MnO2 Lithium Secondary Battery Electrolyte for Deep-Cycle Capacity
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Solution Overview
Problem
Existing lithium secondary batteries using MnO2 as the positive electrode active material face challenges in achieving high capacity density and reversible cycle characteristics, especially when charged and discharged at a deep depth, due to limitations in electrolytic solvents and negative electrode materials.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with MnO2, a negative electrode with occluded lithium ions, and an electrolytic solution composed of a mixed solvent of cyclic and chain carbonates, allowing high charge voltage and improved cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic solvents are used in MnO2-based lithium secondary batteries, then the battery structure is simple, but the capacity density is low and cycle characteristics deteriorate at deep discharge levels
Solution Approach 1:
The patent applies composite materials by combining multiple electrolytic solvents (cyclic carbonate and chain carbonate) to create a mixed solvent system. This composite electrolytic solution achieves both high capacity density and favorable cycle characteristics at deep discharge levels, resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent changes the parameters of the electrolytic solution by specifying precise compositional ratios (cyclic carbonate 20-40 vol%, chain carbonate 60-80 vol%) and controlling water content (5-50 ppm). These parameter changes enable the electrolytic solution to support high charge voltages while maintaining stable cycle characteristics at deep discharge levels.
2Quantity of substance
If high charge voltage is applied to MnO2 positive electrode, then capacity density increases, but cycle characteristics worsen at deep discharge levels
Solution Approach 1:
The patent uses a composite electrolytic solution combining cyclic carbonate and chain carbonate in specific ratios. This composite system enables the battery to achieve high capacity density at 4.2V charge voltage while maintaining favorable cycle characteristics even at 80% depth of discharge, resolving the contradiction between quantity of substance and reliability.
Solution Approach 2:
The patent changes the electrolytic solution parameters by controlling the ratio of cyclic to chain carbonate and limiting water content to 5-50 ppm. These parameter changes allow the system to stabilize the electrode interface at high charge voltages, enabling both high capacity density and reliable cycle performance at deep discharge levels.
3Reliability
If cobalt-containing composite oxide is used as positive electrode active material, then electrochemical performance is high, but material availability is limited due to cobalt depletion
Solution Approach 1:
The patent replaces expensive and scarce cobalt-containing composite oxides with manganese dioxide, which is abundant and inexpensive. The developed electrolytic solution system enables MnO2 to achieve electrochemical performance comparable to cobalt-based materials, substituting a rare material with a readily available alternative.
Solution Approach 2:
The patent changes the chemical composition of the positive electrode active material from cobalt-containing composite oxide to manganese dioxide. By optimizing the electrolytic solution parameters (cyclic/chain carbonate ratio, water content control), the system compensates for the lower intrinsic performance of MnO2, achieving comparable electrochemical performance with abundant material.
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 battery achieves enhanced capacity density and favorable cycle characteristics even at deep discharge levels, utilizing the high withstand voltage of the mixed solvent and the reversibility of the occluded lithium ions.
Implementation Method 1
an electrolytic solution including a mixed solvent of a cyclic carbonate and a chain carbonate, the electrolytic solution being impregnated into the positive electrode and the negative electrode
Implementation Method 2
a negative electrode including a negative electrode active material with lithium ions occluded
Data Source
AI summary
A lithium secondary battery 100 of the present disclosure includes: a positive electrode 5 including MnO2; a negative electrode 6 including a negative electrode active material with lithium ions occluded; and an electrolytic solution including a mixed solvent of a cyclic carbonate and a chain carbonate, the electrolytic solution being impregnated into the positive electrode 5 and the negative electrode 6. The negative electrode active material includes, for example, at least one selected from the group consisting of graphite and silicon. The cyclic carbonate includes, for example, at least one selected from the group consisting of ethylene carbonate and vinylene carbonate. The chain carbonate includes, for example, ethyl methyl carbonate.