomposition potential is reached. This preliminary SEI film formation prevents subsequent non-uniform reactions and internal resistance increase, allowing multiple additives to coexist in the electrolyte without harmful effects during long-term storage.
3Reliability
If charging is performed at potentials where multiple additives decompose simultaneously, then comprehensive SEI film formation can occur, but non-uniform electrode reaction and increased internal resistance result
Solution Approach 1:
The charging process applies different potentials at different stages: the first charging step uses a potential specifically tailored to decompose only the additive with the noblest reduction potential, while the second charging step uses a higher potential for solvent decomposition. This local quality control in potential application ensures that SEI film formation occurs uniformly without causing non-uniform electrode reactions.
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 leads to a uniform electrode reaction, inhibiting the increase in internal resistance and enhancing the durability and cycle performance of the battery, even after long-term storage.
Implementation Method 1
when charging and discharging of battery is repeated, a non-aqueous solvent in an electrolyte is decomposed by reacting electrochemically with a negative electrode active material
Implementation Method 2
decomposition products generated by the reaction are deposited as a SEI (Solid Electrolyte Interface) film on a surface of a negative electrode active material
Implementation Method 3
during the second charging step, the battery voltage is maintained at voltage at which the non-aqueous solvent is reduced and decomposed
Data Source
AI summary
A method for producing a non-aqueous electrolyte secondary battery including an electrolyte containing an electrolyte salt, a non-aqueous solvent capable of dissolving the electrolyte salt, and plural additives, wherein at least one of the additives has a reduction potential that is nobler than the reduction potential of the non-aqueous solvent. The method includes a first charging step for maintaining battery voltage at a negative electrode potential at which the additive having the noblest reduction potential of the additives is decomposed while the non-aqueous solvent and other additives are not reduced and decomposed and a second charging step for maintaining battery voltage so as to have reduction and decomposition of at least one of the non-aqueous solvents and bring the electrical potential of the negative electrode to at least 0.7 V relative to lithium. By having a uniform reaction in an electrode, a decrease in durability is suppressed.