Lithium Battery Anode Efficiency Mismatch for Low SOC Resistance
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Solution Overview
Problem
Lithium secondary batteries face reduced output at low state-of-charge (SOC) levels due to high resistance at the discharge end portion of the negative electrode, which is exacerbated by the higher initial charge/discharge efficiency of the negative electrode compared to the positive electrode.
Innovation Solution
A lithium secondary battery design featuring a positive electrode with Li(Ni a Co b Mn c )O2 or Li(Ni a Co b Al c )O2 as the active material and a negative electrode with a mixing ratio of graphite and Si/SiOx, where the initial charge/discharge efficiency of the negative electrode is intentionally lower than that of the positive electrode, typically in the range of 80% to 92%, to reduce resistance and improve output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the initial charge/discharge efficiency of the negative electrode is higher than that of the positive electrode, then the negative electrode can deliver high capacity, but the discharge end portion coincides with the discharge end portion of the positive electrode, causing increased resistance
Solution Approach 1:
The invention inverts the conventional relationship by making the initial charge/discharge efficiency of the negative electrode lower than that of the positive electrode. This inversion strategically positions the discharge end portions at different SOC levels, preventing coincidence with the high-resistance region of the positive electrode and reducing overall resistance.
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 intentional reduction in the initial charge/discharge efficiency of the negative electrode relative to the positive electrode reduces resistance at low SOC levels, enhancing the output characteristics of the battery by avoiding the high-resistance region of the positive electrode, thereby improving overall battery performance.
Implementation Method 1
Lithium secondary batteries produce electric energy through an oxidation-reduction reaction when lithium ions are intercalated/deintercalated into/from negative electrodes and positive electrodes
Implementation Method 2
in a state in which an organic electrolyte solution or a polymer electrolyte solution is filled between the negative electrodes and the positive electrodes
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a lithium secondary battery comprising an anode and a cathode, wherein the anode includes a first anode active material consisting of a carbon-based material and a second anode active material with an initial charging and discharging efficiency lower than that of the first anode active material, and the initial charging and discharging efficiency of the anode is lower than that of the cathode. The present invention provides a lithium secondary battery that can realize a high output by significantly decreasing the resistance at a state of charge (SOC) in a low region.